draft-ietf-hip-base-01.txt   draft-ietf-hip-base-02.txt 
Network Working Group R. Moskowitz Network Working Group R. Moskowitz
Internet-Draft ICSAlabs, a Division of TruSecure Internet-Draft ICSAlabs, a Division of TruSecure
Expires: April 25, 2005 Corporation Expires: August 25, 2005 Corporation
P. Nikander P. Nikander
P. Jokela (editor) P. Jokela (editor)
Ericsson Research NomadicLab Ericsson Research NomadicLab
T. Henderson T. Henderson
The Boeing Company The Boeing Company
October 25, 2004 February 21, 2005
Host Identity Protocol Host Identity Protocol
draft-ietf-hip-base-01 draft-ietf-hip-base-02
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable This document is an Internet-Draft and is subject to all provisions
patent or other IPR claims of which I am aware have been disclosed, of Section 3 of RFC 3667. By submitting this Internet-Draft, each
and any of which I become aware will be disclosed, in accordance with author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2005).
Abstract Abstract
This memo specifies the details of the Host Identity Protocol (HIP). This memo specifies the details of the Host Identity Protocol (HIP).
The overall description of protocol and the underlying architectural The overall description of protocol and the underlying architectural
thinking is available in the separate HIP architecture specification. thinking is available in the separate HIP architecture specification.
The Host Identity Protocol is used to establish a rapid The Host Identity Protocol is used to establish a rapid
authentication between two hosts and to provide continuity of authentication between two hosts and to provide continuity of
communications between those hosts independent of the networking communications between those hosts independent of the networking
layer. layer.
The various forms of the Host Identity, Host Identity Tag (HIT) and The various forms of the Host Identity, Host Identity Tag (HIT) and
Local Scope Identifier (LSI), are covered in detail. It is described Local Scope Identifier (LSI), are covered in detail. It is described
how they are used to support authentication and the establishment of how they are used to support authentication and the establishment of
skipping to change at page 2, line 10 skipping to change at page 2, line 15
The overall description of protocol and the underlying architectural The overall description of protocol and the underlying architectural
thinking is available in the separate HIP architecture specification. thinking is available in the separate HIP architecture specification.
The Host Identity Protocol is used to establish a rapid The Host Identity Protocol is used to establish a rapid
authentication between two hosts and to provide continuity of authentication between two hosts and to provide continuity of
communications between those hosts independent of the networking communications between those hosts independent of the networking
layer. layer.
The various forms of the Host Identity, Host Identity Tag (HIT) and The various forms of the Host Identity, Host Identity Tag (HIT) and
Local Scope Identifier (LSI), are covered in detail. It is described Local Scope Identifier (LSI), are covered in detail. It is described
how they are used to support authentication and the establishment of how they are used to support authentication and the establishment of
keying material, which is then used by IPsec Encapsulated Security keying material, which is then used for protecting subsequent HIP
payload (ESP) to establish a two-way secured communication channel messages, and which can be used for generating session keys for other
between the hosts. The basic state machine for HIP provides a HIP security protocols, such as IPsec Encapsulaed Security Payload (ESP).
compliant host with the resiliency to avoid many denial-of-service The basic state machine for HIP provides a HIP compliant host with
(DoS)attacks. The basic HIP exchange for two public hosts shows the the resiliency to avoid many denial-of-service (DoS) attacks. The
actual packet flow. Other HIP exchanges, including those that work basic HIP exchange for two public hosts shows the actual packet flow.
across NATs are covered elsewhere. Other HIP exchanges, including those that work across NATs, are
covered elsewhere.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 A new name space and identifiers . . . . . . . . . . . . . 5 1.1 A new name space and identifiers . . . . . . . . . . . . . 6
1.2 The HIP protocol . . . . . . . . . . . . . . . . . . . . . 5 1.2 The HIP base exchange . . . . . . . . . . . . . . . . . . 6
2. Conventions used in this document . . . . . . . . . . . . . 7 2. Conventions used in this document . . . . . . . . . . . . . 8
3. Host Identifier (HI) and its representations . . . . . . . . 8 3. Host Identifier (HI) and its representations . . . . . . . . 9
3.1 Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . 8 3.1 Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . 9
3.1.1 Generating a HIT from a HI . . . . . . . . . . . . . . 9 3.1.1 Restricting HIT values . . . . . . . . . . . . . . . . 10
3.2 Local Scope Identifier (LSI) . . . . . . . . . . . . . . . 11 3.1.2 Generating a HIT from a HI . . . . . . . . . . . . . . 11
3.3 Security Parameter Index (SPI) . . . . . . . . . . . . . . 11 3.2 Local Scope Identifier (LSI) . . . . . . . . . . . . . . . 12
4. Host Identity Protocol . . . . . . . . . . . . . . . . . . . 13 4. Host Identity Protocol . . . . . . . . . . . . . . . . . . . 14
4.1 HIP base exchange . . . . . . . . . . . . . . . . . . . . 13 4.1 HIP base exchange . . . . . . . . . . . . . . . . . . . . 14
4.1.1 HIP Cookie Mechanism . . . . . . . . . . . . . . . . . 14 4.1.1 HIP Cookie Mechanism . . . . . . . . . . . . . . . . . 15
4.1.2 Authenticated Diffie-Hellman protocol . . . . . . . . 17 4.1.2 Authenticated Diffie-Hellman protocol . . . . . . . . 18
4.1.3 HIP replay protection . . . . . . . . . . . . . . . . 18 4.1.3 HIP replay protection . . . . . . . . . . . . . . . . 19
4.2 TCP and UDP pseudo-header computation . . . . . . . . . . 19 4.2 TCP and UDP pseudo-header computation for user data . . . 20
4.3 Updating a HIP association . . . . . . . . . . . . . . . . 19 4.3 Updating a HIP association . . . . . . . . . . . . . . . . 20
4.4 Error processing . . . . . . . . . . . . . . . . . . . . . 19 4.4 Error processing . . . . . . . . . . . . . . . . . . . . . 20
4.5 Certificate distribution . . . . . . . . . . . . . . . . . 19 4.5 Certificate distribution . . . . . . . . . . . . . . . . . 21
4.6 Sending data on HIP packets . . . . . . . . . . . . . . . 20 4.6 Sending data on HIP packets . . . . . . . . . . . . . . . 21
5. HIP protocol overview . . . . . . . . . . . . . . . . . . . 21 4.7 Transport Formats . . . . . . . . . . . . . . . . . . . . 21
5.1 HIP Scenarios . . . . . . . . . . . . . . . . . . . . . . 21 5. HIP protocol overview . . . . . . . . . . . . . . . . . . . 22
5.2 Refusing a HIP exchange . . . . . . . . . . . . . . . . . 22 5.1 HIP Scenarios . . . . . . . . . . . . . . . . . . . . . . 22
5.3 Reboot and SA timeout restart of HIP . . . . . . . . . . . 22 5.2 Refusing a HIP exchange . . . . . . . . . . . . . . . . . 23
5.3 Reboot and SA timeout restart of HIP . . . . . . . . . . . 23
5.4 HIP State Machine . . . . . . . . . . . . . . . . . . . . 23 5.4 HIP State Machine . . . . . . . . . . . . . . . . . . . . 23
5.4.1 HIP States . . . . . . . . . . . . . . . . . . . . . . 23 5.4.1 HIP States . . . . . . . . . . . . . . . . . . . . . . 24
5.4.2 HIP State Processes . . . . . . . . . . . . . . . . . 23 5.4.2 HIP State Processes . . . . . . . . . . . . . . . . . 24
5.4.3 Simplified HIP State Diagram . . . . . . . . . . . . . 27 5.4.3 Simplified HIP State Diagram . . . . . . . . . . . . . 28
6. Packet formats . . . . . . . . . . . . . . . . . . . . . . . 29 6. Packet formats . . . . . . . . . . . . . . . . . . . . . . . 30
6.1 Payload format . . . . . . . . . . . . . . . . . . . . . . 29 6.1 Payload format . . . . . . . . . . . . . . . . . . . . . . 30
6.1.1 HIP Controls . . . . . . . . . . . . . . . . . . . . . 30 6.1.1 HIP Controls . . . . . . . . . . . . . . . . . . . . . 31
6.1.2 Checksum . . . . . . . . . . . . . . . . . . . . . . . 30 6.1.2 Checksum . . . . . . . . . . . . . . . . . . . . . . . 31
6.2 HIP parameters . . . . . . . . . . . . . . . . . . . . . . 31 6.2 HIP parameters . . . . . . . . . . . . . . . . . . . . . . 32
6.2.1 TLV format . . . . . . . . . . . . . . . . . . . . . . 32 6.2.1 TLV format . . . . . . . . . . . . . . . . . . . . . . 33
6.2.2 Defining new parameters . . . . . . . . . . . . . . . 33 6.2.2 Defining new parameters . . . . . . . . . . . . . . . 35
6.2.3 SPI . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.2.3 R1_COUNTER . . . . . . . . . . . . . . . . . . . . . . 36
6.2.4 R1_COUNTER . . . . . . . . . . . . . . . . . . . . . . 35 6.2.4 PUZZLE . . . . . . . . . . . . . . . . . . . . . . . . 37
6.2.5 PUZZLE . . . . . . . . . . . . . . . . . . . . . . . . 36 6.2.5 SOLUTION . . . . . . . . . . . . . . . . . . . . . . . 38
6.2.6 SOLUTION . . . . . . . . . . . . . . . . . . . . . . . 37 6.2.6 DIFFIE_HELLMAN . . . . . . . . . . . . . . . . . . . . 39
6.2.7 DIFFIE_HELLMAN . . . . . . . . . . . . . . . . . . . . 38 6.2.7 HIP_TRANSFORM . . . . . . . . . . . . . . . . . . . . 40
6.2.8 HIP_TRANSFORM . . . . . . . . . . . . . . . . . . . . 39 6.2.8 HOST_ID . . . . . . . . . . . . . . . . . . . . . . . 41
6.2.9 ESP_TRANSFORM . . . . . . . . . . . . . . . . . . . . 39 6.2.9 CERT . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.2.10 HOST_ID . . . . . . . . . . . . . . . . . . . . . . 40 6.2.10 HMAC . . . . . . . . . . . . . . . . . . . . . . . . 43
6.2.11 CERT . . . . . . . . . . . . . . . . . . . . . . . . 41 6.2.11 HMAC_2 . . . . . . . . . . . . . . . . . . . . . . . 43
6.2.12 HMAC . . . . . . . . . . . . . . . . . . . . . . . . 42 6.2.12 HIP_SIGNATURE . . . . . . . . . . . . . . . . . . . 44
6.2.13 HMAC_2 . . . . . . . . . . . . . . . . . . . . . . . 42 6.2.13 HIP_SIGNATURE_2 . . . . . . . . . . . . . . . . . . 44
6.2.14 HIP_SIGNATURE . . . . . . . . . . . . . . . . . . . 43 6.2.14 SEQ . . . . . . . . . . . . . . . . . . . . . . . . 45
6.2.15 HIP_SIGNATURE_2 . . . . . . . . . . . . . . . . . . 44 6.2.15 ACK . . . . . . . . . . . . . . . . . . . . . . . . 45
6.2.16 NES . . . . . . . . . . . . . . . . . . . . . . . . 44 6.2.16 ENCRYPTED . . . . . . . . . . . . . . . . . . . . . 46
6.2.17 SEQ . . . . . . . . . . . . . . . . . . . . . . . . 45 6.2.17 NOTIFY . . . . . . . . . . . . . . . . . . . . . . . 47
6.2.18 ACK . . . . . . . . . . . . . . . . . . . . . . . . 46 6.2.18 ECHO_REQUEST . . . . . . . . . . . . . . . . . . . . 50
6.2.19 ENCRYPTED . . . . . . . . . . . . . . . . . . . . . 47 6.2.19 ECHO_RESPONSE . . . . . . . . . . . . . . . . . . . 51
6.2.20 NOTIFY . . . . . . . . . . . . . . . . . . . . . . . 48 6.3 ICMP messages . . . . . . . . . . . . . . . . . . . . . . 51
6.2.21 ECHO_REQUEST . . . . . . . . . . . . . . . . . . . . 51 6.3.1 Invalid Version . . . . . . . . . . . . . . . . . . . 51
6.2.22 ECHO_RESPONSE . . . . . . . . . . . . . . . . . . . 52
6.3 ICMP messages . . . . . . . . . . . . . . . . . . . . . . 52
6.3.1 Invalid Version . . . . . . . . . . . . . . . . . . . 52
6.3.2 Other problems with the HIP header and packet 6.3.2 Other problems with the HIP header and packet
structure . . . . . . . . . . . . . . . . . . . . . . 53 structure . . . . . . . . . . . . . . . . . . . . . . 51
6.3.3 Unknown SPI . . . . . . . . . . . . . . . . . . . . . 53 6.3.3 Invalid Cookie Solution . . . . . . . . . . . . . . . 52
6.3.4 Invalid Cookie Solution . . . . . . . . . . . . . . . 53 6.3.4 Non-existing HIP association . . . . . . . . . . . . . 52
6.3.5 Non-existing HIP association . . . . . . . . . . . . . 53 7. HIP Packets . . . . . . . . . . . . . . . . . . . . . . . . 53
7. HIP Packets . . . . . . . . . . . . . . . . . . . . . . . . 54 7.1 I1 - the HIP initiator packet . . . . . . . . . . . . . . 53
7.1 I1 - the HIP initiator packet . . . . . . . . . . . . . . 54 7.2 R1 - the HIP responder packet . . . . . . . . . . . . . . 54
7.2 R1 - the HIP responder packet . . . . . . . . . . . . . . 55 7.3 I2 - the second HIP initiator packet . . . . . . . . . . . 55
7.3 I2 - the second HIP initiator packet . . . . . . . . . . . 56 7.4 R2 - the second HIP responder packet . . . . . . . . . . . 56
7.4 R2 - the second HIP responder packet . . . . . . . . . . . 58 7.5 CER - the HIP Certificate Packet . . . . . . . . . . . . . 57
7.5 CER - the HIP Certificate Packet . . . . . . . . . . . . . 58 7.6 UPDATE - the HIP Update Packet . . . . . . . . . . . . . . 57
7.6 UPDATE - the HIP Update Packet . . . . . . . . . . . . . . 59 7.7 NOTIFY - the HIP Notify Packet . . . . . . . . . . . . . . 58
7.7 NOTIFY - the HIP Notify Packet . . . . . . . . . . . . . . 60 7.8 CLOSE - the HIP association closing packet . . . . . . . . 59
7.8 CLOSE - the HIP association closing packet . . . . . . . . 60 7.9 CLOSE_ACK - the HIP closing acknowledgment packet . . . . 59
7.9 CLOSE_ACK - the HIP closing acknowledgment packet . . . . 61 8. Packet processing . . . . . . . . . . . . . . . . . . . . . 61
8. Packet processing . . . . . . . . . . . . . . . . . . . . . 62 8.1 Processing outgoing application data . . . . . . . . . . . 61
8.1 Processing outgoing application data . . . . . . . . . . . 62 8.2 Processing incoming application data . . . . . . . . . . . 62
8.2 Processing incoming application data . . . . . . . . . . . 63 8.3 HMAC and SIGNATURE calculation and verification . . . . . 63
8.3 HMAC and SIGNATURE calculation and verification . . . . . 64 8.3.1 HMAC calculation . . . . . . . . . . . . . . . . . . . 63
8.3.1 HMAC calculation . . . . . . . . . . . . . . . . . . . 64 8.3.2 Signature calculation . . . . . . . . . . . . . . . . 63
8.3.2 Signature calculation . . . . . . . . . . . . . . . . 64 8.4 Initiation of a HIP exchange . . . . . . . . . . . . . . . 64
8.4 Initiation of a HIP exchange . . . . . . . . . . . . . . . 65 8.4.1 Sending multiple I1s in parallel . . . . . . . . . . . 65
8.4.1 Sending multiple I1s in parallel . . . . . . . . . . . 66
8.4.2 Processing incoming ICMP Protocol Unreachable 8.4.2 Processing incoming ICMP Protocol Unreachable
messages . . . . . . . . . . . . . . . . . . . . . . . 66 messages . . . . . . . . . . . . . . . . . . . . . . . 65
8.5 Processing incoming I1 packets . . . . . . . . . . . . . . 67 8.5 Processing incoming I1 packets . . . . . . . . . . . . . . 66
8.5.1 R1 Management . . . . . . . . . . . . . . . . . . . . 67 8.5.1 R1 Management . . . . . . . . . . . . . . . . . . . . 66
8.5.2 Handling malformed messages . . . . . . . . . . . . . 68 8.5.2 Handling malformed messages . . . . . . . . . . . . . 67
8.6 Processing incoming R1 packets . . . . . . . . . . . . . . 68 8.6 Processing incoming R1 packets . . . . . . . . . . . . . . 67
8.6.1 Handling malformed messages . . . . . . . . . . . . . 70 8.6.1 Handling malformed messages . . . . . . . . . . . . . 68
8.7 Processing incoming I2 packets . . . . . . . . . . . . . . 70 8.7 Processing incoming I2 packets . . . . . . . . . . . . . . 69
8.7.1 Handling malformed messages . . . . . . . . . . . . . 71 8.7.1 Handling malformed messages . . . . . . . . . . . . . 70
8.8 Processing incoming R2 packets . . . . . . . . . . . . . . 72 8.8 Processing incoming R2 packets . . . . . . . . . . . . . . 70
8.9 Dropping HIP associations . . . . . . . . . . . . . . . . 72 8.9 Sending UPDATE packets . . . . . . . . . . . . . . . . . . 71
8.10 Initiating rekeying . . . . . . . . . . . . . . . . . . 72 8.10 Receiving UPDATE packets . . . . . . . . . . . . . . . . 71
8.11 Processing UPDATE packets . . . . . . . . . . . . . . . 74 8.10.1 Handling a SEQ paramaeter in a received UPDATE
8.11.1 Processing an UPDATE packet in state ESTABLISHED . . 75 message . . . . . . . . . . . . . . . . . . . . . . 72
8.11.2 Processing an UPDATE packet in state REKEYING . . . 75 8.10.2 Handling an ACK parameter in a received UPDATE
8.11.3 Leaving REKEYING state . . . . . . . . . . . . . . . 76 packet . . . . . . . . . . . . . . . . . . . . . . . 72
8.12 Processing CER packets . . . . . . . . . . . . . . . . . 76 8.11 Processing CER packets . . . . . . . . . . . . . . . . . 73
8.13 Processing NOTIFY packets . . . . . . . . . . . . . . . 76 8.12 Processing NOTIFY packets . . . . . . . . . . . . . . . 73
8.14 Processing CLOSE packets . . . . . . . . . . . . . . . . 77 8.13 Processing CLOSE packets . . . . . . . . . . . . . . . . 73
8.15 Processing CLOSE_ACK packets . . . . . . . . . . . . . . 77 8.14 Processing CLOSE_ACK packets . . . . . . . . . . . . . . 73
9. HIP KEYMAT . . . . . . . . . . . . . . . . . . . . . . . . . 78 8.15 Dropping HIP associations . . . . . . . . . . . . . . . 73
10. HIP Fragmentation Support . . . . . . . . . . . . . . . . . 80 9. HIP KEYMAT . . . . . . . . . . . . . . . . . . . . . . . . . 75
11. ESP with HIP . . . . . . . . . . . . . . . . . . . . . . . . 81 10. HIP Fragmentation Support . . . . . . . . . . . . . . . . . 77
11.1 ESP Security Associations . . . . . . . . . . . . . . . 81 11. HIP Policies . . . . . . . . . . . . . . . . . . . . . . . . 78
11.2 Updating ESP SAs during rekeying . . . . . . . . . . . . 81 12. Security Considerations . . . . . . . . . . . . . . . . . . 79
11.3 Security Association Management . . . . . . . . . . . . 82 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . 82
11.4 Security Parameter Index (SPI) . . . . . . . . . . . . . 82 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 83
11.5 Supported Transforms . . . . . . . . . . . . . . . . . . 82 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 84
11.6 Sequence Number . . . . . . . . . . . . . . . . . . . . 83 15.1 Normative references . . . . . . . . . . . . . . . . . . 84
12. HIP Policies . . . . . . . . . . . . . . . . . . . . . . . . 84 15.2 Informative references . . . . . . . . . . . . . . . . . 85
13. Security Considerations . . . . . . . . . . . . . . . . . . 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 86
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . 88 A. Probabilities of HIT collisions . . . . . . . . . . . . . . 87
15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 89 B. Probabilities in the cookie calculation . . . . . . . . . . 88
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 90 C. Using responder cookies . . . . . . . . . . . . . . . . . . 89
16.1 Normative references . . . . . . . . . . . . . . . . . . . 90 D. Example checksums for HIP packets . . . . . . . . . . . . . 92
16.2 Informative references . . . . . . . . . . . . . . . . . . 91 D.1 IPv6 HIP example (I1) . . . . . . . . . . . . . . . . . . 92
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 92 D.2 IPv4 HIP packet (I1) . . . . . . . . . . . . . . . . . . . 92
A. API issues . . . . . . . . . . . . . . . . . . . . . . . . . 93 D.3 TCP segment . . . . . . . . . . . . . . . . . . . . . . . 92
B. Probabilities of HIT collisions . . . . . . . . . . . . . . 95 E. 384-bit group . . . . . . . . . . . . . . . . . . . . . . . 94
C. Probabilities in the cookie calculation . . . . . . . . . . 96 Intellectual Property and Copyright Statements . . . . . . . 95
D. Using responder cookies . . . . . . . . . . . . . . . . . . 97
E. Running HIP over IPv4 UDP . . . . . . . . . . . . . . . . . 100
F. Example checksums for HIP packets . . . . . . . . . . . . . 101
F.1 IPv6 HIP example (I1) . . . . . . . . . . . . . . . . . . 101
F.2 IPv4 HIP packet (I1) . . . . . . . . . . . . . . . . . . . 101
F.3 TCP segment . . . . . . . . . . . . . . . . . . . . . . . 101
G. 384-bit group . . . . . . . . . . . . . . . . . . . . . . . 103
Intellectual Property and Copyright Statements . . . . . . . 104
1. Introduction 1. Introduction
The Host Identity Protocol (HIP) provides a rapid exchange of Host The Host Identity Protocol (HIP) provides a rapid exchange of Host
Identities between two hosts. The exchange also establishes a pair Identities between two hosts. The protocol is designed to be
IPsec Security Associations (SA), to be used with IPsec Encapsulated
Security Payload (ESP) [19]. The HIP protocol is designed to be
resistant to Denial-of-Service (DoS) and Man-in-the-middle (MitM) resistant to Denial-of-Service (DoS) and Man-in-the-middle (MitM)
attacks, and when used to enable ESP, provides DoS and MitM attacks, and when used together with another suitable security
protection for upper layer protocols, such as TCP and UDP. protocol, such as Encapsulated Security Payload (ESP) [23], it
provides DoS and MitM protection for upper layer protocols, such as
TCP and UDP.
1.1 A new name space and identifiers 1.1 A new name space and identifiers
The Host Identity Protocol introduces a new namespace, the Host The Host Identity Protocol introduces a new namespace, the Host
Identity. The effects of this change are explained in the companion Identity. The effects of this change are explained in the companion
document, the HIP architecture [21] specification. document, the HIP architecture [21] specification.
There are two main representations of the Host Identity, the full There are two main representations of the Host Identity, the full
Host Identifier (HI) and the Host Identity Tag (HIT). The HI is a Host Identifier (HI) and the Host Identity Tag (HIT). The HI is a
public key and directly represents the Identity. Since there are public key and directly represents the Identity. Since there are
different public key algorithms that can be used with different key different public key algorithms that can be used with different key
lengths, the HI is not good for using as a packet identifier, or as a lengths, the HI is not good for use as a packet identifier, or as an
index into the various operational tables needed to support HIP. index into the various operational tables needed to support HIP.
Consequently, a hash of the HI, the Host Identity Tag (HIT), becomes Consequently, a hash of the HI, the Host Identity Tag (HIT), becomes
the operational representation. It is 128 bits long and is used in the operational representation. It is 128 bits long and is used in
the HIP payloads and to index the corresponding state in the end the HIP payloads and to index the corresponding state in the end
hosts. hosts.
1.2 The HIP protocol 1.2 The HIP base exchange
The base HIP exchange consists of four packets. The four-packet The HIP base exchange is a two-party cryptographic protocol that
design helps to make HIP DoS resilient. The protocol exchanges consists of four packets. The first party is called the Initiator
Diffie-Hellman keys in the 2nd and 3rd packets, and authenticates the and the second party the Responder. The four-packet design helps to
parties in the 3rd and 4th packets. Additionally, it starts the make HIP DoS resilient. The protocol exchanges Diffie-Hellman keys
cookie exchange in the 2nd packet, completing it in the 3rd packet. in the 2nd and 3rd packets, and authenticates the parties in the 3rd
and 4th packets. Additionally, it starts the cookie exchange in the
2nd packet, completing it in the 3rd packet.
The exchange uses the Diffie-Hellman exchange to hide the Host The exchange uses the Diffie-Hellman exchange to hide the Host
Identity of the Initiator in packet 3. The Responder's Host Identity Identity of the Initiator in packet 3. The Responder's Host Identity
is not protected. It should be noted, however, that both the is not protected. It should be noted, however, that both the
Initiator's and the Responder's HITs are transported as such (in Initiator's and the Responder's HITs are transported as such (in
cleartext) in the packets, allowing an eavesdropper with a priori cleartext) in the packets, allowing an eavesdropper with a priori
knowledge about the parties to verify their identities. knowledge about the parties to verify their identities.
Data packets start after the 4th packet. The 3rd and 4th HIP packets Data packets start after the 4th packet. The 3rd and 4th HIP packets
may carry a data payload in the future. However, the details of this may carry a data payload in the future. However, the details of this
are to be defined later as more implementation experience is gained. are to be defined later as more implementation experience is gained.
Finally, HIP is designed as an end-to-end authentication and key Finally, HIP is designed as an end-to-end authentication and key
establishment protocol. It lacks much of the fine-grained policy establishment protocol, to be used with Encapsulated Security Payload
control found in Internet Key Exchange IKE RFC2409 [8] that allows (ESP) [23] and other end-to-end security protocols. The base
IKE to support complex gateway policies. Thus, HIP is not a complete protocol lacks the details for security association management and
replacement for IKE. much of the fine-grained policy control found in Internet Key
Exchange IKE RFC2409 [8] that allows IKE to support complex gateway
policies. Thus, HIP is not a replacement for IKE.
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [5]. document are to be interpreted as described in RFC2119 [5].
3. Host Identifier (HI) and its representations 3. Host Identifier (HI) and its representations
A public key of an asymmetric key pair is used as the Host Identifier A public key of an asymmetric key pair is used as the Host Identifier
(HI). Correspondingly, the host itself is the entity that holds the (HI). Correspondingly, the host itself is defined as the entity that
private key from the key pair. See the HIP architecture holds the private key from the key pair. See the HIP architecture
specification [21] for more details about the difference between an specification [21] for more details about the difference between an
identity and the corresponding identifier. identity and the corresponding identifier.
HIP implementations MUST support the Rivest Shamir Adelman (RSA) [14] HIP implementations MUST support the Rivest Shamir Adelman (RSA) [14]
public key algorithm, and SHOULD support the Digital Signature public key algorithm, and SHOULD support the Digital Signature
Algorithm (DSA) [13] algorithm; other algorithms MAY be supported. Algorithm (DSA) [13] algorithm; other algorithms MAY be supported.
A hash of the HI, the Host Identity Tag (HIT), is used in protocols A hash of the HI, the Host Identity Tag (HIT), is used in protocols
to represent the Host Identity. The HIT is 128 bits long and has the to represent the Host Identity. The HIT is 128 bits long and has the
following three key properties: i) it is the same length as an IPv6 following three key properties: i) it is the same length as an IPv6
skipping to change at page 8, line 32 skipping to change at page 9, line 32
computationally hard to find a Host Identity key that matches the computationally hard to find a Host Identity key that matches the
HIT), and iii) the probability of HIT collision between two hosts is HIT), and iii) the probability of HIT collision between two hosts is
very low. very low.
In many environments, 128 bits is still considered large. For In many environments, 128 bits is still considered large. For
example, currently used IPv4 based applications are constrained with example, currently used IPv4 based applications are constrained with
32-bit address fields. Another problem is that the cohabitation of 32-bit address fields. Another problem is that the cohabitation of
IPv6 and HIP might require some applications to differentiate an IPv6 IPv6 and HIP might require some applications to differentiate an IPv6
address from a HIT. Thus, a third representation, the Local Scope address from a HIT. Thus, a third representation, the Local Scope
Identifier (LSI), may be needed. There are two types of such LSIs: Identifier (LSI), may be needed. There are two types of such LSIs:
32 bits long IPv4-compatible one and 128 bits long IPv6-compatible 32-bit IPv4-compatible ones and 128-bit IPv6-compatible ones. The
one. The LSI provides a compression of the HIT with only a local LSI provides a compression of the HIT with only a local scope so that
scope so that it can be carried efficiently in any application level it can be carried efficiently in any application level packet and
packet and used in API calls. LSIs do not have the same properties used in API calls. The LSIs do not have the same properties as HITs
as HITs (i.e., they are not self-certifying nor are they as unlikely (i.e., they are not self-certifying nor are they as unlikely to
to collide -- hence their local scope), and consequently they must be collide -- hence their local scope), and consequently they must be
used more carefully. used more carefully.
Finally, HIs, HITs, and LSIs are not carried explicitly in the Finally, HIs, HITs, and LSIs are not expected to be carried
headers of user data packets. Instead, the IPsec Security Parameter explicitly in the headers of user data packets. Depending on the
Index (SPI) is used in data packets to index the right host context. form of further communication, other methods are used to map the data
The SPIs are selected during the HIP exchange. For user data packets, packet to the these representatives of host identities. For example,
then, the combination of IPsec SPIs and IP addresses are used if ESP is used to protect data traffic, the Security Parameter Index
indirectly to identify the host context, thereby avoiding an (SPI) can be used for this purpose. In some cases, this makes it
additional explicit protocol header. possible to use HIP without an additional explicit protocol header.
3.1 Host Identity Tag (HIT) 3.1 Host Identity Tag (HIT)
The Host Identity Tag is a 128 bit value -- a hash of the Host The Host Identity Tag is a 128 bits long value -- a hash of the Host
Identifier. There are two advantages of using a hash over the actual Identifier. There are two advantages of using a hash over the actual
Identity in protocols. Firstly, its fixed length makes for easier Identity in protocols. Firstly, its fixed length makes for easier
protocol coding and also better manages the packet size cost of this protocol coding and also better manages the packet size cost of this
technology. Secondly, it presents a consistent format to the technology. Secondly, it presents a consistent format to the
protocol whatever underlying identity technology is used. protocol whatever underlying identity technology is used.
There are two types of HITs. HITs of the first type, called *type 1 There are two types of HITs. HITs of the first type, called _type 1
HIT*, consist of 128 bits of the SHA-1 hash of the public key. HITs HIT_, consist of 128 bits of the SHA-1 hash of the public key. HITs
of the second type consist of a Host Assigning Authority Field (HAA), of the second type consist of a Host Assigning Authority Field (HAA),
and only the last 64 bits come from a SHA-1 hash of the Host and only the last 64 bits come from a SHA-1 hash of the Host
Identity. This latter format for HIT is recommended for 'well known' Identity. This latter format for HIT is recommended for 'well known'
systems. It is possible to support a resolution mechanism for these systems. It is possible to support a resolution mechanism for these
names in hierarchical directories, like the DNS. Another use of HAA names in hierarchical directories, like the DNS. Another use of HAA
is in policy controls, see Section 12. is in policy controls, see Section 11.
As the type of a HIT cannot be determined by inspecting its contents, As the type of a HIT cannot be determined by inspecting its contents,
the HIT type must be communicated by some external means. the HIT type must be communicated by some external means.
When comparing HITs for equality, it is RECOMMENDED that conforming When comparing HITs for equality, it is RECOMMENDED that conforming
implementations ignore the TBD top most bits. This is to allow implementations ignore the TBD top most bits. This is to allow
better compatibility for legacy IPv6 applications; see Appendix A. better compatibility for legacy IPv6 applications; see [29].
However, independent of how many bits are actually used for HIT However, independent of how many bits are actually used for HIT
comparison, it is also RECOMMENDED that the final equality decision comparison, it is also RECOMMENDED that the final equality decision
is based on the public key and not the HIT, if possible. See also is based on the public key and not the HIT, if possible. See also
Section 3.2 for related discussion. Section 3.2 for related discussion.
This document fully specifies only type 1 HITs. HITs that consists This document fully specifies only type 1 HITs. HITs that consists
of the HAA field and the hash are specified in [24]. of the HAA field and the hash are specified in [25].
Any conforming implementation MUST be able to deal with Type 1 HITs. Any conforming implementation MUST be able to deal with Type 1 HITs.
When handling other than type 1 HITs, the implementation is When handling other than type 1 HITs, the implementation is
RECOMMENDED to explicitly learn and record the binding between the RECOMMENDED to explicitly learn and record the binding between the
Host Identifier and the HIT, as it may not be able to generate such Host Identifier and the HIT, as it may not be able to generate such
HITs from the Host Identifiers. HITs from the Host Identifiers.
3.1.1 Generating a HIT from a HI 3.1.1 Restricting HIT values
To facilitate experimentation and make certain kind of
implementations easier, the following restrictions are temporarily
placed on HITs. These restriction are to be lifted at the end of
2008. That is, after January 1st 2009, any implementation claiming
conformance to this specification MUST accept any HITs from peers and
be able to process them normally.
The restrictions: Before the end of 2008, all implementations SHOULD
restrict the HITs they generate to ones whose upper-most (left-most)
two bits are either binary01 or10. That is, when generating new HIs,
if the resulting HIT has as its first two bits as00 or11, the
implementation SHOULD generate new HIs until it generates one that
fulfills this restriction. Additionally, a conforming implementation
MAY refuse to communicate with a peer that has a HIT with the
upper-most bits either00 or11. When refusing a HIP connection on
this bases, the implementation MAY send an R2 with a NOTIFY payload,
with the NOTIFY code being UNSUPPORTED_HIT_VALUE_RANGE. Any such
NOTIFYs may be rate-limited
A rationale: One way to experimentally implement HIP is to use
unmodified IPv6, TCP and UDP implementations in the stack, using HITs
in the place of IPv6 addresses. This modification makes it easier to
use existing IPv6 data structures to hold HITs and to distinguish
between the two data types. If the IPv6 address space and the HIT
value space overlap, it becomes hard to define secure IPsec policies
without explicitly tagging the values either as HITs or IPv6
addresses.
3.1.2 Generating a HIT from a HI
The 128 or 64 hash bits in a HIT MUST be generated by taking the The 128 or 64 hash bits in a HIT MUST be generated by taking the
least significant 128 or 64 bits of the SHA-1 [22] hash of the Host least significant 128 or 64 bits of the SHA-1 [22] hash of the Host
Identifier as it is represented in the Host Identity field in a HIP Identifier as it is represented in the Host Identity field in a HIP
payload packet. payload packet.
For Identities that are either RSA or DSA public keys, the HIT is For Identities that are either RSA or DSA public keys, the HIT is
formed as follows: formed as follows:
1. The public key is encoded as specified in the corresponding 1. The public key is encoded as specified in the corresponding
DNSSEC document, taking the algorithm specific portion of the DNSSEC document, taking the algorithm specific portion of the
skipping to change at page 10, line 4 skipping to change at page 11, line 33
Identifier as it is represented in the Host Identity field in a HIP Identifier as it is represented in the Host Identity field in a HIP
payload packet. payload packet.
For Identities that are either RSA or DSA public keys, the HIT is For Identities that are either RSA or DSA public keys, the HIT is
formed as follows: formed as follows:
1. The public key is encoded as specified in the corresponding 1. The public key is encoded as specified in the corresponding
DNSSEC document, taking the algorithm specific portion of the DNSSEC document, taking the algorithm specific portion of the
RDATA part of the KEY RR. There is currently only two defined RDATA part of the KEY RR. There is currently only two defined
public key algorithms: RSA and DSA. Hence, either of the public key algorithms: RSA and DSA. Hence, either of the
following applies: following applies:
The RSA public key is encoded as defined in RFC3110 [14] The RSA public key is encoded as defined in RFC3110 [14]
Section 2, taking the exponent length (e_len), exponent (e) Section 2, taking the exponent length (e_len), exponent (e)
and modulus (n) fields concatenated. The length of the and modulus (n) fields concatenated. The length (n_len) of
modulus (n) can be determined from the total HI length the modulus (n) can be determined from the total HI length
(hi_len) and the preceding HI fields including the exponent (hi_len) and the preceding HI fields including the exponent
(e). Thus, the data to be hashed has the same length than the (e). Thus, the data to be hashed has the same length as the
HI (hi_len). The fields MUST be encoded in network byte order, HI (hi_len). The fields MUST be encoded in network byte
as defined in RFC3110 [14]. order, as defined in RFC3110 [14].
The DSA public key is encoded as defined in RFC2536 [13] The DSA public key is encoded as defined in RFC2536 [13]
Section 2, taking the fields T, Q, P, G, and Y, concatenated. Section 2, taking the fields T, Q, P, G, and Y, concatenated.
Thus, the data to be hashed is 1 + 20 + 3 * 64 + 3 * 8 * T Thus, the data to be hashed is 1 + 20 + 3 * 64 + 3 * 8 * T
octets long, where T is the size parameter as defined in octets long, where T is the size parameter as defined in
RFC2536 [13]. The size parameter T, affecting the field RFC2536 [13]. The size parameter T, affecting the field
lengths, MUST be selected as the minimum value that is long lengths, MUST be selected as the minimum value that is long
enough to accommodate P, G, and Y. The fields MUST be encoded enough to accommodate P, G, and Y. The fields MUST be encoded
in network byte order, as defined in RFC2536 [13]. in network byte order, as defined in RFC2536 [13].
2. A SHA-1 hash [22] is calculated over the encoded key. 2. A SHA-1 hash [22] is calculated over the encoded key.
3. The least significant 128 or 64 bits of the hash result are used 3. The least significant 128 or 64 bits of the hash result are used
skipping to change at page 10, line 38 skipping to change at page 12, line 18
two parameters, an integer (bignum) and a length in bytes, and two parameters, an integer (bignum) and a length in bytes, and
returns the integer encoded into a byte string of the given length. returns the integer encoded into a byte string of the given length.
switch ( HI.algorithm ) switch ( HI.algorithm )
{ {
case RSA: case RSA:
buffer := encode_in_network_byte_order ( HI.RSA.e_len, buffer := encode_in_network_byte_order ( HI.RSA.e_len,
( HI.RSA.e_len > 255 ) ? 3 : 1 ) ( HI.RSA.e_len > 255 ) ? 3 : 1 )
buffer += encode_in_network_byte_order ( HI.RSA.e, HI.RSA.e_len ) buffer += encode_in_network_byte_order ( HI.RSA.e, HI.RSA.e_len )
buffer += encode_in_network_byte_order ( HI.RSA.n, HI.hi_len ) buffer += encode_in_network_byte_order ( HI.RSA.n, HI.RSA.n_len )
break; break;
case DSA: case DSA:
buffer := encode_in_network_byte_order ( HI.DSA.T , 1 ) buffer := encode_in_network_byte_order ( HI.DSA.T , 1 )
buffer += encode_in_network_byte_order ( HI.DSA.Q , 20 ) buffer += encode_in_network_byte_order ( HI.DSA.Q , 20 )
buffer += encode_in_network_byte_order ( HI.DSA.P , 64 + 8 * HI.DSA.T ) buffer += encode_in_network_byte_order ( HI.DSA.P , 64 + 8 * HI.DSA.T )
buffer += encode_in_network_byte_order ( HI.DSA.G , 64 + 8 * HI.DSA.T ) buffer += encode_in_network_byte_order ( HI.DSA.G , 64 + 8 * HI.DSA.T )
buffer += encode_in_network_byte_order ( HI.DSA.Y , 64 + 8 * HI.DSA.T ) buffer += encode_in_network_byte_order ( HI.DSA.Y , 64 + 8 * HI.DSA.T )
break; break;
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from the peer's HIT collides with another LSI in use locally (i.e., from the peer's HIT collides with another LSI in use locally (i.e.,
the lower 24 or TBD bits of two different HITs are the same). In the lower 24 or TBD bits of two different HITs are the same). In
that case, the host MUST handle the LSI collision locally such that that case, the host MUST handle the LSI collision locally such that
application calls can be disambiguated. One possible means of doing application calls can be disambiguated. One possible means of doing
so is to perform a Host NAT function to locally convert a peer's LSI so is to perform a Host NAT function to locally convert a peer's LSI
into a different LSI value. This would require the host to ensure into a different LSI value. This would require the host to ensure
that LSI bits on the wire (i.e., in the application data stream) are that LSI bits on the wire (i.e., in the application data stream) are
converted back to match that host's LSI. Other alternatives for converted back to match that host's LSI. Other alternatives for
resolving LSI collisions may be added in the future. resolving LSI collisions may be added in the future.
3.3 Security Parameter Index (SPI)
SPIs are used in ESP to find the right security association for
received packets. The ESP SPIs have added significance when used
with HIP; they are a compressed representation of the HITs in every
packet. Thus, SPIs MAY be used by intermediary systems in providing
services like address mapping. Note that since the SPI has
significance at the receiver, only the < DST, SPI >, where DST is a
destination IP address, uniquely identifies the receiver HIT at every
given point of time. The same SPI value may be used by several
hosts. A single < DST, SPI > value may denote different hosts at
different points of time, depending on which host is currently
reachable at the DST.
Each host selects for itself the SPI it wants to see in packets
received from its peer. This allows it to select different SPIs for
different peers. The SPI selection SHOULD be random; the rules of
Section 2.1 of the ESP specification [19] must be followed. A
different SPI SHOULD be used for each HIP exchange with a particular
host; this is to avoid a replay attack. Additionally, when a host
rekeys, the SPI MUST be changed. Furthermore, if a host changes over
to use a different IP address, it MAY change the SPI.
One method for SPI creation that meets these criteria would be to
concatenate the HIT with a 32-bit random or sequential number, hash
this (using SHA1), and then use the high order 32 bits as the SPI.
The selected SPI is communicated to the peer in the third (I2) and
fourth (R2) packets of the base HIP exchange. Changes in SPI are
signaled with NES parameters.
4. Host Identity Protocol 4. Host Identity Protocol
The Host Identity Protocol is IP protocol TBD (number will be The Host Identity Protocol is IP protocol TBD (number will be
assigned by IANA). The HIP payload could be carried in every assigned by IANA). The HIP payload (Section 6.1) header could be
datagram. However, since HIP datagrams are relatively large (at carried in every datagram. However, since HIP datagrams are
least 40 bytes), and ESP already has all of the functionality to relatively large (at least 40 bytes), it is desirable to 'compress'
maintain and protect state, the HIP payload is 'compressed' into an the HIP header so that the HIP header only occur in datagrams to
ESP payload after the HIP exchange. Thus in practice, HIP packets establish or change HIP state. The actual method for header
only occur in datagrams to establish or change HIP state. 'compression' and matching data packets with existing HIP
associations (if any) is defined in separate extension documents,
describing transport formats and methods. All HIP implementations
MUST implement, at minimum, the ESP transport format for HIP [23].
For testing purposes, the protocol number 99 is currently used. For testing purposes, the protocol number 99 is currently used.
4.1 HIP base exchange 4.1 HIP base exchange
The base HIP exchange serves to manage the establishment of state The HIP base exchange serves to manage the establishment of state
between an Initiator and a Responder. During the exchange, an IPsec between an Initiator and a Responder. The last three packets of the
Security Association is created between the hosts. The last three exchange, R1, I2, and R2, constitute a standard authenticated
packets of the exchange, R1, I2, and R2, constitute a standard Diffie-Hellman key exchange for session key generation. During the
authenticated Diffie-Hellman key exchange for session key generation. Diffie-Hellman key exchange, a piece of keying material is generated.
The HIP association keys are drawn from this keying material. If
other cryptographic keys are needed, e.g., to be used with ESP, they
are expected to be drawn from the same keying material.
The Initiator first sends a trigger packet, I1, to the Responder. The Initiator first sends a trigger packet, I1, to the Responder.
The packet contains only the HIT of the Initiator and possibly the The packet contains only the HIT of the Initiator and possibly the
HIT of the Responder, if it is known. HIT of the Responder, if it is known.
The second packet, R1, starts the actual exchange. It contains a The second packet, R1, starts the actual exchange. It contains a
puzzle, that is, a cryptographic challenge that the Initiator must puzzle, that is, a cryptographic challenge that the Initiator must
solve before continuing the exchange. In addition, it contains the solve before continuing the exchange. In addition, it contains the
initial Diffie-Hellman parameters and a signature, covering part of initial Diffie-Hellman parameters and a signature, covering part of
the message. Some fields are left outside the signature to support the message. Some fields are left outside the signature to support
pre-created R1s. pre-created R1s.
In the I2 packet, the Initiator must display the solution to the In the I2 packet, the Initiator must display the solution to the
received puzzle. Without a correct solution, the I2 message is received puzzle. Without a correct solution, the I2 message is
discarded. The I2 also contains a Diffie-Hellman parameter that discarded. The I2 also contains a Diffie-Hellman parameter that
carries needed information for the Responder. The packet is signed carries needed information for the Responder. The packet is signed
by the sender. by the sender.
The R2 packet finalizes the 4-way handshake, containing the SPI value The R2 packet finalizes the base exchange. The packet is signed.
of the Responder. The packet is signed.
The base exchange is illustrated below. During this D-H procedure, The base exchange is illustrated below.
the hosts create an IPsec session key.
Initiator Responder Initiator Responder
I1: trigger exchange I1: trigger exchange
--------------------------> -------------------------->
select pre-computed R1 select pre-computed R1
R1: puzzle, D-H, key, sig R1: puzzle, D-H, key, sig
<------------------------- <-------------------------
check sig remain stateless check sig remain stateless
solve puzzle solve puzzle
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The Cookie mechanism has been explicitly designed to give space for The Cookie mechanism has been explicitly designed to give space for
various implementation options. It allows a responder implementation various implementation options. It allows a responder implementation
to completely delay session specific state creation until a valid I2 to completely delay session specific state creation until a valid I2
is received. In such a case a validly formatted I2 can be rejected is received. In such a case a validly formatted I2 can be rejected
earliest only once the Responder has checked its validity by earliest only once the Responder has checked its validity by
computing one hash function. On the other hand, the design also computing one hash function. On the other hand, the design also
allows a responder implementation to keep state about received I1s, allows a responder implementation to keep state about received I1s,
and match the received I2s against the state, thereby allowing the and match the received I2s against the state, thereby allowing the
implementation to avoid the computational cost of the hash function. implementation to avoid the computational cost of the hash function.
The drawback of this latter approach is the requirement of creating The drawback of this latter approach is the requirement of creating
state. Finally, it also allows an implementation to use any state. Finally, it also allows an implementation to use other
combination of the space-saving and computation-saving mechanisms. combinations of the space-saving and computation-saving mechanisms.
One possible way for a Responder to remain stateless but drop most One possible way for a Responder to remain stateless but drop most
spoofed I2s is to base the selection of the cookie on some function spoofed I2s is to base the selection of the cookie on some function
over the Initiator's Host Identity. The idea is that the Responder over the Initiator's Host Identity. The idea is that the Responder
has a (perhaps varying) number of pre-calculated R1 packets, and it has a (perhaps varying) number of pre-calculated R1 packets, and it
selects one of these based on the information carried in I1. When selects one of these based on the information carried in I1. When
the Responder then later receives I2, it checks that the cookie in the Responder then later receives I2, it checks that the cookie in
the I2 matches with the cookie sent in the R1, thereby making it the I2 matches with the cookie sent in the R1, thereby making it
impractical for the attacker to first exchange one I1/R1, and then impractical for the attacker to first exchange one I1/R1, and then
generate a large number of spoofed I2s that seemingly come from generate a large number of spoofed I2s that seemingly come from
different IP addresses or use different HITs. The method does not different IP addresses or use different HITs. The method does not
protect from an attacker that uses fixed IP addresses and HITs, protect from an attacker that uses fixed IP addresses and HITs,
though. Against such an attacker it is probably best to create a though. Against such an attacker it is probably best to create a
piece of local state, and remember that the puzzle check has piece of local state, and remember that the puzzle check has
previously failed. See Appendix D for one possible implementation. previously failed. See Appendix C for one possible implementation.
Note, however, that the implementations MUST NOT use the exact Note, however, that the implementations MUST NOT use the exact
implementation given in the appendix, and SHOULD include sufficient implementation given in the appendix, and SHOULD include sufficient
randomness to the algorithm so that algorithm complexity attacks randomness to the algorithm so that algorithm complexity attacks
become impossible [26]. become impossible [27].
The Responder can set the difficulty for Initiator, based on its The Responder can set the puzzle difficulty for Initiator, based on
concern of trust of the Initiator. The Responder SHOULD use its concern of trust of the Initiator. The Responder SHOULD use
heuristics to determine when it is under a denial-of-service attack, heuristics to determine when it is under a denial-of-service attack,
and set the difficulty value K appropriately. and set the puzzle difficulty value K appropriately; see below.
The Responder starts the cookie exchange when it receives an I1. The The Responder starts the cookie exchange when it receives an I1. The
Responder supplies a random number I, and requires the Initiator to Responder supplies a random number I, and requires the Initiator to
find a number J. To select a proper J, the Initiator must create the find a number J. To select a proper J, the Initiator must create the
concatenation of I, the HITs of the parties, and J, and take a SHA-1 concatenation of I, the HITs of the parties, and J, and take a SHA-1
hash over this concatenation. The lowest order K bits of the result hash over this concatenation. The lowest order K bits of the result
MUST be zeros. MUST be zeros. The value K sets the difficulty of the puzzle.
To generate a proper number J, the Initiator will have to generate a To generate a proper number J, the Initiator will have to generate a
number of Js until one produces the hash target of zero. The number of Js until one produces the hash target of zero. The
Initiator SHOULD give up after exceeding the puzzle lifetime received Initiator SHOULD give up after exceeding the puzzle lifetime in the
in PUZZLE TLV. The Responder needs to re-create the concatenation of PUZZLE TLV. The Responder needs to re-create the concatenation of I,
I, the HITs, and the provided J, and compute the hash once to prove the HITs, and the provided J, and compute the hash once to prove that
that the Initiator did its assigned task. the Initiator did its assigned task.
To prevent pre-computation attacks, the Responder MUST select the To prevent pre-computation attacks, the Responder MUST select the
number I in such a way that the Initiator cannot guess it. number I in such a way that the Initiator cannot guess it.
Furthermore, the construction MUST allow the Responder to verify that Furthermore, the construction MUST allow the Responder to verify that
the value was indeed selected by it and not by the Initiator. See the value was indeed selected by it and not by the Initiator. See
Appendix D for an example on how to implement this. Appendix C for an example on how to implement this.
Using the Opaque data field in the ECHO_REQUEST, the Responder can Using the Opaque data field in an ECHO_REQUEST parameter, the
include some data in R1 that the Initiator must copy unmodified in Responder can include some data in R1 that the Initiator must copy
the corresponding I2 packet. The Responder can generate the Opaque unmodified in the corresponding I2 packet. The Responder can
data e.g. using the sent I, some secret and possibly other related generate the Opaque data in various ways; e.g. using the sent I,
data. Using this same secret, received I in I2 packet and possible some secret, and possibly other related data. Using this same
other data, the Receiver can verify that it has itself sent the I to secret, received I in I2 packet and possible other data, the Receiver
the Initiator. The Responder must change the secret periodically. can verify that it has itself sent the I to the Initiator. The
Responder MUST change the secret periodically.
It is RECOMMENDED that the Responder generates a new cookie and a new It is RECOMMENDED that the Responder generates a new cookie and a new
R1 once every few minutes. Furthermore, it is RECOMMENDED that the R1 once every few minutes. Furthermore, it is RECOMMENDED that the
Responder remembers an old cookie at least 2*lifetime seconds after Responder remembers an old cookie at least 2*lifetime seconds after
it has been deprecated. These time values allow a slower Initiator it has been deprecated. These time values allow a slower Initiator
to solve the cookie puzzle while limiting the usability that an old, to solve the cookie puzzle while limiting the usability that an old,
solved cookie has to an attacker. solved cookie has to an attacker.
NOTE: The protocol developers explicitly considered whether R1 should NOTE: The protocol developers explicitly considered whether R1 should
include a timestamp in order to protect the Initiator from replay include a timestamp in order to protect the Initiator from replay
attacks. The decision was NOT to include a timestamp. attacks. The decision was NOT to include a timestamp.
NOTE: The protocol developers explicitly considered whether a memory
bound function should be used for the puzzle instead of a CPU bound
function. The decision was not to use memory bound functions. At
the time of the decision the idea of memory bound functions was
relatively new and their IPR status were unknown. Once there is more
experience about memory bound functions and once their IPR status is
better known, it may be reasonable to reconsider this decision.
In R1, the values I and K are sent in network byte order. Similarly, In R1, the values I and K are sent in network byte order. Similarly,
in I2 the values I and J are sent in network byte order. The SHA-1 in I2 the values I and J are sent in network byte order. The SHA-1
hash is created by concatenating, in network byte order, the hash is created by concatenating, in network byte order, the
following data, in the following order: following data, in the following order:
64-bit random value I, in network byte order, as appearing in R1 64-bit random value I, in network byte order, as appearing in R1
and I2. and I2.
128-bit initiator HIT, in network byte order, as appearing in the 128-bit initiator HIT, in network byte order, as appearing in the
HIP Payload in R1 and I2. HIP Payload in R1 and I2.
128-bit responder HIT, in network byte order, as appearing in the 128-bit responder HIT, in network byte order, as appearing in the
HIP Payload in R1 and I2. HIP Payload in R1 and I2.
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HIP Payload in R1 and I2. HIP Payload in R1 and I2.
128-bit responder HIT, in network byte order, as appearing in the 128-bit responder HIT, in network byte order, as appearing in the
HIP Payload in R1 and I2. HIP Payload in R1 and I2.
64-bit random value J, in network byte order, as appearing in I2. 64-bit random value J, in network byte order, as appearing in I2.
In order to be a valid response cookie, the K low-order bits of the In order to be a valid response cookie, the K low-order bits of the
resulting SHA-1 digest must be zero. resulting SHA-1 digest must be zero.
Notes: Notes:
The length of the data to be hashed is 48 bytes. The length of the data to be hashed is 48 bytes.
All the data in the hash input MUST be in network byte order. All the data in the hash input MUST be in network byte order.
The order of the initiator and responder HITs are different in the The order of the initiator and responder HITs are different in the
R1 and I2 packets, see Section 6.1. Care must be taken to copy R1 and I2 packets, see Section 6.1. Care must be taken to copy
the values in right order to the hash input. the values in right order to the hash input.
Precomputation by the Responder Precomputation by the Responder
Sets up the challenge difficulty K. Sets up the puzzle difficulty K.
Creates a signed R1 and caches it. Creates a signed R1 and caches it.
Responder Responder
Selects a suitable cached R1. Selects a suitable cached R1.
Generates a random number I. Generates a random number I.
Sends I and K in a HIP Cookie in the R1. Sends I and K in an R1.
Saves I and K for a Delta time. Saves I and K for a Delta time.
Initiator Initiator
Generates repeated attempts to solve the challenge until a Generates repeated attempts to solve the puzzle until a matching J
matching J is found: is found:
Ltrunc( SHA-1( I | HIT-I | HIT-R | J ), K ) == 0 Ltrunc( SHA-1( I | HIT-I | HIT-R | J ), K ) == 0
Sends I and J in HIP Cookie in a I2. Sends I and J in an I2.
Responder Responder
Verifies that the received I is a saved one. Verifies that the received I is a saved one.
Finds the right K based on I. Finds the right K based on I.
Computes V := Ltrunc( SHA-1( I | HIT-I | HIT-R | J ), K ) Computes V := Ltrunc( SHA-1( I | HIT-I | HIT-R | J ), K )
Rejects if V != 0 Rejects if V != 0
Accept if V == 0 Accept if V == 0
The Ltrunc (SHA-1(), K) denotes the lowest order K bits of the SHA-1 The Ltrunc (SHA-1(), K) denotes the lowest order K bits of the SHA-1
result. result.
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The packets R1, I2, and R2 implement a standard authenticated The packets R1, I2, and R2 implement a standard authenticated
Diffie-Hellman exchange. The Responder sends its public Diffie-Hellman exchange. The Responder sends its public
Diffie-Hellman key and its public authentication key, i.e., its host Diffie-Hellman key and its public authentication key, i.e., its host
identity, in R1. The signature in R1 allows the Initiator to verify identity, in R1. The signature in R1 allows the Initiator to verify
that the R1 has been once generated by the Responder. However, since that the R1 has been once generated by the Responder. However, since
it is precomputed and therefore does not cover all of the packet, it it is precomputed and therefore does not cover all of the packet, it
does not protect from replay attacks. does not protect from replay attacks.
When the Initiator receives an R1, it computes the Diffie-Hellman When the Initiator receives an R1, it computes the Diffie-Hellman
session key. It creates a HIP security association using keying session key. It creates a HIP association using keying material from
material from the session key (see Section 9), and uses the security the session key (see Section 9), and uses the association to encrypt
association to encrypt its public authentication key, i.e., host its public authentication key, i.e., host identity. The resulting I2
identity. The resulting I2 contains the Initiator's Diffie-Hellman contains the Initiator's Diffie-Hellman key and its encrypted public
key and its the encrypted public authentication key. The signature authentication key. The signature in I2 covers all of the packet.
in I2 covers all of the packet.
The Responder extracts the Initiator Diffie-Hellman public key from The Responder extracts the Initiator Diffie-Hellman public key from
the I2, computes the Diffie-Hellman session key, creates a the I2, computes the Diffie-Hellman session key, creates a
corresponding HIP security association, and decrypts the Initiator's corresponding HIP association, and decrypts the Initiator's public
public authentication key. It can then verify the signature using authentication key. It can then verify the signature using the
the authentication key. authentication key.
The final message, R2, is needed to protect the Initiator from replay The final message, R2, is needed to protect the Initiator from replay
attacks. attacks.
4.1.3 HIP replay protection 4.1.3 HIP replay protection
The HIP protocol includes the following mechanisms to protect against The HIP protocol includes the following mechanisms to protect against
malicious replays. Responders are protected against replays of I1 malicious replays. Responders are protected against replays of I1
packets by virtue of the stateless response to I1s with presigned R1 packets by virtue of the stateless response to I1s with presigned R1
messages. Initiators are protected against R1 replays by a messages. Initiators are protected against R1 replays by a
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Responders are protected against replays or false I2s by the cookie Responders are protected against replays or false I2s by the cookie
mechanism (Section 4.1.1 above), and optional use of opaque data. mechanism (Section 4.1.1 above), and optional use of opaque data.
Hosts are protected against replays to R2s and UPDATEs by use of a Hosts are protected against replays to R2s and UPDATEs by use of a
less expensive HMAC verification preceding HIP signature less expensive HMAC verification preceding HIP signature
verification. verification.
The R1 generation counter is a monotonically increasing 64-bit The R1 generation counter is a monotonically increasing 64-bit
counter that may be initialized to any value. The scope of the counter that may be initialized to any value. The scope of the
counter MAY be system-wide but SHOULD be per host identity, if there counter MAY be system-wide but SHOULD be per host identity, if there
is more than one local host identity. The value of this counter is more than one local host identity. The value of this counter
SHOULD be kept across system reboots and invocations of the HIP SHOULD be kept across system reboots and invocations of the HIP base
signaling process. This counter indicates the current generation of exchange. This counter indicates the current generation of cookie
cookie puzzles. Implementations MUST accept puzzles from the current puzzles. Implementations MUST accept puzzles from the current
generation and MAY accept puzzles from earlier generations. A generation and MAY accept puzzles from earlier generations. A
system's local counter MUST be incremented at least as often as every system's local counter MUST be incremented at least as often as every
time old R1s cease to be valid, and SHOULD never be decremented, lest time old R1s cease to be valid, and SHOULD never be decremented, lest
the host expose its peers to the replay of previously generated, the host expose its peers to the replay of previously generated,
higher numbered R1s. Also, the R1 generation counter MUST NOT roll higher numbered R1s. Also, the R1 generation counter MUST NOT roll
over; if the counter is about to become exhausted, the corresponding over; if the counter is about to become exhausted, the corresponding
HI must be abandoned and replaced with a new one. HI must be abandoned and replaced with a new one.
A host may receive more than one R1, either due to sending multiple A host may receive more than one R1, either due to sending multiple
I1s (Section 8.4.1) or due to a replay of an old R1. When sending I1s (Section 8.4.1) or due to a replay of an old R1. When sending
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processing with the fresher R1, as if it were the first R1 to arrive. processing with the fresher R1, as if it were the first R1 to arrive.
Upon conclusion of an active HIP association with another host, the Upon conclusion of an active HIP association with another host, the
R1 generation counter associated with the peer host SHOULD be R1 generation counter associated with the peer host SHOULD be
flushed. A local policy MAY override the default flushing of R1 flushed. A local policy MAY override the default flushing of R1
counters on a per-HIT basis. The reason for recommending the counters on a per-HIT basis. The reason for recommending the
flushing of this counter is that there may be hosts where the R1 flushing of this counter is that there may be hosts where the R1
generation counter (occasionally) decreases; e.g., due to hardware generation counter (occasionally) decreases; e.g., due to hardware
failure. failure.
4.2 TCP and UDP pseudo-header computation 4.2 TCP and UDP pseudo-header computation for user data
When computing TCP and UDP checksums on sockets bound to HITs or When computing TCP and UDP checksums on user data packets that flow
LSIs, the IPv6 pseudo-header format [11] MUST be used. Additionally, through sockets bound to HITs or LSIs, the IPv6 pseudo-header format
the HITs MUST be used in the place of the IPv6 addresses in the IPv6 [11] MUST be used. Additionally, the HITs MUST be used in the place
pseudo-header. Note that the pseudo-header for actual HIP payloads of the IPv6 addresses in the IPv6 pseudo-header. Note that the
is computed differently; see Section 6.1.2. pseudo-header for actual HIP payloads is computed differently; see
Section 6.1.2.
4.3 Updating a HIP association 4.3 Updating a HIP association
A HIP association between two hosts may need to be updated over time. A HIP association between two hosts may need to be updated over time.
Examples include the need to rekey expiring security associations, Examples include the need to rekey expiring user data security
add new security associations, or change IP addresses associated with associations, add new security associations, or change IP addresses
hosts. This document only specifies how UPDATE is used for rekeying; associated with hosts. The UPDATE packet is used for those and other
other uses are deferred to other drafts. similar purposes. This document only specifies the UPDATE packet
format and basic processing rules, with mandatory TLVs. The actual
usage is defined in separate specifications.
HIP provides a general purpose UPDATE packet, which can carry HIP provides a general purpose UPDATE packet, which can carry
multiple HIP parameters, for updating the HIP state between two multiple HIP parameters, for updating the HIP state between two
peers. The UPDATE mechanism has the following properties: peers. The UPDATE mechanism has the following properties:
UPDATE messages carry a monotonically increasing sequence number UPDATE messages carry a monotonically increasing sequence number
and are explicitly acknowledged by the peer. Lost UPDATEs or and are explicitly acknowledged by the peer. Lost UPDATEs or
acknowledgments may be recovered via retransmission. Multiple acknowledgments may be recovered via retransmission. Multiple
UPDATE messages may be outstanding. UPDATE messages may be outstanding.
UPDATE is protected by both HMAC and HIP_SIGNATURE parameters, UPDATE is protected by both HMAC and HIP_SIGNATURE parameters,
since processing UPDATE signatures alone is a potential DoS attack since processing UPDATE signatures alone is a potential DoS attack
against intermediate systems. against intermediate systems.
The UPDATE packet is defined in Section 7.6. The UPDATE packet is defined in Section 7.6.
4.4 Error processing 4.4 Error processing
HIP error processing behaviour depends on whether there exists an HIP error processing behaviour depends on whether there exists an
active HIP association or not. In general, if an HIP security active HIP association or not. In general, if an HIP association
association exists between the sender and receiver of a packet exists between the sender and receiver of a packet causing an error
causing an error condition, the receiver SHOULD respond with a NOTIFY condition, the receiver SHOULD respond with a NOTIFY packet. On the
packet. On the other hand, if there are no existing HIP security other hand, if there are no existing HIP associations between the
associations between the sender and receiver, or the receiver cannot sender and receiver, or the receiver cannot reasonably determine the
reasonably determine the identity of the sender, the receiver MAY identity of the sender, the receiver MAY respond with a suitable ICMP
respond with a suitable ICMP message; see Section 6.3 for more message; see Section 6.3 for more details.
details.
4.5 Certificate distribution 4.5 Certificate distribution
HIP does not define how to use certificates. However, it does define HIP does not define how to use certificates. However, it does define
a simple certificate transport mechanisms that MAY be used to a simple certificate transport mechanisms that MAY be used to
implement certificate based security policies. The certificate implement certificate-based security policies. The certificate
payload is defined in Section 6.2.11, and the certificate packet in payload is defined in Section 6.2.9, and the certificate packet in
Section 7.5. Section 7.5.
4.6 Sending data on HIP packets 4.6 Sending data on HIP packets
A future version of this document may define how to include ESP A future version of this document may define how to include user data
protected data on various HIP packets. However, currently the HIP on various HIP packets. However, currently the HIP header is a
header is a terminal header, and not followed by any other headers. terminal header, and not followed by any other headers.
4.7 Transport Formats
The actual data transmission format, used for user data after the HIP
base exchange, is not defined in this document. Such transport
formats and methods are described in separate specifications. All
HIP implementations MUST implement, at minimum, the ESP transport
format for HIP [23].
When new transport formats are defined, the corresponding parameters
MUST have smaller type value than the ESP_TRANSFORM parameter. The
order in which the transport formats are presented in the R1 packet,
is the preferred order. The last of the transport formats MUST be
ESP transport format, represented by the ESP_TRANSFORM parameter.
5. HIP protocol overview 5. HIP protocol overview
The following material is an overview of the HIP protocol operation. The following material is an overview of the HIP protocol operation.
Section 8 describes the packet processing steps in more detail. Section 8 describes the packet processing steps in more detail.
A typical HIP packet flow is shown below, between an Initiator (I) A typical HIP packet flow is shown below, between an Initiator (I)
and a Responder (R). It illustrates the exchange of four HIP packets and a Responder (R). It illustrates the exchange of four HIP packets
(I1, R1, I2, and R2). (I1, R1, I2, and R2).
I --> Directory: lookup R I --> Directory: lookup R
I <-- Directory: return R's addresses, and HI and/or HIT I <-- Directory: return R's addresses, and HI and/or HIT
I1 I --> R (Hi. Here is my I1, let's talk HIP) I1 I --> R (Hi. Here is my I1, let's talk HIP)
R1 I <-- R (OK. Here is my R1, handle this HIP cookie) R1 I <-- R (OK. Here is my R1, handle this HIP cookie)
I2 I --> R (Compute, compute, here is my counter I2) I2 I --> R (Compute, compute, here is my counter I2)
R2 I <-- R (OK. Let's finish HIP with my R2) R2 I <-- R (OK. Let's finish HIP with my R2)
I --> R (ESP protected data) I --> R (data)
I <-- R (ESP protected data) I <-- R (data)
By definition, the system initiating a HIP exchange is the Initiator, By definition, the system initiating a HIP exchange is the Initiator,
and the peer is the Responder. This distinction is forgotten once and the peer is the Responder. This distinction is forgotten once
the base exchange completes, and either party can become the the base exchange completes, and either party can become the
initiator in future communications. initiator in future communications.
5.1 HIP Scenarios 5.1 HIP Scenarios
The HIP protocol and state machine is designed to recover from one of The HIP protocol and state machine is designed to recover from one of
the parties crashing and losing its state. The following scenarios the parties crashing and losing its state. The following scenarios
describe the main use cases covered by the design. describe the main use cases covered by the design.
No prior state between the two systems. No prior state between the two systems.
The system with data to send is the Initiator. The process The system with data to send is the Initiator. The process
follows the standard four packet base exchange, establishing follows the standard four packet base exchange, establishing
the SAs. the HIP association.
The system with data to send has no state with the receiver, but The system with data to send has no state with the receiver, but
the receiver has a residual SA. the receiver has a residual HIP association.
The system with data to send is the Initiator. The Initiator The system with data to send is the Initiator. The Initiator
acts as in no prior state, sending I1 and getting R1. When the acts as in no prior state, sending I1 and getting R1. When the
Responder receives a valid I2, the old SAs are 'discovered' and Responder receives a valid I2, the old association is
deleted, and the new SAs are established. 'discovered' and deleted, and the new association is
The system with data to send has an SA, but the receiver does not. established.
The system sends data on the outbound SA. The receiver The system with data to send has an HIP association, but the
'detects' the situation when it receives an ESP packet that receiver does not.
contains an unknown SPI. The receiving host MUST discard this The system sends data on the outbound user data security
packet, in accordance with IPsec architecture. Optionally, the association. The receiver 'detects' the situation when it
receiving host MAY send an ICMP packet with the Parameter receives a user data packet that it cannot match to any HIP
Problem type to inform about invalid SPI (see Section 6.3, and association. The receiving host MUST discard this packet.
it MAY initiate a new HIP negotiation. However, responding Optionally, the receiving host MAY send an ICMP packet with the
with these optional mechanisms is implementation or policy Parameter Problem type to inform about non-existing HIP
dependent. association (see Section 6.3), and it MAY initiate a new HIP
negotiation. However, responding with these optional
A system determines that it needs to reset ESP Sequence Number, or mechanisms is implementation or policy dependent.
rekey.
The system sends a HIP UPDATE packet. The peer responds with a
HIP UPDATE response. The UPDATE exchanges can refresh or
establish new SAs for peers.
5.2 Refusing a HIP exchange 5.2 Refusing a HIP exchange
A HIP aware host may choose not to accept a HIP exchange. If the A HIP aware host may choose not to accept a HIP exchange. If the
host's policy is to only be an Initiator, it should begin its own HIP host's policy is to only be an Initiator, it should begin its own HIP
exchange. A host MAY choose to have such a policy since only the exchange. A host MAY choose to have such a policy since only the
Initiator HI is protected in the exchange. There is a risk of a race Initiator HI is protected in the exchange. There is a risk of a race
condition if each host's policy is to only be an Initiator, at which condition if each host's policy is to only be an Initiator, at which
point the HIP exchange will fail. point the HIP exchange will fail.
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If a host reboots or times out, it has lost its HIP state. If the If a host reboots or times out, it has lost its HIP state. If the
system that lost state has a datagram to deliver to its peer, it system that lost state has a datagram to deliver to its peer, it
simply restarts the HIP exchange. The peer replies with an R1 HIP simply restarts the HIP exchange. The peer replies with an R1 HIP
packet, but does not reset its state until it receives the I2 HIP packet, but does not reset its state until it receives the I2 HIP
packet. The I2 packet MUST have a valid solution to the puzzle and, packet. The I2 packet MUST have a valid solution to the puzzle and,
if inserted in R1, a valid Opaque data as well as a valid signature. if inserted in R1, a valid Opaque data as well as a valid signature.
Note that either the original Initiator or the Responder could end up Note that either the original Initiator or the Responder could end up
restarting the exchange, becoming the new Initiator. restarting the exchange, becoming the new Initiator.
If a system receives an ESP packet for an unknown SPI, it is possible If a system receives a user data packet that cannot be matched to any
that it has lost the state and its peer has not. It MAY send an ICMP existing HIP association, it is possible that it has lost the state
packet with the Parameter Problem type, the Pointer pointing to the and its peer has not. It MAY send an ICMP packet with the Parameter
SPI value within the ESP header. Reacting to ESP traffic with unknown Problem type, the Pointer pointing to the referred HIP-related
SPI depends on the implementation and the environment where the association information. Reacting to such traffic depends on the
implementation is used. implementation and the environment where the implementation is used.
The initiating host cannot know, if the SA indicated by the received
ESP packet is either a HIP SA or and IKE SA. If the old SA was not a
HIP SA, the peer may not respond to the I1 packet.
After sending the I1, the HIP negotiation proceeds as normally and, After sending the I1, the HIP negotiation proceeds as normally and,
when successful, the SA is created at the initiating end. The peer when successful, the SA is created at the initiating end. The peer
end removes the OLD SA and replaces it with the new one. end removes the OLD SA and replaces it with the new one.
5.4 HIP State Machine 5.4 HIP State Machine
The HIP protocol itself has very little state. In the HIP base The HIP protocol itself has little state. In the HIP base exchange,
exchange, there is an Initiator and a Responder. Once the SAs are there is an Initiator and a Responder. Once the SAs are established,
established, this distinction is lost. If the HIP state needs to be this distinction is lost. If the HIP state needs to be
re-established, the controlling parameters are which peer still has re-established, the controlling parameters are which peer still has
state and which has a datagram to send to its peer. The following state and which has a datagram to send to its peer. The following
state machine attempts to capture these processes. state machine attempts to capture these processes.
The state machine is presented in a single system view, representing The state machine is presented in a single system view, representing
either an Initiator or a Responder. There is not a complete overlap either an Initiator or a Responder. There is not a complete overlap
of processing logic here and in the packet definitions. Both are of processing logic here and in the packet definitions. Both are
needed to completely implement HIP. needed to completely implement HIP.
Implementors must understand that the state machine, as described Implementors must understand that the state machine, as described
here, is informational. Specific implementations are free to here, is informational. Specific implementations are free to
implement the actual functions differently. Section 8 describes the implement the actual functions differently. Section 8 describes the
packet processing rules in more detail. This state machine focuses packet processing rules in more detail. This state machine focuses
on the HIP I1, R1, I2, R2, and UPDATE packets only, and specifically, on the HIP I1, R1, I2, and R2 packets only. Other states may be
the state induced by an UPDATE that triggers a rekeying event. Other introduced by mechanisms in other drafts (such as mobility and
states may be introduced by mechanisms in other drafts (such as multihoming).
mobility and multihoming).
5.4.1 HIP States 5.4.1 HIP States
UNASSOCIATED State machine start +---------------------+---------------------------------------------+
I1-SENT Initiating HIP | State | Explanation |
I2-SENT Waiting to finish HIP +---------------------+---------------------------------------------+
R2-SENT Waiting to finish HIP | UNASSOCIATED | State machine start |
ESTABLISHED HIP SA established | | |
REKEYING HIP SA established, but UPDATE is outstanding for rekeying | I1-SENT | Initiating HIP |
CLOSING HIP SA closing, no data (ESP) can be sent | | |
CLOSED HIP SA closed, no data (ESP) can be sent | I2-SENT | Waiting to finish HIP |
E-FAILED HIP exchange failed | | |
| R2-SENT | Waiting to finish HIP |
| | |
| ESTABLISHED | HIP association established |
| | |
| CLOSING | HIP association closing, no data can be |
| | sent |
| | |
| CLOSED | HIP association closed, no data can be sent |
| | |
| E-FAILED | HIP exchange failed |
+---------------------+---------------------------------------------+
5.4.2 HIP State Processes 5.4.2 HIP State Processes
+------------+ +------------+
|UNASSOCIATED| Start state |UNASSOCIATED| Start state
+------------+ +------------+
User data to send requiring a new HIP association, send I1 and go to I1-SENT
Datagram to send requiring a new SA, send I1 and go to I1-SENT
Receive I1, send R1 and stay at UNASSOCIATED Receive I1, send R1 and stay at UNASSOCIATED
Receive I2, process Receive I2, process
if successful, send R2 and go to R2-SENT if successful, send R2 and go to R2-SENT
if fail, stay at UNASSOCIATED if fail, stay at UNASSOCIATED
Receive ESP for unknown SA, optionally send ICMP as defined Receive user data for unknown HIP association, optionally send ICMP as
in defined in
Section 6.3 Section 6.3
and stay at UNASSOCIATED and stay at UNASSOCIATED
Receive CLOSE, optionally send ICMP Parameter Problem and stay
Receive CLOSE, or UPDATE, optionally send ICMP Parameter in UNASSOCIATED.
Problem and stay in UNASSOCIATED.
Receive ANYOTHER, drop and stay at UNASSOCIATED Receive ANYOTHER, drop and stay at UNASSOCIATED
+---------+ +---------+
| I1-SENT | Initiating HIP | I1-SENT | Initiating HIP
+---------+ +---------+
Receive I1, send R1 and stay at I1-SENT Receive I1, send R1 and stay at I1-SENT
Receive I2, process Receive I2, process
if successful, send R2 and go to R2-SENT if successful, send R2 and go to R2-SENT
skipping to change at page 25, line 17 skipping to change at page 26, line 19
| R2-SENT | Waiting to finish HIP | R2-SENT | Waiting to finish HIP
+---------+ +---------+
Receive I1, send R1 and stay at R2-SENT Receive I1, send R1 and stay at R2-SENT
Receive I2, process, Receive I2, process,
if successful, send R2, and cycle at R2-SENT if successful, send R2, and cycle at R2-SENT
if failed, stay at R2-SENT if failed, stay at R2-SENT
Receive R1, drop and stay at R2-SENT Receive R1, drop and stay at R2-SENT
Receive R2, drop and stay at R2-SENT Receive R2, drop and stay at R2-SENT
Receive ESP for SA, process and go to ESTABLISHED
Receive UPDATE, go to ESTABLISHED and process from ESTABLISHED state
Move to ESTABLISHED after an implementation specific time. Move to ESTABLISHED after an implementation specific time.
+------------+ +------------+
|ESTABLISHED | HIP SA established |ESTABLISHED | HIP association established
+------------+ +------------+
Receive I1, send R1 and stay at ESTABLISHED Receive I1, send R1 and stay at ESTABLISHED
Receive I2, process with cookie and possible Opaque data verification Receive I2, process with cookie and possible Opaque data verification
if successful, send R2, drop old SAs, establish new SA, go to if successful, send R2, drop old HIP association, establish a new
R2-SENT HIP association, to to R2-SENT
if fail, stay at ESTABLISHED if fail, stay at ESTABLISHED
Receive R1, drop and stay at ESTABLISHED Receive R1, drop and stay at ESTABLISHED
Receive R2, drop and stay at ESTABLISHED Receive R2, drop and stay at ESTABLISHED
Receive ESP for SA, process and stay at ESTABLISHED Receive user data for HIP association, process and stay at ESTABLISHED
Receive UPDATE, process No packet sent/received during UAL minutes, send CLOSE and go to CLOSING.
if successful, send UPDATE in reply and go to REKEYING
if failed, stay at ESTABLISHED
Need rekey,
send UPDATE and go to REKEYING
No packet sent/received during UAL minutes, send CLOSE and go to
CLOSING.
Receive CLOSE, process Receive CLOSE, process
if successful, send CLOSE_ACK and go to CLOSED if successful, send CLOSE_ACK and go to CLOSED
if failed, stay at ESTABLISHED if failed, stay at ESTABLISHED
+---------+ +---------+
| CLOSING | HIP association has not been used for UAL (Unused | CLOSING | HIP association has not been used for UAL (Unused
+---------+ Association Lifetime) minutes. +---------+ Association Lifetime) minutes.
Datagram to send, requires the creation of another incarnation User data to send, requires the creation of another incarnation
of the HIP association, started by sending an I1, of the HIP association, started by sending an I1,
and stay at CLOSING and stay at CLOSING
Receive I1, send R1 and stay at CLOSING Receive I1, send R1 and stay at CLOSING
Receive I2, process Receive I2, process
if successful, send R2 and go to R2-SENT if successful, send R2 and go to R2-SENT
if fail, stay at CLOSING if fail, stay at CLOSING
Receive R1, process Receive R1, process
if successful, send I2 and go to I2-SENT if successful, send I2 and go to I2-SENT
if fail, stay at CLOSING if fail, stay at CLOSING
Receive CLOSE, process Receive CLOSE, process
if successful, send CLOSE_ACK, discard state and go to CLOSED if successful, send CLOSE_ACK, discard state and go to CLOSED
if failed, stay at CLOSING if failed, stay at CLOSING
Receive CLOSE_ACK, process Receive CLOSE_ACK, process
if successful, discard state and go to UNASSOCIATED if successful, discard state and go to UNASSOCIATED
if failed, stay at CLOSING if failed, stay at CLOSING
skipping to change at page 27, line 4 skipping to change at page 27, line 43
if successful, send R2 and go to R2-SENT if successful, send R2 and go to R2-SENT
if fail, stay at CLOSED if fail, stay at CLOSED
Receive R1, process Receive R1, process
if successful, send I2 and go to I2-SENT if successful, send I2 and go to I2-SENT
if fail, stay at CLOSED if fail, stay at CLOSED
Receive CLOSE, process Receive CLOSE, process
if successful, send CLOSE_ACK, stay at CLOSED if successful, send CLOSE_ACK, stay at CLOSED
if failed, stay at CLOSED if failed, stay at CLOSED
Receive CLOSE_ACK, process Receive CLOSE_ACK, process
if successful, discard state and go to UNASSOCIATED if successful, discard state and go to UNASSOCIATED
if failed, stay at CLOSED if failed, stay at CLOSED
Receive ANYOTHER, drop and stay at CLOSED Receive ANYOTHER, drop and stay at CLOSED
Timeout (UAL + 2MSL), discard state and go to UNASSOCIATED Timeout (UAL + 2MSL), discard state and go to UNASSOCIATED
+----------+
| REKEYING | HIP SA established, rekey pending
+----------+
Receive I1, send R1 and stay at REKEYING
Receive I2, process with cookie and possible Opaque data verification
if successful, send R2, drop old SA and go to R2-SENT
if fail, stay at REKEYING
Receive R1, drop and stay at REKEYING
Receive R2, drop and stay at REKEYING
Receive ESP for SA, process and stay at REKEYING
Receive UPDATE, process
if successful completion of rekey, go to ESTABLISHED
if failed, stay at REKEYING
Timeout, increment timeout counter
If counter is less than UPDATE_RETRIES_MAX, send UPDATE and stay at
REKEYING
If counter is greater than UPDATE_RETRIES_MAX, go to E-FAILED
+----------+ +----------+
| E-FAILED | HIP failed to establish association with peer | E-FAILED | HIP failed to establish association with peer
+----------+ +----------+
Move to UNASSOCIATED after an implementation specific time. Re-negotiation Move to UNASSOCIATED after an implementation specific time. Re-negotiation
is possible after moving to UNASSOCIATED state. is possible after moving to UNASSOCIATED state.
5.4.3 Simplified HIP State Diagram 5.4.3 Simplified HIP State Diagram
The following diagram shows the major state transitions. Transitions The following diagram shows the major state transitions. Transitions
based on received packets implicitly assume that the packets are based on received packets implicitly assume that the packets are
successfully authenticated or processed. The diagram assumes that successfully authenticated or processed.
UPDATE messages are being used for rekeying.
+-+ +------------------------------+ +-+ +------------------------------+
I1 received, send R1 | | | | I1 received, send R1 | | | |
| v v | | v v |
Datagram to send +--------------+ I2 received, send R2 | Datagram to send +--------------+ I2 received, send R2 |
+---------------| UNASSOCIATED |---------------+ | +---------------| UNASSOCIATED |---------------+ |
| +--------------+ | | | +--------------+ | |
v | | v | |
+---------+ I2 received, send R2 | | +---------+ I2 received, send R2 | |
+---->| I1-SENT |---------------------------------------+ | | +---->| I1-SENT |---------------------------------------+ | |
skipping to change at page 28, line 21 skipping to change at page 28, line 37
| | +------------------------+ | | | | | +------------------------+ | | |
| | R1 received, | I2 received, send R2 | | | | | | R1 received, | I2 received, send R2 | | | |
| v send I2 | v v v | | v send I2 | v v v |
| +---------+ | +---------+ | | +---------+ | +---------+ |
| +->| I2-SENT |------------+ | R2-SENT |<-----+ | | +->| I2-SENT |------------+ | R2-SENT |<-----+ |
| | +---------+ +---------+ | | | | +---------+ +---------+ | |
| | | | | | | | | | | |
| | | | | | | | | | | |
| |receive | | | | | |receive | | | |
| |R1, send | timeout, | receive I2,| | | |R1, send | timeout, | receive I2,| |
| |I2 |R2 received +--------------+ ESP | send R2| | | |I2 |R2 received +--------------+ data | send R2| |
| | +----------->| ESTABLISHED |<---------+ | | | | +----------->| ESTABLISHED |<---------+ | |
| | +--------------+ | | | | +--------------+ | |
| | Update received/ | ^ | | | | | | | | | | | |
| | Update triggered | | | | +---------------------------+ | | | | | +---------------------------+ |
| | +----------------+ | | | | | | | | | | |
| | | | | | No packet sent/received | | | | | | No packet sent/received | |
| | v | | | for UAL min, send CLOSE | | | | | | for UAL min, send CLOSE | |
| | +----------+ | | | | | | | | | | |
| | | REKEYING |-------------+ | | +---------+<-+ timeout | | | | | | +---------+<-+ timeout | |
| | +----------+ UPDATE acked | +--->| CLOSING |--+ (UAL+MSL) | | | | | +--->| CLOSING |--+ (UAL+MSL) | |
| | and NES received | +---------+ retransmit | | | | | +---------+ retransmit | |
+--+----------------------------+---------+ | | | | CLOSE | | +--+----------------------------+---------+ | | | | CLOSE | |
| +----------------------------+-----------+ | | +----------------+ | | +----------------------------+-----------+ | | +----------------+ |
| | | +-----------+ +------------------+--+ | | | +-----------+ +------------------+--+
| | | | receive CLOSE, CLOSE_ACK | | | | | | receive CLOSE, CLOSE_ACK | |
| | | | send CLOSE_ACK received or | | | | | | send CLOSE_ACK received or | |
| | v v timeout | | | | v v timeout | |
| | +--------+ (UAL+MSL) | | | | +--------+ (UAL+MSL) | |
| +---------------------------| CLOSED |---------------------------+ | | +---------------------------| CLOSED |---------------------------+ |
+------------------------------+--------+------------------------------+ +------------------------------+--------+------------------------------+
Datagram to send ^ | timeout (UAL+2MSL), Datagram to send ^ | timeout (UAL+2MSL),
skipping to change at page 29, line 38 skipping to change at page 30, line 38
| | | |
/ HIP Parameters / / HIP Parameters /
/ / / /
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The HIP header is logically an IPv6 extension header. However, this The HIP header is logically an IPv6 extension header. However, this
document does not describe processing for Next Header values other document does not describe processing for Next Header values other
than decimal 59, IPPROTO_NONE, the IPV6 no next header value. Future than decimal 59, IPPROTO_NONE, the IPV6 no next header value. Future
documents MAY do so. However, implementations MUST ignore trailing documents MAY do so. However, implementations MUST ignore trailing
data if a Next Header value is received that is not implemented. data if an unimplemented Next Header value is received.
The Header Length field contains the length of the HIP Header and the The Header Length field contains the length of the HIP Header and HIP
length of HIP parameters in 8 bytes units, excluding the first 8 parameters in 8 bytes units, excluding the first 8 bytes. Since all
bytes. Since all HIP headers MUST contain the sender's and HIP headers MUST contain the sender's and receiver's HIT fields, the
receiver's HIT fields, the minimum value for this field is 4, and minimum value for this field is 4, and conversely, the maximum length
conversely, the maximum length of the HIP Parameters field is of the HIP Parameters field is (255*8)-32 = 2008 bytes. Note: this
(255*8)-32 = 2008 bytes. Note: this sets an additional limit for sets an additional limit for sizes of TLVs included in the Parameters
sizes of TLVs included in the Parameters field, independent of the field, independent of the individual TLV parameter maximum lengths.
individual TLV parameter maximum lengths.
The Packet Type indicates the HIP packet type. The individual packet The Packet Type indicates the HIP packet type. The individual packet
types are defined in the relevant sections. If a HIP host receives a types are defined in the relevant sections. If a HIP host receives a
HIP packet that contains an unknown packet type, it MUST drop the HIP packet that contains an unknown packet type, it MUST drop the
packet. packet.
The HIP Version is four bits. The current version is 1. The version The HIP Version is four bits. The current version is 1. The version
number is expected to be incremented only if there are incompatible number is expected to be incremented only if there are incompatible
changes to the protocol. Most extensions can be handled by defining changes to the protocol. Most extensions can be handled by defining
new packet types, new parameter types, or new controls. new packet types, new parameter types, or new controls.
skipping to change at page 30, line 34 skipping to change at page 31, line 33
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SHT | DHT | | | | | | | | |C|A| | SHT | DHT | | | | | | | | |C|A|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
C - Certificate One or more certificate packets (CER) follows this C - Certificate One or more certificate packets (CER) follows this
HIP packet (see Section 7.5). HIP packet (see Section 7.5).
A - Anonymous If this is set, the sender's HI in this packet is A - Anonymous If this is set, the sender's HI in this packet is
anonymous, i.e., one not listed in a directory. Anonymous HIs anonymous, i.e., one not listed in a directory. Anonymous HIs
SHOULD NOT be stored. This control is set in packets R1 and/or SHOULD NOT be stored. This control is set in packets R1 and/or
I2. The peer receiving an anonymous HI may choose to refuse it by I2. The peer receiving an anonymous HI may choose to refuse it.
silently dropping the exchange.
SHT - Sender's HIT Type Currently the following values are specified: SHT - Sender's HIT Type Currently the following values are specified:
0 RESERVED 0 RESERVED
1 Type 1 HIT 1 Type 1 HIT
2 Type 2 HIT 2 Type 2 HIT
3-6 UNASSIGNED 3-6 UNASSIGNED
7 RESERVED 7 RESERVED
DHT - Destination's HIT Type Using the same values as SHT. DHT - Destination's HIT Type Using the same values as SHT.
The rest of the fields are reserved for future use and MUST be set to The rest of the fields are reserved for future use and MUST be set to
zero on sent packets and ignored on received packets. zero on sent packets and ignored on received packets.
6.1.2 Checksum 6.1.2 Checksum
The checksum field is located at the same location within the header The checksum field is located at the same location within the header
as the checksum field in UDP packets, enabling hardware assisted as the checksum field in UDP packets, enabling hardware assisted
checksum generation and verification. Note that since the checksum checksum generation and verification. Note that since the checksum
covers the source and destination addresses in the IP header, it must covers the source and destination addresses in the IP header, it must
be recomputed on HIP based NAT boxes. be recomputed on HIP-aware NAT boxes.
If IPv6 is used to carry the HIP packet, the pseudo-header [11] If IPv6 is used to carry the HIP packet, the pseudo-header [11]
contains the source and destination IPv6 addresses, HIP packet length contains the source and destination IPv6 addresses, HIP packet length
in the pseudo-header length field, a zero field, and the HIP protocol in the pseudo-header length field, a zero field, and the HIP protocol
number (TBD, see Section 4) in the Next Header field. The length number (TBD, see Section 4) in the Next Header field. The length
field is in bytes and can be calculated from the HIP header length field is in bytes and can be calculated from the HIP header length
field: (HIP Header Length + 1) * 8. field: (HIP Header Length + 1) * 8.
In case of using IPv4, the IPv4 UDP pseudo header format [1] is used. In case of using IPv4, the IPv4 UDP pseudo header format [1] is used.
In the pseudo header, the source and destination addresses are those In the pseudo header, the source and destination addresses are those
used in the IP header, the zero field is obviously zero, the protocol used in the IP header, the zero field is obviously zero, the protocol
is the HIP protocol number (TBD, see Section 4), and the length is is the HIP protocol number (TBD, see Section 4), and the length is
calculated as in the IPv6 case. calculated as in the IPv6 case.
6.2 HIP parameters 6.2 HIP parameters
The HIP Parameters are used to carry the public key associated with The HIP Parameters are used to carry the public key associated with
the sender's HIT, together with other related security information. the sender's HIT, together with other related security and other
The HIP Parameters consists of ordered parameters, encoded in TLV information. The HIP Parameters consists of ordered parameters,
format. encoded in TLV format.
The following parameter types are currently defined. The following parameter types are currently defined.
TLV Type Length Data +-----------------+-------+----------+------------------------------+
| TLV | Type | Length | Data |
SPI 1 4 Remote's SPI. +-----------------+-------+----------+------------------------------+
| R1_COUNTER | 2 | 12 | System Boot Counter |
R1_COUNTER 2 12 System Boot Counter | | | | |
| PUZZLE | 5 | 12 | K and Random #I |
PUZZLE 5 12 K and Random #I | | | | |
| SOLUTION | 7 | 20 | K, Random #I and puzzle |
SOLUTION 7 20 K, Random #I and puzzle solution | | | | solution J |
| | | | |
NES 9 12 Old SPI, New SPI and other | SEQ | 11 | 4 | Update packet ID number |
info needed for UPDATE | | | | |
| ACK | 13 | variable | Update packet ID number |
SEQ 11 4 Update packet ID number | | | | |
| DIFFIE_HELLMAN | 15 | variable | public key |
ACK 13 variable Update packet ID number | | | | |
| HIP_TRANSFORM | 17 | variable | HIP Encryption and Integrity |
DIFFIE_HELLMAN 15 variable public key | | | | Transform |
| | | | |
HIP_TRANSFORM 17 variable HIP Encryption and Integrity | ENCRYPTED | 21 | variable | Encrypted part of I2 or CER |
Transform | | | | packets |
| | | | |
ESP_TRANSFORM 19 variable ESP Encryption and | HOST_ID | 35 | variable | Host Identity with Fully |
Authentication Transform | | | | Qualified Domain Name or NAI |
ENCRYPTED 21 variable Encrypted part of I2 or CER | | | | |
packets | CERT | 64 | variable | HI Certificate |
| | | | |
HOST_ID 35 variable Host Identity with Fully | NOTIFY | 256 | variable | Informational data |
Qualified Domain Name | | | | |
| ECHO_REQUEST | 1022 | variable | Opaque data to be echoed |
CERT 64 variable HI certificate | | | | back; under signature |
| | | | |
NOTIFY 256 variable Informational data | ECHO_RESPONSE | 1024 | variable | Opaque data echoed back; |
| | | | under signature |
ECHO_REQUEST 1022 variable Opaque data to be echoed back; | | | | |
under signature | HMAC | 65245 | 20 | HMAC based message |
| | | | authentication code, with |
ECHO_RESPONSE 1024 variable Opaque data echoed back; under | | | | key material from |
signature | | | | HIP_TRANSFORM |
| | | | |
HMAC 65245 20 HMAC based message | HMAC_2 | 65247 | 20 | HMAC based message |
authentication code, with | | | | authentication code, with |
key material from HIP_TRANSFORM | | | | key material from |
| | | | HIP_TRANSFORM |
HMAC_2 65247 20 HMAC based message | | | | |
authentication code, with | HIP_SIGNATURE_2 | 65277 | variable | Signature of the R1 packet |
key material from HIP_TRANSFORM | | | | |
| HIP_SIGNATURE | 65279 | variable | Signature of the packet |
HIP_SIGNATURE_2 65277 variable Signature of the R1 packet | | | | |
| ECHO_REQUEST | 65281 | variable | Opaque data to be echoed |
HIP_SIGNATURE 65279 variable Signature of the packet | | | | back |
| | | | |
ECHO_REQUEST 65281 variable Opaque data to be echoed back | ECHO_RESPONSE | 65283 | variable | Opaque data echoed back; |
| | | | after signature |
ECHO_RESPONSE 65283 variable Opaque data echoed back; after +-----------------+-------+----------+------------------------------+
signature
6.2.1 TLV format 6.2.1 TLV format
The TLV encoded parameters are described in the following The TLV encoded parameters are described in the following
subsections. The type-field value also describes the order of these subsections. The type-field value also describes the order of these
fields in the packet. The parameters MUST be included into the fields in the packet, except for type values from 2048 to 4095 which
packet so that the types form an increasing order. If the order does are reserved for new transport forms. The parameters MUST be
not follow this rule, the packet is considered to be malformed and it included into the packet so that the types form an increasing order.
MUST be discarded. If the order does not follow this rule, the packet is considered to
be malformed and it MUST be discarded.
Parameters using type values from 2048 up to 4095 are transport
formats. Currently, one transport format is defined: the ESP
transport format [23]. The order of these parameters does not follow
the order of their type value, but they are put in the packet in
order of preference. First one of the transport formats it the most
preferred, and so on.
All the TLV parameters have a length (including Type and Length All the TLV parameters have a length (including Type and Length
fields) which is a multiple of 8 bytes. When needed, padding MUST be fields) which is a multiple of 8 bytes. When needed, padding MUST be
added to the end of the parameter so that the total length becomes a added to the end of the parameter so that the total length becomes a
multiple of 8 bytes. This rule ensures proper alignment of data. If multiple of 8 bytes. This rule ensures proper alignment of data. If
padding is added, the Length field MUST NOT include the padding. Any padding is added, the Length field MUST NOT include the padding. Any
added padding bytes MUST be set zero by the sender, but their content added padding bytes MUST be set zero by the sender, but their content
SHOULD NOT be checked on the receiving end. SHOULD NOT be checked on the receiving end.
Consequently, the Length field indicates the length of the Contents Consequently, the Length field indicates the length of the Contents
skipping to change at page 33, line 38 skipping to change at page 34, line 43
MUST be recognized by the recipient, zero otherwise. MUST be recognized by the recipient, zero otherwise.
The C bit is considered to be a part of the Type field. The C bit is considered to be a part of the Type field.
Consequently, critical parameters are always odd Consequently, critical parameters are always odd
and non-critical ones have an even value. and non-critical ones have an even value.
Length Length of the Contents, in bytes. Length Length of the Contents, in bytes.
Contents Parameter specific, defined by Type Contents Parameter specific, defined by Type
Padding Padding, 0-7 bytes, added if needed Padding Padding, 0-7 bytes, added if needed
Critical parameters MUST be recognized by the recipient. If a Critical parameters MUST be recognized by the recipient. If a
recipient encounters a critical parameter that it does not recognize, recipient encounters a critical parameter that it does not recognize,
it MUST NOT process the packet any further. it MUST NOT process the packet any further. It MAY send an ICMP or
NOTIFY, as defined in Section 4.4.
Non-critical parameters MAY be safely ignored. If a recipient Non-critical parameters MAY be safely ignored. If a recipient
encounters a non-critical parameter that it does not recognize, it encounters a non-critical parameter that it does not recognize, it
SHOULD proceed as if the parameter was not present in the received SHOULD proceed as if the parameter was not present in the received
packet. packet.
6.2.2 Defining new parameters 6.2.2 Defining new parameters
Future specifications may define new parameters as needed. When Future specifications may define new parameters as needed. When
defining new parameters, care must be taken to ensure that the defining new parameters, care must be taken to ensure that the
skipping to change at page 34, line 16 skipping to change at page 35, line 24
The following rules must be followed when defining new parameters. The following rules must be followed when defining new parameters.
1. The low order bit C of the Type code is used to distinguish 1. The low order bit C of the Type code is used to distinguish
between critical and non-critical parameters. between critical and non-critical parameters.
2. A new parameter may be critical only if an old recipient ignoring 2. A new parameter may be critical only if an old recipient ignoring
it would cause security problems. In general, new parameters it would cause security problems. In general, new parameters
SHOULD be defined as non-critical, and expect a reply from the SHOULD be defined as non-critical, and expect a reply from the
recipient. recipient.
3. If a system implements a new critical parameter, it MUST provide 3. If a system implements a new critical parameter, it MUST provide
the ability to configure the associated feature off, such that the ability to configure the associated feature off, such that
the critical parameter is not sent at all. The configuration the critical parameter is not sent at all. The configuration
option must be well documented. By default, sending of such a new option must be well documented. By default, sending of such a
critical parameter SHOULD be off. In other words, the management new critical parameter SHOULD be off. In other words, the
interface MUST allow vanilla standards only mode as a default management interface MUST allow vanilla standards-only mode as a
configuration setting, and MAY allow new critical payloads to be default configuration setting, and MAY allow new critical
configured on (and off). payloads to be configured on (and off).
4. The following type codes are reserved for future base protocol 4. The following type codes are reserved for future base protocol
extensions, and may be assigned only through an appropriate WG or extensions, and may be assigned only through an appropriate WG or
RFC action. RFC action.
0 - 511 0 - 511
65024 - 65535 65024 - 65535
5. The following type codes are reserved for experimentation and 5. The following type codes are reserved for experimentation and
private use. Types SHOULD be selected in a random fashion from private use. Types SHOULD be selected in a random fashion from
this range, thereby reducing the probability of collisions. A this range, thereby reducing the probability of collisions. A
method employing genuine randomness (such as flipping a coin) method employing genuine randomness (such as flipping a coin)
SHOULD be used. SHOULD be used.
32768 - 49141 32768 - 49141
6. All other parameter type codes MUST be registered by the IANA. 6. All other parameter type codes MUST be registered by the IANA.
See Section 14. See Section 13.
6.2.3 SPI
The SPI parameter contains the SPI that the receiving host must use
when sending data to the sending host. It may be possible, in future
extensions of this protocol, for multiple SPIs to exist in a
host-host communications context.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 1
Length 4
SPI Security Parameter Index
6.2.4 R1_COUNTER 6.2.3 R1_COUNTER
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved, 4 bytes | | Reserved, 4 bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| R1 generation counter, 8 bytes | | R1 generation counter, 8 bytes |
| | | |
skipping to change at page 35, line 33 skipping to change at page 36, line 32
The R1_COUNTER parameter contains an 64-bit unsigned integer in The R1_COUNTER parameter contains an 64-bit unsigned integer in
network byte order, indicating the current generation of valid network byte order, indicating the current generation of valid
puzzles. The sender is supposed to increment this counter puzzles. The sender is supposed to increment this counter
periodically. It is RECOMMENDED that the counter value is periodically. It is RECOMMENDED that the counter value is
incremented at least as often as old PUZZLE values are deprecated so incremented at least as often as old PUZZLE values are deprecated so
that SOLUTIONs to them are no longer accepted. that SOLUTIONs to them are no longer accepted.
The R1_COUNTER parameter is optional. It SHOULD be included in the The R1_COUNTER parameter is optional. It SHOULD be included in the
R1 (in which case it is covered by the signature), and if present in R1 (in which case it is covered by the signature), and if present in
the R1, it MAY be echoed (including the Reserved field) by the the R1, it MAY be echoed (including the Reserved field in verbatim)
Initiator in the I2. by the Initiator in the I2.
6.2.5 PUZZLE 6.2.4 PUZZLE
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| K, 1 byte | Lifetime | Opaque, 2 bytes | | K, 1 byte | Lifetime | Opaque, 2 bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Random # I, 8 bytes | | Random # I, 8 bytes |
| | | |
skipping to change at page 37, line 5 skipping to change at page 38, line 5
initiator which it should not exceed while trying to solve the initiator which it should not exceed while trying to solve the
puzzle. The lifetime is indicated as power of 2 using formula puzzle. The lifetime is indicated as power of 2 using formula
2^(Lifetime-32) seconds. A puzzle MAY be augmented by including an 2^(Lifetime-32) seconds. A puzzle MAY be augmented by including an
ECHO_REQUEST parameter to an R1. The contents of the ECHO_REQUEST ECHO_REQUEST parameter to an R1. The contents of the ECHO_REQUEST
are then echoed back in ECHO_RESPONSE, allowing the Responder to use are then echoed back in ECHO_RESPONSE, allowing the Responder to use
the included information as a part of puzzle processing. the included information as a part of puzzle processing.
The Opaque and Random #I field are not covered by the HIP_SIGNATURE_2 The Opaque and Random #I field are not covered by the HIP_SIGNATURE_2
parameter. parameter.
6.2.6 SOLUTION 6.2.5 SOLUTION
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| K, 1 byte | Reserved | Opaque, 2 bytes | | K, 1 byte | Reserved | Opaque, 2 bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Random #I, 8 bytes | | Random #I, 8 bytes |
| | | |
skipping to change at page 38, line 5 skipping to change at page 39, line 5
Puzzle solution Puzzle solution
#J random number #J random number
Random #I, and Random #J are represented as 64-bit integers, K as Random #I, and Random #J are represented as 64-bit integers, K as
8-bit integer, all in network byte order. 8-bit integer, all in network byte order.
The SOLUTION parameter contains a solution to a puzzle. It also The SOLUTION parameter contains a solution to a puzzle. It also
echoes back the random difficulty K, the Opaque field, and the puzzle echoes back the random difficulty K, the Opaque field, and the puzzle
integer #I. integer #I.
6.2.7 DIFFIE_HELLMAN 6.2.6 DIFFIE_HELLMAN
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group ID | Public Value / | Group ID | Public Value /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | padding | / | padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 38, line 41 skipping to change at page 39, line 41
8192-bit MODP group 6 8192-bit MODP group 6
The MODP Diffie-Hellman groups are defined in [18]. The OAKLEY group The MODP Diffie-Hellman groups are defined in [18]. The OAKLEY group
is defined in [9]. The OAKLEY well known group 5 is the same as the is defined in [9]. The OAKLEY well known group 5 is the same as the
1536-bit MODP group. 1536-bit MODP group.
A HIP implementation MUST support Group IDs 1 and 3. The 384-bit A HIP implementation MUST support Group IDs 1 and 3. The 384-bit
group can be used when lower security is enough (e.g. web surfing) group can be used when lower security is enough (e.g. web surfing)
and when the equipment is not powerful enough (e.g. some PDAs). and when the equipment is not powerful enough (e.g. some PDAs).
Equipment powerful enough SHOULD implement also group ID 5. The Equipment powerful enough SHOULD implement also group ID 5. The
384-bit group is defined in Appendix G. 384-bit group is defined in Appendix E.
To avoid unnecessary failures during the 4-way handshake, the rest of To avoid unnecessary failures during the base exchange, the rest of
the groups SHOULD be implemented in hosts where resources are the groups SHOULD be implemented in hosts where resources are
adequate. adequate.
6.2.8 HIP_TRANSFORM 6.2.7 HIP_TRANSFORM
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transform-ID #1 | Transform-ID #2 | | Transform-ID #1 | Transform-ID #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transform-ID #n | Padding | | Transform-ID #n | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 17 Type 17
Length length in octets, excluding Type, Length, and padding Length length in octets, excluding Type, Length, and padding
Transform-ID Defines the HIP Suite to be used Transform-ID Defines the HIP Suite to be used
The Suite-IDs are identical to those defined in Section 6.2.9. The following Suite-IDs are defined ([20],[24]):
There MUST NOT be more than six (6) HIP Suite-IDs in one HIP
transform TLV. The limited number of transforms sets the maximum
size of HIP_TRANSFORM TLV. The HIP_TRANSFORM TLV MUST contain at
least one of the mandatory Suite-IDs.
Mandatory implementations: ENCR-AES-CBC with HMAC-SHA1 and ENCR-NULL
with HMAC-SHA1.
6.2.9 ESP_TRANSFORM
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |E| Suite-ID #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Suite-ID #2 | Suite-ID #3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Suite-ID #n | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 19
Length length in octets, excluding Type, Length, and padding
E One if the ESP transform requires 64-bit sequence
numbers
(see
Section 11.6
)
Reserved zero when sent, ignored when received
Suite-ID defines the ESP Suite to be used
The following Suite-IDs are defined ([20],[23]): XXX: Deprecate MD5 in the light of recent development?
Suite-ID Value Suite-ID Value
RESERVED 0 RESERVED 0
ESP-AES-CBC with HMAC-SHA1 1 AES-CBC with HMAC-SHA1 1
ESP-3DES-CBC with HMAC-SHA1 2 3DES-CBC with HMAC-SHA1 2
ESP-3DES-CBC with HMAC-MD5 3 3DES-CBC with HMAC-MD5 3
ESP-BLOWFISH-CBC with HMAC-SHA1 4 BLOWFISH-CBC with HMAC-SHA1 4
ESP-NULL with HMAC-SHA1 5 NULL-ENCRYPT with HMAC-SHA1 5
ESP-NULL with HMAC-MD5 6 NULL-ENCRYPT with HMAC-MD5 6
There MUST NOT be more than six (6) ESP Suite-IDs in one There MUST NOT be more than six (6) HIP Suite-IDs in one HIP
ESP_TRANSFORM TLV. The limited number of Suite-IDs sets the maximum transform TLV. The limited number of transforms sets the maximum
size of ESP_TRANSFORM TLV. The ESP_TRANSFORM MUST contain at least size of HIP_TRANSFORM TLV. The HIP_TRANSFORM TLV MUST contain at
one of the mandatory Suite-IDs. least one of the mandatory Suite-IDs.
Mandatory implementations: ESP-AES-CBC with HMAC-SHA1 and ESP-NULL Mandatory implementations: AES-CBC with HMAC-SHA1 and NULL-ENCRYPTION
with HMAC-SHA1. with HMAC-SHA1.
6.2.10 HOST_ID 6.2.8 HOST_ID
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HI Length |DI-type| DI Length | | HI Length |DI-type| DI Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Host Identity / | Host Identity /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Domain Identifier / / | Domain Identifier /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Padding | / | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 35 Type 35
Length length in octets, excluding Type, Length, and Length length in octets, excluding Type, Length, and
Padding Padding
HI Length Length of the Host Identity in octets
DI-type type of the following Domain Identifier field DI-type type of the following Domain Identifier field
DI Length length of the FQDN or NAI in octets DI Length length of the FQDN or NAI in octets
N if set, the following FQDN/NAI field contains a
NAI
Host Identity actual host identity Host Identity actual host identity
Domain Identifier the identifier of the sender Domain Identifier the identifier of the sender
The Host Identity is represented in RFC2535 [12] format. The The Host Identity is represented in RFC2535 [12] format. The
algorithms used in RDATA format are the following: algorithms used in RDATA format are the following:
Algorithms Values Algorithms Values
RESERVED 0 RESERVED 0
DSA 3 [RFC2536] (RECOMMENDED) DSA 3 [RFC2536] (RECOMMENDED)
RSA 5 [RFC3110] (REQUIRED) RSA 5 [RFC3110] (REQUIRED)
The following DI-types have been defined: The following DI-types have been defined:
skipping to change at page 41, line 29 skipping to change at page 42, line 10
FQDN Fully Qualified Domain Name, in binary format. FQDN Fully Qualified Domain Name, in binary format.
NAI Network Access Identifier, in binary format. The NAI Network Access Identifier, in binary format. The
format of the NAI is login@FQDN. format of the NAI is login@FQDN.
The format for the FQDN is defined in RFC1035 [3] Section 3.1. The format for the FQDN is defined in RFC1035 [3] Section 3.1.
If there is no Domain Identifier, i.e. the DI-type field is zero, If there is no Domain Identifier, i.e. the DI-type field is zero,
also the DI Length field is set to zero. also the DI Length field is set to zero.
6.2.11 CERT 6.2.9 CERT
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cert count | Cert ID | Cert type | / | Cert count | Cert ID | Cert type | /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ Certificate / / Certificate /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 42, line 16 skipping to change at page 43, line 5
certificate chain. The numbering in Cert ID MUST go from 1 to Cert certificate chain. The numbering in Cert ID MUST go from 1 to Cert
count. count.
The following certificate types are defined: The following certificate types are defined:
Cert format Type number Cert format Type number
X.509 v3 1 X.509 v3 1
The encoding format for X.509v3 certificate is defined in [15]. The encoding format for X.509v3 certificate is defined in [15].
6.2.12 HMAC 6.2.10 HMAC
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| HMAC | | HMAC |
| | | |
| | | |
skipping to change at page 42, line 40 skipping to change at page 43, line 29
Type 65245 Type 65245
Length 20 Length 20
HMAC 160 low order bits of the HMAC computed over the HIP HMAC 160 low order bits of the HMAC computed over the HIP
packet, excluding the HMAC parameter and any packet, excluding the HMAC parameter and any
following HIP_SIGNATURE or HIP_SIGNATURE_2 following HIP_SIGNATURE or HIP_SIGNATURE_2
parameters. The checksum field MUST be set to zero parameters. The checksum field MUST be set to zero
and the HIP header length in the HIP common header and the HIP header length in the HIP common header
MUST be calculated not to cover any excluded MUST be calculated not to cover any excluded
parameters when the HMAC is calculated. parameters when the HMAC is calculated.
The HMAC calculation and verification process is presented in Section The HMAC calculation and verification process is presented in
8.3.1 Section 8.3.1
6.2.13 HMAC_2 6.2.11 HMAC_2
The TLV structure is the same as in Section 6.2.12. The fields are: The TLV structure is the same as in Section 6.2.10. The fields are:
Type 65247 Type 65247
Length 20 Length 20
HMAC 160 low order bits of the HMAC computed over the HIP HMAC 160 low order bits of the HMAC computed over the HIP
packet, excluding the HMAC parameter and any packet, excluding the HMAC parameter and any
following HIP_SIGNATURE or HIP_SIGNATURE_2 following HIP_SIGNATURE or HIP_SIGNATURE_2
parameters and including an additional sender's parameters and including an additional sender's
HOST_ID TLV during the HMAC calculation. The HOST_ID TLV during the HMAC calculation. The
checksum field MUST be set to zero and the HIP checksum field MUST be set to zero and the HIP
header length in the HIP common header MUST be header length in the HIP common header MUST be
calculated not to cover any excluded parameters when calculated not to cover any excluded parameters when
the HMAC is calculated. the HMAC is calculated.
The HMAC calculation and verification process is presented in Section The HMAC calculation and verification process is presented in
8.3.1 Section 8.3.1
6.2.14 HIP_SIGNATURE 6.2.12 HIP_SIGNATURE
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIG alg | Signature / | SIG alg | Signature /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Padding | / | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 43, line 43 skipping to change at page 44, line 28
Length length in octets, excluding Type, Length, and Padding Length length in octets, excluding Type, Length, and Padding
SIG alg Signature algorithm SIG alg Signature algorithm
Signature the signature is calculated over the HIP packet, Signature the signature is calculated over the HIP packet,
excluding the HIP_SIGNATURE TLV field and any TLVs excluding the HIP_SIGNATURE TLV field and any TLVs
that follow the HIP_SIGNATURE TLV. The checksum field that follow the HIP_SIGNATURE TLV. The checksum field
MUST be set to zero, and the HIP header length in the MUST be set to zero, and the HIP header length in the
HIP common header MUST be calculated only to the HIP common header MUST be calculated only to the
beginning of the HIP_SIGNATURE TLV when the signature beginning of the HIP_SIGNATURE TLV when the signature
is calculated. is calculated.
The signature algorithms are defined in Section 6.2.10. The The signature algorithms are defined in Section 6.2.8. The signature
signature in the Signature field is encoded using the proper method in the Signature field is encoded using the proper method depending
depending on the signature algorithm (e.g. according to [14] in case on the signature algorithm (e.g. according to [14] in case of RSA,
of RSA, or according to [13] in case of DSA). or according to [13] in case of DSA).
The HIP_SIGNATURE calculation and verification process is presented The HIP_SIGNATURE calculation and verification process is presented
in Section 8.3.2 in Section 8.3.2
6.2.15 HIP_SIGNATURE_2 6.2.13 HIP_SIGNATURE_2
The TLV structure is the same as in Section 6.2.14. The fields are: The TLV structure is the same as in Section 6.2.12. The fields are:
Type 65277 (2^16-2^8-3) Type 65277 (2^16-2^8-3)
Length length in octets, excluding Type, Length, and Padding Length length in octets, excluding Type, Length, and Padding
SIG alg Signature algorithm SIG alg Signature algorithm
Signature the signature is calculated over the HIP R1 packet, Signature the signature is calculated over the HIP R1 packet,
excluding the HIP_SIGNATURE_2 TLV field and any excluding the HIP_SIGNATURE_2 TLV field and any
TLVs that follow the HIP_SIGNATURE_2 TLV. Initiator's TLVs that follow the HIP_SIGNATURE_2 TLV. Initiator's
HIT, checksum field, and the Opaque and Random #I HIT, checksum field, and the Opaque and Random #I
fields in the PUZZLE TLV MUST be set to zero while fields in the PUZZLE TLV MUST be set to zero while
computing the HIP_SIGNATURE_2 signature. Further, the computing the HIP_SIGNATURE_2 signature. Further, the
HIP packet length in the HIP header MUST be HIP packet length in the HIP header MUST be
calculated to the beginning of the HIP_SIGNATURE_2 calculated to the beginning of the HIP_SIGNATURE_2
TLV when the signature is calculated. TLV when the signature is calculated.
Zeroing the Initiator's HIT makes it possible to create R1 packets Zeroing the Initiator's HIT makes it possible to create R1 packets
beforehand to minimize the effects of possible DoS attacks. Zeroing beforehand to minimize the effects of possible DoS attacks. Zeroing
the I and Opaque fields allows these fields to be populated the I and Opaque fields allows these fields to be populated
dynamically on precomputed R1s. dynamically on precomputed R1s.
Signature calculation and verification follows the process in Section Signature calculation and verification follows the process in
8.3.2. Section 8.3.2.
6.2.16 NES
During the life of an SA established by HIP, one of the hosts may
need to reset the Sequence Number to one (to prevent wrapping) and
rekey. The reason for rekeying might be an approaching sequence
number wrap in ESP, or a local policy on use of a key. Rekeying ends
the current SAs and starts new ones on both peers.
The NES parameter is carried in the HIP UPDATE packet. It is used to
reset Security Associations. It introduces a new SPI to be used when
sending data to the sender of the UPDATE packet. The keys for the
new Security Association will be drawn from KEYMAT. If the packet
contains a Diffie-Hellman parameter, the KEYMAT is first recomputed
before drawing the new keys.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Keymat Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Old SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 9
Length 12
Keymat Index Index, in bytes, where to continue to draw ESP keys
from KEYMAT. If the packet includes a new
Diffie-Hellman key, the field MUST be zero. Note
that the length of this field limits the amount of
keying material that can be drawn from KEYMAT. If
that amount is exceeded, the NES packet MUST contain
a new Diffie-Hellman key.
Old SPI Old SPI for data sent to the source address of
this packet
New SPI New SPI for data sent to the source address of
this packet
A host that receives an NES must reply shortly thereafter with an
NES. Any middleboxes between the communicating hosts will learn the
mappings from the pair of UPDATE messages.
6.2.17 SEQ 6.2.14 SEQ
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Update ID | | Update ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 11 Type 11
Length 4 Length 4
Update ID 32-bit sequence number Update ID 32-bit sequence number
The Update ID is an unsigned quantity, initialized by a host to zero The Update ID is an unsigned quantity, initialized by a host to zero
upon moving to ESTABLISHED state. The Update ID has scope within a upon moving to ESTABLISHED state. The Update ID has scope within a
single HIP association, and not across multiple associations or single HIP association, and not across multiple associations or
multiple hosts. The Update ID is incremented by one before each new multiple hosts. The Update ID is incremented by one before each new
UPDATE that is sent by the host (i.e., the first UPDATE packet UPDATE that is sent by the host (i.e., the first UPDATE packet
originated by a host has an Update ID of 1). originated by a host has an Update ID of 1).
6.2.18 ACK 6.2.15 ACK
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| peer Update ID | | peer Update ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 13 Type 13
Length variable (multiple of 4) Length variable (multiple of 4)
peer Update ID 32-bit sequence number corresponding to the peer Update ID 32-bit sequence number corresponding to the
Update ID being acked. Update ID being acked.
The ACK parameter includes one or more Update IDs that have been The ACK parameter includes one or more Update IDs that have been
received from the peer. The Length field identifies the number of received from the peer. The Length field identifies the number of
peer Update IDs that are present in the parameter. peer Update IDs that are present in the parameter.
6.2.19 ENCRYPTED 6.2.16 ENCRYPTED
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IV / | IV /
/ / / /
skipping to change at page 48, line 16 skipping to change at page 47, line 16
for that suite, but not any additional external padding). Note that for that suite, but not any additional external padding). Note that
the length of the cipher suite output may be smaller or larger than the length of the cipher suite output may be smaller or larger than
the length of the data to be encrypted, since the encryption process the length of the data to be encrypted, since the encryption process
may compress the data or add additional padding to the data. may compress the data or add additional padding to the data.
The ENCRYPTED payload may contain additional external padding, if the The ENCRYPTED payload may contain additional external padding, if the
result of encryption, the TLV header and the IV is not a multiple of result of encryption, the TLV header and the IV is not a multiple of
8 bytes. The contents of this external padding MUST follow the rules 8 bytes. The contents of this external padding MUST follow the rules
given in Section 6.2.1. given in Section 6.2.1.
6.2.20 NOTIFY 6.2.17 NOTIFY
The NOTIFY parameter is used to transmit informational data, such as The NOTIFY parameter is used to transmit informational data, such as
error conditions and state transitions, to a HIP peer. A NOTIFY error conditions and state transitions, to a HIP peer. A NOTIFY
parameter may appear in the NOTIFY packet type. The use of the parameter may appear in the NOTIFY packet type. The use of the
NOTIFY parameter in other packet types is for further study. NOTIFY parameter in other packet types is for further study.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
skipping to change at page 50, line 12 skipping to change at page 49, line 12
NO_HIP_PROPOSAL_CHOSEN 16 NO_HIP_PROPOSAL_CHOSEN 16
None of the proposed HIP Transform crypto suites was None of the proposed HIP Transform crypto suites was
acceptable. acceptable.
INVALID_HIP_TRANSFORM_CHOSEN 17 INVALID_HIP_TRANSFORM_CHOSEN 17
The HIP Transform crypto suite does not correspond to The HIP Transform crypto suite does not correspond to
one offered by the responder. one offered by the responder.
NO_ESP_PROPOSAL_CHOSEN 18
None of the proposed ESP Transform crypto suites was
acceptable.
INVALID_ESP_TRANSFORM_CHOSEN 19
The ESP Transform crypto suite does not correspond to
one offered by the responder.
AUTHENTICATION_FAILED 24 AUTHENTICATION_FAILED 24
Sent in response to a HIP signature failure. Sent in response to a HIP signature failure.
CHECKSUM_FAILED 26 CHECKSUM_FAILED 26
Sent in response to a HIP checksum failure. Sent in response to a HIP checksum failure.
HMAC_FAILED 28 HMAC_FAILED 28
skipping to change at page 51, line 25 skipping to change at page 50, line 15
the I2 for processing. The puzzle was correctly solved the I2 for processing. The puzzle was correctly solved
and the responder is willing to set up an association and the responder is willing to set up an association
but has currently a number of I2s in processing queue. but has currently a number of I2s in processing queue.
R2 will be sent after the I2 has been processed. R2 will be sent after the I2 has been processed.
NOTIFY MESSAGES - STATUS TYPES Value NOTIFY MESSAGES - STATUS TYPES Value
------------------------------ ----- ------------------------------ -----
(None defined at present) (None defined at present)
6.2.21 ECHO_REQUEST 6.2.18 ECHO_REQUEST
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque data (variable length) | | Opaque data (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 65281 or 1022 Type 65281 or 1022
skipping to change at page 52, line 5 skipping to change at page 51, line 5
The ECHO_REQUEST parameter contains an opaque blob of data that the The ECHO_REQUEST parameter contains an opaque blob of data that the
sender wants to get echoed back in the corresponding reply packet. sender wants to get echoed back in the corresponding reply packet.
The ECHO_REQUEST and ECHO_RESPONSE parameters MAY be used for any The ECHO_REQUEST and ECHO_RESPONSE parameters MAY be used for any
purpose where a node wants to carry some state in a request packet purpose where a node wants to carry some state in a request packet
and get it back in a response packet. The ECHO_REQUEST MAY be and get it back in a response packet. The ECHO_REQUEST MAY be
covered by the HMAC and SIGNATURE. This is dictated by the Type covered by the HMAC and SIGNATURE. This is dictated by the Type
field selected for the parameter; Type 1022 ECHO_REQUEST is covered field selected for the parameter; Type 1022 ECHO_REQUEST is covered
and Type 65281 is not. and Type 65281 is not.
6.2.22 ECHO_RESPONSE 6.2.19 ECHO_RESPONSE
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque data (variable length) | | Opaque data (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 65283 or 1024 Type 65283 or 1024
skipping to change at page 52, line 27 skipping to change at page 51, line 27
Opaque data Opaque data, copied unmodified from the ECHO_REQUEST Opaque data Opaque data, copied unmodified from the ECHO_REQUEST
parameter that triggered this response. parameter that triggered this response.
The ECHO_RESPONSE parameter contains an opaque blob of data that the The ECHO_RESPONSE parameter contains an opaque blob of data that the
sender of the ECHO_REQUEST wants to get echoed back. The opaque data sender of the ECHO_REQUEST wants to get echoed back. The opaque data
is copied unmodified from the ECHO_REQUEST parameter. is copied unmodified from the ECHO_REQUEST parameter.
The ECHO_REQUEST and ECHO_RESPONSE parameters MAY be used for any The ECHO_REQUEST and ECHO_RESPONSE parameters MAY be used for any
purpose where a node wants to carry some state in a request packet purpose where a node wants to carry some state in a request packet
and get it back in a response packet. The ECHO_RESPONSE MAY be and get it back in a response packet. The ECHO_RESPONSE MAY be
covered by the HMAC and SIGNATURE. This is dictated by the Type field covered by the HMAC and SIGNATURE. This is dictated by the Type
selected for the parameter; Type 1024 ECHO_RESPONSE is covered and field selected for the parameter; Type 1024 ECHO_RESPONSE is covered
Type 65283 is not. and Type 65283 is not.
6.3 ICMP messages 6.3 ICMP messages
When a HIP implementation detects a problem with an incoming packet, When a HIP implementation detects a problem with an incoming packet,
and it either cannot determine the identity of the sender of the and it either cannot determine the identity of the sender of the
packet or does not have any existing HIP security association with packet or does not have any existing HIP association with the sender
the sender of the packet, it MAY respond with an ICMP packet. Any of the packet, it MAY respond with an ICMP packet. Any such replies
such replies MUST be rate limited as described in [4]. In most MUST be rate limited as described in [4]. In most cases, the ICMP
cases, the ICMP packet will have the Parameter Problem type (12 for packet will have the Parameter Problem type (12 for ICMPv4, 4 for
ICMPv4, 4 for ICMPv6), with the Pointer field pointing to the field ICMPv6), with the Pointer field pointing to the field that caused the
that caused the ICMP message to be generated. ICMP message to be generated.
XXX: Should we say something more about rate limitation here?
6.3.1 Invalid Version 6.3.1 Invalid Version
If a HIP implementation receives a HIP packet that has an If a HIP implementation receives a HIP packet that has an
unrecognized HIP version number, it SHOULD respond, rate limited, unrecognized HIP version number, it SHOULD respond, rate limited,
with an ICMP packet with type Parameter Problem, the Pointer pointing with an ICMP packet with type Parameter Problem, the Pointer pointing
to the VER./RES. byte in the HIP header. to the VER./RES. byte in the HIP header.
6.3.2 Other problems with the HIP header and packet structure 6.3.2 Other problems with the HIP header and packet structure
If a HIP implementation receives a HIP packet that has other If a HIP implementation receives a HIP packet that has other
unrecoverable problems in the header or packet format, it MAY unrecoverable problems in the header or packet format, it MAY
respond, rate limited, with an ICMP packet with type Parameter respond, rate limited, with an ICMP packet with type Parameter
Problem, the Pointer pointing to the field that failed to pass the Problem, the Pointer pointing to the field that failed to pass the
format checks. However, an implementation MUST NOT send an ICMP format checks. However, an implementation MUST NOT send an ICMP
message if the Checksum fails; instead, it MUST silently drop the message if the Checksum fails; instead, it MUST silently drop the
packet. packet.
6.3.3 Unknown SPI 6.3.3 Invalid Cookie Solution
If a HIP implementation receives an ESP packet that has an
unrecognized SPI number, it MAY responder, rate limited, with an ICMP
packet with type Parameter Problem, the Pointer pointing to the the
beginning of SPI field in the ESP header.
6.3.4 Invalid Cookie Solution
If a HIP implementation receives an I2 packet that has an invalid If a HIP implementation receives an I2 packet that has an invalid
cookie solution, the behaviour depends on the underlying version of cookie solution, the behaviour depends on the underlying version of
IP. If IPv6 is used, the implementation SHOULD respond with an ICMP IP. If IPv6 is used, the implementation SHOULD respond with an ICMP
packet with type Parameter Problem, the Pointer pointing to the packet with type Parameter Problem, the Pointer pointing to the
beginning of the Puzzle solution #J field in the SOLUTION payload in beginning of the Puzzle solution #J field in the SOLUTION payload in
the HIP message. the HIP message.
If IPv4 is used, the implementation MAY respond with an ICMP packet If IPv4 is used, the implementation MAY respond with an ICMP packet
with the type Parameter Problem, copying enough of bytes form the I2 with the type Parameter Problem, copying enough of bytes form the I2
message so that the SOLUTION parameter fits in to the ICMP message, message so that the SOLUTION parameter fits in to the ICMP message,
the Pointer pointing to the beginning of the Puzzle solution #J the Pointer pointing to the beginning of the Puzzle solution #J
field, as in the IPv6 case. Note, however, that the resulting ICMPv4 field, as in the IPv6 case. Note, however, that the resulting ICMPv4
message exceeds the typical ICMPv4 message size as defined in [2]. message exceeds the typical ICMPv4 message size as defined in [2].
6.3.5 Non-existing HIP association 6.3.4 Non-existing HIP association
If a HIP implementation receives a CLOSE, or UPDATE packet, or any If a HIP implementation receives a CLOSE, or UPDATE packet, or any
other packet whose handling requires an existing association, that other packet whose handling requires an existing association, that
has either a Receiver or Sender HIT that does not match with any has either a Receiver or Sender HIT that does not match with any
existing HIP association, the implementation MAY respond, rate existing HIP association, the implementation MAY respond, rate
limited, with an ICMP packet with the type Parameter Problem, the limited, with an ICMP packet with the type Parameter Problem, the
Pointer pointing to the the beginning of the first HIT that does not Pointer pointing to the the beginning of the first HIT that does not
match. match.
A host MUST NOT reply with such an ICMP if it receives any of the A host MUST NOT reply with such an ICMP if it receives any of the
following messages: I1, R2, I2, R2, CER, and NOTIFY. When following messages: I1, R2, I2, R2, CER, and NOTIFY. When
introducing new packet types, a specification SHOULD define the introducing new packet types, a specification SHOULD define the
appropriate rules for sending or not sending this kind of ICMP appropriate rules for sending or not sending this kind of ICMP
replies. replies.
7. HIP Packets 7. HIP Packets
There are nine basic HIP packets. Four are for the base HIP There are nine basic HIP packets. Four are for the HIP base
exchange, one is for updating, one is a broadcast for use when there exchange, one is for updating, one is for sending certificates, one
is no IP addressing (e.g., before DHCP exchange), one is used to send for sending notifications, and two for closing a HIP association.
certificates, one for sending notifications, and one is for sending
unencrypted data.
Packets consist of the fixed header as described in Section 6.1, Packets consist of the fixed header as described in Section 6.1,
followed by the parameters. The parameter part, in turn, consists of followed by the parameters. The parameter part, in turn, consists of
zero or more TLV coded parameters. zero or more TLV coded parameters.
In addition to the base packets, other packets types will be defined In addition to the base packets, other packets types will be defined
later in separate specifications. For example, support for mobility later in separate specifications. For example, support for mobility
and multi-homing is not included in this specification. and multi-homing is not included in this specification.
Packet representation uses the following operations: Packet representation uses the following operations:
skipping to change at page 55, line 29 skipping to change at page 54, line 27
Header: Header:
Packet Type = 2 Packet Type = 2
SRC HIT = Responder's HIT SRC HIT = Responder's HIT
DST HIT = Initiator's HIT DST HIT = Initiator's HIT
IP ( HIP ( [ R1_COUNTER, ] IP ( HIP ( [ R1_COUNTER, ]
PUZZLE, PUZZLE,
DIFFIE_HELLMAN, DIFFIE_HELLMAN,
HIP_TRANSFORM, HIP_TRANSFORM,
ESP_TRANSFORM,
HOST_ID, HOST_ID,
[ ECHO_REQUEST, ] [ ECHO_REQUEST, ]
HIP_SIGNATURE_2 ) HIP_SIGNATURE_2 )
[, ECHO_REQUEST ]) [, ECHO_REQUEST ])
Valid control bits: C, A Valid control bits: C, A
The R1 packet may be followed by one or more CER packets. In this The R1 packet may be followed by one or more CER packets. In this
case, the C-bit in the control field MUST be set. case, the C-bit in the control field MUST be set.
skipping to change at page 56, line 25 skipping to change at page 55, line 21
time, for example, 15 minutes. By using a small number of different time, for example, 15 minutes. By using a small number of different
Cookies for a given Diffie-Hellman value, the R1 packets can be Cookies for a given Diffie-Hellman value, the R1 packets can be
pre-computed and delivered as quickly as I1 packets arrive. A pre-computed and delivered as quickly as I1 packets arrive. A
scavenger process should clean up unused DHs and Cookies. scavenger process should clean up unused DHs and Cookies.
The HIP_TRANSFORM contains the encryption and integrity algorithms The HIP_TRANSFORM contains the encryption and integrity algorithms
supported by the Responder to protect the HI exchange, in the order supported by the Responder to protect the HI exchange, in the order
of preference. All implementations MUST support the AES [10] with of preference. All implementations MUST support the AES [10] with
HMAC-SHA-1-96 [6]. HMAC-SHA-1-96 [6].
The ESP_TRANSFORM contains the ESP modes supported by the Responder,
in the order of preference. All implementations MUST support AES
[10] with HMAC-SHA-1-96 [6].
The ECHO_REQUEST contains data that the sender wants to receive The ECHO_REQUEST contains data that the sender wants to receive
unmodified in the corresponding response packet in the ECHO_RESPONSE unmodified in the corresponding response packet in the ECHO_RESPONSE
parameter. The ECHO_REQUEST can be either covered by the signature, parameter. The ECHO_REQUEST can be either covered by the signature,
or it can be left out from it. In the first case, the ECHO_REQUEST or it can be left out from it. In the first case, the ECHO_REQUEST
gets Type number 1022 and in the latter case 65281. gets Type number 1022 and in the latter case 65281.
The signature is calculated over the whole HIP envelope, after The signature is calculated over the whole HIP envelope, after
setting the initiator HIT, header checksum as well as the Opaque setting the initiator HIT, header checksum as well as the Opaque
field and the Random #I in the PUZZLE parameter temporarily to zero, field and the Random #I in the PUZZLE parameter temporarily to zero,
and excluding any TLVs that follow the signature, as described in and excluding any TLVs that follow the signature, as described in
Section 6.2.15. This allows the Responder to use precomputed R1s. Section 6.2.13. This allows the Responder to use precomputed R1s.
The Initiator SHOULD validate this signature. It SHOULD check that The Initiator SHOULD validate this signature. It SHOULD check that
the responder HI received matches with the one expected, if any. the responder HI received matches with the one expected, if any.
7.3 I2 - the second HIP initiator packet 7.3 I2 - the second HIP initiator packet
The HIP header values for the I2 packet: The HIP header values for the I2 packet:
Header: Header:
Type = 3 Type = 3
SRC HIT = Initiator's HIT SRC HIT = Initiator's HIT
DST HIT = Responder's HIT DST HIT = Responder's HIT
IP ( HIP ( SPI, IP ( HIP ( [R1_COUNTER,]
[R1_COUNTER,]
SOLUTION, SOLUTION,
DIFFIE_HELLMAN, DIFFIE_HELLMAN,
HIP_TRANSFORM, HIP_TRANSFORM,
ESP_TRANSFORM,
ENCRYPTED { HOST_ID }, ENCRYPTED { HOST_ID },
[ ECHO_RESPONSE ,] [ ECHO_RESPONSE ,]
HMAC, HMAC,
HIP_SIGNATURE HIP_SIGNATURE
[, ECHO_RESPONSE] ) ) [, ECHO_RESPONSE] ) )
Valid control bits: C, A Valid control bits: C, A
The HITs used MUST match the ones used previously. The HITs used MUST match the ones used previously.
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process should clean up unused DHs. process should clean up unused DHs.
The HIP_TRANSFORM contains the encryption and integrity used to The HIP_TRANSFORM contains the encryption and integrity used to
protect the HI exchange selected by the Initiator. All protect the HI exchange selected by the Initiator. All
implementations MUST support the AES transform [10]. implementations MUST support the AES transform [10].
The Initiator's HI is encrypted using the HIP_TRANSFORM encryption The Initiator's HI is encrypted using the HIP_TRANSFORM encryption
algorithm. The keying material is derived from the Diffie-Hellman algorithm. The keying material is derived from the Diffie-Hellman
exchanged as defined in Section 9. exchanged as defined in Section 9.
The ESP_TRANSFORM contains the ESP mode selected by the Initiator.
All implementations MUST support AES [10] with HMAC-SHA-1-96 [6].
The ECHO_RESPONSE contains the the unmodified Opaque data copied from The ECHO_RESPONSE contains the the unmodified Opaque data copied from
the corresponding ECHO_REQUEST TLV. The ECHO_RESPONSE can be either the corresponding ECHO_REQUEST TLV. The ECHO_RESPONSE can be either
covered by the signature, or it can be left out from it. In the covered by the signature, or it can be left out from it. In the
first case, the ECHO_RESPONSE gets Type number 1024 and in the latter first case, the ECHO_RESPONSE gets Type number 1024 and in the latter
case 65283. case 65283.
The HMAC is calculated over whole HIP envelope, excluding any TLVs The HMAC is calculated over whole HIP envelope, excluding any TLVs
after the HMAC, as described in Section 8.3.1. The Responder MUST after the HMAC, as described in Section 8.3.1. The Responder MUST
validate the HMAC. validate the HMAC.
The signature is calculated over whole HIP envelope, excluding any The signature is calculated over whole HIP envelope, excluding any
TLVs after the HIP_SIGNATURE, as described in Section 6.2.14. The TLVs after the HIP_SIGNATURE, as described in Section 6.2.12. The
Responder MUST validate this signature. It MAY use either the HI in Responder MUST validate this signature. It MAY use either the HI in
the packet or the HI acquired by some other means. the packet or the HI acquired by some other means.
7.4 R2 - the second HIP responder packet 7.4 R2 - the second HIP responder packet
The HIP header values for the R2 packet: The HIP header values for the R2 packet:
Header: Header:
Packet Type = 4 Packet Type = 4
SRC HIT = Responder's HIT SRC HIT = Responder's HIT
DST HIT = Initiator's HIT DST HIT = Initiator's HIT
IP ( HIP ( HMAC_2, HIP_SIGNATURE ) )
IP ( HIP ( SPI, HMAC_2, HIP_SIGNATURE ) )
Valid control bits: none Valid control bits: none
The HMAC_2 is calculated over whole HIP envelope, with Responder's The HMAC_2 is calculated over whole HIP envelope, with Responder's
HOST_ID TLV concatenated with the HIP envelope. The HOST_ID TLV is HOST_ID TLV concatenated with the HIP envelope. The HOST_ID TLV is
removed after the HMAC calculation. The procedure is described in removed after the HMAC calculation. The procedure is described in
8.3.1. 8.3.1.
The signature is calculated over whole HIP envelope. The signature is calculated over whole HIP envelope.
skipping to change at page 59, line 23 skipping to change at page 58, line 10
Support for the UPDATE packet is MANDATORY. Support for the UPDATE packet is MANDATORY.
The HIP header values for the UPDATE packet: The HIP header values for the UPDATE packet:
Header: Header:
Packet Type = 6 Packet Type = 6
SRC HIT = Sender's HIT SRC HIT = Sender's HIT
DST HIT = Recipient's HIT DST HIT = Recipient's HIT
IP ( HIP ( [NES, SEQ, ACK, DIFFIE_HELLMAN, ] HMAC, HIP_SIGNATURE ) ) IP ( HIP ( [SEQ, ACK, ] HMAC, HIP_SIGNATURE ) )
Valid control bits: None Valid control bits: None
The UPDATE packet contains mandatory HMAC and HIP_SIGNATURE The UPDATE packet contains mandatory HMAC and HIP_SIGNATURE
parameters, and other optional parameters. parameters, and other optional parameters.
The UPDATE packet contains zero or one SEQ parameter. The presence The UPDATE packet contains zero or one SEQ parameter. The presence
of a SEQ parameter indicates that the receiver MUST ack the UPDATE. of a SEQ parameter indicates that the receiver MUST ack the UPDATE.
An UPDATE that does not contain a SEQ parameter is simply an ACK of a An UPDATE that does not contain a SEQ parameter is simply an ACK of a
previous UPDATE and itself MUST not be acked. previous UPDATE and itself MUST not be acked.
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A sender MAY choose to forego reliable transmission of a particular A sender MAY choose to forego reliable transmission of a particular
UPDATE (e.g., it becomes overcome by events). The semantics are such UPDATE (e.g., it becomes overcome by events). The semantics are such
that the receiver MUST acknowledge the UPDATE but the sender MAY that the receiver MUST acknowledge the UPDATE but the sender MAY
choose to not care about receiving the ACK. choose to not care about receiving the ACK.
UPDATEs MAY be retransmitting without incrementing SEQ. If the same UPDATEs MAY be retransmitting without incrementing SEQ. If the same
subset of parameters is included in multiple UPDATEs with different subset of parameters is included in multiple UPDATEs with different
SEQs, the host MUST ensure that receiver processing of the parameters SEQs, the host MUST ensure that receiver processing of the parameters
multiple times will not result in a protocol error. multiple times will not result in a protocol error.
In the case of rekeying (Section 8.10), the UPDATE packet MUST carry
NES and MAY carry DIFFIE_HELLMAN parameter, unless the UPDATE is a
bare ack.
Intermediate systems that use the SPI will have to inspect HIP
packets for a UPDATE packet. The packet is signed for the benefit of
the intermediate systems. Since intermediate systems may need the
new SPI values, the contents of this packet cannot be encrypted.
7.7 NOTIFY - the HIP Notify Packet 7.7 NOTIFY - the HIP Notify Packet
The NOTIFY packet is OPTIONAL. The NOTIFY packet MAY be used to The NOTIFY packet is OPTIONAL. The NOTIFY packet MAY be used to
provide information to a peer. Typically, NOTIFY is used to indicate provide information to a peer. Typically, NOTIFY is used to indicate
some type of protocol error or negotiation failure. some type of protocol error or negotiation failure.
The HIP header values for the NOTIFY packet: The HIP header values for the NOTIFY packet:
Header: Header:
Packet Type = 7 Packet Type = 7
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7.8 CLOSE - the HIP association closing packet 7.8 CLOSE - the HIP association closing packet
The HIP header values for the CLOSE packet: The HIP header values for the CLOSE packet:
Header: Header:
Packet Type = 8 Packet Type = 8
SRC HIT = Sender's HIT SRC HIT = Sender's HIT
DST HIT = Recipient's HIT DST HIT = Recipient's HIT
IP ( HIP ( ECHO_REQUEST, HMAC, HIP_SIGNATURE ) ) IP ( HIP ( ECHO_REQUEST, HMAC, HIP_SIGNATURE ) )
Valid control bits: none Valid control bits: none
The sender MUST include an ECHO_REPLY used to validate CLOSE_ACK The sender MUST include an ECHO_REQUEST used to validate CLOSE_ACK
received in response, and both an HMAC and a signature (calculated received in response, and both an HMAC and a signature (calculated
over the whole HIP envelope). over the whole HIP envelope).
The receiver peer MUST validate both the HMAC and the signature if it The receiver peer MUST validate both the HMAC and the signature if it
has a HIP association state, and MUST reply with a CLOSE_ACK has a HIP association state, and MUST reply with a CLOSE_ACK
containing an ECHO_REPLY corresponding to the received ECHO_REQUEST. containing an ECHO_REPLY corresponding to the received ECHO_REQUEST.
7.9 CLOSE_ACK - the HIP closing acknowledgment packet 7.9 CLOSE_ACK - the HIP closing acknowledgment packet
The HIP header values for the CLOSE_ACK packet: The HIP header values for the CLOSE_ACK packet:
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8. Packet processing 8. Packet processing
Each host is assumed to have a single HIP protocol implementation Each host is assumed to have a single HIP protocol implementation
that manages the host's HIP associations and handles requests for new that manages the host's HIP associations and handles requests for new
ones. Each HIP association is governed by a conceptual state ones. Each HIP association is governed by a conceptual state
machine, with states defined above in Section 5.4. The HIP machine, with states defined above in Section 5.4. The HIP
implementation can simultaneously maintain HIP associations with more implementation can simultaneously maintain HIP associations with more
than one host. Furthermore, the HIP implementation may have more than one host. Furthermore, the HIP implementation may have more
than one active HIP association with another host; in this case, HIP than one active HIP association with another host; in this case, HIP
associations are distinguished by their respective HITs and IPsec associations are distinguished by their respective HITs. It is not
SPIs. It is not possible to have more than one HIP associations possible to have more than one HIP associations between any given
between any given pair of HITs. Consequently, the only way for two pair of HITs. Consequently, the only way for two hosts to have more
hosts to have more than one parallel association is to use different than one parallel association is to use different HITs, at least at
HITs, at least at one end. one end.
The processing of packets depends on the state of the HIP The processing of packets depends on the state of the HIP
association(s) with respect to the authenticated or apparent association(s) with respect to the authenticated or apparent
originator of the packet. A HIP implementation determines whether it originator of the packet. A HIP implementation determines whether it
has an active association with the originator of the packet based on has an active association with the originator of the packet based on
the HITs or the SPI of the packet. the HITs. In the case of user data carried in a specific transport
format, the transport format document specifies how the incoming
packets are matched with the active associations.
8.1 Processing outgoing application data 8.1 Processing outgoing application data
In a HIP host, an application can send application level data using In a HIP host, an application can send application level data using
HITs or LSIs as source and destination identifiers. The HITs and HITs or LSIs as source and destination identifiers. The HITs and
LSIs may be specified via a backwards compatible API (see Appendix A) LSIs may be specified via a backwards compatible API (see [29]) or a
or a completely new API. However, whenever there is such outgoing completely new API. The exact format and method for transferring the
data, the stack has to protect the data with ESP, and send the data from the source HIP host to the destination HIP host is defined
resulting datagram using appropriate source and destination IP in the corresponding transport format document. The actual data is
addresses. Here, we specify the processing rules only for the base transmitted in the network using the appropriate source and
case where both hosts have only single usable IP addresses; the destination IP addresses. Here, we specify the processing rules only
multi-address multi-homing case will be specified separately. for the base case where both hosts have only single usable IP
addresses; the multi-address multi-homing case will be specified
separately.
If the IPv4 or IPv6 backward compatible APIs and therefore LSIs are If the IPv4 or IPv6 backward compatible APIs and therefore LSIs are
supported, it is assumed that the LSIs will be converted into proper supported, it is assumed that the LSIs will be converted into proper
HITs somewhere in the stack. The exact location of the conversion is HITs somewhere in the stack. The exact location of the conversion is
an implementation specific issue and not discussed here. The an implementation specific issue and not discussed here. The
following conceptual algorithm discusses only HITs, with the following conceptual algorithm discusses only HITs, with the
assumption that the LSI-to-HIT conversion takes place somewhere. assumption that the LSI-to-HIT conversion takes place somewhere.
The following steps define the conceptual processing rules for The following steps define the conceptual processing rules for
outgoing datagrams destined to a HIT. outgoing datagrams destined to a HIT.
1. If the datagram has a specified source address, it MUST be a HIT. 1. If the datagram has a specified source address, it MUST be a HIT.
If it is not, the implementation MAY replace the source address If it is not, the implementation MAY replace the source address
with a HIT. Otherwise it MUST drop the packet. with a HIT. Otherwise it MUST drop the packet.
2. If the datagram has an unspecified source address, the 2. If the datagram has an unspecified source address, the
implementation must choose a suitable source HIT for the implementation must choose a suitable source HIT for the
datagram. In selecting a proper local HIT, the implementation datagram. In selecting a proper local HIT, the implementation
SHOULD consult the table of currently active HIP sessions, and SHOULD consult the table of currently active HIP sessions, and
preferably select a HIT that already has an active session with preferably select a HIT that already has an active session with
the target HIT. the target HIT.
3. If there no active HIP session with the given < source, 3. If there is no active HIP session with the given < source,
destination > HIT pair, one must be created by running the base destination > HIT pair, one must be created by running the base
exchange. The implementation SHOULD queue at least one packet exchange. The implementation SHOULD queue at least one packet
per HIP session to be formed, and it MAY queue more than one. per HIP session to be formed, and it MAY queue more than one.
4. Once there is an active HIP session for the given < source, 4. Once there is an active HIP session for the given < source,
destination > HIT pair, the outgoing datagram is protected using destination > HIT pair, the outgoing datagram is passed to
the associated ESP security association. In a typical transport handling. The possible transport formats are defined
implementation, this will result in an transport mode ESP in separate documents, of which the ESP transport format for HIP
datagram that still has HITs in the place of IP addresses. is mandatory for all HIP implementations.
5. The HITs in the datagram are replaced with suitable IP addresses. 5. The HITs in the datagram are replaced with suitable IP addresses.
For IPv6, the rules defined in [16] SHOULD be followed. Note For IPv6, the rules defined in [16] SHOULD be followed. Note
that this HIT-to-IP-address conversion step MAY also be performed that this HIT-to-IP-address conversion step MAY also be performed
at some other point in the stack, e.g., before ESP processing. at some other point in the stack, e.g., before wrapping the
However, care must be taken to make sure that the right ESP SA is packet into the output format.
employed.
8.2 Processing incoming application data 8.2 Processing incoming application data
Incoming HIP datagrams arrive as ESP protected packets. In the usual The transport format and method (defined in separate specifications)
case the receiving host has a corresponding ESP security association, determines the format in which incoming HIP packets arrive to the
identified by the SPI and destination IP address in the packet. host. The following steps define the conceptual processing rules for
However, if the host has crashed or otherwise lost its HIP state, it incoming datagrams. The specific transport format and method
may not have such an SA. specifications define in more detail the packet processing, related
to the method.
The following steps define the conceptual processing rules for 1. The incoming datagram is mapped to an existing HIP association,
incoming ESP protected datagrams targeted to an ESP security typically using some information from the packet. For example,
association created with HIP. such mapping may be based on IPsec Security Parameter Index (SPI)
1. Detect the proper IPsec SA using the SPI. If the resulting SA is or a protocol port number.
a non-HIP ESP SA, process the packet according to standard IPsec 2. The specific transport format is unwrapped, in a way depending on
rules. If there are no SAs identified with the SPI, the host MAY the transport format, yielding a packet that looks like a
send an ICMP packet as defined in Section 6.3.3. How to handle standard (unencrypted) IP packet. If possible, this step SHOULD
lost state is an implementation issue. also verify that the packet was indeed (once) sent by the remote
2. If a proper HIP ESP SA is found, the packet is processed normally HIP host, as identified by the HIP association.
by ESP, as if the packet were a transport mode packet. The
packet may be dropped by ESP, as usual. In a typical
implementation, the result of successful ESP decryption and
verification is a datagram with the original IP addresses as
source and destination.
3. The IP addresses in the datagram are replaced with the HITs 3. The IP addresses in the datagram are replaced with the HITs
associated with the ESP SA. Note that this IP-address-to-HIT associated with the HIP association. Note that this
conversion step MAY also be performed at some other point in the IP-address-to-HIT conversion step MAY also be performed at some
stack, e.g., before ESP processing. other point in the stack.
4. The datagram is delivered to the upper layer. Demultiplexing the 4. The datagram is delivered to the upper layer. Demultiplexing the
datagram the right upper layer socket is based on the HITs (or datagram the right upper layer socket is based on the HITs (or
LSIs). LSIs).
8.3 HMAC and SIGNATURE calculation and verification 8.3 HMAC and SIGNATURE calculation and verification
The following subsections define the actions for processing HMAC, The following subsections define the actions for processing HMAC,
HIP_SIGNATURE and HIP_SIGNATURE_2 TLVs. HIP_SIGNATURE and HIP_SIGNATURE_2 TLVs.
8.3.1 HMAC calculation 8.3.1 HMAC calculation
The following process applies both to the HMAC and HMAC_2 TLVs. When The following process applies both to the HMAC and HMAC_2 TLVs. When
processing HMAC_2, the difference is that the HMAC calculation processing HMAC_2, the difference is that the HMAC calculation
includes pseudo HOST_ID field containing the Responder's information includes pseudo HOST_ID field containing the Responder's information
as sent in the R1 packet earlier. as sent in the R1 packet earlier.
The HMAC TLV is defined in Section 6.2.12 and HMAC_2 TLV in Section The HMAC TLV is defined in Section 6.2.10 and HMAC_2 TLV in
6.2.13. HMAC calculation and verification process: Section 6.2.11. HMAC calculation and verification process:
Packet sender: Packet sender:
1. Create the HIP packet, without the HMAC or any possible 1. Create the HIP packet, without the HMAC or any possible
HIP_SIGNATURE or HIP_SIGNATURE_2 TLVs. HIP_SIGNATURE or HIP_SIGNATURE_2 TLVs.
2. In case of HMAC_2 calculation, add a HOST_ID (Responder) TLV to 2. In case of HMAC_2 calculation, add a HOST_ID (Responder) TLV to
the packet. the packet.
3. Calculate the Length field in the HIP header. 3. Calculate the Length field in the HIP header.
4. Compute the HMAC. 4. Compute the HMAC.
5. In case of HMAC_2, remove the HOST_ID TLV from the packet. 5. In case of HMAC_2, remove the HOST_ID TLV from the packet.
6. Add the HMAC TLV to the packet and any HIP_SIGNATURE or 6. Add the HMAC TLV to the packet and any HIP_SIGNATURE or
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6. In case of HMAC_2, remove the HOST_ID TLV from the packet before 6. In case of HMAC_2, remove the HOST_ID TLV from the packet before
further processing. further processing.
8.3.2 Signature calculation 8.3.2 Signature calculation
The following process applies both to the HIP_SIGNATURE and The following process applies both to the HIP_SIGNATURE and
HIP_SIGNATURE_2 TLVs. When processing HIP_SIGNATURE_2, the only HIP_SIGNATURE_2 TLVs. When processing HIP_SIGNATURE_2, the only
difference is that instead of HIP_SIGNATURE TLV, the HIP_SIGNATURE_2 difference is that instead of HIP_SIGNATURE TLV, the HIP_SIGNATURE_2
TLV is used, and the Initiator's HIT and PUZZLE Opaque and Random #I TLV is used, and the Initiator's HIT and PUZZLE Opaque and Random #I
fields are cleared (set to all zeros) before computing the signature. fields are cleared (set to all zeros) before computing the signature.
The HIP_SIGNATURE TLV is defined in Section 6.2.14 and the The HIP_SIGNATURE TLV is defined in Section 6.2.12 and the
HIP_SIGNATURE_2 TLV in Section 6.2.15. HIP_SIGNATURE_2 TLV in Section 6.2.13.
Signature calculation and verification process: Signature calculation and verification process:
Packet sender: Packet sender:
1. Create the HIP packet without the HIP_SIGNATURE TLV or any TLVs 1. Create the HIP packet without the HIP_SIGNATURE TLV or any TLVs
that follow the HIP_SIGNATURE TLV. that follow the HIP_SIGNATURE TLV.
2. Calculate the Length field in the HIP header. 2. Calculate the Length field in the HIP header.
3. Compute the signature. 3. Compute the signature.
4. Add the HIP_SIGNATURE TLV to the packet. 4. Add the HIP_SIGNATURE TLV to the packet.
5. Add any TLVs that follow the HIP_SIGNATURE TLV. 5. Add any TLVs that follow the HIP_SIGNATURE TLV.
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address that corresponds to the peer host. The IP address of the address that corresponds to the peer host. The IP address of the
peer host may be obtained via conventional mechanisms, such as DNS peer host may be obtained via conventional mechanisms, such as DNS
lookup. The I1 contents are specified in Section 7.1. The selection lookup. The I1 contents are specified in Section 7.1. The selection
of which host identity to use, if a host has more than one to choose of which host identity to use, if a host has more than one to choose
from, is typically a policy decision. from, is typically a policy decision.
The following steps define the conceptual processing rules for The following steps define the conceptual processing rules for
initiating a HIP exchange: initiating a HIP exchange:
1. The Initiator gets the Responder's HIT and one or more addresses 1. The Initiator gets the Responder's HIT and one or more addresses
either from a DNS lookup of the responder's FQDN, from some other either from a DNS lookup of the responder's FQDN, from some other
repository, or from a local table. If the initiator does not know repository, or from a local table. If the initiator does not
the responder's HIT, it may attempt opportunistic mode by using know the responder's HIT, it may attempt opportunistic mode by
NULL (all zeros) as the responder's HIT. using NULL (all zeros) as the responder's HIT.
2. The Initiator sends an I1 to one of the Responder's addresses. 2. The Initiator sends an I1 to one of the Responder's addresses.
The selection of which address to use is a local policy decision. The selection of which address to use is a local policy decision.
3. Upon sending an I1, the sender shall transition to state I1-SENT, 3. Upon sending an I1, the sender shall transition to state I1-SENT,
start a timer whose timeout value should be larger than the start a timer whose timeout value should be larger than the
worst-case anticipated RTT, and shall increment a timeout counter worst-case anticipated RTT, and shall increment a timeout counter
associated with the I1. associated with the I1.
4. Upon timeout, the sender SHOULD retransmit the I1 and restart the 4. Upon timeout, the sender SHOULD retransmit the I1 and restart the
timer, up to a maximum of I1_RETRIES_MAX tries. timer, up to a maximum of I1_RETRIES_MAX tries.
8.4.1 Sending multiple I1s in parallel 8.4.1 Sending multiple I1s in parallel
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the HITs in the R1). If so, it should process the R1 as the HITs in the R1). If so, it should process the R1 as
described below. described below.
2. Otherwise, if the system is in any other state than I1-SENT or 2. Otherwise, if the system is in any other state than I1-SENT or
I2-SENT with respect to the HITs included in the R1, it SHOULD I2-SENT with respect to the HITs included in the R1, it SHOULD
silently drop the R1 and remain in the current state. silently drop the R1 and remain in the current state.
3. If the HIP association state is I1-SENT or I2-SENT, the received 3. If the HIP association state is I1-SENT or I2-SENT, the received
Initiator's HIT MUST correspond to the HIT used in the original, Initiator's HIT MUST correspond to the HIT used in the original,
I1 and the Responder's HIT MUST correspond to the one used, I1 and the Responder's HIT MUST correspond to the one used,
unless the I1 contained a NULL HIT. unless the I1 contained a NULL HIT.
4. The system SHOULD validate the R1 signature before applying 4. The system SHOULD validate the R1 signature before applying
further packet processing, according to Section 6.2.15. further packet processing, according to Section 6.2.13.
5. If the HIP association state is I1-SENT, and multiple valid R1s 5. If the HIP association state is I1-SENT, and multiple valid R1s
are present, the system SHOULD select from among the R1s with are present, the system SHOULD select from among the R1s with
the largest R1 generation counter. the largest R1 generation counter.
6. If the HIP association state is I2-SENT, the system MAY reenter 6. If the HIP association state is I2-SENT, the system MAY reenter
state I1-SENT and process the received R1 if it has a larger R1 state I1-SENT and process the received R1 if it has a larger R1
generation counter than the R1 responded to previously. generation counter than the R1 responded to previously.
7. The R1 packet may have the C bit set -- in this case, the system 7. The R1 packet may have the C bit set -- in this case, the system
should anticipate the receipt of HIP CER packets that contain should anticipate the receipt of HIP CER packets that contain
the host identity corresponding to the responder's HIT. the host identity corresponding to the responder's HIT.
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lifetime of the puzzle. If the cookie puzzle is not lifetime of the puzzle. If the cookie puzzle is not
successfully solved, the implementation may either resend I1 successfully solved, the implementation may either resend I1
within the retry bounds or abandon the HIP exchange. within the retry bounds or abandon the HIP exchange.
12. The system computes standard Diffie-Hellman keying material 12. The system computes standard Diffie-Hellman keying material
according to the public value and Group ID provided in the according to the public value and Group ID provided in the
DIFFIE_HELLMAN parameter. The Diffie-Hellman keying material DIFFIE_HELLMAN parameter. The Diffie-Hellman keying material
Kij is used for key extraction as specified in Section 9. If Kij is used for key extraction as specified in Section 9. If
the received Diffie-Hellman Group ID is not supported, the the received Diffie-Hellman Group ID is not supported, the
implementation may either resend I1 within the retry bounds or implementation may either resend I1 within the retry bounds or
abandon the HIP exchange. abandon the HIP exchange.
13. The system selects the HIP transform and ESP transform from the 13. The system selects the HIP transform from the choices presented
choices presented in the R1 packet and uses the selected values in the R1 packet and uses the selected values subsequently when
subsequently when generating and using encryption keys, and when generating and using encryption keys, and when sending the I2.
sending the I2. If the proposed alternatives are not acceptable If the proposed alternatives are not acceptable to the system,
to the system, it may either resend I1 within the retry bounds it may either resend I1 within the retry bounds or abandon the
or abandon the HIP exchange. HIP exchange.
14. The system prepares and creates an incoming IPsec ESP security 14. The system initialized the remaining variables in the associated
association. It may also prepare a security association for
outgoing traffic, but since it does not have the correct SPI
value yet, it cannot activate it.
15. The system initialized the remaining variables in the associated
state, including Update ID counters. state, including Update ID counters.
16. The system prepares and sends an I2, as described in Section 15. The system prepares and sends an I2, as described in
7.3. Section 7.3.
17. The system SHOULD start a timer whose timeout value should be 16. The system SHOULD start a timer whose timeout value should be
larger than the worst-case anticipated RTT, and MUST increment a larger than the worst-case anticipated RTT, and MUST increment a
timeout counter associated with the I2. The sender SHOULD timeout counter associated with the I2. The sender SHOULD
retransmit the I2 upon a timeout and restart the timer, up to a retransmit the I2 upon a timeout and restart the timer, up to a
maximum of I2_RETRIES_MAX tries. maximum of I2_RETRIES_MAX tries.
18. If the system is in state I1-SENT, it shall transition to state 17. If the system is in state I1-SENT, it shall transition to state
I2-SENT. If the system is in any other state, it remains in the I2-SENT. If the system is in any other state, it remains in the
current state. current state.
8.6.1 Handling malformed messages 8.6.1 Handling malformed messages
If an implementation receives a malformed R1 message, it MUST If an implementation receives a malformed R1 message, it MUST
silently drop the packet. Sending a NOTIFY or ICMP would not help, silently drop the packet. Sending a NOTIFY or ICMP would not help,
as the sender of the R1 typically doesn't have any state. An as the sender of the R1 typically doesn't have any state. An
implementation SHOULD wait for some more time for a possible good R1, implementation SHOULD wait for some more time for a possible good R1,
after which it MAY try again by sending a new I1 packet. after which it MAY try again by sending a new I1 packet.
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Otherwise, the HIP implementation SHOULD process the I2. This Otherwise, the HIP implementation SHOULD process the I2. This
includes validation of the cookie puzzle solution, generating the includes validation of the cookie puzzle solution, generating the
Diffie-Hellman key, decrypting the Initiator's Host Identity, Diffie-Hellman key, decrypting the Initiator's Host Identity,
verifying the signature, creating state, and finally sending an R2. verifying the signature, creating state, and finally sending an R2.
The following steps define the conceptual processing rules for The following steps define the conceptual processing rules for
responding to an I2 packet: responding to an I2 packet:
1. The system MAY perform checks to verify that the I2 corresponds 1. The system MAY perform checks to verify that the I2 corresponds
to a recently sent R1. Such checks are implementation to a recently sent R1. Such checks are implementation
dependent. See Appendix D for a description of an example dependent. See Appendix C for a description of an example
implementation. implementation.
2. The system MUST check that the Responder's HIT corresponds to 2. The system MUST check that the Responder's HIT corresponds to one
one of its own HITs. of its own HITs.
3. If the system is in the R2-SENT state, it MAY check if the newly 3. If the system is in the R2-SENT state, it MAY check if the newly
received I2 is similar to the one that triggered moving to received I2 is similar to the one that triggered moving to
R2-SENT. If so, it MAY retransmit a previously sent R2, reset R2-SENT. If so, it MAY retransmit a previously sent R2, reset
the R2-SENT timer, and stay in R2-SENT. the R2-SENT timer, and stay in R2-SENT.
4. If the system is in any other state, it SHOULD check that the 4. If the system is in any other state, it SHOULD check that the
echoed R1 generation counter in I2 is within the acceptable echoed R1 generation counter in I2 is within the acceptable
range. Implementations MUST accept puzzles from the current range. Implementations MUST accept puzzles from the current
generation and MAY accept puzzles from earlier generations. If generation and MAY accept puzzles from earlier generations. If
the newly received I2 is outside the accepted range, the I2 is the newly received I2 is outside the accepted range, the I2 is
stale (perhaps replayed) and SHOULD be dropped. stale (perhaps replayed) and SHOULD be dropped.
5. The system MUST validate the solution to the cookie puzzle by 5. The system MUST validate the solution to the cookie puzzle by
computing the SHA-1 hash described in Section 7.3. computing the SHA-1 hash described in Section 7.3.
6. The I2 MUST have a single value in each of the HIP_TRANSFORM and 6. The I2 MUST have a single value in the HIP_TRANSFORM parameter,
ESP_TRANSFORM parameters, which MUST each match one of the which MUST match one of the values offered to the Initiator in
values offered to the Initiator in the R1 packet. the R1 packet.
7. The system must derive Diffie-Hellman keying material Kij based 7. The system must derive Diffie-Hellman keying material Kij based
on the public value and Group ID in the DIFFIE_HELLMAN on the public value and Group ID in the DIFFIE_HELLMAN
parameter. This key is used to derive the HIP and ESP parameter. This key is used to derive the HIP association keys,
association keys, as described in Section 9. If the as described in Section 9. If the Diffie-Hellman Group ID is
Diffie-Hellman Group ID is unsupported, the I2 packet is unsupported, the I2 packet is silently dropped.
silently dropped.
8. The encrypted HOST_ID decrypted by the Initiator encryption key 8. The encrypted HOST_ID decrypted by the Initiator encryption key
defined in Section 9. If the decrypted data is not an HOST_ID defined in Section 9. If the decrypted data is not an HOST_ID
parameter, the I2 packet is silently dropped. parameter, the I2 packet is silently dropped.
9. The implementation SHOULD also verify that the Initiator's HIT 9. The implementation SHOULD also verify that the Initiator's HIT in
in the I2 corresponds to the Host Identity sent in the I2. the I2 corresponds to the Host Identity sent in the I2.
10. The system MUST verify the HMAC according to the procedures in 10. The system MUST verify the HMAC according to the procedures in
Section 6.2.12. Section 6.2.10.
11. The system MUST verify the HIP_SIGNATURE according to Section 11. The system MUST verify the HIP_SIGNATURE according to
6.2.14 and Section 7.3. Section 6.2.12 and Section 7.3.
12. If the checks above are valid, then the system proceeds with 12. If the checks above are valid, then the system proceeds with
further I2 processing; otherwise, it discards the I2 and remains further I2 processing; otherwise, it discards the I2 and remains
in the same state. in the same state.
13. The I2 packet may have the C bit set -- in this case, the system 13. The I2 packet may have the C bit set -- in this case, the system
should anticipate the receipt of HIP CER packets that contain should anticipate the receipt of HIP CER packets that contain
the host identity corresponding to the responder's HIT. the host identity corresponding to the responder's HIT.
14. The I2 packet may have the A bit set -- in this case, the system 14. The I2 packet may have the A bit set -- in this case, the system
MAY choose to refuse it by dropping the I2 and returning to MAY choose to refuse it by dropping the I2 and returning to
state UNASSOCIATED. If the A bit is set, the Initiator's HIT is state UNASSOCIATED. If the A bit is set, the Initiator's HIT is
anonymous and should not be stored. anonymous and should not be stored.
15. The SPI field is parsed to obtain the SPI that will be used for 15. The system initialized the remaining variables in the associated
the Security Association outbound from the Responder and inbound
to the Initiator.
16. The system prepares and creates both incoming and outgoing ESP
security associations.
17. The system initialized the remaining variables in the associated
state, including Update ID counters. state, including Update ID counters.
18. Upon successful processing of an I2 in states UNASSOCIATED, 16. Upon successful processing of an I2 in states UNASSOCIATED,
I1-SENT, I2-SENT, and R2-SENT, an R2 is sent and the state I1-SENT, I2-SENT, and R2-SENT, an R2 is sent and the state
machine transitions to state ESTABLISHED. machine transitions to state ESTABLISHED.
19. Upon successful processing of an I2 in state ESTABLISHED/ 17. Upon successful processing of an I2 in state ESTABLISHED, the
REKEYING, the old Security Association is dropped and a new one old HIP association is dropped and a new one is installed, an R2
is installed, an R2 is sent, and the state machine transitions is sent, and the state machine transitions to R2-SENT.
to R2-SENT, dropping any possibly ongoing rekeying attempt. 18. Upon transitioning to R2-SENT, start a timer. Leave R2-SENT if
20. Upon transitioning to R2-SENT, start a timer. Leave R2-SENT if
either the timer expires (allowing for maximal retransmission of either the timer expires (allowing for maximal retransmission of
I2s), some data has been received on the incoming SA, or an I2s), some data has been received on the incoming HIP
UPDATE packet has been received (or some other packet that association, or an UPDATE packet has been received (or some
indicates that the peer has moved to ESTABLISHED). other packet that indicates that the peer has moved to
ESTABLISHED).
8.7.1 Handling malformed messages 8.7.1 Handling malformed messages
If an implementation receives a malformed I2 message, the behaviour If an implementation receives a malformed I2 message, the behaviour
SHOULD depend on how much checks the message has already passed. If SHOULD depend on how much checks the message has already passed. If
the puzzle solution in the message has already been checked, the the puzzle solution in the message has already been checked, the
implementation SHOULD report the error by responding with a NOTIFY implementation SHOULD report the error by responding with a NOTIFY
packet. Otherwise the implementation MAY respond with an ICMP packet. Otherwise the implementation MAY respond with an ICMP
message as defined in Section 6.3. message as defined in Section 6.3.
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An R2 received in states UNASSOCIATED, I1-SENT, ESTABLISHED, or An R2 received in states UNASSOCIATED, I1-SENT, ESTABLISHED, or
REKEYING results in the R2 being dropped and the state machine REKEYING results in the R2 being dropped and the state machine
staying in the same state. If an R2 is received in state I2-SENT, it staying in the same state. If an R2 is received in state I2-SENT, it
SHOULD be processed. SHOULD be processed.
The following steps define the conceptual processing rules for The following steps define the conceptual processing rules for
incoming R2 packet: incoming R2 packet:
1. The system MUST verify that the HITs in use correspond to the 1. The system MUST verify that the HITs in use correspond to the
HITs that were received in R1. HITs that were received in R1.
2. The system MUST verify the HMAC_2 according to the procedures in 2. The system MUST verify the HMAC_2 according to the procedures in
Section 6.2.13. Section 6.2.11.
3. The system MUST verify the HIP signature according to the 3. The system MUST verify the HIP signature according to the
procedures in Section 6.2.14. procedures in Section 6.2.12.
4. If any of the checks above fail, there is a high probability of 4. If any of the checks above fail, there is a high probability of
an ongoing man-in-the-middle or other security attack. The an ongoing man-in-the-middle or other security attack. The
system SHOULD act accordingly, based on its local policy. system SHOULD act accordingly, based on its local policy.
5. If the system is in any other state than I2-SENT, the R2 is 5. If the system is in any other state than I2-SENT, the R2 is
silently dropped. silently dropped.
6. The SPI field is parsed to obtain the SPI that will be used for 6. Upon successful processing of the R2, the state machine moves to
the ESP Security Association inbound to the Responder. The
system uses this SPI to create or activate the outgoing ESP
security association used to send packets to the peer.
7. Upon successful processing of the R2, the state machine moves to
state ESTABLISHED. state ESTABLISHED.
8.9 Dropping HIP associations 8.9 Sending UPDATE packets
A HIP implementation is free to drop a HIP association at any time,
based on its own policy. If a HIP host decides to drop an HIP
association, it deletes the IPsec SAs related to that association and
the corresponding HIP state, including the keying material. The
implementation MUST also drop the peer's R1 generation counter value,
unless a local policy explicitly defines that the value of that
particular host is stored. An implementation MUST NOT store R1
generation counters by default, but storing R1 generation counter
values, if done, MUST be configured by explicit HITs.
8.10 Initiating rekeying
A system may initiate the rekey procedure at any time. It MUST
initiate a rekey if its incoming ESP sequence counter is about to
overflow. The system MUST NOT replace its keying material until the
rekeying packet exchange successfully completes. Optionally,
depending on policy, a system may include a new Diffie-Hellman key
for use in new KEYMAT generation. New KEYMAT generation occurs prior
to drawing the new keys.
In the conceptual state machine, a system rekeys when it sends a NES
parameter to the peer and receives both an ACK of the relevant UPDATE
message and its peer's NES parameter. To leave REKEYING state, both
parameters must be received. It may be that the ACK and the NES
arrive in different UPDATE messages. This is always true if a system
does not initiate rekeying but responds to a rekeying request from
the peer, but may also occur if two systems initiate a rekey nearly
simultaneously. In such a case, if the system is in state REKEYING,
it saves the one parameter and waits for the other before leaving
state REKEYING. This implies that the REKEYING state may have
conceptual substates.
The following steps define the processing rules for initiating a
rekey:
1. The system decides whether to continue to use the existing KEYMAT
or to generate new KEYMAT. In the latter case, the system MUST
generate a new Diffie-Hellman public key.
2. The system increments its outgoing Update ID by one.
3. The system creates a UPDATE packet, which contains an SEQ
parameter (with the current value of Update ID), NES parameter
and an optional DIFFIE_HELLMAN parameter. If the UPDATE packet
contains the DIFFIE_HELLMAN parameter, the Keymat Index in the
NES parameter MUST be zero. If the UPDATE does not contain
DIFFIE_HELLMAN, the NES Keymat Index MUST be larger or equal to
the index of the next byte to be drawn from the current KEYMAT.
4. The system sends the UPDATE packet and transitions to state
REKEYING.
5. The system SHOULD start a timer whose timeout value should be
larger than the worst-case anticipated RTT, and MUST increment a
timeout counter associated with UPDATE. The sender SHOULD
retransmit the UPDATE upon a timeout and restart the timer, up to
a maximum of UPDATE_RETRIES_MAX tries.
6. The system MUST NOT delete its existing SAs, but continue using
them if its policy still allows. The UPDATE procedure SHOULD be
initiated early enough to make sure that the SA replay counters
do not overflow.
7. In case a protocol error occurs and the peer system acknowledges
the UPDATE but does not itself send a NES, the system may hang in
state REKEYING. To guard against this, a system MAY re-initiate
the rekeying procedure after some time waiting for the peer to
respond, or it MAY decide to abort the HIP association after
waiting for an implementation-dependent time. The system MUST
NOT hang in state REKEYING for an indefinite time.
To simplify the state machine, a host MUST NOT generate new UPDATEs A host sends an UPDATE packet when it wants to update some
(with higher Update IDs) while in state REKEYING, unless it is information related to a HIP association. There are a number of
restarting the rekeying process. likely situations, e.g. mobility management and rekeying of an
existing ESP Security Association. The following paragraphs define
the conceptual rules for sending an UPDATE packet to the peer.
Additional steps can be defined in other documents where the UPDATE
packet is used.
1. The system increments its own Update ID value by one.
2. The system creates an UPDATE packet that contains a SEQ parameter
with the current value of Update ID. The UPDATE packet may also
include an ACK of the Update ID found in the received UPDATE SEQ
parameter, if any.
3. The system sends the created UPDATE packet and starts an UPDATE
timer. The default value for the timer is 2 * RTT estimate.
4. If the UPDATE timer expires, the UPDATE is resent. The UPDATE
can be resent UPDATE_RETRY_MAX times. The UPDATE timer SHOULD be
exponentially backed off for subsequent retransmissions.
8.11 Processing UPDATE packets 8.10 Receiving UPDATE packets
When a system receives an UPDATE packet, its processing depends on When a system receives an UPDATE packet, its processing depends on
the state of the HIP association and the presence of and values of the state of the HIP association and the presence of and values of
the SEQ and ACK parameters. An UPDATE MUST be processed if the the SEQ and ACK parameters. Typically, an UPDATE message also
following conditions hold (note: UPDATEs may also be processed when carries optional parameters whose handling is defined in separate
additional conditions hold, as specified in other drafts): documents.
1. If there is no corresponding HIP association, the implementation 1. If there is no corresponding HIP association, the implementation
MAY reply with an ICMP Parameter Problem, as specified in Section MAY reply with an ICMP Parameter Problem, as specified in
6.3.5. Section 6.3.4.
2. The state of the HIP association is ESTABLISHED or REKEYING, and
both the SEQ and NES parameters are present in the UPDATE. This
is the case for which the peer host is in the process of
rekeying.
3. The state of the HIP association is REKEYING and an ACK (of
outstanding Update ID) is in the UPDATE. This case usually
corresponds to the peer completing the rekeying process first.
If the above conditions hold, the following steps define the 2. If the association is in the ESTABLISHED state and the SEQ
conceptual processing rules for handling a received UPDATE packet: parameter is present, the UPDATE is processed and replied as
1. If the SEQ parameter is present, and the Update ID in the described in Section 8.10.1.
received SEQ is smaller than the stored Update ID for the host, 3. Additionally (or alternatively), if the association is in the
the packet MUST BE dropped. ESTABLISHED state and there is an ACK (of outstanding Update ID)
2. If the SEQ parameter is present, and the Update ID in the in the UPDATE, the UPDATE is processed as described in
received SEQ is equal to the stored Update ID for the host, the Section 8.10.2.
packet is treated as a retransmission. However, the HMAC
verification (next step) MUST NOT be skipped. (A byte-by-byte 8.10.1 Handling a SEQ paramaeter in a received UPDATE message
comparison of the received and a store packet would be OK,
though.) It is recommended that a host cache the last packet 1. If the Update ID in the received SEQ is smaller than the stored
that was acked to avoid the cost of generating a new ACK packet Update ID for the peer host, the packet MUST BE dropped as a
to respond to a replayed UPDATE. Systems MUST again acknowledge duplicate.
such apparent UPDATE message retransmissions but SHOULD also 2. If the Update ID in the received SEQ is equal to the stored
consider rate-limiting such retransmission responses to guard Update ID for the host, the packet is treated as a
against replay attacks. retransmission. The HMAC verification (next step) MUST NOT be
skipped. (A byte-by-byte comparison of the received and a store
packet would be OK, though.) It is recommended that a host cache
the last packet that was acked to avoid the cost of generating a
new ACK packet to respond to a replayed UPDATE. The system MUST
acknowledge, again, such (apparent) UPDATE message
retransmissions but SHOULD also consider rate-limiting such
retransmission responses to guard against replay attacks.
3. The system MUST verify the HMAC in the UPDATE packet. If the 3. The system MUST verify the HMAC in the UPDATE packet. If the
verification fails, the packet MUST be dropped. verification fails, the packet MUST be dropped.
4. If the received UPDATE contains a DIFFIE_HELLMAN parameter, the 4. The system MAY verify the SIGNATURE in the UPDATE packet. If the
received Keymat Index MUST be zero. If this test fails, the
packet SHOULD be dropped and the system SHOULD log an error
message.
5. The system MAY verify the SIGNATURE in the UPDATE packet. If the
verification fails, the packet SHOULD be dropped and an error verification fails, the packet SHOULD be dropped and an error
message logged. message logged.
5. If a new SEQ parameter is being processed, the system MUST record
6. If a new SEQ parameter is being processed, the system MUST record
the Update ID in the received SEQ parameter, for replay the Update ID in the received SEQ parameter, for replay
protection. protection.
7. If the system is in state ESTABLISHED, and the UPDATE has the NES 6. An UPDATE acknowledgement packet with ACK parameter is prepared
and SEQ parameters, the packet processing continues as specified and send to the peer.
in Section 8.11.1.
8. If the system is in state REKEYING, the packet processing
continues as specified in Section 8.11.2.
8.11.1 Processing an UPDATE packet in state ESTABLISHED
The following steps define the conceptual processing rules responding
handling a received initial UPDATE packet:
1. The system consults its policy to see if it needs to generate a
new Diffie-Hellman key, and generates a new key if needed. The
system records any newly generated or received Diffie-Hellman
keys, for use in KEYMAT generation upon leaving the REKEYING
state.
2. If the system generated new Diffie-Hellman key in the previous
step, or it received a DIFFIE_HELLMAN parameter, it sets NES
Keymat Index to zero. Otherwise, the NES Keymat Index MUST be
larger or equal to the index of the next byte to be drawn from
the current KEYMAT. In this case, it is RECOMMENDED that the
host use the Keymat Index requested by the peer in the received
NES.
3. The system increments its outgoing Update ID by one.
4. The system creates a UPDATE packet, which contains an SEQ
parameter (with the current value of Update ID), NES parameter
and the optional DIFFIE_HELLMAN parameter. The UPDATE packet also
includes the ACK of the Update ID found in the received UPDATE
SEQ parameter.
5. The system sends the UPDATE packet and transitions to state
REKEYING. The system stores any received NES and DIFFIE_HELLMAN
parameters. At this point, it only needs to receive an ACK of
its current Update ID to finish rekeying.
8.11.2 Processing an UPDATE packet in state REKEYING
The following steps define the conceptual processing rules responding
handling a received reply UPDATE packet:
1. If the packet contains a SEQ and NES parameters, then the system
sends a new UPDATE packet with an ACK of the peer's Update ID as
received in the SEQ parameter. Additionally, if the UPDATE packet
contained an ACK of the outstanding Update ID, or if the ACK of
the UPDATE packet that contained the NES has already been
received, the system stores the received NES and (optional)
DIFFIE_HELLMAN parameters and finishes the rekeying procedure as
described in Section 8.11.3. If the ACK of the outstanding Update
ID has not been received, stay in state REKEYING after storing
the received NES and (optional) DIFFIE_HELLMAN.
2. If the packet contains an ACK parameter that ACKs the outstanding
Update ID, and the system has previously received a NES from the
peer, the system finishes the rekeying procedure as described in
Section 8.11.3. If the system is still waiting for the peer's
NES parameter (to arrive in subsequent UPDATE message), the
system stays in state REKEYING.
8.11.3 Leaving REKEYING state 8.10.2 Handling an ACK parameter in a received UPDATE packet
A system leaves REKEYING state when it has received both a NES from 1. The UPDATE packet with ACK must match to an earlier sent UPDATE
its peer and the ACK of the Update ID that was sent in its own NES to packet. If no match is found, the packet MUST be dropped.
the peer. The following steps are taken: 2. The system MUST verify the HMAC in the UPDATE packet. If the
1. If either the received UPDATE contains a new Diffie-Hellman key, verification fails, the packet MUST be dropped.
the system has a new Diffie-Hellman key from initiating rekey, or 3. The system MAY verify the SIGNATURE in the UPDATE packet. If the
both, the system generates new KEYMAT. If there is only one new verification fails, the packet SHOULD be dropped and an error
Diffie-Hellman key, the old key is used as the other key. message logged.
2. If the system generated new KEYMAT in the previous step, it sets 4. The corresponding UPDATE timer is stopped (see Section 8.9) so
Keymat Index to zero, independent on whether the received UPDATE that the now acknowledged UPDATE is no longer retransmitted.
included a Diffie-Hellman key or not. If the system did not
generate new KEYMAT, it uses the lowest Keymat Index of the two
NES parameters.
3. The system draws keys for new incoming and outgoing ESP SAs,
starting from the Keymat Index, and prepares new incoming and
outgoing ESP SAs. The SPI for the outgoing SA is the new SPI
value from the UPDATE. The SPI for the incoming SA was generated
when NES was sent. The order of the keys retrieved from the
KEYMAT during rekeying process is similar to that described in
Section 9. Note, that only IPsec ESP keys are retrieved during
rekeying process, not the HIP keys.
4. The system cancels any timers protecting the UPDATE and
transitions to ESTABLISHED.
5. The system starts to send to the new outgoing SA and prepares to
start receiving data on the new incoming SA.
8.12 Processing CER packets 8.11 Processing CER packets
Processing CER packets is OPTIONAL, and currently undefined. Processing CER packets is OPTIONAL, and currently undefined.
8.13 Processing NOTIFY packets 8.12 Processing NOTIFY packets
Processing NOTIFY packets is OPTIONAL. If processed, any errors Processing NOTIFY packets is OPTIONAL. If processed, any errors
noted by the NOTIFY parameter SHOULD be taken into account by the HIP noted by the NOTIFY parameter SHOULD be taken into account by the HIP
state machine (e.g., by terminating a HIP handshake), and the error state machine (e.g., by terminating a HIP handshake), and the error
SHOULD be logged. SHOULD be logged.
8.14 Processing CLOSE packets 8.13 Processing CLOSE packets
When the host receives a CLOSE message it responds with a CLOSE_ACK When the host receives a CLOSE message it responds with a CLOSE_ACK
message and moves to CLOSED state. (The authenticity of the CLOSE message and moves to CLOSED state. (The authenticity of the CLOSE
message is verified using both HMAC and SIGNATURE). This processing message is verified using both HMAC and SIGNATURE). This processing
applies whether or not the HIP association state is CLOSING in order applies whether or not the HIP association state is CLOSING in order
to handle CLOSE messages from both ends crossing in flight. to handle CLOSE messages from both ends crossing in flight.
The HIP association is not discarded before the host moves from the The HIP association is not discarded before the host moves from the
UNASSOCIATED state. UNASSOCIATED state.
Once the closing process has started, any need to send data packets Once the closing process has started, any need to send data packets
will trigger creating and establishing of a new HIP association, will trigger creating and establishing of a new HIP association,
starting with sending an I1. starting with sending an I1.
If there is no corresponding HIP association, the implementation MAY If there is no corresponding HIP association, the implementation MAY
reply to a CLOSE with an ICMP Parameter Problem, as specified in reply to a CLOSE with an ICMP Parameter Problem, as specified in
Section 6.3.5. Section 6.3.4.
8.15 Processing CLOSE_ACK packets 8.14 Processing CLOSE_ACK packets
When a host receives a CLOSE_ACK message it verifies that it is in When a host receives a CLOSE_ACK message it verifies that it is in
CLOSING or CLOSED state and that the CLOSE_ACK was in response to the CLOSING or CLOSED state and that the CLOSE_ACK was in response to the
CLOSE (using the included ECHO_REPLY in response to the sent CLOSE (using the included ECHO_REPLY in response to the sent
ECHO_REQUEST). ECHO_REQUEST).
The CLOSE_ACK uses HMAC and SIGNATURE for verification. The state is The CLOSE_ACK uses HMAC and SIGNATURE for verification. The state is
discarded when the state changes to UNASSOCIATED and, after that, discarded when the state changes to UNASSOCIATED and, after that,
NOTIFY is sent as a response to a CLOSE message. NOTIFY is sent as a response to a CLOSE message.
8.15 Dropping HIP associations
A HIP implementation is free to drop a HIP association at any time,
based on its own policy. If a HIP host decides to drop a HIP
association, it deletes the corresponding HIP state, including the
keying material. The implementation MUST also drop the peer's R1
generation counter value, unless a local policy explicitly defines
that the value of that particular host is stored. An implementation
MUST NOT store R1 generation counters by default, but storing R1
generation counter values, if done, MUST be configured by explicit
HITs.
9. HIP KEYMAT 9. HIP KEYMAT
HIP keying material is derived from the Diffie-Hellman Kij produced HIP keying material is derived from the Diffie-Hellman Kij produced
during the base HIP exchange. The Initiator has Kij during the during the HIP base exchange. The Initiator has Kij during the
creation of the I2 packet, and the Responder has Kij once it receives creation of the I2 packet, and the Responder has Kij once it receives
the I2 packet. This is why I2 can already contain encrypted the I2 packet. This is why I2 can already contain encrypted
information. information.
The KEYMAT is derived by feeding Kij and the HITs into the following The KEYMAT is derived by feeding Kij and the HITs into the following
operation; the | operation denotes concatenation. operation; the | operation denotes concatenation.
KEYMAT = K1 | K2 | K3 | ... KEYMAT = K1 | K2 | K3 | ...
where where
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method described in the previous paragraph. HOST_g denotes the host method described in the previous paragraph. HOST_g denotes the host
with the greater HIT value, and HOST_l the host with the lower HIT with the greater HIT value, and HOST_l the host with the lower HIT
value. value.
The drawing order for initial keys: The drawing order for initial keys:
HIP-gl encryption key for HOST_g's outgoing HIP packets HIP-gl encryption key for HOST_g's outgoing HIP packets
HIP-gl integrity (HMAC) key for HOST_g's outgoing HIP packets HIP-gl integrity (HMAC) key for HOST_g's outgoing HIP packets
HIP-lg encryption key (currently unused) for HOST_l's outgoing HIP HIP-lg encryption key (currently unused) for HOST_l's outgoing HIP
packets packets
HIP-lg integrity (HMAC) key for HOST_l's outgoing HIP packets HIP-lg integrity (HMAC) key for HOST_l's outgoing HIP packets
SA-gl ESP encryption key for HOST_g's outgoing traffic
SA-gl ESP authentication key for HOST_g's outgoing traffic
SA-lg ESP encryption key for HOST_l's outgoing traffic
SA-lg ESP authentication key for HOST_l's outgoing traffic
The number of bits drawn for a given algorithm is the "natural" size The number of bits drawn for a given algorithm is the "natural" size
of the keys. For the mandatory algorithms, the following sizes of the keys. For the mandatory algorithms, the following sizes
apply: apply:
AES 128 bits AES 128 bits
SHA-1 160 bits SHA-1 160 bits
NULL 0 bits NULL 0 bits
The four HIP keys are only drawn from KEYMAT during a HIP I1->R2
exchange. Subsequent rekeys using UPDATE will only draw the four ESP
keys from KEYMAT. Section 8.11 describes the rules for reusing or
regenerating KEYMAT based on the UPDATE exchange.
10. HIP Fragmentation Support 10. HIP Fragmentation Support
A HIP implementation must support IP fragmentation / reassembly. A HIP implementation must support IP fragmentation / reassembly.
Fragment reassembly MUST be implemented in both IPv4 and IPv6, but Fragment reassembly MUST be implemented in both IPv4 and IPv6, but
fragment generation MUST be implemented only in IPv4 (IPv4 stacks and fragment generation MUST be implemented only in IPv4 (IPv4 stacks and
networks will usually do this by default) and SHOULD be implemented networks will usually do this by default) and SHOULD be implemented
in IPv6. In the IPv6 world, the minimum MTU is larger, 1280 bytes, in IPv6. In the IPv6 world, the minimum MTU is larger, 1280 bytes,
than in the IPv4 world. The larger MTU size is usually sufficient than in the IPv4 world. The larger MTU size is usually sufficient
for most HIP packets, and therefore fragment generation may not be for most HIP packets, and therefore fragment generation may not be
needed. If a host expects to send HIP packets that are larger than needed. If a host expects to send HIP packets that are larger than
the minimum IPv6 MTU, it MUST implement fragment generation even for the minimum IPv6 MTU, it MUST implement fragment generation even for
IPv6. IPv6.
In the IPv4 world, HIP packets may encounter low MTUs along their In the IPv4 world, HIP packets may encounter low MTUs along their
routed path. Since HIP does not provide a mechanism to use multiple routed path. Since HIP does not provide a mechanism to use multiple
IP datagrams for a single HIP packet, support of path MTU discovery IP datagrams for a single HIP packet, support of path MTU discovery
does not bring any value to HIP in the IPv4 world. HIP aware NAT does not bring any value to HIP in the IPv4 world. HIP-aware NAT
systems MUST perform any IPv4 reassembly/fragmentation. systems MUST perform any IPv4 reassembly/fragmentation.
All HIP implementations MUST employ a reassembly algorithm that is All HIP implementations MUST employ a reassembly algorithm that is
sufficiently resistant against DoS attacks. sufficiently resistant against DoS attacks.
11. ESP with HIP 11. HIP Policies
HIP is designed to be used in end-to-end fashion. The IPsec mode
used with HIP is the BEET mode (A Bound End-to-End mode for ESP)
[27]. The BEET mode provides some features from both IPsec tunnel
and transport modes. The HIP uses HITs and LSIs as the "inner"
addresses and IP addresses as "outer" addresses like IP addresses are
used in the tunnel mode. Instead of tunneling packets between hosts,
a conversion between inner and outer addresses is made at end-hosts
and the inner address is never sent in the wire after the initial HIP
negotiation. BEET provides IPsec transport mode syntax (no inner
headers) with limited tunnel mode semantics (fixed logical inner
addresses - the HITs - and changeable outer IP addresses).
Since HIP does not negotiate any lifetimes, all lifetimes are local
policy. The only lifetimes a HIP implementation MUST support are
sequence number rollover (for replay protection), and SA timeout. An
SA times out if no packets are received using that SA. The default
timeout value is 15 minutes. Implementations MAY support lifetimes
for the various ESP transforms.
11.1 ESP Security Associations
Each HIP association is linked with two ESP SAs, one incoming and one
outgoing. The Initiator's incoming SA corresponds with the
Responder's outgoing one. The initiator defines the SPI for this
association, as defined in Section 3.3. This SA is called SA-RI, and
the corresponding SPI is called SPI-RI. Respectively, the
Responder's incoming SA corresponds with the Initiator's outgoing SA
and is called SA-IR, with the SPI-IR.
The Initiator creates SA-RI as a part of R1 processing, before
sending out the I2, as explained in Section 8.6. The keys are
derived from KEYMAT, as defined in Section 9. The Responder creates
SA-RI as a part of I2 processing, see Section 8.7.
The Responder creates SA-IR as a part of I2 processing, before
sending out R2, see Step 17 in Section 8.7. The Initiator creates
SA-IR when processing R2, see Step 7 in Section 8.8.
11.2 Updating ESP SAs during rekeying
After the initial 4-way handshake and SA establishment, both hosts
are in state ESTABLISHED. There are no longer Initiator and
Responder roles and the association is symmetric. In this
subsection, the initiating party of the rekey procedure is denoted
with I' and the peer with R'.
The I' initiates the rekeying process when needed (see Section 8.10).
It creates an UPDATE packet with required information and sends it to
the peer node. The old SAs are still in use.
The R', after receiving and processing the UPDATE (see Section 8.11),
generates new SAs: SA-I'R' and SA-R'I'. It does not take the new
outgoing SA into use, but uses still the old one, so there exists two
SA pairs towards the same peer host. For the new outgoing SA, the
SPI-R'I' value is picked from the received UPDATE packet. The R'
generates the new SPI value for the incoming SA, SPI-I'R', and
includes it in the response UPDATE packet.
When the I' receives a response UPDATE from the R', it generates new
SAs, as described in Section 8.11: SA-I'R' and SA-R'I'. It starts
using the new outgoing SA immediately.
The R' starts using the new outgoing SA when it receives traffic from
the new incoming SA. After this, the R' can remove old SAs.
Similarly, when the I' receives traffic from the new incoming SA, it
can safely remove old SAs.
11.3 Security Association Management
An SA pair is indexed by the 2 SPIs and 2 HITs (both HITs since a
system can have more than one HIT). An inactivity timer is
recommended for all SAs. If the state dictates the deletion of an
SA, a timer is set to allow for any late arriving packets.
11.4 Security Parameter Index (SPI)
The SPIs in ESP provide a simple compression of the HIP data from all
packets after the HIP exchange. This does require a per HIT- pair
Security Association (and SPI), and a decrease of policy granularity
over other Key Management Protocols like IKE.
When a host rekeys, it gets a new SPI from its partner.
11.5 Supported Transforms
All HIP implementations MUST support AES [10] and HMAC-SHA-1-96 [6].
If the Initiator does not support any of the transforms offered by
the Responder in the R1 HIP packet, it MUST use AES and HMAC-SHA-1-96
and state so in the I2 HIP packet.
In addition to AES, all implementations MUST implement the ESP NULL
encryption and authentication algorithms. These algorithms are
provided mainly for debugging purposes, and SHOULD NOT be used in
production environments. The default configuration in
implementations MUST be to reject NULL encryption or authentication.
11.6 Sequence Number
The Sequence Number field is MANDATORY in ESP. Anti-replay
protection MUST be used in an ESP SA established with HIP.
This means that each host MUST rekey before its sequence number
reaches 2^32, or if extended sequence numbers are used, 2^64. Note
that in HIP rekeying, unlike IKE rekeying, only one Diffie-Hellman
key can be changed, that of the rekeying host. However, if one host
rekeys, the other host SHOULD rekey as well.
In some instances, a 32-bit sequence number is inadequate. In the
ESP_TRANSFORM parameter, a peer MAY require that a 64 bit sequence
number be used. In this case the higher 32 bits are NOT included in
the ESP header, but are simply kept local to both peers. 64 bit
sequence numbers must only be used for ciphers that will not be open
to cryptanalysis as a result. AES is one such cipher.
12. HIP Policies
There are a number of variables that will influence the HIP exchanges There are a number of variables that will influence the HIP exchanges
that each host must support. All HIP implementations MUST support that each host must support. All HIP implementations MUST support
more than one simultaneous HIs, at least one of which SHOULD be more than one simultaneous HIs, at least one of which SHOULD be
reserved for anonymous usage. Although anonymous HIs will be rarely reserved for anonymous usage. Although anonymous HIs will be rarely
used as responder HIs, they will be common for Initiators. Support used as responder HIs, they will be common for Initiators. Support
for more than two HIs is RECOMMENDED. for more than two HIs is RECOMMENDED.
Many Initiators would want to use a different HI for different Many Initiators would want to use a different HI for different
Responders. The implementations SHOULD provide for an ACL of Responders. The implementations SHOULD provide for an ACL of
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selection would be from most specific to most general. selection would be from most specific to most general.
The value of K used in the HIP R1 packet can also vary by policy. K The value of K used in the HIP R1 packet can also vary by policy. K
should never be greater than 20, but for trusted partners it could be should never be greater than 20, but for trusted partners it could be
as low as 0. as low as 0.
Responders would need a similar ACL, representing which hosts they Responders would need a similar ACL, representing which hosts they
accept HIP exchanges, and the preferred transform and local accept HIP exchanges, and the preferred transform and local
lifetimes. Wildcarding SHOULD be supported for this ACL also. lifetimes. Wildcarding SHOULD be supported for this ACL also.
13. Security Considerations 12. Security Considerations
HIP is designed to provide secure authentication of hosts and to
provide a fast key exchange for IPsec ESP. HIP also attempts to
limit the exposure of the host to various denial-of-service and man-
in-the-middle attacks. In so doing, HIP itself is subject to its own
DoS and MitM attacks that potentially could be more damaging to a
host's ability to conduct business as usual.
HIP enabled ESP is IP address independent. This might seem to make HIP is designed to provide secure authentication of hosts. HIP also
it easier for an attacker, but ESP with replay protection is already attempts to limit the exposure of the host to various
as well protected as possible, and the removal of the IP address as a denial-of-service and man-in-the-middle (MitM) attacks. In so doing,
check should not increase the exposure of ESP to DoS attacks. HIP itself is subject to its own DoS and MitM attacks that
Furthermore, this is in line with the forthcoming revision of ESP. potentially could be more damaging to a host's ability to conduct
business as usual.
Denial-of-service attacks take advantage of the cost of start of Denial-of-service attacks take advantage of the cost of start of
state for a protocol on the Responder compared to the 'cheapness' on state for a protocol on the Responder compared to the 'cheapness' on
the Initiator. HIP makes no attempt to increase the cost of the the Initiator. HIP makes no attempt to increase the cost of the
start of state on the Initiator, but makes an effort to reduce the start of state on the Initiator, but makes an effort to reduce the
cost to the Responder. This is done by having the Responder start cost to the Responder. This is done by having the Responder start
the 3-way exchange instead of the Initiator, making the HIP protocol the 3-way exchange instead of the Initiator, making the HIP protocol
4 packets long. In doing this, packet 2 becomes a 'stock' packet 4 packets long. In doing this, packet 2 becomes a 'stock' packet
that the Responder MAY use many times. The duration of use is a that the Responder MAY use many times. The duration of use is a
paranoia versus throughput concern. Using the same Diffie- Hellman paranoia versus throughput concern. Using the same Diffie- Hellman
values and random puzzle I has some risk. This risk needs to be values and random puzzle #I has some risk. This risk needs to be
balanced against a potential storm of HIP I1 packets. balanced against a potential storm of HIP I1 packets.
This shifting of the start of state cost to the Initiator in creating This shifting of the start of state cost to the Initiator in creating
the I2 HIP packet, presents another DoS attack. The attacker spoofs the I2 HIP packet, presents another DoS attack. The attacker spoofs
the I1 HIP packet and the Responder sends out the R1 HIP packet. the I1 HIP packet and the Responder sends out the R1 HIP packet.
This could conceivably tie up the 'initiator' with evaluating the R1 This could conceivably tie up the 'initiator' with evaluating the R1
HIP packet, and creating the I2 HIP packet. The defense against this HIP packet, and creating the I2 HIP packet. The defense against this
attack is to simply ignore any R1 packet where a corresponding I1 or attack is to simply ignore any R1 packet where a corresponding I1 was
ESP data was not sent. not sent.
A second form of DoS attack arrives in the I2 HIP packet. Once the A second form of DoS attack arrives in the I2 HIP packet. Once the
attacking Initiator has solved the cookie challenge, it can send attacking Initiator has solved the puzzle, it can send packets with
packets with spoofed IP source addresses with either invalid spoofed IP source addresses with either invalid encrypted HIP payload
encrypted HIP payload component or a bad HIP signature. This would component or a bad HIP signature. This would take resources in the
take resources in the Responder's part to reach the point to discover Responder's part to reach the point to discover that the I2 packet
that the I2 packet cannot be completely processed. The defense cannot be completely processed. The defense against this attack is
against this attack is after N bad I2 packets, the Responder would after N bad I2 packets, the Responder would discard any I2s that
discard any I2s that contain the given Initiator HIT. Thus will shut contain the given Initiator HIT. Thus will shut down the attack.
down the attack. The attacker would have to request another R1 and The attacker would have to request another R1 and use that to launch
use that to launch a new attack. The Responder could up the value of a new attack. The Responder could up the value of K while under
K while under attack. On the downside, valid I2s might get dropped attack. On the downside, valid I2s might get dropped too.
too.
A third form of DoS attack is emulating the restart of state after a A third form of DoS attack is emulating the restart of state after a
reboot of one of the partners. A host restarting would send an I1 to reboot of one of the partners. A host restarting would send an I1 to
a peer, which would respond with an R1 even if it were in state a peer, which would respond with an R1 even if it were in the
ESTABLISHED. If the I1 were spoofed, the resulting R1 would be ESTABLISHED state. If the I1 were spoofed, the resulting R1 would be
received unexpectedly by the spoofed host and would be dropped, as in received unexpectedly by the spoofed host and would be dropped, as in
the first case above. the first case above.
A fourth form of DoS attack is emulating the end of state. HIP A fourth form of DoS attack is emulating the end of state. HIP
relies on timers plus a CLOSE/CLOSE_ACK handshake to explicitly relies on timers plus a CLOSE/CLOSE_ACK handshake to explicitly
signals the end of a state. Because both CLOSE and CLOSE_ACK signals the end of a state. Because both CLOSE and CLOSE_ACK
messages contain an HMAC, an outsider cannot close a connection. The messages contain an HMAC, an outsider cannot close a connection. The
presence of an additional SIGNATURE allows middle-boxes to inspect presence of an additional SIGNATURE allows middle-boxes to inspect
these messages and discard the associated state (for e.g., these messages and discard the associated state (for e.g.,
firewalling, SPI-based NATing, etc.). However, the optional behavior firewalling, SPI-based NATing, etc.). However, the optional behavior
of replying to CLOSE with an ICMP Parameter Problem packet (as of replying to CLOSE with an ICMP Parameter Problem packet (as
described in Section 6.3.5), might allow an IP spoofer sending CLOSE described in Section 6.3.4) might allow an IP spoofer sending CLOSE
messages to launch reflection attacks. messages to launch reflection attacks.
A fifth form of DoS attack is replaying R1s to cause the initiator to A fifth form of DoS attack is replaying R1s to cause the initiator to
solve stale puzzles and become out of synchronization with the solve stale puzzles and become out of synchronization with the
responder. The R1 generation counter is a monotonically increasing responder. The R1 generation counter is a monotonically increasing
counter designed to protect against this attack, as described in counter designed to protect against this attack, as described in
section Section 4.1.3. section Section 4.1.3.
Man-in-the-middle attacks are difficult to defend against, without Man-in-the-middle attacks are difficult to defend against, without
third-party authentication. A skillful MitM could easily handle all third-party authentication. A skillful MitM could easily handle all
skipping to change at page 88, line 5 skipping to change at page 82, line 5
similar attack against the Responder is more involved. First an ICMP similar attack against the Responder is more involved. First an ICMP
message is expected if the I1 was a DoS attack and the real owner of message is expected if the I1 was a DoS attack and the real owner of
the spoofed IP address does not support HIP. The Responder SHOULD the spoofed IP address does not support HIP. The Responder SHOULD
NOT act on this ICMP message to remove the minimal state from the R1 NOT act on this ICMP message to remove the minimal state from the R1
HIP packet (if it has one), but wait for either a valid I2 HIP packet HIP packet (if it has one), but wait for either a valid I2 HIP packet
or the natural timeout of the R1 HIP packet. This is to allow for a or the natural timeout of the R1 HIP packet. This is to allow for a
sophisticated attacker that is trying to break up the HIP exchange. sophisticated attacker that is trying to break up the HIP exchange.
Likewise, the Initiator should ignore any ICMP message while waiting Likewise, the Initiator should ignore any ICMP message while waiting
for an R2 HIP packet, deleting state only after a natural timeout. for an R2 HIP packet, deleting state only after a natural timeout.
14. IANA Considerations 13. IANA Considerations
IANA has assigned IP Protocol number TBD to HIP. IANA has assigned IP Protocol number TBD to HIP.
15. Acknowledgments IANA needs to create registries for:
1. HIP packet types
2. HIP parameter types
14. Acknowledgments
The drive to create HIP came to being after attending the MALLOC The drive to create HIP came to being after attending the MALLOC
meeting at IETF 43. Baiju Patel and Hilarie Orman really gave the meeting at the 43rd IETF meeting. Baiju Patel and Hilarie Orman
original author, Bob Moskowitz, the assist to get HIP beyond 5 really gave the original author, Bob Moskowitz, the assist to get HIP
paragraphs of ideas. It has matured considerably since the early beyond 5 paragraphs of ideas. It has matured considerably since the
drafts thanks to extensive input from IETFers. Most importantly, its early drafts thanks to extensive input from IETFers. Most
design goals are articulated and are different from other efforts in importantly, its design goals are articulated and are different from
this direction. Particular mention goes to the members of the other efforts in this direction. Particular mention goes to the
NameSpace Research Group of the IRTF. Noel Chiappa provided the members of the NameSpace Research Group of the IRTF. Noel Chiappa
framework for LSIs and Keith Moore the impetus to provide provided the framework for LSIs and Keith Moore the impetus to
resolvability. Steve Deering provided encouragement to keep working, provide resolvability. Steve Deering provided encouragement to keep
as a solid proposal can act as a proof of ideas for a research group. working, as a solid proposal can act as a proof of ideas for a
research group.
Many others contributed; extensive security tips were provided by Many others contributed; extensive security tips were provided by
Steve Bellovin. Rob Austein kept the DNS parts on track. Paul Kocher Steve Bellovin. Rob Austein kept the DNS parts on track. Paul
taught Bob Moskowitz how to make the cookie exchange expensive for Kocher taught Bob Moskowitz how to make the cookie exchange expensive
the Initiator to respond, but easy for the Responder to validate. for the Initiator to respond, but easy for the Responder to validate.
Bill Sommerfeld supplied the Birthday concept to simplify reboot Bill Sommerfeld supplied the Birthday concept, which later evolved
management. Rodney Thayer and Hugh Daniels provide extensive into the R1 generation counter, to simplify reboot management.
feedback. In the early times of this draft, John Gilmore kept Bob Rodney Thayer and Hugh Daniels provide extensive feedback. In the
Moskowitz challenged to provide something of value. early times of this draft, John Gilmore kept Bob Moskowitz challenged
to provide something of value.
During the later stages of this document, when the editing baton was During the later stages of this document, when the editing baton was
transfered to Pekka Nikander, the input from the early implementors transfered to Pekka Nikander, the input from the early implementors
were invaluable. Without having actual implementations, this were invaluable. Without having actual implementations, this
document would not be on the level it is now. document would not be on the level it is now.
In the usual IETF fashion, a large number of people have contributed In the usual IETF fashion, a large number of people have contributed
to the actual text or ideas. The list of these people include Jeff to the actual text or ideas. The list of these people include Jeff
Ahrenholz, Francis Dupont, Derek Fawcus, George Gross, Andrew Ahrenholz, Francis Dupont, Derek Fawcus, George Gross, Andrew
McGregor, Julien Laganier, Miika Komu, Mika Kousa, Jan Melen, Henrik McGregor, Julien Laganier, Miika Komu, Mika Kousa, Jan Melen, Henrik
Petander, Michael Richardson, Tim Shepard, Jorma Wall, and Jukka Petander, Michael Richardson, Tim Shepard, Jorma Wall, and Jukka
Ylitalo. Our apologies to anyone who's name is missing. Ylitalo. Our apologies to anyone whose name is missing.
16. References Once the HIP Working Group was founded in early 2004, a number of
changes were introduced through the working group process. Most
notably, the original draft was split in two, one containing the base
exchange and the other one defining how to use ESP.
16.1 Normative references 15. References
15.1 Normative references
[1] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August [1] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August
1980. 1980.
[2] Postel, J., "Internet Control Message Protocol", STD 5, RFC [2] Postel, J., "Internet Control Message Protocol", STD 5,
792, September 1981. RFC 792, September 1981.
[3] Mockapetris, P., "Domain names - implementation and [3] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[4] Conta, A. and S. Deering, "Internet Control Message Protocol [4] Conta, A. and S. Deering, "Internet Control Message Protocol
(ICMPv6) for the Internet Protocol Version 6 (IPv6)", RFC 1885, (ICMPv6) for the Internet Protocol Version 6 (IPv6)", RFC 1885,
December 1995. December 1995.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
skipping to change at page 90, line 44 skipping to change at page 84, line 44
[9] Orman, H., "The OAKLEY Key Determination Protocol", RFC 2412, [9] Orman, H., "The OAKLEY Key Determination Protocol", RFC 2412,
November 1998. November 1998.
[10] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher Algorithms", [10] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher Algorithms",
RFC 2451, November 1998. RFC 2451, November 1998.
[11] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) [11] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998. Specification", RFC 2460, December 1998.
[12] Eastlake, D., "Domain Name System Security Extensions", RFC [12] Eastlake, D., "Domain Name System Security Extensions",
2535, March 1999. RFC 2535, March 1999.
[13] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System [13] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System
(DNS)", RFC 2536, March 1999. (DNS)", RFC 2536, March 1999.
[14] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name [14] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name
System (DNS)", RFC 3110, May 2001. System (DNS)", RFC 3110, May 2001.
[15] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet X.509 [15] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet X.509
Public Key Infrastructure Certificate and Certificate Public Key Infrastructure Certificate and Certificate
Revocation List (CRL) Profile", RFC 3280, April 2002. Revocation List (CRL) Profile", RFC 3280, April 2002.
[16] Draves, R., "Default Address Selection for Internet Protocol [16] Draves, R., "Default Address Selection for Internet Protocol
version 6 (IPv6)", RFC 3484, February 2003. version 6 (IPv6)", RFC 3484, February 2003.
[17] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) [17] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
Addressing Architecture", RFC 3513, April 2003. Addressing Architecture", RFC 3513, April 2003.
[18] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) [18] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
Diffie-Hellman groups for Internet Key Exchange (IKE)", RFC Diffie-Hellman groups for Internet Key Exchange (IKE)",
3526, May 2003. RFC 3526, May 2003.
[19] Kent, S., "IP Encapsulating Security Payload (ESP)", [19] Kent, S., "IP Encapsulating Security Payload (ESP)",
draft-ietf-ipsec-esp-v3-05 (work in progress), April 2003. Internet-Draft draft-ietf-ipsec-esp-v3-05, April 2003.
[20] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", [20] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
draft-ietf-ipsec-ikev2-07 (work in progress), April 2003. Internet-Draft draft-ietf-ipsec-ikev2-07, April 2003.
[21] Moskowitz, R., "Host Identity Protocol Architecture", [21] Moskowitz, R., "Host Identity Protocol Architecture",
draft-moskowitz-hip-arch-03 (work in progress), May 2003. Internet-Draft draft-moskowitz-hip-arch-03, May 2003.
[22] NIST, "FIPS PUB 180-1: Secure Hash Standard", April 1995. [22] NIST, "FIPS PUB 180-1: Secure Hash Standard", April 1995.
16.2 Informative references [23] Jokela, P., Moskowitz, R. and P. Nikander, "Using ESP transport
format with HIP", Internet-Draft draft-jokela-hip-esp-00,
January 2005.
[23] Bellovin, S. and W. Aiello, "Just Fast Keying (JFK)", 15.2 Informative references
draft-ietf-ipsec-jfk-04 (work in progress), July 2002.
[24] Moskowitz, R. and P. Nikander, "Using Domain Name System (DNS) [24] Bellovin, S. and W. Aiello, "Just Fast Keying (JFK)",
with Host Identity Protocol (HIP)", draft-nikander-hip-dns-00 Internet-Draft draft-ietf-ipsec-jfk-04, July 2002.
(to be issued) (work in progress), June 2003.
[25] Nikander, P., "SPI assisted NAT traversal (SPINAT) with Host [25] Moskowitz, R. and P. Nikander, "Using Domain Name System (DNS)
Identity Protocol (HIP)", draft-nikander-hip-nat-00 (to be with Host Identity Protocol (HIP)",
issued) (work in progress), June 2003. Internet-Draft draft-nikander-hip-dns-00 (to be issued), June
2003.
[26] Crosby, SA. and DS. Wallach, "Denial of Service via Algorithmic [26] Nikander, P., "SPI assisted NAT traversal (SPINAT) with Host
Identity Protocol (HIP)",
Internet-Draft draft-nikander-hip-nat-00 (to be issued), June
2003.
[27] Crosby, SA. and DS. Wallach, "Denial of Service via Algorithmic
Complexity Attacks", in Proceedings of Usenix Security Complexity Attacks", in Proceedings of Usenix Security
Symposium 2003, Washington, DC., August 2003. Symposium 2003, Washington, DC., August 2003.
[27] Nikander, P., "A Bound End-to-End Tunnel (BEET) mode for ESP", [28] Nikander, P., "A Bound End-to-End Tunnel (BEET) mode for ESP",
draft-nikander-esp-beet-mode-00 (expired) (work in progress), Internet-Draft draft-nikander-esp-beet-mode-00 (expired), Oct
Oct 2003. 2003.
[29] Henderson, T., "Using HIP with Legacy Applications",
Internet-Draft draft-henderson-hip-applications-00.txt, Feb
2005.
Authors' Addresses Authors' Addresses
Robert Moskowitz Robert Moskowitz
ICSAlabs, a Division of TruSecure Corporation ICSAlabs, a Division of TruSecure Corporation
1000 Bent Creek Blvd, Suite 200 1000 Bent Creek Blvd, Suite 200
Mechanicsburg, PA Mechanicsburg, PA
USA USA
EMail: rgm@icsalabs.com Email: rgm@icsalabs.com
Pekka Nikander Pekka Nikander
Ericsson Research NomadicLab Ericsson Research NomadicLab
JORVAS FIN-02420 JORVAS FIN-02420
FINLAND FINLAND
Phone: +358 9 299 1 Phone: +358 9 299 1
EMail: pekka.nikander@nomadiclab.com Email: pekka.nikander@nomadiclab.com
Petri Jokela Petri Jokela
Ericsson Research NomadicLab Ericsson Research NomadicLab
JORVAS FIN-02420 JORVAS FIN-02420
FINLAND FINLAND
Phone: +358 9 299 1 Phone: +358 9 299 1
EMail: petri.jokela@nomadiclab.com Email: petri.jokela@nomadiclab.com
Thomas R. Henderson Thomas R. Henderson
The Boeing Company The Boeing Company
P.O. Box 3707 P.O. Box 3707
Seattle, WA Seattle, WA
USA USA
EMail: thomas.r.henderson@boeing.com Email: thomas.r.henderson@boeing.com
Appendix A. API issues
The following text is informational and may be expanded upon or
revised in a separate Informational document.
HIP may be used to support application data transfers in one of three
ways:
the application may be HIP-aware and may explicitly use a
HIP-based API and/or resolver library;
the application may not be HIP-aware but may be provided with HITs
or LSIs in place of IP addresses as part of the address resolution
process; and
the application may or may not be HIP-aware and may present IP
addresses to the system, but the system may decide to
opportunistically invoke HIP or use a pre-existing HIP-based SA on
its behalf.
The first case is the most straightforward. The HIP-based API is
outside the scope of this document.
The second case is one way to provide HIP support to non-HIP-aware
applications. HITs may be stored in the DNS or some other
infrastructure, and the resolver library may choose to supply a
querying application with a HIT or LSI in place of an IP address.
Note that if the application truly needs IP addresses for a domain
name for some reason (e.g., a diagnostic application, or for use in a
referral scenario to a non-HIP-based host), blindly providing HITs or
LSIs in place of actual IP addresses may cause some applications to
break.
In both of the first two cases, the means whereby a system can
resolve an LSI or HIT to an IP address, when such a mapping is not
locally cached in the system, is outside the scope of this document.
In the third case, the system is explicitly invoking HIP to a
particular destination IP address on the basis of a local policy
decision. This approach resembles the way that opportunistic IPsec
works. Effectively, this approach is implicitly associating IP
addresses with host identities, and is prone to certain failures or
ambiguity in an environment where IP addresses are dynamic (e.g., an
application connects to an IP address, the peer host moves at some
later time, then another host acquires the old IP address, and the
system again receives a request to connect to that IP address, in
which case it is ambiguous whether the application wants to connect
to the host previously at that IP address or the new host at that
address).
If HIP is used to support an application, the application data stream
may contain either IP addresses or LSIs or HITs in place of the IP
addresses.
Historically, the first two bits of a HIT were used to differentiate
between Type 1, Type 2, and IPv6 address formats. This was changed
in October 2004, when the Working Group decided that all (currently
defined) HITs are 128-bit long. Hence, a Type 1 HIT consists of 128
bits of the SHA-1 hash of the public key, and a Type 2 HIT consists
of a 64-bits long HAA field, followed by a 64-bits of the SHA-1 hash.
[The format of the HAA field is left undefined in this document.]
In this document, we additionally define an internal IPv6-compatible
LSI representation format, to be used within the legacy
IPv6-compatible API (e.g., socket over AF_INET6). The format of
these IPv6-compatible LSIs is designed to avoid the most commonly
occurring IPv6 addresses in RFC3596 [9]. An IPv6-compatible LSI
representation of a HIT can be easily computed by replacing the first
TBDth bits of the HIT by the TBD bits long prefix "0xTBD".
Accordingly, this specification also RECOMMENDS that conforming
implementations ignore the TBD prefix bits when comparing HITs for
equality; see Section 3.1.
Appendix B. Probabilities of HIT collisions Appendix A. Probabilities of HIT collisions
The birthday paradox sets a bound for the expectation of collisions. The birthday paradox sets a bound for the expectation of collisions.
It is based on the square root of the number of values. A 64-bit It is based on the square root of the number of values. A 64-bit
hash, then, would put the chances of a collision at 50-50 with 2^32 hash, then, would put the chances of a collision at 50-50 with 2^32
hosts (4 billion). A 1% chance of collision would occur in a hosts (4 billion). A 1% chance of collision would occur in a
population of 640M and a .001% collision chance in a 20M population. population of 640M and a .001% collision chance in a 20M population.
A 128 bit hash will have the same .001% collision chance in a 9x10^16 A 128 bit hash will have the same .001% collision chance in a 9x10^16
population. population.
Appendix C. Probabilities in the cookie calculation Appendix B. Probabilities in the cookie calculation
A question: Is it guaranteed that the Initiator is able to solve the A question: Is it guaranteed that the Initiator is able to solve the
puzzle in this way when the K value is large? puzzle in this way when the K value is large?
Answer: No, it is not guaranteed. But it is not guaranteed even in Answer: No, it is not guaranteed. But it is not guaranteed even in
the old mechanism, since the Initiator may start far away from J and the old mechanism, since the Initiator may start far away from J and
arrive to J after far too many steps. If we wanted to make sure that arrive to J after far too many steps. If we wanted to make sure that
the Initiator finds a value, we would need to give some hint of a the Initiator finds a value, we would need to give some hint of a
suitable J, and I don't think we want to do that. suitable J, and I don't think we want to do that.
In general, if we model the hash function with a random function, the In general, if we model the hash function with a random function, the
probability that one iteration gives are result with K zero bits is probability that one iteration gives are result with K zero bits is
2^-K. Thus, the probability that one iteration does *not* give K 2^-K. Thus, the probability that one iteration does _not_ give K
zero bits is (1 - 2^-K). Consequently, the probability that 2^K zero bits is (1 - 2^-K). Consequently, the probability that 2^K
iterations does not give K zero bits is (1 - 2^-K)^(2^K). iterations does not give K zero bits is (1 - 2^-K)^(2^K).
Since my calculus starts to be rusty, I made a small experiment and Since my calculus starts to be rusty, I made a small experiment and
found out that found out that
lim (1 - 2^-k)^(2^k) = 0.36788 lim (1 - 2^-k)^(2^k) = 0.36788
k->inf k->inf
lim (1 - 2^-k)^(2^(k+1)) = 0.13534 lim (1 - 2^-k)^(2^(k+1)) = 0.13534
skipping to change at page 97, line 5 skipping to change at page 89, line 5
lim (1 - 2^-k)^(2^(k+3)) = 0.000335 lim (1 - 2^-k)^(2^(k+3)) = 0.000335
k->inf k->inf
Thus, if hash functions were random functions, we would need about Thus, if hash functions were random functions, we would need about
2^(K+3) iterations to make sure that the probability of a failure is 2^(K+3) iterations to make sure that the probability of a failure is
less than 1% (actually less than 0.04%). Now, since my perhaps less than 1% (actually less than 0.04%). Now, since my perhaps
flawed understanding of hash functions is that they are "flatter" flawed understanding of hash functions is that they are "flatter"
than random functions, 2^(K+3) is probably an overkill. OTOH, the than random functions, 2^(K+3) is probably an overkill. OTOH, the
currently suggested 2^K is clearly too little. currently suggested 2^K is clearly too little.
Appendix D. Using responder cookies Appendix C. Using responder cookies
As mentioned in Section 4.1.1, the Responder may delay state creation As mentioned in Section 4.1.1, the Responder may delay state creation
and still reject most spoofed I2s by using a number of pre-calculated and still reject most spoofed I2s by using a number of pre-calculated
R1s and a local selection function. This appendix defines one R1s and a local selection function. This appendix defines one
possible implementation in detail. The purpose of this appendix is possible implementation in detail. The purpose of this appendix is
to give the implementors an idea on how to implement the mechanism. to give the implementors an idea on how to implement the mechanism.
The method described in this appendix SHOULD NOT be used in any real The method described in this appendix SHOULD NOT be used in any real
implementation. If the implementation is based on this appendix, it implementation. If the implementation is based on this appendix, it
SHOULD contain some local modification that makes an attacker's task SHOULD contain some local modification that makes an attacker's task
harder. harder.
skipping to change at page 100, line 5 skipping to change at page 92, line 5
changes in the HITs. Checking the HITs is not that essential, changes in the HITs. Checking the HITs is not that essential,
though, since HITs are included in the cookie computation, too. though, since HITs are included in the cookie computation, too.
The effectivity of the method can be varied by varying the size of The effectivity of the method can be varied by varying the size of
the array containing pre-computed R1s. If the array is large, the the array containing pre-computed R1s. If the array is large, the
probability that an I2 with a spoofed IP address or HIT happens to probability that an I2 with a spoofed IP address or HIT happens to
map to the same slot is fairly slow. However, a large array means map to the same slot is fairly slow. However, a large array means
that each R1 has a fairly long life time, thereby allowing an that each R1 has a fairly long life time, thereby allowing an
attacker to utilize one solved puzzle for a longer time. attacker to utilize one solved puzzle for a longer time.
Appendix E. Running HIP over IPv4 UDP Appendix D. Example checksums for HIP packets
In the IPv4 world, with the deployed NAT devices, it may make sense
to run HIP over UDP. When running HIP over UDP, the following packet
structure is used. The structure is followed by the HITs, as usual.
Both the Source and Destination port MUST be 272.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
| Source port | Destination port | \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ >UDP
| Length | Checksum | /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<
| HIP Controls | HIP pkt Type | Ver. | Res. | >HIP
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/
It is currently undefined how the actual data transfer, using ESP, is
handled. Plain ESP may not go through all NAT devices.
It is currently FORBIDDEN to use this packet format with IPv6.
Appendix F. Example checksums for HIP packets
The HIP checksum for HIP packets is specified in Section 6.1.2. The HIP checksum for HIP packets is specified in Section 6.1.2.
Checksums for TCP and UDP packets running over HIP-enabled security Checksums for TCP and UDP packets running over HIP-enabled security
associations are specified in Section 3.5. The examples below use IP associations are specified in Section 3.5. The examples below use IP
addresses of 192.168.0.1 and 192.168.0.2 (and their respective addresses of 192.168.0.1 and 192.168.0.2 (and their respective
IPv4-compatible IPv6 formats), and type 1 HITs with the first two IPv4-compatible IPv6 formats), and type 1 HITs with the first two
bits "01" followed by 124 zeroes followed by a decimal 1 or 2, bits "01" followed by 124 zeroes followed by a decimal 1 or 2,
respectively. respectively.
F.1 IPv6 HIP example (I1) D.1 IPv6 HIP example (I1)
Source Address: ::c0a8:0001 Source Address: ::c0a8:0001
Destination Address: ::c0a8:0002 Destination Address: ::c0a8:0002
Upper-Layer Packet Length: 40 0x28 Upper-Layer Packet Length: 40 0x28
Next Header: 99 0x63 Next Header: 99 0x63
Payload Protocol: 59 0x3b Payload Protocol: 59 0x3b
Header Length: 4 0x04 Header Length: 4 0x04
Packet Type: 1 0x01 Packet Type: 1 0x01
Version: 1 0x1 Version: 1 0x1
Reserved: 0 0x0 Reserved: 0 0x0
Control: 0 0x0000 Control: 0 0x0000
Checksum: 49672 0xc208 Checksum: 49672 0xc208
Sender's HIT: 4000::0001 Sender's HIT: 4000::0001
Receiver's HIT: 4000::0002 Receiver's HIT: 4000::0002
F.2 IPv4 HIP packet (I1) D.2 IPv4 HIP packet (I1)
The IPv4 checksum value for the same example I1 packet is the same as The IPv4 checksum value for the same example I1 packet is the same as
the IPv6 checksum (since the checksums due to the IPv4 and IPv6 the IPv6 checksum (since the checksums due to the IPv4 and IPv6
pseudo-header components are the same). pseudo-header components are the same).
F.3 TCP segment D.3 TCP segment
Regardless of whether IPv6 or IPv4 is used, the TCP and UDP sockets Regardless of whether IPv6 or IPv4 is used, the TCP and UDP sockets
use the IPv6 pseudo-header format [8], with the HITs used in place of use the IPv6 pseudo-header format [8], with the HITs used in place of
the IPv6 addresses. the IPv6 addresses.
Sender's HIT: 4000::0001 Sender's HIT: 4000::0001
Receiver's HIT: 4000::0002 Receiver's HIT: 4000::0002
Upper-Layer Packet Length: 20 0x14 Upper-Layer Packet Length: 20 0x14
Next Header: 6 0x06 Next Header: 6 0x06
Source port: 32769 0x8001 Source port: 32769 0x8001
Destination port: 22 0x0016 Destination port: 22 0x0016
Sequence number: 1 0x00000001 Sequence number: 1 0x00000001
Acknowledgment number: 0 0x00000000 Acknowledgment number: 0 0x00000000
Header length: 20 0x14 Header length: 20 0x14
Flags: SYN 0x02 Flags: SYN 0x02
Window size: 5840 0x16d0 Window size: 5840 0x16d0
Checksum: 54519 0xd4f7 Checksum: 54519 0xd4f7
Urgent pointer: 0 0x0000 Urgent pointer: 0 0x0000
Appendix G. 384-bit group Appendix E. 384-bit group
This 384-bit group is defined only to be used with HIP. NOTE: The This 384-bit group is defined only to be used with HIP. NOTE: The
security level of this group is very low! The encryption may be security level of this group is very low! The encryption may be
broken in a very short time, even real-time. It should be used only broken in a very short time, even real-time. It should be used only
when the host is not powerful enough (e.g. some PDAs) and when when the host is not powerful enough (e.g. some PDAs) and when
security requirements are low (e.g. during normal web surfing). security requirements are low (e.g. during normal web surfing).
This prime is: 2^384 - 2^320 - 1 + 2^64 * { [ 2^254 pi] + 5857 } This prime is: 2^384 - 2^320 - 1 + 2^64 * { [ 2^254 pi] + 5857 }
Its hexadecimal value is: Its hexadecimal value is:
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The generator is: 2. The generator is: 2.
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skipping to change at page 104, line 41 skipping to change at page 95, line 41
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except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
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Internet Society. Internet Society.
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