rfc5202.txt   draft-ietf-hip-rfc5202-bis-05.txt >
Network Working Group P. Jokela Network Working Group P. Jokela
Request for Comments: 5202 Ericsson Research NomadicLab Internet-Draft Ericsson Research NomadicLab
Category: Experimental R. Moskowitz Obsoletes: 5202 (if approved) R. Moskowitz
ICSAlabs Intended status: Standards Track ICSAlabs, An Independent
P. Nikander Expires: May 22, 2014 Division of Verizon Business
Systems
J. Melen
Ericsson Research NomadicLab Ericsson Research NomadicLab
April 2008 November 18, 2013
Using the Encapsulating Security Payload (ESP) Transport Format with the Using the Encapsulating Security Payload (ESP) Transport Format with the
Host Identity Protocol (HIP) Host Identity Protocol (HIP)
draft-ietf-hip-rfc5202-bis-05
Abstract
This memo specifies an Encapsulated Security Payload (ESP) based
mechanism for transmission of user data packets, to be used with the
Host Identity Protocol (HIP). This document obsoletes RFC 5202.
Status of This Memo Status of This Memo
This memo defines an Experimental Protocol for the Internet This Internet-Draft is submitted in full conformance with the
community. It does not specify an Internet standard of any kind. provisions of BCP 78 and BCP 79.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
IESG Note Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
The following issues describe IESG concerns about this document. The Internet-Drafts are draft documents valid for a maximum of six months
IESG expects that these issues will be addressed when future versions and may be updated, replaced, or obsoleted by other documents at any
of HIP are designed. time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
In case of complex Security Policy Databases (SPDs) and the co- This Internet-Draft will expire on May 22, 2014.
existence of HIP and security-related protocols such as IKE,
implementors may encounter conditions that are unspecified in these
documents. For example, when the SPD defines an IP address subnet to
be protected and a HIP host is residing in that IP address area,
there is a possibility that the communication is encrypted multiple
times. Readers are advised to pay special attention when running HIP
with complex SPD settings. Future specifications should clearly
define when multiple encryption is intended, and when it should be
avoided.
Abstract Copyright Notice
This memo specifies an Encapsulated Security Payload (ESP) based Copyright (c) 2013 IETF Trust and the persons identified as the
mechanism for transmission of user data packets, to be used with the document authors. All rights reserved.
Host Identity Protocol (HIP).
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Using ESP with HIP . . . . . . . . . . . . . . . . . . . . . . 4 3. Using ESP with HIP . . . . . . . . . . . . . . . . . . . . . . 5
3.1. ESP Packet Format . . . . . . . . . . . . . . . . . . . . 4 3.1. ESP Packet Format . . . . . . . . . . . . . . . . . . . . 5
3.2. Conceptual ESP Packet Processing . . . . . . . . . . . . . 4 3.2. Conceptual ESP Packet Processing . . . . . . . . . . . . . 5
3.2.1. Semantics of the Security Parameter Index (SPI) . . . 5 3.2.1. Semantics of the Security Parameter Index (SPI) . . . 6
3.3. Security Association Establishment and Maintenance . . . . 6 3.3. Security Association Establishment and Maintenance . . . . 7
3.3.1. ESP Security Associations . . . . . . . . . . . . . . 6 3.3.1. ESP Security Associations . . . . . . . . . . . . . . 7
3.3.2. Rekeying . . . . . . . . . . . . . . . . . . . . . . . 6 3.3.2. Rekeying . . . . . . . . . . . . . . . . . . . . . . . 7
3.3.3. Security Association Management . . . . . . . . . . . 7 3.3.3. Security Association Management . . . . . . . . . . . 8
3.3.4. Security Parameter Index (SPI) . . . . . . . . . . . . 7 3.3.4. Security Parameter Index (SPI) . . . . . . . . . . . . 8
3.3.5. Supported Transforms . . . . . . . . . . . . . . . . . 7 3.3.5. Supported Ciphers . . . . . . . . . . . . . . . . . . 9
3.3.6. Sequence Number . . . . . . . . . . . . . . . . . . . 8 3.3.6. Sequence Number . . . . . . . . . . . . . . . . . . . 9
3.3.7. Lifetimes and Timers . . . . . . . . . . . . . . . . . 8 3.3.7. Lifetimes and Timers . . . . . . . . . . . . . . . . . 9
3.4. IPsec and HIP ESP Implementation Considerations . . . . . 8 3.4. IPsec and HIP ESP Implementation Considerations . . . . . 9
4. The Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4.1. Data Packet Processing Considerations . . . . . . . . 10
4.1. ESP in HIP . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4.2. HIP Signaling Packet Considerations . . . . . . . . . 10
4.1.1. Setting Up an ESP Security Association . . . . . . . . 9 4. The Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.2. Updating an Existing ESP SA . . . . . . . . . . . . . 10 4.1. ESP in HIP . . . . . . . . . . . . . . . . . . . . . . . . 11
5. Parameter and Packet Formats . . . . . . . . . . . . . . . . . 10 4.1.1. IPsec ESP Transport Format Type . . . . . . . . . . . 11
5.1. New Parameters . . . . . . . . . . . . . . . . . . . . . . 11 4.1.2. Setting Up an ESP Security Association . . . . . . . . 11
5.1.1. ESP_INFO . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.3. Updating an Existing ESP SA . . . . . . . . . . . . . 12
5.1.2. ESP_TRANSFORM . . . . . . . . . . . . . . . . . . . . 13 5. Parameter and Packet Formats . . . . . . . . . . . . . . . . . 13
5.1.3. NOTIFY Parameter . . . . . . . . . . . . . . . . . . . 14 5.1. New Parameters . . . . . . . . . . . . . . . . . . . . . . 13
5.2. HIP ESP Security Association Setup . . . . . . . . . . . . 14 5.1.1. ESP_INFO . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.1. Setup During Base Exchange . . . . . . . . . . . . . . 14 5.1.2. ESP_TRANSFORM . . . . . . . . . . . . . . . . . . . . 15
5.3. HIP ESP Rekeying . . . . . . . . . . . . . . . . . . . . . 16 5.1.3. NOTIFICATION Parameter . . . . . . . . . . . . . . . . 16
5.3.1. Initializing Rekeying . . . . . . . . . . . . . . . . 16 5.2. HIP ESP Security Association Setup . . . . . . . . . . . . 16
5.3.2. Responding to the Rekeying Initialization . . . . . . 17 5.2.1. Setup During Base Exchange . . . . . . . . . . . . . . 16
5.4. ICMP Messages . . . . . . . . . . . . . . . . . . . . . . 17 5.3. HIP ESP Rekeying . . . . . . . . . . . . . . . . . . . . . 18
5.4.1. Unknown SPI . . . . . . . . . . . . . . . . . . . . . 17 5.3.1. Initializing Rekeying . . . . . . . . . . . . . . . . 18
6. Packet Processing . . . . . . . . . . . . . . . . . . . . . . 18 5.3.2. Responding to the Rekeying Initialization . . . . . . 19
6.1. Processing Outgoing Application Data . . . . . . . . . . . 18 5.4. ICMP Messages . . . . . . . . . . . . . . . . . . . . . . 19
6.2. Processing Incoming Application Data . . . . . . . . . . . 19 5.4.1. Unknown SPI . . . . . . . . . . . . . . . . . . . . . 19
6.3. HMAC and SIGNATURE Calculation and Verification . . . . . 19 6. Packet Processing . . . . . . . . . . . . . . . . . . . . . . 20
6.4. Processing Incoming ESP SA Initialization (R1) . . . . . . 19 6.1. Processing Outgoing Application Data . . . . . . . . . . . 20
6.5. Processing Incoming Initialization Reply (I2) . . . . . . 20 6.2. Processing Incoming Application Data . . . . . . . . . . . 20
6.6. Processing Incoming ESP SA Setup Finalization (R2) . . . . 20 6.3. HMAC and SIGNATURE Calculation and Verification . . . . . 21
6.7. Dropping HIP Associations . . . . . . . . . . . . . . . . 20 6.4. Processing Incoming ESP SA Initialization (R1) . . . . . . 21
6.8. Initiating ESP SA Rekeying . . . . . . . . . . . . . . . . 20 6.5. Processing Incoming Initialization Reply (I2) . . . . . . 22
6.9. Processing Incoming UPDATE Packets . . . . . . . . . . . . 22 6.6. Processing Incoming ESP SA Setup Finalization (R2) . . . . 22
6.7. Dropping HIP Associations . . . . . . . . . . . . . . . . 22
6.8. Initiating ESP SA Rekeying . . . . . . . . . . . . . . . . 22
6.9. Processing Incoming UPDATE Packets . . . . . . . . . . . . 24
6.9.1. Processing UPDATE Packet: No Outstanding Rekeying 6.9.1. Processing UPDATE Packet: No Outstanding Rekeying
Request . . . . . . . . . . . . . . . . . . . . . . . 22 Request . . . . . . . . . . . . . . . . . . . . . . . 24
6.10. Finalizing Rekeying . . . . . . . . . . . . . . . . . . . 23 6.10. Finalizing Rekeying . . . . . . . . . . . . . . . . . . . 25
6.11. Processing NOTIFY Packets . . . . . . . . . . . . . . . . 24 6.11. Processing NOTIFY Packets . . . . . . . . . . . . . . . . 26
7. Keying Material . . . . . . . . . . . . . . . . . . . . . . . 24 7. Keying Material . . . . . . . . . . . . . . . . . . . . . . . 26
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25 8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11.1. Normative references . . . . . . . . . . . . . . . . . . . 26 11.1. Normative references . . . . . . . . . . . . . . . . . . . 28
11.2. Informative references . . . . . . . . . . . . . . . . . . 26 11.2. Informative references . . . . . . . . . . . . . . . . . . 29
Appendix A. A Note on Implementation Options . . . . . . . . . . 28 Appendix A. A Note on Implementation Options . . . . . . . . . . 30
Appendix B. Bound End-to-End Tunnel mode for ESP . . . . . . . . 30
B.1. Protocol definition . . . . . . . . . . . . . . . . . . . 31
B.1.1. Changes to Security Association data structures . . . 31
B.1.2. Packet format . . . . . . . . . . . . . . . . . . . . 31
B.1.3. Cryptographic processing . . . . . . . . . . . . . . . 33
B.1.4. IP header processing . . . . . . . . . . . . . . . . . 33
B.1.5. Handling of outgoing packets . . . . . . . . . . . . . 34
B.1.6. Handling of incoming packets . . . . . . . . . . . . . 35
B.1.7. IPv4 options handling . . . . . . . . . . . . . . . . 35
1. Introduction 1. Introduction
In the Host Identity Protocol Architecture [RFC4423], hosts are In the Host Identity Protocol Architecture
identified with public keys. The Host Identity Protocol [RFC5201] [I-D.ietf-hip-rfc4423-bis], hosts are identified with public keys.
base exchange allows any two HIP-supporting hosts to authenticate The Host Identity Protocol [I-D.ietf-hip-rfc5201-bis] base exchange
each other and to create a HIP association between themselves. allows any two HIP-supporting hosts to authenticate each other and to
During the base exchange, the hosts generate a piece of shared keying create a HIP association between themselves. During the base
material using an authenticated Diffie-Hellman exchange. exchange, the hosts generate a piece of shared keying material using
an authenticated Diffie-Hellman exchange.
The HIP base exchange specification [RFC5201] does not describe any The HIP base exchange specification [I-D.ietf-hip-rfc5201-bis] does
transport formats or methods for user data to be used during the not describe any transport formats or methods for user data to be
actual communication; it only defines that it is mandatory to used during the actual communication; it only defines that it is
implement the Encapsulated Security Payload (ESP) [RFC4303] based mandatory to implement the Encapsulated Security Payload (ESP)
transport format and method. This document specifies how ESP is used [RFC4303] based transport format and method. This document specifies
with HIP to carry actual user data. how ESP is used with HIP to carry actual user data.
To be more specific, this document specifies a set of HIP protocol To be more specific, this document specifies a set of HIP protocol
extensions and their handling. Using these extensions, a pair of ESP extensions and their handling. Using these extensions, a pair of ESP
Security Associations (SAs) is created between the hosts during the Security Associations (SAs) is created between the hosts during the
base exchange. The resulting ESP Security Associations use keys base exchange. The resulting ESP Security Associations use keys
drawn from the keying material (KEYMAT) generated during the base drawn from the keying material (KEYMAT) generated during the base
exchange. After the HIP association and required ESP SAs have been exchange. After the HIP association and required ESP SAs have been
established between the hosts, the user data communication is established between the hosts, the user data communication is
protected using ESP. In addition, this document specifies methods to protected using ESP. In addition, this document specifies methods to
update an existing ESP Security Association. update an existing ESP Security Association.
It should be noted that representations of Host Identity are not It should be noted that representations of Host Identity are not
carried explicitly in the headers of user data packets. Instead, the carried explicitly in the headers of user data packets. Instead, the
ESP Security Parameter Index (SPI) is used to indicate the right host ESP Security Parameter Index (SPI) is used to indicate the right host
context. The SPIs are selected during the HIP ESP setup exchange. context. The SPIs are selected during the HIP ESP setup exchange.
For user data packets, ESP SPIs (in possible combination with IP For user data packets, ESP SPIs (in possible combination with IP
addresses) are used indirectly to identify the host context, thereby addresses) are used indirectly to identify the host context, thereby
avoiding any additional explicit protocol headers. avoiding any additional explicit protocol headers.
HIP and ESP traffic have known issues with middlebox traversal RFC
5207 [RFC5207]. Other specifications exist for operating HIP and ESP
over UDP (RFC 5770 [RFC5770] is an experimental specification, and
others are being developed). Middlebox traversal is out of scope for
this document.
This document obsoletes RFC 5202.
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 RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. Using ESP with HIP 3. Using ESP with HIP
The HIP base exchange is used to set up a HIP association between two The HIP base exchange is used to set up a HIP association between two
hosts. The base exchange provides two-way host authentication and hosts. The base exchange provides two-way host authentication and
key material generation, but it does not provide any means for key material generation, but it does not provide any means for
protecting data communication between the hosts. In this document, protecting data communication between the hosts. In this document,
we specify the use of ESP for protecting user data traffic after the we specify the use of ESP for protecting user data traffic after the
HIP base exchange. Note that this use of ESP is intended only for HIP base exchange. Note that this use of ESP is intended only for
host-to-host traffic; security gateways are not supported. host-to-host traffic; security gateways are not supported.
To support ESP use, the HIP base exchange messages require some minor To support ESP use, the HIP base exchange messages require some minor
additions to the parameters transported. In the R1 packet, the additions to the parameters transported. In the R1 packet, the
Responder adds the possible ESP transforms in a new ESP_TRANSFORM Responder adds the possible ESP transforms in an ESP_TRANSFORM
parameter before sending it to the Initiator. The Initiator gets the parameter before sending it to the Initiator. The Initiator gets the
proposed transforms, selects one of those proposed transforms, and proposed transforms, selects one of those proposed transforms, and
adds it to the I2 packet in an ESP_TRANSFORM parameter. In this I2 adds it to the I2 packet in an ESP_TRANSFORM parameter. In this I2
packet, the Initiator also sends the SPI value that it wants to be packet, the Initiator also sends the SPI value that it wants to be
used for ESP traffic flowing from the Responder to the Initiator. used for ESP traffic flowing from the Responder to the Initiator.
This information is carried using the new ESP_INFO parameter. When This information is carried using the ESP_INFO parameter. When
finalizing the ESP SA setup, the Responder sends its SPI value to the finalizing the ESP SA setup, the Responder sends its SPI value to the
Initiator in the R2 packet, again using ESP_INFO. Initiator in the R2 packet, again using ESP_INFO.
3.1. ESP Packet Format 3.1. ESP Packet Format
The ESP specification [RFC4303] defines the ESP packet format for The ESP specification [RFC4303] defines the ESP packet format for
IPsec. The HIP ESP packet looks exactly the same as the IPsec ESP IPsec. The HIP ESP packet looks exactly the same as the IPsec ESP
transport format packet. The semantics, however, are a bit different transport format packet. The semantics, however, are a bit different
and are described in more detail in the next subsection. and are described in more detail in the next subsection.
3.2. Conceptual ESP Packet Processing 3.2. Conceptual ESP Packet Processing
ESP packet processing can be implemented in different ways in HIP. ESP packet processing can be implemented in different ways in HIP.
It is possible to implement it in a way that a standards compliant, It is possible to implement it in a way that a standards compliant,
unmodified IPsec implementation [RFC4303] can be used. unmodified IPsec implementation [RFC4303] can be used in conjunction
with some additional transport checksum processing above it, and if
IP addresses are used as indexes to the right host context.
When a standards compliant IPsec implementation that uses IP When a standards compliant IPsec implementation that uses IP
addresses in the SPD and Security Association Database (SAD) is used, addresses in the SPD and Security Association Database (SAD) is used,
the packet processing may take the following steps. For outgoing the packet processing may take the following steps. For outgoing
packets, assuming that the upper-layer pseudoheader has been built packets, assuming that the upper-layer pseudoheader has been built
using IP addresses, the implementation recalculates upper-layer using IP addresses, the implementation recalculates upper-layer
checksums using Host Identity Tags (HITs) and, after that, changes checksums using Host Identity Tags (HITs) and, after that, changes
the packet source and destination addresses back to corresponding IP the packet source and destination addresses back to corresponding IP
addresses. The packet is sent to the IPsec ESP for transport mode addresses. The packet is sent to the IPsec ESP for transport mode
handling and from there the encrypted packet is sent to the network. handling and from there the encrypted packet is sent to the network.
When an ESP packet is received, the packet is first put to the IPsec When an ESP packet is received, the packet is first put to the IPsec
ESP transport mode handling, and after decryption, the source and ESP transport mode handling, and after decryption, the source and
destination IP addresses are replaced with HITs and finally, upper- destination IP addresses are replaced with HITs and finally, upper-
layer checksums are verified before passing the packet to the upper layer checksums are verified before passing the packet to the upper
layer. layer.
An alternative way to implement packet processing is the BEET (Bound An alternative way to implement packet processing is the BEET (Bound
End-to-End Tunnel) [ESP-BEET] mode. In BEET mode, the ESP packet is End-to-End Tunnel) mode (see Appendix B). In BEET mode, the ESP
formatted as a transport mode packet, but the semantics of the packet is formatted as a transport mode packet, but the semantics of
connection are the same as for tunnel mode. The "outer" addresses of the connection are the same as for tunnel mode. The "outer"
the packet are the IP addresses and the "inner" addresses are the addresses of the packet are the IP addresses and the "inner"
HITs. For outgoing traffic, after the packet has been encrypted, the addresses are the HITs. For outgoing traffic, after the packet has
packet's IP header is changed to a new one that contains IP addresses been encrypted, the packet's IP header is changed to a new one that
instead of HITs, and the packet is sent to the network. When the ESP contains IP addresses instead of HITs, and the packet is sent to the
packet is received, the SPI value, together with the integrity network. When the ESP packet is received, the SPI value, together
protection, allow the packet to be securely associated with the right with the integrity protection, allow the packet to be securely
HIT pair. The packet header is replaced with a new header containing associated with the right HIT pair. The packet header is replaced
HITs, and the packet is decrypted. with a new header containing HITs, and the packet is decrypted. BEET
mode is completely internal for host and doesn't require that the
corresponding host implements it, instead the corresponding host can
have ESP transport mode and do HIT IP conversions outside ESP.
3.2.1. Semantics of the Security Parameter Index (SPI) 3.2.1. Semantics of the Security Parameter Index (SPI)
SPIs are used in ESP to find the right Security Association for SPIs are used in ESP to find the right Security Association for
received packets. The ESP SPIs have added significance when used received packets. The ESP SPIs have added significance when used
with HIP; they are a compressed representation of a pair of HITs. with HIP; they are a compressed representation of a pair of HITs.
Thus, SPIs MAY be used by intermediary systems in providing services Thus, SPIs MAY be used by intermediary systems in providing services
like address mapping. Note that since the SPI has significance at like address mapping. Note that since the SPI has significance at
the receiver, only the < DST, SPI >, where DST is a destination IP the receiver, only the < DST, SPI >, where DST is a destination IP
address, uniquely identifies the receiver HIT at any given point of address, uniquely identifies the receiver HIT at any given point of
time. The same SPI value may be used by several hosts. A single time. The same SPI value may be used by several hosts. A single <
< DST, SPI > value may denote different hosts and contexts at DST, SPI > value may denote different hosts and contexts at different
different points of time, depending on the host that is currently points of time, depending on the host that is currently reachable at
reachable at the DST. the DST.
Each host selects for itself the SPI it wants to see in packets 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 received from its peer. This allows it to select different SPIs for
different peers. The SPI selection SHOULD be random; the rules of different peers. The SPI selection SHOULD be random; the rules of
Section 2.1 of the ESP specification [RFC4303] must be followed. A Section 2.1 of the ESP specification [RFC4303] must be followed. A
different SPI SHOULD be used for each HIP exchange with a particular different SPI SHOULD be used for each HIP exchange with a particular
host; this is to avoid a replay attack. Additionally, when a host host; this is to avoid a replay attack. Additionally, when a host
rekeys, the SPI MUST be changed. Furthermore, if a host changes over rekeys, the SPI MUST be changed. Furthermore, if a host changes over
to use a different IP address, it MAY change the SPI. to use a different IP address, it MAY change the SPI.
skipping to change at page 6, line 10 skipping to change at page 7, line 12
The selected SPI is communicated to the peer in the third (I2) and 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 fourth (R2) packets of the base HIP exchange. Changes in SPI are
signaled with ESP_INFO parameters. signaled with ESP_INFO parameters.
3.3. Security Association Establishment and Maintenance 3.3. Security Association Establishment and Maintenance
3.3.1. ESP Security Associations 3.3.1. ESP Security Associations
In HIP, ESP Security Associations are setup between the HIP nodes In HIP, ESP Security Associations are setup between the HIP nodes
during the base exchange [RFC5201]. Existing ESP SAs can be updated during the base exchange [I-D.ietf-hip-rfc5201-bis]. Existing ESP
later using UPDATE messages. The reason for updating the ESP SA SAs can be updated later using UPDATE messages. The reason for
later can be, for example, a need for rekeying the SA because of updating the ESP SA later can be, for example, a need for rekeying
sequence number rollover. the SA because of sequence number rollover.
Upon setting up a HIP association, each association is linked to two Upon setting up a HIP association, each association is linked to two
ESP SAs, one for incoming packets and one for outgoing packets. The ESP SAs, one for incoming packets and one for outgoing packets. The
Initiator's incoming SA corresponds with the Responder's outgoing Initiator's incoming SA corresponds with the Responder's outgoing
one, and vice versa. The Initiator defines the SPI for its incoming one, and vice versa. The Initiator defines the SPI for its incoming
association, as defined in Section 3.2.1. This SA is herein called association, as defined in Section 3.2.1. This SA is herein called
SA-RI, and the corresponding SPI is called SPI-RI. Respectively, the SA-RI, and the corresponding SPI is called SPI-RI. Respectively, the
Responder's incoming SA corresponds with the Initiator's outgoing SA Responder's incoming SA corresponds with the Initiator's outgoing SA
and is called SA-IR, with the SPI being called SPI-IR. and is called SA-IR, with the SPI being called SPI-IR.
skipping to change at page 6, line 35 skipping to change at page 7, line 37
sending out the I2, as explained in Section 6.4. The keys are sending out the I2, as explained in Section 6.4. The keys are
derived from KEYMAT, as defined in Section 7. The Responder creates derived from KEYMAT, as defined in Section 7. The Responder creates
SA-RI as a part of I2 processing; see Section 6.5. SA-RI as a part of I2 processing; see Section 6.5.
The Responder creates SA-IR as a part of I2 processing, before The Responder creates SA-IR as a part of I2 processing, before
sending out R2; see Section 6.5. The Initiator creates SA-IR when sending out R2; see Section 6.5. The Initiator creates SA-IR when
processing R2; see Section 6.6. processing R2; see Section 6.6.
The initial session keys are drawn from the generated keying The initial session keys are drawn from the generated keying
material, KEYMAT, after the HIP keys have been drawn as specified in material, KEYMAT, after the HIP keys have been drawn as specified in
[RFC5201]. [I-D.ietf-hip-rfc5201-bis].
When the HIP association is removed, the related ESP SAs MUST also be When the HIP association is removed, the related ESP SAs MUST also be
removed. removed.
3.3.2. Rekeying 3.3.2. Rekeying
After the initial HIP base exchange and SA establishment, both hosts After the initial HIP base exchange and SA establishment, both hosts
are in the ESTABLISHED state. There are no longer Initiator and are in the ESTABLISHED state. There are no longer Initiator and
Responder roles and the association is symmetric. In this Responder roles and the association is symmetric. In this
subsection, the party that initiates the rekey procedure is denoted subsection, the party that initiates the rekey procedure is denoted
skipping to change at page 7, line 41 skipping to change at page 8, line 43
An SA pair is indexed by the 2 SPIs and 2 HITs (both local and remote An SA pair is indexed by the 2 SPIs and 2 HITs (both local and remote
HITs since a system can have more than one HIT). An inactivity timer 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 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. SA, a timer is set to allow for any late arriving packets.
3.3.4. Security Parameter Index (SPI) 3.3.4. Security Parameter Index (SPI)
The SPIs in ESP provide a simple compression of the HIP data from all 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 packets after the HIP exchange. This does require a per HIT-pair
Security Association (and SPI), and a decrease of policy granularity Security Association (and SPI), and a decrease of policy granularity
over other Key Management Protocols like IKE. over other Key Management Protocols like Internet Key Exchange (IKE)
[RFC5996].
When a host updates the ESP SA, it provides a new inbound SPI to and When a host updates the ESP SA, it provides a new inbound SPI to and
gets a new outbound SPI from its partner. gets a new outbound SPI from its peer.
3.3.5. Supported Transforms 3.3.5. Supported Ciphers
All HIP implementations MUST support AES-CBC [RFC3602] and HMAC-SHA- All HIP implementations MUST support AES-128-CBC and AES-256-CBC
1-96 [RFC2404]. If the Initiator does not support any of the [RFC3602]. If the Initiator does not support any of the transforms
transforms offered by the Responder, it should abandon the offered by the Responder, it should abandon the negotiation and
negotiation and inform the peer with a NOTIFY message about a non- inform the peer with a NOTIFY message about a non-supported
supported transform. transform.
In addition to AES-CBC, all implementations MUST implement the ESP In addition to AES-128-CBC, all implementations MUST implement the
NULL encryption algorithm. When the ESP NULL encryption is used, it ESP NULL encryption algorithm. When the ESP NULL encryption is used,
MUST be used together with SHA1 or MD5 authentication as specified in it MUST be used together with SHA-256 authentication as specified in
Section 5.1.2 Section 5.1.2
3.3.6. Sequence Number 3.3.6. Sequence Number
The Sequence Number field is MANDATORY when ESP is used with HIP. The Sequence Number field is MANDATORY when ESP is used with HIP.
Anti-replay protection MUST be used in an ESP SA established with Anti-replay protection MUST be used in an ESP SA established with
HIP. When ESP is used with HIP, a 64-bit sequence number MUST be HIP. When ESP is used with HIP, a 64-bit sequence number MUST be
used. This means that each host MUST rekey before its sequence used. This means that each host MUST rekey before its sequence
number reaches 2^64. number reaches 2^64.
When using a 64-bit sequence number, the higher 32 bits are NOT When using a 64-bit sequence number, the higher 32 bits are NOT
included in the ESP header, but are simply kept local to both peers. included in the ESP header, but are simply kept local to both peers.
See [RFC4301]. See [RFC4301].
3.3.7. Lifetimes and Timers 3.3.7. Lifetimes and Timers
HIP does not negotiate any lifetimes. All ESP lifetimes are local HIP does not negotiate any lifetimes. All ESP lifetimes are local
policy. The only lifetimes a HIP implementation MUST support are policy. The only lifetimes a HIP implementation MUST support are
sequence number rollover (for replay protection), and SHOULD support sequence number rollover (for replay protection), and SHOULD support
timing out inactive ESP SAs. An SA times out if no packets are timing out inactive ESP SAs. An SA times out if no packets are
received using that SA. The default timeout value is 15 minutes. received using that SA. Implementations SHOULD support a
Implementations MAY support lifetimes for the various ESP transforms. configurable SA timeout value. Implementations MAY support lifetimes
Each implementation SHOULD implement per-HIT configuration of the for the various ESP transforms. Each implementation SHOULD implement
inactivity timeout, allowing statically configured HIP associations per-HIT configuration of the inactivity timeout, allowing statically
to stay alive for days, even when inactive. configured HIP associations to stay alive for days, even when
inactive.
3.4. IPsec and HIP ESP Implementation Considerations 3.4. IPsec and HIP ESP Implementation Considerations
When HIP is run on a node where a standards compliant IPsec is used, When HIP is run on a node where a standards compliant IPsec is used,
some issues have to be considered. some issues have to be considered.
The HIP implementation must be able to co-exist with other IPsec The HIP implementation must be able to co-exist with other IPsec
keying protocols. When the HIP implementation selects the SPI value, keying protocols. When the HIP implementation selects the SPI value,
it may lead to a collision if not implemented properly. To avoid the it may lead to a collision if not implemented properly. To avoid the
possibility for a collision, the HIP implementation MUST ensure that possibility for a collision, the HIP implementation MUST ensure that
the SPI values used for HIP SAs are not used for IPsec or other SAs, the SPI values used for HIP SAs are not used for IPsec or other SAs,
and vice versa. and vice versa.
Incoming packets using an SA that is not negotiated by HIP MUST NOT
be processed as described in Section 3.2, paragraph 2. The SPI will
identify the correct SA for packet decryption and MUST be used to
identify that the packet has an upper-layer checksum that is
calculated as specified in [I-D.ietf-hip-rfc5201-bis].
3.4.1. Data Packet Processing Considerations
For outbound traffic, the SPD or (coordinated) SPDs if there are two For outbound traffic, the SPD or (coordinated) SPDs if there are two
(one for HIP and one for IPsec) MUST ensure that packets intended for (one for HIP and one for IPsec) MUST ensure that packets intended for
HIP processing are given a HIP-enabled SA and that packets intended HIP processing are given a HIP-enabled SA and that packets intended
for IPsec processing are given an IPsec-enabled SA. The SP then MUST for IPsec processing are given an IPsec-enabled SA. The SP then MUST
be bound to the matching SA and non-HIP packets will not be processed be bound to the matching SA and non-HIP packets will not be processed
by this SA. Data originating from a socket that is not using HIP by this SA. Data originating from a socket that is not using HIP
MUST NOT have checksum recalculated (as described in Section 3.2, MUST NOT have checksum recalculated (as described in Section 3.2,
paragraph 2) and data MUST NOT be passed to the SP or SA created by paragraph 2) and data MUST NOT be passed to the SP or SA created by
the HIP. the HIP.
Incoming data packets using an SA that is not negotiated by HIP MUST It is possible that in case of overlapping policies, the outgoing
NOT be processed as described in Section 3.2, paragraph 2. The SPI packet would be handled both by the IPsec and HIP. In this case, it
will identify the correct SA for packet decryption and MUST be used is possible that the HIP association is end-to-end, while the IPsec
to identify that the packet has an upper-layer checksum that is SA is for encryption between the HIP host and a Security Gateway. In
calculated as specified in [RFC5201]. case of a Security Gateway ESP association, the ESP uses always
tunnel mode.
In case of IPsec tunnel mode, it is hard to see during the HIP SA
processing if the IPsec ESP SA has the same final destination. Thus,
traffic MUST be encrypted both with the HIP ESP SA and with the IPsec
SA when the IPsec ESP SA is used in tunnel mode.
In case of IPsec transport mode, the connection end-points are the
same. However, for HIP data packets it is not possible to avoid HIP
SA processing, while mapping the HIP data packet's IP addresses to
the corresponding HITs requires SPI values from the ESP header. In
case of transport mode IPsec SA, the IPsec encryption MAY be skipped
to avoid double encryption, if the local policy allows.
3.4.2. HIP Signaling Packet Considerations
In general, HIP signaling packets should follow the same processing
as HIP data packets.
In case of IPsec tunnel mode, the HIP signaling packets are always
encrypted using IPsec ESP SA. Note, that this hides the HIP
signaling packets from the eventual HIP middle boxes on the path
between the originating host and the Security Gateway.
In case of IPsec transport mode, the HIP signaling packets MAY skip
the IPsec ESP SA encryption if the local policy allows. This allows
the eventual HIP middle boxes to handle the passing HIP signaling
packets.
4. The Protocol 4. The Protocol
In this section, the protocol for setting up an ESP association to be In this section, the protocol for setting up an ESP association to be
used with HIP association is described. used with HIP association is described.
4.1. ESP in HIP 4.1. ESP in HIP
4.1.1. Setting Up an ESP Security Association 4.1.1. IPsec ESP Transport Format Type
The HIP handshake signals the TRANSPORT_FORMAT_LIST parameter in the
R1 and I2 messages. This parameter contains a list of the supported
HIP transport formats of the sending host in the order of preference.
The transport format type for IPsec ESP is the type number of the
ESP_TRANSFORM parameter, i.e., 4095.
4.1.2. Setting Up an ESP Security Association
Setting up an ESP Security Association between hosts using HIP Setting up an ESP Security Association between hosts using HIP
consists of three messages passed between the hosts. The parameters consists of three messages passed between the hosts. The parameters
are included in R1, I2, and R2 messages during base exchange. are included in R1, I2, and R2 messages during base exchange.
Initiator Responder Initiator Responder
I1 I1
----------------------------------> ---------------------------------->
skipping to change at page 9, line 48 skipping to change at page 12, line 6
<---------------------------------- <----------------------------------
Setting up an ESP Security Association between HIP hosts requires Setting up an ESP Security Association between HIP hosts requires
three messages to exchange the information that is required during an three messages to exchange the information that is required during an
ESP communication. ESP communication.
The R1 message contains the ESP_TRANSFORM parameter, in which the The R1 message contains the ESP_TRANSFORM parameter, in which the
sending host defines the possible ESP transforms it is willing to use sending host defines the possible ESP transforms it is willing to use
for the ESP SA. for the ESP SA.
Including the ESP_TRANSFORM parameter in the R1 message adds clarity
to the TRANSPORT_FORMAT_LIST, but may initiate negotiations for
possibly unselected transforms. However, resource-constrained
devices will most likely restrict support to a single transform for
the sake of minimizing ROM overhead and the additional parameter adds
negligible overhead with unconstrained devices.
The I2 message contains the response to an ESP_TRANSFORM received in The I2 message contains the response to an ESP_TRANSFORM received in
the R1 message. The sender must select one of the proposed ESP the R1 message. The sender must select one of the proposed ESP
transforms from the ESP_TRANSFORM parameter in the R1 message and transforms from the ESP_TRANSFORM parameter in the R1 message and
include the selected one in the ESP_TRANSFORM parameter in the I2 include the selected one in the ESP_TRANSFORM parameter in the I2
packet. In addition to the transform, the host includes the ESP_INFO packet. In addition to the transform, the host includes the ESP_INFO
parameter containing the SPI value to be used by the peer host. parameter containing the SPI value to be used by the peer host.
In the R2 message, the ESP SA setup is finalized. The packet In the R2 message, the ESP SA setup is finalized. The packet
contains the SPI information required by the Initiator for the ESP contains the SPI information required by the Initiator for the ESP
SA. SA.
4.1.2. Updating an Existing ESP SA 4.1.3. Updating an Existing ESP SA
The update process is accomplished using two messages. The HIP The update process is accomplished using two messages. The HIP
UPDATE message is used to update the parameters of an existing ESP UPDATE message is used to update the parameters of an existing ESP
SA. The UPDATE mechanism and message is defined in [RFC5201], and SA. The UPDATE mechanism and message is defined in
the additional parameters for updating an existing ESP SA are [I-D.ietf-hip-rfc5201-bis], and the additional parameters for
described here. updating an existing ESP SA are described here.
The following picture shows a typical exchange when an existing ESP The following picture shows a typical exchange when an existing ESP
SA is updated. Messages include SEQ and ACK parameters required by SA is updated. Messages include SEQ and ACK parameters required by
the UPDATE mechanism. the UPDATE mechanism.
H1 H2 H1 H2
UPDATE: SEQ, ESP_INFO [, DIFFIE_HELLMAN] UPDATE: SEQ, ESP_INFO [, DIFFIE_HELLMAN]
-----------------------------------------------------> ----------------------------------------------------->
UPDATE: SEQ, ACK, ESP_INFO [, DIFFIE_HELLMAN] UPDATE: SEQ, ACK, ESP_INFO [, DIFFIE_HELLMAN]
skipping to change at page 10, line 39 skipping to change at page 13, line 5
UPDATE: ACK UPDATE: ACK
-----------------------------------------------------> ----------------------------------------------------->
The host willing to update the ESP SA creates and sends an UPDATE The host willing to update the ESP SA creates and sends an UPDATE
message. The message contains the ESP_INFO parameter containing the message. The message contains the ESP_INFO parameter containing the
old SPI value that was used, the new SPI value to be used, and the old SPI value that was used, the new SPI value to be used, and the
index value for the keying material, giving the point from where the index value for the keying material, giving the point from where the
next keys will be drawn. If new keying material must be generated, next keys will be drawn. If new keying material must be generated,
the UPDATE message will also contain the DIFFIE_HELLMAN parameter the UPDATE message will also contain the DIFFIE_HELLMAN parameter
defined in [RFC5201]. defined in [I-D.ietf-hip-rfc5201-bis].
The host receiving the UPDATE message requesting update of an The host receiving the UPDATE message requesting update of an
existing ESP SA MUST reply with an UPDATE message. In the reply existing ESP SA MUST reply with an UPDATE message. In the reply
message, the host sends the ESP_INFO parameter containing the message, the host sends the ESP_INFO parameter containing the
corresponding values: old SPI, new SPI, and the keying material corresponding values: old SPI, new SPI, and the keying material
index. If the incoming UPDATE contained a DIFFIE_HELLMAN parameter, index. If the incoming UPDATE contained a DIFFIE_HELLMAN parameter,
the reply packet MUST also contain a DIFFIE_HELLMAN parameter. the reply packet MUST also contain a DIFFIE_HELLMAN parameter.
5. Parameter and Packet Formats 5. Parameter and Packet Formats
In this section, new and modified HIP parameters are presented, as In this section, new and modified HIP parameters are presented, as
well as modified HIP packets. well as modified HIP packets.
5.1. New Parameters 5.1. New Parameters
Two new HIP parameters are defined for setting up ESP transport Two new HIP parameters are defined for setting up ESP transport
format associations in HIP communication and for rekeying existing format associations in HIP communication and for rekeying existing
ones. Also, the NOTIFY parameter, described in [RFC5201], has two ones. Also, the NOTIFICATION parameter, described in
new error parameters. [I-D.ietf-hip-rfc5201-bis], has two new error parameters.
Parameter Type Length Data Parameter Type Length Data
ESP_INFO 65 12 Remote's old SPI, ESP_INFO 65 12 Remote's old SPI,
new SPI, and other info new SPI, and other info
ESP_TRANSFORM 4095 variable ESP Encryption and ESP_TRANSFORM 4095 variable ESP Encryption and
Authentication Transform(s) Authentication Transform(s)
5.1.1. ESP_INFO 5.1.1. ESP_INFO
During the establishment and update of an ESP SA, the SPI value of During the establishment and update of an ESP SA, the SPI value of
both hosts must be transmitted between the hosts. During the both hosts must be transmitted between the hosts. In addition, hosts
establishment and update of an ESP SA, the SPI value of both hosts need the index value to the KEYMAT when they are drawing keys from
must be transmitted between the hosts. In addition, hosts need the the generated keying material. The ESP_INFO parameter is used to
index value to the KEYMAT when they are drawing keys from the
generated keying material. The ESP_INFO parameter is used to
transmit the SPI values and the KEYMAT index information between the transmit the SPI values and the KEYMAT index information between the
hosts. hosts.
During the initial ESP SA setup, the hosts send the SPI value that During the initial ESP SA setup, the hosts send the SPI value that
they want the peer to use when sending ESP data to them. The value they want the peer to use when sending ESP data to them. The value
is set in the NEW SPI field of the ESP_INFO parameter. In the is set in the NEW SPI field of the ESP_INFO parameter. In the
initial setup, an old value for the SPI does not exist, thus the OLD initial setup, an old value for the SPI does not exist, thus the OLD
SPI value field is set to zero. The OLD SPI field value may also be SPI value field is set to zero. The OLD SPI field value may also be
zero when additional SAs are set up between HIP hosts, e.g., in case zero when additional SAs are set up between HIP hosts, e.g., in case
of multihomed HIP hosts [RFC5206]. However, such use is beyond the of multihomed HIP hosts [RFC5206]. However, such use is beyond the
scope of this specification. scope of this specification.
RFC 4301 [RFC4301] describes how to establish multiple SAs to
properly support QoS. If different classes of traffic (distinguished
by Differentiated Services Code Point (DSCP) bits [RFC3474],
[RFC3260]) are sent on the same SA, and if the receiver is employing
the optional anti-replay feature available in ESP, this could result
in inappropriate discarding of lower priority packets due to the
windowing mechanism used by this feature. Therefore, a sender SHOULD
put traffic of different classes but with the same selector values on
different SAs to support Quality of Service (QoS) appropriately. To
permit this, the implementation MUST permit establishment and
maintenance of multiple SAs between a given sender and receiver with
the same selectors. Distribution of traffic among these parallel SAs
to support QoS is locally determined by the sender and is not
negotiated by HIP. The receiver MUST process the packets from the
different SAs without prejudice. It is possible that the DSCP value
changes en route, but this should not cause problems with respect to
IPsec processing since the value is not employed for SA selection and
MUST NOT be checked as part of SA/packet validation.
The KEYMAT index value points to the place in the KEYMAT from where The KEYMAT index value points to the place in the KEYMAT from where
the keying material for the ESP SAs is drawn. The KEYMAT index value the keying material for the ESP SAs is drawn. The KEYMAT index value
is zero only when the ESP_INFO is sent during a rekeying process and is zero only when the ESP_INFO is sent during a rekeying process and
new keying material is generated. new keying material is generated.
During the life of an SA established by HIP, one of the hosts may During the life of an SA established by HIP, one of the hosts may
need to reset the Sequence Number to one and rekey. The reason for need to reset the Sequence Number to one and rekey. The reason for
rekeying might be an approaching sequence number wrap in ESP, or a 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 local policy on use of a key. Rekeying ends the current SAs and
starts new ones on both peers. starts new ones on both peers.
During the rekeying process, the ESP_INFO parameter is used to During the rekeying process, the ESP_INFO parameter is used to
transmit the changed SPI values and the keying material index. transmit the changed SPI values and the keying material index.
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 | KEYMAT Index | | Reserved | KEYMAT Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OLD SPI | | OLD SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NEW SPI | | NEW SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 65
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 and the ESP_INFO is sent in an
UPDATE packet, the field MUST be zero. If the
ESP_INFO is included in base exchange messages, the
KEYMAT Index must have the index value of the point
from where the ESP SA keys are drawn. 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 packet MUST contain
a new Diffie-Hellman key.
OLD SPI old SPI for data sent to address(es) associated
with this SA. If this is an initial SA setup, the
OLD SPI value is zero.
NEW SPI new SPI for data sent to address(es) associated Type 65
with this SA. 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 and the ESP_INFO is sent in an
UPDATE packet, the field MUST be zero. If the
ESP_INFO is included in base exchange messages, the
KEYMAT Index must have the index value of the point
from where the ESP SA keys are drawn. 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 packet MUST contain
a new Diffie-Hellman key.
OLD SPI old SPI for data sent to address(es) associated
with this SA. If this is an initial SA setup, the
OLD SPI value is zero.
NEW SPI new SPI for data sent to address(es) associated
with this SA.
5.1.2. ESP_TRANSFORM 5.1.2. ESP_TRANSFORM
The ESP_TRANSFORM parameter is used during ESP SA establishment. The The ESP_TRANSFORM parameter is used during ESP SA establishment. The
first party sends a selection of transform families in the first party sends a selection of transform families in the
ESP_TRANSFORM parameter, and the peer must select one of the proposed ESP_TRANSFORM parameter, and the peer must select one of the proposed
values and include it in the response ESP_TRANSFORM parameter. values and include it in the response ESP_TRANSFORM parameter.
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
skipping to change at page 13, line 33 skipping to change at page 15, line 30
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Suite ID #n | Padding | | Suite ID #n | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type 4095 Type 4095
Length length in octets, excluding Type, Length, and Length length in octets, excluding Type, Length, and
padding padding
Reserved zero when sent, ignored when received Reserved zero when sent, ignored when received
Suite ID defines the ESP Suite to be used Suite ID defines the ESP Suite to be used
The following Suite IDs are defined in RFC 5201 [RFC5201]: The following Suite IDs can be used:
Suite ID Value Suite ID Value
RESERVED 0 RESERVED 0
AES-CBC with HMAC-SHA1 1 AES-128-CBC with HMAC-SHA1 1 [RFC3602], [RFC2404]
3DES-CBC with HMAC-SHA1 2 DEPRECATED 2
3DES-CBC with HMAC-MD5 3 DEPRECATED 3
BLOWFISH-CBC with HMAC-SHA1 4 DEPRECATED 4
NULL with HMAC-SHA1 5 DEPRECATED 5
NULL with HMAC-MD5 6 DEPRECATED 6
NULL-ENCRYPT with HMAC-SHA-256 7 [RFC2410], [RFC4868]
AES-128-CBC with HMAC-SHA-256 8 [RFC3602], [RFC4868]
AES-256-CBC with HMAC-SHA-256 9 [RFC3602], [RFC4868]
AES-CCM-8 10 [RFC4309]
AES-CCM-16 11 [RFC4309]
AES-GCM with a 8 octet ICV 12 [RFC4106]
AES-GCM with a 16 octet ICV 13 [RFC4106]
AES-CMAC-96 14 [RFC4493], [RFC4494]
AES-GMAC 15 [RFC4543]
The sender of an ESP transform parameter MUST make sure that there The sender of an ESP transform parameter MUST make sure that there
are no more than six (6) Suite IDs in one ESP transform parameter. are no more than six (6) Suite IDs in one ESP transform parameter.
Conversely, a recipient MUST be prepared to handle received transport
Conversely, a recipient MUST be prepared to handle received transform
parameters that contain more than six Suite IDs. The limited number parameters that contain more than six Suite IDs. The limited number
of Suite IDs sets the maximum size of the ESP_TRANSFORM parameter. of Suite IDs sets the maximum size of the ESP_TRANSFORM parameter.
As the default configuration, the ESP_TRANSFORM parameter MUST As the default configuration, the ESP_TRANSFORM parameter MUST
contain at least one of the mandatory Suite IDs. There MAY be a contain at least one of the mandatory Suite IDs. There MAY be a
configuration option that allows the administrator to override this configuration option that allows the administrator to override this
default. default.
Mandatory implementations: AES-CBC with HMAC-SHA1 and NULL with HMAC- Mandatory implementations: AES-128-CBC with HMAC-SHA-256 and NULL
SHA1. with HMAC-SHA-256.
Under some conditions, it is possible to use Traffic Flow Under some conditions, it is possible to use Traffic Flow
Confidentiality (TFC) [RFC4303] with ESP in BEET mode. However, the Confidentiality (TFC) [RFC4303] with ESP in BEET mode. However, the
definition of such operation is future work and must be done in a definition of such operation is future work and must be done in a
separate specification. separate specification.
5.1.3. NOTIFY Parameter 5.1.3. NOTIFICATION Parameter
The HIP base specification defines a set of NOTIFY error types. The The HIP base specification defines a set of NOTIFICATION error types.
following error types are required for describing errors in ESP The following error types are required for describing errors in ESP
Transform crypto suites during negotiation. Transform crypto suites during negotiation.
NOTIFY PARAMETER - ERROR TYPES Value NOTIFICATION PARAMETER - ERROR TYPES Value
------------------------------ ----- ------------------------------------ -----
NO_ESP_PROPOSAL_CHOSEN 18 NO_ESP_PROPOSAL_CHOSEN 18
None of the proposed ESP Transform crypto suites was None of the proposed ESP Transform crypto suites was
acceptable. acceptable.
INVALID_ESP_TRANSFORM_CHOSEN 19 INVALID_ESP_TRANSFORM_CHOSEN 19
The ESP Transform crypto suite does not correspond to The ESP Transform crypto suite does not correspond to
one offered by the Responder. one offered by the Responder.
skipping to change at page 14, line 46 skipping to change at page 16, line 51
The ESP Security Association is set up during the base exchange. The The ESP Security Association is set up during the base exchange. The
following subsections define the ESP SA setup procedure using both following subsections define the ESP SA setup procedure using both
base exchange messages (R1, I2, R2) and UPDATE messages. base exchange messages (R1, I2, R2) and UPDATE messages.
5.2.1. Setup During Base Exchange 5.2.1. Setup During Base Exchange
5.2.1.1. Modifications in R1 5.2.1.1. Modifications in R1
The ESP_TRANSFORM contains the ESP modes supported by the sender, in The ESP_TRANSFORM contains the ESP modes supported by the sender, in
the order of preference. All implementations MUST support AES-CBC the order of preference. All implementations MUST support AES-128-
[RFC3602] with HMAC-SHA-1-96 [RFC2404]. CBC [RFC3602] with HMAC-SHA-256 [RFC4868].
The following figure shows the resulting R1 packet layout. The following figure shows the resulting R1 packet layout.
The HIP parameters for the R1 packet: The HIP parameters for the R1 packet:
IP ( HIP ( [ R1_COUNTER, ] IP ( HIP ( [ R1_COUNTER, ]
PUZZLE, PUZZLE,
DIFFIE_HELLMAN, DIFFIE_HELLMAN,
HIP_TRANSFORM, HIP_CIPHER,
ESP_TRANSFORM, ESP_TRANSFORM,
HOST_ID, HOST_ID,
[ ECHO_REQUEST, ] [ ECHO_REQUEST, ]
HIP_SIGNATURE_2 ) HIP_SIGNATURE_2 )
[, ECHO_REQUEST ]) [, ECHO_REQUEST ])
5.2.1.2. Modifications in I2 5.2.1.2. Modifications in I2
The ESP_INFO contains the sender's SPI for this association as well The ESP_INFO contains the sender's SPI for this association as well
as the KEYMAT index from where the ESP SA keys will be drawn. The as the KEYMAT index from where the ESP SA keys will be drawn. The
old SPI value is set to zero. old SPI value is set to zero.
The ESP_TRANSFORM contains the ESP mode selected by the sender of R1. The ESP_TRANSFORM contains the ESP mode selected by the sender of R1.
All implementations MUST support AES-CBC [RFC3602] with HMAC-SHA-1-96 All implementations MUST support AES-128-CBC [RFC3602] with HMAC-SHA-
[RFC2404]. 256 [RFC4868].
The following figure shows the resulting I2 packet layout. The following figure shows the resulting I2 packet layout.
The HIP parameters for the I2 packet: The HIP parameters for the I2 packet:
IP ( HIP ( ESP_INFO, IP ( HIP ( ESP_INFO,
[R1_COUNTER,] [R1_COUNTER,]
SOLUTION, SOLUTION,
DIFFIE_HELLMAN, DIFFIE_HELLMAN,
HIP_TRANSFORM, HIP_CIPHER,
ESP_TRANSFORM, ESP_TRANSFORM,
ENCRYPTED { HOST_ID }, ENCRYPTED { HOST_ID },
[ ECHO_RESPONSE ,] [ ECHO_RESPONSE ,]
HMAC, HMAC,
HIP_SIGNATURE HIP_SIGNATURE
[, ECHO_RESPONSE] ) ) [, ECHO_RESPONSE] ) )
5.2.1.3. Modifications in R2 5.2.1.3. Modifications in R2
The R2 contains an ESP_INFO parameter, which has the SPI value of the The R2 contains an ESP_INFO parameter, which has the SPI value of the
skipping to change at page 17, line 43 skipping to change at page 19, line 40
IP ( HIP ( ESP_INFO, IP ( HIP ( ESP_INFO,
SEQ, SEQ,
ACK, ACK,
[ DIFFIE_HELLMAN, ] [ DIFFIE_HELLMAN, ]
HMAC, HMAC,
HIP_SIGNATURE ) ) HIP_SIGNATURE ) )
5.4. ICMP Messages 5.4. ICMP Messages
ICMP message handling is mainly described in the HIP base ICMP message handling is mainly described in the HIP base
specification [RFC5201]. In this section, we describe the actions specification [I-D.ietf-hip-rfc5201-bis]. In this section, we
related to ESP security associations. describe the actions related to ESP security associations.
5.4.1. Unknown SPI 5.4.1. Unknown SPI
If a HIP implementation receives an ESP packet that has an If a HIP implementation receives an ESP packet that has an
unrecognized SPI number, it MAY respond (subject to rate limiting the unrecognized SPI number, it MAY respond (subject to rate limiting the
responses) with an ICMP packet with type "Parameter Problem", with responses) with an ICMP packet with type "Parameter Problem", with
the pointer pointing to the beginning of SPI field in the ESP header. the pointer pointing to the beginning of SPI field in the ESP header.
6. Packet Processing 6. Packet Processing
Packet processing is mainly defined in the HIP base specification Packet processing is mainly defined in the HIP base specification
[RFC5201]. This section describes the changes and new requirements [I-D.ietf-hip-rfc5201-bis]. This section describes the changes and
for packet handling when the ESP transport format is used. Note that new requirements for packet handling when the ESP transport format is
all HIP packets (currently protocol 253) MUST bypass ESP processing. used. Note that all HIP packets (currently protocol 139) MUST bypass
ESP processing.
6.1. Processing Outgoing Application Data 6.1. Processing Outgoing Application Data
Outgoing application data handling is specified in the HIP base Outgoing application data handling is specified in the HIP base
specification [RFC5201]. When the ESP transport format is used, and specification [I-D.ietf-hip-rfc5201-bis]. When the ESP transport
there is an active HIP session for the given < source, destination > format is used, and there is an active HIP session for the given <
HIT pair, the outgoing datagram is protected using the ESP security source, destination > HIT pair, the outgoing datagram is protected
association. In a typical implementation, this will result in a using the ESP security association. The following additional steps
BEET-mode ESP packet being sent. BEET-mode [ESP-BEET] was introduced define the conceptual processing rules for outgoing ESP protected
above in Section 3.2. The following additional steps define the datagrams.
conceptual processing rules for outgoing ESP protected datagrams.
1. Detect the proper ESP SA using the HITs in the packet header or 1. Detect the proper ESP SA using the HITs in the packet header or
other information associated with the packet other information associated with the packet
2. Process the packet normally, as if the SA was a transport mode 2. Process the packet normally, as if the SA was a transport mode
SA. SA.
3. Ensure that the outgoing ESP protected packet has proper IP 3. Ensure that the outgoing ESP protected packet has proper IP
header format depending on the used IP address family, and proper header format depending on the used IP address family, and proper
IP addresses in its IP header, e.g., by replacing HITs left by IP addresses in its IP header, e.g., by replacing HITs left by
skipping to change at page 19, line 33 skipping to change at page 21, line 33
datagram to the right upper layer socket is performed as usual, datagram to the right upper layer socket is performed as usual,
except that the HITs are used in place of IP addresses during the except that the HITs are used in place of IP addresses during the
demultiplexing. demultiplexing.
6.3. HMAC and SIGNATURE Calculation and Verification 6.3. HMAC and SIGNATURE Calculation and Verification
The new HIP parameters described in this document, ESP_INFO and The new HIP parameters described in this document, ESP_INFO and
ESP_TRANSFORM, must be protected using HMAC and signature ESP_TRANSFORM, must be protected using HMAC and signature
calculations. In a typical implementation, they are included in R1, calculations. In a typical implementation, they are included in R1,
I2, R2, and UPDATE packet HMAC and SIGNATURE calculations as I2, R2, and UPDATE packet HMAC and SIGNATURE calculations as
described in [RFC5201]. described in [I-D.ietf-hip-rfc5201-bis].
6.4. Processing Incoming ESP SA Initialization (R1) 6.4. Processing Incoming ESP SA Initialization (R1)
The ESP SA setup is initialized in the R1 message. The receiving The ESP SA setup is initialized in the R1 message. The receiving
host (Initiator) selects one of the ESP transforms from the presented host (Initiator) selects one of the ESP transforms from the presented
values. If no suitable value is found, the negotiation is values. If no suitable value is found, the negotiation is
terminated. The selected values are subsequently used when terminated. The selected values are subsequently used when
generating and using encryption keys, and when sending the reply generating and using encryption keys, and when sending the reply
packet. If the proposed alternatives are not acceptable to the packet. If the proposed alternatives are not acceptable to the
system, it may abandon the ESP SA establishment negotiation, or it system, it may abandon the ESP SA establishment negotiation, or it
skipping to change at page 20, line 10 skipping to change at page 22, line 10
the system prepares and creates an incoming ESP security association. the system prepares and creates an incoming ESP security association.
It may also prepare a security association for outgoing traffic, but It may also prepare a security association for outgoing traffic, but
since it does not have the correct SPI value yet, it cannot activate since it does not have the correct SPI value yet, it cannot activate
it. it.
6.5. Processing Incoming Initialization Reply (I2) 6.5. Processing Incoming Initialization Reply (I2)
The following steps are required to process the incoming ESP SA The following steps are required to process the incoming ESP SA
initialization replies in I2. The steps below assume that the I2 has initialization replies in I2. The steps below assume that the I2 has
been accepted for processing (e.g., has not been dropped due to HIT been accepted for processing (e.g., has not been dropped due to HIT
comparisons as described in [RFC5201]). comparisons as described in [I-D.ietf-hip-rfc5201-bis]).
o The ESP_TRANSFORM parameter is verified and it MUST contain a o The ESP_TRANSFORM parameter is verified and it MUST contain a
single value in the parameter, and it MUST match one of the values single value in the parameter, and it MUST match one of the values
offered in the initialization packet. offered in the initialization packet.
o The ESP_INFO NEW SPI field is parsed to obtain the SPI that will o The ESP_INFO NEW SPI field is parsed to obtain the SPI that will
be used for the Security Association outbound from the Responder be used for the Security Association outbound from the Responder
and inbound to the Initiator. For this initial ESP SA and inbound to the Initiator. For this initial ESP SA
establishment, the old SPI value MUST be zero. The KEYMAT Index establishment, the old SPI value MUST be zero. The KEYMAT Index
field MUST contain the index value to the KEYMAT from where the field MUST contain the index value to the KEYMAT from where the
skipping to change at page 21, line 12 skipping to change at page 23, line 12
A system may initiate the SA rekeying procedure at any time. It MUST A system may initiate the SA rekeying procedure at any time. It MUST
initiate a rekey if its incoming ESP sequence counter is about to initiate a rekey if its incoming ESP sequence counter is about to
overflow. The system MUST NOT replace its keying material until the overflow. The system MUST NOT replace its keying material until the
rekeying packet exchange successfully completes. rekeying packet exchange successfully completes.
Optionally, a system may include a new Diffie-Hellman key for use in Optionally, a system may include a new Diffie-Hellman key for use in
new KEYMAT generation. New KEYMAT generation occurs prior to drawing new KEYMAT generation. New KEYMAT generation occurs prior to drawing
the new keys. the new keys.
The rekeying procedure uses the UPDATE mechanism defined in The rekeying procedure uses the UPDATE mechanism defined in
[RFC5201]. Because each peer must update its half of the security [I-D.ietf-hip-rfc5201-bis]. Because each peer must update its half
association pair (including new SPI creation), the rekeying process of the security association pair (including new SPI creation), the
requires that each side both send and receive an UPDATE. A system rekeying process requires that each side both send and receive an
will then rekey the ESP SA when it has sent parameters to the peer UPDATE. A system will then rekey the ESP SA when it has sent
and has received both an ACK of the relevant UPDATE message and parameters to the peer and has received both an ACK of the relevant
corresponding peer's parameters. It may be that the ACK and the UPDATE message and corresponding peer's parameters. It may be that
required HIP parameters arrive in different UPDATE messages. This is the ACK and the required HIP parameters arrive in different UPDATE
always true if a system does not initiate ESP SA update but responds messages. This is always true if a system does not initiate ESP SA
to an update request from the peer, and may also occur if two systems update but responds to an update request from the peer, and may also
initiate update nearly simultaneously. In such a case, if the system occur if two systems initiate update nearly simultaneously. In such
has an outstanding update request, it saves the one parameter and a case, if the system has an outstanding update request, it saves the
waits for the other before completing rekeying. one parameter and waits for the other before completing rekeying.
The following steps define the processing rules for initiating an ESP The following steps define the processing rules for initiating an ESP
SA update: SA update:
1. The system decides whether to continue to use the existing KEYMAT 1. The system decides whether to continue to use the existing KEYMAT
or to generate a new KEYMAT. In the latter case, the system MUST or to generate a new KEYMAT. In the latter case, the system MUST
generate a new Diffie-Hellman public key. generate a new Diffie-Hellman public key.
2. The system creates an UPDATE packet, which contains the ESP_INFO 2. The system creates an UPDATE packet, which contains the ESP_INFO
parameter. In addition, the host may include the optional parameter. In addition, the host may include the optional
skipping to change at page 22, line 19 skipping to change at page 24, line 19
outstanding ESP SA update request for an indefinite time. outstanding ESP SA update request for an indefinite time.
To simplify the state machine, a host MUST NOT generate new UPDATEs To simplify the state machine, a host MUST NOT generate new UPDATEs
while it has an outstanding ESP SA update request, unless it is while it has an outstanding ESP SA update request, unless it is
restarting the update process. restarting the update process.
6.9. Processing Incoming UPDATE Packets 6.9. Processing Incoming UPDATE Packets
When a system receives an UPDATE packet, it must be processed if the When a system receives an UPDATE packet, it must be processed if the
following conditions hold (in addition to the generic conditions following conditions hold (in addition to the generic conditions
specified for UPDATE processing in Section 6.12 of [RFC5201]): specified for UPDATE processing in Section 6.12 of
[I-D.ietf-hip-rfc5201-bis]):
1. A corresponding HIP association must exist. This is usually 1. A corresponding HIP association must exist. This is usually
ensured by the underlying UPDATE mechanism. ensured by the underlying UPDATE mechanism.
2. The state of the HIP association is ESTABLISHED or R2-SENT. 2. The state of the HIP association is ESTABLISHED or R2-SENT.
If the above conditions hold, the following steps define the If the above conditions hold, the following steps define the
conceptual processing rules for handling the received UPDATE packet: conceptual processing rules for handling the received UPDATE packet:
1. If the received UPDATE contains a DIFFIE_HELLMAN parameter, the 1. If the received UPDATE contains a DIFFIE_HELLMAN parameter, the
skipping to change at page 24, line 44 skipping to change at page 26, line 44
denotes the host with the lower HIT value. When HIT values are denotes the host with the lower HIT value. When HIT values are
compared, they are interpreted as positive (unsigned) 128-bit compared, they are interpreted as positive (unsigned) 128-bit
integers in network byte order. integers in network byte order.
The four HIP keys are only drawn from KEYMAT during a HIP I1->R2 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 exchange. Subsequent rekeys using UPDATE will only draw the four ESP
keys from KEYMAT. Section 6.9 describes the rules for reusing or keys from KEYMAT. Section 6.9 describes the rules for reusing or
regenerating KEYMAT based on the rekeying. regenerating KEYMAT based on the rekeying.
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, as specified in Section 6.5 of
apply: [I-D.ietf-hip-rfc5201-bis].
AES 128 bits
SHA-1 160 bits
NULL 0 bits
8. Security Considerations 8. Security Considerations
In this document, the usage of ESP [RFC4303] between HIP hosts to In this document, the usage of ESP [RFC4303] between HIP hosts to
protect data traffic is introduced. The Security Considerations for protect data traffic is introduced. The Security Considerations for
ESP are discussed in the ESP specification. ESP are discussed in the ESP specification.
There are different ways to establish an ESP Security Association There are different ways to establish an ESP Security Association
between two nodes. This can be done, e.g., using IKE [RFC4306]. between two nodes. This can be done, e.g., using IKE [RFC5996].
This document specifies how the Host Identity Protocol is used to This document specifies how the Host Identity Protocol is used to
establish ESP Security Associations. establish ESP Security Associations.
The following issues are new or have changed from the standard ESP The following issues are new or have changed from the standard ESP
usage: usage:
o Initial keying material generation o Initial keying material generation
o Updating the keying material o Updating the keying material
The initial keying material is generated using the Host Identity The initial keying material is generated using the Host Identity
Protocol [RFC5201] using the Diffie-Hellman procedure. This document Protocol [I-D.ietf-hip-rfc5201-bis] using the Diffie-Hellman
extends the usage of the UPDATE packet, defined in the base procedure. This document extends the usage of the UPDATE packet,
specification, to modify existing ESP SAs. The hosts may rekey, defined in the base specification, to modify existing ESP SAs. The
i.e., force the generation of new keying material using the Diffie- hosts may rekey, i.e., force the generation of new keying material
Hellman procedure. The initial setup of ESP SA between the hosts is using the Diffie-Hellman procedure. The initial setup of ESP SA
done during the base exchange, and the message exchange is protected between the hosts is done during the base exchange, and the message
using methods provided by base exchange. Changes in connection exchange is protected using methods provided by base exchange.
parameters means basically that the old ESP SA is removed and a new Changes in connection parameters means basically that the old ESP SA
one is generated once the UPDATE message exchange has been completed. is removed and a new one is generated once the UPDATE message
The message exchange is protected using the HIP association keys. exchange has been completed. The message exchange is protected using
Both HMAC and signing of packets is used. the HIP association keys. Both HMAC and signing of packets is used.
9. IANA Considerations 9. IANA Considerations
This document defines additional parameters and NOTIFY error types This document defines additional parameters and NOTIFY error types
for the Host Identity Protocol [RFC5201]. for the Host Identity Protocol [I-D.ietf-hip-rfc5201-bis].
The new parameters and their type numbers are defined in The new parameters and their type numbers are defined in
Section 5.1.1 and Section 5.1.2, and they have been added to the Section 5.1.1 and Section 5.1.2, and they have been added to the
Parameter Type namespace specified in [RFC5201]. Parameter Type namespace specified in [I-D.ietf-hip-rfc5201-bis].
The new NOTIFY error types and their values are defined in The new NOTIFY error types and their values are defined in
Section 5.1.3, and they have been added to the Notify Message Type Section 5.1.3, and they have been added to the Notify Message Type
namespace specified in [RFC5201]. namespace specified in [I-D.ietf-hip-rfc5201-bis].
10. Acknowledgments 10. Acknowledgments
This document was separated from the base "Host Identity Protocol" This document was separated from the base "Host Identity Protocol"
specification in the beginning of 2005. Since then, a number of specification in the beginning of 2005. Since then, a number of
people have contributed to the text by providing comments and people have contributed to the text by providing comments and
modification proposals. The list of people include Tom Henderson, modification proposals. The list of people include Tom Henderson,
Jeff Ahrenholz, Jan Melen, Jukka Ylitalo, and Miika Komu. The Jeff Ahrenholz, Jan Melen, Jukka Ylitalo, and Miika Komu.
authors also want to thank Charlie Kaufman for reviewing the document Especially, the authors want to thank Pekka Nikander for his
with his eye on the usage of crypto algorithms. invaluable contributions to the document since the first draft
version. The authors want to thank also Charlie Kaufman for
reviewing the document with his eye on the usage of crypto
algorithms.
Due to the history of this document, most of the ideas are inherited Due to the history of this document, most of the ideas are inherited
from the base "Host Identity Protocol" specification. Thus, the list from the base "Host Identity Protocol" specification. Thus, the list
of people in the Acknowledgments section of that specification is of people in the Acknowledgments section of that specification is
also valid for this document. Many people have given valuable also valid for this document. Many people have given valuable
feedback, and our apologies to anyone whose name is missing. feedback, and our apologies to anyone whose name is missing.
11. References 11. References
11.1. Normative references 11.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [I-D.ietf-hip-rfc5201-bis] Moskowitz, R., Heer, T., Jokela, P., and
Requirement Levels", BCP 14, RFC 2119, March 1997. T. Henderson, "Host Identity Protocol
Version 2 (HIPv2)",
draft-ietf-hip-rfc5201-bis-14 (work in
progress), October 2013.
[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within [RFC2119] Bradner, S., "Key words for use in RFCs
ESP and AH", RFC 2404, November 1998. to Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997.
[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher [RFC2404] Madson, C. and R. Glenn, "The Use of
Algorithm and Its Use with IPsec", RFC 3602, HMAC-SHA-1-96 within ESP and AH",
September 2003. RFC 2404, November 1998.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", [RFC2410] Glenn, R. and S. Kent, "The NULL
RFC 4303, December 2005. Encryption Algorithm and Its Use With
IPsec", RFC 2410, November 1998.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., Ed., and T. [RFC3602] Frankel, S., Glenn, R., and S. Kelly,
Henderson, "Host Identity Protocol", RFC 5201, "The AES-CBC Cipher Algorithm and Its Use
April 2008. with IPsec", RFC 3602, September 2003.
[RFC4106] Viega, J. and D. McGrew, "The Use of
Galois/Counter Mode (GCM) in IPsec
Encapsulating Security Payload (ESP)",
RFC 4106, June 2005.
[RFC4303] Kent, S., "IP Encapsulating Security
Payload (ESP)", RFC 4303, December 2005.
[RFC4309] Housley, R., "Using Advanced Encryption
Standard (AES) CCM Mode with IPsec
Encapsulating Security Payload (ESP)",
RFC 4309, December 2005.
[RFC4493] Song, JH., Poovendran, R., Lee, J., and
T. Iwata, "The AES-CMAC Algorithm",
RFC 4493, June 2006.
[RFC4494] Song, JH., Poovendran, R., and J. Lee,
"The AES-CMAC-96 Algorithm and Its Use
with IPsec", RFC 4494, June 2006.
[RFC4543] McGrew, D. and J. Viega, "The Use of
Galois Message Authentication Code (GMAC)
in IPsec ESP and AH", RFC 4543, May 2006.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-
SHA-256, HMAC-SHA-384, and HMAC-SHA-512
with IPsec", RFC 4868, May 2007.
11.2. Informative references 11.2. Informative references
[ESP-BEET] Nikander, P. and J. Melen, "A Bound End-to-End Tunnel [I-D.ietf-hip-rfc4423-bis] Moskowitz, R. and M. Komu, "Host Identity
(BEET) mode for ESP", Work in Progress, November 2007. Protocol Architecture",
draft-ietf-hip-rfc4423-bis-06 (work in
progress), November 2013.
[RFC3260] Grossman, D., "New Terminology and Clarifications for [RFC0791] Postel, J., "Internet Protocol", STD 5,
Diffserv", RFC 3260, April 2002. RFC 791, September 1981.
[RFC3474] Lin, Z. and D. Pendarakis, "Documentation of IANA [RFC4301] Kent, S. and K. Seo, "Security
assignments for Generalized MultiProtocol Label Switching Architecture for the Internet Protocol",
(GMPLS) Resource Reservation Protocol - Traffic RFC 4301, December 2005.
Engineering (RSVP-TE) Usage and Extensions for
Automatically Switched Optical Network (ASON)", RFC 3474,
March 2003.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the [RFC5206] Henderson, T., Ed., "End-Host Mobility
Internet Protocol", RFC 4301, December 2005. and Multihoming with the Host Identity
Protocol", RFC 5206, April 2008.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", [RFC5207] Stiemerling, M., Quittek, J., and L.
RFC 4306, December 2005. Eggert, "NAT and Firewall Traversal
Issues of Host Identity Protocol (HIP)
Communication", RFC 5207, April 2008.
[RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol [RFC5770] Komu, M., Henderson, T., Tschofenig, H.,
(HIP) Architecture", RFC 4423, May 2006. Melen, J., and A. Keranen, "Basic Host
Identity Protocol (HIP) Extensions for
Traversal of Network Address
Translators", RFC 5770, April 2010.
[RFC5206] Henderson, T., Ed., "End-Host Mobility and Multihoming [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P.
with the Host Identity Protocol", RFC 5206, April 2008. Eronen, "Internet Key Exchange Protocol
Version 2 (IKEv2)", RFC 5996,
September 2010.
Appendix A. A Note on Implementation Options Appendix A. A Note on Implementation Options
It is possible to implement this specification in multiple different It is possible to implement this specification in multiple different
ways. As noted above, one possible way of implementing this is to ways. As noted above, one possible way of implementing this is to
rewrite IP headers below IPsec. In such an implementation, IPsec is rewrite IP headers below IPsec. In such an implementation, IPsec is
used as if it was processing IPv6 transport mode packets, with the used as if it was processing IPv6 transport mode packets, with the
IPv6 header containing HITs instead of IP addresses in the source and IPv6 header containing HITs instead of IP addresses in the source and
destination address fields. In outgoing packets, after IPsec destination address fields. In outgoing packets, after IPsec
processing, the HITs are replaced with actual IP addresses, based on processing, the HITs are replaced with actual IP addresses, based on
the HITs and the SPI. In incoming packets, before IPsec processing, the HITs and the SPI. In incoming packets, before IPsec processing,
the IP addresses are replaced with HITs, based on the SPI in the the IP addresses are replaced with HITs, based on the SPI in the
incoming packet. In such an implementation, all IPsec policies are incoming packet. In such an implementation, all IPsec policies are
based on HITs and the upper layers only see packets with HITs in the based on HITs and the upper layers only see packets with HITs in the
place of IP addresses. Consequently, support of HIP does not place of IP addresses. Consequently, support of HIP does not
conflict with other uses of IPsec as long as the SPI spaces are kept conflict with other uses of IPsec as long as the SPI spaces are kept
separate. separate. Appendix B describes another way to implement this
specification.
Another way to implement this specification is to use the proposed Appendix B. Bound End-to-End Tunnel mode for ESP
BEET mode (A Bound End-to-End mode for ESP, [ESP-BEET]). The BEET
mode provides some features from both IPsec tunnel and transport
modes. The HIP uses HITs 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 on 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).
Compared to the option of implementing the required address rewrites This section introduces an alternative way of implementing the
outside of IPsec, BEET has one implementation level benefit. The necessary functions for HIP ESP transport. Compared to the option of
BEET-way of implementing the address rewriting keeps all the implementing the required address rewrites outside of IPsec, BEET has
configuration information in one place, at the SAD. On the other one implementation level benefit. In BEET-way of implementing, the
hand, when address rewriting is implemented separately, the address rewriting information is kept in one place, at the SAD. On
implementation must make sure that the information in the SAD and the the other hand, when address rewriting is implemented separately, the
implementation MUST make sure that the information in the SAD and the
separate address rewriting DB are kept in synchrony. As a result, separate address rewriting DB are kept in synchrony. As a result,
the BEET-mode-based way of implementing this specification is the BEET-mode-based way of implementing this specification is
RECOMMENDED over the separate implementation. RECOMMENDED over the separate implementation as it keeps the binds
the identities, encryption and locators tightly together. It should
be noted that implementing BEET mode doesn't require that
corresponding hosts implement it as the behavior is only visible
internally in a host.
The BEET mode is a combination of IPsec tunnel and transport modes
and provides some of the features from both. The HIP uses HITs 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 on 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).
B.1. Protocol definition
In this section we define the exact protocol formats and operations.
B.1.1. Changes to Security Association data structures
A BEET mode Security Association contains the same data as a regular
tunnel mode Security Association, with the exception that the inner
selectors must be single addresses and cannot be subnets. The data
includes the following:
A pair of inner IP addresses.
A pair of outer IP addresses.
Cryptographic keys and other data as defined in RFC4301 [RFC4301]
Section 4.4.2.
A conforming implementation MAY store the data in a way similar to a
regular tunnel mode Security Association.
Note that in a conforming implementation the inner and outer
addresses MAY belong to different address families. All
implementations that support both IPv4 and IPv6 SHOULD support both
IPv4-over-IPv6 and IPv6-over-IPv4 tunneling.
B.1.2. Packet format
The wire packet format is identical to the ESP transport mode wire
format as defined in [RFC4303] Section 3.1.1. However, the resulting
packet contains outer IP addresses instead of the inner IP addresses
received from the upper layer. The construction of the outer headers
is defined in RFC4301 [RFC4301] Section 5.1.2. The following diagram
illustrates ESP BEET mode positioning for typical IPv4 and IPv6
packets.
IPv4 INNER ADDRESSES
--------------------
BEFORE APPLYING ESP
------------------------------
| inner IP hdr | | |
| | TCP | Data |
------------------------------
AFTER APPLYING ESP, OUTER v4 ADDRESSES
----------------------------------------------------
| outer IP hdr | | | | ESP | ESP |
| (any options) | ESP | TCP | Data | Trailer | ICV |
----------------------------------------------------
|<---- encryption ---->|
|<-------- integrity ------->|
AFTER APPLYING ESP, OUTER v6 ADDRESSES
------------------------------------------------------
| outer | new ext | | | | ESP | ESP |
| IP hdr | hdrs. | ESP | TCP | Data | Trailer| ICV |
------------------------------------------------------
|<--- encryption ---->|
|<------- integrity ------->|
IPv4 INNER ADDRESSES with options
---------------------------------
BEFORE APPLYING ESP
------------------------------
| inner IP hdr | | |
| + options | TCP | Data |
------------------------------
AFTER APPLYING ESP, OUTER v4 ADDRESSES
----------------------------------------------------------
| outer IP hdr | | | | | ESP | ESP |
| (any options) | ESP | PH | TCP | Data | Trailer | ICV |
----------------------------------------------------------
|<------- encryption ------->|
|<----------- integrity ---------->|
AFTER APPLYING ESP, OUTER v6 ADDRESSES
------------------------------------------------------------
| outer | new ext | | | | | ESP | ESP |
| IP hdr | hdrs. | ESP | PH | TCP | Data | Trailer| ICV |
------------------------------------------------------------
|<------ encryption ------->|
|<---------- integrity ---------->|
PH Pseudo Header for IPv4 options
IPv6 INNER ADDRESSES
--------------------
BEFORE APPLYING ESP
------------------------------------------
| | ext hdrs | | |
| inner IP hdr | if present | TCP | Data |
------------------------------------------
AFTER APPLYING ESP, OUTER v6 ADDRESSES
--------------------------------------------------------------
| outer | new ext | | dest | | | ESP | ESP |
| IP hdr | hdrs. | ESP | opts.| TCP | Data | Trailer | ICV |
--------------------------------------------------------------
|<---- encryption ---->|
|<------- integrity ------>|
AFTER APPLYING ESP, OUTER v4 ADDRESSES
----------------------------------------------------
| outer | | dest | | | ESP | ESP |
| IP hdr | ESP | opts.| TCP | Data | Trailer | ICV |
----------------------------------------------------
|<------- encryption -------->|
|<----------- integrity ----------->|
B.1.3. Cryptographic processing
The outgoing packets MUST be protected exactly as in ESP transport
mode [RFC4303]. That is, the upper layer protocol packet is wrapped
into an ESP header, encrypted, and authenticated exactly as if
regular transport mode was used. The resulting ESP packet is subject
to IP header processing as defined in Appendix B.1.4 and
Appendix B.1.5. The incoming ESP protected messages are verified and
decrypted exactly as if regular transport mode was used. The
resulting clear text packet is subject to IP header processing as
defined in Appendix B.1.4 and Appendix B.1.6.
B.1.4. IP header processing
The biggest difference between the BEET mode and the other two modes
is in IP header processing. In the regular transport mode the IP
header is kept intact. In the regular tunnel mode an outer IP header
is created on output and discarded on input. In the BEET mode the IP
header is replaced with another one on both input and output.
On the BEET mode output side, the IP header processing MUST first
ensure that the IP addresses in the original IP header contain the
inner addresses as specified in the SA. This MAY be ensured by
proper policy processing, and it is possible that no checks are
needed at the SA processing time. Once the IP header has been
verified to contain the right IP inner addresses, it is discarded. A
new IP header is created, using the discarded inner header as a hint
for other fields but the IP addresses. The IP addresses in the new
header MUST be the outer tunnel addresses.
On input side, the received IP header is simply discarded. Since the
packet has been decrypted and verified, no further checks are
necessary. A new IP header, corresponding to a tunnel mode inner
header, is created, using the discarded outer header as a hint for
other fields but the IP addresses. The IP addresses in the new
header MUST be the inner addresses.
As the outer header fields are used as hint for creating inner
header, it must be noted that inner header differs as compared to
tunnel-mode inner header. In BEET mode the inner header will have
the TTL, DF-bit and other option values from the outer header. The
TTL, DF-bit and other option values of the inner header MUST be
processed by the stack.
B.1.5. Handling of outgoing packets
The outgoing BEET mode packets are processed as follows:
1. The system MUST verify that the IP header contains the inner
source and destination addresses, exactly as defined in the SA.
This verification MAY be explicit, or it MAY be implicit, for
example, as a result of prior policy processing. Note that in
some implementations there may be no real IP header at this time
but the source and destination addresses may be carried out-of-
band. In case the source address is still unassigned, it SHOULD
be ensured that the designated inner source address would be
selected at a later stage.
2. The IP payload (the contents of the packet beyond the IP header)
is wrapped into an ESP header as defined in [RFC4303] Section
3.3.
3. A new IP header is constructed, replacing the original one. The
new IP header MUST contain the outer source and destination
addresses, as defined in the SA. Note that in some
implementations there may be no real IP header at this time but
the source and destination addresses may be carried out-of-band.
In the case where the source address must be left unassigned, it
SHOULD be made sure that the right source address is selected at
a later stage. Other than the addresses, it is RECOMMENDED that
the new IP header copies the fields from the original IP header.
4. If there are any IPv4 options in the original packet, it is
RECOMMENDED that they are discarded. If the inner header
contains one or more options that need to be transported between
the tunnel end-points, sender MUST encapsulate the options as
defined in Appendix B.1.7
Instead of literally discarding the IP header and constructing a new
one, a conforming implementation MAY simply replace the addresses in
an existing header. However, if the RECOMMENDED feature of allowing
the inner and outer addresses from different address families is
used, this simple strategy does not work.
B.1.6. Handling of incoming packets
The incoming BEET mode packets are processed as follows:
1. The system MUST verify and decrypt the incoming packet
successfully, as defined in [RFC4303] section 3.4. If the
verification or decryption fails, the packet MUST be discarded.
2. The original IP header is simply discarded, without any checks.
Since the ESP verification succeeded, the packet can be safely
assumed to have arrived from the right sender.
3. A new IP header is constructed, replacing the original one. The
new IP header MUST contain the inner source and destination
addresses, as defined in the SA. If the sender has set the ESP
next protocol field to 94 and included the pseudo header as
described in Appendix B.1.7, the receiver MUST include the
options after the constructed IP header. Note, that in some
implementations the real IP header may have already been
discarded and the source and destination addresses are carried
out-of-band. In such case the out-of-band addresses MUST be the
inner addresses. Other than the addresses, it is RECOMMENDED
that the new IP header copies the fields from the original IP
header.
Instead of literally discarding the IP header and constructing a new
one a conforming implementation MAY simply replace the addresses in
an existing header. However, if the RECOMMENDED feature of allowing
the inner and outer addresses from different address families is
used, this simple strategy does not work.
B.1.7. IPv4 options handling
In BEET mode, if IPv4 options are transported inside the tunnel, the
sender MUST include a pseudo-header after ESP header. The pseudo-
header identifies that IPv4 options from the original packet are to
be applied on the packet on input side.
The sender MUST set the next protocol field on the ESP header as 94.
The resulting pseudo header including the IPv4 options MUST be padded
to 8 octet boundary. The padding length is expressed in octets,
valid padding lengths are 0 or 4 octets as the original IPv4 options
are already padded to 4 octet boundary. The padding MUST be filled
with NOP options as defined in Internet Protocol [RFC0791] section
3.1 Internet header format. The padding is added in front of the
original options to ensure that the receiver is able to reconstruct
the original IPv4 datagram. The Header Length field contains the
length of the IPv4 options, and padding in 8 octets units.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Header Len | Pad Len | Reserved |
+---------------+---------------+-------------------------------+
| Padding (if needed) |
+---------------------------------------------------------------+
| IPv4 options ... |
| |
+---------------------------------------------------------------+
Next Header Identifies the data following this header
Length in octets 8-bit unsigned integer. Length of the
pseudo header in 8-octet units, not
including the first 8 octets.
The receiver MUST remove this pseudo-header and padding as a part of
BEET processing, in order reconstruct the original IPv4 datagram.
The IPv4 options included into the pseudo-header MUST be added after
the reconstructed IPv4 (inner) header on the receiving side.
Authors' Addresses Authors' Addresses
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
Robert Moskowitz Robert Moskowitz
ICSAlabs, An Independent Division of Verizon Business Systems ICSAlabs, An Independent Division of Verizon Business Systems
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
Jan Melen
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: jan.melen@nomadiclab.com
Full Copyright Statement
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contained in BCP 78, and except as set forth therein, the authors
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