wdiff draft-ietf-hip-cert-03.txt draft-ietf-hip-cert-04.txt

Host Identity Protocol Heer
Internet-Draft Distributed Systems Group, RWTH
Intended status: Informational Experimental Aachen University
Expires: October 30, 2010 March 27, 2011 Varjonen
Helsinki Institute for Information
Technology
April 28,
September 23, 2010

HIP Certificates
draft-ietf-hip-cert-03
draft-ietf-hip-cert-04

Abstract

This document specifies a certificate parameter called CERT for the
Host Identity Protocol (HIP).

The CERT parameter is a container for X.509.v3 certificates and for
Simple Public Key Infrastructure (SPKI) certificates. It is used for
carrying these certificates in HIP control packets. This document
only specifies the certificate parameter and the error signaling in
case of a failed verification. The use of certificates including how
certificates are obtained, requested, and which actions are taken
upon successful or failed verification are to be defined in the
documents that use the certificate parameter. Additionally, this
document specifies the representations of Host Identity Tags in
X.509.v3 and in SPKI certificates.

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

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provisions of BCP 78 and BCP 79. This document may not be modified,
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1. Introduction

Digital certificates bind a piece of information to a public key by
means of a digital signature, and thus, enable the holder of a
private key to generate cryptographically verifiable statements. The
Host Identity Protocol (HIP)[RFC5201] (HIP) [RFC5201] defines a new cryptographic
namespace based on asymmetric cryptography. Each host's The identity of each
host is derived from a public key, allowing hosts to digitally sign
data with their private key. This document specifies a the CERT parameter that
parameter, which is used to transmit digital signatures certificates in HIP. It
fills the placeholder specified in Section 5.2 of [RFC5201].

2. CERT Parameter

The CERT parameter is a container for a certain types of digital
certificates. It may MAY either carry SPKI certificates or X.509.v3
certificates. It does not specify any certificate semantics.
However, it defines some organizational supplementary parameters that help HIP hosts to
transmit semantically grouped CERT parameters in a more systematic
way. The specific use of the CERT parameter may be covered for different use cases
is intentionally not discussed in this document.

The CERT parameter is covered, when present, by the HIP SIGNATURE
field and is a non-critical parameter.

The CERT parameter can be used in all HIP packets but using CERT it in the
I1 packet is NOT RECOMMENDED. not recommended because it can increase the processing
times of I1s, which can be problematic when processing storms of I1s.
Each allowed HIP control packet may MAY contain multiple CERT parameters. These
parameters may MAY be related or unrelated. Related certificates are
managed in Cert groups. A Cert group specifies a group of related
CERT parameters that should SHOULD be interpreted in a certain order (e.g.
for expressing certificate chains). For grouping CERT parameters,
the Cert group and the Cert count field must MUST be set. Ungrouped
certificates exhibit a unique Cert group field and set the Cert count
to 1. CERT parameters with the same Cert group number in the group
field indicate a logical grouping. The Cert count field indicates
the number of CERT parameters in the group.

CERT parameters that belong to the same Cert group may MAY be contained
in multiple sequential HIP control packets. This is indicated by a
higher Cert count than the amount of CERT parameters with matching
Cert group fields in a HIP control packet. The CERT parameters must MUST
be placed in ascending order, within a HIP control packet, according
to their Cert group field. Cert groups may MAY only span multiple
packets if the Cert group does not fit the packet. Only one a single
Cert group may MAY span two subsequent packets.

The Cert ID acts as a sequence number to identify the certificates in
a Cert group. The numbers in the Cert ID field must MUST start from 1 up
to Cert count.

The Cert Group and Cert ID namespaces are managed locally by each
host that sends CERT parameters in HIP control packets.

Type 768
Length Length in octets, excluding Type, Length, and Padding
Cert group Group ID grouping multiple related CERT parameters
Cert count Total count of certificates that are sent, possibly
in several consecutive HIP control packets.
Cert ID The sequence number for this certificate
Cert Type Describes the type of the certificate
Padding Any Padding, if necessary, to make the TLV a multiple
of 8 bytes.

The following certificate types are defined:

+--------------------------------+-------------+
| Cert format | Type number |
+--------------------------------+-------------+
| X.509.v3 | 1 |
| SPKI | 2 |
| Hash and URL of X.509.v3 | 3 |
| Hash and URL of SPKI | 4 |
| Hash of X.509.v3 | 5 |
| Hash of SPKI | 6 |
| LDAP URL of X.509.v3 | 7 5 |
| LDAP URL of SPKI | 8 6 |
| Distinguished Name of X.509.v3 | 9 7 |
| Distinguished Name of SPKI | 10 8 |
+--------------------------------+-------------+

The next sections outline the use of HITs in X.509.v3 and in SPKI
certificates. X.509.v3 certificates are defined in [RFC3280]. The
Wire
wire format for X.509.v3 is Distinguished Encoding Rules format as
defined in [X.690]. The SPKI and its formats are defined in
[RFC2693].

Hash and URL encodings (3 to 6) 4) are used as defined in [RFC4306]. [RFC4306]
Section 3.6. Using hash and URL encodings results in smaller HIP
control packets, but requires the receiver to resolve the URL or
check a local cache against the hash.

LDAP URL encoding (7 encodings (5 and 8) is 6) are used as defined in [RFC2255]. Using
LDAP URL encoding results in smaller HIP control packets, packets but requires
the receiver to retrieve the certificate or check a local cache
against the URL.

Distinguished name (DN) encoding (9 encodings (7 and 10) is 8) are used as defined in
[RFC1779]. Using LDAP URL the DN encoding results in smaller HIP control
packets, but requires the receiver to retrieve the certificate or
check a local cache against the DN.

3. X.509.v3 Certificate Object and Host Identities

HITs need to be enclosed within the certificates, when

When using X.509.v3 certificates to transmit information related to
HIP hosts. hosts, HITs MAY be enclosed within the certificates. HITs can
represent an issuer, a subject, or both. In X.509.v3 HITs are
represented as issuer and subject alternative name extensions as
defined in [RFC2459]. If only HIP information is presented as either
the issuer or the subject the HIT is also placed into the respective
entity's DNs Common Name (CN) section in a colon delimited
presentation format. Inclusion of CN is not necessary if DN contains
any other information. It is RECOMMENDED to use the FQDN/NAI from
the hosts HOST_ID parameter in the DN if one exists. Full The full HIs
are presented in the public key entries of X.509.v3 certificates.

As an example, in

The following example illustrates a case where in which the issuer and the
subject are both HIP enabled, the HITs are expressed as follows: enabled.

Format:
Issuer: CN=hit-of-host
Subject: CN=hit-of-host

X509v3 extensions:
X509v3 Issuer Alternative Name:
IP Address:HIT-OF-HOST
X509v3 Subject Alternative Name:
IP Address:HIT-OF-HOST

Example:
Issuer: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056
Subject: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056

X509v3 extensions:
X509v3 Issuer Alternative Name:
IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056
X509v3 Subject Alternative Name:
IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056

Appendix B shows a full example X.509.v3 certificate with HIP
content.

4. SPKI Cert Object and Host Identities

HITs need

As another example, consider a managed PKI environment in which the
peers have certificates that are anchored in (potentially different)
managed trust chains. In this scenario, the certificates issued to
HIP hosts are signed by intermediate Certificate Authorities (CAs) up
to a root CA. In this example, the managed PKI environment is
neither HIP aware, nor can it be enclosed within configured to compute HITs and
include them in the certificates, when certificates.

In this scenario, it is recommended that the HIP peers have and use
some mechanism of defining trusted root CAs for the purpose of
establishing HIP communications. Furthermore it is recommended that
the HIP peers have and use some mechanism of checking peer
certificate validity for revocation, signature, minimum cryptographic
strength, etc., up to the trusted root CA.

When HIP communications are established, the HIP hosts not only need
to send their identity certificates (or pointers to their
certificates), but also the chain of intermediate CAs (or pointers to
the CAs) up to the root CA, or to a CA that is trusted by the remote
peer. This chain of certificates MUST be sent in a Cert group as
specified in Section 2. The HIP peers validate each other's
Certificates and compute peer HITs based on the Certificate public
keys.

4. SPKI Cert Object and Host Identities

When using SPKI certificates to transmit information related to HIP hosts.
hosts, HITs need to be enclosed within the certificates. HITs can
represent an issuer, a subject, or both. In the following we define
the representation of those identifiers for SPKI given as
S-expressions. Note that the S-expressions are only the human-
readable representation of SPKI certificates. Full HIs are presented
in the public key sequences of SPKI certificates.

As an example the Host Identity Tag of a host is expressed as
follows:

Format: (hash hit hit-of-host)
Example: (hash hit 2001:13:724d:f3c0:6ff0:33c2:15d8:5f50)

Appendix A shows a full example SPKI certificate with HIP content.

5. Revocation of Certificates

Revocation of SPKI X.509.v3 certificates is handled as defined in Section 5.
5 in [RFC2693] [RFC2459]. Revocation of X.509.v3 SPKI certificates is handled as
defined in Section 5 in [RFC2459]. [RFC2693].

6. Signaling

HIP end-hosts and HIP-aware middleboxes need Error signaling

If the Initiator does not send the certificate that the Responder
requires the Responder may take actions (e.g. blocking the
connection). The Responder MAY signal this to inform, the initiator
or Initiator by
sending a HIP NOTIFY message with NOTIFICATION parameter error type
CREDENTIALS_NEEDED.

If the responder, verification of the need for a certificate or need for a chain
of certificates. They also need fails, a way to inform about failing verifier MAY signal
this to
meet required conditions. HIP services [HIP.service] describes the
signaling. Signaling for provider of the requirements and failures certificate by sending a HIP NOTIFY
message with
certificates NOTIFICATION parameter error type INVALID_CERTIFICATE.

NOTIFICATION PARAMETER - ERROR TYPES Value
------------------------------------ -----

CREDENTIALS_REQUIRED 48

The Responder is described unwilling to set up an association
as the Initiator did not send the needed credentials.

INVALID_CERTIFICATE 50

Sent in Section 4.1 response to a failed verification of [HIP.service]. a certificate.
Notification Data contains 4 octets, in order Cert group,
Cert count, Cert ID, and Cert type of the certificate
parameter that caused the failure.

7. IANA Considerations

This document defines the CERT parameter for the Host Identity
Protocol [RFC5201]. This parameter is defined in Section 2 with type
768. The parameter type number is also defined in [RFC5201].

The
Cert Group CERT parameter has 8-bit unsigned integer field for different
certificate types, for which IANA is to create and Cert ID namespaces maintain a new
sub-registry entitled "HIP certificate types" under the "Host
Identity Protocol (HIP) Parameters". Initial values for the
Certificate type registry are managed locally by each host
that sends CERT parameters given in HIP control packets. Section 2.

In Section 6 this document defines two new types for "NOTIFY message
types" sub-registry under "Host Identity Protocol (HIP) Parameters".

8. Security Considerations

Certificate grouping allows the certificates to be sent in multiple
consecutive packets. This might allow similar attacks as IP-layer
fragmentation allows, i.e. for example sending of fragments in wrong order
and skipping some fragments to delay or stall packet processing by
the victim in order to use resources (e.g. CPU or memory).

It is not recommended to use grouping or hash and URL encodings when
HIP-aware
HIP aware middleboxes are anticipated to be present on the
communication path between peers because fetching remote certificates
require the middlebox to buffer the packets and to request remote
data. This makes these devices prone to denial of service (DoS)
attacks. Moreover, middleboxes and responders that request remote
certificates can be used as deflectors for distributed denial of
service attacks.

9. Acknowledgements

The authors would like to thank A. Keranen, D. Mattes, M. Komu and T.
Henderson of for the fruitful conversations on the subject. D. Mattes
most notably contributed the non-HIP aware use case in Section 3.

10. References

10.1. Normative References

[HIP.service]
Heer, T., Wirtz, H., and S. Varjonen, "Service Identifiers
for HIP", <draft-heer-hip-service-00.txt>.

[RFC1779] Kille, S., "A String Representation of Distinguished
Names", RFC 1779, March 1995.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2255] Howes, T. and M. Smith, "The LDAP URL Format", RFC 2255,
December 1997.

[RFC2459] Housley, R., Ford, W., Polk, T., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and CRL
Profile", RFC 2459, January 1999.

[RFC2693] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas,
B., and T. Ylonen, "SPKI Certificate Theory", RFC 2693,
September 1999.

[RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002.

[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.

[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
"Host Identity Protocol", RFC 5201, April 2008.

10.2. Informative References

[X.690] ITU-T, "Recommendation X.690 Information Technology -
ASN.1 encoding rules: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", July 2002, <http://
www.itu.int/ITU-T/studygroups/com17/languages/
X.690-0207.pdf>.

Appendix A. SPKI certificate example

This section shows a self-signed SPKI certificate of HIT 2001:14:6cf:
fae7:bb79:bf78:7d64:c056. with encoded HITs. The example
has been indented for readability.

(sequence
(public_key
(rsa-pkcs1-sha1
(e #010001#)
(n |n1CheoELqYRSkHYMQddub2TpILl+6H9wC/as6zFCZqOY43hsZgAjG0F
GoQwtyOyQjzO2Ykb2TmUCZemTYui/sR0zIbdwg1xafKl7ggZDkhk5an
PtGDxJxFalTYo6/A5ZQv8uatbaJgB/G7VM8G+O9HLucadad2zQUXpQf
gbK3S8=| |uV7M1dl7OcJCPnlJrX8MvQ8SmE6wne5idnp7VfDMolestu
JqvB69z3UwlVuSr3VVaQvDSA+15BUweYkis/1+UVnSDdcS
XUTz6AUTH1tPifoebYPp4s+9XG/vAh7I25pImjW4uL6Jvq
vI3WBE36wBt3Zmq12hpdA8jSIE1CRZYA8=|
)
)
)
(cert
(issuer
(hash hit 2001:0014:06cf:fae7:bb79:bf78:7d64:c056) 2001:001e:d709:1980:5c6a:bb0c:7650:a027)
)
(subject
(hash hit 2001:0014:06cf:fae7:bb79:bf78:7d64:c056) 2001:001c:5a14:26de:a07c:385b:de35:60e3)
)
(not-before "2008-07-12_22:11:07") "2010-06-22_16:40:47")
(not-after "2008-07-22_22:11:07") "2010-07-02_16:40:47")
)
(signature
(hash sha1 |kfElDhagiK0Bsqtj32Gq3t/1mxgA|)
|HiIqjjZIUzypvoxQyO0UovPm5uC4Xte0scEcBnENDIfn2DNy/bAtxGEdKq4O
dW80vTCmkF8/HXclgXLLVch3DxRNdSbYiiks000HpQt/OKqlTH+uUHBcHOAo
E42LmDskM9T5KQJoC/CH7871zfvojPnpkl2dUngOWv4q0r/wSJ0=| |+UzjNn5+bXo3aMZQNGGtapKdlFAA|)
|Fhioyxi0mpHa2aq2ofhotsauYyDuCa45mMAQ+yTEGOzcc1K+Prx
+O6kFecKxl+Cwz9qXEI6a/zfAnZqLj18yvszM1D/tH+W3RKl2LW
+lASsCDKXOi9ObNx+Dwzj3YlHABPxt4gGk0XVadEMXfCPDqiLF+
zMR9fW5/OaJ+vRwhKs=|
)
)

Appendix B. X.509.v3 certificate example

This section shows a self-signed X.509.v3 certificate of HIT 2001:14:
6cf:fae7:bb79:bf78:7d64:c056. with encoded HITs.

Certificate:
Data:
Version: 3 (0x2)
Serial Number: 0 (0x0)
Signature Algorithm: sha1WithRSAEncryption
Issuer: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056 CN=2001:1e:d709:1980:5c6a:bb0c:7650:a027
Validity
Not Before: Jul 12 18:58:38 2008 Jun 22 13:39:32 2010 GMT
Not After : Jul 22 18:58:38 2008 2 13:39:32 2010 GMT
Subject: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056 CN=2001:1c:5a14:26de:a07c:385b:de35:60e3
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public Key: (1024 bit)
Modulus (1024 bit):
00:9f:50:a1:7a:81:0b:a9:84:52:90:76:0c:41:d7:
6e:6f:64:e9:20:b9:7e:e8:7f:70:0b:f6:ac:eb:31:
42:66:a3:98:e3:78:6c:66:00:23:1b:41:46:a1:0c:
2d:c8:ec:90:8f:33:b6:62:46:f6:4e:65:02:65:e9:
93:62:e8:bf:b1:1d:33:21:b7:70:83:5c:5a:7c:a9:
7b:82:06:43:92:19:39:6a:73:ed:18:3c:49:c4:56:
a5:4d:8a:3a:fc:0e:59:42:ff:2e:6a:d6:da:26:00:
7f:1b:b5:4c:f0:6f:8e:f4:72:ee:71:a7:5a:77:6c:
d0:51:7a:50:7e:06:ca:dd:2f
00:b9:5e:cc:d5:d9:7b:39:c2:42:3e:79:49:ad:7f:
0c:bd:0f:12:98:4e:b0:9d:ee:62:76:7a:7b:55:f0:
cc:a2:57:ac:b6:e2:6a:bc:1e:bd:cf:75:30:95:5b:
92:af:75:55:69:0b:c3:48:0f:b5:e4:15:30:79:89:
22:b3:fd:7e:51:59:d2:0d:d7:12:5d:44:f3:e8:05:
13:1f:5b:4f:89:fa:1e:6d:83:e9:e2:cf:bd:5c:6f:
ef:02:1e:c8:db:9a:48:9a:35:b8:b8:be:89:be:ab:
c8:dd:60:44:df:ac:01:b7:76:66:ab:5d:a1:a5:d0:
3c:8d:22:04:d4:24:59:60:0f
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Basic Constraints:
CA:TRUE
X509v3 Issuer Alternative Name:
IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056 Address:2001:1E:D709:1980:5C6A:BB0C:7650:A027
X509v3 Subject Alternative Name:
IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056 Address:2001:1C:5A14:26DE:A07C:385B:DE35:60E3
Signature Algorithm: sha1WithRSAEncryption
19:32:0b:72:a8:6c:f9:65:20:5b:1d:9a:e1:c7:39:97:c7:8a:
4d:d1:01:f9:7d:0b:0d:6f:61:a2:e3:2c:62:30:28:f6:36:db:
62:bc:7f:d1:9b:6d:cc:da:e3:9b:90:e7:53:9e:55:28:51:7e:
39:de:23:24:f5:a9:97:7a:ba:ce:54:3e:cf:8b:68:04:f6:be:
78:94:9f:d3:20:62:96:14:84:51:af:c7:ba:30:ae:b1:d6:7e:
7f:32:42:9c:f6:f5:76:27:0a:28:58:8b:b5:85:e7:e9:5a:ff:
aa:4c:57:55:95:09:33:ac:0b:8c:fd:05:4a:5e:60:e7:7f:d7:
42:f0
48:a1:25:fb:01:31:d9:80:76:1b:1a:2d:00:f1:26:22:3c:3b:
20:a0:cb:b2:28:d2:0c:21:d3:9e:3b:4a:ab:3d:f6:ea:ad:46:
f6:f5:c4:4f:71:ce:3e:7b:65:8d:58:75:2e:99:25:82:5f:73:
10:c6:c2:f0:4b:35:ff:5c:65:ac:fc:a4:a7:76:50:ab:62:50:
b8:86:21:e6:83:e1:c1:3d:20:c9:8e:13:ab:d7:4b:d4:ab:2d:
72:9d:f0:9f:5f:e0:6f:95:fa:a1:95:64:3f:74:63:e5:a8:1d:
f7:e6:48:98:33:53:7b:91:6d:b0:cb:af:32:15:8c:e0:01:a0:
a0:b8

Appendix C. Change log

Changes from version 00 to 01:

o Revised text about DN usage.

o Revised text about Cert group usage.

Changes from version 01 to 02:

o Revised the type numbers.

o Added a section about signaling.

Changes from version 02 to 03:

o Revised text about CERT use in control packets.

Changes from version 03 to 04:

o Added the non-HIP aware use case to the Section 3.

o Clarified that the HITs are not always required in the
certificates.

o Rewrote the signaling section.

o LDAP URL to LDAP DN in Section 2 last paragraph.

o CERT is always covered by a signature as it's type number requires

o New example certificates

o Style and language clean-ups

o Changed IANA considerations

o Revised the type numbers

o RFC 2119 keywords

o Updated the IANA considerations section

o Rewrote the abstract

Authors' Addresses

Tobias Heer
Distributed Systems Group, RWTH Aachen University
Ahornstrasse 55
Aachen
Germany

Phone: +49 241 80 214 36
Email: heer@cs.rwth-aachen.de
URI: http://ds.cs.rwth-aachen.de/members/heer

Samu Varjonen
Helsinki Institute for Information Technology
Metsnneidonkuja
Metsaenneidonkuja 4
Helsinki
Finland

Fax: +35896949768

Email: samu.varjonen@hiit.fi
URI: http://www.hiit.fi