Host Identity Protocol Heer
Internet-Draft Distributed Systems Group, RWTH
Intended status: Informational Aachen University
Expires: April 29, 2010 Varjonen
Helsinki Institute for Information
Technology
October 26, 2009
HIP Certificates
draft-ietf-hip-cert-02
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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. 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].
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] defines a new cryptographic
namespace based on asymmetric cryptography. Each host's identity is
derived from a public key, allowing hosts to digitally sign data with
their private key. This document specifies a CERT parameter that is
used to transmit digital signatures 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 either carry SPKI certificates or X.509.v3
certificates. It does not specify any certificate semantics.
However, it defines some organizational parameters that help HIP
hosts to transmit semantically grouped parameters in a more
systematic way.
The CERT parameter may be covered by the HIP SIGNATURE field and is a
non-critical parameter.
The CERT parameter can be used in R1, I2, R2, UPDATE and NOTIFY
control packets. Each allowed HIP control packet may contain
multiple CERT parameters. These parameters may be related or
unrelated. Related certificates are managed in Cert groups. A Cert
group specifies a group of related CERT parameters that should be
interpreted in a certain order (e.g. for expressing certificate
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chains). For grouping CERT parameters, the Cert group and the Cert
count field 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 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
be placed in ascending order, within a HIP control packet, according
to their Cert group field. Cert groups may only span multiple
packets if the Cert group does not fit the packet. Only one Cert
group 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 start from 1 up
to Cert count.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cert group | Cert count | Cert ID | Cert type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Certificate /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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:
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+--------------------------------+-------------+
| Cert format | Type number |
+--------------------------------+-------------+
| X.509.v3 | 1 |
| SPKI | 2 |
| URL of X.509.v3 | 3 |
| URL of SPKI | 4 |
| Hash of X.509.v3 | 5 |
| Hash of SPKI | 6 |
| LDAP URL of X.509.v3 | 7 |
| LDAP URL of SPKI | 8 |
| Distinguished Name of X.509.v3 | 9 |
| Distinguished Name of SPKI | 10 |
+--------------------------------+-------------+
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 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) are used as defined in [RFC4306].
Using hash and URL encodings results in smaller HIP control packets,
but requires the receiver to resolve the URL or check local cache
against the hash.
LDAP URL encoding (7 and 8) is used as defined in [RFC2255]. Using
LDAP URL encoding results in smaller HIP control packets, but
requires the receiver to retrieve the certificate or check local
cache against the URL.
Distinguished name (DN) encoding (9 and 10) is used as defined in
[RFC1779]. Using LDAP URL encoding results in smaller HIP control
packets, but requires the receiver to retrieve the certificate or
check local cache against the DN.
3. X.509.v3 Certificate Object and Host Identities
HITs need to be enclosed within the certificates, when using X.509.v3
certificates to transmit information related to HIP hosts. 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 FQDN/NAI from the
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hosts HOST_ID parameter in DN if one exists. Full HIs are presented
in the public key entries of X.509.v3 certificates.
As an example, in a case where the issuer and the subject are both
HIP enabled, the HITs are expressed as follows:
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 to be enclosed within the certificates, when using SPKI
certificates to transmit information related to HIP hosts. 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)
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Appendix A shows a full example SPKI certificate with HIP content.
5. Revocation of Certificates
Revocation of SPKI certificates is handled as defined in Section 5.
in [RFC2693] Revocation of X.509.v3 certificates is handled as
defined in Section 5 in [RFC2459].
6. Signaling
HIP end-hosts and HIP-aware middleboxes need to inform, the initiator
or the responder, of the need for a certificate or need for a chain
of certificates. They also need a way to inform about failing to
meet required conditions. HIP services [HIP.service] describes the
signaling. Signaling for the requirements and failures with
certificates is described in Section 4.1 of [HIP.service].
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 and Cert ID namespaces are managed locally by each host
that sends CERT parameters in HIP control packets.
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. 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 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.
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9. Acknowledgements
The authors would like to thank M. Komu and T. Henderson of fruitful
conversations on the subject.
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://
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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. 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=|
)
)
)
(cert
(issuer
(hash hit 2001:0014:06cf:fae7:bb79:bf78:7d64:c056)
)
(subject
(hash hit 2001:0014:06cf:fae7:bb79:bf78:7d64:c056)
)
(not-before "2008-07-12_22:11:07")
(not-after "2008-07-22_22:11:07")
)
(signature
(hash sha1 |kfElDhagiK0Bsqtj32Gq3t/1mxgA|)
|HiIqjjZIUzypvoxQyO0UovPm5uC4Xte0scEcBnENDIfn2DNy/bAtxGEdKq4O
dW80vTCmkF8/HXclgXLLVch3DxRNdSbYiiks000HpQt/OKqlTH+uUHBcHOAo
E42LmDskM9T5KQJoC/CH7871zfvojPnpkl2dUngOWv4q0r/wSJ0=|
)
)
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.
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Certificate:
Data:
Version: 3 (0x2)
Serial Number: 0 (0x0)
Signature Algorithm: sha1WithRSAEncryption
Issuer: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056
Validity
Not Before: Jul 12 18:58:38 2008 GMT
Not After : Jul 22 18:58:38 2008 GMT
Subject: CN=2001:14:6cf:fae7:bb79:bf78:7d64:c056
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
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Basic Constraints:
CA:TRUE
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
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
Appendix C. Change log
Changes from version 00 to 01:
o Revised text about DN usage.
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o Revised text about Cert group usage.
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 4
Helsinki
Finland
Fax: +35896949768
Email: samu.varjonen@hiit.fi
URI: http://www.hiit.fi
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