One document matched: draft-ietf-hip-cert-00.txt
Host Identity Protocol Heer
Internet-Draft Distributed Systems Group, RWTH
Intended status: Informational Aachen University
Expires: April 24, 2009 Varjonen
Helsinki Institute for Information
Technology
October 21, 2008
HIP Certificates
draft-ietf-hip-cert-00
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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
Simple Public Key Infrastructure (SPKI) and X.509.v3 certificates.
It is used for carrying these certificates in HIP control messages.
Additionally, this document specifies the representations of Host
Identity Tags in SPKI and X.509.v3 certificates.
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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 the CERT parameter that
is used to transmit digital signatures in HIP. It corresponds to the
placeholder specified in Section 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.
Each HIP packet may contain multiple CERT parameters. If these
parameters must be handled in certain sequence, 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 grouped CERT
parameters.
CERT parameters that belong to the same CERT group may be contained
in multiple sequential packets. This is indicated by a higher Cert
count than the amount of CERT parameters with matching Cert group
fields in a packet. Within a HIP packet, CERT parameters must be
placed in ascending order 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.
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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.
The CERT parameter can be used in R1, I2, R2, UPDATE and NOTIFY
messages. When CERT parameter is used in R1 message it is NOT
recommended to use grouping or hash and URL encodings. Initiator and
Responder can detect middleboxes on the path after R1 message is sent
by checking if control packets contain ECHO_REQUEST_M parameters as
defined in [HIP.middle_auth].
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 |
+--------------------------+-------------+
| SPKI | 1 |
| X.509.v3 | 2 |
| Hash and URL of SPKI | 3 |
| Hash and URL of X.509.v3 | 4 |
+--------------------------+-------------+
All implementations MUST support SPKI. The next section outlines the
use of HITs in SPKI. The SPKI and its formats are defined in
[RFC2693]. X.509.v3 certificates are defined in [RFC3280]. Wire
format for X.509.v3 is Distinguished Encoding Rules format as defined
in [X.690].
Hash and URL encodings (3 and 4) 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.
It is not recommended to use hash and URL encodings when HIP-aware
middleboxes are present on the communication path between peers
because fetching remote certificates requires 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.
3. SPKI Cert Object and Host Identities
When using SPKI certificates to transmit information related to HIP
hosts, HITs need to be enclosed within the certificates. 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.
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.
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4. X.509.v3 Certificate Object and Host Identities
When using X.509.v3 certificates to transmit information related to
HIP hosts, HITs need to be enclosed within the certificates. HITs
are represented as issuer and subject alternative name X.509.v3
extensions as defined in [RFC2459]. Because the Distinguished Name
(DN) in X.509.v3 certificate cannot be empty HITs are also placed
into the Common Name (CN) in a colon delimited presentation format.
As an example the HIT of a host is 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.
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. 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
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Cert Group and Cert ID namespaces are managed locally by each peer
that sends CERT parameters in HIP packets.
7. 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).
8. Acknowledgements
The authors would like to thank M. Komu and T. Henderson of fruitful
conversations on the subject.
9. References
9.1. Normative References
[HIP.middle_auth]
Heer, T., "End-Host Authentication for HIP Middleboxes",
<draft-heer-hip-middle-auth-00.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 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.
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9.2. 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. 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=|
)
)
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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.
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
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Authors' Addresses
Tobias Heer
Distributed Systems Group, RWTH Aachen University
Ahornstrasse 55
Aachen
Germany
Phone: +49 241 80 214 36
Email: heer@cs.rwth-aachem.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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