Host Identity Protocol Heer
Internet-Draft Distributed Systems Group, RWTH
Intended status: Experimental Aachen University
Expires: March 27, 2011 Varjonen
Helsinki Institute for Information
Technology
September 23, 2010
HIP Certificates
draft-ietf-hip-cert-04
Abstract
The CERT parameter is a container for X.509.v3 certificates and
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 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] defines a new cryptographic
namespace based on asymmetric cryptography. The identity of each
host is derived from a public key, allowing hosts to digitally sign
data with their private key. This document specifies the CERT
parameter, which is used to transmit digital certificates in HIP. It
fills the placeholder specified in Section 5.2 of [RFC5201].
2. CERT Parameter
The CERT parameter is a container for 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 supplementary parameters that help HIP hosts to
transmit semantically grouped CERT parameters in a more systematic
way. The specific use of the CERT parameter for different use cases
is intentionally not discussed in this document.
The CERT parameter is covered, when present, by the HIP SIGNATURE
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field and is a non-critical parameter.
The CERT parameter can be used in all HIP packets but using it in the
I1 packet is not recommended because it can increase the processing
times of I1s, which can be problematic when processing storms of I1s.
Each 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 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 a single
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.
The Cert Group and Cert ID namespaces are managed locally by each
host that sends CERT parameters in HIP control packets.
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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:
+--------------------------------+-------------+
| Cert format | Type number |
+--------------------------------+-------------+
| X.509.v3 | 1 |
| SPKI | 2 |
| Hash and URL of X.509.v3 | 3 |
| Hash and URL of SPKI | 4 |
| LDAP URL of X.509.v3 | 5 |
| LDAP URL of SPKI | 6 |
| Distinguished Name of X.509.v3 | 7 |
| Distinguished Name of SPKI | 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 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 4) are used as defined in [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.
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LDAP URL encodings (5 and 6) are 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 a local cache
against the URL.
Distinguished name (DN) encodings (7 and 8) are used as defined in
[RFC1779]. Using 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
When using X.509.v3 certificates to transmit information related to
HIP 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. The full HIs
are presented in the public key entries of X.509.v3 certificates.
The following example illustrates a case in which the issuer and the
subject are both HIP enabled.
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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.
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 configured to compute HITs and
include them in the 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.
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4. 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. 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 X.509.v3 certificates is handled as defined in Section
5 in [RFC2459]. Revocation of SPKI certificates is handled as
defined in Section 5 in [RFC2693].
6. 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 the Initiator by
sending a HIP NOTIFY message with NOTIFICATION parameter error type
CREDENTIALS_NEEDED.
If the verification of a certificate fails, a verifier MAY signal
this to the provider of the certificate by sending a HIP NOTIFY
message with NOTIFICATION parameter error type INVALID_CERTIFICATE.
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NOTIFICATION PARAMETER - ERROR TYPES Value
------------------------------------ -----
CREDENTIALS_REQUIRED 48
The Responder is unwilling to set up an association
as the Initiator did not send the needed credentials.
INVALID_CERTIFICATE 50
Sent in response to a failed verification of 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 parameter has 8-bit unsigned integer field for different
certificate types, for which IANA is to create and maintain a new
sub-registry entitled "HIP certificate types" under the "Host
Identity Protocol (HIP) Parameters". Initial values for the
Certificate type registry are given in 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, 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 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 A. Keranen, D. Mattes, M. Komu and T.
Henderson 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
[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>.
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Appendix A. SPKI certificate example
This section shows a SPKI certificate with encoded HITs. The example
has been indented for readability.
(sequence
(public_key
(rsa-pkcs1-sha1
(e #010001#)
(n |uV7M1dl7OcJCPnlJrX8MvQ8SmE6wne5idnp7VfDMolestu
JqvB69z3UwlVuSr3VVaQvDSA+15BUweYkis/1+UVnSDdcS
XUTz6AUTH1tPifoebYPp4s+9XG/vAh7I25pImjW4uL6Jvq
vI3WBE36wBt3Zmq12hpdA8jSIE1CRZYA8=|
)
)
)
(cert
(issuer
(hash hit 2001:001e:d709:1980:5c6a:bb0c:7650:a027)
)
(subject
(hash hit 2001:001c:5a14:26de:a07c:385b:de35:60e3)
)
(not-before "2010-06-22_16:40:47")
(not-after "2010-07-02_16:40:47")
)
(signature
(hash sha1 |+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 X.509.v3 certificate with encoded HITs.
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Certificate:
Data:
Version: 3 (0x2)
Serial Number: 0 (0x0)
Signature Algorithm: sha1WithRSAEncryption
Issuer: CN=2001:1e:d709:1980:5c6a:bb0c:7650:a027
Validity
Not Before: Jun 22 13:39:32 2010 GMT
Not After : Jul 2 13:39:32 2010 GMT
Subject: 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: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 Issuer Alternative Name:
IP Address:2001:1E:D709:1980:5C6A:BB0C:7650:A027
X509v3 Subject Alternative Name:
IP Address:2001:1C:5A14:26DE:A07C:385B:DE35:60E3
Signature Algorithm: sha1WithRSAEncryption
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.
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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
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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-aachen.de
URI: http://ds.cs.rwth-aachen.de/members/heer
Samu Varjonen
Helsinki Institute for Information Technology
Metsaenneidonkuja 4
Helsinki
Finland
Email: samu.varjonen@hiit.fi
URI: http://www.hiit.fi
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