draft-ietf-hip-cert-01.txt   draft-ietf-hip-cert-02.txt 
Host Identity Protocol Heer Host Identity Protocol Heer
Internet-Draft Distributed Systems Group, RWTH Internet-Draft Distributed Systems Group, RWTH
Intended status: Informational Aachen University Intended status: Informational Aachen University
Expires: January 2, 2010 Varjonen Expires: April 29, 2010 Varjonen
Helsinki Institute for Information Helsinki Institute for Information
Technology Technology
July 1, 2009 October 26, 2009
HIP Certificates HIP Certificates
draft-ietf-hip-cert-01 draft-ietf-hip-cert-02
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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Abstract Abstract
This document specifies a certificate parameter called CERT for the This document specifies a certificate parameter called CERT for the
Host Identity Protocol (HIP). The CERT parameter is a container for Host Identity Protocol (HIP). The CERT parameter is a container for
Simple Public Key Infrastructure (SPKI) and X.509.v3 certificates. X.509.v3 certificates and for Simple Public Key Infrastructure (SPKI)
It is used for carrying these certificates in HIP control messages. certificates. It is used for carrying these certificates in HIP
Additionally, this document specifies the representations of Host control packets. Additionally, this document specifies the
Identity Tags in SPKI and X.509.v3 certificates. representations of Host Identity Tags in X.509.v3 and in SPKI
certificates.
Requirements Language Requirements Language
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].
1. Introduction 1. Introduction
Digital certificates bind a piece of information to a public key by Digital certificates bind a piece of information to a public key by
means of a digital signature, and thus, enable the holder of a means of a digital signature, and thus, enable the holder of a
private key to generate cryptographically verifiable statements. The private key to generate cryptographically verifiable statements. The
Host Identity Protocol (HIP)[RFC5201] defines a new cryptographic Host Identity Protocol (HIP)[RFC5201] defines a new cryptographic
namespace based on asymmetric cryptography. Each host's identity is namespace based on asymmetric cryptography. Each host's identity is
derived from a public key, allowing hosts to digitally sign data with derived from a public key, allowing hosts to digitally sign data with
their private key. This document specifies the CERT parameter that their private key. This document specifies a CERT parameter that is
is used to transmit digital signatures in HIP. It corresponds to the used to transmit digital signatures in HIP. It fills the placeholder
placeholder specified in Section 2 of [RFC5201]. specified in Section 5.2 of [RFC5201].
2. CERT Parameter 2. CERT Parameter
The CERT parameter is a container for a certain types of digital 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 may either carry SPKI certificates or X.509.v3
certificates. It does not specify any certificate semantics. certificates. It does not specify any certificate semantics.
However, it defines some organizational parameters that help HIP However, it defines some organizational parameters that help HIP
hosts to transmit semantically grouped parameters in a more hosts to transmit semantically grouped parameters in a more
systematic way. systematic way.
The CERT parameter may be covered by the HIP SIGNATURE field and is a The CERT parameter may be covered by the HIP SIGNATURE field and is a
non-critical parameter. non-critical parameter.
Each HIP packet may contain multiple CERT parameters. These The CERT parameter can be used in R1, I2, R2, UPDATE and NOTIFY
parameters may be related or unrelated. Related certificates are control packets. Each allowed HIP control packet may contain
managed in Cert groups. A cert group specifies a group of related multiple CERT parameters. These parameters may be related or
cert parameters that should be interpreted in a certain order (e.g. unrelated. Related certificates are managed in Cert groups. A Cert
for expressing certificate chains). For grouping Cert parameters, group specifies a group of related CERT parameters that should be
the Cert group and the Cert count field must be set. Ungrouped interpreted in a certain order (e.g. for expressing certificate
certificates exhibit a unique Cert group field and set the Cert count chains). For grouping CERT parameters, the Cert group and the Cert
to 1. CERT parameters with the same Cert group number in the group count field must be set. Ungrouped certificates exhibit a unique
field indicate a logical grouping. The Cert count field indicates Cert group field and set the Cert count to 1. CERT parameters with
the number of CERT parameters in the group. 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 CERT parameters that belong to the same Cert group may be contained
in multiple sequential packets. This is indicated by a higher Cert in multiple sequential HIP control packets. This is indicated by a
count than the amount of CERT parameters with matching Cert group higher Cert count than the amount of CERT parameters with matching
fields in a packet. Within a HIP packet, CERT parameters must be Cert group fields in a HIP control packet. The CERT parameters must
placed in ascending order according to their Cert group field. Cert be placed in ascending order, within a HIP control packet, according
groups may only span multiple packets if the Cert group does not fit to their Cert group field. Cert groups may only span multiple
the packet. Only one Cert group may span two subsequent packets. 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 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 a Cert group. The numbers in the Cert ID field must start from 1 up
to Cert count. 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
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cert group | Cert count | Cert ID | Cert type | | Cert group | Cert count | Cert ID | Cert type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Certificate / | Certificate /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Padding | / | Padding |
skipping to change at page 4, line 5 skipping to change at page 4, line 5
Cert group Group ID grouping multiple related CERT parameters Cert group Group ID grouping multiple related CERT parameters
Cert count Total count of certificates that are sent, possibly Cert count Total count of certificates that are sent, possibly
in several consecutive HIP control packets. in several consecutive HIP control packets.
Cert ID The sequence number for this certificate Cert ID The sequence number for this certificate
Cert Type Describes the type of the certificate Cert Type Describes the type of the certificate
Padding Any Padding, if necessary, to make the TLV a multiple Padding Any Padding, if necessary, to make the TLV a multiple
of 8 bytes. of 8 bytes.
The following certificate types are defined: The following certificate types are defined:
+--------------------------+-------------+ +--------------------------------+-------------+
| Cert format | Type number | | Cert format | Type number |
+--------------------------+-------------+ +--------------------------------+-------------+
| SPKI | 1 | | X.509.v3 | 1 |
| X.509.v3 | 2 | | SPKI | 2 |
| Hash and URL of SPKI | 3 | | URL of X.509.v3 | 3 |
| Hash and URL of X.509.v3 | 4 | | 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 |
+--------------------------------+-------------+
All implementations MUST support SPKI. The next section outlines the Next sections outline the use of HITs in X.509.v3 and in SPKI
use of HITs in SPKI. The SPKI and its formats are defined in certificates. X.509.v3 certificates are defined in [RFC3280]. The
[RFC2693]. X.509.v3 certificates are defined in [RFC3280]. Wire Wire format for X.509.v3 is Distinguished Encoding Rules format as
format for X.509.v3 is Distinguished Encoding Rules format as defined defined in [X.690]. The SPKI and its formats are defined in
in [X.690]. [RFC2693].
Hash and URL encodings (3 and 4) are used as defined in [RFC4306]. Hash and URL encodings (3 to 6) are used as defined in [RFC4306].
Using hash and URL encodings results in smaller HIP control packets, Using hash and URL encodings results in smaller HIP control packets,
but requires the receiver to resolve the URL or check local cache but requires the receiver to resolve the URL or check local cache
against the hash. against the hash.
It is not recommended to use hash and URL encodings when HIP-aware LDAP URL encoding (7 and 8) is used as defined in [RFC2255]. Using
middleboxes are present on the communication path between peers LDAP URL encoding results in smaller HIP control packets, but
because fetching remote certificates require the middlebox to buffer requires the receiver to retrieve the certificate or check local
the packets and to request remote data. This makes these devices cache against the URL.
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. 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.
4. X.509.v3 Certificate Object and Host Identities 3. X.509.v3 Certificate Object and Host Identities
When using X.509.v3 certificates to transmit information related to HITs need to be enclosed within the certificates, when using X.509.v3
HIP hosts, HITs need to be enclosed within the certificates. HITs certificates to transmit information related to HIP hosts. HITs can
are represented as issuer and subject alternative name X.509.v3 represent an issuer, a subject, or both. In X.509.v3 HITs are
extensions as defined in [RFC2459]. Because the Distinguished Name represented as issuer and subject alternative name extensions as
(DN) in X.509.v3 certificate cannot be empty HITs are also placed defined in [RFC2459]. If only HIP information is presented as either
into the Common Name (CN) in a colon delimited presentation format. the issuer or the subject the HIT is also placed into the respective
Placing CN is not necessary if DN contains any other information. It entity's DNs Common Name (CN) section in a colon delimited
is RECOMMENDED to use FQDN/NAI from the hosts HOST_ID parameter in DN presentation format. Inclusion of CN is not necessary if DN contains
if one exists. any other information. It is RECOMMENDED to use FQDN/NAI from the
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 the HIT of a host is expressed as follows: As an example, in a case where the issuer and the subject are both
HIP enabled, the HITs are expressed as follows:
Format: Format:
Issuer: CN=hit-of-host Issuer: CN=hit-of-host
Subject: CN=hit-of-host Subject: CN=hit-of-host
X509v3 extensions: X509v3 extensions:
X509v3 Issuer Alternative Name: X509v3 Issuer Alternative Name:
IP Address:HIT-OF-HOST IP Address:HIT-OF-HOST
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
IP Address:HIT-OF-HOST IP Address:HIT-OF-HOST
skipping to change at page 5, line 42 skipping to change at page 5, line 33
X509v3 extensions: X509v3 extensions:
X509v3 Issuer Alternative Name: X509v3 Issuer Alternative Name:
IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056 IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056 IP Address:2001:14:6CF:FAE7:BB79:BF78:7D64:C056
Appendix B shows a full example X.509.v3 certificate with HIP Appendix B shows a full example X.509.v3 certificate with HIP
content. 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)
Appendix A shows a full example SPKI certificate with HIP content.
5. Revocation of Certificates 5. Revocation of Certificates
Revocation of SPKI certificates is handled as defined in Section 5. Revocation of SPKI certificates is handled as defined in Section 5.
in [RFC2693] Revocation of X.509.v3 certificates is handled as in [RFC2693] Revocation of X.509.v3 certificates is handled as
defined in Section 5 in [RFC2459]. defined in Section 5 in [RFC2459].
6. IANA Considerations 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 This document defines the CERT parameter for the Host Identity
Protocol [RFC5201]. This parameter is defined in Section 2 with type Protocol [RFC5201]. This parameter is defined in Section 2 with type
768. The parameter type number is also defined in [RFC5201]. The 768. The parameter type number is also defined in [RFC5201]. The
Cert Group and Cert ID namespaces are managed locally by each peer Cert Group and Cert ID namespaces are managed locally by each host
that sends CERT parameters in HIP packets. that sends CERT parameters in HIP control packets.
7. Security Considerations 8. Security Considerations
Certificate grouping allows the certificates to be sent in multiple Certificate grouping allows the certificates to be sent in multiple
consecutive packets. This might allow similar attacks as IP-layer consecutive packets. This might allow similar attacks as IP-layer
fragmentation allows, i.e. sending of fragments in wrong order and fragmentation allows, i.e. sending of fragments in wrong order and
skipping some fragments to delay or stall packet processing by the skipping some fragments to delay or stall packet processing by the
victim in order to use resources (e.g. CPU or memory). victim in order to use resources (e.g. CPU or memory).
8. Acknowledgements 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.
9. Acknowledgements
The authors would like to thank M. Komu and T. Henderson of fruitful The authors would like to thank M. Komu and T. Henderson of fruitful
conversations on the subject. conversations on the subject.
9. References 10. References
9.1. Normative References 10.1. Normative References
[HIP.middle_auth] [HIP.service]
Heer, T., "End-Host Authentication for HIP Middleboxes", Heer, T., Wirtz, H., and S. Varjonen, "Service Identifiers
<draft-heer-hip-middle-auth-00.txt>. 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 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. 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 [RFC2459] Housley, R., Ford, W., Polk, T., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and CRL X.509 Public Key Infrastructure Certificate and CRL
Profile", RFC 2459, January 1999. Profile", RFC 2459, January 1999.
[RFC2693] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas, [RFC2693] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas,
B., and T. Ylonen, "SPKI Certificate Theory", RFC 2693, B., and T. Ylonen, "SPKI Certificate Theory", RFC 2693,
September 1999. September 1999.
[RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280, Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002. April 2002.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005. RFC 4306, December 2005.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson, [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
"Host Identity Protocol", RFC 5201, April 2008. "Host Identity Protocol", RFC 5201, April 2008.
9.2. Informative References 10.2. Informative References
[X.690] ITU-T, "Recommendation X.690 Information Technology - [X.690] ITU-T, "Recommendation X.690 Information Technology -
ASN.1 encoding rules: Specification of Basic Encoding ASN.1 encoding rules: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules (CER) and Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", July 2002, <http:// Distinguished Encoding Rules (DER)", July 2002, <http://
www.itu.int/ITU-T/studygroups/com17/languages/ www.itu.int/ITU-T/studygroups/com17/languages/
X.690-0207.pdf>. X.690-0207.pdf>.
Appendix A. SPKI certificate example Appendix A. SPKI certificate example
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