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 This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, except to format it for publication as an RFC or to translate it into languages other than English. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Heer & Varjonen Expires March 27, 2011 [Page 1] Internet-Draft HIP CERT September 2010 The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 27, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. 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 Heer & Varjonen Expires March 27, 2011 [Page 2] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 3] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 4] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 5] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 6] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 7] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 8] Internet-Draft HIP CERT September 2010 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, . Heer & Varjonen Expires March 27, 2011 [Page 9] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 10] Internet-Draft HIP CERT September 2010 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. Heer & Varjonen Expires March 27, 2011 [Page 11] Internet-Draft HIP CERT September 2010 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 Heer & Varjonen Expires March 27, 2011 [Page 12] Internet-Draft HIP CERT September 2010 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 Heer & Varjonen Expires March 27, 2011 [Page 13]