SIDR G. Huston Internet-Draft G. Michaelson Intended status: Standards Track APNIC Expires: April 2, 2009 September 29, 2008 A Profile for AS Adjacency Attestation Objects draft-huston-sidr-aao-profile-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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." 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 April 2, 2009. Abstract This document defines a standard profile for AS Adjacency Attestation Objects (AAOs). An AAO is a digitally signed object that provides a means of verifying that an AS has made an attestation that it has a inter-domain routing adjacency with one or more other AS's, with the associated inference that this AS may announce or receive routes with these adjacent AS's. Huston & Michaelson Expires April 2, 2009 [Page 1] Internet-Draft AS Adjacency Profile September 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Intepretation of an AAO . . . . . . . . . . . . . . . . . . . 3 3. Basic Format . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Signed-Data Content Type . . . . . . . . . . . . . . . . . 4 3.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 5 3.1.2. digestAlgorithms . . . . . . . . . . . . . . . . . . . 5 3.1.3. encapContentInfo . . . . . . . . . . . . . . . . . . . 5 3.1.4. CertificateSet . . . . . . . . . . . . . . . . . . . . 7 3.1.5. certificates . . . . . . . . . . . . . . . . . . . . . 7 3.1.6. crls . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.7. signerInfos . . . . . . . . . . . . . . . . . . . . . 7 4. AAO Validation . . . . . . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Huston & Michaelson Expires April 2, 2009 [Page 2] Internet-Draft AS Adjacency Profile September 2008 1. Introduction The primary purpose of the Internet IP Address and AS Number Resource Public Key Infrastructure (RPKI) system [ID.ietf-sidr-arch] is to improve routing security. As part of this system, a mechanism is defined here to allow entities to verify that an AS attests that is adjacent to one or more other AS's, with the inference that it may elect to announce routes to these adjacent AS's. An AAO provides this function. An AAO is a digitally signed object that makes use of Cryptographic Message Syntax (CMS) [RFC3852] as a standard encapsulation format. CMS was chosen to take advantage of existing open source software available for processing messages in this format. An AAO is a two part structure, that contains a list of AS's and a single "local' AS. The AAO is an attestation that the local AS is a routing peer to each of the AS's in the list. The AAO is signed by a an EE Resource Certificate that has the local AS as the value of its AS number resource extension. 1.1. Terminology It is assumed that the reader is familiar with the terms and concepts described in "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile" [RFC5280], "X.509 Extensions for IP Addresses and AS Identifiers" [RFC3779], "Internet Protocol" [RFC0791], "Internet Protocol Version 6 (IPv6) Addressing Architecture" [RFC4291], "Internet Registry IP Allocation Guidelines" [RFC2050], and related regional Internet registry address management policy documents, and BGP-4 [RFC4271] 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. 2. Intepretation of an AAO An AAO is an attestation on the part of a AS holder that it supports inter-domain routing adjacencies to each of the AS's listed in the AAO. The AAO does not list any prefixes that may be announced to the adjacent AS's either directly or indirectly. The AAO also does not list any local routing policies that may be applied to the routes that are advertised across this adjacency, nor any routing policies that may be applied to routes that are learned from this adjacency. The AAO does not refer to any individual BGP peer session, and may refer to one of many eBGP sessions between the same pair of AS's. Huston & Michaelson Expires April 2, 2009 [Page 3] Internet-Draft AS Adjacency Profile September 2008 It is reasonable for a relying party to infer from a valid AAO that the signing AS has the intent to advertise route objects across this adjacency, and is prepared to learn route objects that are passed to it from the adjacent AS. It is noted that an AAO is an asymmetric assertion, where one AS is asserting that an inter-domain routing adjacency with another AS is asserted to exist, but this assertion is not explicitly acknowledged by the remote AS in the context of a single AAO. Relying parties may elect to place greater levels of confidence in the existence of an inter-domain routing adjacency when both AS's have signed and published AAO objects that contain mutual references. It is also noted that there is a subtle distinction that could be drawn here between the appropriate semantic interpretation a pair of unilateral assertions of adjacency using two AAOs and a bilateral assertion of adjacency where both AS's sign a single assertion of the existence of an inter-domain routing adjacency between these AS's. This bilateral approach, using a single assertion with two digital signatures, is not defined in this document. 3. Basic Format Using CMS syntax, an AAO is a type of signed-data object. The general format of a CMS object is: ContentInfo ::= SEQUENCE { contentType ContentType, content [0] EXPLICIT ANY DEFINED BY contentType } ContentType ::= OBJECT IDENTIFIER As a AAO is a signed-data object, it uses the corresponding OID, 1.2.840.113549.1.7.2. [RFC3852] 3.1. Signed-Data Content Type According to the CMS standard, the signed-data content type shall have ASN.1 type SignedData: Huston & Michaelson Expires April 2, 2009 [Page 4] Internet-Draft AS Adjacency Profile September 2008 SignedData ::= SEQUENCE { version CMSVersion, digestAlgorithms DigestAlgorithmIdentifiers, encapContentInfo EncapsulatedContentInfo, certificates [0] IMPLICIT CertificateSet OPTIONAL, crls [1] IMPLICIT RevocationInfoChoices OPTIONAL, signerInfos SignerInfos } DigestAlgorithmIdentifiers ::= SET OF DigestAlgorithmIdentifier SignerInfos ::= SET OF SignerInfo 3.1.1. version The version is the syntax version number. It MUST be 3, corresponding to the signerInfo structure having version number 3. 3.1.2. digestAlgorithms The digestAlgorithms set MUST include only SHA-256, the OID for which is 2.16.840.1.101.3.4.2.1. [RFC4055] It MUST NOT contain any other algorithms. 3.1.3. encapContentInfo encapContentInfo is the signed content, consisting of a content type identifier and the content itself. EncapsulatedContentInfo ::= SEQUENCE { eContentType ContentType, eContent [0] EXPLICIT OCTET STRING OPTIONAL } ContentType ::= OBJECT IDENTIFIER 3.1.3.1. eContentType The ContentType for a AAO is defined as id-ct-ASAdjancyAttest and has the numerical value of 1.2.840.113549.1.9.16.1.32. id-smime OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9) 16 } id-ct OBJECT IDENTIFIER ::= { id-smime 1 } id-ct-ASAdjacencyAttest OBJECT IDENTIFIER ::= { id-ct 32 } Huston & Michaelson Expires April 2, 2009 [Page 5] Internet-Draft AS Adjacency Profile September 2008 3.1.3.2. eContent The content of an AAO identifies one or more AS's that the signing AS is attesting that it has a routing adjacency with. Multiple adjacencies can be attested on one or more AAOs. The AAO contains no routing policy qualifications, nor does it reference any address prefixes that may be announced within the context of that routing adjacency. An AAO is formally defined as: id-ct-ASAdjacencyAttest ::= SEQUENCE { version [0] INTEGER DEFAULT 0, ASIdentifiers ::= SEQUENCE OF ASIdOrRange, localASNum ASId} ASIdOrRange ::= CHOICE { id ASId, range ASRange } ASRange ::= SEQUENCE { min ASId, max ASId } ASId ::= INTEGER 3.1.3.2.1. version The version number of the ASAdjacencyAttestation MUST be 0. 3.1.3.2.2. ASIdentifiers The ASIdentifiers element is a SEQUENCE containing AS numbers for which the localASnum AS is attesting the existence of a routing adjacency. Any pair of items in the asIdentifiers SEQUENCE MUST NOT overlap. Any contiguous series of AS identifiers MUST be combined into a single range whenever possible. The AS identifiers in the asIdentifiers element MUST be sorted by increasing numeric value. 3.1.3.2.2.1. ASIdOrRange The ASIdOrRange type is a CHOICE of either a single integer (ASId) or a single sequence (ASRange). Huston & Michaelson Expires April 2, 2009 [Page 6] Internet-Draft AS Adjacency Profile September 2008 3.1.3.2.2.2. ASRange The ASRange type is a SEQUENCE consisting of a min and a max element, and is used to specify a range of AS identifier values. 3.1.3.2.2.2.1. min and max The min and max elements have type ASId. The min element is used to specify the value of the minimum AS identifier in the range, and the max element specifies the value of the maximum AS identifier in the range. 3.1.3.2.2.3. ASId The ASId type is an INTEGER. 3.1.3.2.3. localASNum The localASNum field contains the AS that is making the attestation of routing adjacency to each of the AS's listed in the ASIdentifiers element. 3.1.4. CertificateSet The CertificateSet type is defined in section 10 of [RFC3852] 3.1.5. certificates The certificates element MUST be included and MUST contain only the single end entity resource certificate needed to validate this AAO. 3.1.6. crls The crls element MUST be omitted. 3.1.7. signerInfos SignerInfo is defined under CMS as: SignerInfo ::= SEQUENCE { version CMSVersion, sid SignerIdentifier, digestAlgorithm DigestAlgorithmIdentifier, signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL, signatureAlgorithm SignatureAlgorithmIdentifier, signature SignatureValue, unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL } Huston & Michaelson Expires April 2, 2009 [Page 7] Internet-Draft AS Adjacency Profile September 2008 3.1.7.1. version The version number MUST be 3, corresponding with the choice of SubjectKeyIdentifier for the sid. 3.1.7.2. sid The sid is defined as: SignerIdentifier ::= CHOICE { issuerAndSerialNumber IssuerAndSerialNumber, subjectKeyIdentifier [0] SubjectKeyIdentifier } For a AAO, the sid MUST be a SubjectKeyIdentifier. 3.1.7.3. digestAlgorithm The digestAlgorithm MUST be SHA-256, the OID for which is 2.16.840.1.101.3.4.2.1. [RFC4055] 3.1.7.4. signedAttrs The signedAttrs is defined as: SignedAttributes ::= SET SIZE (1..MAX) OF Attribute Attribute ::= SEQUENCE { attrType OBJECT IDENTIFIER, attrValues SET OF AttributeValue } AttributeValue ::= ANY The signedAttr element MUST be present and MUST include the content- type and message-digest attributes. The signer MAY also include the signing-time signed attribute, the binary-signing-time signed attribute, or both signed attributes. Other signed attributes that are deemed appropriate MAY also be included. The intent is to allow additional signed attributes to be included if a future need is identified. This does not cause an interoperability concern because unrecognized signed attributes are ignored by the relying party. The signedAttr MUST include only a single instance of any particular attribute. Additionally, even though the syntax allows for a SET OF AttributeValue, in a AAO the attrValues must consist of only a single AttributeValue Huston & Michaelson Expires April 2, 2009 [Page 8] Internet-Draft AS Adjacency Profile September 2008 3.1.7.4.1. ContentType Attribute The ContentType attribute MUST be present. The attrType OID for the ContentType attribute is 1.2.840.113549.1.9.3. The attrValues for the ContentType attribute in a AAO MUST be 1.2.840.113549.1.9.16.1.24 (matching the eContentType in the EncapsulatedContentInfo). 3.1.7.4.2. MessageDigest Attribute The MessageDigest attribute MUST be present. The attrType OID for the MessageDigest Attribute is 1.2.840.113549.1.9.4. The attrValues for the MessageDigest attribute contains the output of the digest algorithm applied to the content being signed, as specified in Section 11.1 of [RFC3852]. 3.1.7.4.3. SigningTime Attribute The SigningTime attribute MAY be present. If it is present it MUST be ignored by the relying party. The presence of absence of the SigningTime attribute in no way affects the validation of the AAO (as specified in Section 4). The attrType OID for the SigningTime attribute is 1.2.840.113549.1.9.5. The attrValues for the SigningTime attribute is defined as: SigningTime ::= Time Time ::= CHOICE { utcTime UTCTime, generalizedTime GeneralizedTime } The Time element specifies the time, based on the local system clock, at which the digital signature was applied to the content. 3.1.7.4.4. BinarySigningTimeAttribute The BinarySigningTime attribute MAY be present. If it is present it MUST be ignored by the relying party. The presence of absence of the BinarySigningTime attribute in no way affects the validation of the AAO (as specified in Section 3). The attrType OID for the SigningTime attribute is 1.2.840.113549.1.9.16.2.46. The attrValues for the SigningTime attribute is defined as: Huston & Michaelson Expires April 2, 2009 [Page 9] Internet-Draft AS Adjacency Profile September 2008 BinarySigningTime ::= BinaryTime BinaryTime ::= INTEGER (0..MAX) The BinaryTime element specifies the time, based on the local system clock, at which the digital signature was applied to the content. 3.1.7.5. signatureAlgorithm The signatureAlgorithm MUST be RSA (rsaEncryption), the OID for which is 1.2.840.113549.1.1.1. 3.1.7.6. signature The signature value is defined as: SignatureValue ::= OCTET STRING The signature characteristics are defined by the digest and signature algorithms. 3.1.7.7. unsignedAttrs unsignedAttrs MUST be omitted. 4. AAO Validation Before a relying party can use an AAO, the relying party must first use the RPKI to validate the AAO by performing the following steps. 1. Verify that the AAO syntax complies with this specification. In particular, verify the following: a. The contentType of the CMS object is SignedData (OID 1.2.840.113549.1.7.2). b. The version of the SignedData object is 3. c. The digestAlgorithm in the SignedData object is SHA-256 (OID 2.16.840.1.101.3.4.2.1). d. The certificates field in the SignedData object is present and contains an EE certificate whose Subject Key Identifier (SKI) matches the sid field of the SignerInfo object. Huston & Michaelson Expires April 2, 2009 [Page 10] Internet-Draft AS Adjacency Profile September 2008 e. The crls field in the SignedData object is omitted. f. The eContentType in the EncapsulatedContentInfo is id-ct- ADAdjacencyAttest (OID 1.2.840.113549.1.9.16.1.32) g. The version of the id-ct-ASAdjacencyAttest is 0. h. The version of the SignerInfo is 3. i. The digestAlgorithm in the SignerInfo object is SHA-256 (OID 2.16.840.1.101.3.4.2.1). j. The signatureAlgorithm in the SignerInfo object is RSA (OID 1.2.840.113549.1.1.1). k. The signedAttrs field in the SignerInfo object is present and contains both the ContentType attribute (OID 1.2.840.113549.1.9.3) and the MessageDigest attribute (OID 1.2.840.113549.1.9.4). l. The unsignedAttrs field in the SignerInfo object is omitted. 2. Use the public key in the EE certificate to verify the signature on the AAO. 3. Verify that the EE certificate has an Autonomous System Identifier Delegation Extension [RFC3779] and that the Autonomous System Identifier in that extension exactly matches the Autonomous System Identifier in the localASNum element of the AAO. 4. Verify that the EE certificate is a valid end-entity certificate in the RPKI by constructing a valid certificate path to a trust anchor. (See [ID.ietf-sidr-res-certs] for more details.) 5. Security Considerations There is no assumption of confidentiality for the data in a AAO; it is anticipated that AAOs will be stored in repositories that are accessible to all ISPs, and perhaps to all Internet users. There is no explicit authentication associated with a AAO, since the RPKI that is used for AAO validation provides authorization but not authentication. Although the AAO is a signed, application layer object, there is no intent to convey non-repudiation via a AAO. The purpose of a AAO is to convey a unilateral statement of intent that an AS has the intention to announce route objects via a routing Huston & Michaelson Expires April 2, 2009 [Page 11] Internet-Draft AS Adjacency Profile September 2008 adjacency with another AS and has the intention to listen for route objects that are passed to it over a routing adjacency. This should not be interpreted as an authority, nor is a relying party justified in assuming that such an adjacency exists, nor that any valid routing announcements that are passed across this routing adjacency. A relying party may be able to place greater confidence in the inferred existence of a routing adjacency in the case where both AS holders mutually generate signed AAO objects that nominate each other as an adjacent AS. The AAO object does not convey any information relating to route policies that may be applied to the adjacency by either party to a route adjacency, nor what prefixes may be advertised across that adjacency, nor any attributes that may be associated with such advertisements. 6. IANA Considerations [Note to IANA, to be removed prior to publication: there are no IANA considerations stated in this version of the document.] 7. Acknowledgements The authors would like to acknowledge the work of Matt Lepinski, Stephen Kent and Derrick Kong, whose work on the Route Origin Attestation Profile was used as the starting point for this document. 8. References 8.1. Normative References [ID.ietf-sidr-arch] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", draft-ietf-sidr-arch (work in progress), February 2008. [ID.ietf-sidr-res-certs] Huston, G., Michaleson, G., and R. Loomans, "A Profile for X.509 PKIX Resource Certificates", Internet Draft draft-ietf-sidr-res-certs, August 2008. [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP Addresses and AS Identifiers", RFC 3779, June 2004. Huston & Michaelson Expires April 2, 2009 [Page 12] Internet-Draft AS Adjacency Profile September 2008 [RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3852, July 2004. [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008. 8.2. Informative References [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [RFC2050] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and J. Postel, "INTERNET REGISTRY IP ALLOCATION GUIDELINES", BCP 12, RFC 2050, November 1996. [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 4055, June 2005. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. Authors' Addresses Geoff Huston Email: gih@apnic.net URI: http://www.apnic.net George Michaelson Email: ggm@apnic.net URI: http://www.apnic.net Huston & Michaelson Expires April 2, 2009 [Page 13] Internet-Draft AS Adjacency Profile September 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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