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Individual Submission                                          G. Huston
Internet-Draft                                             G. Michaelson
Intended status: BCP                                               APNIC
Expires: November 9, 2010                                    May 8, 2010


             A Profile for AS Adjacency Attestation Objects
                  draft-huston-sidr-aao-profile-03.txt

Abstract

   This document describes a profile for AS Adjacency Attestation
   Objects (AAOs).  An AAO is a digitally signed object that provides a
   means of verifying that an AS holder 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 is prepared to announce or
   receive routes with these adjacent AS's in the inter-domain domain
   environment.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on November 9, 2010.

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



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Semantic Interpretation of an AAO  . . . . . . . . . . . . . .  3
   3.  Basic Format . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Signed-Data Content Type . . . . . . . . . . . . . . . . .  5
       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

























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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 security framework, a
   mechanism is defined here to allow entities to verify that an AS
   holder attests that is adjacent to one or more other AS's, with the
   inference that it is prepared to announce routes to these adjacent
   AS's in the inter-domain routing environment.  An AS Adjacency
   Attestation Object (AAO) provides this function.

   An AAO is a digitally signed object that makes use of Cryptographic
   Message Syntax (CMS) [RFC5652] as a standard encapsulation format.
   CMS was chosen to take advantage of existing open source software
   available for processing messages in this format.

   The AAO is an attestation, made and issued by the local AS holder,
   that the local AS is an inter-domain routing peer with each of the
   AS's that are enumerated in an associated AS list contained in the
   AAO.  An AAO is a two part structure, containing the local AS and a
   list of adjacent AS's.  The AAO is signed by a an End Entity (EE)
   Resource Certificate that has the local AS as the value of its
   [RFC3779] 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], 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.  Semantic Interpretation of an AAO

   An AAO is an attestation on the part of a AS holder that it supports
   currently active 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 have been
   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.




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   The AAO is intended to provide "closure" with respect to
   interpretation of the AAO by relying parties, to the extent that if a
   valid AAO exists for a local AS, then from the perspective of that
   local AS all adjacencies with those AS's listed in the valid AAO can
   be regarded as "valid" and any other adjacency from the perspective
   of the local AS can be regarded as potentially "invalid".  In other
   words an AAO is an attestation of adjacency with the AS's listed in
   the AAO and an implicit attestation of the denial of adjacency with
   all other AS's.

   Where an AS holder has published two or more valid AAO's, the set of
   "valid" adjacent AS's refers to the union of the lists of adjacent
   AS's and all other AS's can be regarded as "invalid" from the
   perspective of the local AS.

   A relying party may infer from a valid AAO that the signing AS holder
   may have the intent to advertise route objects across this inter-AS
   routing adjacency, and may be prepared to learn route objects that
   are passed to it from the adjacent AS.  The AAO does not described
   which routes may be announced across a corresponding inter-AS routing
   adjacency.

   It is noted that an AAO is an asymmetric assertion, where one AS is
   asserting that an inter-domain routing adjacency with another AS
   exists.  It should also be noted that this assertion is not
   explicitly acknowledged by the remote AS in the context of a single
   issued 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 combined
   assertion of adjacency where both AS's sign a single attestation of
   the existence of an inter-domain routing adjacency between these
   AS's.  Such a combined 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:







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         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.  [RFC5652]

3.1.  Signed-Data Content Type

   According to the CMS standard, the signed-data content type shall
   have ASN.1 type SignedData:

         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 contains the OIDs of the digest algorithm(s)
   used in signing the encapsulated content.  This set MUST conform to
   the RPKI Algorithms and Key Size Profile specification
   [ID.sidr-rpki-algs].

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



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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 }

3.1.3.2.  eContent

   The content of an AAO identifies one or more AS's that the signing AS
   holder is attesting the existence of a routing adjacency.

   The AAO contains no routing policy qualifications, nor does it
   reference any address prefixes that may be announced or received
   within the context of any routing adjacency.

   An AAO is 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



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   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).

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 [RFC5652]

3.1.5.  certificates

   The certificates element MUST be included and MUST contain only the
   single EE 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:





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         SignerInfo ::= SEQUENCE {
           version CMSVersion,
           sid SignerIdentifier,
           digestAlgorithm DigestAlgorithmIdentifier,
           signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL,
           signatureAlgorithm SignatureAlgorithmIdentifier,
           signature SignatureValue,
           unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL }

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 consist of the OID of a digest algorithm
   that conforms to the RPKI Algorithms and Key Size Profile
   specification [ID.sidr-rpki-algs].

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 signed 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 by the signer MAY also be included.  The
   intent is to allow additional signed attributes to be included if a



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   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

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 [RFC5652].

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.






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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:

         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 consist of the OID of a signature
   algorithm that conforms RPKI Algorithms and Key Size Profile
   specification [ID.sidr-rpki-algs].

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:







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       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 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.

       d.  The crls field in the SignedData object is omitted.

       e.  The eContentType in the EncapsulatedContentInfo is id-ct-
           ADAdjacencyAttest (OID 1.2.840.113549.1.9.16.1.32)

       f.  The version of the id-ct-ASAdjacencyAttest is 0.

       g.  The version of the SignerInfo is 3.

       h.  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).

       i.  The unsignedAttrs field in the SignerInfo object is omitted.

       j.  The digestAlgorithm in the SignedData and SignerInfo objects
           as well as the signatureAlgorithm in the SignerInfo object
           conform to the RPKI Algorithms and Key Size Profile
           specification [ID.sidr-rpki-algs].

   2.  The public key in the EE certificate (contained within the AAO)
       can be used to successfully verify the signature on the AAO.

   3.  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.  The EE certificate is a valid end-entity certificate in the
       Resource PKI as specified by [ID.ietf-sidr-res-certs]. (in
       particular, there exists a valid certification path from a trust
       anchor to the EE certificate.)


5.  Security Considerations

   There is no assumption of confidentiality for the data in a AAO; it
   is anticipated that AAOs will be stored in public repositories that



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   are accessible to all ISPs, and potentially 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 routing
   capability that an AS has the capability to announce route objects
   via a routing adjacency with another AS and has the capability 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 a routing 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 have issued current 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), March 2009.



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   [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, February 2009.

   [ID.sidr-rpki-algs]
              Huston, G., "A Profile for Algorithms and Key Sizes for
              use in the Resource Public Key Infrastructure", Work in
              progress: Internet
              Drafts draft-ietf-sidr-rpki-algs-00.txt, August 2009.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 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.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)",
              RFC 5652, September 2009.

8.2.  Informative References

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 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











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