Secure Inter-Domain Routing (SIDR)                             G. Huston
Internet-Draft                                             G. Michaelson                          T. Manderson

Intended status: Standards Track                                   APNIC
Expires: May 2, November 26, 2009                                        T. Manderson
                                                        October 29, 2008

             A Profile for Bogon Origin Attestations (BOAs)

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   This document defines a standard profile for Bogon Origin
   Attestations (BOAs).  A BOA is a digitally signed object that
   provides a means of verifying that an IP address block holder has not
   authorised any Autonomous System (AS) to originate routes that are
   equivalent to any of the addresses listed in the BOA.  A BOA also
   provides a means of verifying that a BGP speaker is not using an AS
   without appropriate authority to use that AS. authority.  The proposed application of BOAs is
   intended to fit within the requirements for adding security measures
   to inter-domain routing, including the ability to support incremental
   and piecemeal deployment of such measures, and does not require any
   changes to the specification of the Border Gateway Protocol.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Basic Format . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Signed-Data Content Type . . . . . . . . . . . . . . . . .  4
       2.1.1.  version  . . . . . . . . . . . . . . . . . . . . . . .  4
       2.1.2.  digestAlgorithms . . . . . . . . . . . . . . . . . . .  4
       2.1.3.  encapContentInfo . . . . . . . . . . . . . . . . . . .  4
       2.1.4.  certificates . . . . . . . . . . . . . . . . . . . . .  6
       2.1.5.  crls . . . . . . . . . . . . . . . . . . . . . . . . .  6
       2.1.6.  signerInfo . . . . . . . . . . . . . . . . . . . . . .  6
   3.  BOA Validation . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  BOA Use Practices  . . . . . . . . . . . . . . . . . . . . . . 11
   5.  BOA Interpretation . . . . . . . . . . . . . . . . . . . . . . 12 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13 12
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . .
   Author's Address . . . . . . . . . . . . . . . 14
   Intellectual Property and Copyright Statements . . . . . . . . . . 15 14

1.  Introduction

   This document defines an application of the Resource Public Key
   Infrastructure (RPKI) to validate the attestations of resource
   holders and Internet Registries that certain addresses are currently
   neither allocated nor
   assigned to any party, nor in use by any party, and any
   appearance of such addresses or AS's in a routing advertisement in
   the Border Gateway Protocol (BGP) [RFC4271] should be considered an
   invalid use of such addresses or
   AS's. Autonomous System Numbers.

   The RPKI is based on Resource Certificates.  Resource Certificates
   are X.509 certificates that conform to the PKIX profile [RFC5280],
   and to the extensions for IP addresses and AS identifiers [RFC3779].
   A Resource Certificate describes an action by an Issuer that binds a
   list of IP address blocks and Autonomous System (AS) numbers to the
   Subject of a certificate, identified by the unique association of the
   Subject's private key with the public key contained in the Resource
   Certificate.  The RPKI is structured such that each current Resource
   Certificate matches a current resource allocation or assignment.
   This is described in [ID.sidr-arch]. [I-D.ietf-sidr-arch].

   BOAs can be regarded as a logical opposite of a Route Origin
   Authorization (ROA) [ID.sidr-roa-format], [I-D.ietf-sidr-roa-format], however are not
   contradictory to a ROA and allows a resource holder to explicitly
   list those IP addresses and AS's that are denoted by the holder as
   not validly appearing in any routing advertisement, and to make this
   attestation in a manner that a relying party can unambiguously
   validate under the framework of the RPKI.

   A BOA 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.

2.  Basic Format

   Using CMS syntax, a BOA 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

2.1.  Signed-Data Content Type

   According to the CMS specification, 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

2.1.1.  version

   The version is the syntax version number.  It MUST be 3,
   corresponding to the signerInfo structure having version number 3.

2.1.2.  digestAlgorithms

   The digestAlgorithms set MUST include only SHA-256, the OID for which
   is 2.16.840.  [RFC4055].  It MUST NOT contain any other

2.1.3.  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  eContentType

   The ContentType for a BOA is defined as id-ct-rpkiBOA, and has the
   numerical value of 1.2.840.113549.[TBD].  [This value needs
   to be assigned via an OID registration.]
         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-rpkiBOA OBJECT IDENTIFIER ::= { id-ct [TBD] }  eContent

   The content of a BOA identifies a list of one or more AS's and one or
   more IP address prefixes that are asserted to be "bogons" and,
   accordingly, BOAs are intended to act as a constraint on the routing
   system to signal that no route object that that relates to these AS's
   or IP addresses should be interpreted as representing a valid routing
   attestation.  A BOA is formally defined as:

         id-ct-rpkiBOA ::= {
            version [0] INTEGER DEFAULT 0,
            asIDs        SEQUENCE OF asIdsOrRange,
            ipAddrBlocks SEQUENCE OF BOAIPAddressFamily }

         ASIdOrRange   ::= CHOICE {
            id               ASId,
            range            ASRange }

         ASRange       ::= SEQUENCE {
            min              ASId,
            max              ASId }

         ASId          ::= INTEGER

         BOAIPAddressFamily ::= SEQUENCE {
            addressFamily OCTET STRING (SIZE (2..3)),
            addresses SEQUENCE OF IPAddress }

         IPAddress ::= BIT STRING  version

   The version number of the BogonOriginAttestation MUST be 0.  asIDs

   The asIDs field contains the AS numbers that are to be regarded as
   Bogon AS's.  The set of AS numbers may be explicitly listed, or
   specified as a continuous range of values.  The field is to be
   formatted as per the canonical format specified in [RFC3779].  BOAIPAddressFamily

   The BOAIPAddressFamily field encodes the set of IP address prefixes
   that are to be regarded as Bogon IP addresses that are to be
   constrained from appearing in any routing advertisement.  The
   intended semantics of an address prefix in a BOA is that any route
   object that has the same address prefix as that listed as a Bogon IP
   address, or is a more specific prefix of a Bogon IP address can be
   regarded as a Bogon route object.

   The syntax of the address prefixes listed in a BOA uses a subset of
   the IP Address Delegation extension defined in [RFC3779].  The
   BOAIPAddressFamily cannot contain arbitrary address ranges, but in
   all other respects uses the same canonical format as the IP Address
   Delegation Extension.

   Within the BOAIPAddressFamily structure, addressFamily contains the
   Address Family Identifier (AFI) of an IP address family.  This
   specification only supports IPv4 and IPv6.  Therefore, addressFamily
   MUST be either 0001 or 0002.  The addresses field represents prefixes
   as a sequence of type IPAddress, as defined in[RFC3779].

2.1.4.  certificates

   The certificates field MUST be included, and MUST contain only the
   end entity (EE) certificate needed to validate this BOA.

2.1.5.  crls

   The crls field MUST be omitted.

2.1.6.  signerInfo

   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 }  version

   The version number MUST be 3, corresponding with the choice of
   SubjectKeyIdentifier for the sid.  sid

   The sid is defined as:

         SignerIdentifier ::= CHOICE {
           issuerAndSerialNumber IssuerAndSerialNumber,
           subjectKeyIdentifier [0] SubjectKeyIdentifier }

   For a BOA, the sid MUST be a SubjectKeyIdentifier.  digestAlgorithm

   The digestAlgorithm MUST be SHA-256, the OID for which is
   2.16.840.  [RFC4055]  signedAttrs

   Signed Attributes are 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 BOA the attrValues must consist of only a single
   AttributeValue.  Content-Type 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 ROA MUST be
   1.2.840.113549.[TBD] (matching the eContentType in the
   EncapsulatedContentInfo).  Message-Digest 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].  Signing-Time Attribute

   The SigningTime Attribute MAY be present in a BOA.  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 BOA
   (as specified in Section 3).  The attrType OID for the SigningTime
   attribute is 1.2.840.113549.1.9.5.

   The SigningTime attribute is defined as:

         id-signingTime OBJECT IDENTIFIER ::= { iso(1) member-body(2)
             us(840) rsadsi(113549) pkcs(1) pkcs9(9) 5 }

         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.  BinarySigningTime Attribute

   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
   ROA (as specified in Section 3).  The attrType OID for the
   BinarySigningTime attribute is 1.2.840.113549.

   The BinarySigningTime attribute is defined as:

         id-aa-binarySigningTime OBJECT IDENTIFIER ::= { iso(1)
             member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
             smime(16) aa(2) 46 }

         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.  signatureAlgorithm

   The signatureAlgorithm MUST be RSA (rsaEncryption), the OID for which
   is 1.2.840.113549.1.1.1.  signature

   The signature value is defined as:

         SignatureValue ::= OCTET STRING

   The signature characteristics are defined by the digest and signature
   algorithms.  unsignedAttrs

   unsignedAttrs MUST be omitted.

3.  BOA Validation

   Before a relying party can use a BOA as a constrictor of a routing
   announcement, the relying party must use the RPKI to validate the
   BOA.  To do this the relying party performs the following steps:

   1.  Verify that the BOA syntax complies with this specification.  In
       particular, verify the following:

       a.  The contentType of the CMS object is SignedData (OID
       b.  The eContentType of the CMS object is id-ct-rpkiBOA (OID

       c.  The version of the SignedData object is 3.

       d.  The digestAlgorithm in the SignedData object is SHA-256 (OID

       e.  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.

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

       g.  The eContentType in the EncapsulatedContentInfo is rid-ct-
           rpkiBOA (OID 1.2.840.113549.[TBD])

       h.  The version of the BOA is 0.

       i.  The addressFamily in the BOAIPAddressFamily is either IPv4 or
           IPv6 (0001 and 0002, respectively).

       j.  The version of the SignerInfo is 3.

       k.  The digestAlgorithm in the SignerInfo object is SHA-256 (OID

       l.  The signatureAlgorithm in the SignerInfo object is RSA (OID

       m.  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). .

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

   2.  Use the public key in the EE certificate to verify the signature
       on the BOA.

   3.  Verify that the EE certificate has an IP Address Delegation
       extension [RFC3779] and that the IP address prefixes in that
       extension exactly match cover the IP address prefixes in the BOA, and the AS
       numbers in that extension exactly match cover the AS numbers in the BOA.

   4.  Verify that no valid ROA exists which also covers any more or
       less specific prefixes, or any AS numbers.  In the case that a
       ROA does exist which overlaps the BOA in any way, the BOA MUST be
       considered invalid.
   5.  Verify that the EE certificate is a valid end-entity certificate
       in the resource PKI by constructing a valid certificate path to a
       trust anchor.  (See [ID.sidr-res-certs] [I-D.ietf-sidr-res-certs] for more details.)

   Note that requiring an exact match between the IP address prefixes
   and AS's in a BOA and the IP address prefixes and AS's in the
   corresponding EE certificate does not place any limitations on BOA
   use.  Since each EE certificate in the RPKI architecture is used to
   verify only a single BOA, it is natural to have the IP address
   prefixes in the certificate match those in the corresponding BOA.

4.  BOA Use Practices

   BOAs are intended to allow relying parties a means of validating
   whether route origination information as described in a route
   advertisement refers to an IP address or AS number that has not been
   validly allocated for use in the routing system.

   Any party with a validly assigned Internet resource set and a CA
   certificate that describes this delegation allocation can publish a BOA,
   independently of the actions of the actions of the party that
   assigned the resource set.

   BOAs are not hierarchically related.

   An Internet Registry SHOULD maintain a single BOA in relation to each
   parent registry that has assigned resources to this registry.

   BOAs are not hierarchically related however they are subordinate to
   the CA certificate that describes the immediate allocations assigned.

   An Internet Registry SHOULD maintain a regular issuance cycle for

   For registries that operate on a day-to-day basis in terms of
   resource transactions, it is suggested that a local BOA management
   practice would be that a new BOA should be issued on a regular 24
   hour basis.  The corresponding EE certificate should have a validity
   period of no more than 72 hours from the time of issuance.  Each time
   a new EE certificate for a BOA is issued the previous BOA's EE
   certificate should be revoked and the previous BOA removed from the
   publication repository.

   Parties that operate a local cache of RPKI objects should ensure that
   they refresh BOA objects at intervals 24 hours to ensure that they
   have the current BOA in the local cache.

5.  BOA Interpretation

   A BOA can be used to check an inter-domain routing advertisement
   ("route object")
   ("route") to determine if the origination information in the route
   object refers to invalid IP addresses or an invalid AS number.

   If a route object has an AS origination that refers to an AS number that is
   listed in a valid BOA, then the route object can be regarded as a Bogon object, Bogon, and
   local policies that apply to Bogon AS's can be applied to the object.  This holds whether or not the address prefix
   of route.
   However if the AS number of this route object is described by in a valid ROA or not.
   whose EE certificate lists the AS number, the BOA MUST be considered

   If a route object has an address prefix that is equal to, or is a more
   specific prefix of an IP address that is included in a valid BOA then
   the route object can be regarded as a Bogon object, Bogon, and local policies that apply
   to Bogon AS's prefixes can be applied to the object,
   unless route.  However if the
   address prefix and AS origination of the route object is
   also described (either more or less
   specific) by a valid ROA, in which case the BOA is to MUST be
   disregarded.  In other words, a valid ROA SHOULD infer a higher local
   trust preference than a BOA if a valid ROA and a valid BOA both exist
   that refer to the same address prefix. considered invalid.

   BOA interpretation in the context of validation of origination of
   route objects is described in [ID.sidr-roa-validation]. [I-D.ietf-sidr-roa-validation].

6.  Security Considerations

   There is no assumption of confidentiality for the data in a BOA; it
   is anticipated that BOAs 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 BOA, since the RPKI used
   for BOA validation provides authorization but not authentication.
   Although the BOA is a signed, application layer object, there is no
   intent to convey non-repudiation via a BOA.

   The purpose of a BOA is to convey an attestation by an address holder
   that there is no authority for the generation of a route object that refers
   to specified addresses or origination from specified AS's.  The
   integrity of a BOA must be established in order to validate the
   authority of the Bogon Attestation.  The BOA makes use of the CMS
   signed message format for integrity, and thus inherits the security
   considerations associated with that data structure.  The right of the
   BOA signer to authorize the attestation of specified IP addresses and
   AS's as Bogons is established through use of the address space and AS
   number PKI described in [ID.sidr-arch]. [I-D.ietf-sidr-arch].  Specifically, a
   relying party must verify the signature on the BOA using an X.509
   certificate issued under this PKI, and check that the prefix(es) in
   the BOA match match, or are covered by those in the address space extension
   in the certificate.

7.  IANA Considerations


   It would be anticipated that the IANA maintain a BOA for all
   unallocated space or reserved space (IPv4, IPv6 and ASNs) not
   intended for public use.

8.  Acknowledgments

   The authors are indebted to the authors of Route Origin Authorization
   (ROA) [ID.sidr-roa-format], [I-D.ietf-sidr-roa-format], M. Lepinski, S. Kent and D. Kong,
   as much of the text used to define a BOA has been borrowed from the
   ROA format specification, and Russ Housley for clarification on the
   CMS profile.

   Further the authors wish to thank many security people, too many to
   name, for clarifying that negative attestations are a valid and
   useful security construct.

   Lastly, without the orginal thoughts and words from George Michaelson
   and Geoff Huston this document would not exist.  Their hands helped
   form the concepts of why we need BOAs in the RPKI and historically
   were two of the original three authors of this document.

9.  Normative References


              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch draft-ietf-sidr-arch-06 (work in
              progress), February 2008.

   [ID.sidr-res-certs] March 2009.

              Huston, G., Michaleson, Michaelson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates", Internet
              Draft draft-ietf-sidr-res-certs, August 2008.

              draft-ietf-sidr-res-certs-16 (work in progress),
              February 2009.

              Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to
              Support Secure Internet Routing",
              draft-ietf-sidr-roa-format "A Profile for Route
              Origin Authorizations (ROAs)",
              draft-ietf-sidr-roa-format-04 (work in progress), July
              November 2008.


              Huston, G. and G. Michaelson, "Validation of Route
              Origination in BGP using the Resource Certificate PKI",
              draft-ietf-sidr-roa-validation-01 (work in progress),
              October 2008.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.

   [RFC3852]  Housley, R., "Cryptographic Message Syntax (CMS)",
              RFC 3852, July 2004.

   [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.

   [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.

Authors' Addresses

   Geoff Huston
   Asia Pacific Network Information Centre


   George Michaelson
   Asia Pacific Network Information Centre


Author's Address

   Terry Manderson


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