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Secure Inter-Domain Routing (sidr)                          M. Lepinski
Internet Draft                                                  S. Kent
Expires: May 2009                                               D. Kong
Intended Status: Proposed Standard                     BBN Technologies
                                                       November 3, 2008

             A Profile for Route Origin Authorizations (ROAs)
                     draft-ietf-sidr-roa-format-04.txt


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Abstract

   This document defines a standard profile for Route Origin
   Authorizations (ROAs).  A ROA is a digitally signed object that
   provides a means of verifying that an IP address block holder has
   authorized an Autonomous System (AS) to originate routes to that one
   or more prefixes within the address block.

Table of Contents


   1. Introduction...................................................2
   2. Basic Format...................................................3



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      2.1. Signed-Data Content Type..................................3
         2.1.1. version..............................................4
         2.1.2. digestAlgorithms.....................................4
         2.1.3. encapContentInfo.....................................4
            2.1.3.1. eContentType....................................4
            2.1.3.2. eContent........................................4
               2.1.3.2.1. version....................................5
               2.1.3.2.2. asID.......................................5
               2.1.3.2.3. ipAddrBlocks...............................5
         2.1.4. certificates.........................................6
         2.1.5. crls.................................................6
         2.1.6. signerInfos..........................................6
            2.1.6.1. version.........................................6
            2.1.6.2. sid.............................................6
            2.1.6.3. digestAlgorithm.................................6
            2.1.6.4. signedAttrs.....................................7
               2.1.6.4.1. ContentType Attribute......................7
               2.1.6.4.2. MessageDigest Attribute....................7
               2.1.6.4.3. SigningTime Attribute......................8
               2.1.6.4.4. BinarySigningTimeAttribute.................8
            2.1.6.5. signatureAlgorithm..............................8
            2.1.6.6. signature.......................................9
            2.1.6.7. unsignedAttrs...................................9
   3. ROA Validation.................................................9
   4. Security Considerations.......................................10
   5. IANA Considerations...........................................11
   6. Acknowledgments...............................................11
   7. References....................................................12
      7.1. Normative References.....................................12
      7.2. Informative References...................................12
   Authors' Addresses...............................................13
   Intellectual Property Statement..................................14
   Disclaimer of Validity...........................................14
   Copyright Statement..............................................14

1. Introduction

   The primary purpose of the Internet IP Address and AS Number Resource
   Public Key Infrastructure (RPKI) system is to improve routing
   security.  As part of this system, a mechanism is needed to allow
   entities to verify that an AS has been given permission by an IP
   address block holder to advertise routes to one or more prefixes
   within that block.  A ROA provides this function.

   A ROA is a digitally signed object that makes use of Cryptographic
   Message Syntax (CMS) [RFC3852] as a standard encapsulation format.



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   CMS was chosen to take advantage of existing open source software
   available for processing messages in this format.

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] and "X.509
   Extensions for IP Addresses and AS Identifiers" [RFC3779].

   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].

2. Basic Format

   Using CMS syntax, a ROA 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 ROA is a signed-data object, it uses the corresponding OID,
   1.2.840.113549.1.7.2. [RFC3852]

2.1. 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





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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 2.16.840.1.101.3.4.2.1. [RFC4055] It MUST NOT contain any other
   algorithms.

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

2.1.3.1. eContentType

   The ContentType for a ROA is defined as routeOriginAttestation and
   has the numerical value of 1.2.840.113549.1.9.16.1.24.

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

      id-ct OBJECT INDENTIFIER ::= { id-smime 1 }

      routeOriginAttestion OBJECT IDENTIFIER ::= { id-ct 24 }

2.1.3.2. eContent

   The content of a ROA identifies a single AS that has been authorized
   by the address space holder to originate routes and a list of one or
   more IP address prefixes that will be advertised.  If the address
   space holder needs to authorize multiple ASes to advertise the same
   set of address prefixes, the holder issues multiple ROAs, one per AS
   number. A ROA is formally defined as:

      RouteOriginAttestation ::= SEQUENCE {
         version [0] INTEGER DEFAULT 0,
         asID  ASID,
         ipAddrBlocks SEQUENCE OF ROAIPAddressFamily }


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      ASID ::= INTEGER

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


      ROAIPAddress ::= SEQUENCE {
         address IPAddress,
         maxLength INTEGER OPTIONAL }

      IPAddress ::= BIT STRING

2.1.3.2.1. version

   The version number of the RouteOriginAttestation MUST be 0.

2.1.3.2.2. asID

   The asID field contains the AS number that is authorized to originate
   routes to the given IP address prefixes.

2.1.3.2.3. ipAddrBlocks

   The ipAddrBlocks field encodes the set of IP address prefixes to
   which the AS is authorized to originate routes. Note that the syntax
   here is more restrictive than that used in the IP Address Delegation
   extension defined in RFC 3779. That extension can represent arbitrary
   address ranges, whereas ROAs need to represent only prefixes.

   Within the ROAIPAddressFamily 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.

   Within a ROAIPAddress structure, the addresses field represents
   prefixes as a sequence of type IPAddress. (See [RFC3779] for more
   details). If present, the maxLength must be an integer greater than
   or equal to the length of the accompanying prefix and less than or
   equal to the length (in bits) of an IP address in the address family
   (32 for IPv4 and 128 for IPv6). When present, the maxLength specifies
   the maximum length of IP address prefix that the AS is authorized to
   advertise. (For example, if the IP Address prefix is 10.0/16 and the
   maxLength is 24, the AS is authorized to advertise any more specific
   prefix having length at most 24. That is, in this example, the AS
   would be authorized to advertise 10.0/16, 10.0.128/20, or


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   10.0.255/24, but not 10.0.255.0/25.) When the maxLength is not
   present, the AS is only authorized to advertise exactly the prefix
   specified in the ROA.

2.1.4. certificates

   The certificates field MUST be included and MUST contain only the end
   entity certificate needed to validate this ROA.

2.1.5. crls

   The crls field MUST be omitted.

2.1.6. 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 }

2.1.6.1. version

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

2.1.6.2. sid

   The sid is defined as:

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

   For a ROA, the sid MUST be a SubjectKeyIdentifier.

2.1.6.3. digestAlgorithm

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




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2.1.6.4. 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 ROA the attrValues must consist of only a single
   AttributeValue.

2.1.6.4.1. 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 ROA MUST be
   1.2.840.113549.1.9.16.1.24 (matching the eContentType in the
   EncapsulatedContentInfo).

2.1.6.4.2. 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 RFC 3852.





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2.1.6.4.3. 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 ROA (as
   specified in Section 3). 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.

2.1.6.4.4. 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
   ROA (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.

2.1.6.5. signatureAlgorithm

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







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2.1.6.6. signature

   The signature value is defined as:

      SignatureValue ::= OCTET STRING

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

2.1.6.7. unsignedAttrs

   unsignedAttrs MUST be omitted.

3. ROA Validation

   Before a relying party can use a ROA to validate a routing
   announcement, the relying party must first validate the ROA by
   verifying that all of the following conditions hold.

   1. The ROA syntax complies with this specification. In particular,
      that each of the following is true:

       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.

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

       f. The eContentType in the EncapsulatedContentInfo is
          routeOriginAttestation (OID 1.2.840.113549.1.9.16.1.24)

       g. The version of the RouteOriginAttestation is 0.

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

       i. The version of the SignerInfo is 3.




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       j. The digestAlgorithm in the SignerInfo object is SHA-256 (OID
          2.16.840.1.101.3.4.2.1).

       k. The signatureAlgorithm in the SignerInfo object is RSA (OID
          1.2.840.113549.1.1.1).

       l. 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).

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

   2. The public key of the EE certificate (contained within the ROA)
      can be used to verify the signature on the ROA.

   3. The IP Address Delegation extension [RFC3779] is present in the EE
      certificate (contained within the ROA) and each IP address
      prefix(es) in ROA is contained within the set of IP addresses
      specified by the EE certificate's IP address delegation extension.

   4. The EE certificate (contained within the ROA) is a valid end-
      entity certificate in the resource PKI as specified by [RESCERT].
      (In particular, there exists a valid certification path from a
      trust anchor to the EE certificate.)

4. Security Considerations

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

   The purpose of a ROA is to convey authorization for an AS to
   originate a route to the prefix(es) in the ROA. Thus the integrity of
   a ROA must be established. The ROA 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
   ROA signer to authorize the target AS to originate routes to the
   prefix(es) is established through use of the address space and AS
   number PKI described in [ARCH]. Specifically one must verify the
   signature on the ROA using an X.509 certificate issued under this
   PKI, and check that the prefix(es) in the ROA match those in the
   address space extension in the certificate.


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5. IANA Considerations

   None.

6. Acknowledgments

   The authors wish to thank Charles Gardiner, Russ Housley and
   George Michaelson for their help and contributions.









































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7. References

7.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3852] Housley, R., ''Cryptographic Message Syntax'', RFC 3852,
             July 2004.

   [RFC4055] Schaad, J., Kaliski, B., and Housley, R., ''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.

   [RFC3779] Lynn, C., Kent, S., and Seo, K., ''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.



7.2. Informative References

   [RSA]     Rivest, R., Shamir, A., and Adelman, L. M. 1978. A method
             for obtaining digital signatures and public-key
             cryptosystems. Commun. ACM 21, 2 (Feb.), 120-126.

   [ARCH]    Lepinski, M., Kent, S., and Barnes, R., "An Infrastructure
             to Support Secure Internet Routing," draft-ietf-sidr-arch-
             03.txt, February, 2008 (work in progress).

   [RESCERT] Huston, G., Michaelson, G., and Loomans, R., ''A Profile
             for X.509 PKIX Resource Certificates,'' draft-ietf-sidr-
             res-certs-14.txt, October, 2008 (work in progress).















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Authors' Addresses

   Matt Lepinski
   BBN Technologies
   10 Moulton Street
   Cambridge MA 02138

   Email: mlepinski@bbn.com

   Stephen Kent
   BBN Technologies
   10 Moulton Street
   Cambridge MA 02138

   Email: skent@bbn.com

   Derrick Kong
   BBN Technologies
   10 Moulton Street
   Cambridge MA 02138

   Email: dkong@bbn.com



























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Disclaimer of Validity

   This document and the information contained herein are provided on an
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Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.








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