Subject: [Sidr] ROA Format -03

From: Matt Lepinski <[email-masked]>
Date: Mon, 07 Jul 2008 08:56:03 -0400

I have submitted the attached file as draft-sidr-roa-format-03.

The significant changes in this version are:
- The EE certificate used to verify a ROA must be included in the CMS 
wrapper of the ROA.
- The signed attributes ContentType and MessageDigest must be included 
in the CMS wrapper for the ROA, other signed attributes may be included.
- As proposed in Philidelphia, the syntax of the ROA was changed to 
allow the issuer to authorize the advertisement of prefixes up to a 
given maxLength.

Please let me know if you have any comments on improving the clarity or 
content of the draft.

- Matt Lepinski
Secure Inter-Domain Routing (sidr)                          M. Lepinski 
Internet Draft                                                  S. Kent 
Expires: January 2009                                           D. Kong 
Intended Status: Proposed Standard                     BBN Technologies 
                                                           July 7, 2008 
                                      
             A Profile for Route Origin Authorizations (ROAs) 
                     draft-ietf-sidr-roa-format-03.txt 

Status of this Memo 

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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. 

Conventions used in this document 

   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]. 

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Table of Contents 

   1. Introduction...................................................2 
   2. Basic Format...................................................3 
      2.1. Signed-Data Content Type..................................3 
         2.1.1. version..............................................3 
         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.....................................6 
               2.1.6.4.1. ContentType Attribute......................7 
               2.1.6.4.2. MessageDigest Attribute....................7 
               2.1.6.4.3. SigningTime Attribute......................7 
               2.1.6.4.4. BinarySigningTimeAttribute.................8 
            2.1.6.5. signatureAlgorithm..............................8 
            2.1.6.6. signature.......................................8 
            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 

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   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.  
   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 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 

2.1.1. version 

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

 
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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 } 
     
      ASID ::= INTEGER 
       
      ROAIPAddressFamily ::= SEQUENCE { 

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         addressFamily OCTET STRING (SIZE (2..3)), 
         addresses SEQUENCE OF ROAIPAddress } 

      ROAIPAddress ::= SEQUENCE { 
         address IPAdress, 
         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 
   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. 

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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] 

2.1.6.4. signedAttrs 

   The signedAttrs is defined as: 

 
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         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. 

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 

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   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.  

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. 

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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 use the resource PKI to 
   validate the ROA by performing the following steps. 

   1. Verify that the ROA 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. 

       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. 

       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). 

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

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

   3. Verify that the EE certificate has an IP Address Delegation 
      extension [RFC3779] and that the IP address prefix(es) in that 
      extension exactly matches the IP address prefix(es) in the ROA. 

   4. 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 [RESCERT] for more details.) 

   Note that requiring an exact match between the IP address prefix(es) 
   in a ROA and the IP address prefix(es) in the corresponding EE 
   certificate does not place any limitations on ROA use. Indeed, since 
   each EE certificate in the resource RPKI architecture is used to 
   verify only a single ROA, it is natural to have the IP address 
   prefixes in the certificate match those in the corresponding ROA. 
   When the issuer of a ROA does not require an exact match between the 
   IP address prefix(es) in the ROA and the prefix(es) advertised by the 
   AS (when it originates routes for the prefix), the issuer includes 
   the maxLength element within the ROAIPAddress to indicate that the AS 
   is authorized to advertise more specific prefixes than those 
   indicated in the ROA (up to the specified maxLength values). 

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 and Russ Housley 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. 

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-10.txt, June, 2008 (work in progress). 

    

 
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Authors' Addresses 

   Matt Lepinski 
   BBN Technologies 
   10 Moulton Street 
   Cambridge MA 02138 
    
   Email: [email-masked] 
    
   Stephen Kent 
   BBN Technologies 
   10 Moulton Street 
   Cambridge MA 02138 
    
   Email: [email-masked] 
    
   Derrick Kong 
   BBN Technologies 
   10 Moulton Street 
   Cambridge MA 02138 
       
   Email: [email-masked] 

    

    

    

 
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Disclaimer of Validity 

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Copyright Statement 

   Copyright (C) The IETF Trust (2008). 

   This document is subject to the rights, licenses and restrictions 
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   retain all their rights. 

 
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