RFC 8608
BGPsec Algorithms, Key Formats, and Signature Formats
Internet Engineering Task Force (IETF) S. Turner Request for Comments: 8608 sn3rd Obsoletes: 8208 O. Borchert Updates: 7935 NIST Category: Standards Track June 2019 ISSN: 2070-1721 BGPsec Algorithms, Key Formats, and Signature FormatsAbstract
This document specifies the algorithms, algorithm parameters, asymmetric key formats, asymmetric key sizes, and signature formats used in BGPsec (Border Gateway Protocol Security). This document updates RFC 7935 ("The Profile for Algorithms and Key Sizes for Use in the Resource Public Key Infrastructure") and obsoletes RFC 8208 ("BGPsec Algorithms, Key Formats, and Signature Formats") by adding Documentation and Experimentation Algorithm IDs, correcting the range of unassigned algorithms IDs to fill the complete range, and restructuring the document for better reading. This document also includes example BGPsec UPDATE messages as well as the private keys used to generate the messages and the certificates necessary to validate those signatures. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8608.
Copyright Notice Copyright (c) 2019 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 (https://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 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 1.2. Changes from RFC 8208 . . . . . . . . . . . . . . . . . . 4 2. Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Algorithm ID Types . . . . . . . . . . . . . . . . . . . 4 2.2. Signature Algorithms . . . . . . . . . . . . . . . . . . 6 2.2.1. Algorithm ID 0x01 (1) - (ECDSA P-256) . . . . . . . . 6 3. Asymmetric Key Pair Formats . . . . . . . . . . . . . . . . . 6 3.1. Asymmetric Key Pair for Algorithm ID 0x01 (1) - (ECDSA P-256) . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1.1. Public Key Format . . . . . . . . . . . . . . . . . . 6 3.1.2. Private Key Format . . . . . . . . . . . . . . . . . 7 4. Signature Formats . . . . . . . . . . . . . . . . . . . . . . 7 5. Additional Requirements . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . 11 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 12 A.1. Topology and Experiment Description . . . . . . . . . . . 12 A.2. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . 12 A.3. BGPsec IPv4 . . . . . . . . . . . . . . . . . . . . . . . 16 A.4. BGPsec IPv6 . . . . . . . . . . . . . . . . . . . . . . . 18 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
This document specifies the following: o the digital signature algorithm and parameters, o the hash algorithm and parameters, o the algorithm identifier assignment and classification, o the public and private key formats, and o the signature formats used by Resource Public Key Infrastructure (RPKI) Certification Authorities (CAs) and BGPsec (Border Gateway Protocol Security) speakers (i.e., routers). CAs use these algorithms when processing requests for BGPsec Router Certificates [RFC8209]. Examples of when BGPsec routers use these algorithms include requesting BGPsec certificates [RFC8209], signing BGPsec UPDATE messages [RFC8205], and verifying signatures on BGPsec UPDATE messages [RFC8205]. This document updates [RFC7935] to add support for a) a different algorithm for BGPsec certificate requests, which are issued only by BGPsec speakers; b) a different Subject Public Key Info format for BGPsec certificates, which is needed for the specified BGPsec signature algorithm; and c) different signature formats for BGPsec signatures, which are needed for the specified BGPsec signature algorithm. The BGPsec certificates are differentiated from other RPKI certificates by the use of the BGPsec Extended Key Usage as defined in [RFC8209]. BGPsec uses a different algorithm [RFC6090] [DSS] from the rest of the RPKI to provide similar security with smaller keys, making the certificates smaller; these algorithms also result in smaller signatures, which make the PDUs smaller. Appendix A (non-normative) contains example BGPsec UPDATE messages as well as the private keys used to generate the messages and the certificates necessary to validate the signatures.1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
1.2. Changes from RFC 8208
This section describes the significant changes between [RFC8208] and this document. o Added Section 2.1 containing Algorithm ID types. Also, the interpretation of these IDs is described. o Restructured Sections 2 and 3 to align with the corresponding algorithm suite identifier value. o Corrected the range for unassigned algorithm suite identifier values. o Added Documentation algorithm suite identifier values. o Added Experimentation algorithm suite identifier values. o Changed the next-hop IP in Appendix A's IPv6 example to use a private usage IPv6 address.2. Algorithms
The algorithms used to compute signatures on CA certificates, BGPsec Router Certificates, and Certificate Revocation Lists (CRLs) are as specified in Section 2 of [RFC7935]. This section addresses algorithms used by BGPsec [RFC8205] [DSS]. For example, these algorithms are used by BGPsec routers to sign and verify BGPsec UPDATE messages. To identify which algorithm is used, the BGPsec UPDATE message contains the corresponding algorithm ID in each Signature_Block of the BGPsec UPDATE message.2.1. Algorithm ID Types
Algorithms in BGPsec UPDATE messages are identified by the Algorithm Suite Identifier field (algorithm ID) within the Signature_Block (see Section 3.2 of [RFC8205]). This document specifies five types of Algorithm IDs: o Reserved Algorithm ID Reserved algorithm IDs are the values 0x00 (0) and 0xFF (255). These IDs MUST NOT be used in a Signature_Block, and if encountered, the router MUST treat BGPsec UPDATE messages as malformed [RFC4271].
o Signature Algorithm ID
Signature algorithms are defined in Section 2.2 of this document.
Processing of BGPsec UPDATE signing and validation using signature
algorithms is described at length in Sections 4.2 and 5.2 of
[RFC8205].
o Unassigned Algorithm ID
This type of Algorithm ID is free for future assignments and MUST
NOT be used until an algorithm is officially assigned (see
Section 7). In case a router encounters an unassigned algorithm
ID in one of the Signature_Blocks of a BGPsec UPDATE message, the
router SHOULD process the Signature_Block as an unsupported
algorithm as specified in Section 5.2 of [RFC8205].
o Experimentation Algorithm ID
Experimentation algorithm IDs span from 0xF7 (247) to 0xFA (250).
To allow experimentation to accurately describe deployment
examples, the use of publicly assigned algorithm IDs is
inappropriate, and a reserved block of Experimentation algorithm
IDs is required. This ensures that experimentation does not clash
with assigned algorithm IDs in deployed networks and mitigates the
risks to operational integrity of the network through
inappropriate use of experimentation to perform literal
configuration of routing elements on production systems. A router
that encounters an algorithm ID of this type outside of an
experimental network SHOULD treat it the same as an unsupported
algorithm as specified in Section 5.2 of [RFC8205].
o Documentation Algorithm ID
Documentation algorithm IDs span from 0xFB (251) to 0xFE (254).
To allow documentation to accurately describe deployment examples,
the use of publicly assigned algorithm IDs is inappropriate, and a
reserved block of Documentation algorithm IDs is required. This
ensures that documentation does not clash with assigned algorithm
IDs in deployed networks and mitigates the risks to operational
integrity of the network through inappropriate use of
documentation to perform literal configuration of routing elements
on production systems. A router that encounters an algorithm ID
of this type SHOULD treat it the same as an unsupported algorithm
as specified in Section 5.2 of [RFC8205].
2.2. Signature Algorithms
2.2.1. Algorithm ID 0x01 (1) - (ECDSA P-256)
o The signature algorithm used MUST be the Elliptic Curve Digital Signature Algorithm (ECDSA) with curve P-256 [RFC6090] [DSS]. o The hash algorithm used MUST be SHA-256 [SHS]. Hash algorithms are not identified by themselves in certificates or BGPsec UPDATE messages. They are represented by an OID that combines the hash algorithm with the digital signature algorithm as follows: o The ecdsa-with-SHA256 OID [RFC5480] MUST appear in the Public-Key Cryptography Standards #10 (PKCS #10) signatureAlgorithm field [RFC2986] or in the Certificate Request Message Format (CRMF) POPOSigningKey algorithm field [RFC4211]; where the OID is placed depends on the certificate request format generated. o In BGPsec UPDATE messages, the ECDSA with SHA-256 algorithm suite identifier value 0x01 (1) (see Section 7) is included in the Signature_Block List's Algorithm Suite Identifier field.3. Asymmetric Key Pair Formats
The key formats used to compute signatures on CA certificates, BGPsec Router Certificates, and CRLs are as specified in Section 3 of [RFC7935]. This section addresses key formats found in the BGPsec Router Certificate requests and in BGPsec Router Certificates.3.1. Asymmetric Key Pair for Algorithm ID 0x01 (1) - (ECDSA P-256)
The ECDSA private keys used to compute signatures for certificate requests and BGPsec UPDATE messages MUST be associated with the P-256 elliptic curve domain parameters [RFC5480]. The public key pair MUST use the uncompressed form.3.1.1. Public Key Format
The Subject's public key is included in subjectPublicKeyInfo [RFC5280]. It has two sub-fields: algorithm and subjectPublicKey. The values for the structures and their sub-structures follow: o algorithm (an AlgorithmIdentifier type): The id-ecPublicKey OID MUST be used in the algorithm field, as specified in Section 2.1.1 of [RFC5480]. The value for the associated parameters MUST be secp256r1, as specified in Section 2.1.1.1 of [RFC5480].
o subjectPublicKey: ECPoint MUST be used to encode the certificate's
subjectPublicKey field, as specified in Section 2.2 of [RFC5480].
3.1.2. Private Key Format
Local policy determines private key format.
4. Signature Formats
The structure for the certificate's and CRL's signature field MUST be
as specified in Section 4 of [RFC7935]; this is the same format used
by other RPKI certificates. The structure for the certification
request's and BGPsec UPDATE message's signature field MUST be as
specified in Section 2.2.3 of [RFC3279].
5. Additional Requirements
It is anticipated that BGPsec will require the adoption of updated
key sizes and a different set of signature and hash algorithms over
time, in order to maintain an acceptable level of cryptographic
security. This profile should be updated to specify such future
requirements, when appropriate.
The recommended procedures to implement such a transition of key
sizes and algorithms are specified in [RFC6916].
6. Security Considerations
The security considerations of [RFC3279], [RFC5480], [RFC6090],
[RFC7935], and [RFC8209] apply to certificates. The security
considerations of [RFC3279], [RFC6090], [RFC7935], and [RFC8209]
apply to certification requests. The security considerations of
[RFC3279], [RFC6090], and [RFC8205] apply to BGPsec UPDATE messages.
No new security considerations are introduced as a result of this
specification.
7. IANA Considerations
The Internet Assigned Numbers Authority (IANA) has created the
"BGPsec Algorithm Suites" registry in the Resource Public Key
Infrastructure (RPKI) group. The one-octet algorithm suite
identifiers assigned by IANA identify the digest algorithm and
signature algorithm used in the BGPsec Signature_Block List's
Algorithm Suite Identifier field.
Per [RFC8208], IANA registered a single algorithm suite identifier
for the digest algorithm SHA-256 [SHS] and for the signature
algorithm ECDSA on the P-256 curve [RFC6090] [DSS]. This identifier
is still valid, and IANA has updated the registration to refer to
this document.
IANA has modified the range of the "Unassigned" address space from
"0x2-0xEF" to "0x02-0xF6":
Algorithm Digest Signature Specification
Suite Algorithm Algorithm Pointer
Identifier
+------------+---------------+--------------+-----------------------+
| 0x02-0xF6 | Unassigned | Unassigned | |
+------------+---------------+--------------+-----------------------+
In addition, IANA has registered the following address spaces for
"Experimentation" and "Documentation":
Algorithm Digest Signature Specification
Suite Algorithm Algorithm Pointer
Identifier
+------------+-----------------+-----------------+------------------+
| 0xF7-0xFA | Experimentation | Experimentation | This document |
+------------+-----------------+-----------------+------------------+
| 0xFB-0xFE | Documentation | Documentation | This document |
+------------+-----------------+-----------------+------------------+
The "BGPsec Algorithm Suites" registry in the RPKI group now contains
the following values:
Algorithm Digest Signature Specification
Suite Algorithm Algorithm Pointer
Identifier
+------------+-----------------+-----------------+------------------+
| 0x00 | Reserved | Reserved | This document |
+------------+-----------------+-----------------+------------------+
| 0x01 | SHA-256 | ECDSA P-256 | [SHS] [DSS] |
| | | | [RFC6090] |
| | | | This document |
+------------+-----------------+-----------------+------------------+
| 0x02-0xF6 | Unassigned | Unassigned | |
+------------+-----------------+-----------------+------------------+
| 0xF7-0xFA | Experimentation | Experimentation | This document |
+------------+-----------------+-----------------+------------------+
| 0xFB-0xFE | Documentation | Documentation | This document |
+------------+-----------------+-----------------+------------------+
| 0xFF | Reserved | Reserved | This document |
+------------+-----------------+-----------------+------------------+
Future assignments are to be made using the Standards Action process defined in [RFC8126]. Assignments consist of the one-octet algorithm suite identifier value and the associated digest algorithm name and signature algorithm name.8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification Request Syntax Specification Version 1.7", RFC 2986, DOI 10.17487/RFC2986, November 2000, <https://www.rfc-editor.org/info/rfc2986>. [RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3279, DOI 10.17487/RFC3279, April 2002, <https://www.rfc-editor.org/info/rfc3279>. [RFC4211] Schaad, J., "Internet X.509 Public Key Infrastructure Certificate Request Message Format (CRMF)", RFC 4211, DOI 10.17487/RFC4211, September 2005, <https://www.rfc-editor.org/info/rfc4211>. [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, <https://www.rfc-editor.org/info/rfc4271>. [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, DOI 10.17487/RFC5280, May 2008, <https://www.rfc-editor.org/info/rfc5280>. [RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, "Elliptic Curve Cryptography Subject Public Key Information", RFC 5480, DOI 10.17487/RFC5480, March 2009, <https://www.rfc-editor.org/info/rfc5480>.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic Curve Cryptography Algorithms", RFC 6090, DOI 10.17487/RFC6090, February 2011, <https://www.rfc-editor.org/info/rfc6090>. [RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility Procedure for the Resource Public Key Infrastructure (RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April 2013, <https://www.rfc-editor.org/info/rfc6916>. [RFC7935] Huston, G. and G. Michaelson, Ed., "The Profile for Algorithms and Key Sizes for Use in the Resource Public Key Infrastructure", RFC 7935, DOI 10.17487/RFC7935, August 2016, <https://www.rfc-editor.org/info/rfc7935>. [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. [RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol Specification", RFC 8205, DOI 10.17487/RFC8205, September 2017, <https://www.rfc-editor.org/info/rfc8205>. [RFC8208] Turner, S. and O. Borchert, "BGPsec Algorithms, Key Formats, and Signature Formats", RFC 8208, DOI 10.17487/RFC8208, September 2017, <https://www.rfc-editor.org/info/rfc8208>. [RFC8209] Reynolds, M., Turner, S., and S. Kent, "A Profile for BGPsec Router Certificates, Certificate Revocation Lists, and Certification Requests", RFC 8209, DOI 10.17487/RFC8209, September 2017, <https://www.rfc-editor.org/info/rfc8209>. [DSS] National Institute of Standards and Technology, "Digital Signature Standard (DSS)", NIST FIPS Publication 186-4, DOI 10.6028/NIST.FIPS.186-4, July 2013, <https://nvlpubs.nist.gov/nistpubs/FIPS/ NIST.FIPS.186-4.pdf>.
[SHS] National Institute of Standards and Technology, "Secure Hash Standard (SHS)", NIST FIPS Publication 180-4, DOI 10.6028/NIST.FIPS.180-4, August 2015, <https://nvlpubs.nist.gov/nistpubs/FIPS/ NIST.FIPS.180-4.pdf>.8.2. Informative References
[RFC5398] Huston, G., "Autonomous System (AS) Number Reservation for Documentation Use", RFC 5398, DOI 10.17487/RFC5398, December 2008, <https://www.rfc-editor.org/info/rfc5398>. [RFC6979] Pornin, T., "Deterministic Usage of the Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, August 2013, <https://www.rfc-editor.org/info/rfc6979>.
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