Edit File: draft-ietf-dnsext-tsig-md5-deprecated-03.txt
DNSext Working Group F. Dupont Internet-Draft ISC Updates: 2845,2930,4635 May 8, 2009 (if approved) Intended status: Standards Track Expires: November 9, 2009 Deprecation of HMAC-MD5 in DNS TSIG and TKEY Resource Records draft-ietf-dnsext-tsig-md5-deprecated-03.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. 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The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on November 9, 2009. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. Dupont Expires November 9, 2009 [Page 1] Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract The main purpose of this document is to deprecate the use of HMAC-MD5 as an algorithm for the TSIG (secret key transaction authentication) resource record in the DNS (domain name system), and the use of MD5 in TKEY (secret key establishment for DNS). 1. Introduction The secret key transaction authentication for DNS (TSIG, [RFC2845]) was defined with the HMAC-MD5 [RFC2104] cryptographic algorithm. When the MD5 [RFC1321] security came to be considered lower than expected, [RFC4635] standardized new TSIG algorithms based on SHA [RFC3174][RFC3874][RFC4634] digests. But [RFC4635] did not deprecate the HMAC-MD5 algorithm. This document is targeted to complete the process, in detail: 1. Mark HMAC-MD5.SIG-ALG.REG.INT as optional in the TSIG algorithm name registry managed by the IANA under the IETF Review Policy [RFC5226] 2. Make HMAC-MD5.SIG-ALG.REG.INT support "not Mandatory" for implementations 3. Provide a keying material derivation for the secret key establishment for DNS (TKEY, [RFC2930]) using a Diffie-Hellman exchange with SHA256 [RFC4634] in place of MD5 [RFC1321] 4. Finally recommend the use of HMAC-SHA256. 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 [RFC2119]. 2. Implementation Requirements The table of section 3 of [RFC4635] is replaced by: Dupont Expires November 9, 2009 [Page 2] Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009 +-------------------+--------------------------+ | Requirement Level | Algorithm Name | +-------------------+--------------------------+ | Optional | HMAC-MD5.SIG-ALG.REG.INT | | Optional | gss-tsig | | Mandatory | hmac-sha1 | | Optional | hmac-sha224 | | Mandatory | hmac-sha256 | | Optional | hmac-sha384 | | Optional | hmac-sha512 | +-------------------+--------------------------+ Implementations that support TSIG MUST also implement HMAC-SHA1 and HMAC-SHA256 (i.e., algorithms at the "Mandatory" requirement level) and MAY implement GSS-TSIG and the other algorithms listed above (i.e., algorithms at a "not Mandatory" requirement level). 3. TKEY keying material derivation When the TKEY [RFC2930] uses a Diffie-Hellman exchange, the keying material is derived from the shared secret and TKEY resource record data using MD5 [RFC1321] at the end of section 4.1 page 9. This is amended into: keying material = XOR ( DH value, SHA256 ( query data | DH value ) | SHA256 ( server data | DH value ) ) using the same conventions. 4. IANA Consideration This document extends the "TSIG Algorithm Names - per [] and [RFC2845]" located at http://www.iana.org/assignments/tsig-algorithm-names by adding a new column to the registry "Compliance Requirement". The registry should contain the following: Dupont Expires November 9, 2009 [Page 3] Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009 +--------------------------+------------------------+-------------+ | Algorithm Name | Compliance Requirement | Reference | +--------------------------+------------------------+-------------+ | gss-tsig | Optional | [RFC3645] | | HMAC-MD5.SIG-ALG.REG.INT | Optional | [][RFC2845] | | hmac-sha1 | Mandatory | [RFC4635] | | hmac-sha224 | Optional | [RFC4635] | | hmac-sha256 | Mandatory | [RFC4635] | | hmac-sha384 | Optional | [RFC4635] | | hmac-sha512 | Optional | [RFC4635] | +--------------------------+------------------------+-------------+ where [] is this document. 5. Availability Considerations MD5 is no longer universally available and its use may lead to increasing operation issues. SHA1 is likely to suffer from the same kind of problem. In summary MD5 has reached end-of-life and SHA1 will likely follow in the near term. According to [RFC4635], implementations which support TSIG are REQUIRED to implement HMAC-SHA256. 6. Security Considerations This document does not assume anything about the cryptographic security of different hash algorithms. Its purpose is a better availability of some security mechanisms in a predictable time frame. Requirement levels are adjusted for TSIG and related specifications (i.e., TKEY): The support of HMAC-MD5 is changed from mandatory to optional. The use of MD5 and HMAC-MD5 is NOT RECOMMENDED. The use of HMAC-SHA256 is RECOMMENDED. 7. Acknowledgments Olafur Gudmundsson kindly helped in the procedure to deprecate the MD5 use in TSIG, i.e., the procedure which led to this memo. Alfred Hoenes, Peter Koch, Paul Hoffman and Edward Lewis proposed some improvements. 8. References Dupont Expires November 9, 2009 [Page 4] Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997. [RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D., and B. Wellington, "Secret Key Transaction Authentication for DNS (TSIG)", RFC 2845, May 2000. [RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY RR)", RFC 2930, September 2000. [RFC4635] Eastlake, D., "HMAC SHA TSIG Algorithm Identifiers", RFC 4635, August 2006. 8.2. Informative References [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- Hashing for Message Authentication", RFC 2104, February 1997. [RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1 (SHA1)", RFC 3174, September 2001. [RFC3645] Kwan, S., Garg, P., Gilroy, J., Esibov, L., Westhead, J., and R. Hall, "Generic Security Service Algorithm for Secret Key Transaction Authentication for DNS (GSS-TSIG)", RFC 3645, October 2003. [RFC3874] Housley, R., "A 224-bit One-way Hash Function: SHA-224", RFC 3874, September 2004. [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms (SHA and HMAC-SHA)", RFC 4634, July 2006. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, BCP 26, May 2008. Dupont Expires November 9, 2009 [Page 5] Internet-Draft Deprecating HMAC-MD5 in TSIG May 2009 Author's Address Francis Dupont ISC Email: Francis.Dupont@fdupont.fr Dupont Expires November 9, 2009 [Page 6]
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