DNSext Working Group F. Dupont Internet-Draft ISC Updates: 2845,2930,4635
November 19, 2008April 27, 2009 (if approved) Intended status: Standards Track Expires: May 23,October 29, 2009 Deprecation of HMAC-MD5 in DNS TSIG and TKEY Resource Records draft-ietf-dnsext-tsig-md5-deprecated-01.txtdraft-ietf-dnsext-tsig-md5-deprecated-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claimsThis Internet-Draft is submitted to IETF in full conformance with the provisions of which heBCP 78 and BCP 79. This document may contain material from IETF Documents or she is aware have beenIETF Contributions published or willmade 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 current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 23,October 29, 2009. Copyright Notice Copyright (c) 2009 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 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 goal 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). 1. Introduction The secret key transaction authentication for DNS (TSIG, [RFC2845]) was defined with the HMAC-MD5 [RFC2104] cryptographic algorithm. As the MD5 [RFC1321] security was recognized to be 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 details: 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 updated into:replaced by: +-------------------+--------------------------+ | 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 columcolumn to the registry "Compliance Requirement". The registry should contain the following: +--------------------------+------------------------+-------------+ | Algorithm Name | Compliance Requirement | Reference | +--------------------------+------------------------+-------------+ | gss-tsig | Optional | [RFC3645] | | HMAC-MD5.SIG-ALG.REG.INT | Optional | [RFC2845][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. SecurityAvailability Considerations MD5 was provenis no more universally available and its use should lead to be less secure than expected in some uses, but HMAC-MD5increasing operation issues. SHA1 is not one of these uses, i.e., today HMAC-MD5 was not proved insecure [Bellovin]. But for many reasons likelikely to avoid insecure uses of MD5, or certificationsuffer from the same kind of cryptographic modules (e.g., [FIPS140-2], one cannot assumeproblem. To summary MD5 will be provided by all cryptographic modules, so even HMAC-MD5has reached end-of-life and SHA1 follows few years behind. According to [RFC4635], implementations which support TSIG are REQUIRED to implement HMAC-SHA256. 6. Security Considerations This document does not lead today toassume anything about the cryptographic security issues, it can lead to operational issues. The useof MD5 and HMAC-MD5different hash algorithms. It is NOT RECOMMENDEDa routine maintenance, its goal is better availability of some security mechanisms in a predictable future. Requirement levels are adjusted for TSIG and related specifications (i.e., TKEY). But SHA1 seems to be vulnerable too, so theTKEY): The use of at least SHA256MD5 and HMAC-MD5 is NOT RECOMMENDED. Implementations which support TSIG are REQUIRED to implement HMAC-SHA256, theThe use of HMAC-SHA256 algorithmis RECOMMENDED for default use in TSIG. 6.RECOMMENDED. 7. Acknowledgments Cryptographic module validation programs made MD5 not approved so not available. They provide a good incentive to deprecate MD5 at a place it is still mandatory to support and likely heavily used.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 and paulPaul Hoffman proposed some improvements. 7.8. References 220.127.116.11. 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. 18.104.22.168. Informative References [Bellovin] Bellovin, S., "[Cfrg] HMAC-MD5", March 2006, <http:// www.ietf.org/mail-archive/web/cfrg/current/msg01197.html>. [FIPS140-2] National Institute of Standards and Technology (NIST), "FIPS PUB 140-2: Security Requirements for Cryptographic Modules", May 2001, <http://csrc.nist.gov/publications/ fips/fips140-2/fips1402.pdf>.[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. Author's Address Francis Dupont ISC Email: Francis.Dupont@fdupont.fr Full 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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