SCRAM-SHA-512 and SCRAM-SHA-512-PLUS Simple Authentication and Security Layer (SASL) Mechanisms
draft-melnikov-scram-sha-512-02

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Author Alexey Melnikov 
Last updated 2021-10-19
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Network Working Group                                   A. Melnikov, Ed.
Internet-Draft                                                 Isode Ltd
Intended status: Standards Track                         19 October 2021
Expires: 22 April 2022

SCRAM-SHA-512 and SCRAM-SHA-512-PLUS Simple Authentication and Security
                        Layer (SASL) Mechanisms
                    draft-melnikov-scram-sha-512-02

Abstract

   This document registers the Simple Authentication and Security Layer
   (SASL) mechanisms SCRAM-SHA-512 and SCRAM-SHA-512-PLUS.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 22 April 2022.

Copyright Notice

   Copyright (c) 2021 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
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   provided without warranty as described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Key Word Definitions  . . . . . . . . . . . . . . . . . . . .   2
   3.  SCRAM-SHA-512 and SCRAM-SHA-512-PLUS  . . . . . . . . . . . .   2
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This document registers the SASL [RFC4422] mechanisms SCRAM-SHA-512
   and SCRAM-SHA-512-PLUS.  SHA-512 has stronger security properties
   than SHA-1, and it is expected that SCRAM mechanisms based on it will
   have greater predicted longevity than the SCRAM mechanisms based on
   SHA-1.

2.  Key Word Definitions

   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

3.  SCRAM-SHA-512 and SCRAM-SHA-512-PLUS

   The SCRAM-SHA-512 and SCRAM-SHA-512-PLUS SASL mechanisms are defined
   in the same way that SCRAM-SHA-1 and SCRAM-SHA-1-PLUS are defined in
   [RFC5802], except that the hash function for HMAC() and H() uses
   SHA-512 instead of SHA-1 [RFC6234].

   For the SCRAM-SHA-512 and SCRAM-SHA-512-PLUS SASL mechanisms, the
   hash iteration-count announced by a server SHOULD be at least 10000.

   The GSS-API mechanism OID for SCRAM-SHA-512 is 1.3.6.1.5.5.<TBD> (see
   Section 5).

   This is a simple example of a SCRAM-SHA-512 authentication exchange
   when the client doesn't support channel bindings.  The username
   'user' and password 'pencil' are being used.

   [[TBD: Add an example]]

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4.  Security Considerations

   The security considerations from [RFC5802] still apply.

   To be secure, SCRAM-SHA-512-PLUS MUST be used over a TLS channel that
   has had the session hash extension [RFC7627] negotiated, or session
   resumption MUST NOT have been used.  When using SCRAM over TLS 1.2
   [RFC5246], the "tls-unique" channel binding is still the default
   channel binding to use (see Section 6.1 of [RFC5802]), assuming the
   above conditions are satisfied.  As "tls-unique" channel binding is
   not defined for TLS 1.3 [RFC8446], when using SCRAM over TLS 1.3, the
   "tls-exporter" channel binding [tls-1.3-channel-binding] MUST be the
   default channel binding (in the sense specified in Section 6.1 of
   [RFC5802]) to use.

   See [RFC4270] and [RFC6194] for reasons to move from SHA-1 to a
   strong security mechanism like SHA-512.

   The strength of this mechanism is dependent in part on the hash
   iteration-count, as denoted by "i" in [RFC5802].  As a rule of thumb,
   the hash iteration-count should be such that a modern machine will
   take 0.1 seconds to perform the complete algorithm; however, this is
   unlikely to be practical on mobile devices and other relatively low-
   performance systems.  At the time this was written, the rule of thumb
   gives around 15,000 iterations required; however, a hash iteration-
   count of 10000 takes around 0.5 seconds on current mobile handsets.
   This computational cost can be avoided by caching the ClientKey
   (assuming the Salt and hash iteration-count is stable).  Therefore,
   the recommendation of this specification is that the hash iteration-
   count SHOULD be at least 10000, but careful consideration ought to be
   given to using a significantly higher value, particularly where
   mobile use is less important.

5.  IANA Considerations

   IANA is requested to add the following new SASL SCRAM mechanisms to
   the "SASL SCRAM Family Mechanisms" registry:

      To:  iana@iana.org

      Subject:  Registration of a new SASL SCRAM Family mechanism SCRAM-
         SHA-512

      SASL mechanism name (or prefix for the family):  SCRAM-SHA-512

      Security considerations:  Section 4 of RFC XXXX

      Published specification (optional, recommended):  RFC XXXX

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      Minimum iteration-count:  10000

      OID:  1.3.6.1.5.5.<TBD>

      Person & email address to contact for further information:  IETF
         KITTEN WG <kitten@ietf.org>

      Intended usage:  COMMON

      Owner/Change controller:  IESG <iesg@ietf.org>

      Note:

      To:  iana@iana.org

      Subject:  Registration of a new SASL SCRAM Family mechanism SCRAM-
         SHA-512-PLUS

      SASL mechanism name (or prefix for the family):  SCRAM-SHA-
         512-PLUS

      Security considerations:  Section 4 of RFC XXXX

      Published specification (optional, recommended):  RFC XXXX

      Minimum iteration-count:  10000

      OID:  1.3.6.1.5.5.<TBD>

      Person & email address to contact for further information:  IETF
         KITTEN WG <kitten@ietf.org>

      Intended usage:  COMMON

      Owner/Change controller:  IESG <iesg@ietf.org>

      Note:

6.  References

6.1.  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>.

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   [RFC4422]  Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
              Authentication and Security Layer (SASL)", RFC 4422,
              DOI 10.17487/RFC4422, June 2006,
              <https://www.rfc-editor.org/info/rfc4422>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5802]  Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams,
              "Salted Challenge Response Authentication Mechanism
              (SCRAM) SASL and GSS-API Mechanisms", RFC 5802,
              DOI 10.17487/RFC5802, July 2010,
              <https://www.rfc-editor.org/info/rfc5802>.

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,
              <https://www.rfc-editor.org/info/rfc6234>.

   [RFC7627]  Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
              Langley, A., and M. Ray, "Transport Layer Security (TLS)
              Session Hash and Extended Master Secret Extension",
              RFC 7627, DOI 10.17487/RFC7627, September 2015,
              <https://www.rfc-editor.org/info/rfc7627>.

   [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>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [tls-1.3-channel-binding]
              Whited, S., "Channel Bindings for TLS 1.3", Work in
              Progress, Internet-Draft, draft-ietf-kitten-tls-channel-
              bindings-for-tls13-11, 18 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-kitten-tls-
              channel-bindings-for-tls13-11.txt>.

6.2.  Informative References

   [RFC4270]  Hoffman, P. and B. Schneier, "Attacks on Cryptographic
              Hashes in Internet Protocols", RFC 4270,
              DOI 10.17487/RFC4270, November 2005,
              <https://www.rfc-editor.org/info/rfc4270>.

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   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [RFC6194]  Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
              Considerations for the SHA-0 and SHA-1 Message-Digest
              Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
              <https://www.rfc-editor.org/info/rfc6194>.

Acknowledgements

   This document is based on RFC 7677 by Tony Hansen.

   Thank you to Ludovic Bocquet for comments and corrections.

Author's Address

   Alexey Melnikov (editor)
   Isode Ltd
   14 Castle Mews
   Hampton
   TW12 2NP
   United Kingdom

   Email: alexey.melnikov@isode.com

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