Network Working Group A. Melnikov, Ed.
Internet-Draft Isode Ltd
Intended status: Standards Track May 14, 2020
Expires: November 15, 2020
SCRAM-SHA-512 and SCRAM-SHA-512-PLUS Simple Authentication and Security
Layer (SASL) Mechanisms
draft-melnikov-scram-sha-512-00
Abstract
This document registers the Simple Authentication and Security Layer
(SASL) mechanisms SCRAM-SHA-512 and SCRAM-SHA-512-PLUS.
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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 4096.
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.
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4. Security Considerations
The security considerations from [RFC5802] still apply.
To be secure, either SCRAM-SHA-512-PLUS and SCRAM-SHA-1-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.
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 4096 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 4096, 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
Minimum iteration-count: 4096
OID: 1.3.6.1.5.5.<TBD>
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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: 4096
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>.
[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>.
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[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>.
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>.
[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>.
[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>.
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Acknowledgements
This document is based on RFC 7677 by Tony Hansen.
Author's Address
Alexey Melnikov (editor)
Isode Ltd
14 Castle Mews
Hampton, Middlesex TW12 2NP
UK
EMail: alexey.melnikov@isode.com
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