SCRAM-SHA-256 and SCRAM-SHA-256-PLUS SASL Mechanisms
draft-hansen-scram-sha256-01

Abstract

This document registers the SASL mechanisms SCRAM-SHA-256 and SCRAM-SHA-256-PLUS. It also updates RFC 5802 in minor ways.

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Copyright Notice

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Table of Contents

• 1. Introduction
• 2. SCRAM-SHA-256 and SCRAM-SHA-256-PLUS
• 3. Security Considerations
• 4. IANA Considerations
• 5. Acknowledgements
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Author's Address

1. Introduction

This document registers the SASL mechanisms SCRAM-SHA-256 and SCRAM-SHA-256-PLUS.

The registration form for the SCRAM family of algorithms is also updated.

Note: this paragraph may be removed before publication.
This document was written because [RFC5802] requires that new SASL mechanisms in the SCRAM family be subject to IETF review. This document is being discussed in the KITTEN working group (see the kitten@ietf.org mailing list). It was pursued further because of a desire for its use within a document being discussed in the HTTP-AUTH working group (see the httpauth@ietf.org mailing list).

2. SCRAM-SHA-256 and SCRAM-SHA-256-PLUS

The SCRAM-SHA-256 and SCRAM-SHA-256-PLUS SASL mechanism 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-256 instead of SHA-1 [RFC6234].

For the SCRAM-SHA-256/SCRAM-SHA-256-PLUS SASL mechanisms, servers SHOULD announce a hash iteration-count of at least 4096.
!!!!!!!!!!!!!!!! Note that the appropriate value to specify here needs to be discussed further. !!!!!!!!!!!!!!!!

The GSS-API mechanism OID for SCRAM-SHA-256 is TBD1 (see Section 4).

This is a simple example of a SCRAM-SHA-256 authentication exchange when the client doesn't support channel bindings (username 'user' and password 'pencil' are used):

C:

n,,n=user,r=rOprNGfwEbeRWgbNEkqO

S:

r=rOprNGfwEbeRWgbNEkqO%hvYDpWUa2RaTCAfuxFIlj)hNlF$k0,
s=W22ZaJ0SNY7soEsUEjb6gQ==,i=4096

C:

c=biws,r=rOprNGfwEbeRWgbNEkqO%hvYDpWUa2RaTCAfuxFIlj)hNlF$k0,
p=dHzbZapWIk4jUhN+Ute9ytag9zjfMHgsqmmiz7AndVQ=

S:

v=6rriTRBi23WpRR/wtup+mMhUZUn/dB5nLTJRsjl95G4=

3. Security Considerations

The security considerations from [RFC5802] still apply.

4. IANA Considerations

The IANA registry for the SCRAM family of SASL mechanisms is updated as follows. This revised form adds two new fields: Minimum iteration-count and Associated OID. In addition, the email address for reviews has been updated.

• To: iana@iana.org
  Subject: Registration of a new SASL family SCRAM
• SASL mechanism name (or prefix for the family): SCRAM-*
  Security considerations: Section 7 of [RFC5802]
  Published specification (optional, recommended): RFCXXXX
  Minimum iteration-count: The minimum iteration-count that servers SHOULD announce
  Associated OID: IANA SHOULD assign a GSS-API mechanism OID for this mechanism from the iso.org.dod.internet.security.mechanisms prefix (see the "SMI Security for Mechanism Codes" registry). Only one OID needs to be assigned for a SCRAM-* and SCRAM-*-PLUS pair. The same OID should be assigned to both entries in the registry.
  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: Members of this family MUST be explicitly registered using the "IETF Review" [RFC5226] registration procedure. Reviews MUST be requested on the KITTEN mailing list kitten@ietf.org (or a successor designated by the responsible Security AD).
  !!!!!!!!!!!!!!!! Can we change this to expert review? !!!!!!!!!!!!!!!!
• Note to future SCRAM-mechanism designers: each new SCRAM-SASL mechanism MUST be explicitly registered with IANA and MUST comply with SCRAM-mechanism naming convention defined in Section 4 of [RFC5802].

The following values are to be added to the existing registries for SASL SCRAM-SHA-1 and SCRAM-SHA-1-PLUS:

• Minimum iteration-count: 4096
  OID: 1.3.6.1.5.5.14 (from [RFC5802])

The following new SASL SCRAM mechanisms are added:

• IANA has added the following entries to the SASL Mechanism registry established by [RFC4422]:
• To: iana@iana.org
  Subject: Registration of a new SASL mechanism SCRAM-SHA-256
• SASL mechanism name (or prefix for the family): SCRAM-SHA-256
  Security considerations: Section Section 3 of RFCXXXX
  Published specification (optional, recommended): RFCXXXX
  Minimum iteration-count: 4096
  OID: TBD1
  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 mechanism SCRAM-SHA-256-PLUS
• SASL mechanism name (or prefix for the family): SCRAM-SHA-256-PLUS
  Security considerations: Section Section 3 of RFCXXXX
  Published specification (optional, recommended): RFCXXXX
  Minimum iteration-count: 4096
  OID: TBD1
  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:

[This note may be removed on publication.] IANA needs to assign the GSS-API mechanism OID TBD1 listed above from the iso.org.dod.internet.security.mechanisms prefix (see the "SMI Security for Mechanism Codes" registry).

5. Acknowledgements

This document benefited from discussions on the KITTEN WG mailing list. The author would like to specially thank Russ Albery, Dave Cridland, Shawn Emery, Simon Josefsson, and Alexey Melnikov for their comments on this topic.

6. References

6.1. Normative References

6.2. Informative References

Author's Address