Internet DRAFT - draft-dbider-sha2-mac-for-ssh
draft-dbider-sha2-mac-for-ssh
Network Working Group d. bider
Internet-Draft Bitvise Limited
Updates: 4253 (if approved) M. Baushke
Intended status: Standards Track Juniper Networks, Inc.
Expires: November 4, 2012 May 3, 2012
SHA-2 Data Integrity Verification for the Secure Shell (SSH) Transport
Layer Protocol
draft-dbider-sha2-mac-for-ssh-06
Abstract
This memo defines algorithm names and parameters for use of some of
the SHA-2 family of secure hash algorithms for data integrity
verification in the Secure Shell (SSH) protocol. It also updates
RFC4253 by specifying a new RECOMMENDED data integrity algorithm.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 4, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
1. Overview and Rationale
Secure Shell (SSH) [RFC4251] is a very common protocol for secure
remote login on the Internet. Currently, SSH defines data integrity
verification using SHA-1 and MD5 algorithms [RFC4253]. Due to recent
security concerns with these two algorithms [RFC6151][RFC6194],
implementors and users request support for data integrity
verification using some of the SHA-2 family of of secure hash
algorithms.
Please send comments on this draft to ietf-ssh@NetBSD.org.
1.1. Requirements Terminology
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. Data Integrity Algorithms
This memo adopts the style and conventions of [RFC4253] in specifying
how the use of new data integrity algorithms is indicated in SSH.
The following new data integrity algorithms are defined:
hmac-sha2-256 RECOMMENDED HMAC-SHA2-256
(digest length = 32 bytes,
key length = 32 bytes)
hmac-sha2-512 OPTIONAL HMAC-SHA2-512
(digest length = 64 bytes,
key length = 64 bytes)
Figure 1
The HMAC mechanism was originally defined in [RFC2104] and has been
updated in [RFC6151].
The SHA-2 family of secure hash algorithms are defined in
[FIPS-180-3].
Sample code for the SHA-based HMAC algorithms are available in
[RFC6234]. The variants HMAC-SHA2-224 and HMAC-SHA2-384 algorithms
were considered, but not added to this list as they have the same
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computational requirements of HMAC-SHA2-256 and HMAC-SHA2-512
respectively and do not seem to be much used in practice.
Test vectors for use of HMAC with SHA-2 are provided in [RFC4231].
Users, implementors, and administrators may choose to put these new
Macs into the proposal ahead of the REQUIRED hmac-sha1 algorithm
defined in [RFC4253] so that they would be negotiated first.
3. IANA Considerations
This document augments the MAC Algorithm Names in [RFC4253] and
[RFC4250].
IANA is requested to update the SSH algorithm registry with the
following entries:
MAC Algorithm Name Reference Note
hmac-sha2-256 This draft Section 2
hmac-sha2-512 This draft Section 2
Figure 2
4. Security Considerations
The security considerations of RFC 4253 [RFC4253] apply to this
document.
The National Institute of Standards and Technology (NIST)
publications: NIST Special Publication (SP) 800-107 [800-107] and
NIST SP 800-131A [800-131A] suggest that HMAC-SHA1 and HMAC-SHA2-256
have a security strength of 128 bits and 256 bits respectively which
are considered acceptable key lengths.
Many users seem to be interested in the perceived safety of using the
SHA2-based algorithms for hashing.
5. References
5.1. Normative References
[FIPS-180-3]
National Institute of Standards and Technology (NIST),
United States of America, "Secure Hash Standard (SHS)",
FIPS PUB 180-3, October 2008, <http://csrc.nist.gov/
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publications/fips/fips180-3/fips180-3_final.pdf>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4231] Nystrom, M., "Identifiers and Test Vectors for HMAC-SHA-
224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
RFC 4231, December 2005.
[RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, January 2006.
5.2. Informative References
[800-107] National Institute of Standards and Technology (NIST),
"Recommendation for Applications Using Approved Hash
Algorithms", NIST Special Publication 800-107,
February 2009, <http://csrc.nist.gov/publications/
nistpubs/800-107/NIST-SP-800-107.pdf>.
[800-131A]
National Institute of Standards and Technology (NIST),
"Transitions: Recommendation for the Transitioning of the
Use of Cryptographic Algorithms and Key Lengths", DRAFT
NIST Special Publication 800-131A, January 2011, <http://
csrc.nist.gov/publications/nistpubs/800-131A/
sp800-131A.pdf>.
[RFC4250] Lehtinen, S. and C. Lonvick, "SSH Protocol Assigned
Numbers", RFC 4250, January 2006.
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, March 2011.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, March 2011.
[RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.
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Authors' Addresses
denis bider
Bitvise Limited
Suites 41/42, Victoria House
26 Main Street
Gibraltar
GI
Phone: +1 869 762 1410
Email: ietf-ssh2@denisbider.com
URI: http://www.bitvise.com/
Mark D. Baushke
Juniper Networks, Inc.
1194 N Mathilda Av
Sunnyvale, CA 94089-1206
US
Phone: +1 408 745 2952
Email: mdb@juniper.net
URI: http://www.juniper.net/
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