Network Working Group D. Zhang
Internet-Draft Huawei
Intended status: Standards Track M. Bhatia
Expires: November 25, 2014 Alcatel-Lucent
V. Manral
Ionos Networks
M. Jethanandani
Ciena Corporation
May 24, 2014
Authenticating BFD using HMAC-SHA-2 procedures
draft-ietf-bfd-hmac-sha-05
Abstract
This document describes the mechanism to authenticate Bidirectional
Forwarding Detection (BFD) protocol packets using Hashed Message
Authentication Mode (HMAC) with the SHA-256, SHA-384, and SHA-512
algorithms. The described mechanism uses the Generic Cryptographic
Authentication and Generic Meticulous Cryptographic Authentication
sections to carry the authentication data. This document updates,
but does not supersede, the cryptographic authentication mechanism
specified in RFC 5880.
Requirements Language
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 RFC 2119 [RFC2119].
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 25, 2014.
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Copyright Notice
Copyright (c) 2014 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
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Cryptographic Aspects . . . . . . . . . . . . . . . . . . . . 3
2.1. Preperation of the Key . . . . . . . . . . . . . . . . . 4
2.2. First Hash . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Second Hash T . . . . . . . . . . . . . . . . . . . . . . 4
2.4. Result . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The cryptographic authentication mechanisms specified in BFD
[RFC5880] defines MD5 Message-Digest Algorithm [RFC1321] and Secure
Hash Algorithm (SHA-1) algorithms to authenticate BFD packets. The
recent escalating series of attacks on MD5 and SHA-1 [SHA-1-attack1]
[SHA-1-attack2] raise concerns about their remaining useful lifetime
as outlined in Updated Security Considerations for the MD5 Message-
Digest and the HMAC-MD5 Algorithm [RFC6151] and Security
Considerations for the SHA-0 and SHA-1 Message-Digest Algorithm
[RFC6194].
These attacks may not necessarily result in direct vulnerabilities
for Keyed-MD5 and Keyed-SHA-1 digests as message authentication codes
because the colliding message may not correspond to a syntactically
correct BFD protocol packet. Regardless, there is a need felt to
deprecate MD5 and SHA-1 as the basis for the HMAC algorithm in favor
of stronger digest algorithms.
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This document adds support for Secure Hash Algorithms (SHA) defined
in the US NIST Secure Hash Standard (SHS), which is defined by NIST
FIPS 180-2 [FIPS-180-2]. [FIPS-180-2] includes SHA-1, SHA-224,
SHA-256, SHA-384, and SHA-512. The HMAC authentication mode defined
in NIST FIPS 198 is used [FIPS-198].
It is believed that the HMAC algorithms defined in HMAC: Keyed-
Hashing for Message Authentication [RFC2104] is mathematically
identical to their counterparts in [FIPS-198] and it is also believed
that algorithms in US Secure Hash Algorithms [RFC6234] are
mathematically identical to those defined in [FIPS-180-2].
It should be noted that the collision attacks currently known against
SHA-1 do not apply when SHA-1 is used in the HMAC construction. NIST
will be supporting HMAC-SHA-1 even after 2010 [NIST-HMAC-SHA] ,
whereas it would be dropping support for SHA-1 in digital signatures.
BFD Generic Cryptographic Authentication
[I-D.ietf-bfd-generic-crypto-auth] defines new authentication types -
Generic Cryptographic Authentication (TBD1) and Generic Meticulous
Cryptographic Authentication (TBD2) that can be used for carrying the
authentication digests defined in this document. Also please refer
to this document for the procedures at the sending and the receiving
side.
Implementations of this specification must include support for at
least HMAC-SHA-256 and may include support for either of HMAC-SHA-384
or HMAC-SHA-512.
2. Cryptographic Aspects
In the algorithm description below, the following nomenclature, which
is consistent with [FIPS-198], is used.
H is the specific hashing algorithm (e.g. SHA-256).
K is the password for the BFD packet.
Ko is the cryptographic key used with the hash algorithm.
B is the block size of H, measured in octets rather than bits. Note,
that B is the internal block size, not the hash size. For SHA-1 and
SHA-256 B is equal to 64. For SHA-384 and SHA-512 B is equal to 128.
L is the length of the hash, measured in octets rather than bits.
XOR is the exclusive-or operation.
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Opad is the hexadecimal value 0x5c repeated B times.
Ipad is the hexadecimal value 0x36 repeated B times.
Apad is the hexadecimal value 0x878FE1F3 repeated (L/4) times.
2.1. Preperation of the Key
In this application, Ko is always L octets long.
If the Authentication Key (K) is L octets long, then Ko is equal to
K. If the Authentication Key (K) is more than L octets long, then Ko
is set to H(K). If the Authentication Key (K) is less than L octets
long, then Ko is set to the Authentication Key (K) with zeros
appended to the end of the Authentication Key (K) such that Ko is L
octets long.
2.2. First Hash
First, the Authentication Data field in the Generic Authentication
Section is filled with the value of Apad and the Authentication Type
field is set to TBD1 or TBD2 depending upon which Authentication Type
being used. The Sequence Number field MUST be set to
bfd.XmitAuthSeq.
Then, a first hash, also known as the inner hash, is computed as
follows:
First-Hash = H(Ko XOR Ipad || (BFD Packet))
2.3. Second Hash T
Then a second hash, also known as the outer hash, is computed as
follows:
Second-Hash = H(Ko XOR Opad || First-Hash)
2.4. Result
The resultant Second-Hash becomes the Authentication Data that is
sent in the Authentication Data field of the BFD Authentication
Section. The length of the Authentication Data field is always
identical to the message digest size of the specific hash function H
that is being used.
This also means that the use of hash functions with larger output
sizes will also increase the size of BFD Packet as transmitted on the
wire.
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3. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
4. Security Considerations
The approach described in this document enhances the security of the
BFD protocol by adding, to the existing BFD cryptographic
authentication methods, support for the SHA-2 algorithms defined in
the NIST Secure Hash Standard (SHS) using the HMAC mode. However,
the confidentiality protection for BFD packets is out of scope of
this work .
Because all of the currently specified algorithms use symmetric
cryptography, one cannot authenticate precisely which BFD device sent
a given packet. However, one can authenticate that the sender knew
the BFD Security Association (including the BFD SA's parameters)
currently in use.
To enhance system security, the applied keys should be changed
periodically and implementations SHOULD be able to store and use more
than one key at the same time. The quality of the security provided
by the cryptographic authentication option depends completely on the
strength of the cryptographic algorithm and cryptographic mode in
use, the strength of the key being used, and the correct
implementation of the security mechanism in all communicating BFD
implementations. Accordingly, the use of high assurance development
methods is recommended. It also requires that all parties maintain
the secrecy of the shared secret key. Randomness Requirements for
Security [RFC4086] provides guidance on methods for generating
cryptographically random bits.
The value Apad is used here primarily for consistency with IETF
specifications for HMAC-SHA authentication for RIPv2 RIPv2
Cryptographic Authentication [RFC4822], IS-IS IS-IS Generic
Cryptographic Authentication [RFC5310] and OSPFv2 OSPFv2 HMAC-SHA
Cryptographic Authentication [RFC5709].
5. References
5.1. Normative References
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[FIPS-180-2]
National Institute of Standards and Technology, FIPS PUB
180-2, "The Keyed-Hash Message Authentication Code
(HMAC)", August 2002.
[FIPS-198]
National Institute of Standards and Technology, FIPS PUB
198, "The Keyed-Hash Message Authentication Code (HMAC)",
March 2002.
[I-D.ietf-bfd-generic-crypto-auth]
Bhatia, M., Manral, V., Zhang, D., and M. Jethanandani,
"BFD Generic Cryptographic Authentication", draft-ietf-
bfd-generic-crypto-auth-06 (work in progress), April 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6039] Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues
with Existing Cryptographic Protection Methods for Routing
Protocols", RFC 6039, October 2010.
[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.
5.2. Informative References
[Dobb96a] Dobbertin, H., "Cryptanalysis of MD5 Compress", May 1996.
[Dobb96b] Dobbertin, H., "The Status of MD5 After a Recent Attack",
CryptoBytes", 1996.
[I-D.ietf-karp-design-guide]
Lebovitz, G. and M. Bhatia, "Keying and Authentication for
Routing Protocols (KARP) Design Guidelines", draft-ietf-
karp-design-guide-10 (work in progress), December 2011.
[MD5-attack]
Wang, X., Feng, D., Lai, X., and H. Yu, "Collisions for
Hash Functions MD4, MD5, HAVAL-128 and RIPEMD", August
2004.
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[NIST-HMAC-SHA]
National Institute of Standards and Technology, Available
online at http://csrc.nist.gov/groups/ST/hash/policy.html,
"NIST's Policy on Hash Functions", 2006.
[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.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4822] Atkinson, R. and M. Fanto, "RIPv2 Cryptographic
Authentication", RFC 4822, February 2007.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, February 2009.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, October 2009.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
[RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.
[SHA-1-attack1]
Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the
Full SHA-1", 2005.
[SHA-1-attack2]
Wang, X., Yao, A., and F. Yao, "New Collision Search for
SHA-1", 2005.
Authors' Addresses
Dacheng Zhang
Huawei
Beijing
China
Email: zhangdacheng@huawei.com
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Manav Bhatia
Alcatel-Lucent
Bangalore 560045
India
Email: manav.bhatia@alcatel-lucent.com
Vishwas Manral
Ionos Networks
CA
USA
Email: vishwas@ionosnetworks.com
Mahesh Jethanandani
Ciena Corporation
3939 North 1st Street
San Jose, CA 95134
USA
Phone: +1 (408) 904-2160
Email: mjethanandani@gmail.com
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