Updates to RFC 4572
draft-ietf-mmusic-4572-update-02
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (mmusic WG) | |
|---|---|---|---|
| Author | Christer Holmberg | ||
| Last updated | 2016-05-18 | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text xml htmlized pdfized bibtex | ||
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draft-ietf-mmusic-4572-update-02
Network Working Group C. Holmberg
Internet-Draft Ericsson
Updates: 4572 (if approved) May 18, 2016
Intended status: Standards Track
Expires: November 19, 2016
Updates to RFC 4572
draft-ietf-mmusic-4572-update-02.txt
Abstract
This document updates RFC 4572 by clarifying the usage of multiple
SDP 'fingerprint' attributes with a single TLS connection. The
document also updates the preferred cipher suite to be used, and
removes the requirement to use the same hash function for calculating
a certificate fingerprint that is used to calculate the certificate
signature.
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
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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 19, 2016.
Copyright Notice
Copyright (c) 2016 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
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Holmberg Expires November 19, 2016 [Page 1]
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Update to RFC 4572 . . . . . . . . . . . . . . . . . . . . . 3
3.1. Update to the sixth paragraph of section 5 . . . . . . . 3
3.2. New paragraphs to the end of section 5 . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
RFC 4572 [RFC4572] specifies how to establish Transport Layer
Security (TLS) connections using the Session Description Protocol
(SDP) [RFC4566].
RFC 4572 defines the SDP 'fingerprint' attribute, which is used to
carry a secure hash value (fingerprint) associated with a
certificate. However, RFC 4572 is currently unclear on whether
multiple 'fingerprint' attributes can be associated with a single SDP
media description ("m= line") [RFC4566], and the associated
semantics. Multiple fingerprints are needed if an endpoints wants to
provide fingerprints associated with multiple certificates. For
example, with RTP-based media, an endpoint might use different
certificates for RTP and RTCP.
RFC 4572 also specifies a preferred cipher suite. However, the
currently preferred cipher suite is considered outdated, and the
preference needs to be updated.
RFC 4572 mandates that the hash function used to calculate the
fingerprint is the same hash function used to calculate the
certificate signature. That requirement might prevent usage of
newer, stronger and more collision-safe hash functions for
calculating certificate fingerprints. This change also requires that
multiple 'fingerprint' attributes can be associated with a single
"m=" line, so that implementations are able to provide fingerprints
calculated using updated hash functions alongside those that are
needed to interoperate with existing implementations.
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This document updates RFC 4572 [RFC4572] by clarifying the usage of
multiple SDP 'fingerprint' attributes. It is clarified that multiple
'fingerprint' attributes can be used to carry fingerprints,
calculated using different hash functions, associated with a given
certificate, and to carry fingerprints associated with multiple
certificates. The fingerprint matching procedure, when multiple
fingerprints are provided, are also clarified. The document also
updates the preferred cipher suite to be used, and removes the
requirement to use the same hash function for calculating a
certificate fingerprint and certificate signature.
2. Conventions
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].
3. Update to RFC 4572
This section updates section 5 of RFC 4572.
3.1. Update to the sixth paragraph of section 5
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OLD TEXT:
A certificate fingerprint MUST be computed using the same one-way
hash function as is used in the certificate's signature algorithm.
(This ensures that the security properties required for the
certificate also apply for the fingerprint. It also guarantees that
the fingerprint will be usable by the other endpoint, so long as the
certificate itself is.) Following RFC 3279 [7] as updated by RFC
4055 [9], therefore, the defined hash functions are 'SHA-1' [11]
[19], 'SHA-224' [11], 'SHA-256' [11], 'SHA-384' [11], 'SHA-512' [11]
, 'MD5' [12], and 'MD2' [13], with 'SHA-1' preferred. A new IANA
registry of Hash Function Textual Names, specified in Section 8,
allows for addition of future tokens, but they may only be added if
they are included in RFCs that update or obsolete RFC 3279 [7].
Self-signed certificates (for which legacy certificates are not a
consideration) MUST use one of the FIPS 180 algorithms (SHA-1,
SHA-224, SHA-256, SHA-384, or SHA-512) as their signature algorithm,
and thus also MUST use it to calculate certificate fingerprints.
NEW TEXT:
Following RFC 3279 [7] as updated by RFC 4055 [9], therefore, the
defined hash functions are 'SHA-1' [11] [19], 'SHA-224' [11],
'SHA-256' [11], 'SHA-384' [11], 'SHA-512' [11], 'MD5' [12], and
'MD2' [13], with 'SHA-256' preferred. A new IANA registry of Hash
Function Textual Names, specified in Section 8, allows for addition
of future tokens, but they may only be added if they are included
in RFCs that update or obsolete RFC 3279 [7].
3.2. New paragraphs to the end of section 5
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NEW TEXT:
Multiple SDP fingerprint attributes can be associated with an m-
line. This can occur if multiple fingerprints have been calculated
for a certificate, using different hash functions. It can also
occur if one or more fingerprints associated with multiple
certificates have been calculated, e.g. for cases where multiple
certificates will be used for media associated with an m- line
(e.g. separate certificates for RTP and RTCP), or where it is not
known which certificate will be used when the fingerprints are
exchanged. In such cases, one or more fingerprints MUST be
calculated for each possible certificate.
If fingerprints associated with multiple certificates are
calculated, the same set of fingerprints (using the same hash
functions) MUST be calculated for each certificate associated
with the m- line.
For each used certificate, an endpoint MUST be able to match at
least one fingerprint, calculated using the hash function that the
endpoint supports and considers most secure, with the used
certificate. If there is no match, the endpoint MUST NOT establish
the TLS connection. In addition, the endpoint MAY also check other
fingerprints (calculated using other hash functions) that it has
received for a match. For each hash function checked, one of the
received fingerprints MUST match the used certificate.
NOTE: The SDP fingerprint attribute does not contain a reference to
a specific certificate. Endpoints need to compare the fingerprint
with a certificate hash in order to look for a match.
4. Security Considerations
This document improves security. It updates the preferred hash
function cipher suite from SHA-1 to SHA-256. By clarifying the usage
and handling of multiple fingerprints, the document also enables hash
agility, and incremental deployment of newer, and more secure, cipher
suites.
5. IANA Considerations
This document makes no requests from IANA.
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6. Acknowledgements
Martin Thomson, Paul Kyzivat, Jonathan Lennox and Roman Shpount
provided valuable comments and input on this document.
7. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-4572-update-01
o Changes based on comments from Martin Thomson.
o - Editorial fixes
o Changes in handling of multiple fingerprints.
o - Sender must send same set of hash functions for each offered
certificate.
o - Receiver must check the hash function it considers most secure
for a match. It may check other hash functions.
Changes from draft-ietf-mmusic-4572-update-00
o Changes in handling of multiple fingerprints.
o - Number of fingerprints calculated for each certificate does not
have to match.
o - Clarified that receiver shall check check fingerprints using
hash algorithms it considers safe.
o - Additional text added to security considerations section.
Changes from draft-holmberg-mmusic-4572-update-01
o Adopted WG document (draft-ietf-mmusic-4572-update-00) submitted.
o IANA considerations section added.
8. References
8.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<http://www.rfc-editor.org/info/rfc3264>.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572,
DOI 10.17487/RFC4572, July 2006,
<http://www.rfc-editor.org/info/rfc4572>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
8.2. Informative References
[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009,
<http://www.rfc-editor.org/info/rfc5576>.
[I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12
(work in progress), January 2016.
[I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
negotiation-29 (work in progress), April 2016.
Author's Address
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
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