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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Holmberg 3 Internet-Draft Ericsson 4 Updates: 4572 (if approved) March 21, 2016 5 Intended status: Standards Track 6 Expires: September 22, 2016 8 Updates to RFC 4572 9 draft-holmberg-mmusic-4572-update-01.txt 11 Abstract 13 This document updates RFC 4572 by clarifying the usage of multiple 14 SDP 'fingerprint' attributes with a single TLS connection. The 15 document also updates the preferred cipher suite to be used, and 16 removes the requirement to use the same hash function for calculating 17 the certificate fingerprint that is used to calculate the certificate 18 signature. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on September 22, 2016. 37 Copyright Notice 39 Copyright (c) 2016 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. Update to RFC 4572 . . . . . . . . . . . . . . . . . . . . . 3 57 3.1. Update to the sixth paragraph of section 5 . . . . . . . 3 58 3.2. New paragraphs to the end of section 5 . . . . . . . . . 4 59 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 60 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 61 6. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 7. Normative References . . . . . . . . . . . . . . . . . . . . 4 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 65 1. Introduction 67 RFC 4572 [RFC4572] specifies how to establish Transport Layer 68 Security (TLS) connections using the Session Description Protocol 69 (SDP) [RFC4566]. 71 RFC 4572 defines the SDP 'fingerprint' attribute, which is used to 72 carry a secure hash value associated with a certificate. However, 73 RFC 4572 is currently unclear on whether multiple 'fingerprint' can 74 be associated with a single SDP media description ("m= line") 75 [RFC4566], and the associated semantics. Multiple 'fingerprint' 76 attributes are needed when an endpoint wants to provide multiple 77 fingerprint, using different hash functions, for a certificate. 78 Multiple 'fingerprint' attributes are also needed if an endpoint 79 wants to provide fingerprints associated with multiple certificates. 80 For example, with RTP-based media, an endpoint might use different 81 certificates for RTP and RTCP. 83 RFC 4572 also specifies a preferred cipher suite. However, the 84 currently preferred cipher suite is considered outdated, and the 85 preference needs to be updated. 87 RFC 4572 mandates that the hash function used to calculate the 88 fingerprint is the same hash function used to calculate the 89 certificate signature. That requirement might prevent usage of 90 newer, stronger and more collision-safe hash functions for 91 calculating certificate fingerprints. 93 This document updates RFC 4572 [RFC4572] by clarifying the usage of 94 multiple SDP 'fingerprint' attributes with a single TLS connection. 95 The document also updates the preferred cipher suite to be used, and 96 removes the requirement to use the same hash function for calculating 97 the certificiate fingerprint and certificate signature. 99 2. Conventions 101 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 102 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 103 document are to be interpreted as described in [RFC2119]. 105 3. Update to RFC 4572 107 This section updates section 5 of RFC 4572. 109 3.1. Update to the sixth paragraph of section 5 111 OLD TEXT: 113 A certificate fingerprint MUST be computed using the same one-way 114 hash function as is used in the certificate's signature algorithm. 115 (This ensures that the security properties required for the 116 certificate also apply for the fingerprint. It also guarantees that 117 the fingerprint will be usable by the other endpoint, so long as the 118 certificate itself is.) Following RFC 3279 [7] as updated by RFC 119 4055 [9], therefore, the defined hash functions are 'SHA-1' [11] 120 [19], 'SHA-224' [11], 'SHA-256' [11], 'SHA-384' [11], 'SHA-512' [11], 121 'MD5' [12], and 'MD2' [13], with 'SHA-1' preferred. A new IANA 122 registry of Hash Function Textual Names, specified in Section 8, 123 allows for addition of future tokens, but they may only be added if 124 they are included in RFCs that update or obsolete RFC 3279 [7]. 125 Self-signed certificates (for which legacy certificates are not a 126 consideration) MUST use one of the FIPS 180 algorithms (SHA-1, 127 SHA-224, SHA-256, SHA-384, or SHA-512) as their signature algorithm, 128 and thus also MUST use it to calculate certificate fingerprints. 130 NEW TEXT: 132 Following RFC 3279 [7] as updated by RFC 4055 [9], therefore, the 133 defined hash functions are 'SHA-1' [11] [19], 'SHA-224' [11], 134 'SHA-256' [11], 'SHA-384' [11], 'SHA-512' [11], 'MD5' [12], and 135 'MD2' [13], with 'SHA-256' preferred. A new IANA registry of Hash 136 Function Textual Names, specified in Section 8, allows for addition 137 of future tokens, but they may only be added if they are included 138 in RFCs that update or obsolete RFC 3279 [7]. 140 3.2. New paragraphs to the end of section 5 142 NEW TEXT: 144 Multiple SDP fingerprint attributes can be associated with an m- line. 145 This can occur if multiple fingerprints have been calculated for a 146 certificate, using different hash algorithms. It can also occur if 147 multiple certificates might be used (e.g. separate certificates for 148 RTP and RTCP). In such cases, the same number of fingerprints MUST be 149 calculated for each certificate, and for each certificate the same set 150 of hash algorithms MUST be used. 152 An endpoint MUST be able to match at least one of the received 153 fingerprints with the cerficiate(s) to be used. If there is no match, 154 the endpoint MUST NOT establish the TLS connection. 156 NOTE: The SDP fingerprint attribute does not contain a reference to 157 a specific certificate. Endpoints need to compare all fingerprints with 158 the cerficiate hash when looking for a match. 160 4. Security Considerations 162 This document improves security. 164 5. Acknowledgements 166 Martin Thompson, Paul Kyzivat and Jonathan Lennox provided valuable 167 comments and input on this document. 169 6. Change Log 171 [RFC EDITOR NOTE: Please remove this section when publishing] 173 Changes from draft-holmberg-mmusic-4572-update-xx 175 o Add text 177 7. Normative References 179 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 180 Requirement Levels", BCP 14, RFC 2119, 181 DOI 10.17487/RFC2119, March 1997, 182 . 184 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 185 with Session Description Protocol (SDP)", RFC 3264, 186 DOI 10.17487/RFC3264, June 2002, 187 . 189 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 190 Transport Layer Security (TLS) Protocol in the Session 191 Description Protocol (SDP)", RFC 4572, 192 DOI 10.17487/RFC4572, July 2006, 193 . 195 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 196 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 197 July 2006, . 199 Author's Address 201 Christer Holmberg 202 Ericsson 203 Hirsalantie 11 204 Jorvas 02420 205 Finland 207 Email: christer.holmberg@ericsson.com