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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) May 4, 2016 5 Intended status: Standards Track 6 Expires: November 5, 2016 8 Updates to RFC 4572 9 draft-ietf-mmusic-4572-update-00.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 November 5, 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. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 61 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 62 7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 4 63 8. Normative References . . . . . . . . . . . . . . . . . . . . 5 64 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 66 1. Introduction 68 RFC 4572 [RFC4572] specifies how to establish Transport Layer 69 Security (TLS) connections using the Session Description Protocol 70 (SDP) [RFC4566]. 72 RFC 4572 defines the SDP 'fingerprint' attribute, which is used to 73 carry a secure hash value associated with a certificate. However, 74 RFC 4572 is currently unclear on whether multiple 'fingerprint' can 75 be associated with a single SDP media description ("m= line") 76 [RFC4566], and the associated semantics. Multiple 'fingerprint' 77 attributes are needed when an endpoint wants to provide multiple 78 fingerprint, using different hash functions, for a certificate. 79 Multiple 'fingerprint' attributes are also needed if an endpoint 80 wants to provide fingerprints associated with multiple certificates. 81 For example, with RTP-based media, an endpoint might use different 82 certificates for RTP and RTCP. 84 RFC 4572 also specifies a preferred cipher suite. However, the 85 currently preferred cipher suite is considered outdated, and the 86 preference needs to be updated. 88 RFC 4572 mandates that the hash function used to calculate the 89 fingerprint is the same hash function used to calculate the 90 certificate signature. That requirement might prevent usage of 91 newer, stronger and more collision-safe hash functions for 92 calculating certificate fingerprints. 94 This document updates RFC 4572 [RFC4572] by clarifying the usage of 95 multiple SDP 'fingerprint' attributes with a single TLS connection. 96 The document also updates the preferred cipher suite to be used, and 97 removes the requirement to use the same hash function for calculating 98 the certificate fingerprint and certificate signature. 100 2. Conventions 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 104 document are to be interpreted as described in [RFC2119]. 106 3. Update to RFC 4572 108 This section updates section 5 of RFC 4572. 110 3.1. Update to the sixth paragraph of section 5 112 OLD TEXT: 114 A certificate fingerprint MUST be computed using the same one-way 115 hash function as is used in the certificate's signature algorithm. 116 (This ensures that the security properties required for the 117 certificate also apply for the fingerprint. It also guarantees that 118 the fingerprint will be usable by the other endpoint, so long as the 119 certificate itself is.) Following RFC 3279 [7] as updated by RFC 120 4055 [9], therefore, the defined hash functions are 'SHA-1' [11] 121 [19], 'SHA-224' [11], 'SHA-256' [11], 'SHA-384' [11], 'SHA-512' [11], 122 'MD5' [12], and 'MD2' [13], with 'SHA-1' preferred. A new IANA 123 registry of Hash Function Textual Names, specified in Section 8, 124 allows for addition of future tokens, but they may only be added if 125 they are included in RFCs that update or obsolete RFC 3279 [7]. 126 Self-signed certificates (for which legacy certificates are not a 127 consideration) MUST use one of the FIPS 180 algorithms (SHA-1, 128 SHA-224, SHA-256, SHA-384, or SHA-512) as their signature algorithm, 129 and thus also MUST use it to calculate certificate fingerprints. 131 NEW TEXT: 133 Following RFC 3279 [7] as updated by RFC 4055 [9], therefore, the 134 defined hash functions are 'SHA-1' [11] [19], 'SHA-224' [11], 135 'SHA-256' [11], 'SHA-384' [11], 'SHA-512' [11], 'MD5' [12], and 136 'MD2' [13], with 'SHA-256' preferred. A new IANA registry of Hash 137 Function Textual Names, specified in Section 8, allows for addition 138 of future tokens, but they may only be added if they are included 139 in RFCs that update or obsolete RFC 3279 [7]. 141 3.2. New paragraphs to the end of section 5 143 NEW TEXT: 145 Multiple SDP fingerprint attributes can be associated with an m- 146 line. This can occur if multiple fingerprints have been calculated 147 for a certificate, using different hash algorithms. It can also 148 occur if multiple certificates might be used (e.g. separate 149 certificates for RTP and RTCP). In such cases, the same number of 150 fingerprints MUST be calculated for each certificate, and for each 151 certificate the same set of hash algorithms MUST be used. 153 An endpoint MUST be able to match at least one of the received 154 fingerprints with the cerficiate(s) to be used. If there is no 155 match, the endpoint MUST NOT establish the TLS connection. 157 NOTE: The SDP fingerprint attribute does not contain a reference to 158 a specific certificate. Endpoints need to compare all fingerprints 159 with the cerficiate hash when looking for a match. 161 4. Security Considerations 163 This document improves security. 165 5. IANA Considerations 167 This document makes no requests from IANA. 169 6. Acknowledgements 171 Martin Thompson, Paul Kyzivat and Jonathan Lennox provided valuable 172 comments and input on this document. 174 7. Change Log 176 [RFC EDITOR NOTE: Please remove this section when publishing] 178 Changes from draft-holmberg-mmusic-4572-update-01 180 o Adopted WG document (draft-ietf-mmusic-4572-update-00) submitted. 182 o IANA considerations section added. 184 8. Normative References 186 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 187 Requirement Levels", BCP 14, RFC 2119, 188 DOI 10.17487/RFC2119, March 1997, 189 . 191 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 192 with Session Description Protocol (SDP)", RFC 3264, 193 DOI 10.17487/RFC3264, June 2002, 194 . 196 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 197 Transport Layer Security (TLS) Protocol in the Session 198 Description Protocol (SDP)", RFC 4572, 199 DOI 10.17487/RFC4572, July 2006, 200 . 202 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 203 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 204 July 2006, . 206 Author's Address 208 Christer Holmberg 209 Ericsson 210 Hirsalantie 11 211 Jorvas 02420 212 Finland 214 Email: christer.holmberg@ericsson.com