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(See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) -- The draft header indicates that this document updates RFC5246, but the abstract doesn't seem to mention this, which it should. -- The draft header indicates that this document updates RFC7525, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: In addition, the use of the SHA-256 hash algorithm is RECOMMENDED, SHA-1 or MD5 MUST not be used (see [CAB-Baseline] for more details). Clients MUST indicate to servers that they request SHA-256, by using the "Signature Algorithms" extension defined in TLS 1.2. (Using the creation date from RFC5246, updated by this document, for RFC5378 checks: 2006-03-02) -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (January 16, 2020) is 1562 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) -- Obsolete informational reference (is this intentional?): RFC 5246 (Obsoleted by RFC 8446) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force L. Velvindron 3 Internet-Draft cyberstorm.mu 4 Updates: 5246 7525 (if approved) K. Moriarty 5 Intended status: Standards Track Dell EMC 6 Expires: July 19, 2020 A. Ghedini 7 Cloudflare Inc. 8 January 16, 2020 10 Deprecating MD5 and SHA-1 signature hashes in TLS 1.2 11 draft-ietf-tls-md5-sha1-deprecate-01 13 Abstract 15 The MD5 and SHA-1 hashing algorithms are steadily weakening in 16 strength and their deprecation process should begin for their use in 17 TLS 1.2 digital signatures. However, this document does not 18 deprecate SHA-1 in HMAC for record protection. 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 https://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 July 19, 2020. 37 Copyright Notice 39 Copyright (c) 2020 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 (https://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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 56 2. Signature Algorithms . . . . . . . . . . . . . . . . . . . . 2 57 3. Certificate Request . . . . . . . . . . . . . . . . . . . . . 3 58 4. Server Key Exchange . . . . . . . . . . . . . . . . . . . . . 3 59 5. Certificate Verify . . . . . . . . . . . . . . . . . . . . . 3 60 6. Updates to RFC5246 . . . . . . . . . . . . . . . . . . . . . 3 61 7. Updates to RFC7525 . . . . . . . . . . . . . . . . . . . . . 3 62 8. Security Considerations . . . . . . . . . . . . . . . . . . . 4 63 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 4 64 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 10.1. Normative References . . . . . . . . . . . . . . . . . . 4 66 10.2. Informative References . . . . . . . . . . . . . . . . . 5 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 69 1. Introduction 71 The usage of MD5 and SHA-1 for signature hashing in TLS 1.2 is 72 specified in RFC 5246 [RFC5246]. MD5 and SHA-1 have been proven to 73 be insecure, subject to collision attacks. RFC 6151 [RFC6151] 74 details the security considerations, including collision attacks for 75 MD5, published in 2011. NIST formally deprecated use of SHA-1 in 76 2011 [NISTSP800-131A-R2] and disallowed its use for digital 77 signatures at the end of 2013, based on both the Wang, et. al, attack 78 and the potential for brute-force attack. Further, in 2017, 79 researchers from Google and CWI Amsterdam [SHA-1-Collision] proved 80 SHA-1 collision attacks were practical. This document updates 81 RFC 5246 [RFC5246] and RFC7525 [RFC7525] in such as way that MD5 and 82 SHA1 MUST NOT be used for digital signatures. However, this document 83 does not deprecate SHA-1 in HMAC for record protection. 85 1.1. Requirements Language 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in RFC 2119 [RFC2119]. 91 2. Signature Algorithms 93 Clients SHOULD NOT include MD5 and SHA-1 in signature_algorithms 94 extension. If a client does not send a signature_algorithms 95 extension, then the server MUST abort the handshake and send a 96 handshake_failure alert, except when digital signatures are not used 97 (for example, when using PSK ciphers). 99 3. Certificate Request 101 Servers SHOULD NOT include MD5 and SHA-1 in CertificateRequest 102 message. 104 4. Server Key Exchange 106 Servers MUST NOT include MD5 and SHA-1 in ServerKeyExchange message. 107 If client does receive a MD5 or SHA-1 signature in the 108 ServerKeyExchange message it MUST abort the connection with 109 handshake_failure or insufficient_security alert. 111 5. Certificate Verify 113 Clients MUST NOT include MD5 and SHA-1 in CertificateVerify message. 115 6. Updates to RFC5246 117 OLD: 119 In Section 7.4.1.4.1: the text should be revised from " Note: this is 120 a change from TLS 1.1 where there are no explicit rules, but as a 121 practical matter one can assume that the peer supports MD5 and SHA- 122 1." 124 NEW: 126 "Note: This is a change from TLS 1.1 where there are no explicit 127 rules, but as a practical matter one can assume that the peer 128 supports SHA-256." 130 7. Updates to RFC7525 132 RFC7525 [RFC7525], Recommendations for Secure Use of Transport Layer 133 Security (TLS) and Datagram Transport Layer Security (DTLS) 134 recommends use of SHA-256 as a minimum requirement. This update 135 moves the minimum recommendation to use stronger language deprecating 136 use of both SHA-1 and MD5. The prior text did not explicitly include 137 MD5 and this text adds it to ensure it is understood as having been 138 deprecated. 140 Section 4.3: 142 OLD: 144 When using RSA, servers SHOULD authenticate using certificates with 145 at least a 2048-bit modulus for the public key. In addition, the use 146 of the SHA-256 hash algorithm is RECOMMENDED (see [CAB-Baseline] for 147 more details). Clients SHOULD indicate to servers that they request 148 SHA-256, by using the "Signature Algorithms" extension defined in TLS 149 1.2. 151 NEW: 153 servers SHOULD authenticate using certificates with at least a 154 2048-bit modulus for the public key. 156 In addition, the use of the SHA-256 hash algorithm is RECOMMENDED, 157 SHA-1 or MD5 MUST not be used (see [CAB-Baseline] for more details). 158 Clients MUST indicate to servers that they request SHA-256, by using 159 the "Signature Algorithms" extension defined in TLS 1.2. 161 8. Security Considerations 163 Concerns with TLS 1.2 implementations falling back to SHA-1 is an 164 issue. This draft updates the TLS 1.2 specification to deprecate 165 support for MD5 and SHA-1 for digital signatures. However, this 166 document does not deprecate SHA-1 in HMAC for record protection. 168 9. Acknowledgement 170 The authors would like to thank Hubert Kario for his help in writing 171 the initial draft. We are also grateful to Daniel Migault, Martin 172 Thomson and David Cooper for their feedback. 174 10. References 176 10.1. Normative References 178 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 179 Requirement Levels", BCP 14, RFC 2119, 180 DOI 10.17487/RFC2119, March 1997, 181 . 183 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 184 "Recommendations for Secure Use of Transport Layer 185 Security (TLS) and Datagram Transport Layer Security 186 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 187 2015, . 189 10.2. Informative References 191 [CAB-Baseline] 192 CA/Browser Forum, "Baseline Requirements for the Issuance 193 and Management of Publicly-Trusted Certificates Version 194 1.1.6", 2013, . 196 [NISTSP800-131A-R2] 197 Barker, E. and A. Roginsky, "Transitioning the Use of 198 Cryptographic Algorithms and Key Lengths", March 2019, 199 . 202 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 203 (TLS) Protocol Version 1.2", RFC 5246, 204 DOI 10.17487/RFC5246, August 2008, 205 . 207 [RFC6151] Turner, S. and L. Chen, "Updated Security Considerations 208 for the MD5 Message-Digest and the HMAC-MD5 Algorithms", 209 RFC 6151, DOI 10.17487/RFC6151, March 2011, 210 . 212 [SHA-1-Collision] 213 Stevens, M., Bursztein, E., Karpman, P., Albertini, A., 214 and Y. Markov, "The first collision for full SHA-1", March 215 2019, . 217 Authors' Addresses 219 Loganaden Velvindron 220 cyberstorm.mu 221 Rose Hill 222 MU 224 Phone: +230 59762817 225 Email: logan@cyberstorm.mu 227 Kathleen Moriarty 228 Dell EMC 230 Email: Kathleen.Moriarty.ietf@gmail.com 231 Alessandro Ghedini 232 Cloudflare Inc. 234 Email: alessandro@cloudflare.com