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Checking references for intended status: Best Current Practice ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'IANA' is mentioned on line 123, but not defined == Missing Reference: 'RFC-TBD' is mentioned on line 132, but not defined -- Possible downref: Non-RFC (?) normative reference: ref. 'SCHNEIER' -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force L. Camara 3 Internet-Draft 4 Obsoletes: 4325 (if approved) L. Velvindron 5 Updates: 4253 (if approved) September 3, 2018 6 Intended status: Best Current Practice 7 Expires: March 7, 2019 9 Deprecating RC4 in Secure Shell (SSH) 10 draft-ietf-curdle-rc4-die-die-die-09 12 Abstract 14 This document deprecates RC4 in Secure Shell (SSH). Therefore, this 15 document updates [RFC4253], and formally obsoletes and moves to 16 Historic [RFC4345]. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on March 7, 2019. 35 Copyright Notice 37 Copyright (c) 2018 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 54 2. Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . 2 55 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 56 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 57 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 58 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 60 6.2. Informative References . . . . . . . . . . . . . . . . . 4 61 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 63 1. Introduction 65 The usage of RC4 suites ( also designated as arcfour ) for SSH are 66 specified in [RFC4253] and [RFC4345]. [RFC4253] specifies the 67 allocation of the "arcfour" cipher for SSH. [RFC4345] specifies and 68 allocates the the "arcfour-128" and "arcfour-256" ciphers for SSH. 69 RC4 encryption is steadily weakening in cryptographic strength 70 [RFC7465] [I-D.ietf-curdle-des-des-des-die-die-die], and the 71 deprecation process should be begun for their use in Secure Shell 72 (SSH) [RFC4253]. Accordingly, [RFC4253] is updated to note the 73 deprecation of the RC4 ciphers and [RFC4345] is moved to Historic as 74 all ciphers it specifies MUST NOT be used. 76 1.1. Requirements Language 78 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 79 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 80 document are to be interpreted as described in RFC 2119 [RFC2119]. 82 2. Updates to RFC 4253 84 [RFC4253] is updated to prohibit arcfour's use in SSH. [RFC4253] 85 allocates the "arcfour" cipher in Section 6.3 by defining a list of 86 defined ciphers where the "arcfour" cipher appears as optional as 87 mentioned below: 89 +---------------+-----------------+---------------------------------+ 90 | arcfour | OPTIONAL | the ARCFOUR stream cipher with | 91 | | | a 128-bit key | 92 +---------------+-----------------+---------------------------------+ 94 The current document updates the status of the "arcfour" ciphers in 95 the list of [RFC4253] Section 6.3 by moving it from OPTIONAL to MUST 96 NOT. 98 +----------+-----------+--------------------------------------------+ 99 | arcfour | MUST NOT | the ARCFOUR stream cipher with a 128-bit | 100 | | | key | 101 +----------+-----------+--------------------------------------------+ 103 [RFC4253] defines the "arcfour" ciphers with the text mentioned 104 below: 106 The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. 107 The Arcfour cipher is believed to be compatible with the RC4 cipher 108 [SCHNEIER]. Arcfour (and RC4) has problems with weak keys, and 109 should be used with caution. 111 The current document updates [RFC4253] Section 6.3 by replacing the 112 text above with the following text: 114 The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. 115 The Arcfour cipher is believed to be compatible with the RC4 cipher 116 [SCHNEIER]. Arcfour (and RC4) is steadily weakening in cryptographic 117 strength [RFC7465] [I-D.ietf-curdle-des-des-des-die-die-die], and 118 MUST NOT be used. 120 3. IANA Considerations 122 The IANA is requested to update the Encryption Algorithm Name 123 Registry of the Secure Shell (SSH) Protocol Parameters [IANA]. The 124 Registration procedure is IETF Review which is achieved by this 125 document. The registry should be updated as follows: 127 +-------------+------------------------------------+ 128 | Encryption | Algorithm Name Reference Note | 129 +-------------+------------------------------------+ 130 | arcfour | [RFC-TBD] | 131 | arcfour128 | [RFC-TBD] | 132 | arcfour256 | [RFC-TBD] | 133 +-------------+------------------------------------+ 135 Where TBD is the RFC number assigned to the document. 137 All drafts are required to have an IANA considerations section (see 138 Guidelines for Writing an IANA Considerations Section in RFCs 139 [RFC5226] for a guide). If the draft does not require IANA to do 140 anything, the section contains an explicit statement that this is the 141 case (as above). If there are no requirements for IANA, the section 142 will be removed during conversion into an RFC by the RFC Editor. 144 4. Acknowledgements 146 The authors would like to thank Daniel Migault 148 5. Security Considerations 150 This document only prohibits the use of RC4 in SSH, and introduces no 151 new security considerations. 153 6. References 155 6.1. Normative References 157 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 158 Requirement Levels", BCP 14, RFC 2119, 159 DOI 10.17487/RFC2119, March 1997, 160 . 162 [SCHNEIER] 163 Schneier, B., "Applied Cryptography Second Edition: 164 protocols algorithms and source in code in C", , 1996, 165 . 167 6.2. Informative References 169 [I-D.ietf-curdle-des-des-des-die-die-die] 170 Kaduk, B. and M. Short, "Deprecate 3DES and RC4 in 171 Kerberos", draft-ietf-curdle-des-des-des-die-die-die-05 172 (work in progress), September 2017. 174 [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) 175 Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253, 176 January 2006, . 178 [RFC4345] Harris, B., "Improved Arcfour Modes for the Secure Shell 179 (SSH) Transport Layer Protocol", RFC 4345, 180 DOI 10.17487/RFC4345, January 2006, 181 . 183 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 184 IANA Considerations Section in RFCs", RFC 5226, 185 DOI 10.17487/RFC5226, May 2008, 186 . 188 [RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, 189 DOI 10.17487/RFC7465, February 2015, 190 . 192 Authors' Addresses 194 Luis Camara 196 Email: luis.camara@live.com.pt 198 Loganaden Velvindron 199 Mauritius 201 Email: loganaden@gmail.com