Internet Engineering Task Force L. Velvindron Internet-Draft cyberstorm.mu Updates: 4253 (if approved) November 25, 2019 Intended status: Best Current Practice Expires: May 28, 2020 Deprecating RC4 in Secure Shell (SSH) draft-ietf-curdle-rc4-die-die-die-18 Abstract This document deprecates RC4 in Secure Shell (SSH). Therefore, this document formally moves RFC4345 to historic status. 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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 May 28, 2020. Copyright Notice Copyright (c) 2019 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 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Velvindron Expires May 28, 2020 [Page 1] Internet-Draft draft-ietf-curdle-rc4-die-die-die November 2019 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . 2 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 6.2. Informative References . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction The usage of RC4 suites ( also designated as arcfour ) for SSH are specified in [RFC4253] and [RFC4345]. [RFC4253] specifies the allocation of the "arcfour" cipher for SSH. [RFC4345] specifies and allocates the "arcfour128" and "arcfour256" ciphers for SSH. RC4 encryption has known weaknesses [RFC7465] [RFC8429], and the deprecation process should be begun for their use in Secure Shell (SSH) [RFC4253]. Accordingly, [RFC4253] is updated to note the deprecation of the RC4 ciphers and [RFC4345] is moved to Historic as all ciphers it specifies MUST NOT be used. 1.1. Requirements Language 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 RFC 2119 [RFC2119]RFC 8174 [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Updates to RFC 4253 [RFC4253] is updated to prohibit arcfour's use in SSH. [RFC4253] allocates the "arcfour" cipher in Section 6.3 by defining a list of defined ciphers where the "arcfour" cipher appears as optional as mentioned below: +---------------+-----------------+---------------------------------+ | arcfour | OPTIONAL | the ARCFOUR stream cipher with | | | | a 128-bit key | +---------------+-----------------+---------------------------------+ This current document updates the status of the "arcfour" ciphers in the list of [RFC4253] Section 6.3 by moving it from OPTIONAL to MUST NOT. Velvindron Expires May 28, 2020 [Page 2] Internet-Draft draft-ietf-curdle-rc4-die-die-die November 2019 +-----------+-----------+-------------------------------------------+ | arcfour | MUST NOT | the ARCFOUR stream cipher with a 128-bit | | | | key | +-----------+-----------+-------------------------------------------+ [RFC4253] defines the "arcfour" ciphers with the text mentioned below: The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. The Arcfour cipher is compatible with the RC4 cipher [SCHNEIER]. Arcfour (and RC4) has problems with weak keys, and should be used with caution. This current document updates [RFC4253] Section 6.3 by replacing the text above with the following text: The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. The Arcfour cipher is compatible with the RC4 cipher [SCHNEIER]. Arcfour (and RC4) has known weaknesses [RFC7465] [RFC8429], and MUST NOT be used. 3. IANA Considerations The IANA is requested to update the Encryption Algorithm Name Registry of the Secure Shell (SSH) Protocol Parameters [IANA]. The Registration procedure is IETF Review which is achieved by this document. The registry should be updated as follows: +------------------------------+---------------+---------+ | Encryption Algorithm Name | Reference | Note | +------------------------------+---------------+---------+ | arcfour | [RFC-TBD] | | | arcfour128 | [RFC-TBD] | | | arcfour256 | [RFC-TBD] | | +------------------------------+---------------+---------+ Where TBD is the RFC number assigned to the document. 4. Acknowledgements The authors would like to thank Eric Rescorla, Daniel Migault and Rich Salz. 5. Security Considerations This document only prohibits the use of RC4 in SSH, and introduces no new security considerations. Velvindron Expires May 28, 2020 [Page 3] Internet-Draft draft-ietf-curdle-rc4-die-die-die November 2019 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 6.2. Informative References [IANA] "Secure Shell (SSH) Protocol Parameters: Encryption Algorithm Names", . [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253, January 2006, . [RFC4345] Harris, B., "Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol", RFC 4345, DOI 10.17487/RFC4345, January 2006, . [RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, DOI 10.17487/RFC7465, February 2015, . [RFC8429] Kaduk, B. and M. Short, "Deprecate Triple-DES (3DES) and RC4 in Kerberos", BCP 218, RFC 8429, DOI 10.17487/RFC8429, October 2018, . [SCHNEIER] Schneier, B., "Applied Cryptography Second Edition: protocols algorithms and source in code in C", , 1996, . Author's Address Loganaden Velvindron cyberstorm.mu Mauritius Email: logan@cyberstorm.mu Velvindron Expires May 28, 2020 [Page 4]