



Internet Engineering Task Force                                L. Camara
Internet-Draft
Updates: 4253 (if approved)                                L. Velvindron
Intended status: Best Current Practice                     cyberstorm.mu
Expires: April 23, 2020                                 October 21, 2019


                 Deprecating RC4 in Secure Shell (SSH)
                  draft-ietf-curdle-rc4-die-die-die-17

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 April 23, 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.





Camara & Velvindron      Expires April 23, 2020                 [Page 1]

Internet-Draft      draft-ietf-curdle-rc4-die-die-die       October 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
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   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.



Camara & Velvindron      Expires April 23, 2020                 [Page 2]

Internet-Draft      draft-ietf-curdle-rc4-die-die-die       October 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.




Camara & Velvindron      Expires April 23, 2020                 [Page 3]

Internet-Draft      draft-ietf-curdle-rc4-die-die-die       October 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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2.  Informative References

   [IANA]     "Secure Shell (SSH) Protocol Parameters: Encryption
              Algorithm Names", <https://www.iana.org/assignments/ssh-
              parameters/ssh-parameters.xhtml#ssh-parameters-17>.

   [RFC4253]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
              January 2006, <https://www.rfc-editor.org/info/rfc4253>.

   [RFC4345]  Harris, B., "Improved Arcfour Modes for the Secure Shell
              (SSH) Transport Layer Protocol", RFC 4345,
              DOI 10.17487/RFC4345, January 2006,
              <https://www.rfc-editor.org/info/rfc4345>.

   [RFC7465]  Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465,
              DOI 10.17487/RFC7465, February 2015,
              <https://www.rfc-editor.org/info/rfc7465>.

   [RFC8429]  Kaduk, B. and M. Short, "Deprecate Triple-DES (3DES) and
              RC4 in Kerberos", BCP 218, RFC 8429, DOI 10.17487/RFC8429,
              October 2018, <https://www.rfc-editor.org/info/rfc8429>.

   [SCHNEIER]
              Schneier, B., "Applied Cryptography Second Edition:
              protocols algorithms and source in code in C",  , 1996,
              <SCHNEIER>.

Authors' Addresses

   Luis Camara

   Email: luis.camara@live.com.pt





Camara & Velvindron      Expires April 23, 2020                 [Page 4]

Internet-Draft      draft-ietf-curdle-rc4-die-die-die       October 2019


   Loganaden Velvindron
   cyberstorm.mu
   Mauritius

   Email: logan@cyberstorm.mu














































Camara & Velvindron      Expires April 23, 2020                 [Page 5]
