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Versions: (draft-luis140219-curdle-rc4-die-die-die) 00 01 02 03 04 05 06 07 08 09 10 11 12

Internet Engineering Task Force                                L. Camara
Internet-Draft
Obsoletes: 4325 (if approved)                              L. Velvindron
Updates: 4253 (if approved)                               August 9, 2018
Intended status: Best Current Practice
Expires: February 10, 2019


                 Deprecating RC4 in Secure Shell (SSH)
                  draft-ietf-curdle-rc4-die-die-die-08

Abstract

   This document deprecates RC4 in Secure Shell (SSH).  Therefore, this
   document updates [RFC4253], and formally obsoletes and moves to
   Historic [RFC4345].

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
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   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 February 10, 2019.

Copyright Notice

   Copyright (c) 2018 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

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 the "arcfour-128" and "arcfour-256" ciphers for SSH.
   RC4 encryption is steadily weakening in cryptographic strength
   [RFC7465] [I-D.ietf-curdle-des-des-des-die-die-die], 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].

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                   |
   +---------------+-----------------+---------------------------------+

   The 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.




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   +----------+-----------+--------------------------------------------+
   | 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 believed to be compatible with the RC4 cipher
   [SCHNEIER].  Arcfour (and RC4) has problems with weak keys, and
   should be used with caution.

   The 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 believed to be compatible with the RC4 cipher
   [SCHNEIER].  Arcfour (and RC4) is steadily weakening in cryptographic
   strength [RFC7465] [I-D.ietf-curdle-des-des-des-die-die-die], 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.

   All drafts are required to have an IANA considerations section (see
   Guidelines for Writing an IANA Considerations Section in RFCs
   [RFC5226] for a guide).  If the draft does not require IANA to do
   anything, the section contains an explicit statement that this is the
   case (as above).  If there are no requirements for IANA, the section
   will be removed during conversion into an RFC by the RFC Editor.






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4.  Acknowledgements

   The authors would like to thank Daniel Migault

5.  Security Considerations

   This document only prohibits the use of RC4 in SSH, and introduces no
   new security considerations.

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>.

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

6.2.  Informative References

   [I-D.ietf-curdle-des-des-des-die-die-die]
              Kaduk, B. and M. Short, "Deprecate 3DES and RC4 in
              Kerberos", draft-ietf-curdle-des-des-des-die-die-die-05
              (work in progress), September 2017.

   [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>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

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




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Authors' Addresses

   Luis Camara

   Email: luis.camara@live.com.pt


   Loganaden Velvindron
   Mauritius

   Email: logan@hackers.mu








































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