Internet Engineering Task Force (IETF)                                L. Camara
Internet-Draft                                              L.Velvindron
Obsoletes: 4345 4325 (if approved)                              July 22, 2018                              L. Velvindron
Updates: 4253 (if approved)                               August 9, 2018
Intended Status: status: Best Current Practice
Expires: July 22, 2018 February 10, 2019

                 Deprecating RC4 in Secure Shell (SSH)
                  draft-ietf-curdle-rc4-die-die-die-07

[[RFC-Editor: please replace the second character of my surname by
U+00E2 when publishing as RFC in the header and in all pages.]]
                  draft-ietf-curdle-rc4-die-die-die-08

Abstract

   This document deprecates RC4 in Secure Shell (SSH).  Therefore, this
   document updates RFC 4253, [RFC4253], and formally obsoletes and moves to
   Historic RFC 4345. [RFC4345].

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on July 30, 2018. February 10, 2019.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2. Why obsolete and move to Historic RFC 4345
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   3.
   2.  Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . .   2
   4.
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  2
   5. Security Considerations   3
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . .  3
   6. Acknowlegdements  . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  3
   7.   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   7.1.   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . .  3
   7.2.   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . .  3
   8. Author's Address . . . . . . . . . . . . . . . . . . . . . . .  3   5

1.  Introduction

   The usage of RC4 suites ( also designated as arcfour ) for SSH are
   specified in [RFC 4253] [RFC4253] and [RFC 4345]. [RFC 4253] [RFC4345].  [RFC4253] specifies the
   allocation of the "arcfour" cipher for SSH. RFC 4345  [RFC4345] specifies and
   allocates the the "arcfour-128" and "arcfour-256" ciphers for SSH.
   RC4 encryption is steadily weakening in cryptographic strength [RFC7457]
   [draft-ietf-curdle-des-des-des-die-die-die-05]
   [RFC7465] [I-D.ietf-curdle-des-des-des-die-die-die], and the
   deprecation process should be begun for their use in SSH. 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
   BCP 14 [RFC2119, RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2. Why obsolete and move to Historic RFC 4345 RFC 4345 defines the "arcfour-128" and "arcfour-256" modes for SSH,
   and is obsoleted and moved to Historic as RC4 is broken [RFC7457].
   The modes defined by RFC 4345 MUST NOT be used.

3. 2119 [RFC2119].

2.  Updates to RFC 4253

   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 last sentence current document updates the status of the paragraph on RC4 (called "arcfour" ciphers in [RFC4253]) in
   the list of [RFC4253] Section 6.3 of by moving it from OPTIONAL to MUST
   NOT.

   +----------+-----------+--------------------------------------------+
   | 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 read: "Arcfour (also
   known as 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 broken [RFC7457] steadily weakening in cryptographic
   strength [RFC7465] [I-D.ietf-curdle-des-des-des-die-die-die], and therefore it
   MUST NOT be used."

   An informative reference to RFC 7457 is to be added to [RFC4253].

4. used.

3.  IANA Considerations

   The IANA may need is requested to take action as update the Encryption Algorithm Name
   Registry of the status for RC4 and 3DES
   algorithms for Secure Shell (SSH) Protocol Parameters [IANA].  The
   Registration procedure is IETF Review which is changed achieved by this document
   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 3, in RFCs
   [RFC5226] for a guide).  If the draft does not require IANA to do
   anything, the section contains an explicit statement that updates [RFC4253]). 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.

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. Acknowledgements

   Thanks to the numerous authors which have shown the weaknesses of
   RC4 throughout the years, and to the several people which have
   commented on the CURDLE mailing list about this document.

7.  References

7.1.

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, 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [SCHNEIER]
              Schneier, B., "Ambiguity of Uppercase vs Lowercase "Applied Cryptography Second Edition:
              protocols algorithms and source in
              RFC 2119 Key Words", BCP 14, RFC 8174, May 2017.

7.2. 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., T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
              January 2006.

   [RFC7457]  Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
              Known Attacks on 2006, <https://www.rfc-editor.org/info/rfc4253>.

   [RFC4345]  Harris, B., "Improved Arcfour Modes for the Secure Shell
              (SSH) Transport Layer Security (TLS) and
              Datagram TLS (DTLS)", Protocol", RFC 7457, February 2015.

   [[RFC-Editor: please replace the 'i' in my name by U+00ED and the
   first 'a' 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 the surname by U+00E2, as non-ASCII characters are
   allowed as per RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [RFC7465]  Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7997]]

8. Author's Address 7465,
              DOI 10.17487/RFC7465, February 2015,
              <https://www.rfc-editor.org/info/rfc7465>.

Authors' Addresses

   Luis Camara

   EMail: <luis.camara@live.com.pt>

   Email: luis.camara@live.com.pt

   Loganaden Velvindron

   EMail: <loganaden@gmail.com>
   Mauritius

   Email: logan@hackers.mu