Internet DRAFT - draft-ietf-curdle-rc4-die-die-die
draft-ietf-curdle-rc4-die-die-die
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
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This Internet-Draft will expire on May 28, 2020.
Copyright Notice
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document authors. All rights reserved.
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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 . . . . . . . . . . . . . . . . . . . . . . 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.
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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 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.
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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>.
Author's Address
Loganaden Velvindron
cyberstorm.mu
Mauritius
Email: logan@cyberstorm.mu
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