draft-ietf-curdle-rc4-die-die-die-18.txt   rfc8758.txt 
Internet Engineering Task Force L. Velvindron Internet Engineering Task Force (IETF) L. Velvindron
Internet-Draft cyberstorm.mu Request for Comments: 8758 cyberstorm.mu
Updates: 4253 (if approved) November 25, 2019 BCP: 227 April 2020
Intended status: Best Current Practice Updates: 4253
Expires: May 28, 2020 Category: Best Current Practice
ISSN: 2070-1721
Deprecating RC4 in Secure Shell (SSH) Deprecating RC4 in Secure Shell (SSH)
draft-ietf-curdle-rc4-die-die-die-18
Abstract Abstract
This document deprecates RC4 in Secure Shell (SSH). Therefore, this This document deprecates RC4 in Secure Shell (SSH). Therefore, this
document formally moves RFC4345 to historic status. document formally moves RFC 4345 to Historic status.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This memo documents an Internet Best Current Practice.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on May 28, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8758.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language
2. Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . 2 2. Updates to RFC 4253
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations
5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 5. References
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.1. Normative References
6.1. Normative References . . . . . . . . . . . . . . . . . . 4 5.2. Informative References
6.2. Informative References . . . . . . . . . . . . . . . . . 4 Acknowledgements
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 Author's Address
1. Introduction 1. Introduction
The usage of RC4 suites ( also designated as arcfour ) for SSH are The usage of RC4 suites (also designated as "arcfour") for SSH is
specified in [RFC4253] and [RFC4345]. [RFC4253] specifies the specified in [RFC4253] and [RFC4345]. [RFC4253] specifies the
allocation of the "arcfour" cipher for SSH. [RFC4345] specifies and allocation of the "arcfour" cipher for SSH. [RFC4345] specifies and
allocates the "arcfour128" and "arcfour256" ciphers for SSH. RC4 allocates the "arcfour128" and "arcfour256" ciphers for SSH. RC4
encryption has known weaknesses [RFC7465] [RFC8429], and the encryption has known weaknesses [RFC7465] [RFC8429]; therefore, this
deprecation process should be begun for their use in Secure Shell document starts the deprecation process for their use in Secure Shell
(SSH) [RFC4253]. Accordingly, [RFC4253] is updated to note the (SSH) [RFC4253]. Accordingly, [RFC4253] is updated to note the
deprecation of the RC4 ciphers and [RFC4345] is moved to Historic as deprecation of the RC4 ciphers, and [RFC4345] is moved to Historic
all ciphers it specifies MUST NOT be used. status, as all ciphers it specifies MUST NOT be used.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [RFC2119]RFC "OPTIONAL" in this document are to be interpreted as described in
8174 [RFC8174] when, and only when, they appear in all capitals, as BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
shown here. capitals, as shown here.
2. Updates to RFC 4253 2. Updates to RFC 4253
[RFC4253] is updated to prohibit arcfour's use in SSH. [RFC4253] [RFC4253] is updated to prohibit arcfour's use in SSH. [RFC4253],
allocates the "arcfour" cipher in Section 6.3 by defining a list of Section 6.3 allocates the "arcfour" cipher by defining a list of
defined ciphers where the "arcfour" cipher appears as optional as defined ciphers in which the "arcfour" cipher appears as optional, as
mentioned below: shown in Table 1.
+---------------+-----------------+---------------------------------+ +---------+----------+----------------------------------------------+
| arcfour | OPTIONAL | the ARCFOUR stream cipher with | | arcfour | OPTIONAL | the ARCFOUR stream cipher |
| | | a 128-bit key | | | | with a 128-bit key |
+---------------+-----------------+---------------------------------+ +---------+----------+----------------------------------------------+
This current document updates the status of the "arcfour" ciphers in Table 1
the list of [RFC4253] Section 6.3 by moving it from OPTIONAL to MUST
NOT.
+-----------+-----------+-------------------------------------------+ This document updates the status of the "arcfour" ciphers in the list
| arcfour | MUST NOT | the ARCFOUR stream cipher with a 128-bit | found in [RFC4253], Section 6.3 by moving it from OPTIONAL to MUST
| | | key | NOT.
+-----------+-----------+-------------------------------------------+
[RFC4253] defines the "arcfour" ciphers with the text mentioned +---------+----------+----------------------------------------------+
below: | arcfour | MUST NOT | the ARCFOUR stream cipher |
| | | with a 128-bit key |
+---------+----------+----------------------------------------------+
The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. Table 2
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 [RFC4253] defines the "arcfour" ciphers with the following text:
text above with the following text:
The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. | The "arcfour" cipher is the Arcfour stream cipher with 128-bit
The Arcfour cipher is compatible with the RC4 cipher [SCHNEIER]. | keys. The Arcfour cipher is believed to be compatible with the
Arcfour (and RC4) has known weaknesses [RFC7465] [RFC8429], and MUST | RC4 cipher [SCHNEIER]. Arcfour (and RC4) has problems with weak
NOT be used. | keys, and should be used with caution.
3. IANA Considerations This document updates [RFC4253], Section 6.3 by replacing the text
above with the following text:
The IANA is requested to update the Encryption Algorithm Name | The "arcfour" cipher is the Arcfour stream cipher with 128-bit
Registry of the Secure Shell (SSH) Protocol Parameters [IANA]. The | keys. The Arcfour cipher is compatible with the RC4 cipher
Registration procedure is IETF Review which is achieved by this | [SCHNEIER]. Arcfour (and RC4) has known weaknesses [RFC7465]
document. The registry should be updated as follows: | [RFC8429] and MUST NOT be used.
+------------------------------+---------------+---------+ 3. IANA Considerations
| Encryption Algorithm Name | Reference | Note |
+------------------------------+---------------+---------+
| arcfour | [RFC-TBD] | |
| arcfour128 | [RFC-TBD] | |
| arcfour256 | [RFC-TBD] | |
+------------------------------+---------------+---------+
Where TBD is the RFC number assigned to the document. The IANA has updated the "Encryption Algorithm Names" subregistry in
the "Secure Shell (SSH) Protocol Parameters" registry [IANA]. The
registration procedure is IETF review, which is achieved by this
document. The registry has been updated as follows:
4. Acknowledgements +---------------------------+-----------+----------+
| Encryption Algorithm Name | Reference | Note |
+===========================+===========+==========+
| arcfour | RFC 8758 | HISTORIC |
+---------------------------+-----------+----------+
| arcfour128 | RFC 8758 | HISTORIC |
+---------------------------+-----------+----------+
| arcfour256 | RFC 8758 | HISTORIC |
+---------------------------+-----------+----------+
The authors would like to thank Eric Rescorla, Daniel Migault and Table 3
Rich Salz.
5. Security Considerations 4. Security Considerations
This document only prohibits the use of RC4 in SSH, and introduces no This document only prohibits the use of RC4 in SSH; it introduces no
new security considerations. new security considerations.
6. References 5. References
6.1. Normative References 5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
6.2. Informative References 5.2. Informative References
[IANA] "Secure Shell (SSH) Protocol Parameters: Encryption [IANA] "Secure Shell (SSH) Protocol Parameters",
Algorithm Names", <https://www.iana.org/assignments/ssh- <https://www.iana.org/assignments/ssh-parameters>.
parameters/ssh-parameters.xhtml#ssh-parameters-17>.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253, Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <https://www.rfc-editor.org/info/rfc4253>. January 2006, <https://www.rfc-editor.org/info/rfc4253>.
[RFC4345] Harris, B., "Improved Arcfour Modes for the Secure Shell [RFC4345] Harris, B., "Improved Arcfour Modes for the Secure Shell
(SSH) Transport Layer Protocol", RFC 4345, (SSH) Transport Layer Protocol", RFC 4345,
DOI 10.17487/RFC4345, January 2006, DOI 10.17487/RFC4345, January 2006,
<https://www.rfc-editor.org/info/rfc4345>. <https://www.rfc-editor.org/info/rfc4345>.
[RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, [RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465,
DOI 10.17487/RFC7465, February 2015, DOI 10.17487/RFC7465, February 2015,
<https://www.rfc-editor.org/info/rfc7465>. <https://www.rfc-editor.org/info/rfc7465>.
[RFC8429] Kaduk, B. and M. Short, "Deprecate Triple-DES (3DES) and [RFC8429] Kaduk, B. and M. Short, "Deprecate Triple-DES (3DES) and
RC4 in Kerberos", BCP 218, RFC 8429, DOI 10.17487/RFC8429, RC4 in Kerberos", BCP 218, RFC 8429, DOI 10.17487/RFC8429,
October 2018, <https://www.rfc-editor.org/info/rfc8429>. October 2018, <https://www.rfc-editor.org/info/rfc8429>.
[SCHNEIER] [SCHNEIER] Schneier, B., "Applied Cryptography Second Edition:
Schneier, B., "Applied Cryptography Second Edition: Protocols, Algorithms, and Source in Code in C", John
protocols algorithms and source in code in C", , 1996, Wiley and Sons New York, NY, 1996.
<SCHNEIER>.
Acknowledgements
The author would like to thank Eric Rescorla, Daniel Migault, and
Rich Salz.
Author's Address Author's Address
Loganaden Velvindron Loganaden Velvindron
cyberstorm.mu cyberstorm.mu
Mauritius Mauritius
Email: logan@cyberstorm.mu Email: logan@cyberstorm.mu
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