draft-ietf-curdle-rc4-die-die-die-00.txt   draft-ietf-curdle-rc4-die-die-die-01.txt 
Internet Engineering Task Force (IETF) L. Camara Internet Engineering Task Force (IETF) L. Camara
Internet-Draft July 3, 2017 Internet-Draft August 1, 2017
Obsoletes: 3078, 3079, 4345, 4757, 6229 Obsoletes: 4345
Updates: 2118, 3501, 3961, 4120, 4253, 6150 Updates: 3501, 4253, 6649, 6733
Updates: 6649, 6733, 7457, 7905, xxxx
Intended Status: Best Current Practice Intended Status: Best Current Practice
Expires: January 4, 2018 Expires: February 2, 2018
Deprecating RC4 in all IETF Protocols Deprecating RC4 in all IETF Protocols
draft-ietf-curdle-rc4-die-die-die-00 draft-ietf-curdle-rc4-die-die-die-01
[[RFC-Editor: Please replace all instances of xxxx in this document with [[RFC-Editor: Please replace all instances of xxxx in this document with
the RFC number of draft-ietf-curdle-des-des-des-die-die-die.]] the RFC number of draft-ietf-curdle-des-des-des-die-die-die.]]
[[RFC-Editor: please replace the second character of my surname by [[RFC-Editor: please replace the second character of my surname by
U+00E2 when publishing as RFC in the header and in all pages. U+00E2 when publishing as RFC in the header and in all pages.
Non-ASCII characters are allowed in RFCs as per RFC 7997.]] Non-ASCII characters are allowed in RFCs as per RFC 7997.]]
Abstract Abstract
RC4 is extremely weak as shown by RFC 6649 and RFC 7457, is RC4 is extremely weak as shown by RFC 6649 and RFC 7457, is
prohibited in TLS by RFC 7465, is prohibited in Kerberos by RFC xxxx prohibited in TLS by RFC 7465, is prohibited in Kerberos by RFC xxxx
and it needs to be prohibited in all IETF protocols. Documents that and it needs to be prohibited in all IETF protocols. This document
provide technology that can only use RC4 are obsoleted by this obsoletes RFC 4345 "Improved Arcfour Modes for the Secure Shell (SSH)
document, so this document obsoletes and moves to Historic RFC 3078 Transport Layer Protocol" (note Arcfour and RC4 are synonymous).
"Microsoft Point-to-Point Encryption (MPPE) Protocol" (only supports RFC 3501, RFC 4253, RFC 6649 and RFC 6733 are updated to note the
RC4, RFC 3079 that is also part of that protocol is also obsoleted), deprecation of RC4 in all IETF protocols.
RFC 4345 "Improved Arcfour Modes for the Secure Shell (SSH) Transport
Layer Protocol" (note Arcfour and RC4 are synonymous), RFC 4757 "The
RC4-HMAC Kerberos Encryption Types Used by Microsoft Windows" (only
supports RC4) and RFC 6229 "Test Vectors for the Stream Cipher RC4"
(provides test vectors for historic cryptography). RFC 2118,
RFC 3501, RFC 3961, RFC 4120, RFC 4253, RFC 6150, RFC 6649, RFC 6733,
RFC 7457, RFC 7905 and RFC xxxx are updated to note the deprecation
of RC4 in all IETF protocols. (Please do not confuse RFC 4757 with
RFC 7457.)
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
skipping to change at page 2, line 23 skipping to change at page 2, line 18
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Why obsolete those RFCs and move them to Historic . . . . . . . 3 2. Why obsolete RFC 4345 . . . . . . . . . . . . . . . . . . . . . 2
3. Updates to RFC 2118 . . . . . . . . . . . . . . . . . . . . . . 3 3. Updates to RFC 3501 . . . . . . . . . . . . . . . . . . . . . . 3
4. Updates to RFC 3501 . . . . . . . . . . . . . . . . . . . . . . 3 4. Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . . 3
5. Updates to RFC 3961 . . . . . . . . . . . . . . . . . . . . . . 4 5. Updates to RFC 6649 . . . . . . . . . . . . . . . . . . . . . . 4
6. Updates to RFC 4120 . . . . . . . . . . . . . . . . . . . . . . 4 6. Updates to RFC 6733 . . . . . . . . . . . . . . . . . . . . . . 4
7. Updates to RFC 4253 . . . . . . . . . . . . . . . . . . . . . . 4 7. Action to be taken . . . . . . . . . . . . . . . . . . . . . . 5
8. Updates to RFC 6150 . . . . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
9. Updates to RFC 6649 . . . . . . . . . . . . . . . . . . . . . . 5 9. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
10. Updates to RFC 6733 . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowlegdements . . . . . . . . . . . . . . . . . . . . . . . 5
11. Updates to RFC 7457 . . . . . . . . . . . . . . . . . . . . . 7 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
12. Updates to RFC 7465 . . . . . . . . . . . . . . . . . . . . . 7 11.1. Normative References . . . . . . . . . . . . . . . . . . . . 6
13. Updates to RFC 7905 . . . . . . . . . . . . . . . . . . . . . 7 11.2. Informative References . . . . . . . . . . . . . . . . . . . 6
14. Updates to RFC xxxx . . . . . . . . . . . . . . . . . . . . . 8 12. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
15. Action to be taken . . . . . . . . . . . . . . . . . . . . . . 8 Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . . 8
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
17. Security Considerations . . . . . . . . . . . . . . . . . . . 9
18. Acknowlegdements . . . . . . . . . . . . . . . . . . . . . . . 9
19. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
19.1. Normative References . . . . . . . . . . . . . . . . . . . . 9
19.2. Informative References . . . . . . . . . . . . . . . . . . . 10
20. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix A. Status of Updated Documents as of 2017-06-17 . . . . . 11
Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
RC4 is extremely weak [RFC6649, RFC7457, RFCxxxx] and this document RC4 is extremely weak [RFC6649] [RFC7457] [RFCxxxx] and this document
deprecates its use in all IETF protocols, including Kerberos and deprecates its use in all IETF protocols, including Kerberos and
Secure Shell (SSH). The reasons for obsoleting RFC 3078, RFC 3079, Secure Shell (SSH). The reasons for obsoleting RFC 4345 are discussed
RFC 4345 and RFC 4757 and moving them to Historic are discussed in in Section 2. The updates to RFC 3501, RFC 4253, RFC 6649 and RFC
Section 2. The updates to RFC 2118, RFC 3501, RFC 3961, RFC 4120, RFC 6733 and the reasons for doing them are specified in sections 3,
RFC 4253, RFC 6150, RFC 6649, RFC 6733, RFC 7457, RFC 7905 and 4, 5 and 6, respectively.
RFC xxxx and the reasons for doing them are specified in sections 3,
4, 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14, respectively. The status of
the updated RFCs as of the writing of this document is available in
Appendix A.
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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in document are to be interpreted as described in
BCP 14 [RFC2119, RFC8174]. BCP 14 [RFC2119, RFC8174].
2. Why obsolete those RFCs and move them to Historic 2. Why obsolete RFC 4345
RFC 3078 is no longer used by supported Microsoft Windows versions
and is moved to Historic and obsoleted by this document as it only
supports RC4 for encryption. RFC 2118 is updated to note the
moving of RFC 3078 (that updated RFC 2118) to Historic and its
obsoleting. RFC 3079, that is effectively part of RFC 3078, is also
moved to Historic as it only supports RC4 for encryption.
RFC 4345 defines the "arcfour-128" and "arcfour-256" modes for Secure RFC 4345 defines the "arcfour-128" and "arcfour-256" modes for Secure
Shell (SSH), and is moved to Historic as RC4 is extremely Shell (SSH), and is moved to Historic as RC4 is extremely
weak [RFC6649, RFC7457, RFCxxxx] and there is research that is at weak [RFC6649, RFC7457, RFCxxxx] and there is research that is at
least 5 years old that totally breaks all practical usage of least 5 years old that totally breaks all practical usage of
RC4 [RFC6649]. RC4 [RFC6649].
RFC 4757 is obsoleted and moved to Historic as it is no longer used 3. Updates to RFC 3501
by supported Microsoft Windows versions (support for Windows XP ended
8 April 2014, any unofficial support for officially unsupported
Microsoft Windows versions will certainly remove RC4) and specifies
RC4-HMAC as used by Microsoft Windows in Kerberos, that should have
been obsoleted, not updated, by RFC 6649. RFC xxxx also obsoletes
RFC 4757. Additionally, MD4 is extremely weak and not
one-way [RFC6150] and this is another reason to move RFC 4757 to
Historic, as well as the myriads of other reasons specified
in [RFC6150].
RFC 6229 provides test vectors for RC4 and is obsoleted and moved to
Historic by this document as RC4 is deprecated in all IETF protocols.
3. Updates to RFC 2118
RFC 2118 is updated to note the obsoleting of RFC 3078 and the
moving of RFC 3078 to Historic (see Section 2).
4. Updates to RFC 3501
In Section 11.1 of [RFC3501], it is stated that:
"""
IMAP client and server implementations MUST implement the
TLS_RSA_WITH_RC4_128_MD5 {TLS} cipher suite, and SHOULD implement the
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA {TLS} cipher suite. This is
important as it assures that any two compliant implementations can be
configured to interoperate. All other cipher suites are OPTIONAL.
Note that this is a change from section 2.1 of {IMAP_TLS}.
"""
[[References were replaced with curly braces to avoid nits. When
publishing, revert back to references.]]
The above paragraph of [RFC3501] required that implementations of The second paragraph of [RFC3501] required that implementations of
IMAP clients and servers implement a RC4 cipher suite in TLS IMAP clients and servers implement a RC4 cipher suite in TLS
(contradicts [RFC7465]) and recommends implementing a weak cipher (contradicts [RFC7465]) and recommends implementing a weak cipher
suite (DSA is not recommended by some sources and 3DES is used in suite (3DES is used in the suite). Unfortunately, at the time of
the suite). Unfortunately, at the time of writing of RFC 3501, writing of RFC 3501, AES cipher suites were extremely new (the first
AES cipher suites were extremely new (the first AES cipher suites AES cipher suites were defined in RFC 3268, published in June 2002),
were defined in RFC 3268, published in June 2002), less than 1 year less than 1 year old and the strongest choice they have come up with
old and the strongest choice they have come up with at the time was at the time was TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA.
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA.
As the document is over 14 years old, the above paragraph of [RFC3501] As the document is over 14 years old, the second paragraph of
is replaced with the following paragraph: Section 11.1 of [RFC3501] is replaced with the following paragraph:
""" """
IMAP client and server implementations were formerly required to IMAP client and server implementations were formerly required to
implement TLS_RSA_WITH_RC4_128_MD5 {TLS}, an extremely weak cipher implement TLS_RSA_WITH_RC4_128_MD5 {TLS}, an extremely weak cipher
suite [RFC6151, RFC6649, RFC7457, RFCxxxx, RFCyyyy] that TLS clients suite [RFC6151] [RFC6649] [RFC7457] [RFCxxxx] [RFCyyyy] that TLS
MUST NOT implement per [RFC7465]. Compatibility requirements were clients MUST NOT implement per [RFC7465]. Compatibility requirements
removed in the grounds of security, and all clients and servers were removed in the grounds of security, and all clients and servers
SHOULD implement TLS 1.2 {TLS} and the SHOULD implement TLS 1.2 {TLS} and the
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 {TLS} cipher suite. TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 {TLS} cipher suite.
""" """
The TLS reference in [RFC3501] should be replaced with a reference to The TLS reference in [RFC3501] should be replaced with a reference to
RFC 5246, and references to RFC 6151, RFC 6649, RFC 7457, RFC 7465, RFC 5246, and references to RFC 6151, RFC 6649, RFC 7457, RFC 7465,
RFC xxxx and this document (as RFC yyyy) should be added. RFC xxxx and this document (as RFC yyyy) should be added.
5. Updates to RFC 3961 4. Updates to RFC 4253
RFC 3961 is updated to note the deprecation of rc4-hmac and
rc4-hmac-exp (referred to in Section 8 of [RFC3961]). rc4-hmac is
NOT RECOMMENDED by [RFCxxxx] and rc4-hmac-exp is NOT RECOMMENDED
by [RFC6649].
6. Updates to RFC 4120
RFC 4120 is updated to note the deprecation of rc4-hmac and
rc4-hmac-exp.
7. Updates to RFC 4253
RFC 4253 is updated to note the deprecation of arcfour and 3des-cbc. RFC 4253 is updated to note the deprecation of arcfour and 3des-cbc.
This document changes "OPTIONAL" to "NOT RECOMMENDED" for arcfour and This document changes "OPTIONAL" to "NOT RECOMMENDED" for arcfour and
"REQUIRED" to "OPTIONAL" for 3des-cbc in the table of "REQUIRED" to "OPTIONAL" for 3des-cbc in the table of
Section 6.3 of [RFC4253] as 3DES is weak and maintaining the Section 6.3 of [RFC4253] as 3DES is weak and maintaining the
requirement will compromise systems. [RFC4253] was published in 2006, requirement will compromise systems. [RFC4253] was published in 2006,
11 years ago, and states that """At some future time, it is expected 11 years ago, and states that """At some future time, it is expected
that another algorithm, one with better strength, will become so that another algorithm, one with better strength, will become so
prevalent and ubiquitous that the use of "3des-cbc" will be prevalent and ubiquitous that the use of "3des-cbc" will be
deprecated by another STANDARDS ACTION.""" deprecated by another STANDARDS ACTION."""
The "future time" referred to by [RFC4253] is set to 2017, the The "future time" referred to by [RFC4253] is set to 2017, the
"STANDARDS ACTION" is set to the publication of this document and "STANDARDS ACTION" is set to the publication of this document and
the "algorithm" is set to the Advanced Encryption Standard (AES), as the "algorithm" is set to the Advanced Encryption Standard (AES), as
AES is ubiquitous in Kerberos implementations (see Section 11). AES is ubiquitous in Kerberos implementations (see Section 11).
The paragraph on RC4 (called "arcfour" in [RFC4253]) in The last sentence of the paragraph on RC4 (called "arcfour"
Section 6.3 of [RFC4253] currently reads: in [RFC4253]) in Section 6.3 of [RFC4253] should read: "Arcfour (and
""" RC4) are extremely weak [RFC6649] [RFC7457] [RFCxxxx] [RFCyyyy] and
The "arcfour" cipher is the Arcfour stream cipher with 128-bit keys. therefore their use is NOT RECOMMENDED."
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.
"""
It should read:
"""
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) are extremely weak [RFC6649, RFC7457,
RFCxxxx, RFCyyyy] and therefore their use is NOT RECOMMENDED.
"""
References to RFC 6649, RFC 7457, RFC xxxx and this document (the References to RFC 6649, RFC 7457, RFC xxxx and this document (the
reference to this document is RFCyyyy in the above paragraph) should reference to this document is RFCyyyy in the above paragraph) should
be added to Section 6.3 of [RFC4253]. be added to Section 6.3 of [RFC4253].
8. Updates to RFC 6150 5. Updates to RFC 6649
RFC 6150 moves MD4 to Historic. Note the RFC contains a typo: "MD2"
should be "MD4". RFC 6150 references RFC 4757, obsoleted by this
document, as using MD4. The expression "with the one exception of
Microsoft's use of MD4 as part of RC4-HMAC in Windows,", as well as
all expressions indicating algorithms using RC4 are a problem to the
deprecation of MD4, should be removed from Section 4 of [RFC6150].
9. Updates to RFC 6649
RFC 6649, also known as BCP 179, deprecates DES, RC4-HMAC-EXP and RFC 6649, also known as BCP 179, deprecates DES, RC4-HMAC-EXP and
other weak cryptography in Kerberos. It is updated to note the other weak cryptography in Kerberos. It is updated to note the
deprecation of rc4-hmac and the deprecation of RC4 in all IETF deprecation of rc4-hmac and the deprecation of RC4 in all IETF
protocols. protocols.
The security considerations of [RFC6649] (Section 6 of [RFC6649]) The security considerations of [RFC6649] (Section 6 of [RFC6649])
read, in their last paragraph: read, in their last paragraph:
""" """
skipping to change at page 6, line 22 skipping to change at page 4, line 32
now. The main reason to not actively discourage the use of RC4-HMAC now. The main reason to not actively discourage the use of RC4-HMAC
is that it is the only encryption type that interoperates with older is that it is the only encryption type that interoperates with older
versions of Microsoft Windows once DES and RC4-HMAC-EXP are removed. versions of Microsoft Windows once DES and RC4-HMAC-EXP are removed.
These older versions of Microsoft Windows will likely be in use until These older versions of Microsoft Windows will likely be in use until
at least 2015. at least 2015.
""" """
This is updated to note that Windows XP is without official support This is updated to note that Windows XP is without official support
for 3 years (support for Windows XP ended 8 April 2014). for 3 years (support for Windows XP ended 8 April 2014).
An important quote from [RFC6649] (Section 6 of [RFC6649]): 6. Updates to RFC 6733
"""
Removing support for single DES improves security because DES is
considered to be insecure. RC4-HMAC-EXP has a similarly inadequate
key size, so removing support for it also improves security.
"""
10. Updates to RFC 6733
Section 13.1. of [RFC6733] currently reads:
"""
Diameter nodes MUST be able to negotiate the following TLS/TCP and
DTLS/SCTP cipher suites:
TLS_RSA_WITH_RC4_128_MD5
TLS_RSA_WITH_RC4_128_SHA
TLS_RSA_WITH_3DES_EDE_CBC_SHA
Diameter nodes SHOULD be able to negotiate the following TLS/TCP and
DTLS/SCTP cipher suite:
TLS_RSA_WITH_AES_128_CBC_SHA
Note that it is quite possible that support for the
TLS_RSA_WITH_AES_128_CBC_SHA cipher suite will be REQUIRED at some
future date. Diameter nodes MAY negotiate other TLS/TCP and DTLS/
SCTP cipher suites.
"""
The above paragraphs required that clients implement two RC4 cipher Section 13.1 of [RFC6733] required that clients implement two RC4
suites and a 3DES cipher suite (but recommends implementing an AES cipher suites and a 3DES cipher suite (but recommends implementing an
cipher suite). AES cipher suite).
RFC 6733 was published in October 2012, and the above paragraphs RFC 6733 was published in October 2012, and all paragraphs but the
of [RFC6733] are to be replaced with: last of Section 13.1 of [RFC6733] are to be replaced with:
""" """
Diameter nodes were formerly required to implement insecure RC4 Diameter nodes were formerly required to implement insecure RC4
cipher suites and weak 3DES cipher suites. RC4 MUST NOT be used cipher suites and weak 3DES cipher suites. RC4 MUST NOT be used
because it is prohibited by RFC 7465. because it is prohibited by RFC 7465.
Diameter nodes MUST support at least one of the following cipher Diameter nodes MUST support at least one of the following cipher
suites: suites:
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
skipping to change at page 7, line 37 skipping to change at page 5, line 19
TLS_RSA_WITH_AES_128_CBC_SHA was not chosen to be absolutely required TLS_RSA_WITH_AES_128_CBC_SHA was not chosen to be absolutely required
as Diameter nodes may require all connections to use forward secrecy as Diameter nodes may require all connections to use forward secrecy
by only implementing cipher suites with forward secrecy. by only implementing cipher suites with forward secrecy.
TLS_RSA_WITH_AES_128_CBC_SHA is not a forward secrecy cipher suite TLS_RSA_WITH_AES_128_CBC_SHA is not a forward secrecy cipher suite
because all connections can be decrypted once the private RSA key is because all connections can be decrypted once the private RSA key is
known by an attacker. known by an attacker.
""" """
Several choices were given because of patent concerns with Elliptic Several choices were given because of patent concerns with Elliptic
Curve Cryptography (ECC) and problems of older implementations with Curve Cryptography (ECC) and problems of older implementations with
ECC and GCM cipher suites. ECC and GCM cipher suites, as well as problems of new implementations
with DHE, as they may not support DHE because ECDHE is more
11. Updates to RFC 7457 efficient.
RFC 7457, an Informational RFC describing attacks against Transport
Layer Security (TLS) and Datagram Transport Layer Security (DTLS), is
updated to note the deprecation of RC4 in all IETF protocols.
12. Updates to RFC 7465
RFC 7465 prohibits RC4 cipher suites in Transport Layer Security
(TLS) and is updated to note the deprecation of RC4 in all IETF
protocols.
13. Updates to RFC 7905
RFC 7905, describing the ChaCha20-Poly1305 stream cipher to replace
RC4 in Transport Layer Security (TLS), is updated to note the
deprecation of RC4 in all IETF protocols, including TLS. [RFC7465],
that prohibited RC4 cipher suites, did not update RFC 7905, so this
document will do so.
14. Updates to RFC xxxx
RFC xxxx deprecates 3DES and RC4 in Kerberos, obsoletes RFC 4757 and
updates RFC 3961, and is updated by this document to note the
moving of RC4 RFCs (RFC 4345 and RFC 6229) and Microsoft technology
dependent on RC4 (RFC 3078 and RFC 4757).
An important quote from [RFCxxxx] (Section 5.4 of [RFCxxxx]):
"""
Fortuntately, modern (i.e., supported) Kerberos implementations
support a secure alternative to RC4, in the form of AES. Windows has
supported AES since 2007-2008 with the release of Windows Vista and
Server 2008, respectively; MIT Kerberos [MITKRB5] has fully supported
AES (including the GSSAPI mechanism) since 2004 with the release of
version 1.3.2; Heimdal [HEIMDAL] has fully supported AES since 2005
with the release of version 0.7. Though there may still be issues
running ten-year-old unsupported software in mixed environments with
new software, issues of that sort seem unlikely to be unique to
Kerberos, and the aministrators of such environments are expected to
be capable of devising workarounds.
"""
(note the quote contains typos: "Fortuntately" and "aministrators")
15. Action to be taken 7. Action to be taken
RC4 MUST NOT be used in new implementations of IETF protocols, and RC4 MUST NOT be used in new implementations of IETF protocols, and
RC4 MUST be eliminated as fast as possible from the existing Internet RC4 MUST be eliminated as fast as possible from the existing Internet
infrastructure, as RC4 is extremely weak [RFC6649, RFC7457, RFCxxxx]. infrastructure, as RC4 is insecure [RFC6649] [RFC7457] [RFCxxxx].
New RFCs MAY use the phrase "RC4 is extremely weak [RFC6649, RFC7457,
RFCxxxx]" with references to RFC 6649, RFC 7457 and RFC xxxx. Whether
the references to these documents is normative or informative is
determined by BCP 9 and BCP 97, whose relevant documents for this
purpose are RFC 2026, RFC 3967, RFC 4897, RFC 6410 and RFC 8067.
Microsoft Corporation SHOULD take action to eradicate RC4 in all Microsoft Corporation SHOULD take action to eradicate RC4 in all
its software and systems. its software and systems.
New IETF protocols MUST NOT allow RC4, and new versions of existing New IETF protocols MUST NOT allow RC4, and new versions of existing
IETF protocols MUST either not allow RC4 or recommend not to use RC4 IETF protocols MUST either not allow RC4 or recommend not to use RC4
(for example, using "NOT RECOMMENDED" or "SHOULD NOT"). (for example, using "NOT RECOMMENDED" or "SHOULD NOT").
16. IANA Considerations 8. IANA Considerations
IANA may need to take action as the status for RC4 and 3DES IANA may need to take action as the status for RC4 and 3DES
algorithms for Secure Shell (SSH) is changed by this document algorithms for Secure Shell (SSH) is changed by this document
(see Section 6, that updates [RFC4253]). (see Section 6, that updates [RFC4253]).
17. Security Considerations 9. Security Considerations
This document deprecates RC4, that is obsolete cryptography, and This document deprecates RC4, that is obsolete cryptography, and
several attacks that render it useless have been published [RFC6649]. several attacks that render it useless have been published [RFC6649].
Refer to Section 5 of [RFCxxxx] for further security considerations. Refer to Section 5 of [RFCxxxx] for further security considerations.
18. Acknowledgements 10. Acknowledgements
[[RFC-Editor: When possible, add native names according to the [[RFC-Editor: When possible, add native names according to the
conventions of RFC 7997.]] conventions of RFC 7997.]]
Thanks to the following people for writing reference material: Thanks to the following people for writing reference material:
* Sean Turner and Lily Chen for writing RFC 6151, that contains * Sean Turner and Lily Chen for writing RFC 6151, that contains
updated security considerations for MD5 and HMAC-MD5. updated security considerations for MD5 and HMAC-MD5.
* Love Hornquist Astrand and Tom Yu for writing RFC 6649, that * Love Hornquist Astrand and Tom Yu for writing RFC 6649, that
skipping to change at page 9, line 43 skipping to change at page 6, line 30
Also thanks to SSL Labs for capping server grades to B (RC4 only used Also thanks to SSL Labs for capping server grades to B (RC4 only used
with older protocols) and C (RC4 used with modern protocols) when with older protocols) and C (RC4 used with modern protocols) when
servers support RC4, and flagging cipher suites and clients using RC4 servers support RC4, and flagging cipher suites and clients using RC4
with a red colour (for INSECURE and RC4). You can test any server at with a red colour (for INSECURE and RC4). You can test any server at
<https://www.ssllabs.com/ssltest/>. <https://www.ssllabs.com/ssltest/>.
Refer to the acknowledgements section of RFC 6649, RFC 7457 and Refer to the acknowledgements section of RFC 6649, RFC 7457 and
RFC xxxx for further acknowledgements. RFC xxxx for further acknowledgements.
19. References 11. References
19.1. Normative References 11.1. 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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6649] Hornquist Astrand, L. and T. Yu, "Deprecate DES, RC4-HMAC- [RFC6649] Hornquist Astrand, L. and T. Yu, "Deprecate DES, RC4-HMAC-
EXP, and Other Weak Cryptographic Algorithms in Kerberos", EXP, and Other Weak Cryptographic Algorithms in Kerberos",
BCP 179, RFC 6649, July 2012. BCP 179, RFC 6649, July 2012.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174, May 2017. RFC 2119 Key Words", BCP 14, RFC 8174, May 2017.
[RFCxxxx] Kaduk, B., and M. Short, "Deprecate 3DES and RC4 in [RFCxxxx] Kaduk, B., and M. Short, "Deprecate 3DES and RC4 in
Kerberos", draft-ietf-curdle-des-des-des-die-die-die-03, Kerberos", draft-ietf-curdle-des-des-des-die-die-die-04,
Work in Progress. Work in Progress.
19.2. Informative References 11.2. Informative References
[HEIMDAL] Heimdal Project, "Heimdal Kerberos Implementation", April
2017, <https://www.h5l.org/>.
[MITKRB5] MIT, "MIT Kerberos Implementation", March 2017,
<https://web.mit.edu/kerberos/>.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - Version [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - Version
4rev1", RFC 3501, March 2003. 4rev1", RFC 3501, March 2003.
[RFC3961] Raeburn, K., "Encryption and Checksum Specifications for [RFC3961] Raeburn, K., "Encryption and Checksum Specifications for
Kerberos 5", RFC 3961, February 2005. Kerberos 5", RFC 3961, February 2005.
[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, January 2006. Transport Layer Protocol", RFC 4253, January 2006.
[RFC4757] Jaganathan, K., Zhu, L., and J. Brezak, "The RC4-HMAC [RFC4757] Jaganathan, K., Zhu, L., and J. Brezak, "The RC4-HMAC
Kerberos Encryption Types Used by Microsoft Windows", Kerberos Encryption Types Used by Microsoft Windows",
RFC 4757, December 2606. RFC 4757, December 2006.
[RFC6150] Turner, S., and L. Chen, "MD4 to Historic Status",
RFC 6150, March 2011.
[RFC6151] Turner, S., and L. Chen, "Updated Security Considerations [RFC6151] Turner, S., and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms", for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, March 2011. RFC 6151, March 2011.
[RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
Ed., "Diameter Base Protocol", RFC 6733, October 2012.
[RFC7457] Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing [RFC7457] Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
Known Attacks on Transport Layer Security (TLS) and Known Attacks on Transport Layer Security (TLS) and
Datagram TLS (DTLS)", RFC 7457, February 2015. Datagram TLS (DTLS)", RFC 7457, February 2015.
[RFC7465] Popov, A., "Deprecating RC4 Cipher Suites", RFC 7465, [RFC7465] Popov, A., "Deprecating RC4 Cipher Suites", RFC 7465,
February 2015. February 2015.
[SCHNEIER] Schneier, B., "Applied Cryptography Second Edition:
protocols algorithms and source in code in C", John Wiley
and Sons, New York, NY, 1996.
[[RFC-Editor: please replace the 'i' in my name by U+00ED and the [[RFC-Editor: please replace the 'i' in my name by U+00ED and the
first 'a' in the surname by U+00E2, as non-ASCII characters are first 'a' in the surname by U+00E2, as non-ASCII characters are
allowed as per RFC 7997]] allowed as per RFC 7997]]
20. Author's Address 12. Author's Address
Luis Camara Luis Camara
EMail: <luis.camara@live.com.pt> EMail: <luis.camara@live.com.pt>
Appendix A. Status of Updated Documents as of 2017-06-24 Appendix A. Changelog
[[RFC-Editor: Please replace with updated data when publishing as RFC
and replace "2017-06-24" by the date of publishing.
Leave the table below in a page of its own.]]
+----------+-----------------------+--------------------------------+
| RFC #### | Status | Updated by |
+----------+-----------------------+--------------------------------+
| RFC 2118 | Informational | RFC 3078 |
+----------+-----------------------+--------------------------------+
| | | RFC 4466, RFC 4469, RFC 4551, |
| RFC 3501 | Proposed Standard | RFC 5032, RFC 5182, RFC 5738, |
| | | RFC 6186, RFC 6858, RFC 7817 |
+----------+-----------------------+--------------------------------+
| RFC 3961 | Proposed Standard | RFC xxxx |
+----------+-----------------------+--------------------------------+
| | | RFC 4537, RFC 5021, RFC 5896, |
| RFC 4120 | Proposed Standard | RFC 6111, RFC 6112, RFC 6113, |
| | | RFC 6649, RFC 6806, RFC 7751, |
| | | RFC 8062, RFC 8129 |
+----------+-----------------------+--------------------------------+
| RFC 4253 | Proposed Standard | RFC 6668 |
+----------+-----------------------+--------------------------------+
| RFC 6150 | Informational | |
+----------+-----------------------+--------------------------------+
| RFC 6649 | Best Current Practice | |
| | (BCP 179) | |
+----------+-----------------------+--------------------------------+
| RFC 6733 | Proposed Standard | RFC 7075 |
+----------+-----------------------+--------------------------------+
| RFC 7457 | Informational | |
+----------+-----------------------+--------------------------------+
| RFC 7465 | Proposed Standard | |
+----------+-----------------------+--------------------------------+
| RFC 7905 | Proposed Standard | |
+----------+-----------------------+--------------------------------+
| RFC xxxx | Best Current Practice | This draft is [RFCxxxx] |
| | | |
+----------+-----------------------+--------------------------------+
Appendix B. Changelog
[[RFC-Editor: please remove this section when publishing.]] [[RFC-Editor: please remove this section when publishing.]]
WG draft (draft-ietf-curdle-rc4-die-die-die): WG draft (draft-ietf-curdle-rc4-die-die-die):
01 - massive simplification: removed informational updates, removed
all Pre-5378 Material, retracted all "Obsoletes:" except for
RFC 4345, removed Appendix A and renamed changelog to Appendix A.
00 - dummy update to get the draft into the curdle WG. 00 - dummy update to get the draft into the curdle WG.
Individual draft (draft-luis140219-curdle-rc4-die-die-die): Individual draft (draft-luis140219-curdle-rc4-die-die-die):
02 - changed title to "Deprecating RC4 in all IETF Protocols", changed 02 - changed title to "Deprecating RC4 in all IETF Protocols", changed
the header of all pages to "Deprecating RC4 in all Protocols", the header of all pages to "Deprecating RC4 in all Protocols",
updated RFC 3501 and RFC 6733, simplified the reference to updated RFC 3501 and RFC 6733, simplified the reference to
draft-ietf-curdle-des-des-des-die-die-die to a simple "Work in draft-ietf-curdle-des-des-des-die-die-die to a simple "Work in
Progress" reference and fixed typos. Progress" reference and fixed typos.
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