Internet DRAFT - draft-thomson-sslv3-diediedie
draft-thomson-sslv3-diediedie
Network Working Group R. Barnes
Internet-Draft M. Thomson
Updates: 5246 (if approved) Mozilla
Intended status: Best Current Practice A. Pironti
Expires: May 14, 2015 INRIA
A. Langley
Google
November 10, 2014
Deprecating Secure Sockets Layer Version 3.0
draft-thomson-sslv3-diediedie-00
Abstract
Secure Sockets Layer version 3.0 (SSLv3) [RFC6101] is no longer
secure. This document requires that SSLv3 not be used. The
replacement versions, in particular Transport Layer Security (TLS)
1.2 [RFC5246], are considerably more secure and capable protocols.
This document updates the backward compatibility sections of the TLS
RFCs to prohibit fallback to SSLv3.
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
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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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 14, 2015.
Copyright Notice
Copyright (c) 2014 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. A Litany of Attacks . . . . . . . . . . . . . . . . . . . . . 3
2.1. Record Layer . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Key Exchange . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Custom Cryptographic Primitives . . . . . . . . . . . . . 3
3. Limited Capabilities . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The SSLv3 protocol has been subject to a long series of attacks, both
on its key exchange mechanism and on the encryption schemes it
supports since it was released in 1996. Despite being replaced by
TLS 1.0 [RFC2246] in 1999, and subsequently TLS 1.1 in 2002 [RFC4346]
and 1.2 in 2006 [RFC5246], availability of these replacement versions
has not been universal. As a result, many implementations of TLS
have permitted the negotiation of SSLv3.
The predecessor of SSLv3, SSL version 2, is no longer considered
secure [RFC6176]. SSLv3 now follows.
SSLv3 MUST NOT be used [RFC2119]. Negotiation of SSLv3 from any
version of TLS MUST NOT be permitted.
This document updates Appendix E of [RFC5246]. Clients MUST NOT set
a record layer version number (TLSPlaintext.version) of {03,00}.
Clients SHOULD offer their highest supported version (that is, the
same value that appears in ClientHello.client_version); though
clients MAY use any value greater than or equal to the lowest version
number they are willing to negotiate. Servers SHOULD accept
handshakes from clients that propose SSLv3 or higher, but MUST NOT
negotiate SSLv3.
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2. A Litany of Attacks
2.1. Record Layer
The non-deterministic padding used in the CBC construction of SSLv3
trivially permits the recovery of plaintext [POODLE]. More
generally, the cipher block chaining (CBC) modes of SSLv3 use a
flawed MAC-then-encrypt construction that has subsequently been
replaced in TLS versions [RFC7366]. Unfortunately, the mechanism to
correct this flaw relies on extensions: a feature added in TLS 1.0.
SSLv3 cannot be updated to correct this flaw in the same way.
The flaws in the CBC modes in SSLv3 are mirrored by the weakness of
the stream ciphers it defines. Of those defined, only RC4 is
currently in widespread use. RC4, however, exhibits serious biases
and is also no longer fit for use [I-D.ietf-tls-prohibiting-rc4].
This leaves SSLv3 with no suitable record protection mechanism.
2.2. Key Exchange
The SSLv3 key exchange is vulnerable to man-in-the-middle attacks
when renegotiation [Ray09] or session resumption [TRIPLE-HS] are
used. Each flaw has been fixed in TLS by means of extensions.
Again, SSLv3 cannot be updated to correct these flaws.
2.3. Custom Cryptographic Primitives
SSLv3 defines custom constructions for PRF, HMAC and digital
signature primitives. Such constructions lack the deep cryptographic
scrutiny that standard constructions used by TLS have received.
Furthermore, all SSLv3 primitives rely on SHA-1 [RFC3174] and MD5
[RFC1321]: these hash algorithms are considered weak and are being
systematically replaced with stronger hash functions, such as SHA-256
[FIPS180-2].
3. Limited Capabilities
SSLv3 is unable to take advantage of the many features that have been
added to recent TLS versions. This includes the features that are
enabled by ClientHello extensions, which SSLv3 does not support.
Though SSLv3 can benefit from new cipher suites, it cannot benefit
from new cryptographic modes. Of these, the following are
particularly prominent:
o Authenticated Encryption with Additional Data (AEAD) modes are
added in [RFC5246].
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o Elliptic Curve Diffie-Hellman (ECDH) and Digital Signature
Algorithm (ECDSA) are added in [RFC4492].
o Application layer protocol negotiation [RFC7301].
o Stateless session tickets [RFC5077].
o A datagram mode of operation, DTLS [RFC6347].
4. IANA Considerations
This document has no IANA actions.
5. Security Considerations
This entire document aims to improve security by identifying a
protocol that is not secure.
6. References
6.1. Normative References
[I-D.ietf-tls-prohibiting-rc4]
Popov, A., "Prohibiting RC4 Cipher Suites", draft-ietf-
tls-prohibiting-rc4-01 (work in progress), October 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, May 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure
Sockets Layer (SSL) Protocol Version 3.0", RFC 6101,
August 2011.
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[RFC7366] Gutmann, P., "Encrypt-then-MAC for Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", RFC 7366, September 2014.
6.2. Informative References
[FIPS180-2]
Department of Commerce, National., "NIST FIPS 180-2,
Secure Hash Standard", August 2002.
[POODLE] Moeller, B., "This POODLE bites: exploiting the SSL 3.0
fallback", October 2014,
<http://googleonlinesecurity.blogspot.com/2014/10/
this-poodle-bites-exploiting-ssl-30.html>.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
[RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1
(SHA1)", RFC 3174, September 2001.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, January 2008.
[RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer
(SSL) Version 2.0", RFC 6176, March 2011.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, July 2014.
[Ray09] Ray, M., "Authentication Gap in TLS Renegotiation", 2009.
[TRIPLE-HS]
Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti,
A., and P-Y. Strub, "Triple Handshakes and Cookie Cutters:
Breaking and Fixing Authentication over TLS", IEEE
Symposium on Security and Privacy, 2014.
Authors' Addresses
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Richard Barnes
Mozilla
Email: rlb@ipv.sx
Martin Thomson
Mozilla
Email: martin.thomson@gmail.com
Alfredo Pironti
INRIA
Email: alfredo@pironti.eu
Adam Langley
Google
Email: agl@google.com
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