< draft-ietf-tls-ssl2-must-not-00.txt		draft-ietf-tls-ssl2-must-not-01.txt >
	Network Working Group S. Turner		Network Working Group S. Turner
	Internet Draft IECA		Internet Draft IECA
	Updates: 5246 (once approved) Tim Polk		Updates: 5246 (once approved) Tim Polk
	Intended Status: Standards Track NIST		Intended Status: Standards Track NIST
	Expires: February 23, 2011 August 23, 2010		Expires: April 7, 2011 October 7, 2010
	Prohibiting SSL Version 2.0		Prohibiting SSL Version 2.0
	draft-ietf-tls-ssl2-must-not-00.txt		draft-ietf-tls-ssl2-must-not-01.txt
	Abstract		Abstract
	This document requires that when TLS clients and servers establish		This document requires that when TLS clients and servers establish
	connections that they never negotiate the use of Secure Sockets Layer		connections that they never negotiate the use of Secure Sockets Layer
	(SSL) version 2.0. This document updates the backward compatibility		(SSL) version 2.0. This document updates the backward compatibility
	sections found in the Transport Security Layer (TLS) Protocol, RFC		sections found in the Transport Security Layer (TLS) Protocol, RFC
	5246.		5246.
	Status of this Memo		Status of this Memo
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	This Internet-Draft will expire on February 23, 2009.		This Internet-Draft will expire on April 7, 2009.
	Copyright Notice		Copyright Notice
	Copyright (c) 2010 IETF Trust and the persons identified as the		Copyright (c) 2010 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 36 ¶		skipping to change at page 2, line 36 ¶
	the Transport Security Layer (TLS) Protocol [TLS] and earlier		the Transport Security Layer (TLS) Protocol [TLS] and earlier
	versions.		versions.
	1.1. Requirements Terminology		1.1. Requirements Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	[RFC2119].		[RFC2119].
	2. SSL 2.0		2. SSL 2.0 Deficiencies
	SSL version 2.0 [SSL2] deficiencies include:		SSL version 2.0 [SSL2] deficiencies include:
	o Message authentication uses MD5 [MD5]. Most security-aware users		o Message authentication uses MD5 [MD5]. Most security-aware users
	have already moved away from any of MD5		have already moved away from any use of MD5
	[I-D.turner-md5-seccon-update].		[I-D.turner-md5-seccon-update].
	o Handshake messages are not protected. This permits a man-in-the-		o Handshake messages are not protected. This permits a man-in-the-
	middle to trick the client into picking a weaker cipher suite than		middle to trick the client into picking a weaker cipher suite than
	they would normally choose.		they would normally choose.
	o Message integrity and message encryption use the same key, which		o Message integrity and message encryption use the same key, which
	is a problem if the client and server negotiate a weak encryption		is a problem if the client and server negotiate a weak encryption
	algorithm.		algorithm.
	o Sessions can be easily terminated. A man-in-the-middle can easily		o Sessions can be easily terminated. A man-in-the-middle can easily
	insert a TCP FIN to close the session and the peer is unable to		insert a TCP FIN to close the session and the peer is unable to
	determine whether or not it was a legitimate end of the session.		determine whether or not it was a legitimate end of the session.
	3. Changes to TLS		3. Changes to TLS
	Because of the deficiencies noted in the previous sections, TLS		Because of the deficiencies noted in the previous section:
	implementations MUST NOT support SSL 2.0. The specific changes to
	[TLS], including earlier versions, are as follows:
	o TLS clients MUST NOT use SSL 2.0 ClientHello messages.		o TLS clients MUST NOT negotiate or use SSL 2.0.
	o TLS servers MUST NOT accept SSL 2.0 ClientHello messages.		o TLS clients MUST NOT send SSL 2.0 ClientHello messages.
			o TLS servers MUST NOT negotiate or use SSL 2.0.
			As described in [TLS], TLS servers that do not support SSL 2.0 MAY
			accept version 2.0 CLIENT-HELLO messages as the first message of a
			TLS handshake for interoperability with old clients.
	4. IANA Considerations		4. IANA Considerations
	None.		None.
	5. Security Considerations		5. Security Considerations
	This entire document is about security considerations.		This entire document is about security considerations.
	6. Acknowledgements		6. Acknowledgements
	The idea for this document was inspired by discussions between Peter		The idea for this document was inspired by discussions between Peter
	Saint Andre, Simon Josefsson, and others on the XMPP mailing list.		Saint Andre, Simon Josefsson, and others on the XMPP mailing list.
	We would also like to thank Paul Hoffman, Yaron Sheffer, and Nikos		We would also like to thank Michael D'Errico, Paul Hoffman, Nikos
	Mavrogiannopoulos, Yngve Pettersen, Marsh Ray, and Martin Rex for		Mavrogiannopoulos, Yngve Pettersen, Marsh Ray, Martin Rex, and Yaron
	reviews and comments on earlier versions of this document.		Sheffer for their reviews and comments.
	7. References		7. References
	7.1. Normative References		7.1. 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.
	[TLS] Dierks, T. and E. Rescorla, "The Transport Layer		[TLS] Dierks, T. and E. Rescorla, "The Transport Layer
	Security (TLS) Protocol Version 1.2", RFC 5246,		Security (TLS) Protocol Version 1.2", RFC 5246,
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