Encrypt-then-MAC for Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
RFC 7366
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RFC - Proposed Standard
(September 2014; Errata)
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Last updated |
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2015-10-14
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Replaces |
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draft-gutmann-tls-encrypt-then-mac
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IETF
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plain text
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html
bibtex
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Sean Turner
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Shepherd write-up |
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Show
(last changed 2014-05-21)
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| IESG |
IESG state |
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RFC 7366 (Proposed Standard)
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Consensus Boilerplate |
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Unknown
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Responsible AD |
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Stephen Farrell
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(None)
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| IANA |
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IANA OK - Actions Needed
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RFC-Ed-Ack
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Internet Engineering Task Force (IETF) P. Gutmann
Request for Comments: 7366 University of Auckland
Category: Standards Track September 2014
ISSN: 2070-1721
Encrypt-then-MAC for Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)
Abstract
This document describes a means of negotiating the use of the
encrypt-then-MAC security mechanism in place of the existing MAC-
then-encrypt mechanism in Transport Layer Security (TLS) and Datagram
Transport Layer Security (DTLS). The MAC-then-encrypt mechanism has
been the subject of a number of security vulnerabilities over a
period of many years.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7366.
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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Gutmann Standards Track [Page 1]
RFC 7366 Encrypt-then-MAC for TLS and DTLS September 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 2
2. Negotiating Encrypt-then-MAC . . . . . . . . . . . . . . . . 2
2.1. Rationale . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Applying Encrypt-then-MAC . . . . . . . . . . . . . . . . . . 3
3.1. Rehandshake Issues . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 7
1. Introduction
TLS [2] and DTLS [4] use a MAC-then-encrypt construction that was
regarded as secure at the time the original Secure Socket Layer (SSL)
protocol was specified in the mid-1990s, but that is no longer
regarded as secure [5] [6]. This construction, as used in TLS and
later DTLS, has been the subject of numerous security vulnerabilities
and attacks stretching over a period of many years. This document
specifies a means of switching to the more secure encrypt-then-MAC
construction as part of the TLS/DTLS handshake, replacing the current
MAC-then-encrypt construction. (In this document, "MAC" refers to
"Message Authentication Code".)
1.1. Conventions Used in This Document
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 [1].
2. Negotiating Encrypt-then-MAC
The use of encrypt-then-MAC is negotiated via TLS/DTLS extensions as
defined in TLS [2]. On connecting, the client includes the
encrypt_then_mac extension in its client_hello if it wishes to use
encrypt-then-MAC rather than the default MAC-then-encrypt. If the
server is capable of meeting this requirement, it responds with an
encrypt_then_mac in its server_hello. The "extension_type" value for
this extension SHALL be 22 (0x16), and the "extension_data" field of
this extension SHALL be empty. The client and server MUST NOT use
encrypt-then-MAC unless both sides have successfully exchanged
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