Expect-CT Extension for HTTP
draft-ietf-httpbis-expect-ct-02
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2017-08-14
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HTTP Working Group E. Stark
Internet-Draft Google
Intended status: Experimental August 14, 2017
Expires: February 15, 2018
Expect-CT Extension for HTTP
draft-ietf-httpbis-expect-ct-02
Abstract
This document defines a new HTTP header, named Expect-CT, that allows
web host operators to instruct user agents to expect valid Signed
Certificate Timestamps (SCTs) to be served on connections to these
hosts. When configured in enforcement mode, user agents (UAs) will
remember that hosts expect SCTs and will refuse connections that do
not conform to the UA's Certificate Transparency policy. When
configured in report-only mode, UAs will report the lack of valid
SCTs to a URI configured by the host, but will allow the connection.
By turning on Expect-CT, web host operators can discover
misconfigurations in their Certificate Transparency deployments and
ensure that misissued certificates accepted by UAs are discoverable
in Certificate Transparency logs.
Note to Readers
Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/.
Working Group information can be found at http://httpwg.github.io/;
source code and issues list for this draft can be found at
https://github.com/httpwg/http-extensions/labels/expect-ct.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
Stark Expires February 15, 2018 [Page 1]
Internet-Draft Expect-CT August 2017
This Internet-Draft will expire on February 15, 2018.
Copyright Notice
Copyright (c) 2017 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Server and Client Behavior . . . . . . . . . . . . . . . . . 4
2.1. Response Header Field Syntax . . . . . . . . . . . . . . 4
2.1.1. The report-uri Directive . . . . . . . . . . . . . . 5
2.1.2. The enforce Directive . . . . . . . . . . . . . . . . 6
2.1.3. The max-age Directive . . . . . . . . . . . . . . . . 7
2.1.4. Examples . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Server Processing Model . . . . . . . . . . . . . . . . . 7
2.2.1. HTTP-over-Secure-Transport Request Type . . . . . . . 7
2.2.2. HTTP Request Type . . . . . . . . . . . . . . . . . . 8
2.3. User Agent Processing Model . . . . . . . . . . . . . . . 8
2.3.1. Expect-CT Header Field Processing . . . . . . . . . . 8
2.3.2. HTTP-Equiv <meta> Element Attribute . . . . . . . . . 9
2.3.3. Noting Expect-CT . . . . . . . . . . . . . . . . . . 9
2.3.4. Storage Model . . . . . . . . . . . . . . . . . . . . 9
2.4. Evaluating Expect-CT Connections for CT Compliance . . . 10
3. Reporting Expect-CT Failure . . . . . . . . . . . . . . . . . 11
3.1. Generating a violation report . . . . . . . . . . . . . . 11
3.2. Sending a violation report . . . . . . . . . . . . . . . 13
4. Security Considerations . . . . . . . . . . . . . . . . . . . 13
4.1. Maximum max-age . . . . . . . . . . . . . . . . . . . . . 14
4.2. Avoiding amplification attacks . . . . . . . . . . . . . 14
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