Expect-CT Extension for HTTP
draft-ietf-httpbis-expect-ct-08
HTTP E. Stark
Internet-Draft Google
Intended status: Experimental December 9, 2018
Expires: June 12, 2019
Expect-CT Extension for HTTP
draft-ietf-httpbis-expect-ct-08
Abstract
This document defines a new HTTP header field named Expect-CT, which
allows web host operators to instruct user agents to expect valid
Signed Certificate Timestamps (SCTs) to be served on connections to
these hosts. Expect-CT allows web host operators to discover
misconfigurations in their Certificate Transparency deployments.
Further, web host operaters can use Expect-CT to ensure that, if a UA
which supports Expect-CT accepts a misissued certificate, that
certificate will be 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/ [1].
Working Group information can be found at http://httpwg.github.io/
[2]; source code and issues list for this draft can be found at
https://github.com/httpwg/http-extensions/labels/expect-ct [3].
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-
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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
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 12, 2019.
Stark Expires June 12, 2019 [Page 1]
Internet-Draft Expect-CT December 2018
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Server and Client Behavior . . . . . . . . . . . . . . . . . 5
2.1. Response Header Field Syntax . . . . . . . . . . . . . . 5
2.1.1. The report-uri Directive . . . . . . . . . . . . . . 6
2.1.2. The enforce Directive . . . . . . . . . . . . . . . . 7
2.1.3. The max-age Directive . . . . . . . . . . . . . . . . 7
2.1.4. Examples . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Host Processing Model . . . . . . . . . . . . . . . . . . 8
2.2.1. HTTP-over-Secure-Transport Request Type . . . . . . . 8
2.2.2. HTTP Request Type . . . . . . . . . . . . . . . . . . 8
2.3. User Agent Processing Model . . . . . . . . . . . . . . . 8
2.3.1. Missing or Malformed Expect-CT Header Fields . . . . 9
2.3.2. Expect-CT Header Field Processing . . . . . . . . . . 9
2.3.3. Reporting . . . . . . . . . . . . . . . . . . . . . . 11
2.4. Evaluating Expect-CT Connections for CT Compliance . . . 11
2.4.1. Skipping CT compliance checks . . . . . . . . . . . . 12
3. Reporting Expect-CT Failure . . . . . . . . . . . . . . . . . 12
3.1. Generating a violation report . . . . . . . . . . . . . . 12
3.2. Sending a violation report . . . . . . . . . . . . . . . 14
3.3. Receiving a violation report . . . . . . . . . . . . . . 15
4. Usability Considerations . . . . . . . . . . . . . . . . . . 16
5. Authoring Considerations . . . . . . . . . . . . . . . . . . 16
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7.1. Hostile header attacks . . . . . . . . . . . . . . . . . 17
7.2. Maximum max-age . . . . . . . . . . . . . . . . . . . . . 17
7.3. Amplification attacks . . . . . . . . . . . . . . . . . . 18
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