Expect-CT Extension for HTTP
draft-ietf-httpbis-expect-ct-08

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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-
   Drafts is at https://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."

   This Internet-Draft will expire on June 12, 2019.

Stark                     Expires June 12, 2019                 [Page 1]
Internet-Draft                  Expect-CT                  December 2018

Copyright Notice

   Copyright (c) 2018 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
   (https://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
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   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 . . . . . . . . . . . . . . . . . .   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