Gossiping in CT
draft-ietf-trans-gossip-05

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TRANS                                                        L. Nordberg
Internet-Draft                                                  NORDUnet
Intended status: Experimental                                 D. Gillmor
Expires: July 18, 2018                                              ACLU
                                                               T. Ritter
                                                        January 14, 2018

                            Gossiping in CT
                       draft-ietf-trans-gossip-05

Abstract

   The logs in Certificate Transparency are untrusted in the sense that
   the users of the system don't have to trust that they behave
   correctly since the behavior of a log can be verified to be correct.

   This document tries to solve the problem with logs presenting a
   "split view" of their operations or failing to incorporate a
   submission within MMD.  It describes three gossiping mechanisms for
   Certificate Transparency: SCT Feedback, STH Pollination and Trusted
   Auditor Relationship.

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."

   This Internet-Draft will expire on July 18, 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
   (http://trustee.ietf.org/license-info) in effect on the date of

Nordberg, et al.          Expires July 18, 2018                 [Page 1]
Internet-Draft               Gossiping in CT                January 2018

   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
   2.  Defining the problem  . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Pre-Loaded vs Locally Added Anchors . . . . . . . . . . .   5
   5.  Who gossips with whom . . . . . . . . . . . . . . . . . . . .   5
   6.  What to gossip about and how  . . . . . . . . . . . . . . . .   6
   7.  Data flow . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Gossip Mechanisms . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  SCT Feedback  . . . . . . . . . . . . . . . . . . . . . .   7
       8.1.1.  SCT Feedback data format  . . . . . . . . . . . . . .   8
       8.1.2.  HTTPS client to server  . . . . . . . . . . . . . . .   9
       8.1.3.  HTTPS server operation  . . . . . . . . . . . . . . .  11
       8.1.4.  HTTPS server to auditors  . . . . . . . . . . . . . .  13
     8.2.  STH pollination . . . . . . . . . . . . . . . . . . . . .  14
       8.2.1.  HTTPS Clients and Proof Fetching  . . . . . . . . . .  16
       8.2.2.  STH Pollination without Proof Fetching  . . . . . . .  17
       8.2.3.  Auditor Action  . . . . . . . . . . . . . . . . . . .  17
       8.2.4.  STH Pollination data format . . . . . . . . . . . . .  18
     8.3.  Trusted Auditor Stream  . . . . . . . . . . . . . . . . .  18
       8.3.1.  Trusted Auditor data format . . . . . . . . . . . . .  19
   9.  3-Method Ecosystem  . . . . . . . . . . . . . . . . . . . . .  20
     9.1.  SCT Feedback  . . . . . . . . . . . . . . . . . . . . . .  20
     9.2.  STH Pollination . . . . . . . . . . . . . . . . . . . . .  20
     9.3.  Trusted Auditor Relationship  . . . . . . . . . . . . . .  21
     9.4.  Interaction . . . . . . . . . . . . . . . . . . . . . . .  22
   10. Security considerations . . . . . . . . . . . . . . . . . . .  23
     10.1.  Attacks by actively malicious logs . . . . . . . . . . .  23
     10.2.  Dual-CA Compromise . . . . . . . . . . . . . . . . . . .  23
     10.3.  Censorship/Blocking considerations . . . . . . . . . . .  24
     10.4.  Flushing Attacks . . . . . . . . . . . . . . . . . . . .  25
       10.4.1.  STHs . . . . . . . . . . . . . . . . . . . . . . . .  25
       10.4.2.  SCTs & Certificate Chains on HTTPS Servers . . . . .  26