Attack and Threat Model for Certificate Transparency
draft-ietf-trans-threat-analysis-13

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Public Notary Transparency                                       S. Kent
Internet-Draft                                               Independent
Intended status: Informational                            April 12, 2018
Expires: October 14, 2018

          Attack and Threat Model for Certificate Transparency
                  draft-ietf-trans-threat-analysis-13

Abstract

   This document describes an attack model and discusses threats for the
   Web PKI context in which security mechanisms to detect mis-issuance
   of web site certificates are being developed.  The model provides an
   analysis of detection and remediation mechanisms for both syntactic
   and semantic mis-issuance.  The model introduces an outline of
   attacks to organize the discussion.  The model also describes the
   roles played by the elements of the Certificate Transparency (CT)
   system, to establish a context for the model.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on October 14, 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
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   (https://trustee.ietf.org/license-info) in effect on the date of
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Kent                    Expires October 14, 2018                [Page 1]
Internet-Draft  Attack Model for Certificate Mis-issuance     April 2018

   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.  Conventions used in this document . . . . . . . . . . . .   7
   2.  Threats . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  Semantic mis-issuance . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Non-malicious Web PKI CA context  . . . . . . . . . . . .   9
       3.1.1.  Certificate logged  . . . . . . . . . . . . . . . . .   9
       3.1.2.  Certificate not logged  . . . . . . . . . . . . . . .  11
     3.2.  Malicious Web PKI CA context  . . . . . . . . . . . . . .  12
       3.2.1.  Certificate logged  . . . . . . . . . . . . . . . . .  12
       3.2.2.  Certificate not logged  . . . . . . . . . . . . . . .  14
     3.3.  Undetected Compromise of CAs or Logs  . . . . . . . . . .  15
       3.3.1.  Compromised CA, Benign Log  . . . . . . . . . . . . .  15
       3.3.2.  Benign CA, Compromised Log  . . . . . . . . . . . . .  17
       3.3.3.  Compromised CA, Compromised Log . . . . . . . . . . .  17
     3.4.  Attacks Based on Exploiting Multiple Certificate Chains .  18
     3.5.  Attacks Related to Distribution of Revocation Status  . .  20
   4.  Syntactic mis-issuance  . . . . . . . . . . . . . . . . . . .  21
     4.1.  Non-malicious Web PKI CA context  . . . . . . . . . . . .  21
       4.1.1.  Certificate logged  . . . . . . . . . . . . . . . . .  21
       4.1.2.  Certificate not logged  . . . . . . . . . . . . . . .  23
     4.2.  Malicious Web PKI CA context  . . . . . . . . . . . . . .  23
       4.2.1.  Certificate logged  . . . . . . . . . . . . . . . . .  24
       4.2.2.  Certificate is not logged . . . . . . . . . . . . . .  25
   5.  Issues Applicable to Sections 3 and 4 . . . . . . . . . . . .  25
     5.1.  How does a Subject know which Monitor(s) to use?  . . . .  25
     5.2.  How does a Monitor discover new logs? . . . . . . . . . .  25
     5.3.  CA response to report of a bogus or erroneous certificate  26
     5.4.  Browser behavior  . . . . . . . . . . . . . . . . . . . .  26
     5.5.  Remediation for a malicious CA  . . . . . . . . . . . . .  26
     5.6.  Auditing - detecting misbehaving logs . . . . . . . . . .  27
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  29