Certificate Limitation Policy

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Last updated 2017-06-20
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Internet-Draft                                             June 20, 2017
Intended status: Experimental
Expires: December 22, 2017

                     Certificate Limitation Policy


   The document provides a specification of the application-level trust
   model.  Being provided at the application level, the limitations of
   trust can be distributed separately using cryptographically protected
   format instead of hardcoding the checks into the application itself.

Status of This Memo

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   This Internet-Draft will expire on December 22, 2017.

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1.  Introduction

   Binary trust model standardized as a set of trusted anchors and CRLs/
   OCSP services does not cover all corner cases in the modern crypto
   world.  There is a need in more differentiated limitations.  Some of
   them are suggested by Google when it limits the usage of Symantec's
   certificates.  The CRL profile does not fit the purpose of such
   limitations.  The CRLs are issued by the same CAs that are subject to
   be limited.

   Currently the set of CAs trusted by OS can be used for the validation
   purposes.  In case when a large enough CA becomes untrusted, it
   cannot be deleted from the storage of trusted CAs because it may
   cause error of validation of many certificates.  The measures usually
   taken in such cases usually include application-level limitation of
   certificates lifetimes, refuse to accept EV-certificates in other way
   than DV, requirements of usage Certificate Transparency, etc.

   This document suggests a cryptographically protected format of
   description of such limitations.  This format can be used by
   applications that use system-wide set of trust anchors for validating
   purposes or by applications with own wide enough set of trusted
   anchors in case when the trust anchor for the entity found
   misbehaving cannot be revoked.

   Currently the only way to provide such limitations is hard coding in
   application itself.  Using of CLPs does not allow to completely avoid
   hard coding but allows to hard code only the minimal set of rarely
   changing data, such as the certificate to verify the signature and
   minimal date of issuance (see below).

2.  Certificate Limitations Profile

   A proposed syntax and overall structure of CLP is very similar to the
   one defined for CRLs.  TBD.

2.1.  CLP fields


2.2.  CLP extensions


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2.3.  CLP signature

   The key used for signing the CLP files should have a special Key
   Usage bit and/or an Extended Key Usage value.

2.4.  CLP entry fields

   Each entry in list contains the following fields:

      The issuer of the certificate with limited trust.

      The serial of the certificate with limited trust.

      The fingerprint of the certificate with limited trust (optional).

      The flag indicating whether limitations are applied to the
      certificate itself or to all of its descendants in the chain of

   and a subset of the following limitations:

      maxPeriodStart (do not trust the certs issued after)

      maxPeriodEnd (do not trust the certs after)

      validityPeriod (take minimal value from "native" validity period
      and specified in the limitation file)

      ignoreX509Extensions (e.g.  EV)

      requiredX509extensions (do not trust the certificates )
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