The Transport Layer Security (TLS) Multiple Certificate Status Request Extension
RFC 6961

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Internet Engineering Task Force (IETF)                      Y. Pettersen
Request for Comments: 6961                                     June 2013
Category: Standards Track
ISSN: 2070-1721

                   The Transport Layer Security (TLS)
             Multiple Certificate Status Request Extension

Abstract

   This document defines the Transport Layer Security (TLS) Certificate
   Status Version 2 Extension to allow clients to specify and support
   several certificate status methods.  (The use of the Certificate
   Status extension is commonly referred to as "OCSP stapling".)  Also
   defined is a new method based on the Online Certificate Status
   Protocol (OCSP) that servers can use to provide status information
   about not only the server's own certificate but also the status of
   intermediate certificates in the chain.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6961.

Pettersen                    Standards Track                    [Page 1]
RFC 6961          Multiple Certificate Status Extension        June 2013

Copyright Notice

   Copyright (c) 2013 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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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   than English.

1.  Introduction

   The Transport Layer Security (TLS) Extension [RFC6066] framework
   defines, among other extensions, the Certificate Status extension
   (also referred to as "OCSP stapling") that clients can use to request
   the server's copy of the current status of its certificate.  The
   benefits of this extension include a reduced number of roundtrips and
   network delays for the client to verify the status of the server's
   certificate and a reduced load on the certificate issuer's status
   response servers, thus solving a problem that can become significant
   when the issued certificate is presented by a frequently visited
   server.

   There are two problems with the existing Certificate Status
   extension.  First, it does not provide functionality to request the
   status information about intermediate Certification Authority (CA)
   certificates, which means the client has to request status
   information through other methods, such as Certificate Revocation
   Lists (CRLs), introducing further delays.  Second, the current format
   of the extension and requirements in the TLS protocol prevent a
   client from offering the server multiple status methods.

Pettersen                    Standards Track                    [Page 2]
RFC 6961          Multiple Certificate Status Extension        June 2013

   Many CAs are now issuing intermediate CA certificates that not only
   specify the publication point for their CRLs in a CRL Distribution
   Point [RFC5280] but also specify a URL for their OCSP [RFC6960]
   server in Authority Information Access [RFC5280].  Given that
   client-cached CRLs are frequently out of date, clients would benefit
   from using OCSP to access up-to-date status information about
   intermediate CA certificates.  The benefit to the issuing CA is less
   clear, as providing the bandwidth for the OCSP responder can be
   costly, especially for CAs with many high-traffic subscriber sites,
   and this cost is a concern for many CAs.  There are cases where OCSP