Client-Cert HTTP Header: Conveying Client Certificate Information from TLS Terminating Reverse Proxies to Origin Server Applications
draft-bdc-something-something-certificate-02

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Aspirational                                                 B. Campbell
Internet-Draft                                             Ping Identity
Intended status: Standards Track                        12 February 2020
Expires: 15 August 2020

 Client-Cert HTTP Header: Conveying Client Certificate Information from
     TLS Terminating Reverse Proxies to Origin Server Applications
              draft-bdc-something-something-certificate-02

Abstract

   This document defines the HTTP header field "Client-Cert" that allows
   a TLS terminating reverse proxy to convey information about the
   client certificate of a mutually-authenticated TLS connection to an
   origin server in a common and predictable manner.

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   This Internet-Draft will expire on 15 August 2020.

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Campbell                 Expires 15 August 2020                 [Page 1]
Internet-Draft             Client-Cert Header              February 2020

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  HTTP Header Field and Processing Rules  . . . . . . . . . . .   3
     2.1.  Encoding  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Client-Cert HTTP Header Field . . . . . . . . . . . . . .   4
     2.3.  Processing Rules  . . . . . . . . . . . . . . . . . . . .   4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   6.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Example  . . . . . . . . . . . . . . . . . . . . . .   7
   Appendix B.  Considerations Considered  . . . . . . . . . . . . .   9
     B.1.  Header Injection  . . . . . . . . . . . . . . . . . . . .   9
     B.2.  The Forwarded HTTP Extension  . . . . . . . . . . . . . .   9
     B.3.  The Whole Certificate and Only the Whole Certificate  . .  10
   Appendix C.  Acknowledgements . . . . . . . . . . . . . . . . . .  10
   Appendix D.  Document History . . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   A fairly common deployment pattern for HTTPS applications is to have
   the origin HTTP application servers sit behind a reverse proxy that
   terminates TLS connections from clients.  The proxy is accessible to
   the internet and dispatches client requests to the appropriate origin
   server within a private or protected network.  The origin servers are
   not directly accessible by clients and are only reachable through the
   reverse proxy.  The backend details of this type of deployment are
   typically opaque to clients who make requests to the proxy server and
   see responses as though they originated from the proxy server itself.
   Although HTTPS is also usually employed between the proxy and the
   origin server, the TLS connection that the client establishes for
   HTTPS is only between itself and the reverse proxy server.

   The deployment pattern is found in a number of varieties such as
   n-tier architectures, content delivery networks, application load
   balancing services, and ingress controllers.

   Although not exceedingly prevalent, TLS client certificate
   authentication is sometimes employed and in such cases the origin
   server often requires information about the client certificate for
   its application logic.  Such logic might include access control
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