HTTPbis
HTTP Working Group                                             A. Hutton
Internet-Draft                                                     Unify
Intended status: Standards Track                               J. Uberti
Expires: July 23, September 25, 2015                                       Google
                                                              M. Thomson
                                                                 Mozilla
                                                        January 19,
                                                          March 24, 2015

                 The Tunnel-Protocol HTTP Request Header Field
                 draft-ietf-httpbis-tunnel-protocol-01
                 draft-ietf-httpbis-tunnel-protocol-02

Abstract

   This specification allows HTTP CONNECT requests to indicate what
   protocol will be used within the tunnel once established, using the
   Tunnel-Protocol request header field.

Editorial Note (To be removed by RFC Editor)

   Discussion of this draft takes place on the HTTPBIS working group
   mailing list (ietf-http-wg@w3.org), which is archived at [1].

   Working Group information can be found at [2] and [3]; source code
   and issues list for this draft can be found at [4].

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
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   This Internet-Draft will expire on July 23, September 25, 2015.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  The Tunnel-Protocol HTTP Request Header Field . . . . . . . . . . . .   3
     2.1.  Header Field Values . . . . . . . . . . . . . . . . . . .   3
     2.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
     5.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   5   6

1.  Introduction

   The HTTP CONNECT method (Section 4.3.6 of [RFC7231]) requests that
   the recipient establish a tunnel to the identified origin server and
   thereafter forward packets, in both directions, until the tunnel is
   closed.  Such tunnels are commonly used to create end-to-end virtual
   connections, through one or more proxies, which may then be secured
   using TLS (Transport Layer Security, [RFC5246]). proxies.

   The HTTP Tunnel-Protocol header field identifies the protocol that
   will be spoken within the tunnel, using the application layer next
   protocol Application Layer
   Protocol Negotiation identifier [RFC7301] specified for TLS [RFC5246]. (ALPN, [RFC7301]).

   When the CONNECT method is used to establish a TLS tunnel, the Tunnel-Protocol Tunnel-
   Protocol header field may can be used to carry identify the protocol that the
   client intends to use with that tunnel.  For a tunnel that is then
   secured using TLS [RFC5246], the header field carries the same
   application protocol label as will be carried within the TLS
   handshake.  If there are multiple possible application protocols, all
   of those application protocols are indicated.

   The Tunnel-Protocol header field carries an indication of client
   intent only.  In TLS, the final choice of application protocol is
   made by the server. server from the set of choices presented by the client.
   Other protocols could negotiate protocols differently.

   Proxies do not implement the tunneled protocol, though they might
   choose to make policy decisions based on the value of the header
   field.  For example, a proxy could use the application protocol to
   select appropriate traffic prioritization.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  The Tunnel-Protocol HTTP Request Header Field

   Clients include the `Tunnel-Protocol` Request Header Tunnel-Protocol header field in an HTTP CONNECT
   request to indicate the application layer protocol that will be used
   within the tunnel, or the set of protocols that might be used within
   the tunnel.

2.1.  Header Field Values

   Valid values for the protocol field are taken from the "Application-
   Layer Protocol Negotiation (ALPN) Protocol ID" registry ([5])
   established in by [RFC7301].

2.2.  Syntax

   The ABNF (Augmented Backus-Naur Form) syntax for the `Tunnel-
   Protocol` Tunnel-Protocol
   header field is given below.  It is based on the Generic Grammar
   defined in Section 2 of [RFC7230].

   Tunnel-Protocol = "Tunnel-Protocol":" 1#protocol-id
   protocol-id     = token ; percent-encoded ALPN protocol identifier

   ALPN protocol names are octet sequences with no additional
   constraints on format.  Octets not allowed in tokens ([RFC7230],
   Section 3.2.6) must MUST be percent-encoded as per Section 2.1 of
   [RFC3986].  Consequently, the octet representing the percent
   character "%" (hex 25) must MUST be percent-encoded as well.

   In order to have precisely one way to represent any ALPN protocol
   name, the following additional constraints apply:

   o  Octets in the ALPN protocol must not MUST NOT be percent-encoded if they
      are valid token characters except "%", and

   o  When using percent-encoding, uppercase hex digits must MUST be used.

   With these constraints, recipients can apply simple string comparison
   to match protocol identifiers.

   For example:

     CONNECT www.example.com HTTP/1.1
     Host: www.example.com
     Tunnel-Protocol: h2, http%2F1.1

3.  IANA Considerations

   HTTP header fields are registered within the "Message Headers"
   registry maintained at [5]. [6].  This document defines and registers the
   `Tunnel-Protocol`
   Tunnel-Protocol header field, according to [RFC3864] as follows:

   Header Field Name:  Tunnel-Protocol

   Protocol:  http

   Status:  Standard

   Reference:  Section 2

   Change Controller:  IETF (iesg@ietf.org) - Internet Engineering Task
      Force

4.  Security Considerations

   In case of using HTTP CONNECT to a TURN server ("Traversal Using
   Relays around NAT", [RFC5766]) the security considerations of
   Section 4.3.6 of [RFC7231] apply.  It states that there "are
   significant risks in establishing a tunnel to arbitrary servers,
   particularly when the destination is a well-known or reserved TCP
   port that is not intended for Web traffic.  Proxies that support
   CONNECT SHOULD restrict its use to a limited set of known ports or a
   configurable whitelist of safe request targets."

   The `Tunnel-Protocol` request Tunnel-Protocol header field described in this document is an optional header.
   OPTIONAL header field.  Clients and HTTP Proxies proxies could choose to not
   support the header and therefore fail to provide it, or ignore it
   when present.  If the header is not available or ignored, a proxy
   cannot identify the purpose of the tunnel and use this as input to
   any authorization decision regarding the tunnel.  This is
   indistinguishable from the case where either client or proxy does not
   support the `Tunnel-Protocol` header. Tunnel-Protocol header field.

   The value of the Tunnel-Protocol header field could be falsified by a
   client.  If the data being sent through the tunnel is encrypted (for
   example, with TLS [RFC5246]), then the proxy might not be able to
   directly inspect the data to verify that the claimed protocol is the
   one which is actually being used, though a proxy might be able to
   perform traffic analysis [TRAFFIC].  A proxy therefore cannot rely on
   the value of the Tunnel-Protocol header field as a policy input in
   all cases.

5.  References

5.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997. 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3864]  Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004. 2004, <http://www.rfc-editor.org/info/rfc3864>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005. 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC7230]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Message Syntax and Routing", RFC 7230, June
              2014.
              2014, <http://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Semantics and Content", RFC 7231, June 2014. 2014,
              <http://www.rfc-editor.org/info/rfc7231>.

   [RFC7301]  Friedl, S., Popov, A., Langley, A., and E. Stephan,
              "Transport Layer Security (TLS) Application-Layer Protocol
              Negotiation Extension", RFC 7301, July 2014. 2014,
              <http://www.rfc-editor.org/info/rfc7301>.

5.2.  Informative References

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008. 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [RFC5766]  Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
              Relays around NAT (TURN): Relay Extensions to Session
              Traversal Utilities for NAT (STUN)", RFC 5766, April 2010,
              <http://www.rfc-editor.org/info/rfc5766>.

   [TRAFFIC]  Pironti, A., Strub, P-Y., and K. Bhargavan, "Website Users
              by TLS Traffic Analysis: New Attacks and Effective
              Countermeasures, Revision 1", 2012,
              <https://alfredo.pironti.eu/research/publications/full/
              identifying-website-users-tls-traffic-analysis-new-
              attacks-and-effective-counterme>.

5.3.  URIs

   [1] http://www.iana.org/assignments/tls-extensiontype-values/#alpn-
       protocol-ids

   [2] https://www.iana.org/assignments/message-headers

Authors' Addresses

   Andrew Hutton
   Unify
   Technology Drive
   Nottingham  NG9 1LA
   UK

   EMail: andrew.hutton@unify.com

   Justin Uberti
   Google
   747 6th Ave S
   Kirkland, WA  98033
   US

   EMail: justin@uberti.name

   Martin Thomson
   Mozilla
   331 E Evelyn Street
   Mountain View, CA  94041
   US

   EMail: martin.thomson@gmail.com