HTTP                                                          P. McManus
Internet-Draft                                                   Mozilla
Intended status: Standards Track                          March 27, 2018
Expires: September 28, 2018

                  Bootstrapping WebSockets with HTTP/2


   This document defines a mechanism for running the WebSocket Protocol
   over a single stream of an HTTP/2 connection.

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 28, 2018.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   ( in effect on the date of
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  The Extended CONNECT Method . . . . . . . . . . . . . . . . .   3
   5.  Using Extended CONNECT To Bootstrap The WebSocket Protocol  .   4
     5.1.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Design Considerations . . . . . . . . . . . . . . . . . . . .   5
   7.  About Intermediaries  . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The Hypertext Transfer Protocol (HTTP) provides compatible resource
   level semantics across different versions but it does not offer
   compatibility at the connection management level.  Other protocols,
   such as WebSockets, that rely on connection management details of
   HTTP must be updated for new versions of HTTP.

   The WebSocket Protocol [RFC6455] uses the HTTP/1.1 [RFC7230] Upgrade
   mechanism to transition a TCP connection from HTTP into a WebSocket
   connection.  A different approach must be taken with HTTP/2
   [RFC7540].  HTTP/2 does not allow connection wide header and status
   codes such as the Upgrade and Connection request headers or the 101
   response code due to its multiplexing nature.  These are all required
   by the [RFC6455] opening handshake.

   Being able to bootstrap WebSockets from HTTP/2 allows one TCP
   connection to be shared by both protocols and extends HTTP/2's more
   efficient use of the network to WebSockets.

   This document extends the HTTP/2 CONNECT method.  The extension
   allows the substitution of a new protocol name to connect to rather
   than the external host normally used by CONNECT.  The result is a
   tunnel on a single HTTP/2 stream that can carry data for WebSockets
   (or any other protocol).  The other streams on the connection may
   carry more extended CONNECT tunnels, traditional HTTP/2 data, or a
   mixture of both.

   This tunneled stream will be multiplexed with other regular streams
   on the connection and enjoys the normal priority, cancellation, and
   flow control features of HTTP/2.

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   Streams that successfully establish a WebSocket connection using a
   tunneled stream and the modifications to the opening handshake
   defined in this document then use the traditional WebSocket Protocol
   treating the stream as if were the TCP connection in that

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   and "OPTIONAL" are to be interpreted as described in BCP 14,


   This document adds a new SETTINGS Parameter to those defined by
   [RFC7540], Section 6.5.2.

   The new parameter name is SETTINGS_ENABLE_CONNECT_PROTOCOL.  The
   value of the parameter MUST be 0 or 1.

   Upon receipt of SETTINGS_ENABLE_CONNECT_PROTOCOL with a value of 1 a
   client MAY use the Extended CONNECT definition of this document when
   creating new streams.  Receipt of this parameter by a server does not
   have any impact.

   with the value of 0 after previously sending a value of 1.

   The use of a SETTINGS Parameter to opt-in to an otherwise
   incompatible protocol change is a use of "Extending HTTP/2" defined
   by Section 5.5 of [RFC7540].  If a client were to use the provisions
   of the extended CONNECT method defined in this document without first
   receiving a SETTINGS_ENABLE_CONNECT_PROTOCOL parameter, a non-
   supporting peer would detect a malformed request and generate a
   stream error (Section of [RFC7540]).

4.  The Extended CONNECT Method

   The CONNECT Method defined in Section 8.3 of [RFC7540] is modified in
   the following ways:

   o  A new pseudo-header :protocol MAY be included on request HEADERS
      indicating the desired protocol to be spoken on the tunnel created
      by CONNECT.  The pseudo-header is single valued and contains a
      value from the HTTP Upgrade Token Registry defined by [RFC7230].

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   o  On requests bearing the :protocol pseudo-header, the :scheme and
      :path pseudo-header fields MUST be included.

   o  On requests bearing the :protocol pseudo-header, the :authority
      pseudo-header field is interpreted according to Section of
      [RFC7540] instead of Section 8.3 of [RFC7540].  In particular the
      server MUST not make a new TCP connection to the host and port
      indicated by the :authority.

   Upon receiving a CONNECT request bearing the :protocol pseudo-header
   the server establishes a tunnel to another service of the protocol
   type indicated by the pseudo-header.  This service may or may not be
   co-located with the server.

5.  Using Extended CONNECT To Bootstrap The WebSocket Protocol

   The pseudo-header :protocol MUST be included in the CONNECT request
   and it MUST have a value of websocket to initiate a WebSocket
   connection on an HTTP/2 stream.  Other HTTP request and response
   headers, such as those for manipulating cookies, may be included in
   the HEADERS with the CONNECT :method as usual.  This request replaces
   the GET based request in [RFC6455] and is used to process the
   WebSockets opening handshake.

   The scheme of the Target URI [RFC7230] MUST be https for wss schemed
   WebSockets and http for ws schemed WebSockets.  The websocket URI is
   still used for proxy autoconfiguration.

   [RFC6455] requires the use of Connection and Upgrade headers that are
   not part of HTTP/2.  They MUST not be included in the CONNECT request
   defined here.

   [RFC6455] requires the use of a Host header which is also not part of
   HTTP/2.  The Host information is conveyed as part of the :authority
   pseudo-header which is required on every HTTP/2 transaction.

   Implementations using this extended CONNECT to bootstrap WebSockets
   do not do the processing of the [RFC6455] Sec-WebSocket-Key and Sec-
   WebSocket-Accept headers as that functionality has been superseded by
   the :protocol pseudo-header.

   The Sec-WebSocket-Version, Origin [RFC6454], Sec-WebSocket-Protocol,
   and Sec-WebSocket-Extensions headers are used on the CONNECT request
   and response headers in the same way as defined in [RFC6455].  Note
   that HTTP/1 header names were case insensitive and HTTP/2 requires
   they be encoded as lower case.

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   After successfully processing the opening handshake the peers should
   proceed with The WebSocket Protocol [RFC6455] using the HTTP/2 stream
   from the CONNECT transaction as if it were the TCP connection
   referred to in [RFC6455].  The state of the WebSocket connection at
   this point is OPEN as defined by [RFC6455], Section 4.1.

5.1.  Example

[[ From Client ]]                       [[ From Server ]]

                                        SETTINGS_ENABLE_CONNECT_PROTOCOL = 1

:method = CONNECT
:protocol = websocket
:scheme = https
:path = /chat
:authority =
sec-websocket-protocol = chat, superchat
sec-websocket-extensions = permessage-deflate
sec-websocket-version = 13
origin =

                                        HEADERS + END_HEADERS
                                        :status = 200
                                        sec-websocket-protocol = chat

WebSocket Data

                                        DATA + END_STREAM
                                        WebSocket Data

WebSocket Data

6.  Design Considerations

   A more native integration with HTTP/2 is certainly possible with
   larger additions to HTTP/2.  This design was selected to minimize the
   solution complexity while still addressing the primary concern of
   running HTTP/2 and WebSockets concurrently.

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7.  About Intermediaries

   This document does not change how WebSockets interacts with HTTP
   proxies.  If a client wishing to speak WebSockets connects via HTTP/2
   to a HTTP proxy it should continue to use a traditional (i.e. not
   with a :protocol pseudo-header) CONNECT to tunnel through that proxy
   to the WebSocket server via HTTP.

   The resulting version of HTTP on that tunnel determines whether
   WebSockets is initiated directly or via a modified CONNECT request
   described in this document.

8.  Security Considerations

   [RFC6455] ensures that non WebSockets clients, especially
   XMLHttpRequest based clients, cannot make a WebSocket connection.
   Its primary mechanism for doing that is the use of Sec- prefixed
   request headers that cannot be created by XMLHttpRequest based
   clients.  This specification addresses that concern in two ways:

   o  The CONNECT method is prohibited from being used by XMLHttpRequest

   o  The use of a pseudo-header is something that is connection
      specific and HTTP/2 does not ever allow to be created outside of
      the protocol stack.

9.  IANA Considerations

   This document establishes an entry for the HTTP/2 Settings Registry
   that was established by Section 11.3 of [RFC7540].


   Code: 0x8

   Initial Value: 0

   Specification: This document

10.  Acknowledgments

   The 2017 HTTP Workshop had a very productive discussion that helped
   determine the key problem and acceptable level of solution

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11.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6454]  Barth, A., "The Web Origin Concept", RFC 6454,
              DOI 10.17487/RFC6454, December 2011,

   [RFC6455]  Fette, I. and A. Melnikov, "The WebSocket Protocol",
              RFC 6455, DOI 10.17487/RFC6455, December 2011,

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,

Author's Address

   Patrick McManus


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