HTTP                                                          P. McManus
Internet-Draft                                                   Mozilla
Updates: 6455 (if approved)                                June 18, 2018
Intended status: Standards Track
Expires: December 20, 2018

                  Bootstrapping WebSockets with HTTP/2


   This document defines a mechanism for running the WebSocket Protocol
   (RFC 6455) 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.

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   This Internet-Draft will expire on December 20, 2018.

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Table of Contents

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

1.  Introduction

   The Hypertext Transfer Protocol (HTTP) [RFC7230] 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 Upgrade mechanism
   (Section 6.7 of [RFC7230]) 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
   fields and status codes such as the Upgrade and Connection request
   header fields or the 101 (Switching Protocols) 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 CONNECT method (as specified for
   HTTP/2 in Section 8.3 of [RFC7540]).  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

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   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.

   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

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.


   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].  Specifically, the addition a new
   pseudo-header field ":protocol" and the change in meaning of the
   ":authority" pseudo-header field in Section 4 require opt-in
   negotiation.  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]).

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4.  The Extended CONNECT Method

   Usage of the CONNECT method in HTTP/2 is defined by Section 8.3 of
   [RFC7540].  This extension modifies the method in the following ways:

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

   o  On requests that contain the :protocol pseudo-header field, the
      :scheme and :path pseudo-header fields of the target URI (See
      Section 5) MUST also be included.

   o  On requests bearing the :protocol pseudo-header field, 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 create a tunnel to the host
      indicated by the :authority as it would with a CONNECT method
      request that was not modified by this extension.

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

5.  Using Extended CONNECT To Bootstrap the WebSocket Protocol

   The :protocol pseudo-header field 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 header fields, 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 (Section 5.1 of [RFC7230]) MUST be
   "https" for "wss" schemed WebSockets and "http" for "ws" schemed
   WebSockets.  The remainder of the Target URI is the same as the
   websocket URI.  The websocket URI is still used for proxy
   autoconfiguration.  The security requirements for the HTTP/2
   connection used by this specification are established by [RFC7540]
   for https requests and [RFC8164] for http requests.

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

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

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

   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.

   The HTTP/2 stream closure is also analogous to the TCP connection
   closure of [RFC6455].  Orderly TCP level closures are represented as
   END_STREAM ([RFC7540], Section 6.1) flags and RST exceptions are
   represented with the RST_STREAM ([RFC7540], Section 6.4) frame with
   the CANCEL ([RFC7540], Section 7) error code.

5.1.  Example

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

                                        SETTINGS_ENABLE_CONNECT_[..] = 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.

7.  About Intermediaries

   This document does not change how WebSockets interacts with HTTP
   forward proxies.  If a client wishing to speak WebSockets connects
   via HTTP/2 to an HTTP proxy it should continue to use a traditional
   (i.e. not with a :protocol pseudo-header field) 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.

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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 header fields that cannot be created by XMLHttpRequest-based
   clients.  This specification addresses that concern in two ways:

   o  XMLHttpRequest also prohibits use of the CONNECT method in
      addition to Sec- prefixed request header fields.

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

   The security considerations of [RFC6455] section 10 continue to apply
   to the use of the WebSocket Protocol when using this specification
   with the exception of 10.8.  That section is not relevant because it
   is specific to the boostrapping handshake that is changed in this

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.  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,

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   [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,

   [RFC8164]  Nottingham, M. and M. Thomson, "Opportunistic Security for
              HTTP/2", RFC 8164, DOI 10.17487/RFC8164, May 2017,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.


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

Author's Address

   Patrick McManus


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