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Versions: 00 01 02 draft-ietf-httpbis-h2-websockets

Network Working Group                                         P. McManus
Internet-Draft                                                   Mozilla
Intended status: Standards Track                        October 26, 2017
Expires: April 29, 2018


                  Bootstrapping WebSockets with HTTP/2
                 draft-mcmanus-httpbis-h2-websockets-01

Abstract

   This document defines a mechanism for running the WebSocket Protocol
   [RFC6455] 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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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on April 29, 2018.

Copyright Notice

   Copyright (c) 2017 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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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The ENABLE_CONNECT_PROTOCOL SETTINGS Parameter  . . . . . . .   3
   4.  The Extended CONNECT Method . . . . . . . . . . . . . . . . .   3
   5.  Using Extended CONNECT To Bootstrap The WebSocket Protocol  .   4
     5.1.  Connection Preamble . . . . . . . . . . . . . . . . . . .   5
       5.1.1.  Version Type  . . . . . . . . . . . . . . . . . . . .   5
       5.1.2.  Subprotocol Type  . . . . . . . . . . . . . . . . . .   5
       5.1.3.  Extensions Type . . . . . . . . . . . . . . . . . . .   6
       5.1.4.  Origin Type . . . . . . . . . . . . . . . . . . . . .   6
       5.1.5.  End-Preamble Type . . . . . . . . . . . . . . . . . .   6
     5.2.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Design Considerations . . . . . . . . . . . . . . . . . . . .   8
   7.  About Intermediaries  . . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

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].  The multiplexing nature of 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]
   connection establishment process.

   Being able to bootstrap WebSockets from HTTP/2 allows one TCP
   connection to be easily 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




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   (or any other protocol).  The other streams on the connection may
   carry more extended CONNECT tunnels or traditional HTTP/2 data.

   Streams that have been successfully established as protocol tunnels
   proceed to establish and utilize the WebSocket Protocol using the
   procedure defined by [RFC6455] treating the stream as if were the
   connection in that specification.

   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.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in BCP 14,
   [RFC2119].

3.  The ENABLE_CONNECT_PROTOCOL SETTINGS Parameter

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

   The new parameter is ENABLE_CONNECT_PROTOCOL (type = 0x8).  The value
   of the parameter MUST be 0 or 1.

   Upon receipt of 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.

   A sender MUST NOT send a ENABLE_CONNECT_PROTOCOL parameter 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 ENABLE_CONNECT_PROTOCOL parameter with the value of 1 it
   would be a protocol violation.

4.  The Extended CONNECT Method

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





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   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].

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

   o  On requests bearing the :protocol pseudo-header, the :authority
      pseudo-header field is interpreted according to [RFC7540]
      Section 8.1.2.3 instead of [RFC7540] Section 8.3.  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.

   Parameters specific to WebSockets connection establishment, such as
   the version and sub-protocol are carried in a preamble within the
   HTTP/2 tunnel.  This information was included in the HTTP headers in
   HTTP/1 but can now be conveyed in an HTTP independent fashion because
   the use of CONNECT with a new extension specific pseudo-header
   assures that the request can only be generated by a WebSocket client
   (See also Security Considerations).

   The WebSocket peers process the opening handshake of [RFC6455]
   Section 4, using the information from the HTTP HEADERS and the
   connection preamble defined in this document.  Substitutions are made
   for the preamble types defined here that were previously carried in
   HTTP/1 headers.  For example, :authority pseudo-header provides the
   information from the Host header, and the Version preamble type
   provides the information from the Sec-WebSocket-Version header.

   Implementations using this extended CONNECT to bootstrap WebSockets
   do not do the processing of the HTTP/1 Sec-WebSocket-Key and Sec-
   WebSocket-Accept headers as that functionality has been superceded by
   the :protocol pseudo-header.




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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.  Connection Preamble

   The connection preamble contains parameter information necessary for
   processing the WebSocket opening handshake.  It is exchanged in both
   directions as the content of the first DATA frames on the HTTP/2
   stream.  The connection preamble parameter list is prefaced by a
   constant 16 byte sequence.  This marker facilitates fast failure in
   cases where the endpoints are confused about what protocol is being
   spoken.  The 16 bytes are: CA A4 02 0A 75 19 4D 49 86 4E A7 8F 14 86
   CF 08.

   Parameters such as WebSocket version, sub-protocol, and available
   extensions are exchanged as a series of Type, Length, Value (TLV)
   tuples.  The preamble format is specific to WebSockets over HTTP/2.
   The tuples may appear in any order with the exception of the End-
   Preamble type which must appear last.

   Each tuple consists of 1 type byte, 2 bytes specifying the network-
   order length of the value, and the length specified number of bytes
   containing the value.

   Multiple TLV tuples of the same type form an ordered list of values.
   A single tuple contains only a single value (i.e. comma separated
   lists are not supported).

   Several HTTP headers from [RFC6455] have corresponding preamble types
   defined here.  Sec-WebSocket-Key and Sec-WebSocket-Accept are no
   longer used and do not have corresponding definitions.

5.1.1.  Version Type

   The Version type (0x00) MUST have a length of 1 and indicates the
   version of the WebSocket Protocol available.  This corresponds to the
   Sec-WebSocket-Version header of [RFC6455].  It MUST appear at least
   one time in the client preamble and MUST appear exactly one time in
   the server preamble.  The value defined by [RFC6455] is 0x0d.

5.1.2.  Subprotocol Type

   The Subprotocol type (0x01) corresponds to the Sec-WebSocket-Protocol
   header of [RFC6455] Section 11.3.4.  It may appear any number of




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   times in the request preamble but MUST NOT appear more than once in
   the server preamble.

5.1.3.  Extensions Type

   The Extensions type (0x02) corresponds to the Sec-WebSocket-
   Extensions header of [RFC6455] Section 11.3.2.  It may appear any
   number of times in the request preamble.  The response preamble
   echoes the TLVs of the extensions selected.

5.1.4.  Origin Type

   The Origin type (0x03) corresponds to the Origin header defined by
   [RFC6454] and its use by [RFC6455].  Specifically this tuple MUST
   appear exactly once in a request preamble generated by a browser
   client and MAY appear once in requests from other clients.  It MUST
   NOT appear in response preambles.

5.1.5.  End-Preamble Type

   The End-Preamble type (0xff) MUST be the last TLS in the preamble and
   MUST appear one time.  It has a length of 0.

5.2.  Example



























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

                                            SETTINGS
                                            ENABLE_CONNECT_PROTOCOL = 1

   HEADERS + END_HEADERS
   :method = CONNECT
   :protocol = websocket
   :scheme = wss
   :path = /chat
   :authority = server.example.com:443

   DATA
   0xCA 0xA4 0x02 0x0A
   0x75 0x19 0x4D 0x49
   0x86 0x4E 0xA7 0x8F
   0x14 0x86 0xCF 0x08
   0x00 0x0001 0x0d
   0x01 0x0004 chat
   0x01 0x0009 superchat
   0x02 0x0012 permessage-deflate
   0x03 0x0016 http://www.example.com
   0xFF 0x0000

                                            HEADERS + END_HEADERS
                                            :status = 200

                                            DATA
                                            0xCA 0xA4 0x02 0x0A
                                            0x75 0x19 0x4D 0x49
                                            0x86 0x4E 0xA7 0x8F
                                            0x14 0x86 0xCF 0x08
                                            0x00 0x0001 0x0d
                                            0x01 0x0004 chat
                                            0xFF 0x0000

   DATA
   WebSocket Data

                                            DATA + END_STREAM
                                            WebSocket Data

   DATA + END_STREAM
   WebSocket Data







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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
   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 a entry for the HTTP/2 Settings Registry
   that was established by [RFC7540] Section 11.3

   Name: ENABLE_CONNECT_PROTOCOL

   Code: 0x8

   Initial Value: 0

   Specification: This document






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10.  Acknowledgments

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

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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6454]  Barth, A., "The Web Origin Concept", RFC 6454,
              DOI 10.17487/RFC6454, December 2011,
              <https://www.rfc-editor.org/info/rfc6454>.

   [RFC6455]  Fette, I. and A. Melnikov, "The WebSocket Protocol",
              RFC 6455, DOI 10.17487/RFC6455, December 2011,
              <https://www.rfc-editor.org/info/rfc6455>.

   [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,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/info/rfc7540>.

Author's Address

   Patrick McManus
   Mozilla

   Email: mcmanus@ducksong.com














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