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Versions: (draft-mcmanus-httpbis-h2-websockets)
00 01 02 03 04 05 06 07 RFC 8441
HTTP P. McManus
Internet-Draft Mozilla
Updates: 6455 (if approved) May 2, 2018
Intended status: Standards Track
Expires: November 3, 2018
Bootstrapping WebSockets with HTTP/2
draft-ietf-httpbis-h2-websockets-03
Abstract
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 3, 2018.
Copyright Notice
Copyright (c) 2018 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
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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 SETTINGS_ENABLE_CONNECT_PROTOCOL SETTINGS Parameter . . . 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 headers 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
specification.
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 SETTINGS_ENABLE_CONNECT_PROTOCOL SETTINGS Parameter
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.
A sender MUST NOT send a SETTINGS_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 SETTINGS_ENABLE_CONNECT_PROTOCOL parameter, a non-
supporting peer would detect a malformed request and generate a
stream error (Section 8.1.2.6 of [RFC7540]).
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 :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 8.1.2.3 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.
The HTTP/2 stream closure is also analogous to the TCP connection 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] Secion 7) error code.
5.1. Example
[[ From Client ]] [[ From Server ]]
SETTINGS
SETTINGS_ENABLE_CONNECT_PROTOCOL = 1
HEADERS + END_HEADERS
:method = CONNECT
:protocol = websocket
:scheme = https
:path = /chat
:authority = server.example.com
sec-websocket-protocol = chat, superchat
sec-websocket-extensions = permessage-deflate
sec-websocket-version = 13
origin = http://www.example.com
HEADERS + END_HEADERS
:status = 200
sec-websocket-protocol = chat
DATA
WebSocket Data
DATA + END_STREAM
WebSocket Data
DATA + END_STREAM
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
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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) 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].
Name: SETTINGS_ENABLE_CONNECT_PROTOCOL
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
complexity.
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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,
<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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