Bootstrapping WebSockets with HTTP/2
draft-mcmanus-httpbis-h2-websockets-01
| The information below is for an old version of the document |
| Document |
Type |
|
Active Internet-Draft (individual)
|
|
Author |
|
Patrick McManus
|
|
Last updated |
|
2017-10-26
|
|
Replaced by |
|
RFC 8441, RFC 8441
|
|
Stream |
|
(None)
|
|
Formats |
|
pdf
htmlized
bibtex
|
| Stream |
Stream state |
|
(No stream defined) |
|
Consensus Boilerplate |
|
Unknown
|
|
RFC Editor Note |
|
(None)
|
| IESG |
IESG state |
|
I-D Exists
|
|
Telechat date |
|
|
|
Responsible AD |
|
(None)
|
|
Send notices to |
|
(None)
|
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
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 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
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.
McManus Expires April 29, 2018 [Page 1]
Internet-Draft I-D October 2017
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
McManus Expires April 29, 2018 [Page 2]
Internet-Draft I-D October 2017
(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:
McManus Expires April 29, 2018 [Page 3]
Internet-Draft I-D October 2017
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.
McManus Expires April 29, 2018 [Page 4]
Internet-Draft I-D October 2017
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
McManus Expires April 29, 2018 [Page 5]
Internet-Draft I-D October 2017
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
McManus Expires April 29, 2018 [Page 6]
Internet-Draft I-D October 2017
[[ 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
McManus Expires April 29, 2018 [Page 7]
Internet-Draft I-D October 2017
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
McManus Expires April 29, 2018 [Page 8]
Internet-Draft I-D October 2017
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
McManus Expires April 29, 2018 [Page 9]