Internet DRAFT - draft-ietf-httpbis-h2-websockets
draft-ietf-httpbis-h2-websockets
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
draft-ietf-httpbis-h2-websockets-07
Abstract
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
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This Internet-Draft will expire on December 20, 2018.
Copyright Notice
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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 . . . . . . . . . . . . . . . . . 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
both.
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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
specification.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"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.
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]. 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 8.1.2.6 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
https://www.iana.org/assignments/http-upgrade-tokens/http-upgrade-
tokens.xhtml
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 8.1.2.3 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
transaction.
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
SETTINGS_ENABLE_CONNECT_[..] = 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
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
document.
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. 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>.
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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,
<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>.
[RFC8164] Nottingham, M. and M. Thomson, "Opportunistic Security for
HTTP/2", RFC 8164, DOI 10.17487/RFC8164, May 2017,
<https://www.rfc-editor.org/info/rfc8164>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Acknowledgments
The 2017 HTTP Workshop had a very productive discussion that helped
determine the key problem and acceptable level of solution
complexity.
Author's Address
Patrick McManus
Mozilla
Email: mcmanus@ducksong.com
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