JMAP K. Murchison
Internet-Draft FastMail
Intended status: Standards Track December 5, 2018
Expires: June 8, 2019
A JSON Meta Application Protocol (JMAP) Subprotocol for WebSocket
draft-ietf-jmap-websocket-00
Abstract
This document defines a binding for the JSON Meta Application
Protocol (JMAP) over a WebSocket transport layer. A WebSocket
binding for JMAP provides higher performance than the current HTTP
binding for JMAP.
Open Issues
o What mechanism should be used to allow the client to choose what
types of objects for which is wishes to receive push notifications
over the WS connection? Shoul this be done via a new method type
or can it be done with header fields and/or query parameters on
the WS handshake?
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
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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 June 8, 2019.
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
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(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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Discovering Support for JMAP over WebSocket . . . . . . . . . 3
4. JMAP Subprotocol . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Handshake . . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. WebSocket Messages . . . . . . . . . . . . . . . . . . . 4
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. Registration of the WebSocket JMAP Subprotocol . . . . . 9
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
8.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
JMAP over HTTP requires that every JMAP API request be authenticated.
Depending on the type of authentication used by the JMAP client and
the configuration of the JMAP server, authentication could be an
expensive operation both in time and resources. In such
circumstances, authenticating every JMAP API request may harm
performance.
The WebSocket binding for JMAP eliminates this performance hit by
authenticating just the WebSocket handshake request and having those
credentials remain in effect for the duration of the WebSocket
connection.
Furthermore, the WebSocket binding for JMAP can optionally compress
[RFC7692] JMAP API requests. Although compression of HTTP responses
is ubiquitous, compression of HTTP requests has very low, if any
deployment, and therefore isn't a viable option for JMAP API requests
over HTTP.
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2. Conventions Used in This Document
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 [1] [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The same terminology is used in this document as in the core JMAP
specification.
3. Discovering Support for JMAP over WebSocket
The capabilities object is returned as part of the standard JMAP
Session object (see Section 2 of [I-D.ietf-jmap-core]). Servers
supporting this specification MUST add a property called
"urn:ietf:params:jmap:websocket" to the capabilities object. The
value of this property is an object which MUST contain the following
information on server capabilities:
wsUrl: "String" The URL to use for JMAP over WebSocket.
4. JMAP Subprotocol
The term WebSocket subprotocol refers to an application-level
protocol layered on top of a WebSocket connection. This document
specifies the WebSocket JMAP subprotocol for carrying JMAP API
requests, responses, and push notifications through a WebSocket
connection. Binary data MUST NOT be uploaded or downloaded through a
WebSocket JMAP connection.
4.1. Handshake
The JMAP WebSocket client and JMAP WebSocket server negotiate the use
of the WebSocket JMAP subprotocol during the WebSocket handshake,
either via a HTTP/1.1 Upgrade request (see Section 1.3 of [RFC6455])
or a HTTP/2 Extended CONNECT request (see Section 5 of [RFC8441]).
Regardless of the method used for the WebSocket handshake, the client
MUST make an authenticated [RFC7235] HTTP request on the JMAP 'wsURL'
(Section 3), and the client MUST include the value 'jmap' in the list
of protocols for the 'Sec-WebSocket-Protocol' header field. The
reply from the server MUST also contain 'jmap' in its corresponding
'Sec-WebSocket-Protocol' header field in order for a JMAP subprotocol
connection to be established.
If a client receives a handshake response that does not include
'jmap' in the 'Sec-WebSocket-Protocol' header, then a JMAP
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subprotocol WebSocket connection was not established and the client
MUST close the WebSocket connection.
Once the handshake has successfully completed, the WebSocket
connection is established and can be used for JMAP API requests,
responses, and push notifications. Any other message types MUST NOT
be transmitted over this connection.
The credentials used for authenticating the HTTP request to initiate
the handshake remain in effect for the duration of the WebSocket
connection.
4.2. WebSocket Messages
Data frame messages in the JMAP subprotocol MUST be of the text type
and contain UTF-8 encoded data. The messages MUST be in the form of
a single JMAP Request object (see Section 3.2 of
[I-D.ietf-jmap-core]) when sent from the client to the server, and in
the form of a single JMAP Response object, JSON Problem Details
object, or JMAP StateChange object (see Sections 3.3, 3.5.1, and 7.1
respectively of [I-D.ietf-jmap-core]) when sent from the server to
the client.
4.2.1. JMAP Requests
JMAP over WebSocket allows out of order processing of requests,
thereby requiring a mechanism for the client to correlate requests
and responses.
To this end, this specification adds one extra argument to the
request object:
o *id*: "String" (default: ) A client-specified identifier for the
request.
Additionally, the "maxConcurrentRequests" field in the "capabilities"
object (see Section 2 of [I-D.ietf-jmap-core]) limits the number of
inflight requests over the WebSocket.
4.2.2. JMAP Responses
This specification adds two extra arguments to the Response object:
o *@type*: "String" A string having value "Response" to identify the
JSON object as a JMAP Response.
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o *requestId*: "String|null" The client-specified identifier in the
corresponding request. If "null", no identifier was provided in
the request.
4.2.3. JMAP Request-level Errors
This specification adds two extra arguments to the Problem Details
object:
o *@type*: "String" A string having value "RequestError" to identify
the JSON object as a JSON Problem Details object.
o *requestId*: "String|null" The client-specified identifier in the
corresponding request. If "null", no identifier was provided in
the request.
4.2.4. JMAP Push Notifications
This specification adds one extra argument to the StateChange object:
o *@type*: "String" A string having value "StateChange" to identify
the JSON object as a JMAP StateChange object.
4.3. Examples
The following examples show WebSocket JMAP opening handshakes, a JMAP
Core/echo request and response, and a subsequent closing handshake.
The examples assume that the JMAP 'wsURL' has been advertised in the
JMAP Session object as '/jmap/ws/'. Note that folding of header
fields is for editorial purposes only.
WebSocket JMAP connection via HTTP/1.1:
[[ From Client ]] [[ From Server ]]
GET /jmap/ws/ HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Authorization: Basic Zm9vOmJhcg==
Sec-WebSocket-Key:
dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Protocol: jmap
Sec-WebSocket-Version: 13
Origin: http://www.example.com
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
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Connection: Upgrade
Sec-WebSocket-Accept:
s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: jmap
[WebSocket connection established]
WS_DATA
{
"id": "R1",
"using": [ "urn:ietf:params:jmap:core" ],
"methodCalls": [
[
"Core/echo", {
"hello": true,
"high": 5
},
"b3ff"
]
]
}
WS_DATA
{
"@type": "Response",
"requestId": "R1",
"methodResponses": [
[
"Core/echo", {
"hello": true,
"high": 5
},
"b3ff"
]
]
}
WS_DATA
The quick brown fox jumps
over the lazy dog.
WS_DATA
{
"@type": "RequestError",
"requestId": "null",
"type":
"urn:ietf:params:jmap:error:notJSON",
"status": 400,
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"detail":
"The request did not parse as I-JSON."
}
WS_DATA
{
"@type": "StateChange",
"changed": {
"a123": {
"Mailbox": "0af7a512ce70",
}
}
}
WS_CLOSE
WS_CLOSE
[WebSocket connection closed]
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WebSocket JMAP connection on a HTTP/2 stream which also negotiates
compression [RFC7692]:
[[ From Client ]] [[ From Server ]]
SETTINGS
SETTINGS_ENABLE_CONNECT_PROTOCOL = 1
HEADERS + END_HEADERS
:method = CONNECT
:protocol = websocket
:scheme = https
:path = /jmap/
:authority = server.example.com
authorization = Basic Zm9vOmJhcg==
sec-websocket-protocol = jmap
sec-websocket-version = 13
sec-websocket-extensions =
permessage-deflate
origin = http://www.example.com
HEADERS + END_HEADERS
:status = 200
sec-websocket-protocol = jmap
sec-websocket-extensions =
permessage-deflate
[WebSocket connection established]
DATA
WS_DATA
[compressed text]
DATA
WS_DATA
[compressed text]
...
DATA + END_STREAM
WS_CLOSE
DATA + END_STREAM
WS_CLOSE
[WebSocket connection closed]
[HTTP/2 stream closed]
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5. Security Considerations
The security considerations for both WebSocket (see Section 10 of
[RFC6455]) and JMAP (see Section 8 of [I-D.ietf-jmap-core]) apply to
the WebSocket JMAP subprotocol.
6. IANA Considerations
6.1. Registration of the WebSocket JMAP Subprotocol
This specification requests IANA to register the WebSocket JMAP
subprotocol under the "WebSocket Subprotocol Name" Registry with the
following data:
Subprotocol Identifier: JMAP
Subprotocol Common Name: WebSocket Transport for JMAP (JSON Meta
Application Protocol)
Subprotocol Definition: RFCXXXX (this document)
7. Acknowledgments
The author would like to thank the following individuals for
contributing their ideas and support for writing this specification:
Neil Jenkins and Robert Mueller.
8. References
8.1. Normative References
[I-D.ietf-jmap-core]
Jenkins, N. and C. Newman, "JSON Meta Application
Protocol", draft-ietf-jmap-core-12 (work in progress),
December 2018.
[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>.
[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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[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<https://www.rfc-editor.org/info/rfc7235>.
[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>.
[RFC8441] McManus, P., "Bootstrapping WebSockets with HTTP/2",
RFC 8441, DOI 10.17487/RFC8441, September 2018,
<https://www.rfc-editor.org/info/rfc8441>.
8.2. Informative References
[I-D.ietf-jmap-mail]
Jenkins, N. and C. Newman, "JMAP for Mail", draft-ietf-
jmap-mail-12 (work in progress), December 2018.
[RFC7692] Yoshino, T., "Compression Extensions for WebSocket",
RFC 7692, DOI 10.17487/RFC7692, December 2015,
<https://www.rfc-editor.org/info/rfc7692>.
8.3. URIs
[1] https://tools.ietf.org/html/bcp14
Appendix A. Change History (To be removed by RFC Editor before
publication)
Changes since murchison-02:
o Renamed as a JMAP WG document.
o Allow out of order processing.
o Allow push notifications.
o Modified examples.
o Add Security Considerations text.
o Minor Editorial changes.
Changes since murchison-01:
o Updated WebSocket over HTTP/2 reference to RFC8144.
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Changes since murchison-00:
o Fleshed out section on discovery of support for JMAP over
WebSocket.
o Allow JSON Problem Details objects to be returned by the server
for toplevel errors.
o Mentioned the ability to compress JMAP API requests.
o Minor Editorial changes.
Author's Address
Kenneth Murchison
FastMail US LLC
1429 Walnut Street - Suite 1201
Philadelphia, PA 19102
USA
Email: murch@fastmailteam.com
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