A JSON Meta Application Protocol (JMAP) Subprotocol for WebSocket
RFC 8887
Internet Engineering Task Force (IETF) K. Murchison
Request for Comments: 8887 Fastmail
Category: Standards Track August 2020
ISSN: 2070-1721
A JSON Meta Application Protocol (JMAP) Subprotocol for WebSocket
Abstract
This document defines a binding for the JSON Meta Application
Protocol (JMAP) over a WebSocket transport layer. The WebSocket
binding for JMAP provides higher performance than the current HTTP
binding for JMAP.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8887.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction
2. Conventions Used in This Document
3. Discovering Support for JMAP over WebSocket
4. JMAP Subprotocol
4.1. Authentication
4.2. Handshake
4.3. WebSocket Messages
4.3.1. Handling Invalid Data
4.3.2. JMAP Requests
4.3.3. JMAP Responses
4.3.4. JMAP Request-Level Errors
4.3.5. JMAP Push Notifications
4.4. Examples
5. Security Considerations
5.1. Connection Confidentiality and Integrity
5.2. Non-browser Clients
6. IANA Considerations
6.1. Registration of the WebSocket JMAP Subprotocol
7. References
7.1. Normative References
7.2. Informative References
Acknowledgments
Author's Address
1. Introduction
JMAP [RFC8620] over HTTP [RFC7235] 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, reauthenticating for every JMAP
API request may harm performance.
The WebSocket [RFC6455] 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. This binding supports JMAP API requests and responses,
with optional support for push notifications.
Furthermore, the WebSocket binding for JMAP can optionally compress
[RFC7692] both JMAP API requests and responses. 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.
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document uses the terminology defined in the core JMAP
specification [RFC8620].
3. Discovering Support for JMAP over WebSocket
The JMAP capabilities object is returned as part of the standard JMAP
Session object (see Section 2 of [RFC8620]). Servers supporting this
specification MUST add a property named
"urn:ietf:params:jmap:websocket" to the capabilities object. The
value of this property is an object that MUST contain the following
information on server capabilities:
* url: "String"
The wss-URI (see Section 3 of [RFC6455]) to use for initiating a
JMAP-over-WebSocket handshake (the "WebSocket URL endpoint"
colloquially).
* supportsPush: "Boolean"
This is true if the server supports push notifications over the
WebSocket, as described in Section 4.3.5.
Example:
"urn:ietf:params:jmap:websocket": {
"url": "wss://server.example.com/jmap/ws/",
"supportsPush": true
}
4. JMAP Subprotocol
The term WebSocket subprotocol refers to an application-level
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