JMAP K. Murchison Internet-Draft Fastmail Intended status: Standards Track March 19, 2020 Expires: September 20, 2020 A JSON Meta Application Protocol (JMAP) Subprotocol for WebSocket draft-ietf-jmap-websocket-07 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 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 September 20, 2020. Copyright Notice Copyright (c) 2020 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. Murchison Expires September 20, 2020 [Page 1] Internet-Draft JMAP Over WebSocket March 2020 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. Authentication . . . . . . . . . . . . . . . . . . . . . 4 4.2. Handshake . . . . . . . . . . . . . . . . . . . . . . . . 4 4.3. WebSocket Messages . . . . . . . . . . . . . . . . . . . 5 4.3.1. Handling Invalid Data . . . . . . . . . . . . . . . . 5 4.3.2. JMAP Requests . . . . . . . . . . . . . . . . . . . . 5 4.3.3. JMAP Responses . . . . . . . . . . . . . . . . . . . 6 4.3.4. JMAP Request-Level Errors . . . . . . . . . . . . . . 6 4.3.5. JMAP Push Notifications . . . . . . . . . . . . . . . 6 4.4. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 5.1. Connection Confidentiality and Integrity . . . . . . . . 12 5.2. Non-Browser Clients . . . . . . . . . . . . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6.1. Registration of the WebSocket JMAP Subprotocol . . . . . 12 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . 14 Appendix A. Change History (To be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 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. Murchison Expires September 20, 2020 [Page 2] Internet-Draft JMAP Over WebSocket March 2020 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. The same terminology is used in this document as in the core JMAP specification. 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 which MUST contain the following information on server capabilities: o url: "String" The wss-URI (see Section 3 of [RFC6455]) to use for initiating a JMAP over WebSocket handshake (the "WebSocket URL endpoint" colloquially). o 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 protocol layered on top of a WebSocket connection. This document specifies the WebSocket JMAP subprotocol for carrying JMAP API requests, responses, and optional push notifications through a WebSocket connection. Binary data is handled per Section 6 of [RFC8620] via a separate HTTP connection or stream. Murchison Expires September 20, 2020 [Page 3] Internet-Draft JMAP Over WebSocket March 2020 4.1. Authentication A JMAP WebSocket connection is authenticated by presenting a user's credentials in the HTTP request [RFC7235] that initiates the WebSocket handshake. See Section 8.2 of [RFC8620] for recommendations regarding the selection of HTTP authentication schemes. 4.2. 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 4 of [RFC6455]) or a HTTP/2 Extended CONNECT request (see Section 5 of [RFC8441]). The WebSocket JMAP subprotocol is also intended to run over future bindings of HTTP (e.g. HTTP/3) provided that there is a defined mechanism for performing a WebSocket handshake over that binding. Regardless of the method used for the WebSocket handshake, the client MUST first perform a TLS handshake on a JMAP WebSocket URL endpoint (Section 3) having the "wss://" scheme (WebSocket over TLS) in accordance with the requirements of running the particular binding of HTTP over TLS (see [RFC2818] and Section 4.1 of [RFC6455] for HTTP/1.1 and Section 9.2 of [RFC7540] for HTTP/2). If the TLS handshake fails, the client MUST close the connection. Otherwise, the client MUST make an authenticated [RFC7235] HTTP request on the encrypted connection, and 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 a corresponding "Sec- WebSocket-Protocol" header field with a value of "jmap" in order for a JMAP subprotocol connection to be established. Once the handshake has successfully completed, the WebSocket connection is established and can be used for JMAP API requests, responses, and optional push notifications. 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. If the authentication credentials for the user expire, the server can either treat subsequent requests as if they are unauthenticated or close the WebSocket connection. In the latter case, the server MAY send a Close frame with a status code of 1008 (Policy Violation) as defined in Section 7.4.1 of [RFC6455]. Murchison Expires September 20, 2020 [Page 4] Internet-Draft JMAP Over WebSocket March 2020 4.3. WebSocket Messages Data frame messages in the JMAP subprotocol MUST be text frames and contain UTF-8 encoded data. The messages MUST be in the form of a single JMAP Request object (see Section 3.3 of [RFC8620]), JMAP WebSocketPushEnable object (see Section 4.3.5.2), or JMAP WebSocketPushDisable object (see Section 4.3.5.3) 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 3.4, 3.6.1, and 7.1 respectively of [RFC8620]) when sent from the server to the client. Note that fragmented WebSocket messages (split over multiple text frames) MUST be coalesced prior to parsing them as JSON objects. 4.3.1. Handling Invalid Data If a client or server receives a binary frame, the endpoint can either ignore the frame or close the WebSocket connection. In the latter case, the endpoint MAY send a Close frame with a status code of 1003 (Unsupported Data) as defined in Section 7.4.1 of [RFC6455]. If a client receives a message that is not in the form of either a JSON Problem Details object, a JMAP Response object, or a JMAP StateChange object, the client can either ignore the message or close the WebSocket connection. In the latter case, the endpoint MAY send a Close frame with a status code of 1007 (Invalid frame payload data Data) as defined in Section 7.4.1 of [RFC6455]. A server MUST return an appropriate JSON Problem Details object (Section 4.3.4) for any request-level errors (E.g. an invalid JMAP object, an unsupported capability or method call, or exceeding a server request limit). 4.3.2. JMAP Requests The specification extends the Request object with two additional arguments when used over a WebSocket: o @type: "String" This MUST be the string "Request". o id: "String" (optional) A client-specified identifier for the request to be echoed back in the response to this request. Murchison Expires September 20, 2020 [Page 5] Internet-Draft JMAP Over WebSocket March 2020 JMAP over WebSocket allows the server to process requests out of order. The client-specified identifier is used as a mechanism for the client to correlate requests and responses. Additionally, the "maxConcurrentRequests" limit in the "capabilities" object (see Section 2 of [RFC8620]) also applies to requests made on the WebSocket connection. When using the WebSocket JMAP subprotocol over a binding of HTTP that allows multiplexing of requests (e.g. HTTP/2), this limit applies to the the sum of requests made on both the JMAP API endpoint and the WebSocket connection. 4.3.3. JMAP Responses The specification extends the Response object with two additional arguments when used over a WebSocket: o @type: "String" This MUST be the string "Response". o requestId: "String" (optional; MUST be returned if an id is included in the request) The client-specified identifier in the corresponding request. 4.3.4. JMAP Request-Level Errors The specification extends the Problem Details object for request- level errors (see Section 3.6.1 of [RFC8620]) with two additional arguments when used over a WebSocket: o @type: "String" This MUST be the string "RequestError". o requestId: "String" (optional; MUST be returned if given in the request) The client-specified identifier in the corresponding request. 4.3.5. JMAP Push Notifications JMAP over WebSocket servers that support push notifications on the WebSocket will advertise a "supportsPush" property with a value of true in the "urn:ietf:params:jmap:websocket" server capabilities object. Murchison Expires September 20, 2020 [Page 6] Internet-Draft JMAP Over WebSocket March 2020 4.3.5.1. Notification Format All push notifications take the form of a standard StateChange object (see Section 7.1 of [RFC8620]). The specification extends the StateChange object with one additional argument when used over a WebSocket: o pushState: "String" (optional) A (preferably short) string that encodes the entire server state visible to the user (not just the objects returned in this call). The purpose of the "pushState" token is to allow a client to immediately get any changes that occurred while is was disconnected (see Section 4.3.5.2). If the server does not support "pushState" tokens, the client will have issue a series of "/changes" requests (see Section 5.2 of [RFC8620]) upon reconnection to update its state to match that of the server. 4.3.5.2. Enabling Notifications A client enables push notifications from the server for the current connection by sending a WebSocketPushEnable object to the server. A WebSocketPushEnable object has the following properties: o @type: "String" This MUST be the string "WebSocketPushEnable". o dataTypes: "String[]|null" A list of data type names (e.g. "Mailbox", "Email") that the client is interested in. A StateChange notification will only be sent if the data for one of these types changes. Other types are omitted from the TypeState object. If null, changes will be pushed for all supported data types. o pushState: "String" (optional) The last "pushState" token that the client received from the server. Upon receipt of a "pushState" token, the server SHOULD immediately send all changes since that state token. Murchison Expires September 20, 2020 [Page 7] Internet-Draft JMAP Over WebSocket March 2020 4.3.5.3. Disabling Notifications A client disables push notifications from the server for the current connection by sending a WebSocketPushDisable object to the server. A WebSocketPushDisable object has the following property: o @type: "String" This MUST be the string "WebSocketPushDisable". 4.4. 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 WebSocket URL endpoint has been advertised in the JMAP Session object as having a path of "/jmap/ws/" and that TLS negotiation has already succeeded. Note that folding of header fields is for editorial purposes only. WebSocket JMAP connection via HTTP/1.1 with push notifications for mail [RFC8621] enabled. This example assumes that the client has cached pushState "aaa" from a previous connection. [[ 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: https://www.example.com HTTP/1.1 101 Switching Protocols Upgrade: websocket Connection: Upgrade Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo= Sec-WebSocket-Protocol: jmap [WebSocket connection established] WS_DATA { "@type": "WebSocketPushEnable", Murchison Expires September 20, 2020 [Page 8] Internet-Draft JMAP Over WebSocket March 2020 "dataTypes": [ "Mailbox", "Email" ], "pushState": "aaa" } WS_DATA { "@type": "StateChange", "changed": { "a456": { "Mailbox": "d35ecb040aab" } }, "pushState": "bbb" } WS_DATA { "@type": "Request", "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 Murchison Expires September 20, 2020 [Page 9] Internet-Draft JMAP Over WebSocket March 2020 over the lazy dog. WS_DATA { "@type": "RequestError", "requestId": null, "type": "urn:ietf:params:jmap:error:notJSON", "status": 400, "detail": "The request did not parse as I-JSON." } [A new email is received] WS_DATA { "@type": "StateChange", "changed": { "a123": { "Email": "0af7a512ce70" } } "pushState": "ccc" } WS_CLOSE WS_CLOSE [WebSocket connection closed] Murchison Expires September 20, 2020 [Page 10] Internet-Draft JMAP Over WebSocket March 2020 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/ws/ :authority = server.example.com origin: https://example.com authorization = Basic Zm9vOmJhcg== sec-websocket-protocol = jmap sec-websocket-version = 13 sec-websocket-extensions = permessage-deflate origin = https://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] Murchison Expires September 20, 2020 [Page 11] Internet-Draft JMAP Over WebSocket March 2020 5. Security Considerations The security considerations for both WebSocket (see Section 10 of [RFC6455]) and JMAP (see Section 8 of [RFC8620]) apply to the WebSocket JMAP subprotocol. Specific security considerations are described in subsections of this section. 5.1. Connection Confidentiality and Integrity To ensure the confidentiality and integrity of data sent and received via JMAP over WebSocket, the WebSocket connection MUST use TLS 1.2 [RFC5246] or later, following the recommendations in BCP 195 [RFC7525]. Servers SHOULD support TLS 1.3 [RFC8446] or later. 5.2. Non-Browser Clients JMAP over WebSocket can be used by clients both running inside and outside of a web browser. As such, the security considerations in Sections 10.2 and 10.1 of [RFC6455] apply to those respective environments. 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, Robert Mueller, and Chris Newman. 8. References Murchison Expires September 20, 2020 [Page 12] Internet-Draft JMAP Over WebSocket March 2020 8.1. 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, . [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, DOI 10.17487/RFC2818, May 2000, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC 6455, DOI 10.17487/RFC6455, December 2011, . [RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Authentication", RFC 7235, DOI 10.17487/RFC7235, June 2014, . [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2015, . [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI 10.17487/RFC7540, May 2015, . [RFC7692] Yoshino, T., "Compression Extensions for WebSocket", RFC 7692, DOI 10.17487/RFC7692, December 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8441] McManus, P., "Bootstrapping WebSockets with HTTP/2", RFC 8441, DOI 10.17487/RFC8441, September 2018, . Murchison Expires September 20, 2020 [Page 13] Internet-Draft JMAP Over WebSocket March 2020 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [RFC8620] Jenkins, N. and C. Newman, "The JSON Meta Application Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July 2019, . 8.2. Informative References [RFC8621] Jenkins, N. and C. Newman, "The JSON Meta Application Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621, August 2019, . Appendix A. Change History (To be removed by RFC Editor before publication) Changes since ietf-06: o Removed open issue on security of WebSocket compression, per Alexey Melnikov. Changes since ietf-05: o Renamed "webSocketUrl" to "url" and "supportsWebSocketPush" to "supportsPush", per Benjamin Schwartz. o Added a security subsection with a nod to Sections 10.1 and 10.2 of RFC6455, per Leif Johansson. o Clarified "unsupported JMAP" vs "unsupported JSON", per Benjamin Kaduk. o Refer to RFC 7525 as BCP 195, per Benjamin Kaduk. o Several editorial improvements from Benjamin Kaduk. o Several editorial improvements from Murray Kucherawy. Changes since ietf-04: o Require the use of TLS for JMAP over WebSocket (per Alissa Cooper and others). o Added a section explaining how to handle unsupported messages (per Bob Briscoe). Murchison Expires September 20, 2020 [Page 14] Internet-Draft JMAP Over WebSocket March 2020 o Added a section specifically addressing authentication of the WebSocket (per Leif Johansson). o Corrected references into specific sections of RFC 8620 (per Martin Vigoureax). o Made RFC 7692 a normative reference (per Barry Leiba). o Clarified that the "maxConcurrentRequests" limit applies to the sum of all requests on the current connection (per Benjamin Kaduk). o Clarified that the "pushState" token represents the entire server state visible to the user (per Banjamin Kaduk). o Clarified that "WebSocketPushEnable/Disable" only effect the current connection (per Benjamin Kaduk). o Several editorial improvements from Benjamin Kaduk. Changes since ietf-03: o Updated JMAP Mail reference to RFC 8621. o Specified that requestId MUST be present in a response if given in the request. Changes since ietf-02: o Updated JMAP Core reference to RFC 8620. o Added 'WebSocketPushDisable' object. o Editorial and formatting changes. Changes since ietf-01: o Changed 'wsURL' to 'webSocketUrl' and removed push query option. o Added 'supportsWebSocketPush' capability. o Added '@type' argument to Request object. o Added 'WebSocketPushEnable' object. o Added 'pushState' argument to StateChange object. o Updated example. Murchison Expires September 20, 2020 [Page 15] Internet-Draft JMAP Over WebSocket March 2020 o Minor Editorial changes. Changes since ietf-00: o Added text describing advertisement of and selection of optional push notifications. o Minor Editorial changes. 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. 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 Murchison Expires September 20, 2020 [Page 16] Internet-Draft JMAP Over WebSocket March 2020 Kenneth Murchison Fastmail US LLC 1429 Walnut Street - Suite 1201 Philadelphia, PA 19102 USA Email: murch@fastmailteam.com URI: http://www.fastmail.com/ Murchison Expires September 20, 2020 [Page 17]