Matrix Message Format
draft-ralston-mimi-matrix-message-format-00
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| Document | Type |
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| Authors | Travis Ralston , Matthew Hodgson | ||
| Last updated | 2022-11-06 | ||
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draft-ralston-mimi-matrix-message-format-00
More Instant Messaging Interoperability T. Ralston
Internet-Draft M. Hodgson
Intended status: Informational The Matrix.org Foundation C.I.C.
Expires: 10 May 2023 6 November 2022
Matrix Message Format
draft-ralston-mimi-matrix-message-format-00
Abstract
This document specifies a message format using Matrix for messaging
interoperability.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://turt2live.github.io/ietf-mimi-matrix-message-format/draft-
ralston-mimi-matrix-message-format.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-
ralston-mimi-matrix-message-format/.
Discussion of this document takes place on the More Instant Messaging
Interoperability Working Group mailing list (mailto:mimi@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/mimi/.
Subscribe at https://www.ietf.org/mailman/listinfo/mimi/.
Source for this draft and an issue tracker can be found at
https://github.com/turt2live/ietf-mimi-matrix-message-format.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 10 May 2023.
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Copyright Notice
Copyright (c) 2022 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Matrix Events . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Encryption . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Interoperable instant messaging requires a common format for all
participants to contribute to the conversation or state of the room.
Matrix is an open protocol for interoperable, decentralized, secure
communication, and alongside its existing transport functionality
[TODO: Link to draft-ralston-mimi-matrix-transport], defines a rich
taxonomy of arbitrarily extensible payloads of information called
"events" to carry information between machines and users, which may
in turn be layered over end-to-end encryption. Matrix events have
been designed for interoperability from the outset between
heterogenous messaging platforms, and define a real-world highest-
common denominator set of message types, including:
* Instant messages (plain & rich text)
* End-to-end encrypted payloads
* File transfer
* Reactions (emoji, textual, image-based)
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* Edits
* Replies
* Deletions
* Stickers
* Custom emoji
* Voice messages
* Polls
* Static location share
* Live location share (ephemeral)
* Live location share (persistent)
* Spoiler text
* Threaded messages
* Typing notifications
* Read receipts
* Read-up-to markers
* Presence
* 1:1 VoIP signalling
* Multiparty VoIP signalling
Matrix events are extensible, and proposals exist for additional
event formats ranging from attaching 3D world geometry to
conversations (for openly standardized metaverse communication)
through to transferring healthcare data (FHIR).
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2. Matrix Events
Events are JSON objects which by default follow the formal schemas
defined in the Matrix Client Server API [MxEvents], also available as
JSON Schema definitions [MxEventsSchema]. Events are extensible and
may contain additional off-schema prefixed fields, or use prefixed
event types not yet defined in the spec. Events then get augumented
and signed by the server before being forwarded to other servers/
users in the room.
These JSON objects have a few key fields:
* type: A string the client can use to determine how to render the
event. This is reverse-DNS namespaced, with m. as a privileged
prefix for event types formally adopted and defined within the
Matrix specification.
* sender: The user ID (@alice:example.org) which sent the event.
* room_id: The room ID (!room:example.org) for where the event was
sent.
* content: Type-specific JSON object.
* Other fields (TODO: define these in detail when more relevant to
the doc).
Under MSC1767 [MSC1767] (a spec change proposal in the existing
Matrix open standard ecosystem), callers can combine together
multiple event types to provide fallback representations of an event,
to provide backwards compatibility when rendering unknown event
types.
An example of a simple text message would be:
{
"type": "m.message",
"content": {
"m.text": "i am a fish",
"m.html": "i am a <strong>fish</strong>"
}
}
This can be made more complex if the sender chooses to mix in other
mimetypes:
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{
"type": "m.message",
"content": {
"m.message": [
{ "mimetype": "text/html", "body": "i am a <strong>fish</strong>" },
{ "mimetype": "text/plain", "body": "i am a fish" },
{ "mimetype": "application/vnd.exampleorg.message+html", "body": "<content>i am a <strong>fish</strong></content>" }
]
}
}
To demonstrate extensibility, a file upload [MSC3551] might look
like:
{
"type": "m.file",
"content": {
"m.text": "Upload: foo.pdf https://example.org/_matrix/media/v3/download/example.org/abcd1234 (12 KB)",
"m.file": {
"url": "mxc://example.org/abcd1234",
"name": "foo.pdf",
"mimetype": "application/pdf",
"size": 12345
}
}
}
In this example, clients which do not understand m.file but do
understand m.text (or m.message) would show just the plain text
instead of a download button. The alternative to falling back would
be to hide the unrenderable event, causing the conversation history
to be fragmented: this has clear negative consequences on user
experience. Instead, by defining a fallback mechanism the user is
still able to participate in the conversation, though might need to
ask for more information. It is expected that the "base types" (text
messages, images, videos, and generic files) would be supported by
all clients to ensure there are sufficient building blocks for future
extensibility.
A more complete use-case for extensible events is described by
"MSC3381: Polls" [MSC3381] - clients which do not yet have support
for polls can present their users with text fallback for the question
and the question asker can manually tally up "improper" responses (if
those users simply sent text messages in response to the question).
Clients which do support polls would simply show the poll and its
question/options for the user to click on - their response would be
sent to the room as a (deliberately) unrenderable event for other
clients to tally up automatically.
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3. Encryption
Matrix has specified an encryption algorithm for events called
Megolm, however for the purposes of MIMI it would be desirable to
adopt MLS [I-D.ietf-mls-protocol] instead. Some bookkeeping changes
are required to support MLS in a decentralized environment like
Matrix: those are currently defined by [DMLS].
4. Security Considerations
TODO Security. Future drafts should consider the encryption aspects
in particular.
5. References
5.1. Normative References
[I-D.ietf-mls-protocol]
Barnes, R., Beurdouche, B., Robert, R., Millican, J.,
Omara, E., and K. Cohn-Gordon, "The Messaging Layer
Security (MLS) Protocol", Work in Progress, Internet-
Draft, draft-ietf-mls-protocol-16, 11 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-mls-
protocol-16>.
[MSC1767] Hodgson, M. and T. Ralston, "Extensible event types &
fallback in Matrix (v2)", 2022, <https://github.com/
matrix-org/matrix-spec-
proposals/blob/d6046d8402e7a3c7a4fcbc9da16ea9bad5968992/
proposals/1767-extensible-events.md>.
[MSC3551] Ralston, T., "Extensible Events - Files", 2021,
<https://github.com/matrix-org/matrix-spec-
proposals/blob/5bf2118e8ac873e7845b1eedde8dd7bc187ed673/
proposals/3551-extensible-events-files.md>.
[MxEvents] The Matrix.org Foundation C.I.C., "Events | Client-Server
API", 2022,
<https://spec.matrix.org/v1.4/client-server-api/#events>.
[MxEventsSchema]
The Matrix.org Foundation C.I.C., "Matrix Event JSON
Schemas", 2022, <https://github.com/matrix-org/matrix-
spec/tree/main/data/event-schemas/schema>.
5.2. Informative References
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[DMLS] Chathi, H., "Decentralised MLS", Web
https://gitlab.matrix.org/matrix-org/mls-ts/-
/blob/dd57bc25f6145ddedfb6d193f6baebf5133db7ed/
decentralised.org, 2021, <https://gitlab.matrix.org/
matrix-org/mls-ts/-
/blob/dd57bc25f6145ddedfb6d193f6baebf5133db7ed/
decentralised.org>.
[MSC3381] Ralston, T., "Polls (mk II)", 2022, <https://github.com/
matrix-org/matrix-spec-
proposals/blob/95fdc44b904d2b4d2f227db99050e539e43f3509/
proposals/3381-polls.md>.
Acknowledgments
TODO acknowledge.
Authors' Addresses
Travis Ralston
The Matrix.org Foundation C.I.C.
Email: travisr@matrix.org
Matthew Hodgson
The Matrix.org Foundation C.I.C.
Email: matthew@matrix.org
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