You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
394 lines
18 KiB
ReStructuredText
394 lines
18 KiB
ReStructuredText
.. Copyright 2016 OpenMarket Ltd
|
|
..
|
|
.. Licensed under the Apache License, Version 2.0 (the "License");
|
|
.. you may not use this file except in compliance with the License.
|
|
.. You may obtain a copy of the License at
|
|
..
|
|
.. http://www.apache.org/licenses/LICENSE-2.0
|
|
..
|
|
.. Unless required by applicable law or agreed to in writing, software
|
|
.. distributed under the License is distributed on an "AS IS" BASIS,
|
|
.. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
.. See the License for the specific language governing permissions and
|
|
.. limitations under the License.
|
|
|
|
.. contents:: Table of Contents
|
|
.. sectnum::
|
|
|
|
.. Note that this file is specifically unversioned because we don't want to
|
|
.. have to add Yet Another version number, and the commentary on what specs we
|
|
.. have should hopefully not get complex enough that we need to worry about
|
|
.. versioning it.
|
|
|
|
Introduction
|
|
------------
|
|
.. WARNING::
|
|
The Matrix specification is still evolving: the APIs are not yet frozen
|
|
and this document is in places a work in progress or stale. We have made every
|
|
effort to clearly flag areas which are still being finalised.
|
|
We're publishing it at this point because it's complete enough to be more than
|
|
useful and provide a canonical reference to how Matrix is evolving. Our end
|
|
goal is to mirror WHATWG's `Living Standard
|
|
<https://whatwg.org/faq?#living-standard>`_.
|
|
|
|
Matrix is a set of open APIs for open-federated Instant Messaging (IM), Voice
|
|
over IP (VoIP) and Internet of Things (IoT) communication, designed to create
|
|
and support a new global real-time communication ecosystem. The intention is to
|
|
provide an open decentralised pubsub layer for the internet for securely
|
|
persisting and publishing/subscribing JSON objects. This specification is the
|
|
ongoing result of standardising the APIs used by the various components of the
|
|
Matrix ecosystem to communicate with one another.
|
|
|
|
The principles that Matrix attempts to follow are:
|
|
|
|
- Pragmatic Web-friendly APIs (i.e. JSON over REST)
|
|
- Keep It Simple & Stupid
|
|
|
|
+ provide a simple architecture with minimal third-party dependencies.
|
|
|
|
- Fully open:
|
|
|
|
+ Fully open federation - anyone should be able to participate in the global
|
|
Matrix network
|
|
+ Fully open standard - publicly documented standard with no IP or patent
|
|
licensing encumbrances
|
|
+ Fully open source reference implementation - liberally-licensed example
|
|
implementations with no IP or patent licensing encumbrances
|
|
|
|
- Empowering the end-user
|
|
|
|
+ The user should be able to choose the server and clients they use
|
|
+ The user should be control how private their communication is
|
|
+ The user should know precisely where their data is stored
|
|
|
|
- Fully decentralised - no single points of control over conversations or the
|
|
network as a whole
|
|
- Learning from history to avoid repeating it
|
|
|
|
+ Trying to take the best aspects of XMPP, SIP, IRC, SMTP, IMAP and NNTP
|
|
whilst trying to avoid their failings
|
|
|
|
|
|
The functionality that Matrix provides includes:
|
|
|
|
- Creation and management of fully distributed chat rooms with no
|
|
single points of control or failure
|
|
- Eventually-consistent cryptographically secure synchronisation of room
|
|
state across a global open network of federated servers and services
|
|
- Sending and receiving extensible messages in a room with (optional)
|
|
end-to-end encryption
|
|
- Extensible user management (inviting, joining, leaving, kicking, banning)
|
|
mediated by a power-level based user privilege system.
|
|
- Extensible room state management (room naming, aliasing, topics, bans)
|
|
- Extensible user profile management (avatars, display names, etc)
|
|
- Managing user accounts (registration, login, logout)
|
|
- Use of 3rd Party IDs (3PIDs) such as email addresses, phone numbers,
|
|
Facebook accounts to authenticate, identify and discover users on Matrix.
|
|
- Trusted federation of Identity servers for:
|
|
|
|
+ Publishing user public keys for PKI
|
|
+ Mapping of 3PIDs to Matrix IDs
|
|
|
|
|
|
The end goal of Matrix is to be a ubiquitous messaging layer for synchronising
|
|
arbitrary data between sets of people, devices and services - be that for
|
|
instant messages, VoIP call setups, or any other objects that need to be
|
|
reliably and persistently pushed from A to B in an interoperable and federated
|
|
manner.
|
|
|
|
Architecture
|
|
------------
|
|
|
|
Matrix defines APIs for synchronising extensible JSON objects known as
|
|
"events" between compatible clients, servers and services. Clients are
|
|
typically messaging/VoIP applications or IoT devices/hubs and communicate by
|
|
synchronising communication history with their "homeserver" using the
|
|
"Client-Server API". Each homeserver stores the communication history and
|
|
account information for all of its clients, and shares data with the wider
|
|
Matrix ecosystem by synchronising communication history with other homeservers
|
|
and their clients.
|
|
|
|
Clients typically communicate with each other by emitting events in the
|
|
context of a virtual "room". Room data is replicated across *all of the
|
|
homeservers* whose users are participating in a given room. As such, *no
|
|
single homeserver has control or ownership over a given room*. Homeservers
|
|
model communication history as a partially ordered graph of events known as
|
|
the room's "event graph", which is synchronised with eventual consistency
|
|
between the participating servers using the "Server-Server API". This process
|
|
of synchronising shared conversation history between homeservers run by
|
|
different parties is called "Federation". Matrix optimises for the the
|
|
Availability and Partitioned properties of CAP theorem at
|
|
the expense of Consistency.
|
|
|
|
For example, for client A to send a message to client B, client A performs an
|
|
HTTP PUT of the required JSON event on its homeserver (HS) using the
|
|
client-server API. A's HS appends this event to its copy of the room's event
|
|
graph, signing the message in the context of the graph for integrity. A's HS
|
|
then replicates the message to B's HS by performing an HTTP PUT using the
|
|
server-server API. B's HS authenticates the request, validates the event's
|
|
signature, authorises the event's contents and then adds it to its copy of the
|
|
room's event graph. Client B then receives the message from his homeserver via
|
|
a long-lived GET request.
|
|
|
|
::
|
|
|
|
How data flows between clients
|
|
==============================
|
|
|
|
{ Matrix client A } { Matrix client B }
|
|
^ | ^ |
|
|
| events | Client-Server API | events |
|
|
| V | V
|
|
+------------------+ +------------------+
|
|
| |---------( HTTPS )--------->| |
|
|
| homeserver | | homeserver |
|
|
| |<--------( HTTPS )----------| |
|
|
+------------------+ Server-Server API +------------------+
|
|
History Synchronisation
|
|
(Federation)
|
|
|
|
|
|
Users
|
|
~~~~~
|
|
|
|
Each client is associated with a user account, which is identified in Matrix
|
|
using a unique "user ID". This ID is namespaced to the homeserver which
|
|
allocated the account and has the form::
|
|
|
|
@localpart:domain
|
|
|
|
See the `appendices <appendices.html#identifier-grammar>`_ for full details of
|
|
the structure of user IDs.
|
|
|
|
Devices
|
|
~~~~~~~
|
|
|
|
The Matrix specification has a particular meaning for the term "device". As a
|
|
user, I might have several devices: a desktop client, some web browsers, an
|
|
Android device, an iPhone, etc. They broadly relate to a real device in the
|
|
physical world, but you might have several browsers on a physical device, or
|
|
several Matrix client applications on a mobile device, each of which would be
|
|
its own device.
|
|
|
|
Devices are used primarily to manage the keys used for end-to-end encryption
|
|
(each device gets its own copy of the decryption keys), but they also help
|
|
users manage their access - for instance, by revoking access to particular
|
|
devices.
|
|
|
|
When a user first uses a client, it registers itself as a new device. The
|
|
longevity of devices might depend on the type of client. A web client will
|
|
probably drop all of its state on logout, and create a new device every time
|
|
you log in, to ensure that cryptography keys are not leaked to a new user. In
|
|
a mobile client, it might be acceptable to reuse the device if a login session
|
|
expires, provided the user is the same.
|
|
|
|
Devices are identified by a ``device_id``, which is unique within the scope of
|
|
a given user.
|
|
|
|
A user may assign a human-readable display name to a device, to help them
|
|
manage their devices.
|
|
|
|
Events
|
|
~~~~~~
|
|
|
|
All data exchanged over Matrix is expressed as an "event". Typically each client
|
|
action (e.g. sending a message) correlates with exactly one event. Each event
|
|
has a ``type`` which is used to differentiate different kinds of data. ``type``
|
|
values MUST be uniquely globally namespaced following Java's `package naming
|
|
conventions`_, e.g.
|
|
``com.example.myapp.event``. The special top-level namespace ``m.`` is reserved
|
|
for events defined in the Matrix specification - for instance ``m.room.message``
|
|
is the event type for instant messages. Events are usually sent in the context
|
|
of a "Room".
|
|
|
|
.. _package naming conventions: https://en.wikipedia.org/wiki/Java_package#Package_naming_conventions
|
|
|
|
Event Graphs
|
|
~~~~~~~~~~~~
|
|
|
|
.. _sect:event-graph:
|
|
|
|
Events exchanged in the context of a room are stored in a directed acyclic graph
|
|
(DAG) called an "event graph". The partial ordering of this graph gives the
|
|
chronological ordering of events within the room. Each event in the graph has a
|
|
list of zero or more "parent" events, which refer to any preceding events
|
|
which have no chronological successor from the perspective of the homeserver
|
|
which created the event.
|
|
|
|
Typically an event has a single parent: the most recent message in the room at
|
|
the point it was sent. However, homeservers may legitimately race with each
|
|
other when sending messages, resulting in a single event having multiple
|
|
successors. The next event added to the graph thus will have multiple parents.
|
|
Every event graph has a single root event with no parent.
|
|
|
|
To order and ease chronological comparison between the events within the graph,
|
|
homeservers maintain a ``depth`` metadata field on each event. An event's
|
|
``depth`` is a positive integer that is strictly greater than the depths of any
|
|
of its parents. The root event should have a depth of 1. Thus if one event is
|
|
before another, then it must have a strictly smaller depth.
|
|
|
|
Room structure
|
|
~~~~~~~~~~~~~~
|
|
|
|
A room is a conceptual place where users can send and receive events. Events are
|
|
sent to a room, and all participants in that room with sufficient access will
|
|
receive the event. Rooms are uniquely identified internally via "Room IDs",
|
|
which have the form::
|
|
|
|
!opaque_id:domain
|
|
|
|
There is exactly one room ID for each room. Whilst the room ID does contain a
|
|
domain, it is simply for globally namespacing room IDs. The room does NOT
|
|
reside on the domain specified.
|
|
|
|
See the `appendices <appendices.html#identifier-grammar>`_ for full details of
|
|
the structure of a room ID.
|
|
|
|
The following conceptual diagram shows an
|
|
``m.room.message`` event being sent to the room ``!qporfwt:matrix.org``::
|
|
|
|
{ @alice:matrix.org } { @bob:domain.com }
|
|
| ^
|
|
| |
|
|
[HTTP POST] [HTTP GET]
|
|
Room ID: !qporfwt:matrix.org Room ID: !qporfwt:matrix.org
|
|
Event type: m.room.message Event type: m.room.message
|
|
Content: { JSON object } Content: { JSON object }
|
|
| |
|
|
V |
|
|
+------------------+ +------------------+
|
|
| homeserver | | homeserver |
|
|
| matrix.org | | domain.com |
|
|
+------------------+ +------------------+
|
|
| ^
|
|
| [HTTP PUT] |
|
|
| Room ID: !qporfwt:matrix.org |
|
|
| Event type: m.room.message |
|
|
| Content: { JSON object } |
|
|
`-------> Pointer to the preceding message ------`
|
|
PKI signature from matrix.org
|
|
Transaction-layer metadata
|
|
PKI Authorization header
|
|
|
|
...................................
|
|
| Shared Data |
|
|
| State: |
|
|
| Room ID: !qporfwt:matrix.org |
|
|
| Servers: matrix.org, domain.com |
|
|
| Members: |
|
|
| - @alice:matrix.org |
|
|
| - @bob:domain.com |
|
|
| Messages: |
|
|
| - @alice:matrix.org |
|
|
| Content: { JSON object } |
|
|
|...................................|
|
|
|
|
Federation maintains *shared data structures* per-room between multiple home
|
|
servers. The data is split into ``message events`` and ``state events``.
|
|
|
|
Message events:
|
|
These describe transient 'once-off' activity in a room such as an
|
|
instant messages, VoIP call setups, file transfers, etc. They generally
|
|
describe communication activity.
|
|
|
|
State events:
|
|
These describe updates to a given piece of persistent information
|
|
('state') related to a room, such as the room's name, topic, membership,
|
|
participating servers, etc. State is modelled as a lookup table of key/value
|
|
pairs per room, with each key being a tuple of ``state_key`` and ``event type``.
|
|
Each state event updates the value of a given key.
|
|
|
|
The state of the room at a given point is calculated by considering all events
|
|
preceding and including a given event in the graph. Where events describe the
|
|
same state, a merge conflict algorithm is applied. The state resolution
|
|
algorithm is transitive and does not depend on server state, as it must
|
|
consistently select the same event irrespective of the server or the order the
|
|
events were received in. Events are signed by the originating server (the
|
|
signature includes the parent relations, type, depth and payload hash) and are
|
|
pushed over federation to the participating servers in a room, currently using
|
|
full mesh topology. Servers may also request backfill of events over federation
|
|
from the other servers participating in a room.
|
|
|
|
|
|
Room Aliases
|
|
++++++++++++
|
|
|
|
Each room can also have multiple "Room Aliases", which look like::
|
|
|
|
#room_alias:domain
|
|
|
|
See the `appendices <appendices.html#identifier-grammar>`_ for full details of
|
|
the structure of a room alias.
|
|
|
|
A room alias "points" to a room ID and is the human-readable label by which
|
|
rooms are publicised and discovered. The room ID the alias is pointing to can
|
|
be obtained by visiting the domain specified. Note that the mapping from a room
|
|
alias to a room ID is not fixed, and may change over time to point to a
|
|
different room ID. For this reason, Clients SHOULD resolve the room alias to a
|
|
room ID once and then use that ID on subsequent requests.
|
|
|
|
When resolving a room alias the server will also respond with a list of servers
|
|
that are in the room that can be used to join via.
|
|
|
|
::
|
|
|
|
HTTP GET
|
|
#matrix:domain.com !aaabaa:matrix.org
|
|
| ^
|
|
| |
|
|
_______V____________________|____
|
|
| domain.com |
|
|
| Mappings: |
|
|
| #matrix >> !aaabaa:matrix.org |
|
|
| #golf >> !wfeiofh:sport.com |
|
|
| #bike >> !4rguxf:matrix.org |
|
|
|________________________________|
|
|
|
|
Identity
|
|
~~~~~~~~
|
|
|
|
Users in Matrix are identified via their Matrix user ID. However,
|
|
existing 3rd party ID namespaces can also be used in order to identify Matrix
|
|
users. A Matrix "Identity" describes both the user ID and any other existing IDs
|
|
from third party namespaces *linked* to their account.
|
|
Matrix users can *link* third-party IDs (3PIDs) such as email addresses, social
|
|
network accounts and phone numbers to their user ID. Linking 3PIDs creates a
|
|
mapping from a 3PID to a user ID. This mapping can then be used by Matrix
|
|
users in order to discover the user IDs of their contacts.
|
|
In order to ensure that the mapping from 3PID to user ID is genuine, a globally
|
|
federated cluster of trusted "Identity Servers" (IS) are used to verify the 3PID
|
|
and persist and replicate the mappings.
|
|
|
|
Usage of an IS is not required in order for a client application to be part of
|
|
the Matrix ecosystem. However, without one clients will not be able to look up
|
|
user IDs using 3PIDs.
|
|
|
|
|
|
Profiles
|
|
~~~~~~~~
|
|
|
|
Users may publish arbitrary key/value data associated with their account - such
|
|
as a human readable display name, a profile photo URL, contact information
|
|
(email address, phone numbers, website URLs etc).
|
|
|
|
.. TODO
|
|
Actually specify the different types of data - e.g. what format are display
|
|
names allowed to be?
|
|
|
|
Private User Data
|
|
~~~~~~~~~~~~~~~~~
|
|
|
|
Users may also store arbitrary private key/value data in their account - such as
|
|
client preferences, or server configuration settings which lack any other
|
|
dedicated API. The API is symmetrical to managing Profile data.
|
|
|
|
.. TODO
|
|
Would it really be overengineered to use the same API for both profile &
|
|
private user data, but with different ACLs?
|
|
|
|
License
|
|
-------
|
|
|
|
The Matrix specification is licensed under the `Apache License, Version 2.0
|
|
<http://www.apache.org/licenses/LICENSE-2.0>`_.
|