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document device list synchronisation over federation.

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untested
closes MSC1212
matthew/device_list_update
Matthew Hodgson 6 years ago
parent d789564db7
commit 30d56691b1
3 changed files with 215 additions and 0 deletions
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89
api/server-server/definitions/event-schemas/m.device_list_update.yaml
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# Copyright 2018 New Vector 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.
type: object
title: m.device_list_update
description: |-
An EDU that lets servers push details to each other when one of their users
adds a new device to their account, required for E2E encryption to correctly
target the current set of devices for a given user.
# FIXME: It's very unclear why we have this API surface for synchronising
# device lists, rather than just using a room (which could also be used for
# presence lists, profile info, etc). But documenting what we have for now...
allOf:
- $ref: ../edu.yaml
- type: object
properties:
edu_type:
type: enum
enum: ['m.device_list_update']
description: The string ``m.device_list_update``
example: "m.device_list_update"
content:
type: object
description: The description of the device whose details has changed
title: Device List Update
properties:
user_id:
type: string
description: The user ID who owns this device
example: "@john:example.com"
device_id:
type: string
description: The ID of the device whose details are changing
example: "QBUAZIFURK"
device_display_name:
type: string
description: |-
The public human-readable name of this device. Will be absent
if the device has no name
example: "Mobile"
stream_id:
type: integer
description: |-
An ID sent by the server for this update, unique for a given
user_id. Used to identify any gaps in the sequence of m.device_list_update
EDUs broadcast by a server.
example: 6
prev_id:
type: array
description: |-
The stream_ids of any prior m.device_list_update EDUs sent for this user
which have not been referred to already in an EDU's prev_id field. If the
receiving server does not recognise any of the prev_ids, it means an EDU
has been lost and the server should query a snapshot of the devicelist
via /user/keys/query in order to correctly interpret future m.device_list_update
EDUs. May be missing or empty for the first EDU in a sequence.
items:
type: integer
description: |-
The stream_id of a prior EDU in this sequence which has not been referred
to already in an EDU's prev_id field.
example: 5
deleted:
type: boolean
description: |-
True if the server is announcing that this device has been deleted.
keys:
description: |-
The updated identity keys (if any) for this device. May be absent if the
device has no E2E keys defined.
allOf:
- $ref: definitions/device_keys.yaml
required:
- user_id
- device_id
- stream_id

84
api/server-server/user_devices.yaml
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# Copyright 2018 New Vector 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.
swagger: '2.0'
info:
title: "Matrix Federation User Device Management API"
version: "1.0.0"
host: localhost:8448
schemes:
- https
basePath: /_matrix/federation/v1
consumes:
- application/json
produces:
- application/json
securityDefinitions:
$ref: definitions/security.yaml
paths:
"/user/devices/{userId}":
get:
summary: Gets all of the user's devices
description: Gets information on all of the user's devices
operationId: getUserDevices
security:
- signedRequest: []
parameters:
- in: path
name: userId
type: string
required: true
description: |-
The user ID to retrieve devices for. Must be a user local to the
receiving homeserver.
required: true
x-example: "@alice:example.org"
responses:
200:
description: The user's devices.
schema:
type: object
properties:
user_id:
type: string
description: The user ID devices were requested for.
example: "@alice:example.org"
stream_id:
type: integer
description: |-
An ID the requesting homeserver may use to detect changes in the
device list. This should increase as time goes on, and always
produce the same ``devices`` list if not incremented.
example: 334608
devices:
type: array
description: The user's devices. May be empty.
items:
type: object
title: User Device
properties:
device_id:
type: string
description: The device ID.
example: "JLAFKJWSCS"
keys:
type: object
description: Identity keys for the device.
$ref: "../client-server/definitions/device_keys.yaml"
device_display_name:
type: string
description: Optional display name for the device.
example: "Alice's Mobile Phone"
required: ['device_id', 'keys']
required: ['user_id', 'stream_id', 'devices']

42
specification/server_server_api.rst
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{{openid_ss_http_api}}
Device Management
-----------------
Details of a user's devices must be efficiently published to other users and kept
up-to-date. This is critical for reliable end-to-end encryption, in order for users
to know which devices are participating in a room. It's also required for to-device
messaging to work. This section is intended to complement the `Device Management module`_
of the Client-Server API.
Matrix currently uses a custom pubsub system for synchronising information
about the list of devices for a given user over federation. When a server
wishes to determine a remote user's device list for the first time,
it should populate its local cache by calling the /user/keys/query API
on the remote server. However, subsequent updates to the cache should be applied
by consuming ``m.device_list_update`` EDUs, which must be sent by the remote server
whenever a user's device list changes.
Servers send ``m.device_list_update`` EDUs in a sequence per source user, each with
a unique ``stream_id``. They also include a pointer to the most recent previous EDU(s)
that this update is relative to in the `pprev_id`` field. To simplify implementation
for clustered servers which could send multiple EDUs at the same time, the ``prev_id``
field should include all ``m.device_list_update`` EDUs which have not been yet been
referenced in a EDU. If EDUs are emitted in series by a server, there should only ever
be one ``prev_id`` in the EDU.
This forms a simple directed acyclic graph of ``m.device_list_update`` EDUs, showing
which EDUs a server needs to have received in order to apply an update to its local
copy of the remote user's device list. If a server receives an EDU which refers to
a ``prev_id`` it does not recognise, it must resynchronise its list by calling the
/user/keys/query API and resume the process.
..TODO: how do you synchronise the result of the /query API with the stream_id
in the EDUs?
..TODO: this whole thing desperately feels like it should just be state in a room,
rather than inventing a whole different DAG. The same room could be used for
profiles, presence lists, etc.
{{user_devices_ss_http_api}}
{{definition_ss_event_schemas_m_device_list_update}}
End-to-End Encryption
---------------------

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