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.
78 lines
3.5 KiB
Markdown
78 lines
3.5 KiB
Markdown
# Update auth rules to check notifications key in m.room.power_levels
|
|
|
|
## Introduction
|
|
|
|
The key `notifications` was added to the `m.room.power_levels` event after the
|
|
finalisation of the auth rules specified in room version 1. This leads to the
|
|
fact, that this dictionary is not subject to the same validation as other
|
|
dictionaries in the event, such as `users` or `events`. This especially means
|
|
that Alice is able to alter any entry within the dictionary including ones,
|
|
that are above her own power level, which is inconsistent with the behaviour
|
|
for the other two dictionaries.
|
|
|
|
[m.room.power_levels](https://matrix.org/docs/spec/client_server/r0.5.0#m-room-power-levels)
|
|
[room version 1](https://matrix.org/docs/spec/rooms/v1)
|
|
|
|
## Proposal
|
|
|
|
The auth rules regarding `m.room.power_levels` have been established in room
|
|
version 1. The general idea here was that creators of a new `m.room.power_levels`
|
|
event are only able to make changes to something that is equal to or lower than
|
|
their own power level.
|
|
So, assuming a room with Alice (50), Bob (100), `m.room.power_levels` at 50,
|
|
`m.room.name` at 75 and `m.room.topic` at 25 would mean the following:
|
|
|
|
* Alice CAN alter `m.room.topic` to any power level up to her own, in this case 50
|
|
* Alice is NOT able to alter `m.room.name` since the current value is higher than
|
|
her own (75 > 50)
|
|
* Alice is NOT able to alter the power level of Bob, since his current value is
|
|
higher than her own (100 > 50)
|
|
* Alice is free to set the level for anything that has not been defined such as
|
|
`org.alice.message` up to a maximum of 50
|
|
|
|
Later on the key `notifications` was added to the `m.room.power_levels` event.
|
|
It contains a mapping of notification keys to a power level, that is required
|
|
for a user to trigger the specific notification. The most famous notification
|
|
type is the `@room` notification.
|
|
|
|
Going back to the original example because this key was added later on, the auth
|
|
rules make no mention of it, which enables the following behaviour. *It is assumed
|
|
that `@room` is at 75*
|
|
|
|
* Alice can add any key to the dictionary and set the value to any value she wants,
|
|
including ones higher than her own.
|
|
* Alice can alter the value for `@room` to any value she wants, including ones that
|
|
are higher than her own, even though her own value is lower.
|
|
|
|
The proposed solution is to alter the auth rules and add the `notifications` dictionary
|
|
to the same rules that handle `events` and `users`.
|
|
|
|
So the rule [10.d](https://matrix.org/docs/spec/rooms/v1.html) of the auth rules in
|
|
room version 1 would be updated in a new room version to:
|
|
|
|
|
|
> For each entry being added, changed or removed in events, users __and notifications__
|
|
>keys:
|
|
|
|
|
|
## Tradeoffs
|
|
|
|
The proposed solution would be a breaking change with current room versions and
|
|
the alternative would be to leave the `notifications` key without any checks.
|
|
|
|
## Security considerations
|
|
|
|
This is likely to improve security because it prevents malicious users that were
|
|
only given the right to emit `m.room.power_levels` so that they could alter a very
|
|
specific key, such as `invite`, from altering the rules established for triggering
|
|
notifications.
|
|
|
|
## Conclusion
|
|
|
|
The current spec conform behaviour regarding `notifications` is inconsistent with
|
|
behaviour shown by the other dictionaries and room administrators are very likely
|
|
expecting the `notifications` to work the same as them. The required change is minimal
|
|
is and also in line with the general spirit of the auth rules regarding the
|
|
`m.room.power_levels` event. A new room version is, however, required. This can be
|
|
done with other pending changes.
|