|
|
|
|
# Mass redactions
|
|
|
|
|
Matrix, like any platform with public chat rooms, has spammers. Currently,
|
|
|
|
|
redacting spam essentially requires spamming redaction events in a 1:1 ratio,
|
|
|
|
|
which is not optimal<sup>[1]</sup>. Most clients do not even have any mass
|
|
|
|
|
redaction tools, likely in part due to the lack of a mass redaction API. A mass
|
|
|
|
|
redaction API on the other hand has not been implemented as it would require
|
|
|
|
|
sending lots of events at once. However, this problem could be solved by
|
|
|
|
|
allowing a single redaction event to redact many events instead of sending many
|
|
|
|
|
redaction events.
|
|
|
|
|
|
|
|
|
|
## Proposal
|
|
|
|
|
This proposal builds upon [MSC2174] and suggests making the `redacts` field
|
|
|
|
|
in the content of `m.room.redaction` events an array of event ID strings
|
|
|
|
|
instead of a single event ID string.
|
|
|
|
|
|
|
|
|
|
It would be easiest to do this before MSC2174 is written into the spec, as then
|
|
|
|
|
only one migration would be needed: from an event-level redacts string to a
|
|
|
|
|
content-level redacts array.
|
|
|
|
|
|
|
|
|
|
### Number of redactions
|
|
|
|
|
Room v4+ event IDs are 44 bytes long, which means the federation event size
|
|
|
|
|
limit would cap a single redaction event at a bit less than 1500 targets.
|
|
|
|
|
Redactions are not intrinsically heavy, so a separate limit should not be
|
|
|
|
|
necessary.
|
|
|
|
|
|
|
|
|
|
### Client behavior
|
|
|
|
|
Clients shall apply existing `m.room.redaction` target behavior over an array
|
|
|
|
|
of event ID strings.
|
|
|
|
|
|
|
|
|
|
### Server behavior
|
|
|
|
|
The redaction auth rules should change to iterate the array and check if the
|
|
|
|
|
sender has the privileges to redact each event.
|
|
|
|
|
|
|
|
|
|
There are at least two potential ways to handle targets that are not found or
|
|
|
|
|
rejected: soft failing until all targets are found or handling each target
|
|
|
|
|
separately.
|
|
|
|
|
|
|
|
|
|
#### Soft fail
|
|
|
|
|
[Soft fail] the event until all targets are found, then accept only if the
|
|
|
|
|
sender has the privileges to redact every listed event. This is how redactions
|
|
|
|
|
currently work.
|
|
|
|
|
|
|
|
|
|
This has the downside of requiring servers to fetch all the target events (and
|
|
|
|
|
possibly forward them to clients) before being able to process and forward the
|
|
|
|
|
redaction event.
|
|
|
|
|
|
|
|
|
|
#### Handle each target separately
|
|
|
|
|
The target events of an `m.room.redaction` shall no longer be considered when
|
|
|
|
|
deciding the authenticity of an `m.room.redaction` event. Any other existing
|
|
|
|
|
rules remain unchanged.
|
|
|
|
|
|
|
|
|
|
When a server accepts an `m.room.redaction` using the modified auth rules, it
|
|
|
|
|
evaluates targets individually for authenticity under the existing auth rules.
|
|
|
|
|
Servers MUST NOT include failing and unknown entries to clients.
|
|
|
|
|
|
|
|
|
|
> Servers do not know whether redaction targets are authorized at the time they
|
|
|
|
|
receive the `m.room.redaction` unless they are in possession of the target
|
|
|
|
|
event. Implementations retain entries in the original list which were not
|
|
|
|
|
shared with clients to later evaluate the target's redaction status.
|
|
|
|
|
|
|
|
|
|
When the implementation receives a belated target from an earlier
|
|
|
|
|
`m.room.redaction`, it evaluates at that point whether the redaction is
|
|
|
|
|
authorized.
|
|
|
|
|
|
|
|
|
|
> Servers should not send belated target events to clients if their redaction
|
|
|
|
|
was found to be authentic, as clients were not made aware of the redaction.
|
|
|
|
|
That fact is also used to simply ignore unauthorized targets and send the
|
|
|
|
|
events to clients normally.
|
|
|
|
|
|
|
|
|
|
## Tradeoffs
|
|
|
|
|
|
|
|
|
|
## Potential issues
|
|
|
|
|
|
|
|
|
|
## Security considerations
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
[1]: https://img.mau.lu/hEqqt.png
|
|
|
|
|
[MSC2174]: https://github.com/matrix-org/matrix-doc/pull/2174
|
|
|
|
|
[Soft fail]: https://matrix.org/docs/spec/server_server/r0.1.3#soft-failure
|
