This commit introduces a verification step at the relay connection
level, to help ensure notes get validated at the source and prevent
security issues associated with untrusted relays.
`RelayConnection.swift` — the source that initially handles WebSocket
messages — was analyzed, and measures were put in place to prevent
(or at least minimize) unverified nostr event data being spread
throughout the app.
The following measures were taken:
1. A note verification step was added prior to the `self.handleEvent(.nostr_event(ev))` call (which sends a Nostr response to the rest of the app for logical handling).
a. From code analysis, there is only one such call in `RelayConnection.swift`.
2. `NostrConnectionEvent`, the object that gets passed to event handlers, had its interface modified to remove the "message" case, since:
a. that could be a source of unverified nostr events.
b. it is redundant an unneeded due to the `.nostr_event` case.
c. there were no usages of it around the codebase
3. The raw websocket event handler had its label renamed to "handleUnverifiedWSEvent", to make it clear to the caller about the verification status of the data.
a. Usages of this were inspected and no significant risk was detected.
4. A new `verify` method in NdbNote was created to verify Nostr notes, and unit tests were added to confirm tampering detections around all the major fields in a Nostr note.
5. Care was taken to ensure the performance regression is as little as
possible.
It is worth noting that we will not need this once the local relay model
architecture is introduced, since that architecture ensures note
validation before it reaches the rest of the application and the user.
In other words, this is a temporary fix.
However, since the migration to that new architecture is a major
undertaking that will take some time to be completed, this fix was written
in order to address security concerns while the migration is unfinished.
This fix was written in a way that attempts to be as effective as
possible in reducing security risks without a risky and lenghty
refactor of the code that would delay the fix from being published.
Changelog-Fixed: Improved security around note validation
Closes: https://github.com/damus-io/damus/issues/1341
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
4570ba797c