1894765 - Site hosts allowlisted from BTP never get removed from candidate list

Status: RESOLVED FIXED

(Core :: Privacy: Anti-Tracking, defect, P1)

Description

[Paul Zühlcke [:pbz]]

Sites that are on the content blocking allow list (ETP toggle) get skipped from purging. However skipping currently means they remain in the bounce tracker candidate map. They can remain there as long as they're allow-listed and we will never remove them unless the entire BTP storage gets cleared. See https://searchfox.org/mozilla-central/rev/f1532761de0b60337e42c6c3f525288a523dabef/toolkit/components/antitracking/bouncetrackingprotection/BounceTrackingProtection.cpp#617,627

Ideally we would not classify them to begin with in RecordStatefulBounces. Need to check if this check isn't too expensive to do.

Independently, need to keep the exception check in PurgeBounceTrackersForStateGlobal too for when a user exempts a site that has already been classified and is in the bounce tracker candidate map already. If we find a site that is allowlisted there we should remove it from the candidate list.

Comment 1

[Paul Zühlcke [:pbz]]

Attachment: Bug 1894765 - Remove bounce tracker from candidate list if it's allow-listed. r=bvandersloot,manuel

Removing it avoids an ever-growing list of candidates that don't ever get purged.
We could avoid adding it in the first place by adding a similar check in
BounceTrackingProtection::RecordStatefulBounces. However the permission check per base
domain is rather expensive (see ContentBlockingAllowListCache).
This behaviour is a compromise where we still may re-add allow-listed bounce trackers
to the candidate list before they are removed in the hourly PurgeBounceTrackers run.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/32d481a432de
Remove bounce tracker from candidate list if it's allow-listed. r=anti-tracking-reviewers,manuel

Comment 3

[tszentpeteri]

https://hg.mozilla.org/mozilla-central/rev/32d481a432de