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Fix redaction authentication (#5700)
Ensures that redactions are correctly authenticated for recent room versions. There are a few things going on here: * `_fetch_event_rows` is updated to return a dict rather than a list of rows. * Rather than returning multiple copies of an event which was redacted multiple times, it returns the redactions as a list within the dict. * It also returns the actual rejection reason, rather than merely the fact that it was rejected, so that we don't have to query the table again in `_get_event_from_row`. * The redaction handling is factored out of `_get_event_from_row`, and now checks if any of the redactions are valid.
This commit is contained in:
Richard van der Hoff
GitHub
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65c5592b8e
commit
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changelog.d/5700.bugfix
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2
changelog.d/5700.bugfix
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@ -0,0 +1,2 @@
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Fix some problems with authenticating redactions in recent room versions.
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@ -37,6 +37,7 @@ from synapse.logging.context import (
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)
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.types import get_domain_from_id
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from synapse.util import batch_iter
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from synapse.util.metrics import Measure
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from ._base import SQLBaseStore
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@ -240,27 +241,8 @@ class EventsWorkerStore(SQLBaseStore):
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# instead.
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if not allow_rejected and entry.event.type == EventTypes.Redaction:
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if entry.event.internal_metadata.need_to_check_redaction():
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# XXX: we need to avoid calling get_event here.
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#
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# The problem is that we end up at this point when an event
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# which has been redacted is pulled out of the database by
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# _enqueue_events, because _enqueue_events needs to check
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# the redaction before it can cache the redacted event. So
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# obviously, calling get_event to get the redacted event out
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# of the database gives us an infinite loop.
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#
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# For now (quick hack to fix during 0.99 release cycle), we
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# just go and fetch the relevant row from the db, but it
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# would be nice to think about how we can cache this rather
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# than hit the db every time we access a redaction event.
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#
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# One thought on how to do this:
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# 1. split get_events_as_list up so that it is divided into
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# (a) get the rawish event from the db/cache, (b) do the
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# redaction/rejection filtering
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# 2. have _get_event_from_row just call the first half of
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# that
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# XXX: we should probably use _get_events_from_cache_or_db here,
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# so that we can benefit from caching.
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orig_sender = yield self._simple_select_one_onecol(
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table="events",
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keyvalues={"event_id": entry.event.redacts},
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@ -410,19 +392,16 @@ class EventsWorkerStore(SQLBaseStore):
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The fetch requests. Each entry consists of a list of event
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ids to be fetched, and a deferred to be completed once the
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events have been fetched.
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"""
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with Measure(self._clock, "_fetch_event_list"):
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try:
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event_id_lists = list(zip(*event_list))[0]
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event_ids = [item for sublist in event_id_lists for item in sublist]
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rows = self._new_transaction(
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row_dict = self._new_transaction(
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conn, "do_fetch", [], [], self._fetch_event_rows, event_ids
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)
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row_dict = {r["event_id"]: r for r in rows}
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# We only want to resolve deferreds from the main thread
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def fire(lst, res):
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for ids, d in lst:
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@ -480,7 +459,7 @@ class EventsWorkerStore(SQLBaseStore):
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logger.debug("Loaded %d events (%d rows)", len(events), len(rows))
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if not allow_rejected:
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rows[:] = [r for r in rows if not r["rejects"]]
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rows[:] = [r for r in rows if r["rejected_reason"] is None]
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res = yield make_deferred_yieldable(
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defer.gatherResults(
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@ -489,8 +468,8 @@ class EventsWorkerStore(SQLBaseStore):
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self._get_event_from_row,
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row["internal_metadata"],
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row["json"],
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row["redacts"],
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rejected_reason=row["rejects"],
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row["redactions"],
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rejected_reason=row["rejected_reason"],
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format_version=row["format_version"],
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)
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for row in rows
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@ -501,49 +480,98 @@ class EventsWorkerStore(SQLBaseStore):
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defer.returnValue({e.event.event_id: e for e in res if e})
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def _fetch_event_rows(self, txn, events):
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rows = []
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N = 200
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for i in range(1 + len(events) // N):
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evs = events[i * N : (i + 1) * N]
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if not evs:
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break
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def _fetch_event_rows(self, txn, event_ids):
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"""Fetch event rows from the database
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Events which are not found are omitted from the result.
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The returned per-event dicts contain the following keys:
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* event_id (str)
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* json (str): json-encoded event structure
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* internal_metadata (str): json-encoded internal metadata dict
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* format_version (int|None): The format of the event. Hopefully one
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of EventFormatVersions. 'None' means the event predates
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EventFormatVersions (so the event is format V1).
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* rejected_reason (str|None): if the event was rejected, the reason
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why.
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* redactions (List[str]): a list of event-ids which (claim to) redact
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this event.
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Args:
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txn (twisted.enterprise.adbapi.Connection):
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event_ids (Iterable[str]): event IDs to fetch
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Returns:
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Dict[str, Dict]: a map from event id to event info.
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"""
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event_dict = {}
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for evs in batch_iter(event_ids, 200):
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sql = (
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"SELECT "
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" e.event_id as event_id, "
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" e.event_id, "
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" e.internal_metadata,"
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" e.json,"
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" e.format_version, "
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" r.redacts as redacts,"
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" rej.event_id as rejects "
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" rej.reason "
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" FROM event_json as e"
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" LEFT JOIN rejections as rej USING (event_id)"
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" LEFT JOIN redactions as r ON e.event_id = r.redacts"
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" WHERE e.event_id IN (%s)"
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) % (",".join(["?"] * len(evs)),)
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txn.execute(sql, evs)
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rows.extend(self.cursor_to_dict(txn))
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return rows
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for row in txn:
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event_id = row[0]
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event_dict[event_id] = {
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"event_id": event_id,
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"internal_metadata": row[1],
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"json": row[2],
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"format_version": row[3],
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"rejected_reason": row[4],
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"redactions": [],
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}
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# check for redactions
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redactions_sql = (
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"SELECT event_id, redacts FROM redactions WHERE redacts IN (%s)"
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) % (",".join(["?"] * len(evs)),)
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txn.execute(redactions_sql, evs)
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for (redacter, redacted) in txn:
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d = event_dict.get(redacted)
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if d:
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d["redactions"].append(redacter)
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return event_dict
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@defer.inlineCallbacks
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def _get_event_from_row(
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self, internal_metadata, js, redacted, format_version, rejected_reason=None
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self, internal_metadata, js, redactions, format_version, rejected_reason=None
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):
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"""Parse an event row which has been read from the database
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Args:
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internal_metadata (str): json-encoded internal_metadata column
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js (str): json-encoded event body from event_json
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redactions (list[str]): a list of the events which claim to have redacted
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this event, from the redactions table
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format_version: (str): the 'format_version' column
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rejected_reason (str|None): the reason this event was rejected, if any
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Returns:
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_EventCacheEntry
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"""
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with Measure(self._clock, "_get_event_from_row"):
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d = json.loads(js)
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internal_metadata = json.loads(internal_metadata)
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if rejected_reason:
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rejected_reason = yield self._simple_select_one_onecol(
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table="rejections",
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keyvalues={"event_id": rejected_reason},
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retcol="reason",
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desc="_get_event_from_row_rejected_reason",
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)
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if format_version is None:
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# This means that we stored the event before we had the concept
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# of a event format version, so it must be a V1 event.
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@ -555,41 +583,7 @@ class EventsWorkerStore(SQLBaseStore):
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rejected_reason=rejected_reason,
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)
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redacted_event = None
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if redacted:
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redacted_event = prune_event(original_ev)
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redaction_id = yield self._simple_select_one_onecol(
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table="redactions",
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keyvalues={"redacts": redacted_event.event_id},
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retcol="event_id",
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desc="_get_event_from_row_redactions",
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)
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redacted_event.unsigned["redacted_by"] = redaction_id
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# Get the redaction event.
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because = yield self.get_event(
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redaction_id, check_redacted=False, allow_none=True
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)
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if because:
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# It's fine to do add the event directly, since get_pdu_json
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# will serialise this field correctly
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redacted_event.unsigned["redacted_because"] = because
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# Starting in room version v3, some redactions need to be
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# rechecked if we didn't have the redacted event at the
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# time, so we recheck on read instead.
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if because.internal_metadata.need_to_check_redaction():
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expected_domain = get_domain_from_id(original_ev.sender)
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if get_domain_from_id(because.sender) == expected_domain:
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# This redaction event is allowed. Mark as not needing a
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# recheck.
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because.internal_metadata.recheck_redaction = False
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else:
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# Senders don't match, so the event isn't actually redacted
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redacted_event = None
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redacted_event = yield self._maybe_redact_event_row(original_ev, redactions)
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cache_entry = _EventCacheEntry(
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event=original_ev, redacted_event=redacted_event
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@ -599,6 +593,56 @@ class EventsWorkerStore(SQLBaseStore):
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defer.returnValue(cache_entry)
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@defer.inlineCallbacks
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def _maybe_redact_event_row(self, original_ev, redactions):
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"""Given an event object and a list of possible redacting event ids,
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determine whether to honour any of those redactions and if so return a redacted
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event.
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Args:
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original_ev (EventBase):
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redactions (iterable[str]): list of event ids of potential redaction events
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Returns:
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Deferred[EventBase|None]: if the event should be redacted, a pruned
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event object. Otherwise, None.
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"""
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redaction_map = yield self._get_events_from_cache_or_db(redactions)
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for redaction_id in redactions:
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redaction_entry = redaction_map.get(redaction_id)
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if not redaction_entry:
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# we don't have the redaction event, or the redaction event was not
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# authorized.
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continue
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redaction_event = redaction_entry.event
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# Starting in room version v3, some redactions need to be
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# rechecked if we didn't have the redacted event at the
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# time, so we recheck on read instead.
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if redaction_event.internal_metadata.need_to_check_redaction():
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expected_domain = get_domain_from_id(original_ev.sender)
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if get_domain_from_id(redaction_event.sender) == expected_domain:
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# This redaction event is allowed. Mark as not needing a recheck.
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redaction_event.internal_metadata.recheck_redaction = False
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else:
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# Senders don't match, so the event isn't actually redacted
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continue
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# we found a good redaction event. Redact!
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redacted_event = prune_event(original_ev)
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redacted_event.unsigned["redacted_by"] = redaction_id
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# It's fine to add the event directly, since get_pdu_json
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# will serialise this field correctly
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redacted_event.unsigned["redacted_because"] = redaction_event
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return redacted_event
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# no valid redaction found for this event
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return None
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@defer.inlineCallbacks
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def have_events_in_timeline(self, event_ids):
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"""Given a list of event ids, check if we have already processed and
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