fix(matrix): close 'hall of mirrors' pairing + echo loop (#15763) (#16374)

Harden the Matrix adapter's sender-drop guards so bot-self events and
appservice/bridge identities never reach the gateway's pairing flow or
the agent loop.

Two filters, applied as early as possible in _on_room_message (and
_on_reaction for the self-filter):

1. _is_self_sender(sender) — case-insensitive + whitespace-trimmed
   equality with self._user_id.  When self._user_id is still empty
   (whoami has not resolved, or login failed), returns True
   defensively: an unidentified bot dropping its own events is always
   preferable to falling into an echo loop.  The previous byte-for-byte
   equality check let differently-cased copies of the bot's MXID slip
   through, and an unresolved self-ID silently disabled the guard.

2. _is_system_or_bridge_sender(sender) — drops appservice namespace
   puppets (conventional @_bridge_...:server form) and malformed
   senders with an empty localpart.  These identities used to fall
   through to the gateway's unauthorized-user path, trigger a pairing
   code, and — once an operator approved the bridge — every outbound
   message the bridge relayed would loop back as an authorized user
   message.  This was the root of the 'hall of mirrors' symptom.

Fixes #15763

Test plan
---------
scripts/run_tests.sh tests/gateway/test_matrix.py
scripts/run_tests.sh tests/gateway/test_matrix_mention.py tests/gateway/test_matrix_voice.py
All 182 tests pass.  14 new regression tests cover exact / case-insensitive
/ whitespace / unresolved-self-id matches, bridge prefix detection, empty
sender, and the full _on_room_message drop path.
This commit is contained in:
Teknium
2026-04-26 21:50:28 -07:00
committed by GitHub
parent 4a2ee6c162
commit af3d5150c1
2 changed files with 216 additions and 3 deletions

View File

@@ -1178,13 +1178,83 @@ class MatrixAdapter(BasePlatformAdapter):
# Event callbacks
# ------------------------------------------------------------------
def _is_self_sender(self, sender: str) -> bool:
"""Return True if the sender refers to the bot's own account.
Matrix user IDs are byte-compared after trimming whitespace and
lowercasing — some homeservers normalize the localpart case
differently at different API surfaces, and the reply-loop tail
of the "hall of mirrors" bug (#15763) has been observed with the
bot's own account bypassing a case-sensitive equality check.
When ``self._user_id`` is empty (whoami hasn't resolved yet, or
login failed), we cannot prove a sender is NOT us, so we return
True defensively — an unidentified bot dropping its own events
is always preferable to falling into an echo loop.
"""
own = (self._user_id or "").strip().lower()
if not own:
return True
return sender.strip().lower() == own
@staticmethod
def _is_system_or_bridge_sender(sender: str) -> bool:
"""Return True if the sender looks like a system / bridge / appservice
identity rather than a real user.
Appservice namespaces on Matrix conventionally prefix bot / puppet
user IDs with an underscore (e.g. ``@_telegram_12345:server``,
``@_discord_999:server``, ``@_slack_...:server``). Server-notices
bots and bridge-controller bots on many homeservers use the same
pattern.
We treat these as system identities for pairing purposes: they
should never be offered a pairing code, because an operator
approving the code would hand the bridge itself permanent
authorization — and every outbound message relayed by the bridge
would then loop back into the agent as an "authorized user
message", which is the root of issue #15763.
Matches:
``@_something:server`` — appservice namespace convention
``@:server`` — malformed / empty localpart
``:server`` — malformed, no leading ``@``
"""
s = (sender or "").strip()
if not s:
return True
# Localpart is everything between leading '@' and ':'
if s.startswith("@"):
s = s[1:]
if ":" in s:
localpart, _, _ = s.partition(":")
else:
localpart = s
if not localpart:
return True
return localpart.startswith("_")
async def _on_room_message(self, event: Any) -> None:
"""Handle incoming room message events (text, media)."""
room_id = str(getattr(event, "room_id", ""))
sender = str(getattr(event, "sender", ""))
# Ignore own messages.
if sender == self._user_id:
# Ignore own messages (case-insensitive; also drops when our own
# user_id hasn't been resolved yet — see _is_self_sender docstring
# and issue #15763).
if self._is_self_sender(sender):
return
# Ignore appservice / bridge / system identities so they never
# trigger the pairing flow. Once a bridge user is paired, every
# outbound message it relays would loop back as an authorized
# user message (the "hall of mirrors" in #15763).
if self._is_system_or_bridge_sender(sender):
logger.debug(
"Matrix: ignoring system/bridge sender %s in %s",
sender,
room_id,
)
return
# Deduplicate by event ID.
@@ -1654,7 +1724,7 @@ class MatrixAdapter(BasePlatformAdapter):
async def _on_reaction(self, event: Any) -> None:
"""Handle incoming reaction events."""
sender = str(getattr(event, "sender", ""))
if sender == self._user_id:
if self._is_self_sender(sender):
return
event_id = str(getattr(event, "event_id", ""))
if self._is_duplicate_event(event_id):

View File

@@ -1956,3 +1956,146 @@ class TestMatrixPresence:
self.adapter._client = None
result = await self.adapter.set_presence("online")
assert result is False
# ---------------------------------------------------------------------------
# Self / bridge / system sender filtering — regression coverage for #15763
# ("Hall of Mirrors": recursive pairing / echo loops triggered by bridge
# or bot-self senders bypassing the early-drop guard in _on_room_message).
# ---------------------------------------------------------------------------
class TestMatrixSelfSenderFilter:
def setup_method(self):
self.adapter = _make_adapter()
def test_exact_match_is_self(self):
self.adapter._user_id = "@bot:example.org"
assert self.adapter._is_self_sender("@bot:example.org") is True
def test_case_insensitive_match_is_self(self):
# Some homeservers canonicalize the localpart differently at
# different API surfaces — a case-sensitive equality check lets
# the bot's own sender through and triggers the pairing / echo
# loop in #15763.
self.adapter._user_id = "@Bot:Example.ORG"
assert self.adapter._is_self_sender("@bot:example.org") is True
assert self.adapter._is_self_sender("@BOT:EXAMPLE.ORG") is True
def test_whitespace_trimmed(self):
self.adapter._user_id = "@bot:example.org"
assert self.adapter._is_self_sender(" @bot:example.org ") is True
def test_different_user_is_not_self(self):
self.adapter._user_id = "@bot:example.org"
assert self.adapter._is_self_sender("@alice:example.org") is False
def test_empty_user_id_is_treated_as_self(self):
# If whoami hasn't resolved yet (or login failed), we cannot
# prove a sender is NOT us. Defensively drop rather than leak
# our own outbound traffic into the agent loop.
self.adapter._user_id = ""
assert self.adapter._is_self_sender("@alice:example.org") is True
assert self.adapter._is_self_sender("") is True
class TestMatrixSystemBridgeFilter:
def setup_method(self):
self.adapter = _make_adapter()
def test_appservice_underscore_prefix_is_bridge(self):
# Conventional appservice namespace puppets
assert self.adapter._is_system_or_bridge_sender(
"@_telegram_12345:bridge.example.org"
) is True
assert self.adapter._is_system_or_bridge_sender(
"@_discord_999:example.org"
) is True
assert self.adapter._is_system_or_bridge_sender(
"@_slackbridge_puppet:example.org"
) is True
def test_empty_localpart_is_system(self):
assert self.adapter._is_system_or_bridge_sender("@:server.example") is True
def test_empty_sender_is_system(self):
assert self.adapter._is_system_or_bridge_sender("") is True
assert self.adapter._is_system_or_bridge_sender(" ") is True
def test_regular_user_is_not_bridge(self):
assert self.adapter._is_system_or_bridge_sender(
"@alice:example.org"
) is False
# A user whose localpart merely CONTAINS an underscore is not a
# bridge — the convention is a LEADING underscore.
assert self.adapter._is_system_or_bridge_sender(
"@alice_smith:example.org"
) is False
def test_bot_account_is_not_bridge(self):
# The Hermes bot itself (no leading underscore) must not be
# classified as a bridge — that filter is a pairing guard, not
# a self-filter.
assert self.adapter._is_system_or_bridge_sender(
"@daemon:nerdworks.casa"
) is False
class TestMatrixOnRoomMessageFilter:
"""End-to-end coverage of _on_room_message drop conditions."""
def setup_method(self):
self.adapter = _make_adapter()
self.adapter._user_id = "@bot:example.org"
self.adapter._startup_ts = 0.0 # accept any event_ts
self.adapter._handle_text_message = AsyncMock()
self.adapter._handle_media_message = AsyncMock()
@staticmethod
def _mk_event(sender, body="hi", msgtype="m.text", event_id=None, ts=None):
import time as _t
ev = MagicMock()
ev.room_id = "!room:example.org"
ev.sender = sender
ev.event_id = event_id or f"$evt-{sender}-{body}"
ev.timestamp = int((ts or _t.time()) * 1000)
ev.server_timestamp = ev.timestamp
ev.content = {"msgtype": msgtype, "body": body}
return ev
@pytest.mark.asyncio
async def test_own_sender_case_insensitive_dropped(self):
# Simulate whoami returning a differently-cased copy of our MXID.
self.adapter._user_id = "@Bot:Example.ORG"
ev = self._mk_event(sender="@bot:example.org")
await self.adapter._on_room_message(ev)
self.adapter._handle_text_message.assert_not_called()
@pytest.mark.asyncio
async def test_bridge_sender_dropped_before_pairing(self):
ev = self._mk_event(sender="@_telegram_12345:bridge.example.org")
await self.adapter._on_room_message(ev)
# Bridge / appservice identities must never flow through to the
# gateway — otherwise they trigger pairing (#15763).
self.adapter._handle_text_message.assert_not_called()
@pytest.mark.asyncio
async def test_empty_sender_dropped(self):
ev = self._mk_event(sender="")
await self.adapter._on_room_message(ev)
self.adapter._handle_text_message.assert_not_called()
@pytest.mark.asyncio
async def test_self_with_unresolved_user_id_dropped(self):
# whoami has not resolved yet → user_id empty → drop ALL traffic
# defensively rather than risk echoing our own outbound messages.
self.adapter._user_id = ""
ev = self._mk_event(sender="@alice:example.org")
await self.adapter._on_room_message(ev)
self.adapter._handle_text_message.assert_not_called()
@pytest.mark.asyncio
async def test_regular_user_reaches_text_handler(self):
ev = self._mk_event(sender="@alice:example.org", body="hello bot")
await self.adapter._on_room_message(ev)
self.adapter._handle_text_message.assert_awaited_once()