fix(auth): prevent allowlist bypass via sender_id token splitting

tests/test_base_channel.py

@@ -0,0 +1,25 @@
+from types import SimpleNamespace
+
+from nanobot.bus.events import OutboundMessage
+from nanobot.bus.queue import MessageBus
+from nanobot.channels.base import BaseChannel
+
+
+class _DummyChannel(BaseChannel):
+    name = "dummy"
+
+    async def start(self) -> None:
+        return None
+
+    async def stop(self) -> None:
+        return None
+
+    async def send(self, msg: OutboundMessage) -> None:
+        return None
+
+
+def test_is_allowed_requires_exact_match() -> None:
+    channel = _DummyChannel(SimpleNamespace(allow_from=["allow@email.com"]), MessageBus())
+
+    assert channel.is_allowed("allow@email.com") is True
+    assert channel.is_allowed("attacker|allow@email.com") is False

tests/test_telegram_channel.py

@@ -131,6 +131,21 @@ def test_get_extension_falls_back_to_original_filename() -> None:
     assert channel._get_extension("file", None, "archive.tar.gz") == ".tar.gz"
 
 
+def test_is_allowed_accepts_legacy_telegram_id_username_formats() -> None:
+    channel = TelegramChannel(TelegramConfig(allow_from=["12345", "alice", "67890|bob"]), MessageBus())
+
+    assert channel.is_allowed("12345|carol") is True
+    assert channel.is_allowed("99999|alice") is True
+    assert channel.is_allowed("67890|bob") is True
+
+
+def test_is_allowed_rejects_invalid_legacy_telegram_sender_shapes() -> None:
+    channel = TelegramChannel(TelegramConfig(allow_from=["alice"]), MessageBus())
+
+    assert channel.is_allowed("attacker|alice|extra") is False
+    assert channel.is_allowed("not-a-number|alice") is False
+
+
 @pytest.mark.asyncio
 async def test_send_progress_keeps_message_in_topic() -> None:
     config = TelegramConfig(enabled=True, token="123:abc", allow_from=["*"])