matrix/livekit/test_voice_limit_guard.py

#!/usr/bin/env python3
"""Unit tests for voice-limit-guard pure logic + JWT re-sign roundtrip.

Run: python3 -m unittest livekit/test_voice_limit_guard.py  (from repo root)
The module has a hyphenated filename, so it's loaded via importlib.
"""

import hashlib
import hmac
import importlib.util
import urllib.error
import json
import os
import unittest

_HERE = os.path.dirname(os.path.abspath(__file__))
_spec = importlib.util.spec_from_file_location(
    "voice_limit_guard", os.path.join(_HERE, "voice-limit-guard.py")
)
guard = importlib.util.module_from_spec(_spec)
_spec.loader.exec_module(guard)


def make_jwt(secret: str, payload: dict) -> str:
    header_b64 = guard.b64url(json.dumps({"alg": "HS256", "typ": "JWT"}).encode())
    payload_b64 = guard.b64url(json.dumps(payload).encode())
    signing_input = f"{header_b64}.{payload_b64}".encode()
    sig = guard.b64url(hmac.new(secret.encode(), signing_input, hashlib.sha256).digest())
    return f"{header_b64}.{payload_b64}.{sig}"


def verify_jwt(secret: str, token: str) -> bool:
    header_b64, payload_b64, sig = token.split(".")
    expected = guard.b64url(
        hmac.new(secret.encode(), f"{header_b64}.{payload_b64}".encode(), hashlib.sha256).digest()
    )
    return hmac.compare_digest(expected, sig)


class TestShouldBlock(unittest.TestCase):
    def test_no_limit_never_blocks(self):
        self.assertFalse(guard.should_block(0, {"@a:x", "@b:x"}, "@c:x"))

    def test_rejoin_never_blocks(self):
        self.assertFalse(guard.should_block(2, {"@a:x", "@b:x"}, "@a:x"))

    def test_blocks_at_capacity_for_new_user(self):
        self.assertTrue(guard.should_block(2, {"@a:x", "@b:x"}, "@c:x"))

    def test_allows_below_capacity(self):
        self.assertFalse(guard.should_block(3, {"@a:x", "@b:x"}, "@c:x"))


class TestMatrixUser(unittest.TestCase):
    def test_strips_device(self):
        self.assertEqual(guard.matrix_user("@bob:example.org:DEVICEID"), "@bob:example.org")

    def test_plain_user(self):
        self.assertEqual(guard.matrix_user("@bob:example.org"), "@bob:example.org")

    def test_non_matrix_identity_unchanged(self):
        self.assertEqual(guard.matrix_user("hashedfederatedid"), "hashedfederatedid")


class TestAllowedSources(unittest.TestCase):
    def test_all_allowed_returns_none(self):
        self.assertIsNone(guard.allowed_sources({}))
        self.assertIsNone(
            guard.allowed_sources({"allow_camera": True, "allow_screenshare": True})
        )

    def test_no_screenshare_drops_screen_sources_keeps_mic_cam(self):
        self.assertEqual(
            guard.allowed_sources({"allow_screenshare": False}),
            ["microphone", "camera"],
        )

    def test_audio_only_keeps_mic_only(self):
        self.assertEqual(
            guard.allowed_sources({"allow_screenshare": False, "allow_camera": False}),
            ["microphone"],
        )

    def test_no_camera_keeps_mic_and_screenshare(self):
        self.assertEqual(
            guard.allowed_sources({"allow_camera": False}),
            ["microphone", "screen_share", "screen_share_audio"],
        )


class TestResignJwt(unittest.TestCase):
    SECRET = "test-livekit-secret"

    def _make(self):
        return make_jwt(
            self.SECRET,
            {
                "iss": "APIkey",
                "sub": "@alice:example.org:DEV1",
                "nbf": 1000,
                "exp": 5000,
                "video": {"roomJoin": True, "room": "hashed-alias", "canPublish": True,
                          "canSubscribe": True},
            },
        )

    def test_resigned_token_verifies_with_same_secret(self):
        token = self._make()
        new = guard.resign_jwt(token, self.SECRET, ["microphone", "camera"])
        self.assertTrue(verify_jwt(self.SECRET, new))

    def test_sets_sources_and_preserves_identity_and_room(self):
        token = self._make()
        new = guard.resign_jwt(token, self.SECRET, ["microphone"])
        claims = guard.jwt_payload(new)
        self.assertEqual(claims["video"]["canPublishSources"], ["microphone"])
        # Everything else preserved.
        self.assertEqual(claims["sub"], "@alice:example.org:DEV1")
        self.assertEqual(claims["video"]["room"], "hashed-alias")
        self.assertEqual(claims["exp"], 5000)
        self.assertTrue(claims["video"]["canPublish"])

    def test_preserves_original_header_segment(self):
        token = self._make()
        new = guard.resign_jwt(token, self.SECRET, ["microphone"])
        self.assertEqual(token.split(".")[0], new.split(".")[0])

    def test_raises_without_video_grant(self):
        token = make_jwt(self.SECRET, {"sub": "@x:y", "exp": 1})
        with self.assertRaises(ValueError):
            guard.resign_jwt(token, self.SECRET, ["microphone"])

    def test_tampering_detectable(self):
        # A token re-signed with the WRONG secret must not verify with the real one.
        token = self._make()
        forged = guard.resign_jwt(token, "wrong-secret", ["microphone"])
        self.assertFalse(verify_jwt(self.SECRET, forged))


class TestVerifyJwtSig(unittest.TestCase):
    SECRET = "shared-livekit-secret"

    def _token(self, secret):
        return make_jwt(secret, {"sub": "@a:b:D", "exp": 9, "video": {"room": "r"}})

    def test_verifies_token_signed_with_same_secret(self):
        # Guard's own secret signed the token -> safe to re-sign.
        self.assertTrue(guard.verify_jwt_sig(self._token(self.SECRET), self.SECRET))

    def test_rejects_token_signed_with_different_secret(self):
        # Secret drift: lk-jwt-service used a different key. Re-signing would
        # produce a token the SFU rejects, so the guard must detect this and
        # skip the restriction (fail open) instead.
        self.assertFalse(guard.verify_jwt_sig(self._token("lk-jwt-secret"), self.SECRET))

    def test_malformed_token_returns_false(self):
        self.assertFalse(guard.verify_jwt_sig("not-a-jwt", self.SECRET))
        self.assertFalse(guard.verify_jwt_sig("", self.SECRET))


class TestRoomIdFromRequest(unittest.TestCase):
    def test_legacy_sfu_get_reads_room(self):
        self.assertEqual(guard.room_id_from_request("/sfu/get", {"room": "!a:x"}), "!a:x")

    def test_new_get_token_reads_room_id(self):
        self.assertEqual(guard.room_id_from_request("/get_token", {"room_id": "!b:x"}), "!b:x")

    def test_both_keys_uses_endpoint_field_not_the_other(self):
        # A client sending both keys must not get the wrong room's policy: each
        # endpoint reads only its own field (matching lk-jwt-service).
        both = {"room": "!lax:x", "room_id": "!restricted:x"}
        self.assertEqual(guard.room_id_from_request("/sfu/get", both), "!lax:x")
        self.assertEqual(guard.room_id_from_request("/get_token", both), "!restricted:x")

    def test_missing_field_is_empty(self):
        self.assertEqual(guard.room_id_from_request("/get_token", {"room": "!a:x"}), "")


class TestForbiddenSources(unittest.TestCase):
    def test_none_forbidden_when_all_allowed(self):
        self.assertEqual(guard.forbidden_sources({}), set())
        self.assertEqual(
            guard.forbidden_sources({"allow_camera": True, "allow_screenshare": True}), set()
        )

    def test_screenshare_forbidden(self):
        self.assertEqual(
            guard.forbidden_sources({"allow_screenshare": False}),
            {"SCREEN_SHARE", "SCREEN_SHARE_AUDIO"},
        )

    def test_audio_only_forbids_cam_and_screen(self):
        self.assertEqual(
            guard.forbidden_sources({"allow_screenshare": False, "allow_camera": False}),
            {"SCREEN_SHARE", "SCREEN_SHARE_AUDIO", "CAMERA"},
        )


class TestReconcilePublishSources(unittest.TestCase):
    SS = {"SCREEN_SHARE", "SCREEN_SHARE_AUDIO"}

    def test_empty_current_means_all_allowed_so_gets_narrowed(self):
        # [] = all allowed; forbidding screenshare must produce the explicit
        # non-screenshare list (never an empty list, which LK reads as "all").
        result = guard.reconcile_publish_sources([], self.SS)
        self.assertEqual(result, ["CAMERA", "MICROPHONE"])

    def test_compliant_when_no_forbidden_present(self):
        self.assertIsNone(guard.reconcile_publish_sources(["CAMERA", "MICROPHONE"], self.SS))

    def test_removes_only_forbidden_never_grants(self):
        result = guard.reconcile_publish_sources(["MICROPHONE", "SCREEN_SHARE"], self.SS)
        self.assertEqual(result, ["MICROPHONE"])

    def test_never_widens_a_narrow_set(self):
        # Participant only had mic; forbidding screenshare leaves mic — camera is
        # NOT granted.
        self.assertIsNone(guard.reconcile_publish_sources(["MICROPHONE"], self.SS))

    def test_empty_result_signals_disable_publish(self):
        # If the only source they had is now forbidden, the result is [] so the
        # caller sets canPublish=False (not an empty allow-list).
        result = guard.reconcile_publish_sources(["SCREEN_SHARE"], self.SS)
        self.assertEqual(result, [])


class TestReconcileParticipant(unittest.TestCase):
    def setUp(self):
        self.calls = []
        self._orig = guard.livekit_update_participant
        guard.livekit_update_participant = lambda a, i, p: self.calls.append((a, i, p))

    def tearDown(self):
        guard.livekit_update_participant = self._orig

    def test_skips_non_publisher(self):
        p = {"identity": "u", "permission": {"canPublish": False}}
        self.assertFalse(guard.reconcile_participant("room", p, {"SCREEN_SHARE"}))
        self.assertEqual(self.calls, [])

    def test_skips_compliant_publisher(self):
        p = {
            "identity": "u",
            "permission": {"canPublish": True, "canPublishSources": ["MICROPHONE", "CAMERA"]},
        }
        self.assertFalse(guard.reconcile_participant("room", p, {"SCREEN_SHARE"}))
        self.assertEqual(self.calls, [])

    def test_revokes_and_preserves_other_permission_flags(self):
        p = {
            "identity": "@a:b:D",
            "permission": {
                "canPublish": True,
                "canSubscribe": True,
                "canPublishData": True,
                "canPublishSources": ["MICROPHONE", "SCREEN_SHARE"],
            },
        }
        self.assertTrue(guard.reconcile_participant("room", p, {"SCREEN_SHARE", "SCREEN_SHARE_AUDIO"}))
        self.assertEqual(len(self.calls), 1)
        _alias, identity, perm = self.calls[0]
        self.assertEqual(identity, "@a:b:D")
        self.assertEqual(perm["canPublishSources"], ["MICROPHONE"])
        self.assertTrue(perm["canPublish"])
        # Other flags preserved (full-replace safety).
        self.assertTrue(perm["canSubscribe"])
        self.assertTrue(perm["canPublishData"])

    def test_disables_publish_when_no_source_remains(self):
        p = {"identity": "u", "permission": {"canPublish": True, "canPublishSources": ["SCREEN_SHARE"]}}
        guard.reconcile_participant("room", p, {"SCREEN_SHARE", "SCREEN_SHARE_AUDIO"})
        _a, _i, perm = self.calls[0]
        self.assertFalse(perm["canPublish"])


class TestReconcileRoom(unittest.TestCase):
    """End-to-end reconcile_room with LiveKit + Synapse mocked."""

    def setUp(self):
        self._orig_state = guard.room_state
        self._orig_list = guard.livekit_list_participants
        self._orig_update = guard.livekit_update_participant
        self.updates = []
        guard.livekit_update_participant = lambda a, i, p: self.updates.append((i, p))
        guard._alias_to_room.clear()

    def tearDown(self):
        guard.room_state = self._orig_state
        guard.livekit_list_participants = self._orig_list
        guard.livekit_update_participant = self._orig_update
        guard._alias_to_room.clear()

    def test_unrestricted_room_touches_nothing(self):
        guard.room_state = lambda rid, max_age=0: {"allow_screenshare": True, "allow_camera": True}
        guard.livekit_list_participants = lambda a: (_ for _ in ()).throw(
            AssertionError("should not list participants when unrestricted")
        )
        guard.reconcile_room("alias", "!room:x")
        self.assertEqual(self.updates, [])

    def test_screenshare_forbidden_revokes_the_sharer(self):
        guard.room_state = lambda rid, max_age=0: {"allow_screenshare": False, "allow_camera": True}
        guard.livekit_list_participants = lambda a: [
            {"identity": "sharer", "permission": {"canPublish": True,
             "canPublishSources": ["MICROPHONE", "SCREEN_SHARE"]}},
            {"identity": "listener", "permission": {"canPublish": True,
             "canPublishSources": ["MICROPHONE"]}},
        ]
        guard.reconcile_room("alias", "!room:x")
        self.assertEqual(len(self.updates), 1)
        self.assertEqual(self.updates[0][0], "sharer")
        self.assertEqual(self.updates[0][1]["canPublishSources"], ["MICROPHONE"])

    def test_empty_room_is_NOT_forgotten(self):
        # An empty read may be transient (room persists until empty_timeout); only
        # a 404 prunes, so mid-call enforcement isn't dropped on a race.
        guard._alias_to_room["alias"] = "!room:x"
        guard.room_state = lambda rid, max_age=0: {"allow_screenshare": False, "allow_camera": True}
        guard.livekit_list_participants = lambda a: []
        guard.reconcile_room("alias", "!room:x")
        self.assertIn("alias", guard._alias_to_room)

    def test_room_gone_404_is_forgotten(self):
        guard._alias_to_room["alias"] = "!room:x"
        guard.room_state = lambda rid, max_age=0: {"allow_screenshare": False, "allow_camera": True}

        def _raise_404(_alias):
            raise urllib.error.HTTPError("u", 404, "not found", {}, None)

        guard.livekit_list_participants = _raise_404
        guard.reconcile_room("alias", "!room:x")
        self.assertNotIn("alias", guard._alias_to_room)


class TestRoomStateParsing(unittest.TestCase):
    """allow_* only forbids on an explicit False; absent/other stays permissive."""

    def _policy(self, content):
        # Emulate the parsing block in room_state without hitting Synapse.
        return {
            "allow_screenshare": content.get("allow_screenshare", True) is not False,
            "allow_camera": content.get("allow_camera", True) is not False,
        }

    def test_absent_is_allowed(self):
        self.assertEqual(
            self._policy({}), {"allow_screenshare": True, "allow_camera": True}
        )

    def test_explicit_false_forbids(self):
        self.assertEqual(
            self._policy({"allow_screenshare": False}),
            {"allow_screenshare": False, "allow_camera": True},
        )

    def test_non_bool_stays_permissive(self):
        self.assertEqual(
            self._policy({"allow_screenshare": "no"}),
            {"allow_screenshare": True, "allow_camera": True},
        )


if __name__ == "__main__":
    unittest.main()