diff options
Diffstat (limited to 'synapse/event_auth.py')
| -rw-r--r-- | synapse/event_auth.py | 678 |
1 files changed, 678 insertions, 0 deletions
diff --git a/synapse/event_auth.py b/synapse/event_auth.py new file mode 100644 index 0000000000..4096c606f1 --- /dev/null +++ b/synapse/event_auth.py @@ -0,0 +1,678 @@ +# -*- coding: utf-8 -*- +# Copyright 2014 - 2016 OpenMarket Ltd +# +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +import logging + +from canonicaljson import encode_canonical_json +from signedjson.key import decode_verify_key_bytes +from signedjson.sign import verify_signed_json, SignatureVerifyException +from unpaddedbase64 import decode_base64 + +from synapse.api.constants import EventTypes, Membership, JoinRules +from synapse.api.errors import AuthError, SynapseError, EventSizeError +from synapse.types import UserID, get_domain_from_id + +logger = logging.getLogger(__name__) + + +def check(event, auth_events, do_sig_check=True, do_size_check=True): + """ Checks if this event is correctly authed. + + Args: + event: the event being checked. + auth_events (dict: event-key -> event): the existing room state. + + + Returns: + True if the auth checks pass. + """ + if do_size_check: + _check_size_limits(event) + + if not hasattr(event, "room_id"): + raise AuthError(500, "Event has no room_id: %s" % event) + + if do_sig_check: + sender_domain = get_domain_from_id(event.sender) + event_id_domain = get_domain_from_id(event.event_id) + + is_invite_via_3pid = ( + event.type == EventTypes.Member + and event.membership == Membership.INVITE + and "third_party_invite" in event.content + ) + + # Check the sender's domain has signed the event + if not event.signatures.get(sender_domain): + # We allow invites via 3pid to have a sender from a different + # HS, as the sender must match the sender of the original + # 3pid invite. This is checked further down with the + # other dedicated membership checks. + if not is_invite_via_3pid: + raise AuthError(403, "Event not signed by sender's server") + + # Check the event_id's domain has signed the event + if not event.signatures.get(event_id_domain): + raise AuthError(403, "Event not signed by sending server") + + if auth_events is None: + # Oh, we don't know what the state of the room was, so we + # are trusting that this is allowed (at least for now) + logger.warn("Trusting event: %s", event.event_id) + return True + + if event.type == EventTypes.Create: + room_id_domain = get_domain_from_id(event.room_id) + if room_id_domain != sender_domain: + raise AuthError( + 403, + "Creation event's room_id domain does not match sender's" + ) + # FIXME + return True + + creation_event = auth_events.get((EventTypes.Create, ""), None) + + if not creation_event: + raise SynapseError( + 403, + "Room %r does not exist" % (event.room_id,) + ) + + creating_domain = get_domain_from_id(event.room_id) + originating_domain = get_domain_from_id(event.sender) + if creating_domain != originating_domain: + if not _can_federate(event, auth_events): + raise AuthError( + 403, + "This room has been marked as unfederatable." + ) + + # FIXME: Temp hack + if event.type == EventTypes.Aliases: + if not event.is_state(): + raise AuthError( + 403, + "Alias event must be a state event", + ) + if not event.state_key: + raise AuthError( + 403, + "Alias event must have non-empty state_key" + ) + sender_domain = get_domain_from_id(event.sender) + if event.state_key != sender_domain: + raise AuthError( + 403, + "Alias event's state_key does not match sender's domain" + ) + return True + + if logger.isEnabledFor(logging.DEBUG): + logger.debug( + "Auth events: %s", + [a.event_id for a in auth_events.values()] + ) + + if event.type == EventTypes.Member: + allowed = _is_membership_change_allowed( + event, auth_events + ) + if allowed: + logger.debug("Allowing! %s", event) + else: + logger.debug("Denying! %s", event) + return allowed + + _check_event_sender_in_room(event, auth_events) + + # Special case to allow m.room.third_party_invite events wherever + # a user is allowed to issue invites. Fixes + # https://github.com/vector-im/vector-web/issues/1208 hopefully + if event.type == EventTypes.ThirdPartyInvite: + user_level = get_user_power_level(event.user_id, auth_events) + invite_level = _get_named_level(auth_events, "invite", 0) + + if user_level < invite_level: + raise AuthError( + 403, ( + "You cannot issue a third party invite for %s." % + (event.content.display_name,) + ) + ) + else: + return True + + _can_send_event(event, auth_events) + + if event.type == EventTypes.PowerLevels: + _check_power_levels(event, auth_events) + + if event.type == EventTypes.Redaction: + check_redaction(event, auth_events) + + logger.debug("Allowing! %s", event) + + +def _check_size_limits(event): + def too_big(field): + raise EventSizeError("%s too large" % (field,)) + + if len(event.user_id) > 255: + too_big("user_id") + if len(event.room_id) > 255: + too_big("room_id") + if event.is_state() and len(event.state_key) > 255: + too_big("state_key") + if len(event.type) > 255: + too_big("type") + if len(event.event_id) > 255: + too_big("event_id") + if len(encode_canonical_json(event.get_pdu_json())) > 65536: + too_big("event") + + +def _can_federate(event, auth_events): + creation_event = auth_events.get((EventTypes.Create, "")) + + return creation_event.content.get("m.federate", True) is True + + +def _is_membership_change_allowed(event, auth_events): + membership = event.content["membership"] + + # Check if this is the room creator joining: + if len(event.prev_events) == 1 and Membership.JOIN == membership: + # Get room creation event: + key = (EventTypes.Create, "", ) + create = auth_events.get(key) + if create and event.prev_events[0][0] == create.event_id: + if create.content["creator"] == event.state_key: + return True + + target_user_id = event.state_key + + creating_domain = get_domain_from_id(event.room_id) + target_domain = get_domain_from_id(target_user_id) + if creating_domain != target_domain: + if not _can_federate(event, auth_events): + raise AuthError( + 403, + "This room has been marked as unfederatable." + ) + + # get info about the caller + key = (EventTypes.Member, event.user_id, ) + caller = auth_events.get(key) + + caller_in_room = caller and caller.membership == Membership.JOIN + caller_invited = caller and caller.membership == Membership.INVITE + + # get info about the target + key = (EventTypes.Member, target_user_id, ) + target = auth_events.get(key) + + target_in_room = target and target.membership == Membership.JOIN + target_banned = target and target.membership == Membership.BAN + + key = (EventTypes.JoinRules, "", ) + join_rule_event = auth_events.get(key) + if join_rule_event: + join_rule = join_rule_event.content.get( + "join_rule", JoinRules.INVITE + ) + else: + join_rule = JoinRules.INVITE + + user_level = get_user_power_level(event.user_id, auth_events) + target_level = get_user_power_level( + target_user_id, auth_events + ) + + # FIXME (erikj): What should we do here as the default? + ban_level = _get_named_level(auth_events, "ban", 50) + + logger.debug( + "_is_membership_change_allowed: %s", + { + "caller_in_room": caller_in_room, + "caller_invited": caller_invited, + "target_banned": target_banned, + "target_in_room": target_in_room, + "membership": membership, + "join_rule": join_rule, + "target_user_id": target_user_id, + "event.user_id": event.user_id, + } + ) + + if Membership.INVITE == membership and "third_party_invite" in event.content: + if not _verify_third_party_invite(event, auth_events): + raise AuthError(403, "You are not invited to this room.") + if target_banned: + raise AuthError( + 403, "%s is banned from the room" % (target_user_id,) + ) + return True + + if Membership.JOIN != membership: + if (caller_invited + and Membership.LEAVE == membership + and target_user_id == event.user_id): + return True + + if not caller_in_room: # caller isn't joined + raise AuthError( + 403, + "%s not in room %s." % (event.user_id, event.room_id,) + ) + + if Membership.INVITE == membership: + # TODO (erikj): We should probably handle this more intelligently + # PRIVATE join rules. + + # Invites are valid iff caller is in the room and target isn't. + if target_banned: + raise AuthError( + 403, "%s is banned from the room" % (target_user_id,) + ) + elif target_in_room: # the target is already in the room. + raise AuthError(403, "%s is already in the room." % + target_user_id) + else: + invite_level = _get_named_level(auth_events, "invite", 0) + + if user_level < invite_level: + raise AuthError( + 403, "You cannot invite user %s." % target_user_id + ) + elif Membership.JOIN == membership: + # Joins are valid iff caller == target and they were: + # invited: They are accepting the invitation + # joined: It's a NOOP + if event.user_id != target_user_id: + raise AuthError(403, "Cannot force another user to join.") + elif target_banned: + raise AuthError(403, "You are banned from this room") + elif join_rule == JoinRules.PUBLIC: + pass + elif join_rule == JoinRules.INVITE: + if not caller_in_room and not caller_invited: + raise AuthError(403, "You are not invited to this room.") + else: + # TODO (erikj): may_join list + # TODO (erikj): private rooms + raise AuthError(403, "You are not allowed to join this room") + elif Membership.LEAVE == membership: + # TODO (erikj): Implement kicks. + if target_banned and user_level < ban_level: + raise AuthError( + 403, "You cannot unban user &s." % (target_user_id,) + ) + elif target_user_id != event.user_id: + kick_level = _get_named_level(auth_events, "kick", 50) + + if user_level < kick_level or user_level <= target_level: + raise AuthError( + 403, "You cannot kick user %s." % target_user_id + ) + elif Membership.BAN == membership: + if user_level < ban_level or user_level <= target_level: + raise AuthError(403, "You don't have permission to ban") + else: + raise AuthError(500, "Unknown membership %s" % membership) + + return True + + +def _check_event_sender_in_room(event, auth_events): + key = (EventTypes.Member, event.user_id, ) + member_event = auth_events.get(key) + + return _check_joined_room( + member_event, + event.user_id, + event.room_id + ) + + +def _check_joined_room(member, user_id, room_id): + if not member or member.membership != Membership.JOIN: + raise AuthError(403, "User %s not in room %s (%s)" % ( + user_id, room_id, repr(member) + )) + + +def get_send_level(etype, state_key, auth_events): + key = (EventTypes.PowerLevels, "", ) + send_level_event = auth_events.get(key) + send_level = None + if send_level_event: + send_level = send_level_event.content.get("events", {}).get( + etype + ) + if send_level is None: + if state_key is not None: + send_level = send_level_event.content.get( + "state_default", 50 + ) + else: + send_level = send_level_event.content.get( + "events_default", 0 + ) + + if send_level: + send_level = int(send_level) + else: + send_level = 0 + + return send_level + + +def _can_send_event(event, auth_events): + send_level = get_send_level( + event.type, event.get("state_key", None), auth_events + ) + user_level = get_user_power_level(event.user_id, auth_events) + + if user_level < send_level: + raise AuthError( + 403, + "You don't have permission to post that to the room. " + + "user_level (%d) < send_level (%d)" % (user_level, send_level) + ) + + # Check state_key + if hasattr(event, "state_key"): + if event.state_key.startswith("@"): + if event.state_key != event.user_id: + raise AuthError( + 403, + "You are not allowed to set others state" + ) + + return True + + +def check_redaction(event, auth_events): + """Check whether the event sender is allowed to redact the target event. + + Returns: + True if the the sender is allowed to redact the target event if the + target event was created by them. + False if the sender is allowed to redact the target event with no + further checks. + + Raises: + AuthError if the event sender is definitely not allowed to redact + the target event. + """ + user_level = get_user_power_level(event.user_id, auth_events) + + redact_level = _get_named_level(auth_events, "redact", 50) + + if user_level >= redact_level: + return False + + redacter_domain = get_domain_from_id(event.event_id) + redactee_domain = get_domain_from_id(event.redacts) + if redacter_domain == redactee_domain: + return True + + raise AuthError( + 403, + "You don't have permission to redact events" + ) + + +def _check_power_levels(event, auth_events): + user_list = event.content.get("users", {}) + # Validate users + for k, v in user_list.items(): + try: + UserID.from_string(k) + except: + raise SynapseError(400, "Not a valid user_id: %s" % (k,)) + + try: + int(v) + except: + raise SynapseError(400, "Not a valid power level: %s" % (v,)) + + key = (event.type, event.state_key, ) + current_state = auth_events.get(key) + + if not current_state: + return + + user_level = get_user_power_level(event.user_id, auth_events) + + # Check other levels: + levels_to_check = [ + ("users_default", None), + ("events_default", None), + ("state_default", None), + ("ban", None), + ("redact", None), + ("kick", None), + ("invite", None), + ] + + old_list = current_state.content.get("users") + for user in set(old_list.keys() + user_list.keys()): + levels_to_check.append( + (user, "users") + ) + + old_list = current_state.content.get("events") + new_list = event.content.get("events") + for ev_id in set(old_list.keys() + new_list.keys()): + levels_to_check.append( + (ev_id, "events") + ) + + old_state = current_state.content + new_state = event.content + + for level_to_check, dir in levels_to_check: + old_loc = old_state + new_loc = new_state + if dir: + old_loc = old_loc.get(dir, {}) + new_loc = new_loc.get(dir, {}) + + if level_to_check in old_loc: + old_level = int(old_loc[level_to_check]) + else: + old_level = None + + if level_to_check in new_loc: + new_level = int(new_loc[level_to_check]) + else: + new_level = None + + if new_level is not None and old_level is not None: + if new_level == old_level: + continue + + if dir == "users" and level_to_check != event.user_id: + if old_level == user_level: + raise AuthError( + 403, + "You don't have permission to remove ops level equal " + "to your own" + ) + + if old_level > user_level or new_level > user_level: + raise AuthError( + 403, + "You don't have permission to add ops level greater " + "than your own" + ) + + +def _get_power_level_event(auth_events): + key = (EventTypes.PowerLevels, "", ) + return auth_events.get(key) + + +def get_user_power_level(user_id, auth_events): + power_level_event = _get_power_level_event(auth_events) + + if power_level_event: + level = power_level_event.content.get("users", {}).get(user_id) + if not level: + level = power_level_event.content.get("users_default", 0) + + if level is None: + return 0 + else: + return int(level) + else: + key = (EventTypes.Create, "", ) + create_event = auth_events.get(key) + if (create_event is not None and + create_event.content["creator"] == user_id): + return 100 + else: + return 0 + + +def _get_named_level(auth_events, name, default): + power_level_event = _get_power_level_event(auth_events) + + if not power_level_event: + return default + + level = power_level_event.content.get(name, None) + if level is not None: + return int(level) + else: + return default + + +def _verify_third_party_invite(event, auth_events): + """ + Validates that the invite event is authorized by a previous third-party invite. + + Checks that the public key, and keyserver, match those in the third party invite, + and that the invite event has a signature issued using that public key. + + Args: + event: The m.room.member join event being validated. + auth_events: All relevant previous context events which may be used + for authorization decisions. + + Return: + True if the event fulfills the expectations of a previous third party + invite event. + """ + if "third_party_invite" not in event.content: + return False + if "signed" not in event.content["third_party_invite"]: + return False + signed = event.content["third_party_invite"]["signed"] + for key in {"mxid", "token"}: + if key not in signed: + return False + + token = signed["token"] + + invite_event = auth_events.get( + (EventTypes.ThirdPartyInvite, token,) + ) + if not invite_event: + return False + + if invite_event.sender != event.sender: + return False + + if event.user_id != invite_event.user_id: + return False + + if signed["mxid"] != event.state_key: + return False + if signed["token"] != token: + return False + + for public_key_object in get_public_keys(invite_event): + public_key = public_key_object["public_key"] + try: + for server, signature_block in signed["signatures"].items(): + for key_name, encoded_signature in signature_block.items(): + if not key_name.startswith("ed25519:"): + continue + verify_key = decode_verify_key_bytes( + key_name, + decode_base64(public_key) + ) + verify_signed_json(signed, server, verify_key) + + # We got the public key from the invite, so we know that the + # correct server signed the signed bundle. + # The caller is responsible for checking that the signing + # server has not revoked that public key. + return True + except (KeyError, SignatureVerifyException,): + continue + return False + + +def get_public_keys(invite_event): + public_keys = [] + if "public_key" in invite_event.content: + o = { + "public_key": invite_event.content["public_key"], + } + if "key_validity_url" in invite_event.content: + o["key_validity_url"] = invite_event.content["key_validity_url"] + public_keys.append(o) + public_keys.extend(invite_event.content.get("public_keys", [])) + return public_keys + + +def auth_types_for_event(event): + """Given an event, return a list of (EventType, StateKey) that may be + needed to auth the event. The returned list may be a superset of what + would actually be required depending on the full state of the room. + + Used to limit the number of events to fetch from the database to + actually auth the event. + """ + if event.type == EventTypes.Create: + return [] + + auth_types = [] + + auth_types.append((EventTypes.PowerLevels, "", )) + auth_types.append((EventTypes.Member, event.user_id, )) + auth_types.append((EventTypes.Create, "", )) + + if event.type == EventTypes.Member: + membership = event.content["membership"] + if membership in [Membership.JOIN, Membership.INVITE]: + auth_types.append((EventTypes.JoinRules, "", )) + + auth_types.append((EventTypes.Member, event.state_key, )) + + if membership == Membership.INVITE: + if "third_party_invite" in event.content: + key = ( + EventTypes.ThirdPartyInvite, + event.content["third_party_invite"]["signed"]["token"] + ) + auth_types.append(key) + + return auth_types |