def check_username(self, localpart, guest_access_token=None):
        yield run_on_reactor()

        if urllib.quote(localpart.encode('utf-8')) != localpart:
            raise SynapseError(
                400,
                "User ID can only contain characters a-z, 0-9, or '_-./'",
                Codes.INVALID_USERNAME
            )

        user = UserID(localpart, self.hs.hostname)
        user_id = user.to_string()

        yield self.check_user_id_is_valid(user_id)

        users = yield self.store.get_users_by_id_case_insensitive(user_id)
        if users:
            if not guest_access_token:
                raise SynapseError(
                    400,
                    "User ID already taken.",
                    errcode=Codes.USER_IN_USE,
                )
            user_data = yield self.auth.get_user_from_macaroon(guest_access_token)
            if not user_data["is_guest"] or user_data["user"].localpart != localpart:
                raise AuthError(
                    403,
                    "Cannot register taken user ID without valid guest "
                    "credentials for that user.",
                    errcode=Codes.FORBIDDEN,
                )

    def _do_create(self, requester, user_json):
        yield run_on_reactor()

        if "localpart" not in user_json:
            raise SynapseError(400, "Expected 'localpart' key.")

        if "displayname" not in user_json:
            raise SynapseError(400, "Expected 'displayname' key.")

        localpart = user_json["localpart"].encode("utf-8")
        displayname = user_json["displayname"].encode("utf-8")
        password_hash = user_json["password_hash"].encode("utf-8") \
            if user_json.get("password_hash") else None

        handler = self.handlers.registration_handler
        user_id, token = yield handler.get_or_create_user(
            requester=requester,
            localpart=localpart,
            displayname=displayname,
            password_hash=password_hash
        )

        defer.returnValue({
            "user_id": user_id,
            "access_token": token,
            "home_server": self.hs.hostname,
        })

    def requestMsisdnToken(
            self, id_server, country, phone_number,
            client_secret, send_attempt, **kwargs
    ):
        yield run_on_reactor()

        if not self._should_trust_id_server(id_server):
            raise SynapseError(
                400, "Untrusted ID server '%s'" % id_server,
                Codes.SERVER_NOT_TRUSTED
            )

        params = {
            'country': country,
            'phone_number': phone_number,
            'client_secret': client_secret,
            'send_attempt': send_attempt,
        }
        params.update(kwargs)

        try:
            data = yield self.http_client.post_json_get_json(
                "https://%s%s" % (
                    id_server,
                    "/_matrix/identity/api/v1/validate/msisdn/requestToken"
                ),
                params
            )
            defer.returnValue(data)
        except MatrixCodeMessageException as e:
            logger.info("Proxied requestToken failed with Matrix error: %r", e)
            raise SynapseError(e.code, e.msg, e.errcode)
        except CodeMessageException as e:
            logger.info("Proxied requestToken failed: %r", e)
            raise e

    def on_new_receipts(self, min_stream_id, max_stream_id, affected_room_ids):
        yield run_on_reactor()
        try:
            # Need to subtract 1 from the minimum because the lower bound here
            # is not inclusive
            updated_receipts = yield self.store.get_all_updated_receipts(
                min_stream_id - 1, max_stream_id
            )
            # This returns a tuple, user_id is at index 3
            users_affected = set([r[3] for r in updated_receipts])

            deferreds = []

            for u in users_affected:
                if u in self.pushers:
                    for p in self.pushers[u].values():
                        deferreds.append(
                            run_in_background(
                                p.on_new_receipts,
                                min_stream_id, max_stream_id,
                            )
                        )

            yield make_deferred_yieldable(
                defer.gatherResults(deferreds, consumeErrors=True),
            )
        except Exception:
            logger.exception("Exception in pusher on_new_receipts")

    def bind_threepid(self, creds, mxid):
        yield run_on_reactor()
        logger.debug("binding threepid %r to %s", creds, mxid)
        data = None

        if 'id_server' in creds:
            id_server = creds['id_server']
        elif 'idServer' in creds:
            id_server = creds['idServer']
        else:
            raise SynapseError(400, "No id_server in creds")

        if 'client_secret' in creds:
            client_secret = creds['client_secret']
        elif 'clientSecret' in creds:
            client_secret = creds['clientSecret']
        else:
            raise SynapseError(400, "No client_secret in creds")

        try:
            data = yield self.http_client.post_urlencoded_get_json(
                "https://%s%s" % (
                    id_server, "/_matrix/identity/api/v1/3pid/bind"
                ),
                {
                    'sid': creds['sid'],
                    'client_secret': client_secret,
                    'mxid': mxid,
                }
            )
            logger.debug("bound threepid %r to %s", creds, mxid)
        except CodeMessageException as e:
            data = json.loads(e.msg)
        defer.returnValue(data)

    def on_POST(self, request):
        yield run_on_reactor()

        body = parse_json_object_from_request(request)

        threePidCreds = body.get("threePidCreds")
        threePidCreds = body.get("three_pid_creds", threePidCreds)
        if threePidCreds is None:
            raise SynapseError(400, "Missing param", Codes.MISSING_PARAM)

        requester = yield self.auth.get_user_by_req(request)
        user_id = requester.user.to_string()

        threepid = yield self.identity_handler.threepid_from_creds(threePidCreds)

        if not threepid:
            raise SynapseError(400, "Failed to auth 3pid", Codes.THREEPID_AUTH_FAILED)

        for reqd in ["medium", "address", "validated_at"]:
            if reqd not in threepid:
                logger.warn("Couldn't add 3pid: invalid response from ID sevrer")
                raise SynapseError(500, "Invalid response from ID Server")

        yield self.auth_handler.add_threepid(user_id, threepid["medium"], threepid["address"], threepid["validated_at"])

        if "bind" in body and body["bind"]:
            logger.debug("Binding emails %s to %s", threepid, user_id)
            yield self.identity_handler.bind_threepid(threePidCreds, user_id)

        defer.returnValue((200, {}))

    def requestEmailToken(self, id_server, email, client_secret, send_attempt, **kwargs):
        yield run_on_reactor()

        if not self._should_trust_id_server(id_server):
            raise SynapseError(
                400, "Untrusted ID server '%s'" % id_server,
                Codes.SERVER_NOT_TRUSTED
            )

        params = {
            'email': email,
            'client_secret': client_secret,
            'send_attempt': send_attempt,
        }
        params.update(kwargs)

        try:
            data = yield self.http_client.post_urlencoded_get_json(
                "https://%s%s" % (
                    id_server,
                    "/_matrix/identity/api/v1/validate/email/requestToken"
                ),
                params
            )
            defer.returnValue(data)
        except CodeMessageException as e:
            logger.info("Proxied requestToken failed: %r", e)
            raise e

    def _on_new_room_event(self, event, snapshot, extra_destinations=[],
                           extra_users=[], suppress_auth=False,
                           do_invite_host=None):
        yield run_on_reactor()

        snapshot.fill_out_prev_events(event)

        yield self.state_handler.annotate_event_with_state(event)

        yield self.auth.add_auth_events(event)

        logger.debug("Signing event...")

        add_hashes_and_signatures(
            event, self.server_name, self.signing_key
        )

        logger.debug("Signed event.")

        if not suppress_auth:
            logger.debug("Authing...")
            self.auth.check(event, auth_events=event.old_state_events)
            logger.debug("Authed")
        else:
            logger.debug("Suppressed auth.")

        if do_invite_host:
            federation_handler = self.hs.get_handlers().federation_handler
            invite_event = yield federation_handler.send_invite(
                do_invite_host,
                event
            )

            # FIXME: We need to check if the remote changed anything else
            event.signatures = invite_event.signatures

        yield self.store.persist_event(event)

        destinations = set(extra_destinations)
        # Send a PDU to all hosts who have joined the room.

        for k, s in event.state_events.items():
            try:
                if k[0] == RoomMemberEvent.TYPE:
                    if s.content["membership"] == Membership.JOIN:
                        destinations.add(
                            self.hs.parse_userid(s.state_key).domain
                        )
            except:
                logger.warn(
                    "Failed to get destination from event %s", s.event_id
                )

        event.destinations = list(destinations)

        yield self.notifier.on_new_room_event(event, extra_users=extra_users)

        federation_handler = self.hs.get_handlers().federation_handler
        yield federation_handler.handle_new_event(event, snapshot)

    def add_auth_events(self, builder, context):
        yield run_on_reactor()

        if builder.type == EventTypes.Create:
            builder.auth_events = []
            return

        auth_ids = []

        key = (EventTypes.PowerLevels, "", )
        power_level_event = context.current_state.get(key)

        if power_level_event:
            auth_ids.append(power_level_event.event_id)

        key = (EventTypes.JoinRules, "", )
        join_rule_event = context.current_state.get(key)

        key = (EventTypes.Member, builder.user_id, )
        member_event = context.current_state.get(key)

        key = (EventTypes.Create, "", )
        create_event = context.current_state.get(key)
        if create_event:
            auth_ids.append(create_event.event_id)

        if join_rule_event:
            join_rule = join_rule_event.content.get("join_rule")
            is_public = join_rule == JoinRules.PUBLIC if join_rule else False
        else:
            is_public = False

        if builder.type == EventTypes.Member:
            e_type = builder.content["membership"]
            if e_type in [Membership.JOIN, Membership.INVITE]:
                if join_rule_event:
                    auth_ids.append(join_rule_event.event_id)

            if e_type == Membership.JOIN:
                if member_event and not is_public:
                    auth_ids.append(member_event.event_id)
            else:
                if member_event:
                    auth_ids.append(member_event.event_id)
        elif member_event:
            if member_event.content["membership"] == Membership.JOIN:
                auth_ids.append(member_event.event_id)

        auth_events_entries = yield self.store.add_event_hashes(
            auth_ids
        )

        builder.auth_events = auth_events_entries

        context.auth_events = {
            k: v
            for k, v in context.current_state.items()
            if v.event_id in auth_ids
        }

    def on_GET(self, request):
        yield run_on_reactor()

        requester = yield self.auth.get_user_by_req(request)

        threepids = yield self.hs.get_datastore().user_get_threepids(requester.user.to_string())

        defer.returnValue((200, {"threepids": threepids}))

    def register(self, localpart=None, password=None):
        """Registers a new client on the server.

        Args:
            localpart : The local part of the user ID to register. If None,
              one will be randomly generated.
            password (str) : The password to assign to this user so they can
            login again.
        Returns:
            A tuple of (user_id, access_token).
        Raises:
            RegistrationError if there was a problem registering.
        """
        yield run_on_reactor()
        password_hash = None
        if password:
            password_hash = bcrypt.hashpw(password, bcrypt.gensalt())

        if localpart:
            user = UserID(localpart, self.hs.hostname)
            user_id = user.to_string()

            token = self._generate_token(user_id)
            yield self.store.register(
                user_id=user_id,
                token=token,
                password_hash=password_hash
            )

            yield self.distributor.fire("registered_user", user)
        else:
            # autogen a random user ID
            attempts = 0
            user_id = None
            token = None
            while not user_id and not token:
                try:
                    localpart = self._generate_user_id()
                    user = UserID(localpart, self.hs.hostname)
                    user_id = user.to_string()

                    token = self._generate_token(user_id)
                    yield self.store.register(
                        user_id=user_id,
                        token=token,
                        password_hash=password_hash)

                    self.distributor.fire("registered_user", user)
                except SynapseError:
                    # if user id is taken, just generate another
                    user_id = None
                    token = None
                    attempts += 1
                    if attempts > 5:
                        raise RegistrationError(
                            500, "Cannot generate user ID.")

        defer.returnValue((user_id, token))

 def _notify():
     yield run_on_reactor()
     try:
         self.notifier.on_new_room_event(
             event, event_stream_id, max_stream_id,
             extra_users=extra_users
         )
     except Exception:
         logger.exception("Error notifying about new room event")

    def handle_new_client_event(self, event, context, extra_destinations=[],
                                extra_users=[], suppress_auth=False):
        yield run_on_reactor()

        # We now need to go and hit out to wherever we need to hit out to.

        if not suppress_auth:
            self.auth.check(event, auth_events=context.current_state)

        yield self.store.persist_event(event, context=context)

        federation_handler = self.hs.get_handlers().federation_handler

        if event.type == EventTypes.Member:
            if event.content["membership"] == Membership.INVITE:
                invitee = UserID.from_string(event.state_key)
                if not self.hs.is_mine(invitee):
                    # TODO: Can we add signature from remote server in a nicer
                    # way? If we have been invited by a remote server, we need
                    # to get them to sign the event.
                    returned_invite = yield federation_handler.send_invite(
                        invitee.domain,
                        event,
                    )

                    # TODO: Make sure the signatures actually are correct.
                    event.signatures.update(
                        returned_invite.signatures
                    )

        destinations = set(extra_destinations)
        for k, s in context.current_state.items():
            try:
                if k[0] == EventTypes.Member:
                    if s.content["membership"] == Membership.JOIN:
                        destinations.add(
                            UserID.from_string(s.state_key).domain
                        )
            except SynapseError:
                logger.warn(
                    "Failed to get destination from event %s", s.event_id
                )

        # Don't block waiting on waking up all the listeners.
        d = self.notifier.on_new_room_event(event, extra_users=extra_users)

        def log_failure(f):
            logger.warn(
                "Failed to notify about %s: %s",
                event.event_id, f.value
            )

        d.addErrback(log_failure)

        yield federation_handler.handle_new_event(
            event, destinations=destinations,
        )

    def add_auth_events(self, builder, context):
        yield run_on_reactor()

        auth_ids = self.compute_auth_events(builder, context.current_state)

        auth_events_entries = yield self.store.add_event_hashes(
            auth_ids
        )

        builder.auth_events = auth_events_entries

    def _do_local_membership_update(self, event, context):
        yield run_on_reactor()

        target_user = UserID.from_string(event.state_key)

        yield self.handle_new_client_event(
            event,
            context,
            extra_users=[target_user],
        )

    def _do_shared_secret(self, request, register_json, session):
        yield run_on_reactor()

        if not isinstance(register_json.get("mac", None), string_types):
            raise SynapseError(400, "Expected mac.")
        if not isinstance(register_json.get("user", None), string_types):
            raise SynapseError(400, "Expected 'user' key.")
        if not isinstance(register_json.get("password", None), string_types):
            raise SynapseError(400, "Expected 'password' key.")

        if not self.hs.config.registration_shared_secret:
            raise SynapseError(400, "Shared secret registration is not enabled")

        user = register_json["user"].encode("utf-8")
        password = register_json["password"].encode("utf-8")
        admin = register_json.get("admin", None)

        # Its important to check as we use null bytes as HMAC field separators
        if b"\x00" in user:
            raise SynapseError(400, "Invalid user")
        if b"\x00" in password:
            raise SynapseError(400, "Invalid password")

        # str() because otherwise hmac complains that 'unicode' does not
        # have the buffer interface
        got_mac = str(register_json["mac"])

        want_mac = hmac.new(
            key=self.hs.config.registration_shared_secret.encode(),
            digestmod=sha1,
        )
        want_mac.update(user)
        want_mac.update(b"\x00")
        want_mac.update(password)
        want_mac.update(b"\x00")
        want_mac.update(b"admin" if admin else b"notadmin")
        want_mac = want_mac.hexdigest()

        if compare_digest(want_mac, got_mac):
            handler = self.handlers.registration_handler
            user_id, token = yield handler.register(
                localpart=user.lower(),
                password=password,
                admin=bool(admin),
            )
            self._remove_session(session)
            defer.returnValue({
                "user_id": user_id,
                "access_token": token,
                "home_server": self.hs.hostname,
            })
        else:
            raise SynapseError(
                403, "HMAC incorrect",
            )

    def _do_local_membership_update(self, event, membership, context,
                                    do_auth):
        yield run_on_reactor()

        target_user = self.hs.parse_userid(event.state_key)

        yield self.handle_new_client_event(
            event,
            context,
            extra_users=[target_user],
            suppress_auth=(not do_auth),
        )

    def get_or_create_user(self, localpart, displayname, duration_seconds):
        """Creates a new user if the user does not exist,
        else revokes all previous access tokens and generates a new one.

        Args:
            localpart : The local part of the user ID to register. If None,
              one will be randomly generated.
        Returns:
            A tuple of (user_id, access_token).
        Raises:
            RegistrationError if there was a problem registering.
        """
        yield run_on_reactor()

        if localpart is None:
            raise SynapseError(400, "Request must include user id")

        need_register = True

        try:
            yield self.check_username(localpart)
        except SynapseError as e:
            if e.errcode == Codes.USER_IN_USE:
                need_register = False
            else:
                raise

        user = UserID(localpart, self.hs.hostname)
        user_id = user.to_string()
        auth_handler = self.hs.get_handlers().auth_handler
        token = auth_handler.generate_short_term_login_token(user_id, duration_seconds)

        if need_register:
            yield self.store.register(
                user_id=user_id,
                token=token,
                password_hash=None
            )

            yield registered_user(self.distributor, user)
        else:
            yield self.store.user_delete_access_tokens(user_id=user_id)
            yield self.store.add_access_token_to_user(user_id=user_id, token=token)

        if displayname is not None:
            logger.info("setting user display name: %s -> %s", user_id, displayname)
            profile_handler = self.hs.get_handlers().profile_handler
            yield profile_handler.set_displayname(
                user, Requester(user, token, False), displayname
            )

        defer.returnValue((user_id, token))

    def check_username(self, localpart):
        yield run_on_reactor()

        if urllib.quote(localpart) != localpart:
            raise SynapseError(400, "User ID must only contain characters which do not" " require URL encoding.")

        user = UserID(localpart, self.hs.hostname)
        user_id = user.to_string()

        yield self.check_user_id_is_valid(user_id)

        users = yield self.store.get_users_by_id_case_insensitive(user_id)
        if users:
            raise SynapseError(400, "User ID already taken.", errcode=Codes.USER_IN_USE)

    def get_or_create_user(self, requester, localpart, displayname,
                           password_hash=None):
        """Creates a new user if the user does not exist,
        else revokes all previous access tokens and generates a new one.

        Args:
            localpart : The local part of the user ID to register. If None,
              one will be randomly generated.
        Returns:
            A tuple of (user_id, access_token).
        Raises:
            RegistrationError if there was a problem registering.
        """
        yield run_on_reactor()

        if localpart is None:
            raise SynapseError(400, "Request must include user id")

        need_register = True

        try:
            yield self.check_username(localpart)
        except SynapseError as e:
            if e.errcode == Codes.USER_IN_USE:
                need_register = False
            else:
                raise

        user = UserID(localpart, self.hs.hostname)
        user_id = user.to_string()
        token = self.macaroon_gen.generate_access_token(user_id)

        if need_register:
            yield self.store.register(
                user_id=user_id,
                token=token,
                password_hash=password_hash,
                create_profile_with_localpart=user.localpart,
            )
        else:
            yield self._auth_handler.delete_access_tokens_for_user(user_id)
            yield self.store.add_access_token_to_user(user_id=user_id, token=token)

        if displayname is not None:
            logger.info("setting user display name: %s -> %s", user_id, displayname)
            yield self.profile_handler.set_displayname(
                user, requester, displayname, by_admin=True,
            )

        defer.returnValue((user_id, token))