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-rw-r--r--synapse/handlers/auth.py892
1 files changed, 491 insertions, 401 deletions
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 374372b69e..119678e67b 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -17,14 +17,12 @@
 import logging
 import time
 import unicodedata
+import urllib.parse
+from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple, Union
 
 import attr
-import bcrypt
+import bcrypt  # type: ignore[import]
 import pymacaroons
-from canonicaljson import json
-
-from twisted.internet import defer
-from twisted.web.client import PartialDownloadError
 
 import synapse.util.stringutils as stringutils
 from synapse.api.constants import LoginType
@@ -38,11 +36,15 @@ from synapse.api.errors import (
     UserDeactivatedError,
 )
 from synapse.api.ratelimiting import Ratelimiter
-from synapse.config.emailconfig import ThreepidBehaviour
+from synapse.handlers.ui_auth import INTERACTIVE_AUTH_CHECKERS
+from synapse.handlers.ui_auth.checkers import UserInteractiveAuthChecker
+from synapse.http.server import finish_request
+from synapse.http.site import SynapseRequest
 from synapse.logging.context import defer_to_thread
+from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.module_api import ModuleApi
-from synapse.types import UserID
-from synapse.util.caches.expiringcache import ExpiringCache
+from synapse.push.mailer import load_jinja2_templates
+from synapse.types import Requester, UserID
 
 from ._base import BaseHandler
 
@@ -58,23 +60,14 @@ class AuthHandler(BaseHandler):
             hs (synapse.server.HomeServer):
         """
         super(AuthHandler, self).__init__(hs)
-        self.checkers = {
-            LoginType.RECAPTCHA: self._check_recaptcha,
-            LoginType.EMAIL_IDENTITY: self._check_email_identity,
-            LoginType.MSISDN: self._check_msisdn,
-            LoginType.DUMMY: self._check_dummy_auth,
-            LoginType.TERMS: self._check_terms_auth,
-        }
-        self.bcrypt_rounds = hs.config.bcrypt_rounds
 
-        # This is not a cache per se, but a store of all current sessions that
-        # expire after N hours
-        self.sessions = ExpiringCache(
-            cache_name="register_sessions",
-            clock=hs.get_clock(),
-            expiry_ms=self.SESSION_EXPIRE_MS,
-            reset_expiry_on_get=True,
-        )
+        self.checkers = {}  # type: Dict[str, UserInteractiveAuthChecker]
+        for auth_checker_class in INTERACTIVE_AUTH_CHECKERS:
+            inst = auth_checker_class(hs)
+            if inst.is_enabled():
+                self.checkers[inst.AUTH_TYPE] = inst  # type: ignore
+
+        self.bcrypt_rounds = hs.config.bcrypt_rounds
 
         account_handler = ModuleApi(hs, self)
         self.password_providers = [
@@ -87,6 +80,9 @@ class AuthHandler(BaseHandler):
         self.hs = hs  # FIXME better possibility to access registrationHandler later?
         self.macaroon_gen = hs.get_macaroon_generator()
         self._password_enabled = hs.config.password_enabled
+        self._sso_enabled = (
+            hs.config.cas_enabled or hs.config.saml2_enabled or hs.config.oidc_enabled
+        )
 
         # we keep this as a list despite the O(N^2) implication so that we can
         # keep PASSWORD first and avoid confusing clients which pick the first
@@ -102,14 +98,70 @@ class AuthHandler(BaseHandler):
                     if t not in login_types:
                         login_types.append(t)
         self._supported_login_types = login_types
-
-        self._account_ratelimiter = Ratelimiter()
-        self._failed_attempts_ratelimiter = Ratelimiter()
+        # Login types and UI Auth types have a heavy overlap, but are not
+        # necessarily identical. Login types have SSO (and other login types)
+        # added in the rest layer, see synapse.rest.client.v1.login.LoginRestServerlet.on_GET.
+        ui_auth_types = login_types.copy()
+        if self._sso_enabled:
+            ui_auth_types.append(LoginType.SSO)
+        self._supported_ui_auth_types = ui_auth_types
+
+        # Ratelimiter for failed auth during UIA. Uses same ratelimit config
+        # as per `rc_login.failed_attempts`.
+        self._failed_uia_attempts_ratelimiter = Ratelimiter(
+            clock=self.clock,
+            rate_hz=self.hs.config.rc_login_failed_attempts.per_second,
+            burst_count=self.hs.config.rc_login_failed_attempts.burst_count,
+        )
 
         self._clock = self.hs.get_clock()
 
-    @defer.inlineCallbacks
-    def validate_user_via_ui_auth(self, requester, request_body, clientip):
+        # Expire old UI auth sessions after a period of time.
+        if hs.config.worker_app is None:
+            self._clock.looping_call(
+                run_as_background_process,
+                5 * 60 * 1000,
+                "expire_old_sessions",
+                self._expire_old_sessions,
+            )
+
+        # Load the SSO HTML templates.
+
+        # The following template is shown to the user during a client login via SSO,
+        # after the SSO completes and before redirecting them back to their client.
+        # It notifies the user they are about to give access to their matrix account
+        # to the client.
+        self._sso_redirect_confirm_template = load_jinja2_templates(
+            hs.config.sso_template_dir, ["sso_redirect_confirm.html"],
+        )[0]
+        # The following template is shown during user interactive authentication
+        # in the fallback auth scenario. It notifies the user that they are
+        # authenticating for an operation to occur on their account.
+        self._sso_auth_confirm_template = load_jinja2_templates(
+            hs.config.sso_template_dir, ["sso_auth_confirm.html"],
+        )[0]
+        # The following template is shown after a successful user interactive
+        # authentication session. It tells the user they can close the window.
+        self._sso_auth_success_template = hs.config.sso_auth_success_template
+        # The following template is shown during the SSO authentication process if
+        # the account is deactivated.
+        self._sso_account_deactivated_template = (
+            hs.config.sso_account_deactivated_template
+        )
+
+        self._server_name = hs.config.server_name
+
+        # cast to tuple for use with str.startswith
+        self._whitelisted_sso_clients = tuple(hs.config.sso_client_whitelist)
+
+    async def validate_user_via_ui_auth(
+        self,
+        requester: Requester,
+        request: SynapseRequest,
+        request_body: Dict[str, Any],
+        clientip: str,
+        description: str,
+    ) -> dict:
         """
         Checks that the user is who they claim to be, via a UI auth.
 
@@ -118,14 +170,19 @@ class AuthHandler(BaseHandler):
         that it isn't stolen by re-authenticating them.
 
         Args:
-            requester (Requester): The user, as given by the access token
+            requester: The user, as given by the access token
+
+            request: The request sent by the client.
 
-            request_body (dict): The body of the request sent by the client
+            request_body: The body of the request sent by the client
 
-            clientip (str): The IP address of the client.
+            clientip: The IP address of the client.
+
+            description: A human readable string to be displayed to the user that
+                         describes the operation happening on their account.
 
         Returns:
-            defer.Deferred[dict]: the parameters for this request (which may
+            The parameters for this request (which may
                 have been given only in a previous call).
 
         Raises:
@@ -134,15 +191,31 @@ class AuthHandler(BaseHandler):
 
             AuthError if the client has completed a login flow, and it gives
                 a different user to `requester`
+
+            LimitExceededError if the ratelimiter's failed request count for this
+                user is too high to proceed
+
         """
 
+        user_id = requester.user.to_string()
+
+        # Check if we should be ratelimited due to too many previous failed attempts
+        self._failed_uia_attempts_ratelimiter.ratelimit(user_id, update=False)
+
         # build a list of supported flows
-        flows = [[login_type] for login_type in self._supported_login_types]
+        flows = [[login_type] for login_type in self._supported_ui_auth_types]
 
-        result, params, _ = yield self.check_auth(flows, request_body, clientip)
+        try:
+            result, params, _ = await self.check_auth(
+                flows, request, request_body, clientip, description
+            )
+        except LoginError:
+            # Update the ratelimiter to say we failed (`can_do_action` doesn't raise).
+            self._failed_uia_attempts_ratelimiter.can_do_action(user_id)
+            raise
 
         # find the completed login type
-        for login_type in self._supported_login_types:
+        for login_type in self._supported_ui_auth_types:
             if login_type not in result:
                 continue
 
@@ -158,34 +231,48 @@ class AuthHandler(BaseHandler):
 
         return params
 
-    @defer.inlineCallbacks
-    def check_auth(self, flows, clientdict, clientip):
+    def get_enabled_auth_types(self):
+        """Return the enabled user-interactive authentication types
+
+        Returns the UI-Auth types which are supported by the homeserver's current
+        config.
+        """
+        return self.checkers.keys()
+
+    async def check_auth(
+        self,
+        flows: List[List[str]],
+        request: SynapseRequest,
+        clientdict: Dict[str, Any],
+        clientip: str,
+        description: str,
+    ) -> Tuple[dict, dict, str]:
         """
         Takes a dictionary sent by the client in the login / registration
         protocol and handles the User-Interactive Auth flow.
 
-        As a side effect, this function fills in the 'creds' key on the user's
-        session with a map, which maps each auth-type (str) to the relevant
-        identity authenticated by that auth-type (mostly str, but for captcha, bool).
-
         If no auth flows have been completed successfully, raises an
         InteractiveAuthIncompleteError. To handle this, you can use
         synapse.rest.client.v2_alpha._base.interactive_auth_handler as a
         decorator.
 
         Args:
-            flows (list): A list of login flows. Each flow is an ordered list of
-                          strings representing auth-types. At least one full
-                          flow must be completed in order for auth to be successful.
+            flows: A list of login flows. Each flow is an ordered list of
+                   strings representing auth-types. At least one full
+                   flow must be completed in order for auth to be successful.
+
+            request: The request sent by the client.
 
             clientdict: The dictionary from the client root level, not the
                         'auth' key: this method prompts for auth if none is sent.
 
-            clientip (str): The IP address of the client.
+            clientip: The IP address of the client.
+
+            description: A human readable string to be displayed to the user that
+                         describes the operation happening on their account.
 
         Returns:
-            defer.Deferred[dict, dict, str]: a deferred tuple of
-                (creds, params, session_id).
+            A tuple of (creds, params, session_id).
 
                 'creds' contains the authenticated credentials of each stage.
 
@@ -201,47 +288,93 @@ class AuthHandler(BaseHandler):
         """
 
         authdict = None
-        sid = None
+        sid = None  # type: Optional[str]
         if clientdict and "auth" in clientdict:
             authdict = clientdict["auth"]
             del clientdict["auth"]
             if "session" in authdict:
                 sid = authdict["session"]
-        session = self._get_session_info(sid)
 
-        if len(clientdict) > 0:
+        # Convert the URI and method to strings.
+        uri = request.uri.decode("utf-8")
+        method = request.uri.decode("utf-8")
+
+        # If there's no session ID, create a new session.
+        if not sid:
+            session = await self.store.create_ui_auth_session(
+                clientdict, uri, method, description
+            )
+
+        else:
+            try:
+                session = await self.store.get_ui_auth_session(sid)
+            except StoreError:
+                raise SynapseError(400, "Unknown session ID: %s" % (sid,))
+
+            # If the client provides parameters, update what is persisted,
+            # otherwise use whatever was last provided.
+            #
             # This was designed to allow the client to omit the parameters
             # and just supply the session in subsequent calls so it split
             # auth between devices by just sharing the session, (eg. so you
             # could continue registration from your phone having clicked the
             # email auth link on there). It's probably too open to abuse
             # because it lets unauthenticated clients store arbitrary objects
-            # on a home server.
-            # Revisit: Assumimg the REST APIs do sensible validation, the data
-            # isn't arbintrary.
-            session["clientdict"] = clientdict
-            self._save_session(session)
-        elif "clientdict" in session:
-            clientdict = session["clientdict"]
+            # on a homeserver.
+            #
+            # Revisit: Assuming the REST APIs do sensible validation, the data
+            # isn't arbitrary.
+            #
+            # Note that the registration endpoint explicitly removes the
+            # "initial_device_display_name" parameter if it is provided
+            # without a "password" parameter. See the changes to
+            # synapse.rest.client.v2_alpha.register.RegisterRestServlet.on_POST
+            # in commit 544722bad23fc31056b9240189c3cbbbf0ffd3f9.
+            if not clientdict:
+                clientdict = session.clientdict
+
+            # Ensure that the queried operation does not vary between stages of
+            # the UI authentication session. This is done by generating a stable
+            # comparator and storing it during the initial query. Subsequent
+            # queries ensure that this comparator has not changed.
+            #
+            # The comparator is based on the requested URI and HTTP method. The
+            # client dict (minus the auth dict) should also be checked, but some
+            # clients are not spec compliant, just warn for now if the client
+            # dict changes.
+            if (session.uri, session.method) != (uri, method):
+                raise SynapseError(
+                    403,
+                    "Requested operation has changed during the UI authentication session.",
+                )
+
+            if session.clientdict != clientdict:
+                logger.warning(
+                    "Requested operation has changed during the UI "
+                    "authentication session. A future version of Synapse "
+                    "will remove this capability."
+                )
+
+            # For backwards compatibility, changes to the client dict are
+            # persisted as clients modify them throughout their user interactive
+            # authentication flow.
+            await self.store.set_ui_auth_clientdict(sid, clientdict)
 
         if not authdict:
             raise InteractiveAuthIncompleteError(
-                self._auth_dict_for_flows(flows, session)
+                self._auth_dict_for_flows(flows, session.session_id)
             )
 
-        if "creds" not in session:
-            session["creds"] = {}
-        creds = session["creds"]
-
         # check auth type currently being presented
-        errordict = {}
+        errordict = {}  # type: Dict[str, Any]
         if "type" in authdict:
-            login_type = authdict["type"]
+            login_type = authdict["type"]  # type: str
             try:
-                result = yield self._check_auth_dict(authdict, clientip)
+                result = await self._check_auth_dict(authdict, clientip)
                 if result:
-                    creds[login_type] = result
-                    self._save_session(session)
+                    await self.store.mark_ui_auth_stage_complete(
+                        session.session_id, login_type, result
+                    )
             except LoginError as e:
                 if login_type == LoginType.EMAIL_IDENTITY:
                     # riot used to have a bug where it would request a new
@@ -257,6 +390,7 @@ class AuthHandler(BaseHandler):
                 # so that the client can have another go.
                 errordict = e.error_dict()
 
+        creds = await self.store.get_completed_ui_auth_stages(session.session_id)
         for f in flows:
             if len(set(f) - set(creds)) == 0:
                 # it's very useful to know what args are stored, but this can
@@ -269,15 +403,17 @@ class AuthHandler(BaseHandler):
                     creds,
                     list(clientdict),
                 )
-                return creds, clientdict, session["id"]
 
-        ret = self._auth_dict_for_flows(flows, session)
+                return creds, clientdict, session.session_id
+
+        ret = self._auth_dict_for_flows(flows, session.session_id)
         ret["completed"] = list(creds)
         ret.update(errordict)
         raise InteractiveAuthIncompleteError(ret)
 
-    @defer.inlineCallbacks
-    def add_oob_auth(self, stagetype, authdict, clientip):
+    async def add_oob_auth(
+        self, stagetype: str, authdict: Dict[str, Any], clientip: str
+    ) -> bool:
         """
         Adds the result of out-of-band authentication into an existing auth
         session. Currently used for adding the result of fallback auth.
@@ -287,19 +423,15 @@ class AuthHandler(BaseHandler):
         if "session" not in authdict:
             raise LoginError(400, "", Codes.MISSING_PARAM)
 
-        sess = self._get_session_info(authdict["session"])
-        if "creds" not in sess:
-            sess["creds"] = {}
-        creds = sess["creds"]
-
-        result = yield self.checkers[stagetype](authdict, clientip)
+        result = await self.checkers[stagetype].check_auth(authdict, clientip)
         if result:
-            creds[stagetype] = result
-            self._save_session(sess)
+            await self.store.mark_ui_auth_stage_complete(
+                authdict["session"], stagetype, result
+            )
             return True
         return False
 
-    def get_session_id(self, clientdict):
+    def get_session_id(self, clientdict: Dict[str, Any]) -> Optional[str]:
         """
         Gets the session ID for a client given the client dictionary
 
@@ -307,7 +439,7 @@ class AuthHandler(BaseHandler):
             clientdict: The dictionary sent by the client in the request
 
         Returns:
-            str|None: The string session ID the client sent. If the client did
+            The string session ID the client sent. If the client did
                 not send a session ID, returns None.
         """
         sid = None
@@ -317,43 +449,57 @@ class AuthHandler(BaseHandler):
                 sid = authdict["session"]
         return sid
 
-    def set_session_data(self, session_id, key, value):
+    async def set_session_data(self, session_id: str, key: str, value: Any) -> None:
         """
         Store a key-value pair into the sessions data associated with this
         request. This data is stored server-side and cannot be modified by
         the client.
 
         Args:
-            session_id (string): The ID of this session as returned from check_auth
-            key (string): The key to store the data under
-            value (any): The data to store
+            session_id: The ID of this session as returned from check_auth
+            key: The key to store the data under
+            value: The data to store
         """
-        sess = self._get_session_info(session_id)
-        sess.setdefault("serverdict", {})[key] = value
-        self._save_session(sess)
+        try:
+            await self.store.set_ui_auth_session_data(session_id, key, value)
+        except StoreError:
+            raise SynapseError(400, "Unknown session ID: %s" % (session_id,))
 
-    def get_session_data(self, session_id, key, default=None):
+    async def get_session_data(
+        self, session_id: str, key: str, default: Optional[Any] = None
+    ) -> Any:
         """
         Retrieve data stored with set_session_data
 
         Args:
-            session_id (string): The ID of this session as returned from check_auth
-            key (string): The key to store the data under
-            default (any): Value to return if the key has not been set
+            session_id: The ID of this session as returned from check_auth
+            key: The key to store the data under
+            default: Value to return if the key has not been set
         """
-        sess = self._get_session_info(session_id)
-        return sess.setdefault("serverdict", {}).get(key, default)
+        try:
+            return await self.store.get_ui_auth_session_data(session_id, key, default)
+        except StoreError:
+            raise SynapseError(400, "Unknown session ID: %s" % (session_id,))
 
-    @defer.inlineCallbacks
-    def _check_auth_dict(self, authdict, clientip):
+    async def _expire_old_sessions(self):
+        """
+        Invalidate any user interactive authentication sessions that have expired.
+        """
+        now = self._clock.time_msec()
+        expiration_time = now - self.SESSION_EXPIRE_MS
+        await self.store.delete_old_ui_auth_sessions(expiration_time)
+
+    async def _check_auth_dict(
+        self, authdict: Dict[str, Any], clientip: str
+    ) -> Union[Dict[str, Any], str]:
         """Attempt to validate the auth dict provided by a client
 
         Args:
-            authdict (object): auth dict provided by the client
-            clientip (str): IP address of the client
+            authdict: auth dict provided by the client
+            clientip: IP address of the client
 
         Returns:
-            Deferred: result of the stage verification.
+            Result of the stage verification.
 
         Raises:
             StoreError if there was a problem accessing the database
@@ -363,7 +509,7 @@ class AuthHandler(BaseHandler):
         login_type = authdict["type"]
         checker = self.checkers.get(login_type)
         if checker is not None:
-            res = yield checker(authdict, clientip=clientip)
+            res = await checker.check_auth(authdict, clientip=clientip)
             return res
 
         # build a v1-login-style dict out of the authdict and fall back to the
@@ -373,132 +519,13 @@ class AuthHandler(BaseHandler):
         if user_id is None:
             raise SynapseError(400, "", Codes.MISSING_PARAM)
 
-        (canonical_id, callback) = yield self.validate_login(user_id, authdict)
+        (canonical_id, callback) = await self.validate_login(user_id, authdict)
         return canonical_id
 
-    @defer.inlineCallbacks
-    def _check_recaptcha(self, authdict, clientip, **kwargs):
-        try:
-            user_response = authdict["response"]
-        except KeyError:
-            # Client tried to provide captcha but didn't give the parameter:
-            # bad request.
-            raise LoginError(
-                400, "Captcha response is required", errcode=Codes.CAPTCHA_NEEDED
-            )
-
-        logger.info(
-            "Submitting recaptcha response %s with remoteip %s", user_response, clientip
-        )
-
-        # TODO: get this from the homeserver rather than creating a new one for
-        # each request
-        try:
-            client = self.hs.get_simple_http_client()
-            resp_body = yield client.post_urlencoded_get_json(
-                self.hs.config.recaptcha_siteverify_api,
-                args={
-                    "secret": self.hs.config.recaptcha_private_key,
-                    "response": user_response,
-                    "remoteip": clientip,
-                },
-            )
-        except PartialDownloadError as pde:
-            # Twisted is silly
-            data = pde.response
-            resp_body = json.loads(data)
-
-        if "success" in resp_body:
-            # Note that we do NOT check the hostname here: we explicitly
-            # intend the CAPTCHA to be presented by whatever client the
-            # user is using, we just care that they have completed a CAPTCHA.
-            logger.info(
-                "%s reCAPTCHA from hostname %s",
-                "Successful" if resp_body["success"] else "Failed",
-                resp_body.get("hostname"),
-            )
-            if resp_body["success"]:
-                return True
-        raise LoginError(401, "", errcode=Codes.UNAUTHORIZED)
-
-    def _check_email_identity(self, authdict, **kwargs):
-        return self._check_threepid("email", authdict, **kwargs)
-
-    def _check_msisdn(self, authdict, **kwargs):
-        return self._check_threepid("msisdn", authdict)
-
-    def _check_dummy_auth(self, authdict, **kwargs):
-        return defer.succeed(True)
-
-    def _check_terms_auth(self, authdict, **kwargs):
-        return defer.succeed(True)
-
-    @defer.inlineCallbacks
-    def _check_threepid(self, medium, authdict, **kwargs):
-        if "threepid_creds" not in authdict:
-            raise LoginError(400, "Missing threepid_creds", Codes.MISSING_PARAM)
-
-        threepid_creds = authdict["threepid_creds"]
-
-        identity_handler = self.hs.get_handlers().identity_handler
-
-        logger.info("Getting validated threepid. threepidcreds: %r", (threepid_creds,))
-        if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
-            if medium == "email":
-                threepid = yield identity_handler.threepid_from_creds(
-                    self.hs.config.account_threepid_delegate_email, threepid_creds
-                )
-            elif medium == "msisdn":
-                threepid = yield identity_handler.threepid_from_creds(
-                    self.hs.config.account_threepid_delegate_msisdn, threepid_creds
-                )
-            else:
-                raise SynapseError(400, "Unrecognized threepid medium: %s" % (medium,))
-        elif self.hs.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            row = yield self.store.get_threepid_validation_session(
-                medium,
-                threepid_creds["client_secret"],
-                sid=threepid_creds["sid"],
-                validated=True,
-            )
-
-            threepid = (
-                {
-                    "medium": row["medium"],
-                    "address": row["address"],
-                    "validated_at": row["validated_at"],
-                }
-                if row
-                else None
-            )
-
-            if row:
-                # Valid threepid returned, delete from the db
-                yield self.store.delete_threepid_session(threepid_creds["sid"])
-        else:
-            raise SynapseError(
-                400, "Password resets are not enabled on this homeserver"
-            )
-
-        if not threepid:
-            raise LoginError(401, "", errcode=Codes.UNAUTHORIZED)
-
-        if threepid["medium"] != medium:
-            raise LoginError(
-                401,
-                "Expecting threepid of type '%s', got '%s'"
-                % (medium, threepid["medium"]),
-                errcode=Codes.UNAUTHORIZED,
-            )
-
-        threepid["threepid_creds"] = authdict["threepid_creds"]
-
-        return threepid
-
-    def _get_params_recaptcha(self):
+    def _get_params_recaptcha(self) -> dict:
         return {"public_key": self.hs.config.recaptcha_public_key}
 
-    def _get_params_terms(self):
+    def _get_params_terms(self) -> dict:
         return {
             "policies": {
                 "privacy_policy": {
@@ -515,7 +542,9 @@ class AuthHandler(BaseHandler):
             }
         }
 
-    def _auth_dict_for_flows(self, flows, session):
+    def _auth_dict_for_flows(
+        self, flows: List[List[str]], session_id: str,
+    ) -> Dict[str, Any]:
         public_flows = []
         for f in flows:
             public_flows.append(f)
@@ -525,7 +554,7 @@ class AuthHandler(BaseHandler):
             LoginType.TERMS: self._get_params_terms,
         }
 
-        params = {}
+        params = {}  # type: Dict[str, Any]
 
         for f in public_flows:
             for stage in f:
@@ -533,25 +562,14 @@ class AuthHandler(BaseHandler):
                     params[stage] = get_params[stage]()
 
         return {
-            "session": session["id"],
+            "session": session_id,
             "flows": [{"stages": f} for f in public_flows],
             "params": params,
         }
 
-    def _get_session_info(self, session_id):
-        if session_id not in self.sessions:
-            session_id = None
-
-        if not session_id:
-            # create a new session
-            while session_id is None or session_id in self.sessions:
-                session_id = stringutils.random_string(24)
-            self.sessions[session_id] = {"id": session_id}
-
-        return self.sessions[session_id]
-
-    @defer.inlineCallbacks
-    def get_access_token_for_user_id(self, user_id, device_id, valid_until_ms):
+    async def get_access_token_for_user_id(
+        self, user_id: str, device_id: Optional[str], valid_until_ms: Optional[int]
+    ):
         """
         Creates a new access token for the user with the given user ID.
 
@@ -561,11 +579,11 @@ class AuthHandler(BaseHandler):
         The device will be recorded in the table if it is not there already.
 
         Args:
-            user_id (str): canonical User ID
-            device_id (str|None): the device ID to associate with the tokens.
+            user_id: canonical User ID
+            device_id: the device ID to associate with the tokens.
                None to leave the tokens unassociated with a device (deprecated:
                we should always have a device ID)
-            valid_until_ms (int|None): when the token is valid until. None for
+            valid_until_ms: when the token is valid until. None for
                 no expiry.
         Returns:
               The access token for the user's session.
@@ -579,10 +597,10 @@ class AuthHandler(BaseHandler):
             )
         logger.info("Logging in user %s on device %s%s", user_id, device_id, fmt_expiry)
 
-        yield self.auth.check_auth_blocking(user_id)
+        await self.auth.check_auth_blocking(user_id)
 
         access_token = self.macaroon_gen.generate_access_token(user_id)
-        yield self.store.add_access_token_to_user(
+        await self.store.add_access_token_to_user(
             user_id, access_token, device_id, valid_until_ms
         )
 
@@ -592,52 +610,45 @@ class AuthHandler(BaseHandler):
         # device, so we double-check it here.
         if device_id is not None:
             try:
-                yield self.store.get_device(user_id, device_id)
+                await self.store.get_device(user_id, device_id)
             except StoreError:
-                yield self.store.delete_access_token(access_token)
+                await self.store.delete_access_token(access_token)
                 raise StoreError(400, "Login raced against device deletion")
 
         return access_token
 
-    @defer.inlineCallbacks
-    def check_user_exists(self, user_id):
+    async def check_user_exists(self, user_id: str) -> Optional[str]:
         """
         Checks to see if a user with the given id exists. Will check case
         insensitively, but return None if there are multiple inexact matches.
 
         Args:
-            (unicode|bytes) user_id: complete @user:id
+            user_id: complete @user:id
 
         Returns:
-            defer.Deferred: (unicode) canonical_user_id, or None if zero or
-            multiple matches
-
-        Raises:
-            LimitExceededError if the ratelimiter's login requests count for this
-                user is too high too proceed.
-            UserDeactivatedError if a user is found but is deactivated.
+            The canonical_user_id, or None if zero or multiple matches
         """
-        self.ratelimit_login_per_account(user_id)
-        res = yield self._find_user_id_and_pwd_hash(user_id)
+        res = await self._find_user_id_and_pwd_hash(user_id)
         if res is not None:
             return res[0]
         return None
 
-    @defer.inlineCallbacks
-    def _find_user_id_and_pwd_hash(self, user_id):
+    async def _find_user_id_and_pwd_hash(
+        self, user_id: str
+    ) -> Optional[Tuple[str, str]]:
         """Checks to see if a user with the given id exists. Will check case
         insensitively, but will return None if there are multiple inexact
         matches.
 
         Returns:
-            tuple: A 2-tuple of `(canonical_user_id, password_hash)`
-            None: if there is not exactly one match
+            A 2-tuple of `(canonical_user_id, password_hash)` or `None`
+            if there is not exactly one match
         """
-        user_infos = yield self.store.get_users_by_id_case_insensitive(user_id)
+        user_infos = await self.store.get_users_by_id_case_insensitive(user_id)
 
         result = None
         if not user_infos:
-            logger.warn("Attempted to login as %s but they do not exist", user_id)
+            logger.warning("Attempted to login as %s but they do not exist", user_id)
         elif len(user_infos) == 1:
             # a single match (possibly not exact)
             result = user_infos.popitem()
@@ -646,7 +657,7 @@ class AuthHandler(BaseHandler):
             result = (user_id, user_infos[user_id])
         else:
             # multiple matches, none of them exact
-            logger.warn(
+            logger.warning(
                 "Attempted to login as %s but it matches more than one user "
                 "inexactly: %r",
                 user_id,
@@ -654,7 +665,7 @@ class AuthHandler(BaseHandler):
             )
         return result
 
-    def get_supported_login_types(self):
+    def get_supported_login_types(self) -> Iterable[str]:
         """Get a the login types supported for the /login API
 
         By default this is just 'm.login.password' (unless password_enabled is
@@ -662,30 +673,29 @@ class AuthHandler(BaseHandler):
         other login types.
 
         Returns:
-            Iterable[str]: login types
+            login types
         """
         return self._supported_login_types
 
-    @defer.inlineCallbacks
-    def validate_login(self, username, login_submission):
+    async def validate_login(
+        self, username: str, login_submission: Dict[str, Any]
+    ) -> Tuple[str, Optional[Callable[[Dict[str, str]], None]]]:
         """Authenticates the user for the /login API
 
         Also used by the user-interactive auth flow to validate
         m.login.password auth types.
 
         Args:
-            username (str): username supplied by the user
-            login_submission (dict): the whole of the login submission
+            username: username supplied by the user
+            login_submission: the whole of the login submission
                 (including 'type' and other relevant fields)
         Returns:
-            Deferred[str, func]: canonical user id, and optional callback
+            A tuple of the canonical user id, and optional callback
                 to be called once the access token and device id are issued
         Raises:
             StoreError if there was a problem accessing the database
             SynapseError if there was a problem with the request
             LoginError if there was an authentication problem.
-            LimitExceededError if the ratelimiter's login requests count for this
-                user is too high too proceed.
         """
 
         if username.startswith("@"):
@@ -693,8 +703,6 @@ class AuthHandler(BaseHandler):
         else:
             qualified_user_id = UserID(username, self.hs.hostname).to_string()
 
-        self.ratelimit_login_per_account(qualified_user_id)
-
         login_type = login_submission.get("type")
         known_login_type = False
 
@@ -711,7 +719,7 @@ class AuthHandler(BaseHandler):
         for provider in self.password_providers:
             if hasattr(provider, "check_password") and login_type == LoginType.PASSWORD:
                 known_login_type = True
-                is_valid = yield provider.check_password(qualified_user_id, password)
+                is_valid = await provider.check_password(qualified_user_id, password)
                 if is_valid:
                     return qualified_user_id, None
 
@@ -743,7 +751,7 @@ class AuthHandler(BaseHandler):
                     % (login_type, missing_fields),
                 )
 
-            result = yield provider.check_auth(username, login_type, login_dict)
+            result = await provider.check_auth(username, login_type, login_dict)
             if result:
                 if isinstance(result, str):
                     result = (result, None)
@@ -752,8 +760,8 @@ class AuthHandler(BaseHandler):
         if login_type == LoginType.PASSWORD and self.hs.config.password_localdb_enabled:
             known_login_type = True
 
-            canonical_user_id = yield self._check_local_password(
-                qualified_user_id, password
+            canonical_user_id = await self._check_local_password(
+                qualified_user_id, password  # type: ignore
             )
 
             if canonical_user_id:
@@ -762,32 +770,23 @@ class AuthHandler(BaseHandler):
         if not known_login_type:
             raise SynapseError(400, "Unknown login type %s" % login_type)
 
-        # unknown username or invalid password.
-        self._failed_attempts_ratelimiter.ratelimit(
-            qualified_user_id.lower(),
-            time_now_s=self._clock.time(),
-            rate_hz=self.hs.config.rc_login_failed_attempts.per_second,
-            burst_count=self.hs.config.rc_login_failed_attempts.burst_count,
-            update=True,
-        )
-
         # We raise a 403 here, but note that if we're doing user-interactive
         # login, it turns all LoginErrors into a 401 anyway.
         raise LoginError(403, "Invalid password", errcode=Codes.FORBIDDEN)
 
-    @defer.inlineCallbacks
-    def check_password_provider_3pid(self, medium, address, password):
+    async def check_password_provider_3pid(
+        self, medium: str, address: str, password: str
+    ) -> Tuple[Optional[str], Optional[Callable[[Dict[str, str]], None]]]:
         """Check if a password provider is able to validate a thirdparty login
 
         Args:
-            medium (str): The medium of the 3pid (ex. email).
-            address (str): The address of the 3pid (ex. jdoe@example.com).
-            password (str): The password of the user.
+            medium: The medium of the 3pid (ex. email).
+            address: The address of the 3pid (ex. jdoe@example.com).
+            password: The password of the user.
 
         Returns:
-            Deferred[(str|None, func|None)]: A tuple of `(user_id,
-            callback)`. If authentication is successful, `user_id` is a `str`
-            containing the authenticated, canonical user ID. `callback` is
+            A tuple of `(user_id, callback)`. If authentication is successful,
+            `user_id`is the authenticated, canonical user ID. `callback` is
             then either a function to be later run after the server has
             completed login/registration, or `None`. If authentication was
             unsuccessful, `user_id` and `callback` are both `None`.
@@ -799,7 +798,7 @@ class AuthHandler(BaseHandler):
                 # success, to a str (which is the user_id) or a tuple of
                 # (user_id, callback_func), where callback_func should be run
                 # after we've finished everything else
-                result = yield provider.check_3pid_auth(medium, address, password)
+                result = await provider.check_3pid_auth(medium, address, password)
                 if result:
                     # Check if the return value is a str or a tuple
                     if isinstance(result, str):
@@ -809,43 +808,36 @@ class AuthHandler(BaseHandler):
 
         return None, None
 
-    @defer.inlineCallbacks
-    def _check_local_password(self, user_id, password):
+    async def _check_local_password(self, user_id: str, password: str) -> Optional[str]:
         """Authenticate a user against the local password database.
 
         user_id is checked case insensitively, but will return None if there are
         multiple inexact matches.
 
         Args:
-            user_id (unicode): complete @user:id
-            password (unicode): the provided password
+            user_id: complete @user:id
+            password: the provided password
         Returns:
-            Deferred[unicode] the canonical_user_id, or Deferred[None] if
-                unknown user/bad password
-
-        Raises:
-            LimitExceededError if the ratelimiter's login requests count for this
-                user is too high too proceed.
+            The canonical_user_id, or None if unknown user/bad password
         """
-        lookupres = yield self._find_user_id_and_pwd_hash(user_id)
+        lookupres = await self._find_user_id_and_pwd_hash(user_id)
         if not lookupres:
             return None
         (user_id, password_hash) = lookupres
 
         # If the password hash is None, the account has likely been deactivated
         if not password_hash:
-            deactivated = yield self.store.get_user_deactivated_status(user_id)
+            deactivated = await self.store.get_user_deactivated_status(user_id)
             if deactivated:
                 raise UserDeactivatedError("This account has been deactivated")
 
-        result = yield self.validate_hash(password, password_hash)
+        result = await self.validate_hash(password, password_hash)
         if not result:
-            logger.warn("Failed password login for user %s", user_id)
+            logger.warning("Failed password login for user %s", user_id)
             return None
         return user_id
 
-    @defer.inlineCallbacks
-    def validate_short_term_login_token_and_get_user_id(self, login_token):
+    async def validate_short_term_login_token_and_get_user_id(self, login_token: str):
         auth_api = self.hs.get_auth()
         user_id = None
         try:
@@ -854,27 +846,24 @@ class AuthHandler(BaseHandler):
             auth_api.validate_macaroon(macaroon, "login", user_id)
         except Exception:
             raise AuthError(403, "Invalid token", errcode=Codes.FORBIDDEN)
-        self.ratelimit_login_per_account(user_id)
-        yield self.auth.check_auth_blocking(user_id)
+
+        await self.auth.check_auth_blocking(user_id)
         return user_id
 
-    @defer.inlineCallbacks
-    def delete_access_token(self, access_token):
+    async def delete_access_token(self, access_token: str):
         """Invalidate a single access token
 
         Args:
-            access_token (str): access token to be deleted
+            access_token: access token to be deleted
 
-        Returns:
-            Deferred
         """
-        user_info = yield self.auth.get_user_by_access_token(access_token)
-        yield self.store.delete_access_token(access_token)
+        user_info = await self.auth.get_user_by_access_token(access_token)
+        await self.store.delete_access_token(access_token)
 
         # see if any of our auth providers want to know about this
         for provider in self.password_providers:
             if hasattr(provider, "on_logged_out"):
-                yield provider.on_logged_out(
+                await provider.on_logged_out(
                     user_id=str(user_info["user"]),
                     device_id=user_info["device_id"],
                     access_token=access_token,
@@ -882,27 +871,26 @@ class AuthHandler(BaseHandler):
 
         # delete pushers associated with this access token
         if user_info["token_id"] is not None:
-            yield self.hs.get_pusherpool().remove_pushers_by_access_token(
+            await self.hs.get_pusherpool().remove_pushers_by_access_token(
                 str(user_info["user"]), (user_info["token_id"],)
             )
 
-    @defer.inlineCallbacks
-    def delete_access_tokens_for_user(
-        self, user_id, except_token_id=None, device_id=None
+    async def delete_access_tokens_for_user(
+        self,
+        user_id: str,
+        except_token_id: Optional[str] = None,
+        device_id: Optional[str] = None,
     ):
         """Invalidate access tokens belonging to a user
 
         Args:
-            user_id (str):  ID of user the tokens belong to
-            except_token_id (str|None): access_token ID which should *not* be
-                deleted
-            device_id (str|None):  ID of device the tokens are associated with.
+            user_id:  ID of user the tokens belong to
+            except_token_id: access_token ID which should *not* be deleted
+            device_id:  ID of device the tokens are associated with.
                 If None, tokens associated with any device (or no device) will
                 be deleted
-        Returns:
-            Deferred
         """
-        tokens_and_devices = yield self.store.user_delete_access_tokens(
+        tokens_and_devices = await self.store.user_delete_access_tokens(
             user_id, except_token_id=except_token_id, device_id=device_id
         )
 
@@ -910,19 +898,28 @@ class AuthHandler(BaseHandler):
         for provider in self.password_providers:
             if hasattr(provider, "on_logged_out"):
                 for token, token_id, device_id in tokens_and_devices:
-                    yield provider.on_logged_out(
+                    await provider.on_logged_out(
                         user_id=user_id, device_id=device_id, access_token=token
                     )
 
         # delete pushers associated with the access tokens
-        yield self.hs.get_pusherpool().remove_pushers_by_access_token(
+        await self.hs.get_pusherpool().remove_pushers_by_access_token(
             user_id, (token_id for _, token_id, _ in tokens_and_devices)
         )
 
-    @defer.inlineCallbacks
-    def add_threepid(self, user_id, medium, address, validated_at):
+    async def add_threepid(
+        self, user_id: str, medium: str, address: str, validated_at: int
+    ):
+        # check if medium has a valid value
+        if medium not in ["email", "msisdn"]:
+            raise SynapseError(
+                code=400,
+                msg=("'%s' is not a valid value for 'medium'" % (medium,)),
+                errcode=Codes.INVALID_PARAM,
+            )
+
         # 'Canonicalise' email addresses down to lower case.
-        # We've now moving towards the Home Server being the entity that
+        # We've now moving towards the homeserver being the entity that
         # is responsible for validating threepids used for resetting passwords
         # on accounts, so in future Synapse will gain knowledge of specific
         # types (mediums) of threepid. For now, we still use the existing
@@ -933,26 +930,26 @@ class AuthHandler(BaseHandler):
         if medium == "email":
             address = address.lower()
 
-        yield self.store.user_add_threepid(
+        await self.store.user_add_threepid(
             user_id, medium, address, validated_at, self.hs.get_clock().time_msec()
         )
 
-    @defer.inlineCallbacks
-    def delete_threepid(self, user_id, medium, address, id_server=None):
+    async def delete_threepid(
+        self, user_id: str, medium: str, address: str, id_server: Optional[str] = None
+    ) -> bool:
         """Attempts to unbind the 3pid on the identity servers and deletes it
         from the local database.
 
         Args:
-            user_id (str)
-            medium (str)
-            address (str)
-            id_server (str|None): Use the given identity server when unbinding
+            user_id: ID of user to remove the 3pid from.
+            medium: The medium of the 3pid being removed: "email" or "msisdn".
+            address: The 3pid address to remove.
+            id_server: Use the given identity server when unbinding
                 any threepids. If None then will attempt to unbind using the
                 identity server specified when binding (if known).
 
-
         Returns:
-            Deferred[bool]: Returns True if successfully unbound the 3pid on
+            Returns True if successfully unbound the 3pid on
             the identity server, False if identity server doesn't support the
             unbind API.
         """
@@ -962,27 +959,21 @@ class AuthHandler(BaseHandler):
             address = address.lower()
 
         identity_handler = self.hs.get_handlers().identity_handler
-        result = yield identity_handler.try_unbind_threepid(
+        result = await identity_handler.try_unbind_threepid(
             user_id, {"medium": medium, "address": address, "id_server": id_server}
         )
 
-        yield self.store.user_delete_threepid(user_id, medium, address)
+        await self.store.user_delete_threepid(user_id, medium, address)
         return result
 
-    def _save_session(self, session):
-        # TODO: Persistent storage
-        logger.debug("Saving session %s", session)
-        session["last_used"] = self.hs.get_clock().time_msec()
-        self.sessions[session["id"]] = session
-
-    def hash(self, password):
+    async def hash(self, password: str) -> str:
         """Computes a secure hash of password.
 
         Args:
-            password (unicode): Password to hash.
+            password: Password to hash.
 
         Returns:
-            Deferred(unicode): Hashed password.
+            Hashed password.
         """
 
         def _do_hash():
@@ -994,17 +985,19 @@ class AuthHandler(BaseHandler):
                 bcrypt.gensalt(self.bcrypt_rounds),
             ).decode("ascii")
 
-        return defer_to_thread(self.hs.get_reactor(), _do_hash)
+        return await defer_to_thread(self.hs.get_reactor(), _do_hash)
 
-    def validate_hash(self, password, stored_hash):
+    async def validate_hash(
+        self, password: str, stored_hash: Union[bytes, str]
+    ) -> bool:
         """Validates that self.hash(password) == stored_hash.
 
         Args:
-            password (unicode): Password to hash.
-            stored_hash (bytes): Expected hash value.
+            password: Password to hash.
+            stored_hash: Expected hash value.
 
         Returns:
-            Deferred(bool): Whether self.hash(password) == stored_hash.
+            Whether self.hash(password) == stored_hash.
         """
 
         def _do_validate_hash():
@@ -1020,46 +1013,150 @@ class AuthHandler(BaseHandler):
             if not isinstance(stored_hash, bytes):
                 stored_hash = stored_hash.encode("ascii")
 
-            return defer_to_thread(self.hs.get_reactor(), _do_validate_hash)
+            return await defer_to_thread(self.hs.get_reactor(), _do_validate_hash)
         else:
-            return defer.succeed(False)
+            return False
 
-    def ratelimit_login_per_account(self, user_id):
-        """Checks whether the process must be stopped because of ratelimiting.
+    async def start_sso_ui_auth(self, redirect_url: str, session_id: str) -> str:
+        """
+        Get the HTML for the SSO redirect confirmation page.
+
+        Args:
+            redirect_url: The URL to redirect to the SSO provider.
+            session_id: The user interactive authentication session ID.
 
-        Checks against two ratelimiters: the generic one for login attempts per
-        account and the one specific to failed attempts.
+        Returns:
+            The HTML to render.
+        """
+        try:
+            session = await self.store.get_ui_auth_session(session_id)
+        except StoreError:
+            raise SynapseError(400, "Unknown session ID: %s" % (session_id,))
+        return self._sso_auth_confirm_template.render(
+            description=session.description, redirect_url=redirect_url,
+        )
+
+    async def complete_sso_ui_auth(
+        self, registered_user_id: str, session_id: str, request: SynapseRequest,
+    ):
+        """Having figured out a mxid for this user, complete the HTTP request
 
         Args:
-            user_id (unicode): complete @user:id
+            registered_user_id: The registered user ID to complete SSO login for.
+            request: The request to complete.
+            client_redirect_url: The URL to which to redirect the user at the end of the
+                process.
+        """
+        # Mark the stage of the authentication as successful.
+        # Save the user who authenticated with SSO, this will be used to ensure
+        # that the account be modified is also the person who logged in.
+        await self.store.mark_ui_auth_stage_complete(
+            session_id, LoginType.SSO, registered_user_id
+        )
 
-        Raises:
-            LimitExceededError if one of the ratelimiters' login requests count
-                for this user is too high too proceed.
+        # Render the HTML and return.
+        html_bytes = self._sso_auth_success_template.encode("utf-8")
+        request.setResponseCode(200)
+        request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+        request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
+
+        request.write(html_bytes)
+        finish_request(request)
+
+    async def complete_sso_login(
+        self,
+        registered_user_id: str,
+        request: SynapseRequest,
+        client_redirect_url: str,
+    ):
+        """Having figured out a mxid for this user, complete the HTTP request
+
+        Args:
+            registered_user_id: The registered user ID to complete SSO login for.
+            request: The request to complete.
+            client_redirect_url: The URL to which to redirect the user at the end of the
+                process.
         """
-        self._failed_attempts_ratelimiter.ratelimit(
-            user_id.lower(),
-            time_now_s=self._clock.time(),
-            rate_hz=self.hs.config.rc_login_failed_attempts.per_second,
-            burst_count=self.hs.config.rc_login_failed_attempts.burst_count,
-            update=False,
+        # If the account has been deactivated, do not proceed with the login
+        # flow.
+        deactivated = await self.store.get_user_deactivated_status(registered_user_id)
+        if deactivated:
+            html_bytes = self._sso_account_deactivated_template.encode("utf-8")
+
+            request.setResponseCode(403)
+            request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+            request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
+            request.write(html_bytes)
+            finish_request(request)
+            return
+
+        self._complete_sso_login(registered_user_id, request, client_redirect_url)
+
+    def _complete_sso_login(
+        self,
+        registered_user_id: str,
+        request: SynapseRequest,
+        client_redirect_url: str,
+    ):
+        """
+        The synchronous portion of complete_sso_login.
+
+        This exists purely for backwards compatibility of synapse.module_api.ModuleApi.
+        """
+        # Create a login token
+        login_token = self.macaroon_gen.generate_short_term_login_token(
+            registered_user_id
         )
 
-        self._account_ratelimiter.ratelimit(
-            user_id.lower(),
-            time_now_s=self._clock.time(),
-            rate_hz=self.hs.config.rc_login_account.per_second,
-            burst_count=self.hs.config.rc_login_account.burst_count,
-            update=True,
+        # Append the login token to the original redirect URL (i.e. with its query
+        # parameters kept intact) to build the URL to which the template needs to
+        # redirect the users once they have clicked on the confirmation link.
+        redirect_url = self.add_query_param_to_url(
+            client_redirect_url, "loginToken", login_token
         )
 
+        # if the client is whitelisted, we can redirect straight to it
+        if client_redirect_url.startswith(self._whitelisted_sso_clients):
+            request.redirect(redirect_url)
+            finish_request(request)
+            return
+
+        # Otherwise, serve the redirect confirmation page.
+
+        # Remove the query parameters from the redirect URL to get a shorter version of
+        # it. This is only to display a human-readable URL in the template, but not the
+        # URL we redirect users to.
+        redirect_url_no_params = client_redirect_url.split("?")[0]
+
+        html_bytes = self._sso_redirect_confirm_template.render(
+            display_url=redirect_url_no_params,
+            redirect_url=redirect_url,
+            server_name=self._server_name,
+        ).encode("utf-8")
+
+        request.setResponseCode(200)
+        request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+        request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
+        request.write(html_bytes)
+        finish_request(request)
+
+    @staticmethod
+    def add_query_param_to_url(url: str, param_name: str, param: Any):
+        url_parts = list(urllib.parse.urlparse(url))
+        query = dict(urllib.parse.parse_qsl(url_parts[4]))
+        query.update({param_name: param})
+        url_parts[4] = urllib.parse.urlencode(query)
+        return urllib.parse.urlunparse(url_parts)
+
 
 @attr.s
 class MacaroonGenerator(object):
 
     hs = attr.ib()
 
-    def generate_access_token(self, user_id, extra_caveats=None):
+    def generate_access_token(
+        self, user_id: str, extra_caveats: Optional[List[str]] = None
+    ) -> str:
         extra_caveats = extra_caveats or []
         macaroon = self._generate_base_macaroon(user_id)
         macaroon.add_first_party_caveat("type = access")
@@ -1072,16 +1169,9 @@ class MacaroonGenerator(object):
             macaroon.add_first_party_caveat(caveat)
         return macaroon.serialize()
 
-    def generate_short_term_login_token(self, user_id, duration_in_ms=(2 * 60 * 1000)):
-        """
-
-        Args:
-            user_id (unicode):
-            duration_in_ms (int):
-
-        Returns:
-            unicode
-        """
+    def generate_short_term_login_token(
+        self, user_id: str, duration_in_ms: int = (2 * 60 * 1000)
+    ) -> str:
         macaroon = self._generate_base_macaroon(user_id)
         macaroon.add_first_party_caveat("type = login")
         now = self.hs.get_clock().time_msec()
@@ -1089,12 +1179,12 @@ class MacaroonGenerator(object):
         macaroon.add_first_party_caveat("time < %d" % (expiry,))
         return macaroon.serialize()
 
-    def generate_delete_pusher_token(self, user_id):
+    def generate_delete_pusher_token(self, user_id: str) -> str:
         macaroon = self._generate_base_macaroon(user_id)
         macaroon.add_first_party_caveat("type = delete_pusher")
         return macaroon.serialize()
 
-    def _generate_base_macaroon(self, user_id):
+    def _generate_base_macaroon(self, user_id: str) -> pymacaroons.Macaroon:
         macaroon = pymacaroons.Macaroon(
             location=self.hs.config.server_name,
             identifier="key",