Merge pull request #3534 from krombel/use_parse_and_asserts_from_servlet

Use parse and asserts from http.servlet

17 files changed, 101 insertions, 165 deletions

diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index f0c7a06718..c11798093d 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -23,7 +23,7 @@ from synapse.api.errors import Codes, SynapseError
 from synapse.crypto.event_signing import check_event_content_hash
 from synapse.events import FrozenEvent
 from synapse.events.utils import prune_event
-from synapse.http.servlet import assert_params_in_request
+from synapse.http.servlet import assert_params_in_dict
 from synapse.util import logcontext, unwrapFirstError
 
 logger = logging.getLogger(__name__)
@@ -199,7 +199,7 @@ def event_from_pdu_json(pdu_json, outlier=False):
     """
     # we could probably enforce a bunch of other fields here (room_id, sender,
     # origin, etc etc)
-    assert_params_in_request(pdu_json, ('event_id', 'type', 'depth'))
+    assert_params_in_dict(pdu_json, ('event_id', 'type', 'depth'))
 
     depth = pdu_json['depth']
     if not isinstance(depth, six.integer_types):
diff --git a/synapse/http/servlet.py b/synapse/http/servlet.py
index cf6723563a..882816dc8f 100644
--- a/synapse/http/servlet.py
+++ b/synapse/http/servlet.py
@@ -206,7 +206,7 @@ def parse_json_object_from_request(request, allow_empty_body=False):
     return content
 
 
-def assert_params_in_request(body, required):
+def assert_params_in_dict(body, required):
     absent = []
     for k in required:
         if k not in body:
diff --git a/synapse/rest/client/v1/admin.py b/synapse/rest/client/v1/admin.py
index 2b091d61a5..01c3f2eb04 100644
--- a/synapse/rest/client/v1/admin.py
+++ b/synapse/rest/client/v1/admin.py
@@ -22,7 +22,12 @@ from twisted.internet import defer
 
 from synapse.api.constants import Membership
 from synapse.api.errors import AuthError, Codes, NotFoundError, SynapseError
-from synapse.http.servlet import parse_json_object_from_request
+from synapse.http.servlet import (
+    assert_params_in_dict,
+    parse_json_object_from_request,
+    parse_integer,
+    parse_string
+)
 from synapse.types import UserID, create_requester
 
 from .base import ClientV1RestServlet, client_path_patterns
@@ -98,16 +103,8 @@ class PurgeMediaCacheRestServlet(ClientV1RestServlet):
         if not is_admin:
             raise AuthError(403, "You are not a server admin")
 
-        before_ts = request.args.get("before_ts", None)
-        if not before_ts:
-            raise SynapseError(400, "Missing 'before_ts' arg")
-
-        logger.info("before_ts: %r", before_ts[0])
-
-        try:
-            before_ts = int(before_ts[0])
-        except Exception:
-            raise SynapseError(400, "Invalid 'before_ts' arg")
+        before_ts = parse_integer(request, "before_ts", required=True)
+        logger.info("before_ts: %r", before_ts)
 
         ret = yield self.media_repository.delete_old_remote_media(before_ts)
 
@@ -300,10 +297,8 @@ class ShutdownRoomRestServlet(ClientV1RestServlet):
             raise AuthError(403, "You are not a server admin")
 
         content = parse_json_object_from_request(request)
-
-        new_room_user_id = content.get("new_room_user_id")
-        if not new_room_user_id:
-            raise SynapseError(400, "Please provide field `new_room_user_id`")
+        assert_params_in_dict(content, ["new_room_user_id"])
+        new_room_user_id = content["new_room_user_id"]
 
         room_creator_requester = create_requester(new_room_user_id)
 
@@ -464,9 +459,8 @@ class ResetPasswordRestServlet(ClientV1RestServlet):
             raise AuthError(403, "You are not a server admin")
 
         params = parse_json_object_from_request(request)
+        assert_params_in_dict(params, ["new_password"])
         new_password = params['new_password']
-        if not new_password:
-            raise SynapseError(400, "Missing 'new_password' arg")
 
         logger.info("new_password: %r", new_password)
 
@@ -514,12 +508,9 @@ class GetUsersPaginatedRestServlet(ClientV1RestServlet):
             raise SynapseError(400, "Can only users a local user")
 
         order = "name"  # order by name in user table
-        start = request.args.get("start")[0]
-        limit = request.args.get("limit")[0]
-        if not limit:
-            raise SynapseError(400, "Missing 'limit' arg")
-        if not start:
-            raise SynapseError(400, "Missing 'start' arg")
+        start = parse_integer(request, "start", required=True)
+        limit = parse_integer(request, "limit", required=True)
+
         logger.info("limit: %s, start: %s", limit, start)
 
         ret = yield self.handlers.admin_handler.get_users_paginate(
@@ -551,12 +542,9 @@ class GetUsersPaginatedRestServlet(ClientV1RestServlet):
 
         order = "name"  # order by name in user table
         params = parse_json_object_from_request(request)
+        assert_params_in_dict(params, ["limit", "start"])
         limit = params['limit']
         start = params['start']
-        if not limit:
-            raise SynapseError(400, "Missing 'limit' arg")
-        if not start:
-            raise SynapseError(400, "Missing 'start' arg")
         logger.info("limit: %s, start: %s", limit, start)
 
         ret = yield self.handlers.admin_handler.get_users_paginate(
@@ -604,10 +592,7 @@ class SearchUsersRestServlet(ClientV1RestServlet):
         if not self.hs.is_mine(target_user):
             raise SynapseError(400, "Can only users a local user")
 
-        term = request.args.get("term")[0]
-        if not term:
-            raise SynapseError(400, "Missing 'term' arg")
-
+        term = parse_string(request, "term", required=True)
         logger.info("term: %s ", term)
 
         ret = yield self.handlers.admin_handler.search_users(
diff --git a/synapse/rest/client/v1/directory.py b/synapse/rest/client/v1/directory.py
index 4fdbb83815..69dcd618cb 100644
--- a/synapse/rest/client/v1/directory.py
+++ b/synapse/rest/client/v1/directory.py
@@ -52,15 +52,14 @@ class ClientDirectoryServer(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, room_alias):
+        room_alias = RoomAlias.from_string(room_alias)
+
         content = parse_json_object_from_request(request)
         if "room_id" not in content:
-            raise SynapseError(400, "Missing room_id key",
+            raise SynapseError(400, 'Missing params: ["room_id"]',
                                errcode=Codes.BAD_JSON)
 
         logger.debug("Got content: %s", content)
-
-        room_alias = RoomAlias.from_string(room_alias)
-
         logger.debug("Got room name: %s", room_alias.to_string())
 
         room_id = content["room_id"]
diff --git a/synapse/rest/client/v1/initial_sync.py b/synapse/rest/client/v1/initial_sync.py
index fbe8cb2023..00a1a99feb 100644
--- a/synapse/rest/client/v1/initial_sync.py
+++ b/synapse/rest/client/v1/initial_sync.py
@@ -16,6 +16,7 @@
 from twisted.internet import defer
 
 from synapse.streams.config import PaginationConfig
+from synapse.http.servlet import parse_boolean
 
 from .base import ClientV1RestServlet, client_path_patterns
 
@@ -33,7 +34,7 @@ class InitialSyncRestServlet(ClientV1RestServlet):
         requester = yield self.auth.get_user_by_req(request)
         as_client_event = "raw" not in request.args
         pagination_config = PaginationConfig.from_request(request)
-        include_archived = request.args.get("archived", None) == ["true"]
+        include_archived = parse_boolean(request, "archived", default=False)
         content = yield self.initial_sync_handler.snapshot_all_rooms(
             user_id=requester.user.to_string(),
             pagin_config=pagination_config,
diff --git a/synapse/rest/client/v1/push_rule.py b/synapse/rest/client/v1/push_rule.py
index 0df7ce570f..7cf6a99774 100644
--- a/synapse/rest/client/v1/push_rule.py
+++ b/synapse/rest/client/v1/push_rule.py
@@ -21,7 +21,7 @@ from synapse.api.errors import (
     SynapseError,
     UnrecognizedRequestError,
 )
-from synapse.http.servlet import parse_json_value_from_request
+from synapse.http.servlet import parse_json_value_from_request, parse_string
 from synapse.push.baserules import BASE_RULE_IDS
 from synapse.push.clientformat import format_push_rules_for_user
 from synapse.push.rulekinds import PRIORITY_CLASS_MAP
@@ -75,11 +75,11 @@ class PushRuleRestServlet(ClientV1RestServlet):
         except InvalidRuleException as e:
             raise SynapseError(400, e.message)
 
-        before = request.args.get("before", None)
+        before = parse_string(request, "before")
         if before:
             before = _namespaced_rule_id(spec, before[0])
 
-        after = request.args.get("after", None)
+        after = parse_string(request, "after")
         if after:
             after = _namespaced_rule_id(spec, after[0])
 
diff --git a/synapse/rest/client/v1/pusher.py b/synapse/rest/client/v1/pusher.py
index 1581f88db5..182a68b1e2 100644
--- a/synapse/rest/client/v1/pusher.py
+++ b/synapse/rest/client/v1/pusher.py
@@ -21,6 +21,7 @@ from synapse.api.errors import Codes, StoreError, SynapseError
 from synapse.http.server import finish_request
 from synapse.http.servlet import (
     RestServlet,
+    assert_params_in_dict,
     parse_json_object_from_request,
     parse_string,
 )
@@ -91,15 +92,11 @@ class PushersSetRestServlet(ClientV1RestServlet):
             )
             defer.returnValue((200, {}))
 
-        reqd = ['kind', 'app_id', 'app_display_name',
-                'device_display_name', 'pushkey', 'lang', 'data']
-        missing = []
-        for i in reqd:
-            if i not in content:
-                missing.append(i)
-        if len(missing):
-            raise SynapseError(400, "Missing parameters: " + ','.join(missing),
-                               errcode=Codes.MISSING_PARAM)
+        assert_params_in_dict(
+            content,
+            ['kind', 'app_id', 'app_display_name',
+             'device_display_name', 'pushkey', 'lang', 'data']
+        )
 
         logger.debug("set pushkey %s to kind %s", content['pushkey'], content['kind'])
         logger.debug("Got pushers request with body: %r", content)
@@ -148,7 +145,7 @@ class PushersRemoveRestServlet(RestServlet):
     SUCCESS_HTML = "<html><body>You have been unsubscribed</body><html>"
 
     def __init__(self, hs):
-        super(RestServlet, self).__init__()
+        super(PushersRemoveRestServlet, self).__init__()
         self.hs = hs
         self.notifier = hs.get_notifier()
         self.auth = hs.get_auth()
diff --git a/synapse/rest/client/v1/register.py b/synapse/rest/client/v1/register.py
index 9203e60615..25a143af8d 100644
--- a/synapse/rest/client/v1/register.py
+++ b/synapse/rest/client/v1/register.py
@@ -18,14 +18,12 @@ import hmac
 import logging
 from hashlib import sha1
 
-from six import string_types
-
 from twisted.internet import defer
 
 import synapse.util.stringutils as stringutils
 from synapse.api.constants import LoginType
 from synapse.api.errors import Codes, SynapseError
-from synapse.http.servlet import parse_json_object_from_request
+from synapse.http.servlet import assert_params_in_dict, parse_json_object_from_request
 from synapse.types import create_requester
 
 from .base import ClientV1RestServlet, client_path_patterns
@@ -124,8 +122,7 @@ class RegisterRestServlet(ClientV1RestServlet):
         session = (register_json["session"]
                    if "session" in register_json else None)
         login_type = None
-        if "type" not in register_json:
-            raise SynapseError(400, "Missing 'type' key.")
+        assert_params_in_dict(register_json, ["type"])
 
         try:
             login_type = register_json["type"]
@@ -312,9 +309,7 @@ class RegisterRestServlet(ClientV1RestServlet):
     def _do_app_service(self, request, register_json, session):
         as_token = self.auth.get_access_token_from_request(request)
 
-        if "user" not in register_json:
-            raise SynapseError(400, "Expected 'user' key.")
-
+        assert_params_in_dict(register_json, ["user"])
         user_localpart = register_json["user"].encode("utf-8")
 
         handler = self.handlers.registration_handler
@@ -331,12 +326,7 @@ class RegisterRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def _do_shared_secret(self, request, register_json, session):
-        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.")
+        assert_params_in_dict(register_json, ["mac", "user", "password"])
 
         if not self.hs.config.registration_shared_secret:
             raise SynapseError(400, "Shared secret registration is not enabled")
@@ -419,11 +409,7 @@ class CreateUserRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def _do_create(self, requester, user_json):
-        if "localpart" not in user_json:
-            raise SynapseError(400, "Expected 'localpart' key.")
-
-        if "displayname" not in user_json:
-            raise SynapseError(400, "Expected 'displayname' key.")
+        assert_params_in_dict(user_json, ["localpart", "displayname"])
 
         localpart = user_json["localpart"].encode("utf-8")
         displayname = user_json["displayname"].encode("utf-8")
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 2470db52ba..3d62447854 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -28,6 +28,7 @@ from synapse.api.errors import AuthError, Codes, SynapseError
 from synapse.api.filtering import Filter
 from synapse.events.utils import format_event_for_client_v2, serialize_event
 from synapse.http.servlet import (
+    assert_params_in_dict,
     parse_integer,
     parse_json_object_from_request,
     parse_string,
@@ -435,9 +436,9 @@ class RoomMessageListRestServlet(ClientV1RestServlet):
             request, default_limit=10,
         )
         as_client_event = "raw" not in request.args
-        filter_bytes = request.args.get("filter", None)
+        filter_bytes = parse_string(request, "filter")
         if filter_bytes:
-            filter_json = urlparse.unquote(filter_bytes[-1]).decode("UTF-8")
+            filter_json = urlparse.unquote(filter_bytes).decode("UTF-8")
             event_filter = Filter(json.loads(filter_json))
         else:
             event_filter = None
@@ -530,7 +531,7 @@ class RoomEventContextServlet(ClientV1RestServlet):
     def on_GET(self, request, room_id, event_id):
         requester = yield self.auth.get_user_by_req(request, allow_guest=True)
 
-        limit = int(request.args.get("limit", [10])[0])
+        limit = parse_integer(request, "limit", default=10)
 
         results = yield self.handlers.room_context_handler.get_event_context(
             requester.user,
@@ -636,8 +637,7 @@ class RoomMembershipRestServlet(ClientV1RestServlet):
 
         target = requester.user
         if membership_action in ["invite", "ban", "unban", "kick"]:
-            if "user_id" not in content:
-                raise SynapseError(400, "Missing user_id key.")
+            assert_params_in_dict(content, ["user_id"])
             target = UserID.from_string(content["user_id"])
 
         event_content = None
@@ -764,7 +764,7 @@ class SearchRestServlet(ClientV1RestServlet):
 
         content = parse_json_object_from_request(request)
 
-        batch = request.args.get("next_batch", [None])[0]
+        batch = parse_string(request, "next_batch")
         results = yield self.handlers.search_handler.search(
             requester.user,
             content,
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index 1263abb02c..eeae466d82 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -24,7 +24,7 @@ from synapse.api.constants import LoginType
 from synapse.api.errors import Codes, SynapseError
 from synapse.http.servlet import (
     RestServlet,
-    assert_params_in_request,
+    assert_params_in_dict,
     parse_json_object_from_request,
 )
 from synapse.util.msisdn import phone_number_to_msisdn
@@ -47,7 +47,7 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
 
-        assert_params_in_request(body, [
+        assert_params_in_dict(body, [
             'id_server', 'client_secret', 'email', 'send_attempt'
         ])
 
@@ -80,7 +80,7 @@ class MsisdnPasswordRequestTokenRestServlet(RestServlet):
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
 
-        assert_params_in_request(body, [
+        assert_params_in_dict(body, [
             'id_server', 'client_secret',
             'country', 'phone_number', 'send_attempt',
         ])
@@ -159,11 +159,10 @@ class PasswordRestServlet(RestServlet):
                     raise SynapseError(404, "Email address not found", Codes.NOT_FOUND)
                 user_id = threepid_user_id
             else:
-                logger.error("Auth succeeded but no known type!", result.keys())
+                logger.error("Auth succeeded but no known type! %r", result.keys())
                 raise SynapseError(500, "", Codes.UNKNOWN)
 
-        if 'new_password' not in params:
-            raise SynapseError(400, "", Codes.MISSING_PARAM)
+        assert_params_in_dict(params, ["new_password"])
         new_password = params['new_password']
 
         yield self._set_password_handler.set_password(
@@ -228,15 +227,10 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
     @defer.inlineCallbacks
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
-
-        required = ['id_server', 'client_secret', 'email', 'send_attempt']
-        absent = []
-        for k in required:
-            if k not in body:
-                absent.append(k)
-
-        if absent:
-            raise SynapseError(400, "Missing params: %r" % absent, Codes.MISSING_PARAM)
+        assert_params_in_dict(
+            body,
+            ['id_server', 'client_secret', 'email', 'send_attempt'],
+        )
 
         if not check_3pid_allowed(self.hs, "email", body['email']):
             raise SynapseError(
@@ -266,18 +260,10 @@ class MsisdnThreepidRequestTokenRestServlet(RestServlet):
     @defer.inlineCallbacks
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
-
-        required = [
+        assert_params_in_dict(body, [
             'id_server', 'client_secret',
             'country', 'phone_number', 'send_attempt',
-        ]
-        absent = []
-        for k in required:
-            if k not in body:
-                absent.append(k)
-
-        if absent:
-            raise SynapseError(400, "Missing params: %r" % absent, Codes.MISSING_PARAM)
+        ])
 
         msisdn = phone_number_to_msisdn(body['country'], body['phone_number'])
 
@@ -372,15 +358,7 @@ class ThreepidDeleteRestServlet(RestServlet):
     @defer.inlineCallbacks
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
-
-        required = ['medium', 'address']
-        absent = []
-        for k in required:
-            if k not in body:
-                absent.append(k)
-
-        if absent:
-            raise SynapseError(400, "Missing params: %r" % absent, Codes.MISSING_PARAM)
+        assert_params_in_dict(body, ['medium', 'address'])
 
         requester = yield self.auth.get_user_by_req(request)
         user_id = requester.user.to_string()
diff --git a/synapse/rest/client/v2_alpha/devices.py b/synapse/rest/client/v2_alpha/devices.py
index 09f6a8efe3..aded2409be 100644
--- a/synapse/rest/client/v2_alpha/devices.py
+++ b/synapse/rest/client/v2_alpha/devices.py
@@ -18,14 +18,18 @@ import logging
 from twisted.internet import defer
 
 from synapse.api import errors
-from synapse.http import servlet
+from synapse.http.servlet import (
+    assert_params_in_dict,
+    parse_json_object_from_request,
+    RestServlet
+)
 
 from ._base import client_v2_patterns, interactive_auth_handler
 
 logger = logging.getLogger(__name__)
 
 
-class DevicesRestServlet(servlet.RestServlet):
+class DevicesRestServlet(RestServlet):
     PATTERNS = client_v2_patterns("/devices$", v2_alpha=False)
 
     def __init__(self, hs):
@@ -47,7 +51,7 @@ class DevicesRestServlet(servlet.RestServlet):
         defer.returnValue((200, {"devices": devices}))
 
 
-class DeleteDevicesRestServlet(servlet.RestServlet):
+class DeleteDevicesRestServlet(RestServlet):
     """
     API for bulk deletion of devices. Accepts a JSON object with a devices
     key which lists the device_ids to delete. Requires user interactive auth.
@@ -67,19 +71,17 @@ class DeleteDevicesRestServlet(servlet.RestServlet):
         requester = yield self.auth.get_user_by_req(request)
 
         try:
-            body = servlet.parse_json_object_from_request(request)
+            body = parse_json_object_from_request(request)
         except errors.SynapseError as e:
             if e.errcode == errors.Codes.NOT_JSON:
-                # deal with older clients which didn't pass a J*DELETESON dict
+                # DELETE
+                # deal with older clients which didn't pass a JSON dict
                 # the same as those that pass an empty dict
                 body = {}
             else:
                 raise e
 
-        if 'devices' not in body:
-            raise errors.SynapseError(
-                400, "No devices supplied", errcode=errors.Codes.MISSING_PARAM
-            )
+        assert_params_in_dict(body, ["devices"])
 
         yield self.auth_handler.validate_user_via_ui_auth(
             requester, body, self.hs.get_ip_from_request(request),
@@ -92,7 +94,7 @@ class DeleteDevicesRestServlet(servlet.RestServlet):
         defer.returnValue((200, {}))
 
 
-class DeviceRestServlet(servlet.RestServlet):
+class DeviceRestServlet(RestServlet):
     PATTERNS = client_v2_patterns("/devices/(?P<device_id>[^/]*)$", v2_alpha=False)
 
     def __init__(self, hs):
@@ -121,7 +123,7 @@ class DeviceRestServlet(servlet.RestServlet):
         requester = yield self.auth.get_user_by_req(request)
 
         try:
-            body = servlet.parse_json_object_from_request(request)
+            body = parse_json_object_from_request(request)
 
         except errors.SynapseError as e:
             if e.errcode == errors.Codes.NOT_JSON:
@@ -144,7 +146,7 @@ class DeviceRestServlet(servlet.RestServlet):
     def on_PUT(self, request, device_id):
         requester = yield self.auth.get_user_by_req(request, allow_guest=True)
 
-        body = servlet.parse_json_object_from_request(request)
+        body = parse_json_object_from_request(request)
         yield self.device_handler.update_device(
             requester.user.to_string(),
             device_id,
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index d305afcaef..1918897f68 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -28,7 +28,7 @@ from synapse.api.constants import LoginType
 from synapse.api.errors import Codes, SynapseError, UnrecognizedRequestError
 from synapse.http.servlet import (
     RestServlet,
-    assert_params_in_request,
+    assert_params_in_dict,
     parse_json_object_from_request,
     parse_string,
 )
@@ -68,7 +68,7 @@ class EmailRegisterRequestTokenRestServlet(RestServlet):
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
 
-        assert_params_in_request(body, [
+        assert_params_in_dict(body, [
             'id_server', 'client_secret', 'email', 'send_attempt'
         ])
 
@@ -104,7 +104,7 @@ class MsisdnRegisterRequestTokenRestServlet(RestServlet):
     def on_POST(self, request):
         body = parse_json_object_from_request(request)
 
-        assert_params_in_request(body, [
+        assert_params_in_dict(body, [
             'id_server', 'client_secret',
             'country', 'phone_number',
             'send_attempt',
@@ -386,9 +386,7 @@ class RegisterRestServlet(RestServlet):
             add_msisdn = False
         else:
             # NB: This may be from the auth handler and NOT from the POST
-            if 'password' not in params:
-                raise SynapseError(400, "Missing password.",
-                                   Codes.MISSING_PARAM)
+            assert_params_in_dict(params, ["password"])
 
             desired_username = params.get("username", None)
             new_password = params.get("password", None)
@@ -565,11 +563,14 @@ class RegisterRestServlet(RestServlet):
         Returns:
             defer.Deferred:
         """
-        reqd = ('medium', 'address', 'validated_at')
-        if any(x not in threepid for x in reqd):
-            # This will only happen if the ID server returns a malformed response
-            logger.info("Can't add incomplete 3pid")
-            defer.returnValue()
+        try:
+            assert_params_in_dict(threepid, ['medium', 'address', 'validated_at'])
+        except SynapseError as ex:
+            if ex.errcode == Codes.MISSING_PARAM:
+                # This will only happen if the ID server returns a malformed response
+                logger.info("Can't add incomplete 3pid")
+                defer.returnValue(None)
+            raise
 
         yield self.auth_handler.add_threepid(
             user_id,
diff --git a/synapse/rest/client/v2_alpha/report_event.py b/synapse/rest/client/v2_alpha/report_event.py
index 0cc2a71c3b..95d2a71ec2 100644
--- a/synapse/rest/client/v2_alpha/report_event.py
+++ b/synapse/rest/client/v2_alpha/report_event.py
@@ -23,7 +23,7 @@ from twisted.internet import defer
 from synapse.api.errors import Codes, SynapseError
 from synapse.http.servlet import (
     RestServlet,
-    assert_params_in_request,
+    assert_params_in_dict,
     parse_json_object_from_request,
 )
 
@@ -50,7 +50,7 @@ class ReportEventRestServlet(RestServlet):
         user_id = requester.user.to_string()
 
         body = parse_json_object_from_request(request)
-        assert_params_in_request(body, ("reason", "score"))
+        assert_params_in_dict(body, ("reason", "score"))
 
         if not isinstance(body["reason"], string_types):
             raise SynapseError(
diff --git a/synapse/rest/media/v1/identicon_resource.py b/synapse/rest/media/v1/identicon_resource.py
index a2e391415f..b3217eff53 100644
--- a/synapse/rest/media/v1/identicon_resource.py
+++ b/synapse/rest/media/v1/identicon_resource.py
@@ -14,6 +14,8 @@
 
 from pydenticon import Generator
 
+from synapse.http.servlet import parse_integer
+
 from twisted.web.resource import Resource
 
 FOREGROUND = [
@@ -56,8 +58,8 @@ class IdenticonResource(Resource):
 
     def render_GET(self, request):
         name = "/".join(request.postpath)
-        width = int(request.args.get("width", [96])[0])
-        height = int(request.args.get("height", [96])[0])
+        width = parse_integer(request, "width", default=96)
+        height = parse_integer(request, "height", default=96)
         identicon_bytes = self.generate_identicon(name, width, height)
         request.setHeader(b"Content-Type", b"image/png")
         request.setHeader(
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 4e3a18ce08..b70b15c4c2 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -40,6 +40,7 @@ from synapse.http.server import (
     respond_with_json_bytes,
     wrap_json_request_handler,
 )
+from synapse.http.servlet import parse_integer, parse_string
 from synapse.util.async import ObservableDeferred
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.logcontext import make_deferred_yieldable, run_in_background
@@ -96,9 +97,9 @@ class PreviewUrlResource(Resource):
 
         # XXX: if get_user_by_req fails, what should we do in an async render?
         requester = yield self.auth.get_user_by_req(request)
-        url = request.args.get("url")[0]
+        url = parse_string(request, "url")
         if "ts" in request.args:
-            ts = int(request.args.get("ts")[0])
+            ts = parse_integer(request, "ts")
         else:
             ts = self.clock.time_msec()
 
diff --git a/synapse/rest/media/v1/upload_resource.py b/synapse/rest/media/v1/upload_resource.py
index 1a98120e1d..9b22d204a6 100644
--- a/synapse/rest/media/v1/upload_resource.py
+++ b/synapse/rest/media/v1/upload_resource.py
@@ -21,6 +21,7 @@ from twisted.web.server import NOT_DONE_YET
 
 from synapse.api.errors import SynapseError
 from synapse.http.server import respond_with_json, wrap_json_request_handler
+from synapse.http.servlet import parse_string
 
 logger = logging.getLogger(__name__)
 
@@ -65,10 +66,10 @@ class UploadResource(Resource):
                 code=413,
             )
 
-        upload_name = request.args.get("filename", None)
+        upload_name = parse_string(request, "filename")
         if upload_name:
             try:
-                upload_name = upload_name[0].decode('UTF-8')
+                upload_name = upload_name.decode('UTF-8')
             except UnicodeDecodeError:
                 raise SynapseError(
                     msg="Invalid UTF-8 filename parameter: %r" % (upload_name),
diff --git a/synapse/streams/config.py b/synapse/streams/config.py
index 46ccbbda7d..22b0b830f7 100644
--- a/synapse/streams/config.py
+++ b/synapse/streams/config.py
@@ -16,6 +16,7 @@
 import logging
 
 from synapse.api.errors import SynapseError
+from synapse.http.servlet import parse_integer, parse_string
 from synapse.types import StreamToken
 
 logger = logging.getLogger(__name__)
@@ -56,23 +57,10 @@ class PaginationConfig(object):
     @classmethod
     def from_request(cls, request, raise_invalid_params=True,
                      default_limit=None):
-        def get_param(name, default=None):
-            lst = request.args.get(name, [])
-            if len(lst) > 1:
-                raise SynapseError(
-                    400, "%s must be specified only once" % (name,)
-                )
-            elif len(lst) == 1:
-                return lst[0]
-            else:
-                return default
-
-        direction = get_param("dir", 'f')
-        if direction not in ['f', 'b']:
-            raise SynapseError(400, "'dir' parameter is invalid.")
-
-        from_tok = get_param("from")
-        to_tok = get_param("to")
+        direction = parse_string(request, "dir", default='f', allowed_values=['f', 'b'])
+
+        from_tok = parse_string(request, "from")
+        to_tok = parse_string(request, "to")
 
         try:
             if from_tok == "END":
@@ -88,12 +76,7 @@ class PaginationConfig(object):
         except Exception:
             raise SynapseError(400, "'to' paramater is invalid")
 
-        limit = get_param("limit", None)
-        if limit is not None and not limit.isdigit():
-            raise SynapseError(400, "'limit' parameter must be an integer.")
-
-        if limit is None:
-            limit = default_limit
+        limit = parse_integer(request, "limit", default=default_limit)
 
         try:
             return PaginationConfig(from_tok, to_tok, direction, limit)