Add device management to admin API (#7481)

- Admin is able to
  - change displaynames
  - delete devices
  - list devices
  - get device informations

Fixes #7330

5 files changed, 920 insertions, 0 deletions

diff --git a/changelog.d/7481.feature b/changelog.d/7481.feature
new file mode 100644
index 0000000000..f167f3632c
--- /dev/null
+++ b/changelog.d/7481.feature
@@ -0,0 +1 @@
+Add admin APIs to allow server admins to manage users' devices. Contributed by @dklimpel.
diff --git a/docs/admin_api/user_admin_api.rst b/docs/admin_api/user_admin_api.rst
index 776e71ec04..a3d52b282b 100644
--- a/docs/admin_api/user_admin_api.rst
+++ b/docs/admin_api/user_admin_api.rst
@@ -1,3 +1,5 @@
+.. contents::
+
 Create or modify Account
 ========================
 
@@ -245,3 +247,210 @@ with a body of:
     }
 
 including an ``access_token`` of a server admin.
+
+
+User devices
+============
+
+List all devices
+----------------
+Gets information about all devices for a specific ``user_id``.
+
+**Usage**
+
+A standard request to query the devices of an user:
+
+::
+
+    GET /_synapse/admin/v2/users/<user_id>/devices
+
+    {}
+
+Response:
+
+.. code:: json
+
+    {
+      "devices": [
+        {
+          "device_id": "QBUAZIFURK",
+          "display_name": "android",
+          "last_seen_ip": "1.2.3.4",
+          "last_seen_ts": 1474491775024,
+          "user_id": "<user_id>"
+        },
+        {
+          "device_id": "AUIECTSRND",
+          "display_name": "ios",
+          "last_seen_ip": "1.2.3.5",
+          "last_seen_ts": 1474491775025,
+          "user_id": "<user_id>"
+        }
+      ]
+    }
+
+**Parameters**
+
+The following query parameters are available:
+
+- ``user_id`` - fully qualified: for example, ``@user:server.com``.
+
+The following fields are possible in the JSON response body:
+
+- ``devices`` - An array of objects, each containing information about a device.
+  Device objects contain the following fields:
+
+  - ``device_id`` - Identifier of device.
+  - ``display_name`` - Display name set by the user for this device.
+    Absent if no name has been set.
+  - ``last_seen_ip`` - The IP address where this device was last seen.
+    (May be a few minutes out of date, for efficiency reasons).
+  - ``last_seen_ts`` - The timestamp (in milliseconds since the unix epoch) when this
+    devices was last seen. (May be a few minutes out of date, for efficiency reasons).
+  - ``user_id`` - Owner of  device.
+
+Delete multiple devices
+------------------
+Deletes the given devices for a specific ``user_id``, and invalidates
+any access token associated with them.
+
+**Usage**
+
+A standard request to delete devices:
+
+::
+
+    POST /_synapse/admin/v2/users/<user_id>/delete_devices
+
+    {
+      "devices": [
+        "QBUAZIFURK",
+        "AUIECTSRND"
+      ],
+    }
+
+
+Response:
+
+.. code:: json
+
+    {}
+
+**Parameters**
+
+The following query parameters are available:
+
+- ``user_id`` - fully qualified: for example, ``@user:server.com``.
+
+The following fields are required in the JSON request body:
+
+- ``devices`` - The list of device IDs to delete.
+
+Show a device
+---------------
+Gets information on a single device, by ``device_id`` for a specific ``user_id``.
+
+**Usage**
+
+A standard request to get a device:
+
+::
+
+    GET /_synapse/admin/v2/users/<user_id>/devices/<device_id>
+
+    {}
+
+
+Response:
+
+.. code:: json
+
+    {
+      "device_id": "<device_id>",
+      "display_name": "android",
+      "last_seen_ip": "1.2.3.4",
+      "last_seen_ts": 1474491775024,
+      "user_id": "<user_id>"
+    }
+
+**Parameters**
+
+The following query parameters are available:
+
+- ``user_id`` - fully qualified: for example, ``@user:server.com``.
+- ``device_id`` - The device to retrieve.
+
+The following fields are possible in the JSON response body:
+
+- ``device_id`` - Identifier of device.
+- ``display_name`` - Display name set by the user for this device.
+  Absent if no name has been set.
+- ``last_seen_ip`` - The IP address where this device was last seen.
+  (May be a few minutes out of date, for efficiency reasons).
+- ``last_seen_ts`` - The timestamp (in milliseconds since the unix epoch) when this
+  devices was last seen. (May be a few minutes out of date, for efficiency reasons).
+- ``user_id`` - Owner of  device.
+
+Update a device
+---------------
+Updates the metadata on the given ``device_id`` for a specific ``user_id``.
+
+**Usage**
+
+A standard request to update a device:
+
+::
+
+    PUT /_synapse/admin/v2/users/<user_id>/devices/<device_id>
+
+    {
+      "display_name": "My other phone"
+    }
+
+
+Response:
+
+.. code:: json
+
+    {}
+
+**Parameters**
+
+The following query parameters are available:
+
+- ``user_id`` - fully qualified: for example, ``@user:server.com``.
+- ``device_id`` - The device to update.
+
+The following fields are required in the JSON request body:
+
+- ``display_name`` - The new display name for this device. If not given,
+  the display name is unchanged.
+
+Delete a device
+---------------
+Deletes the given ``device_id`` for a specific ``user_id``,
+and invalidates any access token associated with it.
+
+**Usage**
+
+A standard request for delete a device:
+
+::
+
+    DELETE /_synapse/admin/v2/users/<user_id>/devices/<device_id>
+
+    {}
+
+
+Response:
+
+.. code:: json
+
+    {}
+
+**Parameters**
+
+The following query parameters are available:
+
+- ``user_id`` - fully qualified: for example, ``@user:server.com``.
+- ``device_id`` - The device to delete.
diff --git a/synapse/rest/admin/__init__.py b/synapse/rest/admin/__init__.py
index 6b85148a32..9eda592de9 100644
--- a/synapse/rest/admin/__init__.py
+++ b/synapse/rest/admin/__init__.py
@@ -26,6 +26,11 @@ from synapse.rest.admin._base import (
     assert_requester_is_admin,
     historical_admin_path_patterns,
 )
+from synapse.rest.admin.devices import (
+    DeleteDevicesRestServlet,
+    DeviceRestServlet,
+    DevicesRestServlet,
+)
 from synapse.rest.admin.groups import DeleteGroupAdminRestServlet
 from synapse.rest.admin.media import ListMediaInRoom, register_servlets_for_media_repo
 from synapse.rest.admin.purge_room_servlet import PurgeRoomServlet
@@ -202,6 +207,9 @@ def register_servlets(hs, http_server):
     UserAdminServlet(hs).register(http_server)
     UserRestServletV2(hs).register(http_server)
     UsersRestServletV2(hs).register(http_server)
+    DeviceRestServlet(hs).register(http_server)
+    DevicesRestServlet(hs).register(http_server)
+    DeleteDevicesRestServlet(hs).register(http_server)
 
 
 def register_servlets_for_client_rest_resource(hs, http_server):
diff --git a/synapse/rest/admin/devices.py b/synapse/rest/admin/devices.py
new file mode 100644
index 0000000000..8d32677339
--- /dev/null
+++ b/synapse/rest/admin/devices.py
@@ -0,0 +1,161 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 Dirk Klimpel
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+import re
+
+from synapse.api.errors import NotFoundError, SynapseError
+from synapse.http.servlet import (
+    RestServlet,
+    assert_params_in_dict,
+    parse_json_object_from_request,
+)
+from synapse.rest.admin._base import assert_requester_is_admin
+from synapse.types import UserID
+
+logger = logging.getLogger(__name__)
+
+
+class DeviceRestServlet(RestServlet):
+    """
+    Get, update or delete the given user's device
+    """
+
+    PATTERNS = (
+        re.compile(
+            "^/_synapse/admin/v2/users/(?P<user_id>[^/]*)/devices/(?P<device_id>[^/]*)$"
+        ),
+    )
+
+    def __init__(self, hs):
+        super(DeviceRestServlet, self).__init__()
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.device_handler = hs.get_device_handler()
+        self.store = hs.get_datastore()
+
+    async def on_GET(self, request, user_id, device_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "Can only lookup local users")
+
+        u = await self.store.get_user_by_id(target_user.to_string())
+        if u is None:
+            raise NotFoundError("Unknown user")
+
+        device = await self.device_handler.get_device(
+            target_user.to_string(), device_id
+        )
+        return 200, device
+
+    async def on_DELETE(self, request, user_id, device_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "Can only lookup local users")
+
+        u = await self.store.get_user_by_id(target_user.to_string())
+        if u is None:
+            raise NotFoundError("Unknown user")
+
+        await self.device_handler.delete_device(target_user.to_string(), device_id)
+        return 200, {}
+
+    async def on_PUT(self, request, user_id, device_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "Can only lookup local users")
+
+        u = await self.store.get_user_by_id(target_user.to_string())
+        if u is None:
+            raise NotFoundError("Unknown user")
+
+        body = parse_json_object_from_request(request, allow_empty_body=True)
+        await self.device_handler.update_device(
+            target_user.to_string(), device_id, body
+        )
+        return 200, {}
+
+
+class DevicesRestServlet(RestServlet):
+    """
+    Retrieve the given user's devices
+    """
+
+    PATTERNS = (re.compile("^/_synapse/admin/v2/users/(?P<user_id>[^/]*)/devices$"),)
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.device_handler = hs.get_device_handler()
+        self.store = hs.get_datastore()
+
+    async def on_GET(self, request, user_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "Can only lookup local users")
+
+        u = await self.store.get_user_by_id(target_user.to_string())
+        if u is None:
+            raise NotFoundError("Unknown user")
+
+        devices = await self.device_handler.get_devices_by_user(target_user.to_string())
+        return 200, {"devices": devices}
+
+
+class DeleteDevicesRestServlet(RestServlet):
+    """
+    API for bulk deletion of devices. Accepts a JSON object with a devices
+    key which lists the device_ids to delete.
+    """
+
+    PATTERNS = (
+        re.compile("^/_synapse/admin/v2/users/(?P<user_id>[^/]*)/delete_devices$"),
+    )
+
+    def __init__(self, hs):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.device_handler = hs.get_device_handler()
+        self.store = hs.get_datastore()
+
+    async def on_POST(self, request, user_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "Can only lookup local users")
+
+        u = await self.store.get_user_by_id(target_user.to_string())
+        if u is None:
+            raise NotFoundError("Unknown user")
+
+        body = parse_json_object_from_request(request, allow_empty_body=False)
+        assert_params_in_dict(body, ["devices"])
+
+        await self.device_handler.delete_devices(
+            target_user.to_string(), body["devices"]
+        )
+        return 200, {}
diff --git a/tests/rest/admin/test_device.py b/tests/rest/admin/test_device.py
new file mode 100644
index 0000000000..faa7f381a9
--- /dev/null
+++ b/tests/rest/admin/test_device.py
@@ -0,0 +1,541 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 Dirk Klimpel
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+import urllib.parse
+
+import synapse.rest.admin
+from synapse.api.errors import Codes
+from synapse.rest.client.v1 import login
+
+from tests import unittest
+
+
+class DeviceRestTestCase(unittest.HomeserverTestCase):
+
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.handler = hs.get_device_handler()
+
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+        self.other_user_token = self.login("user", "pass")
+        res = self.get_success(self.handler.get_devices_by_user(self.other_user))
+        self.other_user_device_id = res[0]["device_id"]
+
+        self.url = "/_synapse/admin/v2/users/%s/devices/%s" % (
+            urllib.parse.quote(self.other_user),
+            self.other_user_device_id,
+        )
+
+    def test_no_auth(self):
+        """
+        Try to get a device of an user without authentication.
+        """
+        request, channel = self.make_request("GET", self.url, b"{}")
+        self.render(request)
+
+        self.assertEqual(401, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+        request, channel = self.make_request("PUT", self.url, b"{}")
+        self.render(request)
+
+        self.assertEqual(401, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+        request, channel = self.make_request("DELETE", self.url, b"{}")
+        self.render(request)
+
+        self.assertEqual(401, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+    def test_requester_is_no_admin(self):
+        """
+        If the user is not a server admin, an error is returned.
+        """
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.other_user_token,
+        )
+        self.render(request)
+
+        self.assertEqual(403, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+        request, channel = self.make_request(
+            "PUT", self.url, access_token=self.other_user_token,
+        )
+        self.render(request)
+
+        self.assertEqual(403, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+        request, channel = self.make_request(
+            "DELETE", self.url, access_token=self.other_user_token,
+        )
+        self.render(request)
+
+        self.assertEqual(403, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+    def test_user_does_not_exist(self):
+        """
+        Tests that a lookup for a user that does not exist returns a 404
+        """
+        url = (
+            "/_synapse/admin/v2/users/@unknown_person:test/devices/%s"
+            % self.other_user_device_id
+        )
+
+        request, channel = self.make_request(
+            "GET", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+        request, channel = self.make_request(
+            "PUT", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+        request, channel = self.make_request(
+            "DELETE", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+    def test_user_is_not_local(self):
+        """
+        Tests that a lookup for a user that is not a local returns a 400
+        """
+        url = (
+            "/_synapse/admin/v2/users/@unknown_person:unknown_domain/devices/%s"
+            % self.other_user_device_id
+        )
+
+        request, channel = self.make_request(
+            "GET", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual("Can only lookup local users", channel.json_body["error"])
+
+        request, channel = self.make_request(
+            "PUT", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual("Can only lookup local users", channel.json_body["error"])
+
+        request, channel = self.make_request(
+            "DELETE", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual("Can only lookup local users", channel.json_body["error"])
+
+    def test_unknown_device(self):
+        """
+        Tests that a lookup for a device that does not exist returns either 404 or 200.
+        """
+        url = "/_synapse/admin/v2/users/%s/devices/unknown_device" % urllib.parse.quote(
+            self.other_user
+        )
+
+        request, channel = self.make_request(
+            "GET", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+        request, channel = self.make_request(
+            "PUT", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+        request, channel = self.make_request(
+            "DELETE", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        # Delete unknown device returns status 200
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+    def test_update_device_too_long_display_name(self):
+        """
+        Update a device with a display name that is invalid (too long).
+        """
+        # Set iniital display name.
+        update = {"display_name": "new display"}
+        self.get_success(
+            self.handler.update_device(
+                self.other_user, self.other_user_device_id, update
+            )
+        )
+
+        # Request to update a device display name with a new value that is longer than allowed.
+        update = {
+            "display_name": "a"
+            * (synapse.handlers.device.MAX_DEVICE_DISPLAY_NAME_LEN + 1)
+        }
+
+        body = json.dumps(update)
+        request, channel = self.make_request(
+            "PUT",
+            self.url,
+            access_token=self.admin_user_tok,
+            content=body.encode(encoding="utf_8"),
+        )
+        self.render(request)
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.UNKNOWN, channel.json_body["errcode"])
+
+        # Ensure the display name was not updated.
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual("new display", channel.json_body["display_name"])
+
+    def test_update_no_display_name(self):
+        """
+        Tests that a update for a device without JSON returns a 200
+        """
+        # Set iniital display name.
+        update = {"display_name": "new display"}
+        self.get_success(
+            self.handler.update_device(
+                self.other_user, self.other_user_device_id, update
+            )
+        )
+
+        request, channel = self.make_request(
+            "PUT", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+        # Ensure the display name was not updated.
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual("new display", channel.json_body["display_name"])
+
+    def test_update_display_name(self):
+        """
+        Tests a normal successful update of display name
+        """
+        # Set new display_name
+        body = json.dumps({"display_name": "new displayname"})
+        request, channel = self.make_request(
+            "PUT",
+            self.url,
+            access_token=self.admin_user_tok,
+            content=body.encode(encoding="utf_8"),
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+        # Check new display_name
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual("new displayname", channel.json_body["display_name"])
+
+    def test_get_device(self):
+        """
+        Tests that a normal lookup for a device is successfully
+        """
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(self.other_user, channel.json_body["user_id"])
+        # Check that all fields are available
+        self.assertIn("user_id", channel.json_body)
+        self.assertIn("device_id", channel.json_body)
+        self.assertIn("display_name", channel.json_body)
+        self.assertIn("last_seen_ip", channel.json_body)
+        self.assertIn("last_seen_ts", channel.json_body)
+
+    def test_delete_device(self):
+        """
+        Tests that a remove of a device is successfully
+        """
+        # Count number of devies of an user.
+        res = self.get_success(self.handler.get_devices_by_user(self.other_user))
+        number_devices = len(res)
+        self.assertEqual(1, number_devices)
+
+        # Delete device
+        request, channel = self.make_request(
+            "DELETE", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+        # Ensure that the number of devices is decreased
+        res = self.get_success(self.handler.get_devices_by_user(self.other_user))
+        self.assertEqual(number_devices - 1, len(res))
+
+
+class DevicesRestTestCase(unittest.HomeserverTestCase):
+
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+
+        self.url = "/_synapse/admin/v2/users/%s/devices" % urllib.parse.quote(
+            self.other_user
+        )
+
+    def test_no_auth(self):
+        """
+        Try to list devices of an user without authentication.
+        """
+        request, channel = self.make_request("GET", self.url, b"{}")
+        self.render(request)
+
+        self.assertEqual(401, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+    def test_requester_is_no_admin(self):
+        """
+        If the user is not a server admin, an error is returned.
+        """
+        other_user_token = self.login("user", "pass")
+
+        request, channel = self.make_request(
+            "GET", self.url, access_token=other_user_token,
+        )
+        self.render(request)
+
+        self.assertEqual(403, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+    def test_user_does_not_exist(self):
+        """
+        Tests that a lookup for a user that does not exist returns a 404
+        """
+        url = "/_synapse/admin/v2/users/@unknown_person:test/devices"
+        request, channel = self.make_request(
+            "GET", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+    def test_user_is_not_local(self):
+        """
+        Tests that a lookup for a user that is not a local returns a 400
+        """
+        url = "/_synapse/admin/v2/users/@unknown_person:unknown_domain/devices"
+
+        request, channel = self.make_request(
+            "GET", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual("Can only lookup local users", channel.json_body["error"])
+
+    def test_get_devices(self):
+        """
+        Tests that a normal lookup for devices is successfully
+        """
+        # Create devices
+        number_devices = 5
+        for n in range(number_devices):
+            self.login("user", "pass")
+
+        # Get devices
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(number_devices, len(channel.json_body["devices"]))
+        self.assertEqual(self.other_user, channel.json_body["devices"][0]["user_id"])
+        # Check that all fields are available
+        for d in channel.json_body["devices"]:
+            self.assertIn("user_id", d)
+            self.assertIn("device_id", d)
+            self.assertIn("display_name", d)
+            self.assertIn("last_seen_ip", d)
+            self.assertIn("last_seen_ts", d)
+
+
+class DeleteDevicesRestTestCase(unittest.HomeserverTestCase):
+
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.handler = hs.get_device_handler()
+
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+
+        self.url = "/_synapse/admin/v2/users/%s/delete_devices" % urllib.parse.quote(
+            self.other_user
+        )
+
+    def test_no_auth(self):
+        """
+        Try to delete devices of an user without authentication.
+        """
+        request, channel = self.make_request("POST", self.url, b"{}")
+        self.render(request)
+
+        self.assertEqual(401, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+    def test_requester_is_no_admin(self):
+        """
+        If the user is not a server admin, an error is returned.
+        """
+        other_user_token = self.login("user", "pass")
+
+        request, channel = self.make_request(
+            "POST", self.url, access_token=other_user_token,
+        )
+        self.render(request)
+
+        self.assertEqual(403, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+    def test_user_does_not_exist(self):
+        """
+        Tests that a lookup for a user that does not exist returns a 404
+        """
+        url = "/_synapse/admin/v2/users/@unknown_person:test/delete_devices"
+        request, channel = self.make_request(
+            "POST", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+    def test_user_is_not_local(self):
+        """
+        Tests that a lookup for a user that is not a local returns a 400
+        """
+        url = "/_synapse/admin/v2/users/@unknown_person:unknown_domain/delete_devices"
+
+        request, channel = self.make_request(
+            "POST", url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual("Can only lookup local users", channel.json_body["error"])
+
+    def test_unknown_devices(self):
+        """
+        Tests that a remove of a device that does not exist returns 200.
+        """
+        body = json.dumps({"devices": ["unknown_device1", "unknown_device2"]})
+        request, channel = self.make_request(
+            "POST",
+            self.url,
+            access_token=self.admin_user_tok,
+            content=body.encode(encoding="utf_8"),
+        )
+        self.render(request)
+
+        # Delete unknown devices returns status 200
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+    def test_delete_devices(self):
+        """
+        Tests that a remove of devices is successfully
+        """
+
+        # Create devices
+        number_devices = 5
+        for n in range(number_devices):
+            self.login("user", "pass")
+
+        # Get devices
+        res = self.get_success(self.handler.get_devices_by_user(self.other_user))
+        self.assertEqual(number_devices, len(res))
+
+        # Create list of device IDs
+        device_ids = []
+        for d in res:
+            device_ids.append(str(d["device_id"]))
+
+        # Delete devices
+        body = json.dumps({"devices": device_ids})
+        request, channel = self.make_request(
+            "POST",
+            self.url,
+            access_token=self.admin_user_tok,
+            content=body.encode(encoding="utf_8"),
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+
+        res = self.get_success(self.handler.get_devices_by_user(self.other_user))
+        self.assertEqual(0, len(res))