Add an admin API endpoint to support per-user feature flags (#15344)

9 files changed, 408 insertions, 0 deletions

diff --git a/changelog.d/15344.feature b/changelog.d/15344.feature
new file mode 100644
index 0000000000..44262e9bd8
--- /dev/null
+++ b/changelog.d/15344.feature
@@ -0,0 +1 @@
+Add an admin API endpoint to support per-user feature flags.
diff --git a/docs/admin_api/experimental_features.md b/docs/admin_api/experimental_features.md
new file mode 100644
index 0000000000..c1aebe4b01
--- /dev/null
+++ b/docs/admin_api/experimental_features.md
@@ -0,0 +1,54 @@
+# Experimental Features API
+
+This API allows a server administrator to enable or disable some experimental features on a per-user
+basis. Currently supported features are [msc3026](https://github.com/matrix-org/matrix-spec-proposals/pull/3026): busy 
+presence state enabled, [msc2654](https://github.com/matrix-org/matrix-spec-proposals/pull/2654): enable unread counts,
+[msc3881](https://github.com/matrix-org/matrix-spec-proposals/pull/3881): enable remotely toggling push notifications 
+for another client, and [msc3967](https://github.com/matrix-org/matrix-spec-proposals/pull/3967): do not require
+UIA when first uploading cross-signing keys. 
+
+
+To use it, you will need to authenticate by providing an `access_token`
+for a server admin: see [Admin API](../usage/administration/admin_api/).
+
+## Enabling/Disabling Features
+
+This API allows a server administrator to enable experimental features for a given user. The request must 
+provide a body containing the user id and listing the features to enable/disable in the following format:
+```json
+{
+   "features": {
+      "msc3026":true,
+      "msc2654":true
+   }
+}
+```
+where true is  used to enable the feature, and false is used to disable the feature.
+
+
+The API is:
+
+```
+PUT /_synapse/admin/v1/experimental_features/<user_id>
+```
+
+## Listing Enabled Features
+ 
+To list which features are enabled/disabled for a given user send a request to the following API:
+
+```
+GET /_synapse/admin/v1/experimental_features/<user_id>
+```
+
+It will return a list of possible features and indicate whether they are enabled or disabled for the
+user like so:
+```json
+{
+   "features": {
+      "msc3026": true,
+      "msc2654": true,
+      "msc3881": false,
+      "msc3967": false
+   }
+}
+```
\ No newline at end of file
diff --git a/synapse/_scripts/synapse_port_db.py b/synapse/_scripts/synapse_port_db.py
index 56d5aeb0dd..27fee3d9a9 100755
--- a/synapse/_scripts/synapse_port_db.py
+++ b/synapse/_scripts/synapse_port_db.py
@@ -125,6 +125,7 @@ BOOLEAN_COLUMNS = {
     "users": ["shadow_banned", "approved"],
     "un_partial_stated_event_stream": ["rejection_status_changed"],
     "users_who_share_rooms": ["share_private"],
+    "per_user_experimental_features": ["enabled"],
 }
 
 
diff --git a/synapse/rest/admin/__init__.py b/synapse/rest/admin/__init__.py
index 770df261ce..c729364839 100644
--- a/synapse/rest/admin/__init__.py
+++ b/synapse/rest/admin/__init__.py
@@ -39,6 +39,7 @@ from synapse.rest.admin.event_reports import (
     EventReportDetailRestServlet,
     EventReportsRestServlet,
 )
+from synapse.rest.admin.experimental_features import ExperimentalFeaturesRestServlet
 from synapse.rest.admin.federation import (
     DestinationMembershipRestServlet,
     DestinationResetConnectionRestServlet,
@@ -292,6 +293,7 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     BackgroundUpdateEnabledRestServlet(hs).register(http_server)
     BackgroundUpdateRestServlet(hs).register(http_server)
     BackgroundUpdateStartJobRestServlet(hs).register(http_server)
+    ExperimentalFeaturesRestServlet(hs).register(http_server)
 
 
 def register_servlets_for_client_rest_resource(
diff --git a/synapse/rest/admin/experimental_features.py b/synapse/rest/admin/experimental_features.py
new file mode 100644
index 0000000000..1d409ac2b7
--- /dev/null
+++ b/synapse/rest/admin/experimental_features.py
@@ -0,0 +1,119 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C
+#
+#  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.
+
+
+from enum import Enum
+from http import HTTPStatus
+from typing import TYPE_CHECKING, Dict, Tuple
+
+from synapse.api.errors import SynapseError
+from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
+from synapse.rest.admin import admin_patterns, assert_requester_is_admin
+from synapse.types import JsonDict, UserID
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+
+class ExperimentalFeature(str, Enum):
+    """
+    Currently supported per-user features
+    """
+
+    MSC3026 = "msc3026"
+    MSC2654 = "msc2654"
+    MSC3881 = "msc3881"
+    MSC3967 = "msc3967"
+
+
+class ExperimentalFeaturesRestServlet(RestServlet):
+    """
+    Enable or disable experimental features for a user or determine which features are enabled
+    for a given user
+    """
+
+    PATTERNS = admin_patterns("/experimental_features/(?P<user_id>[^/]*)")
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastores().main
+        self.is_mine = hs.is_mine
+
+    async def on_GET(
+        self,
+        request: SynapseRequest,
+        user_id: str,
+    ) -> Tuple[int, JsonDict]:
+        """
+        List which features are enabled for a given user
+        """
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.is_mine(target_user):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "User must be local to check what experimental features are enabled.",
+            )
+
+        enabled_features = await self.store.list_enabled_features(user_id)
+
+        user_features = {}
+        for feature in ExperimentalFeature:
+            if feature in enabled_features:
+                user_features[feature] = True
+            else:
+                user_features[feature] = False
+        return HTTPStatus.OK, {"features": user_features}
+
+    async def on_PUT(
+        self, request: SynapseRequest, user_id: str
+    ) -> Tuple[HTTPStatus, Dict]:
+        """
+        Enable or disable the provided features for the requester
+        """
+        await assert_requester_is_admin(self.auth, request)
+
+        body = parse_json_object_from_request(request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.is_mine(target_user):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "User must be local to enable experimental features.",
+            )
+
+        features = body.get("features")
+        if not features:
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST, "You must provide features to set."
+            )
+
+        # validate the provided features
+        validated_features = {}
+        for feature, enabled in features.items():
+            try:
+                validated_feature = ExperimentalFeature(feature)
+                validated_features[validated_feature] = enabled
+            except ValueError:
+                raise SynapseError(
+                    HTTPStatus.BAD_REQUEST,
+                    f"{feature!r} is not recognised as a valid experimental feature.",
+                )
+
+        await self.store.set_features_for_user(user_id, validated_features)
+
+        return HTTPStatus.OK, {}
diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index dc3948c170..0032a92f49 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -43,6 +43,7 @@ from .event_federation import EventFederationStore
 from .event_push_actions import EventPushActionsStore
 from .events_bg_updates import EventsBackgroundUpdatesStore
 from .events_forward_extremities import EventForwardExtremitiesStore
+from .experimental_features import ExperimentalFeaturesStore
 from .filtering import FilteringWorkerStore
 from .keys import KeyStore
 from .lock import LockStore
@@ -82,6 +83,7 @@ logger = logging.getLogger(__name__)
 
 class DataStore(
     EventsBackgroundUpdatesStore,
+    ExperimentalFeaturesStore,
     DeviceStore,
     RoomMemberStore,
     RoomStore,
diff --git a/synapse/storage/databases/main/experimental_features.py b/synapse/storage/databases/main/experimental_features.py
new file mode 100644
index 0000000000..cf3226ae5a
--- /dev/null
+++ b/synapse/storage/databases/main/experimental_features.py
@@ -0,0 +1,75 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C
+#
+#  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.
+
+from typing import TYPE_CHECKING, Dict
+
+from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
+from synapse.storage.databases.main import CacheInvalidationWorkerStore
+from synapse.types import StrCollection
+from synapse.util.caches.descriptors import cached
+
+if TYPE_CHECKING:
+    from synapse.rest.admin.experimental_features import ExperimentalFeature
+    from synapse.server import HomeServer
+
+
+class ExperimentalFeaturesStore(CacheInvalidationWorkerStore):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ) -> None:
+        super().__init__(database, db_conn, hs)
+
+    @cached()
+    async def list_enabled_features(self, user_id: str) -> StrCollection:
+        """
+        Checks to see what features are enabled for a given user
+        Args:
+            user:
+                the user to be queried on
+        Returns:
+            the features currently enabled for the user
+        """
+        enabled = await self.db_pool.simple_select_list(
+            "per_user_experimental_features",
+            {"user_id": user_id, "enabled": True},
+            ["feature"],
+        )
+
+        return [feature["feature"] for feature in enabled]
+
+    async def set_features_for_user(
+        self,
+        user: str,
+        features: Dict["ExperimentalFeature", bool],
+    ) -> None:
+        """
+        Enables or disables features for a given user
+        Args:
+            user:
+                the user for whom to enable/disable the features
+            features:
+                pairs of features and True/False for whether the feature should be enabled
+        """
+        for feature, enabled in features.items():
+            await self.db_pool.simple_upsert(
+                table="per_user_experimental_features",
+                keyvalues={"feature": feature, "user_id": user},
+                values={"enabled": enabled},
+                insertion_values={"user_id": user, "feature": feature},
+            )
+
+            await self.invalidate_cache_and_stream("list_enabled_features", (user,))
diff --git a/synapse/storage/schema/main/delta/76/03_per_user_experimental_features.sql b/synapse/storage/schema/main/delta/76/03_per_user_experimental_features.sql
new file mode 100644
index 0000000000..c4ef81846c
--- /dev/null
+++ b/synapse/storage/schema/main/delta/76/03_per_user_experimental_features.sql
@@ -0,0 +1,27 @@
+/* Copyright 2023 The Matrix.org Foundation C.I.C
+ *
+ * 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.
+ */
+
+-- Table containing experimental features and whether they are enabled for a given user
+CREATE TABLE per_user_experimental_features (
+    -- The User ID to check/set the feature for
+    user_id TEXT NOT NULL,
+    -- Contains features to be enabled/disabled
+    feature TEXT NOT NULL,
+    -- whether the feature is enabled/disabled for a given user, defaults to disabled
+    enabled BOOLEAN DEFAULT FALSE,
+    FOREIGN KEY (user_id) REFERENCES users(name),
+    PRIMARY KEY (user_id, feature)
+);
+
diff --git a/tests/rest/admin/test_admin.py b/tests/rest/admin/test_admin.py
index a8f6436836..645a00b4b1 100644
--- a/tests/rest/admin/test_admin.py
+++ b/tests/rest/admin/test_admin.py
@@ -372,3 +372,130 @@ class PurgeHistoryTestCase(unittest.HomeserverTestCase):
 
         self.assertEqual(200, channel.code, msg=channel.json_body)
         self.assertEqual("complete", channel.json_body["status"])
+
+
+class ExperimentalFeaturesTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        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_tok = self.login("user", "pass")
+
+        self.url = "/_synapse/admin/v1/experimental_features"
+
+    def test_enable_and_disable(self) -> None:
+        """
+        Test basic functionality of ExperimentalFeatures endpoint
+        """
+        # test enabling features works
+        url = f"{self.url}/{self.other_user}"
+        channel = self.make_request(
+            "PUT",
+            url,
+            content={
+                "features": {"msc3026": True, "msc2654": True},
+            },
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200)
+
+        # list which features are enabled and ensure the ones we enabled are listed
+        self.assertEqual(channel.code, 200)
+        url = f"{self.url}/{self.other_user}"
+        channel = self.make_request(
+            "GET",
+            url,
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            True,
+            channel.json_body["features"]["msc3026"],
+        )
+        self.assertEqual(
+            True,
+            channel.json_body["features"]["msc2654"],
+        )
+
+        # test disabling a feature works
+        url = f"{self.url}/{self.other_user}"
+        channel = self.make_request(
+            "PUT",
+            url,
+            content={"features": {"msc3026": False}},
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200)
+
+        # list the features enabled/disabled and ensure they are still are correct
+        self.assertEqual(channel.code, 200)
+        url = f"{self.url}/{self.other_user}"
+        channel = self.make_request(
+            "GET",
+            url,
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            False,
+            channel.json_body["features"]["msc3026"],
+        )
+        self.assertEqual(
+            True,
+            channel.json_body["features"]["msc2654"],
+        )
+        self.assertEqual(
+            False,
+            channel.json_body["features"]["msc3881"],
+        )
+        self.assertEqual(
+            False,
+            channel.json_body["features"]["msc3967"],
+        )
+
+        # test nothing blows up if you try to disable a feature that isn't already enabled
+        url = f"{self.url}/{self.other_user}"
+        channel = self.make_request(
+            "PUT",
+            url,
+            content={"features": {"msc3026": False}},
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 200)
+
+        # test trying to enable a feature without an admin access token is denied
+        url = f"{self.url}/f{self.other_user}"
+        channel = self.make_request(
+            "PUT",
+            url,
+            content={"features": {"msc3881": True}},
+            access_token=self.other_user_tok,
+        )
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {"errcode": "M_FORBIDDEN", "error": "You are not a server admin"},
+        )
+
+        # test trying to enable a bogus msc is denied
+        url = f"{self.url}/{self.other_user}"
+        channel = self.make_request(
+            "PUT",
+            url,
+            content={"features": {"msc6666": True}},
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(channel.code, 400)
+        self.assertEqual(
+            channel.json_body,
+            {
+                "errcode": "M_UNKNOWN",
+                "error": "'msc6666' is not recognised as a valid experimental feature.",
+            },
+        )