From 3ff8a619f5ed9d12b72858bfbbe3859e77dd064c Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Thu, 7 Jun 2018 16:37:19 +0100
Subject: [PATCH] UserErasureStore

to store which users have been erased
---
 synapse/storage/__init__.py                   |   2 +
 .../storage/schema/delta/50/erasure_store.sql |  21 ++++
 synapse/storage/user_erasure_store.py         | 103 ++++++++++++++++++
 3 files changed, 126 insertions(+)
 create mode 100644 synapse/storage/schema/delta/50/erasure_store.sql
 create mode 100644 synapse/storage/user_erasure_store.py

diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index 979fa2243..e843b702b 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -20,6 +20,7 @@ import time
 import logging
 
 from synapse.storage.devices import DeviceStore
+from synapse.storage.user_erasure_store import UserErasureStore
 from .appservice import (
     ApplicationServiceStore, ApplicationServiceTransactionStore
 )
@@ -88,6 +89,7 @@ class DataStore(RoomMemberStore, RoomStore,
                 DeviceInboxStore,
                 UserDirectoryStore,
                 GroupServerStore,
+                UserErasureStore,
                 ):
 
     def __init__(self, db_conn, hs):
diff --git a/synapse/storage/schema/delta/50/erasure_store.sql b/synapse/storage/schema/delta/50/erasure_store.sql
new file mode 100644
index 000000000..5d8641a9a
--- /dev/null
+++ b/synapse/storage/schema/delta/50/erasure_store.sql
@@ -0,0 +1,21 @@
+/* Copyright 2018 New Vector Ltd
+ *
+ * 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.
+ */
+
+-- a table of users who have requested that their details be erased
+CREATE TABLE erased_users (
+    user_id TEXT NOT NULL
+);
+
+CREATE UNIQUE INDEX erased_users_user ON erased_users(user_id);
diff --git a/synapse/storage/user_erasure_store.py b/synapse/storage/user_erasure_store.py
new file mode 100644
index 000000000..47bfc01e8
--- /dev/null
+++ b/synapse/storage/user_erasure_store.py
@@ -0,0 +1,103 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd
+#
+# 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 operator
+
+from twisted.internet import defer
+
+from synapse.storage._base import SQLBaseStore
+from synapse.util.caches.descriptors import cachedList, cached
+
+
+class UserErasureWorkerStore(SQLBaseStore):
+    @cached()
+    def is_user_erased(self, user_id):
+        """
+        Check if the given user id has requested erasure
+
+        Args:
+            user_id (str): full user id to check
+
+        Returns:
+            Deferred[bool]: True if the user has requested erasure
+        """
+        return self._simple_select_onecol(
+            table="erased_users",
+            keyvalues={"user_id": user_id},
+            retcol="1",
+            desc="is_user_erased",
+        ).addCallback(operator.truth)
+
+    @cachedList(
+        cached_method_name="is_user_erased",
+        list_name="user_ids",
+        inlineCallbacks=True,
+    )
+    def are_users_erased(self, user_ids):
+        """
+        Checks which users in a list have requested erasure
+
+        Args:
+            user_ids (iterable[str]): full user id to check
+
+        Returns:
+            Deferred[dict[str, bool]]:
+                for each user, whether the user has requested erasure.
+        """
+        # this serves the dual purpose of (a) making sure we can do len and
+        # iterate it multiple times, and (b) avoiding duplicates.
+        user_ids = tuple(set(user_ids))
+
+        def _get_erased_users(txn):
+            txn.execute(
+                "SELECT user_id FROM erased_users WHERE user_id IN (%s)" % (
+                    ",".join("?" * len(user_ids))
+                ),
+                user_ids,
+            )
+            return set(r[0] for r in txn)
+
+        erased_users = yield self.runInteraction(
+            "are_users_erased", _get_erased_users,
+        )
+        res = dict((u, u in erased_users) for u in user_ids)
+        defer.returnValue(res)
+
+
+class UserErasureStore(UserErasureWorkerStore):
+    def mark_user_erased(self, user_id):
+        """Indicate that user_id wishes their message history to be erased.
+
+        Args:
+            user_id (str): full user_id to be erased
+        """
+        def f(txn):
+            # first check if they are already in the list
+            txn.execute(
+                "SELECT 1 FROM erased_users WHERE user_id = ?",
+                (user_id, )
+            )
+            if txn.fetchone():
+                return
+
+            # they are not already there: do the insert.
+            txn.execute(
+                "INSERT INTO erased_users (user_id) VALUES (?)",
+                (user_id, )
+            )
+
+            self._invalidate_cache_and_stream(
+                txn, self.is_user_erased, (user_id,)
+            )
+        return self.runInteraction("mark_user_erased", f)