WIP

config/default.yaml

@@ -192,3 +192,42 @@ web:
   abuseReporting:
     # Whether to enable this feature.
     enabled: false
+
+# Uncomment to enable support for undoable actions.
+#
+# As of this writing, the only undoable action is `softredact`.
+#
+#trashcan:
+#  # The room in which we store undoable actions for review.
+#  # Mjölnir will not create it. This can be the same as the
+#  # management room but it doesn't have to.
+#  roomAliasOrId: "#trashcan:localhost"
+#
+#  # Support for soft redactions, i.e. using Mjölnir to mark
+#  # messages as hidden pending moderation.
+#  #
+#  # As of this writing, this feature only works with develop
+#  # versions of Element Web, with feature
+#  # `feature_msc3531_hide_messages_pending_moderation`
+#  # enabled.
+#  #
+#  # Comment this out if you wish to disable soft redactions.
+#  softRedact:
+#    # After `goodAfterMs` milliseconds, any message hidden
+#    # pending moderation by Mjölnir will revert to visible
+#    # and vanish from the trashcan.
+#    # Ignored if `goodAfterMs` is >= `badAfterMs` or `retainMs`.
+#    goodAfterMs: .inf
+#
+#    # After `badAfterMs` milliseconds, any message hidden
+#    # pending moderation by Mjölnir will be irreversibly
+#    # deleted from homeservers and up-to-date clients and
+#    # vanish from the trashcan.
+#    # Ignored if `badAfterMs` is > `goodAfterMs` or `retainMs`.
+#    badAfterMs: .inf
+#
+#    # After `retainMs` milliseconds, any message hidden
+#    # pending moderation will vanish from the trashcan, without
+#    # further action.
+#    # Ignored if `retainMs` is > `goodAfterMs` or `badAfterMs`.
+#    retainMs: 604800000 # Approximately one week.

src/Mjolnir.ts

@@ -42,6 +42,7 @@ import { EventRedactionQueue, RedactUserInRoom } from "./queues/EventRedactionQu
 import * as htmlEscape from "escape-html";
 import { ReportManager } from "./report/ReportManager";
 import { WebAPIs } from "./webapis/WebAPIs";
+import { TrashManager } from "./trashcan/TrashManager";
 
 export const STATE_NOT_STARTED = "not_started";
 export const STATE_CHECKING_PERMISSIONS = "checking_permissions";
@@ -73,6 +74,8 @@ export class Mjolnir {
     private explicitlyProtectedRoomIds: string[] = [];
     private knownUnprotectedRooms: string[] = [];
     private webapis: WebAPIs;
+    public trashcanManager?: TrashManager;
+
     /**
      * Adds a listener to the client that will automatically accept invitations.
      * @param {MatrixClient} client
@@ -146,15 +149,25 @@ export class Mjolnir {
         } else {
             config.managementRoom = managementRoomId;
         }
-        await logMessage(LogLevel.INFO, "index", "Mjolnir is starting up. Use !mjolnir to query status.");
 
-        return new Mjolnir(client, protectedRooms, banLists);
+        let trashcanRoomId;
+        if (config.trashcan) {
+            trashcanRoomId = await client.resolveRoom(config.trashcan.roomAliasOrId);
+            const joinedRooms = await client.getJoinedRooms();
+            if (!joinedRooms.includes(trashcanRoomId)) {
+                await client.joinRoom(trashcanRoomId);
+            }
+        }
+
+        await logMessage(LogLevel.INFO, "index", "Mjolnir is starting up. Use !mjolnir to query status.");
+        return new Mjolnir(client, protectedRooms, banLists, trashcanRoomId);
     }
 
     constructor(
         public readonly client: MatrixClient,
         public readonly protectedRooms: { [roomId: string]: string },
         private banLists: BanList[],
+        trashcanRoomId?: string,
     ) {
         this.explicitlyProtectedRoomIds = Object.keys(this.protectedRooms);
 
@@ -222,6 +235,12 @@ export class Mjolnir {
         // Setup Web APIs
         console.log("Creating Web APIs");
         this.webapis = new WebAPIs(new ReportManager(this));
+
+        // Setup trashcan.
+        console.log("Creating Trashcan Manager");
+        if (trashcanRoomId) {
+            this.trashcanManager = new TrashManager(this, trashcanRoomId);
+        }
     }
 
     public get lists(): BanList[] {

src/commands/CommandHandler.ts

@@ -1,5 +1,5 @@
 /*
-Copyright 2019-2021 The Matrix.org Foundation C.I.C.
+Copyright 2019-2022 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.
@@ -24,7 +24,8 @@ import { execSyncCommand } from "./SyncCommand";
 import { execPermissionCheckCommand } from "./PermissionCheckCommand";
 import { execCreateListCommand } from "./CreateBanListCommand";
 import { execUnwatchCommand, execWatchCommand } from "./WatchUnwatchCommand";
-import { execRedactCommand } from "./RedactCommand";
+import { execHardRedactCommand } from "./HardRedactCommand";
+import { execSoftRedactCommand } from "./SoftRedactCommand";
 import { execImportCommand } from "./ImportCommand";
 import { execSetDefaultListCommand } from "./SetDefaultBanListCommand";
 import { execDeactivateCommand } from "./DeactivateCommand";
@@ -63,7 +64,9 @@ export async function handleCommand(roomId: string, event: any, mjolnir: Mjolnir
         } else if (parts[1] === 'unwatch' && parts.length > 1) {
             return await execUnwatchCommand(roomId, event, mjolnir, parts);
         } else if (parts[1] === 'redact' && parts.length > 1) {
-            return await execRedactCommand(roomId, event, mjolnir, parts);
+            return await execHardRedactCommand(roomId, event, mjolnir, parts);
+        } else if (parts[1] === 'hide' && parts.length > 1) {
+            return await execSoftRedactCommand(roomId, event, mjolnir, parts);
         } else if (parts[1] === 'import' && parts.length > 2) {
             return await execImportCommand(roomId, event, mjolnir, parts);
         } else if (parts[1] === 'default' && parts.length > 2) {

src/commands/HardRedactCommand.ts

@@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2019-2022 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.
@@ -18,8 +18,16 @@ import { Mjolnir } from "../Mjolnir";
 import { redactUserMessagesIn } from "../utils";
 import { Permalinks } from "matrix-bot-sdk";
 
+/*!
+ * "Hard redaction", cannot be undone.
+ *
+ * Instruct all participant homeservers to permanently erase the
+ * contents of the message from the timeline and to request the
+ * same from all clients.
+ */
+
 // !mjolnir redact <user ID> [room alias] [limit]
-export async function execRedactCommand(roomId: string, event: any, mjolnir: Mjolnir, parts: string[]) {
+export async function execHardRedactCommand(roomId: string, event: any, mjolnir: Mjolnir, parts: string[]) {
     const userId = parts[2];
     let roomAlias: string|null = null;
     let limit = Number.parseInt(parts.length > 3 ? parts[3] : "", 10); // default to NaN for later

src/commands/SoftRedactCommand.ts

@@ -0,0 +1,66 @@
+/*
+Copyright 2022 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.
+*/
+
+import { Mjolnir } from "../Mjolnir";
+import { redactUserMessagesIn } from "../utils";
+import { Permalinks } from "matrix-bot-sdk";
+
+/*!
+ * "Soft redaction", aka "undoable redaction".
+ *
+ * 1. Instruct all clients to mark the message as hidden
+ *    pending moderation. Only moderators and the author
+ *    of the message may still see it.
+ * 2. Copy the message to the trashcan room.
+ * 3. In the trashcan room, moderators have the ability
+ *    to either restore the message or trash (i.e. redact)
+ *    it permanently.
+ */
+
+// !mjolnir hide <user ID> [room alias] [limit]
+export async function execSoftRedactCommand(roomId: string, instructionEvent: any, mjolnir: Mjolnir, parts: string[]) {
+    // This could either be an eventId or a userId.
+    const targetId = parts[2];
+    let roomAlias: string | null = null;
+    let limit = Number.parseInt(parts.length > 3 ? parts[3] : "", 10); // default to NaN for later
+    if (parts.length > 3 && isNaN(limit)) {
+        roomAlias = await mjolnir.client.resolveRoom(parts[3]);
+        if (parts.length > 4) {
+            limit = Number.parseInt(parts[4], 10);
+        }
+    }
+
+    // Make sure we always have a limit set
+    if (isNaN(limit)) limit = 1000;
+
+    const processingReactionId = await mjolnir.client.unstableApis.addReactionToEvent(roomId, instructionEvent['event_id'], 'In Progress');
+
+    if (userId[0] !== '@') {
+        // Assume it's a permalink
+        const parsed = Permalinks.parseUrl(parts[2]);
+        const targetRoomId = await mjolnir.client.resolveRoom(parsed.roomIdOrAlias);
+        await mjolnir.client.redactEvent(targetRoomId, parsed.eventId);
+        await mjolnir.client.unstableApis.addReactionToEvent(roomId, instructionEvent['event_id'], '✅');
+        await mjolnir.client.redactEvent(roomId, processingReactionId, 'done processing command');
+        return;
+    }
+
+    const targetRoomIds = roomAlias ? [roomAlias] : Object.keys(mjolnir.protectedRooms);
+    await redactUserMessagesIn(mjolnir.client, userId, targetRoomIds, limit);
+
+    await mjolnir.client.unstableApis.addReactionToEvent(roomId, instructionEvent['event_id'], '✅');
+    await mjolnir.client.redactEvent(roomId, processingReactionId, 'done processing');
+}

src/config.ts

@@ -76,7 +76,15 @@ interface IConfig {
         abuseReporting: {
             enabled: boolean;
         }
-    }
+    };
+    trashcan?: {
+        roomAliasOrId: string;
+        softRedact?: {
+            goodAfterMs: number;
+            badAfterMs: number;
+            retainMs: number;
+        }
+    };
 
     /**
      * Config options only set at runtime. Try to avoid using the objects