Add a new protection, MessageIsMedia

* Simply redacts any media sent to the room, by anyone
* Meant to serve as a temporary measure to prevent image spam,
  in conjunction with FirstMessageIsImage

src/protections/MessageIsMedia.ts

@@ -0,0 +1,49 @@
+/*
+Copyright 2019 - 2021 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 { IProtection } from "./IProtection";
+import { Mjolnir } from "../Mjolnir";
+import { LogLevel, Permalinks, UserID } from "matrix-bot-sdk";
+import { logMessage } from "../LogProxy";
+import config from "../config";
+
+export class MessageIsMedia implements IProtection {
+
+    constructor() {
+    }
+
+    public get name(): string {
+        return 'MessageIsMediaProtection';
+    }
+
+    public async handleEvent(mjolnir: Mjolnir, roomId: string, event: any): Promise<any> {
+        if (event['type'] === 'm.room.message') {
+            const content = event['content'] || {};
+            const msgtype = content['msgtype'] || 'm.text';
+            const formattedBody = content['formatted_body'] || '';
+            const isMedia = msgtype === 'm.image' || msgtype === 'm.video' || formattedBody.toLowerCase().includes('<img');
+            if (isMedia) {
+                await logMessage(LogLevel.WARN, "MessageIsMedia", `Redacting event from ${event['sender']} for posting an image/video. ${Permalinks.forEvent(roomId, event['event_id'], [new UserID(await mjolnir.client.getUserId()).domain])}`);
+                // Redact the event
+                if (!config.noop) {
+                    await mjolnir.client.redactEvent(roomId, event['event_id'], "Images/videos are not permitted here");
+                } else {
+                    await logMessage(LogLevel.WARN, "MessageIsMedia", `Tried to redact ${event['event_id']} in ${roomId} but Mjolnir is running in no-op mode`, roomId);
+                }
+            }
+        }
+    }
+}

src/protections/protections.ts

@@ -19,6 +19,7 @@ import { IProtection } from "./IProtection";
 import { BasicFlooding, MAX_PER_MINUTE } from "./BasicFlooding";
 import { WordList } from "./WordList";
 import { MessageIsVoice } from "./MessageIsVoice";
+import { MessageIsMedia } from "./MessageIsMedia";
 
 export const PROTECTIONS: PossibleProtections = {
     [new FirstMessageIsImage().name]: {
@@ -40,6 +41,10 @@ export const PROTECTIONS: PossibleProtections = {
         description: "If a user posts a voice message, that message will be redacted. No bans are issued.",
         factory: () => new MessageIsVoice(),
     },
+    [new MessageIsMedia().name]: {
+        description: "If a user posts an image or video, that message will be redacted. No bans are issued.",
+        factory: () => new MessageIsMedia(),
+    }
 };
 
 export interface PossibleProtections {