Merge pull request #56 from Alch-Emi/wordlist

Add a WordList protection

config/default.yaml

@@ -107,6 +107,25 @@ commands:
   additionalPrefixes:
     - "mjolnir_bot"
 
+# Configuration specific to certain toggleable protections
+protections:
+  # Configuration for the wordlist plugin, which can ban users based if they say certain
+  # blocked words shortly after joining.
+  wordlist:
+    # A list of words which should be monitored by the bot.  These will match if any part
+    # of the word is present in the message in any case.  e.g. "hello" also matches
+    # "HEllO".  Additionally, regular expressions can be used.
+    words:
+      - "CaSe"
+      - "InSeNsAtIve"
+      - "WoRd"
+      - "LiSt"
+
+    # How long after a user joins the server should the bot monitor their messages.  After
+    # this time, users can say words from the wordlist without being banned automatically.
+    # Set to zero to disable (users will always be banned if they say a bad word)
+    minutesBeforeTrusting: 20
+
 # Options for monitoring the health of the bot
 health:
   # healthz options. These options are best for use in container environments

src/config.ts

@@ -43,6 +43,12 @@ interface IConfig {
         allowNoPrefix: boolean;
         additionalPrefixes: string[];
     };
+    protections: {
+        wordlist: {
+            words: string[];
+            minutesBeforeTrusting: number;
+        };
+    };
     health: {
         healthz: {
             enabled: boolean;
@@ -89,6 +95,12 @@ const defaultConfig: IConfig = {
         allowNoPrefix: false,
         additionalPrefixes: [],
     },
+    protections: {
+        wordlist: {
+            words: [],
+            minutesBeforeTrusting: 20
+        }
+    },
     health: {
         healthz: {
             enabled: false,

src/protections/WordList.ts

@@ -0,0 +1,106 @@
+/*
+Copyright 2020 Emi Tatsuo Simpson et al.
+
+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, LogService } from "matrix-bot-sdk";
+import { logMessage } from "../LogProxy";
+import config from "../config";
+import { isTrueJoinEvent } from "../utils";
+
+export class WordList implements IProtection {
+
+    private justJoined: { [roomId: string]: { [username: string]: Date} } = {};
+    private badWords: RegExp;
+
+    constructor() {
+        // Create a mega-regex from all the tiny baby regexs
+        this.badWords = new RegExp(
+            "(" + config.protections.wordlist.words.join(")|(") + ")",
+            "i"
+        )
+    }
+
+    public get name(): string {
+        return 'WordList';
+    }
+
+    public async handleEvent(mjolnir: Mjolnir, roomId: string, event: any): Promise<any> {
+
+        const content = event['content'] || {};
+        const minsBeforeTrusting = config.protections.wordlist.minutesBeforeTrusting;
+
+        if (minsBeforeTrusting > 0) {
+            if (!this.justJoined[roomId]) this.justJoined[roomId] = {};
+
+            // When a new member logs in, store the time they joined.  This will be useful
+            // when we need to check if a message was sent within 20 minutes of joining
+            if (event['type'] === 'm.room.member') {
+                if (isTrueJoinEvent(event)) {
+                    const now = new Date();
+                    this.justJoined[roomId][event['state_key']] = now;
+                    LogService.info("WordList", `${event['state_key']} joined ${roomId} at ${now.toDateString()}`);
+                } else if (content['membership'] === 'leave' || content['membership'] === 'ban') {
+                    delete this.justJoined[roomId][event['sender']]
+                }
+
+                return;
+            }
+        }
+
+        if (event['type'] === 'm.room.message') {
+            const message = content['formatted_body'] || content['body'] || null;
+
+            // Check conditions first
+            if (minsBeforeTrusting > 0) {
+                const joinTime = this.justJoined[roomId][event['sender']]
+                if (joinTime) { // Disregard if the user isn't recently joined
+
+                    // Check if they did join recently, was it within the timeframe
+                    const now = new Date();
+                    if (now.valueOf() - joinTime.valueOf() > minsBeforeTrusting * 60 * 1000) {
+                        delete this.justJoined[roomId][event['sender']] // Remove the user
+                        LogService.info("WordList", `${event['sender']} is no longer considered suspect`);
+                        return
+                    }
+
+                } else {
+                    // The user isn't in the recently joined users list, no need to keep
+                    // looking
+                    return
+                }
+            }
+
+
+            // Perform the test
+            if (message && this.badWords.test(message)) {
+                await logMessage(LogLevel.WARN, "WordList", `Banning ${event['sender']} for word list violation in ${roomId}.`);
+                if (!config.noop) {
+                    await mjolnir.client.banUser(event['sender'], roomId, "Word list violation");
+                } else {
+                    await logMessage(LogLevel.WARN, "WordList", `Tried to ban ${event['sender']} in ${roomId} but Mjolnir is running in no-op mode`, roomId);
+                }
+
+                // Redact the event
+                if (!config.noop) {
+                    await mjolnir.client.redactEvent(roomId, event['event_id'], "spam");
+                } else {
+                    await logMessage(LogLevel.WARN, "WordList", `Tried to redact ${event['event_id']} in ${roomId} but Mjolnir is running in no-op mode`, roomId);
+                }
+            }
+        }
+    }
+}

src/protections/protections.ts

@@ -17,6 +17,7 @@ limitations under the License.
 import { FirstMessageIsImage } from "./FirstMessageIsImage";
 import { IProtection } from "./IProtection";
 import { BasicFlooding, MAX_PER_MINUTE } from "./BasicFlooding";
+import { WordList } from "./WordList";
 
 export const PROTECTIONS: PossibleProtections = {
     [new FirstMessageIsImage().name]: {
@@ -28,6 +29,11 @@ export const PROTECTIONS: PossibleProtections = {
         description: "If a user posts more than " + MAX_PER_MINUTE + " messages in 60s they'll be " +
             "banned for spam. This does not publish the ban to any of your ban lists.",
         factory: () => new BasicFlooding(),
+    },
+    [new WordList().name]: {
+        description: "If a user posts a monitored word a set amount of time after joining, they " +
+            "will be banned from that room.  This will not publish the ban to a ban list.",
+        factory: () => new WordList(),
     }
 };