feat(automod): MIME type trigger

backend/src/plugins/Automod/triggers/availableTriggers.ts

@@ -13,6 +13,7 @@ import { LinkSpamTrigger } from "./linkSpam";
 import { MatchAttachmentTypeTrigger } from "./matchAttachmentType";
 import { MatchInvitesTrigger } from "./matchInvites";
 import { MatchLinksTrigger } from "./matchLinks";
+import { MatchMimeTypeTrigger } from "./matchMimeType";
 import { MatchRegexTrigger } from "./matchRegex";
 import { MatchWordsTrigger } from "./matchWords";
 import { MemberJoinTrigger } from "./memberJoin";
@@ -37,6 +38,7 @@ export const availableTriggers: Record<string, AutomodTriggerBlueprint<any, any>
   match_invites: MatchInvitesTrigger,
   match_links: MatchLinksTrigger,
   match_attachment_type: MatchAttachmentTypeTrigger,
+  match_mime_type: MatchMimeTypeTrigger,
   member_join: MemberJoinTrigger,
   role_added: RoleAddedTrigger,
   role_removed: RoleRemovedTrigger,

backend/src/plugins/Automod/triggers/matchMimeType.ts

@@ -0,0 +1,84 @@
+import { automodTrigger } from "../helpers";
+import * as t from "io-ts";
+import fetch from "node-fetch";
+import { fromBuffer } from "file-type";
+import { asSingleLine, disableInlineCode, messageSummary, verboseChannelMention } from "src/utils";
+
+interface MatchResultType {
+  matchedType: string;
+  mode: "blacklist" | "whitelist";
+}
+
+export const MatchMimeTypeTrigger = automodTrigger<MatchResultType>()({
+  configType: t.type({
+    mimetype_blacklist: t.array(t.string),
+    blacklist_enabled: t.boolean,
+    mimetype_whitelist: t.array(t.string),
+    whitelist_enabled: t.boolean,
+  }),
+
+  defaultConfig: {
+    mimetype_blacklist: [],
+    blacklist_enabled: false,
+    mimetype_whitelist: [],
+    whitelist_enabled: false,
+  },
+
+  async match({ context, triggerConfig: trigger }) {
+    if (!context.message) return;
+
+    const { attachments } = context.message.data;
+    if (!attachments) return null;
+
+    for (const attachment of attachments) {
+      const res = await fetch(attachment.proxyURL);
+      const mimeType = await fromBuffer(await res.buffer());
+      if (!mimeType) return;
+
+      const blacklist = trigger.blacklist_enabled
+        ? (trigger.mimetype_blacklist || []).map(_t => _t.toLowerCase())
+        : null;
+
+      if (blacklist?.includes(mimeType.mime)) {
+        return {
+          extra: {
+            matchedType: mimeType.mime,
+            mode: "blacklist",
+          },
+        };
+      }
+
+      const whitelist = trigger.whitelist_enabled
+        ? (trigger.mimetype_whitelist || []).map(_t => _t.toLowerCase())
+        : null;
+
+      if (whitelist?.includes(mimeType.mime)) {
+        return {
+          extra: {
+            matchedType: mimeType.mime,
+            mode: "whitelist",
+          },
+        };
+      }
+
+      return null;
+    }
+  },
+
+  renderMatchInformation({ pluginData, contexts, matchResult }) {
+    const [context] = contexts;
+    const { message } = context;
+    if (!message) return;
+    const channel = pluginData.guild.channels.cache.get(message.channel_id);
+    const prettyChannel = verboseChannelMention(channel);
+    const { matchedType, mode } = matchResult.extra;
+
+    return (
+      asSingleLine(`
+        Matched MIME type \`${disableInlineCode(matchedType)}\`
+        (${mode === "blacklist" ? "(blacklisted)" : "(not in whitelist)"})
+        in message (\`${message.id}\`) in ${prettyChannel}
+      `) + messageSummary(message)
+    );
+  },
+});

package.json

@@ -9,6 +9,7 @@
     "codestyle-check": "prettier --check \"./{backend,dashboard}/{,!(node_modules)/**/}/*.ts\""
   },
   "devDependencies": {
+    "@types/node-fetch": "^2.5.12",
     "husky": "^3.0.9",
     "lint-staged": "^9.4.2",
     "prettier": "^1.19.1",
@@ -27,5 +28,9 @@
       "prettier --write",
       "git add"
     ]
+  },
+  "dependencies": {
+    "file-type": "^16.5.2",
+    "node-fetch": "^2.6.1"
   }
 }