feat(automod): MIME type trigger (#247)

backend/src/plugins/Automod/AutomodPlugin.ts

@@ -114,6 +114,21 @@ const configPreprocessor: ConfigPreprocessorFn<AutomodPluginType> = options => {
                 ]);
               }
             }
+
+            if (triggerObj[triggerName].match_mime_type) {
+              const white = triggerObj[triggerName].match_mime_type.whitelist_enabled;
+              const black = triggerObj[triggerName].match_mime_type.blacklist_enabled;
+
+              if (white && black) {
+                throw new StrictValidationError([
+                  `Cannot have both blacklist and whitelist enabled at rule <${rule.name}/match_mime_type>`,
+                ]);
+              } else if (!white && !black) {
+                throw new StrictValidationError([
+                  `Must have either blacklist or whitelist enabled at rule <${rule.name}/match_mime_type>`,
+                ]);
+              }
+            }
           }
         }
       }

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

@@ -11,6 +11,7 @@ import { KickTrigger } from "./kick";
 import { LineSpamTrigger } from "./lineSpam";
 import { LinkSpamTrigger } from "./linkSpam";
 import { MatchAttachmentTypeTrigger } from "./matchAttachmentType";
+import { MatchMimeTypeTrigger } from "./matchMimeType";
 import { MatchInvitesTrigger } from "./matchInvites";
 import { MatchLinksTrigger } from "./matchLinks";
 import { MatchRegexTrigger } from "./matchRegex";
@@ -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,
@@ -72,6 +74,7 @@ export const AvailableTriggers = t.type({
   match_invites: MatchInvitesTrigger.configType,
   match_links: MatchLinksTrigger.configType,
   match_attachment_type: MatchAttachmentTypeTrigger.configType,
+  match_mime_type: MatchMimeTypeTrigger.configType,
   member_join: MemberJoinTrigger.configType,
   member_leave: MemberLeaveTrigger.configType,
   role_added: RoleAddedTrigger.configType,

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

@@ -0,0 +1,79 @@
+import { automodTrigger } from "../helpers";
+import * as t from "io-ts";
+import { asSingleLine, messageSummary, verboseChannelMention } from "../../../utils";
+import { GuildChannel, Util } from "discord.js";
+
+interface MatchResultType {
+  matchedType: string;
+  mode: "blacklist" | "whitelist";
+}
+
+export const MatchMimeTypeTrigger = automodTrigger<MatchResultType>()({
+  configType: t.type({
+    mime_type_blacklist: t.array(t.string),
+    blacklist_enabled: t.boolean,
+    mime_type_whitelist: t.array(t.string),
+    whitelist_enabled: t.boolean,
+  }),
+
+  defaultConfig: {
+    mime_type_blacklist: [],
+    blacklist_enabled: false,
+    mime_type_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 { contentType } = attachment;
+
+      const blacklist = trigger.blacklist_enabled
+        ? (trigger.mime_type_blacklist ?? []).map(_t => _t.toLowerCase())
+        : null;
+
+      if (contentType && blacklist?.includes(contentType)) {
+        return {
+          extra: {
+            matchedType: contentType,
+            mode: "blacklist",
+          },
+        };
+      }
+
+      const whitelist = trigger.whitelist_enabled
+        ? (trigger.mime_type_whitelist ?? []).map(_t => _t.toLowerCase())
+        : null;
+
+      if (whitelist && (!contentType || !whitelist.includes(contentType))) {
+        return {
+          extra: {
+            matchedType: contentType || "<unknown>",
+            mode: "whitelist",
+          },
+        };
+      }
+
+      return null;
+    }
+  },
+
+  renderMatchInformation({ pluginData, contexts, matchResult }) {
+    const { message } = contexts[0];
+    const channel = pluginData.guild.channels.resolve(message!.channel_id);
+    const prettyChannel = verboseChannelMention(channel as GuildChannel);
+    const { matchedType, mode } = matchResult.extra;
+
+    return (
+      asSingleLine(`
+        Matched MIME type \`${Util.escapeInlineCode(matchedType)}\`
+        (${mode === "blacklist" ? "blacklisted" : "not in whitelist"})
+        in message (\`${message!.id}\`) in ${prettyChannel}
+      `) + messageSummary(message!)
+    );
+  },
+});