forkbomb DOS mitigation

packages/backend/src/remote/activitypub/kernel/update/index.ts

@@ -10,7 +10,7 @@ import { updatePerson } from '../../models/person.js';
  */
 export default async (actor: CacheableRemoteUser, activity: IUpdate): Promise<string> => {
 	if ('actor' in activity && actor.uri !== activity.actor) {
-		return `skip: invalid actor`;
+		return 'skip: invalid actor';
 	}
 
 	apLogger.debug('Update');
@@ -24,10 +24,10 @@ export default async (actor: CacheableRemoteUser, activity: IUpdate): Promise<st
 
 	if (isActor(object)) {
 		await updatePerson(actor.uri!, resolver, object);
-		return `ok: Person updated`;
+		return 'ok: Person updated';
 	} else if (getApType(object) === 'Question') {
-		await updateQuestion(object).catch(e => console.log(e));
-		return `ok: Question updated`;
+		await updateQuestion(object, resolver).catch(e => console.log(e));
+		return 'ok: Question updated';
 	} else {
 		return `skip: Unknown type: ${getApType(object)}`;
 	}

packages/backend/src/remote/activitypub/models/person.ts

@@ -271,7 +271,7 @@ export async function createPerson(uri: string, resolver?: Resolver): Promise<Us
 	});
 	//#endregion
 
-	await updateFeatured(user!.id).catch(err => logger.error(err));
+	await updateFeatured(user!.id, resolver).catch(err => logger.error(err));
 
 	return user!;
 }
@@ -384,7 +384,7 @@ export async function updatePerson(uri: string, resolver?: Resolver | null, hint
 		followerSharedInbox: person.sharedInbox || (person.endpoints ? person.endpoints.sharedInbox : undefined),
 	});
 
-	await updateFeatured(exist.id).catch(err => logger.error(err));
+	await updateFeatured(exist.id, resolver).catch(err => logger.error(err));
 }
 
 /**
@@ -462,14 +462,14 @@ export function analyzeAttachments(attachments: IObject | IObject[] | undefined)
 	return { fields, services };
 }
 
-export async function updateFeatured(userId: User['id']) {
+export async function updateFeatured(userId: User['id'], resolver?: Resolver) {
 	const user = await Users.findOneByOrFail({ id: userId });
 	if (!Users.isRemoteUser(user)) return;
 	if (!user.featured) return;
 
 	logger.info(`Updating the featured: ${user.uri}`);
 
-	const resolver = new Resolver();
+	if (resolver == null) resolver = new Resolver();
 
 	// Resolve to (Ordered)Collection Object
 	const collection = await resolver.resolveCollection(user.featured);

packages/backend/src/remote/activitypub/models/question.ts

@@ -1,9 +1,9 @@
 import config from '@/config/index.js';
+import { Notes, Polls } from '@/models/index.js';
+import { IPoll } from '@/models/entities/poll.js';
 import Resolver from '../resolver.js';
 import { IObject, IQuestion, isQuestion } from '../type.js';
 import { apLogger } from '../logger.js';
-import { Notes, Polls } from '@/models/index.js';
-import { IPoll } from '@/models/entities/poll.js';
 
 export async function extractPollFromQuestion(source: string | IObject, resolver?: Resolver): Promise<IPoll> {
 	if (resolver == null) resolver = new Resolver();
@@ -40,7 +40,7 @@ export async function extractPollFromQuestion(source: string | IObject, resolver
  * @param uri URI of AP Question object
  * @returns true if updated
  */
-export async function updateQuestion(value: any) {
+export async function updateQuestion(value: any, resolver?: Resolver) {
 	const uri = typeof value === 'string' ? value : value.id;
 
 	// URIがこのサーバーを指しているならスキップ
@@ -55,7 +55,7 @@ export async function updateQuestion(value: any) {
 	//#endregion
 
 	// resolve new Question object
-	const resolver = new Resolver();
+	if (resolver == null) resolver = new Resolver();
 	const question = await resolver.resolve(value) as IQuestion;
 	apLogger.debug(`fetched question: ${JSON.stringify(question, null, 2)}`);
 

packages/backend/src/remote/activitypub/resolver.ts

@@ -4,10 +4,7 @@ import { ILocalUser } from '@/models/entities/user.js';
 import { getInstanceActor } from '@/services/instance-actor.js';
 import { fetchMeta } from '@/misc/fetch-meta.js';
 import { extractDbHost, isSelfHost } from '@/misc/convert-host.js';
-import { signedGet } from './request.js';
-import { IObject, isCollectionOrOrderedCollection, ICollection, IOrderedCollection } from './type.js';
 import { FollowRequests, Notes, NoteReactions, Polls, Users } from '@/models/index.js';
-import { parseUri } from './db-resolver.js';
 import renderNote from '@/remote/activitypub/renderer/note.js';
 import { renderLike } from '@/remote/activitypub/renderer/like.js';
 import { renderPerson } from '@/remote/activitypub/renderer/person.js';
@@ -15,12 +12,16 @@ import renderQuestion from '@/remote/activitypub/renderer/question.js';
 import renderCreate from '@/remote/activitypub/renderer/create.js';
 import { renderActivity } from '@/remote/activitypub/renderer/index.js';
 import renderFollow from '@/remote/activitypub/renderer/follow.js';
+import { parseUri } from './db-resolver.js';
+import { IObject, isCollectionOrOrderedCollection, ICollection, IOrderedCollection } from './type.js';
+import { signedGet } from './request.js';
 
 export default class Resolver {
 	private history: Set<string>;
 	private user?: ILocalUser;
+	private recursionLimit?: number;
 
-	constructor() {
+	constructor(recursionLimit = 100) {
 		this.history = new Set();
 	}
 
@@ -60,6 +61,10 @@ export default class Resolver {
 			throw new Error('cannot resolve already resolved one');
 		}
 
+		if (this.recursionLimit && this.history.size > this.recursionLimit) {
+			throw new Error('hit recursion limit');
+		}
+
 		this.history.add(value);
 
 		const host = extractDbHost(value);
@@ -123,7 +128,7 @@ export default class Resolver {
 				if (parsed.rest == null || !/^\w+$/.test(parsed.rest)) throw new Error('resolveLocal: invalid follow URI');
 
 				return Promise.all(
-					[parsed.id, parsed.rest].map(id => Users.findOneByOrFail({ id }))
+					[parsed.id, parsed.rest].map(id => Users.findOneByOrFail({ id })),
 				)
 				.then(([follower, followee]) => renderActivity(renderFollow(follower, followee, url)));
 			default: