From 6f6ee0436e45065fd47189e29b2f33806c22ccd6 Mon Sep 17 00:00:00 2001
From: Hazelnoot <acomputerdog@gmail.com>
Date: Tue, 30 Sep 2025 21:54:34 -0400
Subject: [PATCH] verify recursion limit in MockResolver

---
 .../src/core/activitypub/ApResolverService.ts        |  4 ++--
 packages/backend/test/misc/mock-resolver.ts          | 12 ++++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/packages/backend/src/core/activitypub/ApResolverService.ts b/packages/backend/src/core/activitypub/ApResolverService.ts
index d53e265d36..5aad924671 100644
--- a/packages/backend/src/core/activitypub/ApResolverService.ts
+++ b/packages/backend/src/core/activitypub/ApResolverService.ts
@@ -30,7 +30,7 @@ import { ApRequestService } from './ApRequestService.js';
 import type { IObject, ApObject, IAnonymousObject } from './type.js';
 
 export class Resolver {
-	private history: Set<string>;
+	protected readonly history: Set<string>;
 	private user?: MiLocalUser;
 	private logger: Logger;
 
@@ -52,7 +52,7 @@ export class Resolver {
 		private readonly apLogService: ApLogService,
 		private readonly apUtilityService: ApUtilityService,
 		private readonly cacheService: CacheService,
-		private recursionLimit = 256,
+		protected readonly recursionLimit = 256,
 	) {
 		this.history = new Set();
 		this.logger = this.loggerService.getLogger('ap-resolve');
diff --git a/packages/backend/test/misc/mock-resolver.ts b/packages/backend/test/misc/mock-resolver.ts
index 34241d13cb..79da74d7b4 100644
--- a/packages/backend/test/misc/mock-resolver.ts
+++ b/packages/backend/test/misc/mock-resolver.ts
@@ -26,6 +26,8 @@ import { fromTuple } from '@/misc/from-tuple.js';
 import { SystemAccountService } from '@/core/SystemAccountService.js';
 import { bindThis } from '@/decorators.js';
 import { Resolver } from '@/core/activitypub/ApResolverService.js';
+import { DI } from '@/di-symbols.js';
+import { IdentifiableError } from '@/misc/identifiable-error.js';
 
 type MockResponse = {
 	type: string;
@@ -66,6 +68,7 @@ export class MockResolver extends Resolver {
 	}
 
 	public clear(): void {
+		this.history.clear();
 		this.#responseMap.clear();
 		this.#remoteGetTrials.length = 0;
 	}
@@ -81,6 +84,15 @@ export class MockResolver extends Resolver {
 		value = fromTuple(value);
 		if (typeof value !== 'string') return value;
 
+		// Check history - copied from Resolver._resolve
+		if (this.history.has(value)) {
+			throw new IdentifiableError('0dc86cf6-7cd6-4e56-b1e6-5903d62d7ea5', `failed to resolve ${value}: recursive resolution blocked`);
+		}
+		if (this.history.size > this.recursionLimit) {
+			throw new IdentifiableError('d592da9f-822f-4d91-83d7-4ceefabcf3d2', `failed to resolve ${value}: hit recursion limit`);
+		}
+		this.history.add(value);
+
 		this.#remoteGetTrials.push(value);
 		const r = this.#responseMap.get(value);