From e70e990a1aa932a3f994b2205bacc2f35730aa01 Mon Sep 17 00:00:00 2001
From: Julian Lam <julian@nodebb.org>
Date: Thu, 22 May 2025 14:13:41 -0400
Subject: [PATCH] feat: restrict access to ap.probe method to registered users,
 add rate limiting protection

---
 src/activitypub/index.js             | 22 ++++++++++++++++++++++
 src/controllers/activitypub/index.js |  2 +-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/activitypub/index.js b/src/activitypub/index.js
index c87a0654f3..4067405080 100644
--- a/src/activitypub/index.js
+++ b/src/activitypub/index.js
@@ -27,6 +27,9 @@ const probeCache = ttl({
 	max: 500,
 	ttl: 1000 * 60 * 60, // 1 hour
 });
+const probeRateLimit = ttl({
+	ttl: 1000 * 3, // 3 seconds
+});
 
 const ActivityPub = module.exports;
 
@@ -506,6 +509,13 @@ ActivityPub.probe = async ({ uid, url }) => {
 	 *   - Returns a relative path if already available, true if not, and false otherwise.
 	 */
 
+	// Disable on config setting; restrict lookups to HTTPS-enabled URLs only
+	const { activitypubProbe } = meta.config;
+	const { protocol } = new URL(url);
+	if (!activitypubProbe || protocol !== 'https:') {
+		return false;
+	}
+
 	// Known resources
 	const [isNote, isMessage, isActor, isActorUrl] = await Promise.all([
 		posts.exists(url),
@@ -541,6 +551,17 @@ ActivityPub.probe = async ({ uid, url }) => {
 		}
 	}
 
+	// Guests not allowed to use expensive logic path
+	if (!uid) {
+		return false;
+	}
+
+	// One request allowed every 3 seconds (configured at top)
+	const limited = probeRateLimit.get(uid);
+	if (limited) {
+		return false;
+	}
+
 	// Cached result
 	if (probeCache.has(url)) {
 		return probeCache.get(url);
@@ -572,6 +593,7 @@ ActivityPub.probe = async ({ uid, url }) => {
 		return false;
 	}
 	try {
+		probeRateLimit.set(uid, true);
 		return await checkHeader(meta.config.activitypubProbeTimeout || 2000);
 	} catch (e) {
 		if (e.name === 'TimeoutError') {
diff --git a/src/controllers/activitypub/index.js b/src/controllers/activitypub/index.js
index 36054d6616..0e7112ddfd 100644
--- a/src/controllers/activitypub/index.js
+++ b/src/controllers/activitypub/index.js
@@ -31,7 +31,7 @@ Controller.fetch = async (req, res, next) => {
 		if (typeof result === 'string') {
 			return helpers.redirect(res, result);
 		} else if (result) {
-			const { id, type } = await activitypub.get('uid', req.uid || 0, url.href);
+			const { id, type } = await activitypub.get('uid', req.uid, url.href);
 			switch (true) {
 				case activitypub._constants.acceptedPostTypes.includes(type): {
 					return helpers.redirect(res, `/post/${encodeURIComponent(id)}`);