From 2f883c6f63b0e7b4de21abe798d516b0e20e05e5 Mon Sep 17 00:00:00 2001
From: Jannis Braun <151788261+TheZwiss@users.noreply.github.com>
Date: Wed, 25 Mar 2026 01:48:18 +0100
Subject: [PATCH] refactor(server): extract SSRF validation into shared ssrf.ts
 utility

---
 packages/server/src/utils/metadataFetcher.ts | 38 +----------------
 packages/server/src/utils/ssrf.ts            | 45 ++++++++++++++++++++
 2 files changed, 47 insertions(+), 36 deletions(-)
 create mode 100644 packages/server/src/utils/ssrf.ts

diff --git a/packages/server/src/utils/metadataFetcher.ts b/packages/server/src/utils/metadataFetcher.ts
index 9eb1d5ed..e5562921 100644
--- a/packages/server/src/utils/metadataFetcher.ts
+++ b/packages/server/src/utils/metadataFetcher.ts
@@ -1,20 +1,5 @@
-import dns from 'dns';
 import * as cheerio from 'cheerio';
-
-export function isPrivateIp(ip: string): boolean {
-  // IPv4
-  if (ip.startsWith('127.') || ip.startsWith('0.') || ip === '0.0.0.0') return true;
-  if (ip.startsWith('10.')) return true;
-  if (ip.startsWith('192.168.')) return true;
-  if (ip.startsWith('169.254.')) return true;
-  if (ip.startsWith('172.')) {
-    const second = parseInt(ip.split('.')[1] ?? '', 10);
-    if (second >= 16 && second <= 31) return true;
-  }
-  // IPv6
-  if (ip === '::1' || ip.startsWith('fc') || ip.startsWith('fd') || ip.startsWith('fe80')) return true;
-  return false;
-}
+import { validateExternalUrl } from './ssrf.js';
 
 export interface UrlMetadata {
   title: string | null;
@@ -27,31 +12,12 @@ export interface UrlMetadata {
 }
 
 export async function fetchUrlMetadata(url: string): Promise<UrlMetadata | null> {
-  // Validate URL scheme
-  let parsed: URL;
   try {
-    parsed = new URL(url);
+    await validateExternalUrl(url);
   } catch {
     return null;
   }
 
-  if (!['http:', 'https:'].includes(parsed.protocol)) {
-    return null;
-  }
-
-  // Resolve hostname and block private/internal IPs
-  let address: string;
-  try {
-    const result = await dns.promises.lookup(parsed.hostname);
-    address = result.address;
-  } catch {
-    return null;
-  }
-
-  if (isPrivateIp(address)) {
-    return null;
-  }
-
   const controller = new AbortController();
   const timeout = setTimeout(() => controller.abort(), 5000);
   try {
diff --git a/packages/server/src/utils/ssrf.ts b/packages/server/src/utils/ssrf.ts
new file mode 100644
index 00000000..bbd097d7
--- /dev/null
+++ b/packages/server/src/utils/ssrf.ts
@@ -0,0 +1,45 @@
+import dns from 'dns';
+
+export function isPrivateIp(ip: string): boolean {
+  // IPv4
+  if (ip.startsWith('127.') || ip.startsWith('0.') || ip === '0.0.0.0') return true;
+  if (ip.startsWith('10.')) return true;
+  if (ip.startsWith('192.168.')) return true;
+  if (ip.startsWith('169.254.')) return true;
+  if (ip.startsWith('172.')) {
+    const second = parseInt(ip.split('.')[1] ?? '', 10);
+    if (second >= 16 && second <= 31) return true;
+  }
+  // IPv6
+  if (ip === '::1' || ip.startsWith('fc') || ip.startsWith('fd') || ip.startsWith('fe80')) return true;
+  return false;
+}
+
+/**
+ * Validate that a URL is safe for outbound fetch (not private/internal).
+ * Throws on invalid scheme, DNS failure, or private IP resolution.
+ */
+export async function validateExternalUrl(url: string): Promise<void> {
+  let parsed: URL;
+  try {
+    parsed = new URL(url);
+  } catch {
+    throw new Error('Invalid URL');
+  }
+
+  if (!['http:', 'https:'].includes(parsed.protocol)) {
+    throw new Error('Invalid URL scheme');
+  }
+
+  let address: string;
+  try {
+    const result = await dns.promises.lookup(parsed.hostname);
+    address = result.address;
+  } catch {
+    throw new Error('DNS lookup failed');
+  }
+
+  if (isPrivateIp(address)) {
+    throw new Error('Private IP not allowed');
+  }
+}