🛡️ Sentinel: [HIGH] Fix SSRF protection to explicitly block link-local IPs

.jules/sentinel.md

@@ -2,3 +2,8 @@
 **Vulnerability:** The `_is_safe_ip` function relied primarily on `is_private` and `is_global` properties of Python's `ipaddress` module to prevent SSRF loopback connections. While these often cover `127.0.0.1` and `::1`, edge cases and alternative loopback addresses may bypass these checks depending on OS/network configurations.
 **Learning:** Defense-in-depth is essential when validating IPs. Relying solely on `is_private` or `is_global` without explicitly checking `is_loopback` creates potential edge cases where loopback traffic might not be caught, increasing SSRF risk.
 **Prevention:** Explicitly check for `is_loopback` along with `is_unspecified` and `is_private` to ensure comprehensive outbound SSRF filtering.
+
+## 2025-04-07 - Add explicit link-local IP check to prevent SSRF bypass
+**Vulnerability:** The `_is_safe_ip` function lacked an explicit check for link-local addresses (like `169.254.169.254`, commonly used for cloud metadata services), implicitly relying on `is_global` or `is_private`.
+**Learning:** OS-specific network stacks might unexpectedly route link-local addresses or fail to properly classify them as non-global or private. This could allow attackers to bypass SSRF protections and access sensitive internal metadata endpoints.
+**Prevention:** Defense-in-depth requires explicitly blocking `ip.is_link_local` alongside `is_loopback`, `is_unspecified`, and `is_private` to ensure complete outbound SSRF filtering.

main.py

@@ -1075,6 +1075,8 @@ def _is_safe_ip(ip: ipaddress.IPv4Address | ipaddress.IPv6Address) -> bool:
         return False
     if ip.is_loopback:
         return False
+    if ip.is_link_local:
+        return False
     if isinstance(ip, ipaddress.IPv6Address) and ip.ipv4_mapped:
         return _is_safe_ip(ip.ipv4_mapped)
     if isinstance(ip, ipaddress.IPv4Address) and ip in _CGNAT_NETWORK:

tests/test_ssrf_link_local.py

@@ -0,0 +1,28 @@
+import os
+import socket
+import sys
+import unittest
+from unittest.mock import patch
+
+# Add root to path to import main
+sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+import main
+
+class TestSSRFLinkLocal(unittest.TestCase):
+    def test_domain_resolving_to_link_local_ip(self):
+        """
+        Test that a domain resolving to a link-local IP (169.254.169.254) is blocked.
+        """
+        with patch("socket.getaddrinfo") as mock_getaddrinfo:
+            # Simulate resolving to AWS metadata service IP
+            mock_getaddrinfo.return_value = [
+                (socket.AF_INET, socket.SOCK_STREAM, 6, "", ("169.254.169.254", 443))
+            ]
+
+            url = "https://metadata.example.com/config.json"
+            result = main.validate_folder_url(url)
+            self.assertFalse(result, "Should block domain resolving to link-local IP")
+
+if __name__ == "__main__":
+    unittest.main()