fix: allow trusted QQ CDN benchmark IP resolution

tests/tools/test_url_safety.py

@@ -152,6 +152,34 @@ class TestIsSafeUrl:
             # 100.0.0.1 is a global IP, not in CGNAT range
             assert is_safe_url("http://legit-host.example/") is True
 
+    def test_benchmark_ip_blocked_for_non_allowlisted_host(self):
+        with patch("socket.getaddrinfo", return_value=[
+            (2, 1, 6, "", ("198.18.0.23", 0)),
+        ]):
+            assert is_safe_url("https://example.com/file.jpg") is False
+
+    def test_qq_multimedia_hostname_allowed_with_benchmark_ip(self):
+        with patch("socket.getaddrinfo", return_value=[
+            (2, 1, 6, "", ("198.18.0.23", 0)),
+        ]):
+            assert is_safe_url("https://multimedia.nt.qq.com.cn/download?id=123") is True
+
+    def test_qq_multimedia_hostname_exception_is_exact_match(self):
+        with patch("socket.getaddrinfo", return_value=[
+            (2, 1, 6, "", ("198.18.0.23", 0)),
+        ]):
+            assert is_safe_url("https://sub.multimedia.nt.qq.com.cn/download?id=123") is False
+
+    def test_qq_multimedia_hostname_exception_requires_https(self):
+        with patch("socket.getaddrinfo", return_value=[
+            (2, 1, 6, "", ("198.18.0.23", 0)),
+        ]):
+            assert is_safe_url("http://multimedia.nt.qq.com.cn/download?id=123") is False
+
+    def test_qq_multimedia_hostname_dns_failure_still_blocked(self):
+        with patch("socket.getaddrinfo", side_effect=socket.gaierror("Name resolution failed")):
+            assert is_safe_url("https://multimedia.nt.qq.com.cn/download?id=123") is False
+
 
 class TestIsBlockedIp:
     """Direct tests for the _is_blocked_ip helper."""
@@ -159,7 +187,7 @@ class TestIsBlockedIp:
     @pytest.mark.parametrize("ip_str", [
         "127.0.0.1", "10.0.0.1", "172.16.0.1", "192.168.1.1",
         "169.254.169.254", "0.0.0.0", "224.0.0.1", "255.255.255.255",
-        "100.64.0.1", "100.100.100.100", "100.127.255.254",
+        "100.64.0.1", "100.100.100.100", "100.127.255.254", "198.18.0.23",
         "::1", "fe80::1", "fc00::1", "fd12::1", "ff02::1",
         "::ffff:127.0.0.1", "::ffff:169.254.169.254",
     ])

tools/url_safety.py

@@ -29,6 +29,13 @@ _BLOCKED_HOSTNAMES = frozenset({
     "metadata.goog",
 })
 
+# Exact HTTPS hostnames allowed to resolve to private/benchmark-space IPs.
+# This is intentionally narrow: QQ media downloads can legitimately resolve
+# to 198.18.0.0/15 behind local proxy/benchmark infrastructure.
+_TRUSTED_PRIVATE_IP_HOSTS = frozenset({
+    "multimedia.nt.qq.com.cn",
+})
+
 # 100.64.0.0/10 (CGNAT / Shared Address Space, RFC 6598) is NOT covered by
 # ipaddress.is_private — it returns False for both is_private and is_global.
 # Must be blocked explicitly. Used by carrier-grade NAT, Tailscale/WireGuard
@@ -48,6 +55,11 @@ def _is_blocked_ip(ip: ipaddress.IPv4Address | ipaddress.IPv6Address) -> bool:
     return False
 
 
+def _allows_private_ip_resolution(hostname: str, scheme: str) -> bool:
+    """Return True when a trusted HTTPS hostname may bypass IP-class blocking."""
+    return scheme == "https" and hostname in _TRUSTED_PRIVATE_IP_HOSTS
+
+
 def is_safe_url(url: str) -> bool:
     """Return True if the URL target is not a private/internal address.
 
@@ -56,7 +68,8 @@ def is_safe_url(url: str) -> bool:
     """
     try:
         parsed = urlparse(url)
-        hostname = (parsed.hostname or "").strip().lower()
+        hostname = (parsed.hostname or "").strip().lower().rstrip(".")
+        scheme = (parsed.scheme or "").strip().lower()
         if not hostname:
             return False
 
@@ -65,6 +78,8 @@ def is_safe_url(url: str) -> bool:
             logger.warning("Blocked request to internal hostname: %s", hostname)
             return False
 
+        allow_private_ip = _allows_private_ip_resolution(hostname, scheme)
+
         # Try to resolve and check IP
         try:
             addr_info = socket.getaddrinfo(hostname, None, socket.AF_UNSPEC, socket.SOCK_STREAM)
@@ -81,13 +96,19 @@ def is_safe_url(url: str) -> bool:
             except ValueError:
                 continue
 
-            if _is_blocked_ip(ip):
+            if not allow_private_ip and _is_blocked_ip(ip):
                 logger.warning(
                     "Blocked request to private/internal address: %s -> %s",
                     hostname, ip_str,
                 )
                 return False
 
+        if allow_private_ip:
+            logger.debug(
+                "Allowing trusted hostname despite private/internal resolution: %s",
+                hostname,
+            )
+
         return True
 
     except Exception as exc: