fix(image): delegate DNS to explicit proxy

tests/providers/test_image_generation_security.py

@@ -139,13 +139,13 @@ class _StreamContext:
 
 
 @pytest.mark.asyncio
-async def test_generated_image_download_uses_explicit_provider_proxy(
+async def test_generated_image_download_delegates_unresolved_host_to_provider_proxy(
     monkeypatch,
 ) -> None:
-    monkeypatch.setattr(
-        "nanobot.security.network.socket.getaddrinfo",
-        _resolve_public,
-    )
+    def fail_local_dns(host: str, port: int | None, *args, **kwargs):
+        raise socket.gaierror(f"cannot resolve {host}")
+
+    monkeypatch.setattr("nanobot.security.network.socket.getaddrinfo", fail_local_dns)
     captured: dict[str, object] = {}
 
     class FakeAsyncClient:
@@ -167,12 +167,12 @@ async def test_generated_image_download_uses_explicit_provider_proxy(
     proxy = "http://127.0.0.1:23458"
 
     result = await _download_image_data_url(
-        "https://cdn.example/image.png",
+        "https://proxy-only.example/image.png",
         proxy=proxy,
     )
 
     assert result.startswith("data:image/png;base64,")
-    assert captured["request"] == ("GET", "https://cdn.example/image.png")
+    assert captured["request"] == ("GET", "https://proxy-only.example/image.png")
     assert captured["kwargs"] == {
         "follow_redirects": False,
         "timeout": image_generation._DEFAULT_TIMEOUT_S,

tests/security/test_security_network.py

@@ -195,6 +195,47 @@ def test_resolve_url_target_returns_validated_public_ips():
     assert resolved_ips == ("93.184.216.34",)
 
 
+@pytest.mark.parametrize(
+    ("trust_remote_dns", "expected_ok"),
+    [(False, False), (True, True)],
+)
+def test_resolve_url_target_only_delegates_dns_to_trusted_proxy(
+    trust_remote_dns: bool,
+    expected_ok: bool,
+):
+    with patch(
+        "nanobot.security.network.socket.getaddrinfo",
+        side_effect=socket.gaierror("local DNS unavailable"),
+    ):
+        ok, err, resolved_ips = resolve_url_target(
+            "https://proxy-only.example/image.png",
+            trust_remote_dns=trust_remote_dns,
+        )
+
+    assert ok is expected_ok, err
+    assert resolved_ips == ()
+
+
+@pytest.mark.parametrize(
+    "url",
+    [
+        "http://localhost/secret",
+        "http://service.localhost/secret",
+        "http://127.0.0.1/secret",
+        "http://169.254.169.254/latest",
+        "http://[::1]/secret",
+    ],
+)
+def test_resolve_url_target_does_not_delegate_local_targets(url: str):
+    with patch(
+        "nanobot.security.network.socket.getaddrinfo",
+        side_effect=socket.gaierror("local DNS unavailable"),
+    ):
+        ok, _, _ = resolve_url_target(url, trust_remote_dns=True)
+
+    assert not ok
+
+
 def test_pin_resolved_url_dns_prevents_second_resolution_rebind():
     def _rebinding_resolver(hostname, port, family=0, type_=0):
         return [(socket.AF_INET, socket.SOCK_STREAM, 0, "", ("169.254.169.254", 0))]