feat: add mitm_launcher.py and explicit scan_failed degradation in addon

- addon.py: split except block into specific httpx network errors
  (ConnectError, TimeoutException, HTTPStatusError) and generic Exception;
  both now log action="scan_failed" instead of "allow", and redact mode
  calls flow.kill() to block the upload when info-privacy is unreachable
- mitm_launcher.py: programmatic DumpMaster entry point for PyInstaller,
  replaces `mitmdump -s addon.py` file-load so all source compiles to binary
- tests/test_addon_degradation.py: 8 parametrized tests covering audit/redact
  degradation with ConnectError, TimeoutException, HTTPStatusError, and
  _audit=None edge cases

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/privacy_gateway/addon.py

@@ -132,14 +132,33 @@ class PrivacyGatewayAddon:
         for f in files:
             try:
                 result = await scan_and_redact(f.filename, f.data)
-            except Exception as e:
-                ctx.log.warn(f"[privacy-gw] scan failed {f.filename}: {e}")
+            except (httpx.ConnectError, httpx.TimeoutException, httpx.HTTPStatusError) as e:
+                logger.warning("[privacy-gw] info-privacy unreachable for %s: %s", f.filename, e)
+                ctx.log.warn(f"[privacy-gw] scan_failed {f.filename}: {e}")
                 if _audit is not None:
                     _audit.log(
-                        host, {}, "allow", f.data, total_files,
+                        host, {}, "scan_failed", f.data, total_files,
                         client_ip=client_ip, request_url=request_url,
                         filename=f.filename, file_size=len(f.data),
                     )
+                if mode == "redact":
+                    # Block upload when info-privacy is unavailable in redact mode
+                    flow.kill()
+                    return
+                # audit or off mode: allow through with scan_failed logged
+                continue
+            except Exception as e:
+                logger.warning("[privacy-gw] unexpected scan error for %s: %s", f.filename, e)
+                ctx.log.warn(f"[privacy-gw] scan error {f.filename}: {e}")
+                if _audit is not None:
+                    _audit.log(
+                        host, {}, "scan_failed", f.data, total_files,
+                        client_ip=client_ip, request_url=request_url,
+                        filename=f.filename, file_size=len(f.data),
+                    )
+                if mode == "redact":
+                    flow.kill()
+                    return
                 continue
 
             if mode == "audit":

services/privacy_gateway/mitm_launcher.py

@@ -0,0 +1,38 @@
+"""Programmatic mitmproxy entry point for PyInstaller compilation.
+
+Replaces `mitmdump -s addon.py` file-load so all source is compiled into binary.
+Usage:
+    python -m privacy_gateway.mitm_launcher
+    # or after PyInstaller packaging:
+    ./kvm-mitm
+"""
+from __future__ import annotations
+
+import asyncio
+import signal
+
+from mitmproxy import options
+from mitmproxy.tools.dump import DumpMaster
+
+from privacy_gateway.addon import PrivacyGatewayAddon
+
+
+async def main() -> None:
+    opts = options.Options(
+        listen_host="0.0.0.0",
+        listen_port=8888,
+        mode=["regular"],
+        ssl_insecure=True,
+    )
+    master = DumpMaster(opts, with_termlog=False, with_dumper=False)
+    master.addons.add(PrivacyGatewayAddon())
+
+    loop = asyncio.get_event_loop()
+    for sig in (signal.SIGINT, signal.SIGTERM):
+        loop.add_signal_handler(sig, master.shutdown)
+
+    await master.run()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

services/privacy_gateway/tests/test_addon_degradation.py

@@ -0,0 +1,128 @@
+"""Test that addon handles info-privacy being down gracefully (scan_failed degradation).
+
+When scan_and_redact raises a network error:
+- audit mode : audit log called with action="scan_failed", request allowed through
+- redact mode: audit log called with action="scan_failed", flow killed/blocked
+"""
+import asyncio
+import pytest
+from unittest.mock import MagicMock, patch, AsyncMock
+
+import httpx
+
+import services.privacy_gateway.addon as _addon_mod
+
+
+def _make_mock_flow(ip="127.0.0.1"):
+    flow = MagicMock()
+    flow.client_conn.peername = (ip, 9999)
+    flow.request.url = "https://api.openai.com/v1/files"
+    flow.request.content = b"original"
+    return flow
+
+
+def _make_mock_file(filename="secret.pdf", data=b"bytes"):
+    f = MagicMock()
+    f.filename = filename
+    f.data = data
+    f.field_name = "file"
+    return f
+
+
+# ---------------------------------------------------------------------------
+# Helper: build ScanError exceptions that map to httpx network failures
+# ---------------------------------------------------------------------------
+
+_NETWORK_ERRORS = [
+    httpx.ConnectError("Connection refused"),
+    httpx.TimeoutException("Timeout"),
+    httpx.HTTPStatusError("503", request=MagicMock(), response=MagicMock()),
+]
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("exc", _NETWORK_ERRORS)
+async def test_audit_mode_scan_failed_logs_and_allows(exc):
+    """In audit mode, scan failure → action='scan_failed', request NOT blocked."""
+    mock_audit = MagicMock()
+
+    with patch.object(_addon_mod, "_audit", mock_audit), \
+         patch.object(_addon_mod, "scan_and_redact", AsyncMock(side_effect=exc)), \
+         patch.object(_addon_mod, "ctx", MagicMock()):
+
+        addon = _addon_mod.PrivacyGatewayAddon()
+        flow = _make_mock_flow()
+        mock_file = _make_mock_file()
+
+        await addon._process_upload(flow, "api.openai.com", [mock_file], "audit")
+
+        # Must log with action="scan_failed" (not "allow")
+        mock_audit.log.assert_called_once()
+        call_args = mock_audit.log.call_args
+        # positional: domain, pii_types, action, raw_bytes?, file_count?
+        action = call_args[0][2] if len(call_args[0]) > 2 else call_args[1].get("action")
+        assert action == "scan_failed", (
+            f"Expected action='scan_failed' in audit mode, got '{action}'"
+        )
+        # Request must NOT be blocked/killed
+        flow.kill.assert_not_called()
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("exc", _NETWORK_ERRORS)
+async def test_redact_mode_scan_failed_blocks_request(exc):
+    """In redact mode, scan failure → action='scan_failed', flow.kill() called."""
+    mock_audit = MagicMock()
+
+    with patch.object(_addon_mod, "_audit", mock_audit), \
+         patch.object(_addon_mod, "scan_and_redact", AsyncMock(side_effect=exc)), \
+         patch.object(_addon_mod, "ctx", MagicMock()):
+
+        addon = _addon_mod.PrivacyGatewayAddon()
+        flow = _make_mock_flow()
+        mock_file = _make_mock_file()
+
+        await addon._process_upload(flow, "api.openai.com", [mock_file], "redact")
+
+        # Must log with action="scan_failed"
+        mock_audit.log.assert_called_once()
+        call_args = mock_audit.log.call_args
+        action = call_args[0][2] if len(call_args[0]) > 2 else call_args[1].get("action")
+        assert action == "scan_failed", (
+            f"Expected action='scan_failed' in redact mode, got '{action}'"
+        )
+        # Request MUST be blocked
+        flow.kill.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_audit_mode_scan_failed_no_audit_object():
+    """If _audit is None, scan failure in audit mode should not raise."""
+    with patch.object(_addon_mod, "_audit", None), \
+         patch.object(_addon_mod, "scan_and_redact", AsyncMock(
+             side_effect=httpx.ConnectError("down"))), \
+         patch.object(_addon_mod, "ctx", MagicMock()):
+
+        addon = _addon_mod.PrivacyGatewayAddon()
+        flow = _make_mock_flow()
+        mock_file = _make_mock_file()
+
+        # Must not raise even if _audit is None
+        await addon._process_upload(flow, "api.openai.com", [mock_file], "audit")
+        flow.kill.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_redact_mode_scan_failed_no_audit_object():
+    """If _audit is None, scan failure in redact mode should still kill the flow."""
+    with patch.object(_addon_mod, "_audit", None), \
+         patch.object(_addon_mod, "scan_and_redact", AsyncMock(
+             side_effect=httpx.ConnectError("down"))), \
+         patch.object(_addon_mod, "ctx", MagicMock()):
+
+        addon = _addon_mod.PrivacyGatewayAddon()
+        flow = _make_mock_flow()
+        mock_file = _make_mock_file()
+
+        await addon._process_upload(flow, "api.openai.com", [mock_file], "redact")
+        flow.kill.assert_called_once()