Redact server proxy upstream errors

node/server_proxy.py

@@ -6,7 +6,6 @@
 
 from flask import Flask, request, jsonify
 import requests
-import json
 from urllib.parse import quote
 
 app = Flask(__name__)
@@ -22,6 +21,23 @@ def _build_local_api_url(path):
     safe_path = "/".join(quote(part, safe="") for part in parts)
     return f"{LOCAL_SERVER}/api/{safe_path}"
 
+
+def _relay_upstream_response(response):
+    """Relay upstream responses without exposing internal 5xx details."""
+    if response.status_code >= 500:
+        app.logger.warning("Upstream server returned %s for proxied request", response.status_code)
+        return jsonify({'error': 'Upstream server error'}), 502
+
+    content_type = response.headers.get('Content-Type', '')
+    if 'application/json' in content_type:
+        try:
+            return jsonify(response.json()), response.status_code
+        except ValueError:
+            app.logger.warning("Upstream server returned invalid JSON with JSON content type")
+            return jsonify({'error': 'Invalid upstream JSON response'}), 502
+
+    return response.text, response.status_code
+
 @app.route('/api/<path:path>', methods=['GET', 'POST'])
 def proxy(path):
     """Forward all API requests to local server"""
@@ -43,23 +59,16 @@ def proxy(path):
             # Forward GET requests
             response = requests.get(url, timeout=10)
 
-        # Return the response from local server
-        # Safely handle non-JSON responses from upstream
-        content_type = response.headers.get('Content-Type', '')
-        if 'application/json' in content_type:
-            try:
-                return response.json(), response.status_code
-            except (ValueError, Exception):
-                # JSON parse failed, fall back to text
-                return response.text, response.status_code
-        else:
-            # Non-JSON response (e.g., HTML error page), return as-is with text
-            return response.text, response.status_code
+        return _relay_upstream_response(response)
 
     except requests.exceptions.Timeout:
         return jsonify({'error': 'Local server timeout'}), 504
-    except Exception as e:
-        return jsonify({'error': str(e)}), 500
+    except requests.exceptions.RequestException:
+        app.logger.warning("Local server request failed", exc_info=True)
+        return jsonify({'error': 'Local server unavailable'}), 502
+    except Exception:
+        app.logger.exception("Unexpected proxy error")
+        return jsonify({'error': 'Proxy error'}), 500
 
 @app.route('/status')
 def status():

node/tests/test_server_proxy_errors.py

@@ -0,0 +1,44 @@
+import sys
+import unittest
+from pathlib import Path
+from unittest.mock import Mock, patch
+
+NODE_DIR = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(NODE_DIR))
+
+import server_proxy
+
+
+class ServerProxyErrorTests(unittest.TestCase):
+    def setUp(self):
+        server_proxy.app.config["TESTING"] = True
+        self.client = server_proxy.app.test_client()
+
+    @patch("server_proxy.requests.get")
+    def test_proxy_exception_does_not_leak_message(self, mock_get):
+        mock_get.side_effect = RuntimeError("secret filesystem path")
+
+        response = self.client.get("/api/stats")
+
+        self.assertEqual(response.status_code, 500)
+        body = response.get_json()
+        self.assertEqual(body, {"error": "Proxy error"})
+        self.assertNotIn("secret filesystem path", response.get_data(as_text=True))
+
+    @patch("server_proxy.requests.get")
+    def test_upstream_500_body_is_redacted(self, mock_get):
+        upstream = Mock()
+        upstream.status_code = 500
+        upstream.headers = {"Content-Type": "text/plain"}
+        upstream.text = "Traceback: database password is hunter2"
+        mock_get.return_value = upstream
+
+        response = self.client.get("/api/stats")
+
+        self.assertEqual(response.status_code, 502)
+        self.assertEqual(response.get_json(), {"error": "Upstream server error"})
+        self.assertNotIn("hunter2", response.get_data(as_text=True))
+
+
+if __name__ == "__main__":
+    unittest.main()