Redact password from DatabaseSessionService engine-creation errors

src/google/adk/sessions/database_session_service.py

@@ -71,6 +71,22 @@
 
 logger = logging.getLogger("google_adk." + __name__)
 
+
+def _redact_db_url(db_url: str) -> str:
+  """Returns the database URL with any embedded password removed.
+
+  The engine-creation error messages below include the database URL to aid
+  debugging, but a URL may embed credentials
+  (e.g. ``postgresql://user:password@host/db``). Rendering it with
+  ``hide_password=True`` keeps the useful parts (dialect, host, database) while
+  preventing the password from leaking into exceptions and logs.
+  """
+  try:
+    return make_url(db_url).render_as_string(hide_password=True)
+  except Exception:  # noqa: BLE001 - fall back to a fully redacted placeholder
+    return "[redacted]"
+
+
 _STALE_SESSION_ERROR_MESSAGE = (
     "The session has been modified in storage since it was loaded. "
     "Please reload the session before appending more events."
@@ -285,16 +301,17 @@ def __init__(
           event.listen(db_engine.sync_engine, "connect", _set_sqlite_pragma)
 
       except Exception as e:
+        safe_db_url = _redact_db_url(db_url)
         if isinstance(e, ArgumentError):
           raise ValueError(
-              f"Invalid database URL format or argument '{db_url}'."
+              f"Invalid database URL format or argument '{safe_db_url}'."
           ) from e
         if isinstance(e, ImportError):
           raise ValueError(
-              f"Database related module not found for URL '{db_url}'."
+              f"Database related module not found for URL '{safe_db_url}'."
           ) from e
         raise ValueError(
-            f"Failed to create database engine for URL '{db_url}'"
+            f"Failed to create database engine for URL '{safe_db_url}'"
         ) from e
     else:
       self._owns_db_engine = False

tests/unittests/sessions/test_session_service.py

@@ -38,6 +38,7 @@
 import pytest
 from sqlalchemy import delete
 from sqlalchemy import text
+from sqlalchemy.exc import ArgumentError
 from sqlalchemy.ext.asyncio import create_async_engine
 from sqlalchemy.pool import StaticPool
 
@@ -87,6 +88,52 @@ async def session_service(request, tmp_path):
     )
 
 
+_DB_URL_WITH_PASSWORD = (
+    'postgresql+psycopg2://db_user:sup3rs3cret@localhost:5432/prod'
+)
+_DB_PASSWORD = 'sup3rs3cret'
+
+
+def test_redact_db_url_masks_embedded_password():
+  redacted = database_session_service._redact_db_url(_DB_URL_WITH_PASSWORD)
+
+  assert _DB_PASSWORD not in redacted
+  # The non-sensitive parts stay available for debugging.
+  assert 'localhost' in redacted
+  assert 'prod' in redacted
+  assert 'db_user' in redacted
+
+
+def test_redact_db_url_falls_back_to_placeholder_for_unparsable_url():
+  assert database_session_service._redact_db_url('::not a url::') == '[redacted]'
+
+
+@pytest.mark.parametrize(
+    'raised_error',
+    [
+        ArgumentError('invalid url'),
+        ImportError('missing driver'),
+        RuntimeError('unexpected failure'),
+    ],
+)
+def test_database_session_service_init_error_does_not_leak_password(
+    raised_error,
+):
+  """Engine-creation failures must not surface the URL password."""
+  with mock.patch.object(
+      database_session_service,
+      'create_async_engine',
+      side_effect=raised_error,
+  ):
+    with pytest.raises(ValueError) as exc_info:
+      database_session_service.DatabaseSessionService(_DB_URL_WITH_PASSWORD)
+
+  message = str(exc_info.value)
+  assert _DB_PASSWORD not in message
+  # The redacted URL keeps the host so the error stays actionable.
+  assert 'localhost' in message
+
+
 def test_database_session_service_enables_pool_pre_ping_by_default():
   captured_kwargs = {}