fix: validate local eval path segments

Merge https://github.com/google/adk-python/pull/5993

## Summary
- add shared validation for local eval filesystem path segments
- reject empty, traversal, separator, and null-byte identifiers before path construction
- cover local eval set and eval result managers with regression tests

## Issue Association
No public GitHub issue. This hardens local eval storage path handling for caller-controlled identifiers.

## Testing Plan
- env UV_CACHE_DIR=/tmp/uv-cache uv run --extra test pytest tests/unittests/evaluation/test_local_eval_sets_manager.py tests/unittests/evaluation/test_local_eval_set_results_manager.py

Co-authored-by: George Weale <gweale@google.com>
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/5993 from bg0d-droid:bg0d/validate-eval-path-segments 8f3f363b1686190ae5a7ecf1937cea01eaad1aee
PiperOrigin-RevId: 938260846

src/google/adk/evaluation/_path_validation.py

@@ -0,0 +1,40 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+
+def validate_path_segment(value: str, field_name: str) -> None:
+  """Rejects values that could alter a filesystem path.
+
+  Args:
+    value: The caller-supplied identifier.
+    field_name: Human-readable field name used in error messages.
+
+  Raises:
+    ValueError: If the value contains path separators, traversal segments, or
+      null bytes.
+  """
+  if not value:
+    raise ValueError(f"{field_name} must not be empty.")
+  if "\x00" in value:
+    raise ValueError(f"{field_name} must not contain null bytes.")
+  if "/" in value or "\\" in value:
+    raise ValueError(
+        f"{field_name} {value!r} must not contain path separators."
+    )
+  if value in (".", ".."):
+    raise ValueError(
+        f"{field_name} {value!r} must not contain traversal segments."
+    )

src/google/adk/evaluation/local_eval_set_results_manager.py

@@ -22,6 +22,7 @@ from typing_extensions import override
 from ..errors.not_found_error import NotFoundError
 from ._eval_set_results_manager_utils import create_eval_set_result
 from ._eval_set_results_manager_utils import parse_eval_set_result_json
+from ._path_validation import validate_path_segment
 from .eval_result import EvalCaseResult
 from .eval_result import EvalSetResult
 from .eval_set_results_manager import EvalSetResultsManager
@@ -46,6 +47,8 @@ class LocalEvalSetResultsManager(EvalSetResultsManager):
       eval_case_results: list[EvalCaseResult],
   ) -> None:
     """Creates and saves a new EvalSetResult given eval_case_results."""
+    validate_path_segment(app_name, "app_name")
+    validate_path_segment(eval_set_id, "eval_set_id")
     eval_set_result = create_eval_set_result(
         app_name, eval_set_id, eval_case_results
     )
@@ -67,6 +70,7 @@ class LocalEvalSetResultsManager(EvalSetResultsManager):
       self, app_name: str, eval_set_result_id: str
   ) -> EvalSetResult:
     """Returns an EvalSetResult identified by app_name and eval_set_result_id."""
+    validate_path_segment(eval_set_result_id, "eval_set_result_id")
     # Load the eval set result file data.
     maybe_eval_result_file_path = (
         os.path.join(
@@ -97,4 +101,5 @@ class LocalEvalSetResultsManager(EvalSetResultsManager):
     return eval_result_files
 
   def _get_eval_history_dir(self, app_name: str) -> str:
+    validate_path_segment(app_name, "app_name")
     return os.path.join(self._agents_dir, app_name, _ADK_EVAL_HISTORY_DIR)

src/google/adk/evaluation/local_eval_sets_manager.py

@@ -33,6 +33,7 @@ from ._eval_sets_manager_utils import delete_eval_case_from_eval_set
 from ._eval_sets_manager_utils import get_eval_case_from_eval_set
 from ._eval_sets_manager_utils import get_eval_set_from_app_and_id
 from ._eval_sets_manager_utils import update_eval_case_in_eval_set
+from ._path_validation import validate_path_segment
 from .eval_case import EvalCase
 from .eval_case import IntermediateData
 from .eval_case import Invocation
@@ -247,6 +248,7 @@ class LocalEvalSetsManager(EvalSetsManager):
     Raises:
       NotFoundError: If the eval directory for the app is not found.
     """
+    validate_path_segment(app_name, "app_name")
     eval_set_file_path = os.path.join(self._agents_dir, app_name)
     eval_sets = []
     try:
@@ -310,6 +312,8 @@ class LocalEvalSetsManager(EvalSetsManager):
     self._save_eval_set(app_name, eval_set_id, updated_eval_set)
 
   def _get_eval_set_file_path(self, app_name: str, eval_set_id: str) -> str:
+    validate_path_segment(app_name, "app_name")
+    validate_path_segment(eval_set_id, "eval_set_id")
     return os.path.join(
         self._agents_dir,
         app_name,

tests/unittests/evaluation/test__path_validation.py

@@ -0,0 +1,52 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from google.adk.evaluation._path_validation import validate_path_segment
+import pytest
+
+
+@pytest.mark.parametrize(
+    "value", ["eval_set_1", "my-app", "App Name 1", "résumé", "a.b.c"]
+)
+def test_validate_path_segment_accepts_valid_value(value):
+  validate_path_segment(value, "field")
+
+
+def test_validate_path_segment_rejects_empty():
+  with pytest.raises(ValueError, match="must not be empty"):
+    validate_path_segment("", "field")
+
+
+def test_validate_path_segment_rejects_null_byte():
+  with pytest.raises(ValueError, match="must not contain null bytes"):
+    validate_path_segment("foo\x00bar", "field")
+
+
+@pytest.mark.parametrize("value", ["foo/bar", "foo\\bar", "/", "\\"])
+def test_validate_path_segment_rejects_path_separators(value):
+  with pytest.raises(ValueError, match="must not contain path separators"):
+    validate_path_segment(value, "field")
+
+
+@pytest.mark.parametrize("value", [".", ".."])
+def test_validate_path_segment_rejects_traversal_segments(value):
+  with pytest.raises(ValueError, match="must not contain traversal segments"):
+    validate_path_segment(value, "field")
+
+
+def test_validate_path_segment_includes_field_name_in_error():
+  with pytest.raises(ValueError, match="eval_set_id"):
+    validate_path_segment("", "eval_set_id")

tests/unittests/evaluation/test_local_eval_set_results_manager.py

@@ -92,6 +92,22 @@ class TestLocalEvalSetResultsManager:
     expected_eval_set_result_data = self.eval_set_result.model_dump(mode="json")
     assert expected_eval_set_result_data == actual_eval_set_result_data
 
+  @pytest.mark.parametrize("app_name", ["", ".", "..", "foo/bar", "foo\\bar"])
+  def test_save_eval_set_result_rejects_invalid_app_name(self, app_name):
+    with pytest.raises(ValueError):
+      self.manager.save_eval_set_result(
+          app_name, self.eval_set_id, self.eval_case_results
+      )
+
+  @pytest.mark.parametrize(
+      "eval_set_id", ["", ".", "..", "foo/bar", "foo\\bar"]
+  )
+  def test_save_eval_set_result_rejects_invalid_eval_set_id(self, eval_set_id):
+    with pytest.raises(ValueError):
+      self.manager.save_eval_set_result(
+          self.app_name, eval_set_id, self.eval_case_results
+      )
+
   def test_get_eval_set_result(self, mocker):
     mock_time = mocker.patch("time.time")
     mock_time.return_value = self.timestamp
@@ -103,6 +119,20 @@ class TestLocalEvalSetResultsManager:
     )
     assert retrieved_result == self.eval_set_result
 
+  @pytest.mark.parametrize("app_name", ["", ".", "..", "foo/bar", "foo\\bar"])
+  def test_get_eval_set_result_rejects_invalid_app_name(self, app_name):
+    with pytest.raises(ValueError):
+      self.manager.get_eval_set_result(app_name, self.eval_set_result_name)
+
+  @pytest.mark.parametrize(
+      "eval_set_result_id", ["", ".", "..", "foo/bar", "foo\\bar"]
+  )
+  def test_get_eval_set_result_rejects_invalid_eval_set_result_id(
+      self, eval_set_result_id
+  ):
+    with pytest.raises(ValueError):
+      self.manager.get_eval_set_result(self.app_name, eval_set_result_id)
+
   def test_get_eval_set_result_double_encoded_legacy(self):
     eval_history_dir = os.path.join(
         self.agents_dir, self.app_name, _ADK_EVAL_HISTORY_DIR

tests/unittests/evaluation/test_local_eval_sets_manager.py

@@ -395,6 +395,29 @@ class TestLocalEvalSetsManager:
     with pytest.raises(ValueError, match="Invalid Eval Set ID"):
       local_eval_sets_manager.create_eval_set(app_name, eval_set_id)
 
+  @pytest.mark.parametrize("app_name", ["", ".", "..", "foo/bar", "foo\\bar"])
+  def test_local_eval_sets_manager_create_eval_set_rejects_invalid_app_name(
+      self, local_eval_sets_manager, app_name
+  ):
+    with pytest.raises(ValueError):
+      local_eval_sets_manager.create_eval_set(app_name, "test_eval_set")
+
+  @pytest.mark.parametrize("app_name", ["", ".", "..", "foo/bar", "foo\\bar"])
+  def test_local_eval_sets_manager_list_eval_sets_rejects_invalid_app_name(
+      self, local_eval_sets_manager, app_name
+  ):
+    with pytest.raises(ValueError):
+      local_eval_sets_manager.list_eval_sets(app_name)
+
+  @pytest.mark.parametrize(
+      "eval_set_id", ["", ".", "..", "foo/bar", "foo\\bar"]
+  )
+  def test_local_eval_sets_manager_get_eval_set_rejects_invalid_eval_set_id(
+      self, local_eval_sets_manager, eval_set_id
+  ):
+    with pytest.raises(ValueError):
+      local_eval_sets_manager.get_eval_set("test_app", eval_set_id)
+
   def test_local_eval_sets_manager_create_eval_set_already_exists(
       self, local_eval_sets_manager, mocker
   ):