fix(environment): add integer validation in ReadFileTool

Add runtime integer type validation for start_line and end_line arguments (including boolean exclusion) to prevent slice type errors and ensure safe execution.

Co-authored-by: Liang Wu <wuliang@google.com>
PiperOrigin-RevId: 945188902

Author: wuliang229

src/google/adk/tools/environment/_read_file_tool.py

@@ -37,6 +37,11 @@
 logger = logging.getLogger('google_adk.' + __name__)
 
 
+def _is_valid_line_number(value: Any) -> bool:
+  """Returns True when *value* is a non-bool integer."""
+  return isinstance(value, int) and not isinstance(value, bool)
+
+
 @experimental
 class ReadFileTool(BaseTool):
   """Read a file from the environment."""
@@ -101,6 +106,12 @@ async def run_async(
       return {'status': 'error', 'error': '`path` is required.'}
     start_line = args.get('start_line')
     end_line = args.get('end_line')
+    for name, value in (('start_line', start_line), ('end_line', end_line)):
+      if value is not None and not _is_valid_line_number(value):
+        return {
+            'status': 'error',
+            'error': f'`{name}` must be an integer if provided.',
+        }
 
     try:
       # TODO: Avoid loading the entire file into memory to prevent OOM on large files.

tests/unittests/tools/environment/test_read_file_tool.py

@@ -12,13 +12,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+"""Tests for ReadFileTool."""
+
 from pathlib import Path
 from typing import Optional
 
 from google.adk.environment._base_environment import BaseEnvironment
 from google.adk.environment._base_environment import ExecutionResult
-from google.adk.tools.environment._tools import ReadFileTool
+from google.adk.environment._local_environment import LocalEnvironment
+from google.adk.tools.environment._read_file_tool import ReadFileTool
 import pytest
+import pytest_asyncio
 
 
 class _StubEnvironment(BaseEnvironment):
@@ -94,3 +98,99 @@ async def test_read_file_with_line_range_treats_shell_payload_as_literal_path():
       'error': f'File not found: {payload}',
   }
   assert environment.execute_calls == []
+
+
+@pytest_asyncio.fixture(name='env')
+async def _env(tmp_path: Path):
+  """Create and initialize a LocalEnvironment backed by a temp directory."""
+  environment = LocalEnvironment(working_dir=tmp_path)
+  await environment.initialize()
+  yield environment
+  await environment.close()
+
+
+class TestReadFileTool:
+  """Tests for ReadFileTool behavior."""
+
+  @pytest.mark.asyncio
+  async def test_read_file_with_line_range_returns_selected_lines(
+      self, env: LocalEnvironment
+  ):
+    """Reads the requested line range and preserves line numbers."""
+    await env.write_file('sample.txt', 'line1\nline2\nline3\n')
+
+    tool = ReadFileTool(env)
+    result = await tool.run_async(
+        args={'path': 'sample.txt', 'start_line': 2, 'end_line': 3},
+        tool_context=None,
+    )
+
+    assert result == {
+        'status': 'ok',
+        'content': '     2\tline2\n     3\tline3\n',
+        'total_lines': 3,
+    }
+
+  @pytest.mark.asyncio
+  async def test_read_file_with_line_range_missing_file_returns_error(
+      self, env: LocalEnvironment
+  ):
+    """Returns a missing-file error for ranged reads."""
+    tool = ReadFileTool(env)
+
+    result = await tool.run_async(
+        args={'path': 'missing.txt', 'start_line': 2},
+        tool_context=None,
+    )
+
+    assert result == {
+        'status': 'error',
+        'error': 'File not found: missing.txt',
+    }
+
+  @pytest.mark.asyncio
+  async def test_read_file_rejects_non_integer_end_line(
+      self, env: LocalEnvironment
+  ):
+    """Rejects non-integer line numbers without executing shell syntax."""
+    await env.write_file('sample.txt', 'line1\nline2\n')
+    marker = env.working_dir / 'marker.txt'
+    injected_end_line = f"1'; touch {marker}; echo '"
+
+    tool = ReadFileTool(env)
+    result = await tool.run_async(
+        args={'path': 'sample.txt', 'end_line': injected_end_line},
+        tool_context=None,
+    )
+
+    assert result == {
+        'status': 'error',
+        'error': '`end_line` must be an integer if provided.',
+    }
+    assert not marker.exists()
+
+  @pytest.mark.asyncio
+  async def test_read_file_rejects_boolean_line_numbers(
+      self, env: LocalEnvironment
+  ):
+    """Rejects boolean values for start_line and end_line."""
+    await env.write_file('sample.txt', 'line1\nline2\n')
+
+    tool = ReadFileTool(env)
+    res_start = await tool.run_async(
+        args={'path': 'sample.txt', 'start_line': True},
+        tool_context=None,
+    )
+    res_end = await tool.run_async(
+        args={'path': 'sample.txt', 'end_line': False},
+        tool_context=None,
+    )
+
+    assert res_start == {
+        'status': 'error',
+        'error': '`start_line` must be an integer if provided.',
+    }
+    assert res_end == {
+        'status': 'error',
+        'error': '`end_line` must be an integer if provided.',
+    }