Add authentication and input validation to TaskLogHandler

The TaskLogHandler endpoint at /testcase-detail/task-log was missing
authentication and authorization checks, unlike every other handler in
the same file that accesses testcase data. This change:

1. Adds access.check_access_and_get_testcase() to verify the caller
   is authenticated and authorized to view the testcase before querying
   Cloud Logging.

2. Validates task_name against the known set of valid task names to
   prevent Cloud Logging filter injection via crafted query parameters.

3. Adds _sanitize_filter_value() to escape double quotes and backslashes
   in user-supplied values before interpolating them into the Cloud
   Logging filter string, as defense-in-depth against filter injection.

4. Adds unit tests for the sanitization function and task name validation.

Author: petrmarinec

src/appengine/handlers/testcase_detail/show.py

@@ -640,9 +640,21 @@ class TaskLogHandler(base_handler.Handler):
   @handler.get(handler.TEXT)
   def get(self):
     """Serve the task log."""
+    testcase_id = flask.request.args.get('testcase_id')
+
+    # Verify the user is authenticated and has access to this testcase.
+    testcase = access.check_access_and_get_testcase(testcase_id)
+
     task_id = flask.request.args.get('task_id')
     task_name = flask.request.args.get('task_name')
-    testcase_id = flask.request.args.get('testcase_id')
+
+    # Validate task_name against the known set to prevent filter injection.
+    valid_task_names = (
+        testcase_status_events.TestcaseStatusInfo.TASK_EVENTS_NAMES +
+        testcase_status_events.TestcaseStatusInfo.CHROME_TASK_EVENTS_NAMES)
+    if task_name and task_name not in valid_task_names:
+      raise helpers.EarlyExitError('Invalid task name.', 400)
+
     log_content = testcase_status_events.get_task_log(testcase_id, task_id,
                                                       task_name)
 

src/appengine/handlers/testcase_detail/testcase_status_events.py

@@ -219,11 +219,21 @@ def _get_time_range_filter(self, days: int) -> str:
     start_time = utils.utcnow() - datetime.timedelta(days=days)
     return f'timestamp >= "{start_time.isoformat()}Z"'
 
+  @staticmethod
+  def _sanitize_filter_value(value: str) -> str:
+    """Sanitize a value for use in a Cloud Logging filter string.
+
+    Escapes double quotes and backslashes to prevent filter injection."""
+    return value.replace('\\', '\\\\').replace('"', '\\"')
+
   def _get_task_log_query_filter(self, task_id: str, task_name: str) -> str:
     """Returns the filter string for querying task logs."""
-    query = (f'jsonPayload.extras.task_id="{task_id}" AND '
-             f'jsonPayload.extras.testcase_id="{self._testcase_id}" AND '
-             f'jsonPayload.extras.task_name="{task_name}"')
+    safe_task_id = self._sanitize_filter_value(task_id)
+    safe_task_name = self._sanitize_filter_value(task_name)
+    safe_testcase_id = self._sanitize_filter_value(str(self._testcase_id))
+    query = (f'jsonPayload.extras.task_id="{safe_task_id}" AND '
+             f'jsonPayload.extras.testcase_id="{safe_testcase_id}" AND '
+             f'jsonPayload.extras.task_name="{safe_task_name}"')
     query += f' AND {self._get_time_range_filter(days=31)}'
     return query
 

src/clusterfuzz/_internal/tests/appengine/handlers/testcase_detail/show_test.py

@@ -607,3 +607,33 @@ def test_unreproducible_get(self):
     self.assertDictContainsSubset({
         'lines': [show.Line(1, 'crash_stacktrace', False)]
     }, result['last_tested_crash_stacktrace'])
+
+
+class TaskLogHandlerValidationTest(unittest.TestCase):
+  """Test that TaskLogHandler validates task_name against the known set."""
+
+  def test_valid_task_names(self):
+    """Verify the known valid task names."""
+    from handlers.testcase_detail import testcase_status_events
+    valid_names = (
+        testcase_status_events.TestcaseStatusInfo.TASK_EVENTS_NAMES +
+        testcase_status_events.TestcaseStatusInfo.CHROME_TASK_EVENTS_NAMES)
+
+    self.assertIn('analyze', valid_names)
+    self.assertIn('minimize', valid_names)
+    self.assertIn('progression', valid_names)
+    self.assertIn('regression', valid_names)
+    self.assertIn('variant', valid_names)
+    self.assertIn('blame', valid_names)
+    self.assertIn('impact', valid_names)
+
+  def test_injection_payloads_rejected(self):
+    """Verify that injection payloads are not valid task names."""
+    from handlers.testcase_detail import testcase_status_events
+    valid_names = (
+        testcase_status_events.TestcaseStatusInfo.TASK_EVENTS_NAMES +
+        testcase_status_events.TestcaseStatusInfo.CHROME_TASK_EVENTS_NAMES)
+
+    self.assertNotIn('analyze" OR "1"="1', valid_names)
+    self.assertNotIn('evil_task', valid_names)
+    self.assertNotIn('', valid_names)

src/clusterfuzz/_internal/tests/appengine/handlers/testcase_detail/testcase_status_events_test.py

@@ -834,3 +834,34 @@ def test_get_task_log_api_call(self):
     self.assertLess(
         result.find('"payload": "log1"'), result.find('"payload": "log2"'))
     self.assertEqual(result.count('\n'), 5)
+
+
+class SanitizeFilterValueTest(unittest.TestCase):
+  """Test _sanitize_filter_value for Cloud Logging filter injection."""
+
+  def test_normal_value(self):
+    """Test that normal values pass through unchanged."""
+    self.assertEqual(
+        testcase_status_events.TestcaseEventHistory._sanitize_filter_value(
+            'analyze'),
+        'analyze')
+
+  def test_double_quote_escaped(self):
+    """Test that double quotes are escaped to prevent filter injection."""
+    self.assertEqual(
+        testcase_status_events.TestcaseEventHistory._sanitize_filter_value(
+            'analyze" OR resource.type="global'),
+        'analyze\\" OR resource.type=\\"global')
+
+  def test_backslash_escaped(self):
+    """Test that backslashes are escaped."""
+    self.assertEqual(
+        testcase_status_events.TestcaseEventHistory._sanitize_filter_value(
+            'test\\value'),
+        'test\\\\value')
+
+  def test_empty_string(self):
+    """Test empty string."""
+    self.assertEqual(
+        testcase_status_events.TestcaseEventHistory._sanitize_filter_value(''),
+        '')