REFACTOR: Add path canonicalization and traversal guard to setup_logging log_file_path validation

mssql_python/logging.py

@@ -273,17 +273,44 @@ def _cleanup_handlers(self):
                     except:
                         pass
 
-    def _validate_log_file_extension(self, file_path: str) -> None:
+    def _validate_log_file_path(self, file_path: str) -> str:
         """
-        Validate that the log file has an allowed extension.
+        Validate and sanitize the log file path.
+
+        Resolves the path to its canonical form, checks for path traversal
+        outside the current working directory (for relative paths), and
+        validates the file extension.
 
         Args:
             file_path: Path to the log file
 
+        Returns:
+            The resolved canonical path.
+
         Raises:
-            ValueError: If the file extension is not allowed
+            ValueError: If the path contains traversal outside the allowed
+                        base directory, or if the file extension is not allowed
         """
-        _, ext = os.path.splitext(file_path)
+        resolved = os.path.realpath(os.path.abspath(file_path))
+
+        # For relative paths, ensure the resolved path stays under cwd
+        if not os.path.isabs(file_path):
+            base = os.path.realpath(os.path.abspath(os.getcwd()))
+            # os.path.commonpath raises ValueError if paths are on different drives
+            try:
+                common = os.path.commonpath([base, resolved])
+            except ValueError:
+                raise ValueError(
+                    "log_file_path resolves outside the current working directory. "
+                    "Path traversal is not permitted for relative paths."
+                )
+            if common != base:
+                raise ValueError(
+                    "log_file_path resolves outside the current working directory. "
+                    "Path traversal is not permitted for relative paths."
+                )
+
+        _, ext = os.path.splitext(resolved)
         ext_lower = ext.lower()
 
         if ext_lower not in ALLOWED_LOG_EXTENSIONS:
@@ -292,6 +319,8 @@ def _validate_log_file_extension(self, file_path: str) -> None:
                 f"Invalid log file extension '{ext}'. " f"Allowed extensions: {allowed}"
             )
 
+        return resolved
+
     def _write_log_header(self):
         """
         Write CSV header and metadata to the log file.
@@ -483,10 +512,9 @@ def _setLevel(
                 )
             self._output_mode = output
 
-        # Store custom log file path if provided
+        # Store custom log file path if provided (sanitized)
         if log_file_path is not None:
-            self._validate_log_file_extension(log_file_path)
-            self._custom_log_path = log_file_path
+            self._custom_log_path = self._validate_log_file_path(log_file_path)
 
         # Setup handlers if not yet initialized or if output mode/path changed
         # Handler setup is protected by _handler_lock inside _setup_handlers()

tests/test_007_logging.py

@@ -150,8 +150,9 @@ def test_custom_log_file_path(self, cleanup_logger, temp_log_dir):
         setup_logging(log_file_path=custom_path)
         logger.debug("Test message")
 
-        assert logger.log_file == custom_path
-        assert os.path.exists(custom_path)
+        resolved = os.path.realpath(os.path.abspath(custom_path))
+        assert logger.log_file == resolved
+        assert os.path.exists(resolved)
 
     def test_custom_log_file_path_creates_directory(self, cleanup_logger, temp_log_dir):
         """Custom log file path should create parent directories"""
@@ -179,6 +180,36 @@ def test_log_file_extension_validation_invalid(self, cleanup_logger, temp_log_di
         with pytest.raises(ValueError, match="Invalid log file extension"):
             setup_logging(log_file_path=custom_path)
 
+    def test_path_traversal_rejected(self, cleanup_logger, monkeypatch, tmp_path):
+        """Relative paths with traversal outside a controlled cwd should be rejected"""
+        monkeypatch.chdir(tmp_path)
+        with pytest.raises(ValueError, match="Path traversal is not permitted"):
+            setup_logging(log_file_path="../evil.log")
+
+    def test_path_traversal_dot_dot_rejected(self, cleanup_logger, monkeypatch, tmp_path):
+        """Relative paths using ../ to escape a controlled cwd should be rejected"""
+        monkeypatch.chdir(tmp_path)
+        with pytest.raises(ValueError, match="Path traversal is not permitted"):
+            setup_logging(log_file_path="../nested/evil.log")
+
+    def test_path_traversal_different_drive(self, cleanup_logger, monkeypatch, tmp_path):
+        """commonpath ValueError (e.g. different drives on Windows) should be rejected"""
+        monkeypatch.chdir(tmp_path)
+
+        def mock_commonpath(paths):
+            raise ValueError("Can't mix absolute and relative paths")
+
+        monkeypatch.setattr(os.path, "commonpath", mock_commonpath)
+        with pytest.raises(ValueError, match="Path traversal is not permitted"):
+            setup_logging(log_file_path="subdir/test.log")
+
+    def test_absolute_path_allowed(self, cleanup_logger, temp_log_dir):
+        """Absolute paths should be allowed (developer-controlled)"""
+        custom_path = os.path.join(temp_log_dir, "absolute_test.log")
+        setup_logging(log_file_path=custom_path)
+        logger.debug("Test message")
+        assert os.path.exists(os.path.realpath(os.path.abspath(custom_path)))
+
 
 class TestCSVFormat:
     """Test CSV output format"""