codekingpro/portable-devtools

1from __future__ import annotations2 3import os4import sys5from contextlib import suppress6from errno import EACCES7from pathlib import Path8from typing import cast9 10from ._api import BaseFileLock11from ._util import ensure_directory_exists, raise_on_not_writable_file12 13if sys.platform == "win32":  # pragma: win32 cover14    import ctypes15    import msvcrt16    from ctypes import wintypes17 18    # Windows API constants for reparse point detection19    FILE_ATTRIBUTE_REPARSE_POINT = 0x0000040020    INVALID_FILE_ATTRIBUTES = 0xFFFFFFFF21 22    # Load kernel32.dll23    _kernel32 = ctypes.WinDLL("kernel32", use_last_error=True)24    _kernel32.GetFileAttributesW.argtypes = [wintypes.LPCWSTR]25    _kernel32.GetFileAttributesW.restype = wintypes.DWORD26 27    def _is_reparse_point(path: str) -> bool:28        """29        Check if a path is a reparse point (symlink, junction, etc.) on Windows.30 31        :param path: Path to check32 33        :returns: True if path is a reparse point, False otherwise34 35        :raises OSError: If GetFileAttributesW fails for reasons other than file-not-found36 37        """38        attrs = _kernel32.GetFileAttributesW(path)39        if attrs == INVALID_FILE_ATTRIBUTES:40            # File doesn't exist yet - that's fine, we'll create it41            err = ctypes.get_last_error()42            if err == 2:  # noqa: PLR2004  # ERROR_FILE_NOT_FOUND43                return False44            if err == 3:  # noqa: PLR2004 # ERROR_PATH_NOT_FOUND45                return False46            # Some other error - let caller handle it47            return False48        return bool(attrs & FILE_ATTRIBUTE_REPARSE_POINT)49 50    class WindowsFileLock(BaseFileLock):51        """52        Uses the :func:`msvcrt.locking` function to hard lock the lock file on Windows systems.53 54        Lock file cleanup: Windows attempts to delete the lock file after release, but deletion is55        not guaranteed in multi-threaded scenarios where another thread holds an open handle. The lock56        file may persist on disk, which does not affect lock correctness.57        """58 59        def _acquire(self) -> None:60            raise_on_not_writable_file(self.lock_file)61            ensure_directory_exists(self.lock_file)62 63            # Security check: Refuse to open reparse points (symlinks, junctions)64            # This prevents TOCTOU symlink attacks (CVE-TBD)65            if _is_reparse_point(self.lock_file):66                msg = f"Lock file is a reparse point (symlink/junction): {self.lock_file}"67                raise OSError(msg)68 69            flags = (70                os.O_RDWR  # open for read and write71                | os.O_CREAT  # create file if not exists72            )73            try:74                fd = os.open(self.lock_file, flags, self._open_mode())75            except OSError as exception:76                if exception.errno != EACCES:  # has no access to this lock77                    raise78            else:79                try:80                    msvcrt.locking(fd, msvcrt.LK_NBLCK, 1)81                except OSError as exception:82                    os.close(fd)  # close file first83                    if exception.errno != EACCES:  # file is already locked84                        raise85                else:86                    self._context.lock_file_fd = fd87 88        def _release(self) -> None:89            fd = cast("int", self._context.lock_file_fd)90            self._context.lock_file_fd = None91            msvcrt.locking(fd, msvcrt.LK_UNLCK, 1)92            os.close(fd)93 94            with suppress(OSError):95                Path(self.lock_file).unlink()96 97else:  # pragma: win32 no cover98 99    class WindowsFileLock(BaseFileLock):100        """Uses the :func:`msvcrt.locking` function to hard lock the lock file on Windows systems."""101 102        def _acquire(self) -> None:103            raise NotImplementedError104 105        def _release(self) -> None:106            raise NotImplementedError107 108 109__all__ = [110    "WindowsFileLock",111]112