# # Copyright (C) 2016 The Android Open Source Project # # 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. import errno from ctypes import WinDLL, get_last_error, FormatError, WinError, addressof from ctypes import c_buffer from ctypes.wintypes import BOOL, BOOLEAN, LPCWSTR, DWORD, HANDLE, POINTER, c_ubyte from ctypes.wintypes import WCHAR, USHORT, LPVOID, Structure, Union, ULONG from ctypes.wintypes import byref kernel32 = WinDLL('kernel32', use_last_error=True) LPDWORD = POINTER(DWORD) UCHAR = c_ubyte # Win32 error codes ERROR_SUCCESS = 0 ERROR_NOT_SUPPORTED = 50 ERROR_PRIVILEGE_NOT_HELD = 1314 # Win32 API entry points CreateSymbolicLinkW = kernel32.CreateSymbolicLinkW CreateSymbolicLinkW.restype = BOOLEAN CreateSymbolicLinkW.argtypes = (LPCWSTR, # lpSymlinkFileName In LPCWSTR, # lpTargetFileName In DWORD) # dwFlags In # Symbolic link creation flags SYMBOLIC_LINK_FLAG_FILE = 0x00 SYMBOLIC_LINK_FLAG_DIRECTORY = 0x01 # symlink support for CreateSymbolicLink() starting with Windows 10 (1703, v10.0.14972) SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE = 0x02 GetFileAttributesW = kernel32.GetFileAttributesW GetFileAttributesW.restype = DWORD GetFileAttributesW.argtypes = (LPCWSTR,) # lpFileName In INVALID_FILE_ATTRIBUTES = 0xFFFFFFFF FILE_ATTRIBUTE_REPARSE_POINT = 0x00400 CreateFileW = kernel32.CreateFileW CreateFileW.restype = HANDLE CreateFileW.argtypes = (LPCWSTR, # lpFileName In DWORD, # dwDesiredAccess In DWORD, # dwShareMode In LPVOID, # lpSecurityAttributes In_opt DWORD, # dwCreationDisposition In DWORD, # dwFlagsAndAttributes In HANDLE) # hTemplateFile In_opt CloseHandle = kernel32.CloseHandle CloseHandle.restype = BOOL CloseHandle.argtypes = (HANDLE,) # hObject In INVALID_HANDLE_VALUE = HANDLE(-1).value OPEN_EXISTING = 3 FILE_FLAG_BACKUP_SEMANTICS = 0x02000000 FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000 DeviceIoControl = kernel32.DeviceIoControl DeviceIoControl.restype = BOOL DeviceIoControl.argtypes = (HANDLE, # hDevice In DWORD, # dwIoControlCode In LPVOID, # lpInBuffer In_opt DWORD, # nInBufferSize In LPVOID, # lpOutBuffer Out_opt DWORD, # nOutBufferSize In LPDWORD, # lpBytesReturned Out_opt LPVOID) # lpOverlapped Inout_opt # Device I/O control flags and options FSCTL_GET_REPARSE_POINT = 0x000900A8 IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003 IO_REPARSE_TAG_SYMLINK = 0xA000000C MAXIMUM_REPARSE_DATA_BUFFER_SIZE = 0x4000 class GENERIC_REPARSE_BUFFER(Structure): _fields_ = (('DataBuffer', UCHAR * 1),) class SYMBOLIC_LINK_REPARSE_BUFFER(Structure): _fields_ = (('SubstituteNameOffset', USHORT), ('SubstituteNameLength', USHORT), ('PrintNameOffset', USHORT), ('PrintNameLength', USHORT), ('Flags', ULONG), ('PathBuffer', WCHAR * 1)) @property def PrintName(self): arrayt = WCHAR * (self.PrintNameLength // 2) offset = type(self).PathBuffer.offset + self.PrintNameOffset return arrayt.from_address(addressof(self) + offset).value class MOUNT_POINT_REPARSE_BUFFER(Structure): _fields_ = (('SubstituteNameOffset', USHORT), ('SubstituteNameLength', USHORT), ('PrintNameOffset', USHORT), ('PrintNameLength', USHORT), ('PathBuffer', WCHAR * 1)) @property def PrintName(self): arrayt = WCHAR * (self.PrintNameLength // 2) offset = type(self).PathBuffer.offset + self.PrintNameOffset return arrayt.from_address(addressof(self) + offset).value class REPARSE_DATA_BUFFER(Structure): class REPARSE_BUFFER(Union): _fields_ = (('SymbolicLinkReparseBuffer', SYMBOLIC_LINK_REPARSE_BUFFER), ('MountPointReparseBuffer', MOUNT_POINT_REPARSE_BUFFER), ('GenericReparseBuffer', GENERIC_REPARSE_BUFFER)) _fields_ = (('ReparseTag', ULONG), ('ReparseDataLength', USHORT), ('Reserved', USHORT), ('ReparseBuffer', REPARSE_BUFFER)) _anonymous_ = ('ReparseBuffer',) def create_filesymlink(source, link_name): """Creates a Windows file symbolic link source pointing to link_name.""" _create_symlink(source, link_name, SYMBOLIC_LINK_FLAG_FILE) def create_dirsymlink(source, link_name): """Creates a Windows directory symbolic link source pointing to link_name. """ _create_symlink(source, link_name, SYMBOLIC_LINK_FLAG_DIRECTORY) def _create_symlink(source, link_name, dwFlags): if not CreateSymbolicLinkW(link_name, source, dwFlags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE): # See https://github.com/golang/go/pull/24307/files#diff-b87bc12e4da2497308f9ef746086e4f0 # "the unprivileged create flag is unsupported below Windows 10 (1703, v10.0.14972). # retry without it." if not CreateSymbolicLinkW(link_name, source, dwFlags): code = get_last_error() error_desc = FormatError(code).strip() if code == ERROR_PRIVILEGE_NOT_HELD: raise OSError(errno.EPERM, error_desc, link_name) _raise_winerror( code, 'Error creating symbolic link \"%s\"'.format(link_name)) def islink(path): result = GetFileAttributesW(path) if result == INVALID_FILE_ATTRIBUTES: return False return bool(result & FILE_ATTRIBUTE_REPARSE_POINT) def readlink(path): reparse_point_handle = CreateFileW(path, 0, 0, None, OPEN_EXISTING, FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS, None) if reparse_point_handle == INVALID_HANDLE_VALUE: _raise_winerror( get_last_error(), 'Error opening symblic link \"%s\"'.format(path)) target_buffer = c_buffer(MAXIMUM_REPARSE_DATA_BUFFER_SIZE) n_bytes_returned = DWORD() io_result = DeviceIoControl(reparse_point_handle, FSCTL_GET_REPARSE_POINT, None, 0, target_buffer, len(target_buffer), byref(n_bytes_returned), None) CloseHandle(reparse_point_handle) if not io_result: _raise_winerror( get_last_error(), 'Error reading symblic link \"%s\"'.format(path)) rdb = REPARSE_DATA_BUFFER.from_buffer(target_buffer) if rdb.ReparseTag == IO_REPARSE_TAG_SYMLINK: return _preserve_encoding(path, rdb.SymbolicLinkReparseBuffer.PrintName) elif rdb.ReparseTag == IO_REPARSE_TAG_MOUNT_POINT: return _preserve_encoding(path, rdb.MountPointReparseBuffer.PrintName) # Unsupported reparse point type _raise_winerror( ERROR_NOT_SUPPORTED, 'Error reading symblic link \"%s\"'.format(path)) def _preserve_encoding(source, target): """Ensures target is the same string type (i.e. unicode or str) as source.""" if isinstance(source, unicode): return unicode(target) return str(target) def _raise_winerror(code, error_desc): win_error_desc = FormatError(code).strip() error_desc = "%s: %s".format(error_desc, win_error_desc) raise WinError(code, error_desc)