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platform_utils_win32.py
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#
# 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, 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 = BOOL
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):
# Note: Win32 documentation for CreateSymbolicLink is incorrect.
# On success, the function returns "1".
# On error, the function returns some random value (e.g. 1280).
# The best bet seems to use "GetLastError" and check for error/success.
CreateSymbolicLinkW(link_name, source, dwFlags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE)
code = get_last_error()
if code != ERROR_SUCCESS:
# 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."
CreateSymbolicLinkW(link_name, source, dwFlags)
code = get_last_error()
if code != ERROR_SUCCESS:
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)