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filesystem.cpp: __std_fs_change_permissions() and __std_fs_get_temp_path() should avoid TOCTOU #5970

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filesystem.cpp: __std_fs_change_permissions() and __std_fs_get_temp_path() should avoid TOCTOU #5970

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67 changes: 28 additions & 39 deletions stl/src/filesystem.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -636,44 +636,30 @@ struct __std_fs_file_id { // typedef struct _FILE_ID_INFO {

[[nodiscard]] __std_win_error __stdcall __std_fs_change_permissions(
_In_z_ const wchar_t* const _Path, _In_ const bool _Follow_symlinks, _In_ const bool _Readonly) noexcept {
const DWORD _Old_attributes = GetFileAttributesW(_Path);
if (_Old_attributes == INVALID_FILE_ATTRIBUTES) {
return __std_win_error{GetLastError()};
}

const DWORD _Readonly_test = _Readonly ? FILE_ATTRIBUTE_READONLY : 0;
if ((_Old_attributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0u && _Follow_symlinks) {
__std_win_error _Err;
_STD _Fs_file _Handle(_Path,
__std_access_rights::_File_read_attributes | __std_access_rights::_File_write_attributes,
__std_fs_file_flags::_Backup_semantics, &_Err);

if (_Err != __std_win_error::_Success) {
return _Err;
}

FILE_BASIC_INFO _Basic_info;
if (!GetFileInformationByHandleEx(_Handle._Get(), FileBasicInfo, &_Basic_info, sizeof(_Basic_info))) {
return __std_win_error{GetLastError()};
}

if ((_Basic_info.FileAttributes & FILE_ATTRIBUTE_READONLY) == _Readonly_test) { // nothing to do
return __std_win_error::_Success;
}
const auto _File_flags = _Follow_symlinks
? __std_fs_file_flags::_Backup_semantics
: __std_fs_file_flags::_Backup_semantics | __std_fs_file_flags::_Open_reparse_point;
__std_win_error _Err;
_STD _Fs_file _Handle(_Path,
__std_access_rights::_File_read_attributes | __std_access_rights::_File_write_attributes, _File_flags, &_Err);

_Basic_info.FileAttributes ^= FILE_ATTRIBUTE_READONLY;
if (SetFileInformationByHandle(_Handle._Get(), FileBasicInfo, &_Basic_info, sizeof(_Basic_info))) {
return __std_win_error::_Success;
}
if (_Err != __std_win_error::_Success) {
return _Err;
}

FILE_BASIC_INFO _Basic_info;
if (!GetFileInformationByHandleEx(_Handle._Get(), FileBasicInfo, &_Basic_info, sizeof(_Basic_info))) {
return __std_win_error{GetLastError()};
}

if ((_Old_attributes & FILE_ATTRIBUTE_READONLY) == _Readonly_test) { // nothing to do
const DWORD _Readonly_test = _Readonly ? FILE_ATTRIBUTE_READONLY : 0;
if ((_Basic_info.FileAttributes & FILE_ATTRIBUTE_READONLY) == _Readonly_test) { // nothing to do
return __std_win_error::_Success;
}

if (SetFileAttributesW(_Path, _Old_attributes ^ FILE_ATTRIBUTE_READONLY)) {
_Basic_info.FileAttributes ^= FILE_ATTRIBUTE_READONLY;
if (SetFileInformationByHandle(_Handle._Get(), FileBasicInfo, &_Basic_info, sizeof(_Basic_info))) {
return __std_win_error::_Success;
}

Expand Down Expand Up @@ -818,19 +804,22 @@ namespace {
}

// Effects: If exists(p) is false or is_directory(p) is false, an error is reported
const DWORD _Attributes = GetFileAttributesW(_Target);
if (_Attributes == INVALID_FILE_ATTRIBUTES || (_Attributes & FILE_ATTRIBUTE_DIRECTORY) == 0u) {
__std_fs_file_handle _Handle;
__std_win_error _Last_error = __std_fs_open_handle(
&_Handle, _Target, __std_access_rights::_File_read_attributes, __std_fs_file_flags::_Backup_semantics);
if (_Last_error != __std_win_error::_Success) {
return {_Size, __std_win_error::_Max};
}

if ((_Attributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0u) {
__std_fs_file_handle _Handle;
const auto _Last_error = __std_fs_open_handle(
&_Handle, _Target, __std_access_rights::_File_read_attributes, __std_fs_file_flags::_Backup_semantics);
__std_fs_close_handle(_Handle);
if (_Last_error != __std_win_error::_Success) {
return {_Size, __std_win_error::_Max};
}
unsigned long _File_attributes;
_Last_error = __std_fs_get_file_attributes_by_handle(_Handle, &_File_attributes);
__std_fs_close_handle(_Handle);
if (_Last_error != __std_win_error::_Success) {
return {_Size, __std_win_error::_Max};
}

if ((_File_attributes & FILE_ATTRIBUTE_DIRECTORY) == 0u) {
return {_Size, __std_win_error::_Max};
}

return {_Size, __std_win_error::_Success};
Expand Down