// ************************************************************************** // * This file is part of the FreeFileSync project. It is distributed under * // * GNU General Public License: http://www.gnu.org/licenses/gpl-3.0 * // * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved * // ************************************************************************** #ifndef SYMLINK_TARGET_H_801783470198357483 #define SYMLINK_TARGET_H_801783470198357483 #include "scope_guard.h" #include "file_error.h" #ifdef ZEN_WIN #include "win.h" //includes "windows.h" #include "privilege.h" #include "long_path_prefix.h" #include "dll.h" #elif defined ZEN_LINUX || defined ZEN_MAC #include #include //realpath #endif namespace zen { #ifdef ZEN_WIN bool isSymlink(const WIN32_FIND_DATA& data); //checking FILE_ATTRIBUTE_REPARSE_POINT is insufficient! bool isSymlink(DWORD fileAttributes, DWORD reparseTag); #endif Zstring getResolvedSymlinkPath(const Zstring& linkPath); //throw FileError; Win: requires Vista or later! Zstring getSymlinkTargetRaw (const Zstring& linkPath); //throw FileError } //################################ implementation ################################ #ifdef ZEN_WIN //I don't have Windows Driver Kit at hands right now, so unfortunately we need to redefine this structure and cross fingers... typedef struct _REPARSE_DATA_BUFFER //from ntifs.h { ULONG ReparseTag; USHORT ReparseDataLength; USHORT Reserved; union { struct { USHORT SubstituteNameOffset; USHORT SubstituteNameLength; USHORT PrintNameOffset; USHORT PrintNameLength; ULONG Flags; WCHAR PathBuffer[1]; } SymbolicLinkReparseBuffer; struct { USHORT SubstituteNameOffset; USHORT SubstituteNameLength; USHORT PrintNameOffset; USHORT PrintNameLength; WCHAR PathBuffer[1]; } MountPointReparseBuffer; struct { UCHAR DataBuffer[1]; } GenericReparseBuffer; }; } REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER; #define REPARSE_DATA_BUFFER_HEADER_SIZE FIELD_OFFSET(REPARSE_DATA_BUFFER, GenericReparseBuffer) #endif namespace { //retrieve raw target data of symlink or junction Zstring getSymlinkRawTargetString_impl(const Zstring& linkPath) //throw FileError { using namespace zen; #ifdef ZEN_WIN //FSCTL_GET_REPARSE_POINT: http://msdn.microsoft.com/en-us/library/aa364571(VS.85).aspx //reading certain symlinks/junctions requires admin rights! try { activatePrivilege(SE_BACKUP_NAME); } //throw FileError catch (FileError&) {} //This shall not cause an error in user mode! const HANDLE hLink = ::CreateFile(applyLongPathPrefix(linkPath).c_str(), //_In_ LPCTSTR lpFileName, //it seems we do not even need GENERIC_READ! 0, //_In_ DWORD dwDesiredAccess, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, //_In_ DWORD dwShareMode, nullptr, //_In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes, OPEN_EXISTING, //_In_ DWORD dwCreationDisposition, FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT, //_In_ DWORD dwFlagsAndAttributes, nullptr); //_In_opt_ HANDLE hTemplateFile if (hLink == INVALID_HANDLE_VALUE) THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), L"CreateFile"); ZEN_ON_SCOPE_EXIT(::CloseHandle(hLink)); //respect alignment issues... const DWORD bufferSize = REPARSE_DATA_BUFFER_HEADER_SIZE + MAXIMUM_REPARSE_DATA_BUFFER_SIZE; std::vector buffer(bufferSize); DWORD bytesReturned = 0; //dummy value required by FSCTL_GET_REPARSE_POINT! if (!::DeviceIoControl(hLink, //__in HANDLE hDevice, FSCTL_GET_REPARSE_POINT, //__in DWORD dwIoControlCode, nullptr, //__in_opt LPVOID lpInBuffer, 0, //__in DWORD nInBufferSize, &buffer[0], //__out_opt LPVOID lpOutBuffer, bufferSize, //__in DWORD nOutBufferSize, &bytesReturned, //__out_opt LPDWORD lpBytesReturned, nullptr)) //__inout_opt LPOVERLAPPED lpOverlapped THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), L"DeviceIoControl, FSCTL_GET_REPARSE_POINT"); REPARSE_DATA_BUFFER& reparseData = *reinterpret_cast(&buffer[0]); //REPARSE_DATA_BUFFER needs to be artificially enlarged! Zstring output; if (reparseData.ReparseTag == IO_REPARSE_TAG_SYMLINK) { output = Zstring(reparseData.SymbolicLinkReparseBuffer.PathBuffer + reparseData.SymbolicLinkReparseBuffer.SubstituteNameOffset / sizeof(WCHAR), reparseData.SymbolicLinkReparseBuffer.SubstituteNameLength / sizeof(WCHAR)); } else if (reparseData.ReparseTag == IO_REPARSE_TAG_MOUNT_POINT) { output = Zstring(reparseData.MountPointReparseBuffer.PathBuffer + reparseData.MountPointReparseBuffer.SubstituteNameOffset / sizeof(WCHAR), reparseData.MountPointReparseBuffer.SubstituteNameLength / sizeof(WCHAR)); } else throw FileError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), L"Not a symbolic link or junction."); //absolute symlinks and junctions use NT namespace naming convention while relative ones do not: //http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx#NT_Namespaces return ntPathToWin32Path(output); #elif defined ZEN_LINUX || defined ZEN_MAC const size_t BUFFER_SIZE = 10000; std::vector buffer(BUFFER_SIZE); const ssize_t bytesWritten = ::readlink(linkPath.c_str(), &buffer[0], BUFFER_SIZE); if (bytesWritten < 0) THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), L"readlink"); if (bytesWritten >= static_cast(BUFFER_SIZE)) //detect truncation, not an error for readlink! throw FileError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), L"readlink: buffer truncated."); return Zstring(&buffer[0], bytesWritten); //readlink does not append 0-termination! #endif } Zstring getResolvedSymlinkPath_impl(const Zstring& linkPath) //throw FileError { using namespace zen; #ifdef ZEN_WIN //GetFinalPathNameByHandle() is not available before Vista! typedef DWORD (WINAPI* GetFinalPathNameByHandleWFunc)(HANDLE hFile, LPTSTR lpszFilePath, DWORD cchFilePath, DWORD dwFlags); const SysDllFun getFinalPathNameByHandle(L"kernel32.dll", "GetFinalPathNameByHandleW"); if (!getFinalPathNameByHandle) throw FileError(replaceCpy(_("Cannot determine final path for %x."), L"%x", fmtPath(linkPath)), replaceCpy(_("Cannot find system function %x."), L"%x", L"\"GetFinalPathNameByHandleW\"")); const HANDLE hFile = ::CreateFile(applyLongPathPrefix(linkPath).c_str(), //_In_ LPCTSTR lpFileName, 0, //_In_ DWORD dwDesiredAccess, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, //_In_ DWORD dwShareMode, nullptr, //_In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes, OPEN_EXISTING, //_In_ DWORD dwCreationDisposition, //needed to open a directory: FILE_FLAG_BACKUP_SEMANTICS, //_In_ DWORD dwFlagsAndAttributes, nullptr); //_In_opt_ HANDLE hTemplateFile if (hFile == INVALID_HANDLE_VALUE) THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot determine final path for %x."), L"%x", fmtPath(linkPath)), L"CreateFile"); ZEN_ON_SCOPE_EXIT(::CloseHandle(hFile)); const DWORD bufferSize = getFinalPathNameByHandle(hFile, nullptr, 0, 0); if (bufferSize == 0) THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot determine final path for %x."), L"%x", fmtPath(linkPath)), L"GetFinalPathNameByHandle"); std::vector targetPath(bufferSize); const DWORD charsWritten = getFinalPathNameByHandle(hFile, //__in HANDLE hFile, &targetPath[0], //__out LPTSTR lpszFilePath, bufferSize, //__in DWORD cchFilePath, 0); //__in DWORD dwFlags if (charsWritten == 0 || charsWritten >= bufferSize) { const std::wstring errorMsg = replaceCpy(_("Cannot determine final path for %x."), L"%x", fmtPath(linkPath)); if (charsWritten == 0) THROW_LAST_FILE_ERROR(errorMsg, L"GetFinalPathNameByHandle"); throw FileError(errorMsg); } return Zstring(&targetPath[0], charsWritten); #elif defined ZEN_LINUX || defined ZEN_MAC char* targetPath = ::realpath(linkPath.c_str(), nullptr); if (!targetPath) THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot determine final path for %x."), L"%x", fmtPath(linkPath)), L"realpath"); ZEN_ON_SCOPE_EXIT(::free(targetPath)); return targetPath; #endif } } namespace zen { inline Zstring getSymlinkTargetRaw(const Zstring& linkPath) { return getSymlinkRawTargetString_impl(linkPath); } inline Zstring getResolvedSymlinkPath(const Zstring& linkPath) { return getResolvedSymlinkPath_impl(linkPath); } #ifdef ZEN_WIN /* Reparse Point Tags http://msdn.microsoft.com/en-us/library/windows/desktop/aa365511(v=vs.85).aspx WIN32_FIND_DATA structure http://msdn.microsoft.com/en-us/library/windows/desktop/aa365740(v=vs.85).aspx The only surrogate reparse points are; IO_REPARSE_TAG_MOUNT_POINT IO_REPARSE_TAG_SYMLINK */ inline bool isSymlink(DWORD fileAttributes, DWORD reparseTag) { return (fileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0 && IsReparseTagNameSurrogate(reparseTag); } inline bool isSymlink(const WIN32_FIND_DATA& data) { return isSymlink(data.dwFileAttributes, data.dwReserved0); } #endif } #endif //SYMLINK_TARGET_H_801783470198357483