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Diffstat (limited to 'zen/symlink_target.h')
| -rw-r--r-- | zen/symlink_target.h | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/zen/symlink_target.h b/zen/symlink_target.h new file mode 100644 index 00000000..3704eebe --- /dev/null +++ b/zen/symlink_target.h @@ -0,0 +1,140 @@ +// ************************************************************************** +// * This file is part of the FreeFileSync project. It is distributed under * +// * GNU General Public License: http://www.gnu.org/licenses/gpl.html * +// * Copyright (C) 2008-2011 ZenJu (zhnmju123 AT gmx.de) * +// ************************************************************************** + +#ifndef SYMLINK_WIN_H_INCLUDED +#define SYMLINK_WIN_H_INCLUDED + +#include "scope_guard.h" +#include "file_error.h" + +#ifdef FFS_WIN +#include "win.h" //includes "windows.h" +#include "WinIoCtl.h" +#include "privilege.h" +#include "long_path_prefix.h" + +#elif defined FFS_LINUX +#include <unistd.h> +#endif + + +#ifdef _MSC_VER //I don't have Windows Driver Kit at hands right now, so unfortunately we need to redefine this structures 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(const Zstring& linkPath) //throw FileError +{ + using namespace zen; +#ifdef FFS_WIN + //FSCTL_GET_REPARSE_POINT: http://msdn.microsoft.com/en-us/library/aa364571(VS.85).aspx + + try //reading certain symlinks/junctions requires admin rights! This shall not cause an error in user mode! + { + Privileges::getInstance().ensureActive(SE_BACKUP_NAME); //throw FileError + } + catch (...) {} + + const HANDLE hLink = ::CreateFile(applyLongPathPrefix(linkPath).c_str(), + GENERIC_READ, + FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, + 0, + OPEN_EXISTING, + FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT, + NULL); + if (hLink == INVALID_HANDLE_VALUE) + throw FileError(_("Error resolving symbolic link:") + "\n\"" + linkPath + "\"" + "\n\n" + getLastErrorFormatted()); + ZEN_ON_BLOCK_EXIT(::CloseHandle(hLink)); + + //respect alignment issues... + const DWORD bufferSize = REPARSE_DATA_BUFFER_HEADER_SIZE + MAXIMUM_REPARSE_DATA_BUFFER_SIZE; + std::vector<char> buffer(bufferSize); + + DWORD bytesReturned; //dummy value required by FSCTL_GET_REPARSE_POINT! + if (!::DeviceIoControl(hLink, //__in HANDLE hDevice, + FSCTL_GET_REPARSE_POINT, //__in DWORD dwIoControlCode, + NULL, //__in_opt LPVOID lpInBuffer, + 0, //__in DWORD nInBufferSize, + &buffer[0], //__out_opt LPVOID lpOutBuffer, + bufferSize, //__in DWORD nOutBufferSize, + &bytesReturned, //__out_opt LPDWORD lpBytesReturned, + NULL)) //__inout_opt LPOVERLAPPED lpOverlapped + throw FileError(_("Error resolving symbolic link:") + "\n\"" + linkPath + "\"" + "\n\n" + getLastErrorFormatted()); + + REPARSE_DATA_BUFFER& reparseData = *reinterpret_cast<REPARSE_DATA_BUFFER*>(&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(_("Error resolving symbolic link:") + "\n\"" + linkPath + "\"" + "\n\n" + "Not a symbolic link or junction!"); + + //absolute symlinks and junctions technically start with \??\ while relative ones do not + if (startsWith(output, Zstr("\\??\\"))) + output = Zstring(output.c_str() + 4, output.length() - 4); + + return output; + +#elif defined FFS_LINUX + const int BUFFER_SIZE = 10000; + std::vector<char> buffer(BUFFER_SIZE); + + const int bytesWritten = ::readlink(linkPath.c_str(), &buffer[0], BUFFER_SIZE); + if (bytesWritten < 0 || bytesWritten >= BUFFER_SIZE) + { + std::wstring errorMessage = _("Error resolving symbolic link:") + "\n\"" + linkPath + "\""; + if (bytesWritten < 0) + errorMessage += L"\n\n" + getLastErrorFormatted(); + throw FileError(errorMessage); + } + buffer[bytesWritten] = 0; //set null-terminating char + + return Zstring(&buffer[0], bytesWritten); +#endif +} +} + +#endif // SYMLINK_WIN_H_INCLUDED |