mklink.c

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/*
 *  MKLINK.C - mklink internal command.
 */

#include <precomp.h>

#ifdef INCLUDE_CMD_MKLINK

/* There is no API for creating junctions, so we must do it the hard way */
static BOOL CreateJunction(LPCTSTR LinkName, LPCTSTR TargetName)
{
    /* Structure for reparse point daya when ReparseTag is one of
     * the tags defined by Microsoft. Copied from MinGW winnt.h */
    typedef struct _REPARSE_DATA_BUFFER {
        DWORD  ReparseTag;
        WORD   ReparseDataLength;
        WORD   Reserved;
        _ANONYMOUS_UNION union {
            struct {
                WORD   SubstituteNameOffset;
                WORD   SubstituteNameLength;
                WORD   PrintNameOffset;
                WORD   PrintNameLength;
                ULONG  Flags;
                WCHAR PathBuffer[1];
            } SymbolicLinkReparseBuffer;
            struct {
                WORD   SubstituteNameOffset;
                WORD   SubstituteNameLength;
                WORD   PrintNameOffset;
                WORD   PrintNameLength;
                WCHAR PathBuffer[1];
            } MountPointReparseBuffer;
            struct {
                BYTE   DataBuffer[1];
            } GenericReparseBuffer;
        } DUMMYUNIONNAME;
    } REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER;

    HMODULE hNTDLL = GetModuleHandle(_T("NTDLL"));
    BOOLEAN (WINAPI *RtlDosPathNameToNtPathName_U)(PCWSTR, PUNICODE_STRING, PCWSTR *, CURDIR *)
        = (BOOLEAN (WINAPI *)(PCWSTR, PUNICODE_STRING, PCWSTR *, CURDIR *))GetProcAddress(hNTDLL, "RtlDosPathNameToNtPathName_U");
    VOID (WINAPI *RtlFreeUnicodeString)(PUNICODE_STRING)
        = (VOID (WINAPI *)(PUNICODE_STRING))GetProcAddress(hNTDLL, "RtlFreeUnicodeString");

    TCHAR TargetFullPath[MAX_PATH];
#ifdef UNICODE
#define TargetFullPathW TargetFullPath
#else
    WCHAR TargetFullPathW[MAX_PATH];
#endif
    UNICODE_STRING TargetNTPath;
    HANDLE hJunction;

    /* The data for this kind of reparse point has two strings:
     * The first ("SubstituteName") is the full target path in NT format,
     * the second ("PrintName") is the full target path in Win32 format.
     * Both of these must be wide-character strings. */
    if (!RtlDosPathNameToNtPathName_U ||
        !RtlFreeUnicodeString ||
        !GetFullPathName(TargetName, MAX_PATH, TargetFullPath, NULL) ||
#ifndef UNICODE
        !MultiByteToWideChar(CP_ACP, 0, TargetFullPath, -1, TargetFullPathW, -1) ||
#endif
        !RtlDosPathNameToNtPathName_U(TargetFullPathW, &TargetNTPath, NULL, NULL))
    {
        return FALSE;
    }

    /* We have both the names we need, so time to create the junction.
     * Start with an empty directory */
    if (!CreateDirectory(LinkName, NULL))
    {
        RtlFreeUnicodeString(&TargetNTPath);
        return FALSE;
    }

    /* Open the directory we just created */
    hJunction = CreateFile(LinkName, GENERIC_WRITE, 0, NULL,
        OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
    if (hJunction != INVALID_HANDLE_VALUE)
    {
        /* Allocate a buffer large enough to hold both strings, including trailing NULs */
        SIZE_T TargetLen = wcslen(TargetFullPathW) * sizeof(WCHAR);
        DWORD DataSize = (DWORD)(FIELD_OFFSET(REPARSE_DATA_BUFFER, MountPointReparseBuffer.PathBuffer)
                          + TargetNTPath.Length + sizeof(WCHAR)
                          + TargetLen           + sizeof(WCHAR));
        PREPARSE_DATA_BUFFER Data = _alloca(DataSize);

        /* Fill it out and use it to turn the directory into a reparse point */
        Data->ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
        Data->ReparseDataLength = (WORD)(DataSize - FIELD_OFFSET(REPARSE_DATA_BUFFER, MountPointReparseBuffer));
        Data->Reserved = 0;
        Data->MountPointReparseBuffer.SubstituteNameOffset = 0;
        Data->MountPointReparseBuffer.SubstituteNameLength = TargetNTPath.Length;
        wcscpy(Data->MountPointReparseBuffer.PathBuffer,
               TargetNTPath.Buffer);
        Data->MountPointReparseBuffer.PrintNameOffset = TargetNTPath.Length + sizeof(WCHAR);
        Data->MountPointReparseBuffer.PrintNameLength = (USHORT)TargetLen;
        wcscpy((WCHAR *)((BYTE *)Data->MountPointReparseBuffer.PathBuffer
                         + Data->MountPointReparseBuffer.PrintNameOffset),
               TargetFullPathW);
        if (DeviceIoControl(hJunction, FSCTL_SET_REPARSE_POINT,
                            Data, DataSize, NULL, 0, &DataSize, NULL))
        {
            /* Success */
            CloseHandle(hJunction);
            RtlFreeUnicodeString(&TargetNTPath);
            return TRUE;
        }
        CloseHandle(hJunction);
    }
    RemoveDirectory(LinkName);
    RtlFreeUnicodeString(&TargetNTPath);
    return FALSE;
}

INT
cmd_mklink(LPTSTR param)
{
    HMODULE hKernel32 = GetModuleHandle(_T("KERNEL32"));
    DWORD Flags = 0;
    enum { SYMBOLIC, HARD, JUNCTION } LinkType = SYMBOLIC;
    INT NumFiles = 0;
    LPTSTR Name[2];
    INT argc, i;
    LPTSTR *arg;

    if (!_tcsncmp(param, _T("/?"), 2))
    {
        ConOutResPuts(STRING_MKLINK_HELP);
        return 0;
    }

    arg = split(param, &argc, FALSE, FALSE);
    for (i = 0; i < argc; i++)
    {
        if (arg[i][0] == _T('/'))
        {
            if (!_tcsicmp(arg[i], _T("/D")))
                Flags |= 1; /* SYMBOLIC_LINK_FLAG_DIRECTORY */
            else if (!_tcsicmp(arg[i], _T("/H")))
                LinkType = HARD;
            else if (!_tcsicmp(arg[i], _T("/J")))
                LinkType = JUNCTION;
            else
            {
                error_invalid_switch(arg[i][1]);
                freep(arg);
                return 1;
            }
        }
        else
        {
            if (NumFiles == 2)
            {
                error_too_many_parameters(arg[i]);
                freep(arg);
                return 1;
            }
            Name[NumFiles++] = arg[i];
        }
    }
    freep(arg);

    if (NumFiles != 2)
    {
        error_req_param_missing();
        return 1;
    }

    nErrorLevel = 0;

    if (LinkType == SYMBOLIC)
    {
        /* CreateSymbolicLink doesn't exist in old versions of Windows,
         * so load dynamically */
        BOOL (WINAPI *CreateSymbolicLink)(LPCTSTR, LPCTSTR, DWORD)
#ifdef UNICODE
            = (BOOL (WINAPI *)(LPCTSTR, LPCTSTR, DWORD))GetProcAddress(hKernel32, "CreateSymbolicLinkW");
#else
            = (BOOL (WINAPI *)(LPCTSTR, LPCTSTR, DWORD))GetProcAddress(hKernel32, "CreateSymbolicLinkA");
#endif
        if (CreateSymbolicLink && CreateSymbolicLink(Name[0], Name[1], Flags))
        {
            ConOutResPrintf(STRING_MKLINK_CREATED_SYMBOLIC, Name[0], Name[1]);
            return 0;
        }
    }
    else if (LinkType == HARD)
    {
        /* CreateHardLink doesn't exist in old versions of Windows,
         * so load dynamically */
        BOOL (WINAPI *CreateHardLink)(LPCTSTR, LPCTSTR, LPSECURITY_ATTRIBUTES)
#ifdef UNICODE
            = (BOOL (WINAPI *)(LPCTSTR, LPCTSTR, LPSECURITY_ATTRIBUTES))GetProcAddress(hKernel32, "CreateHardLinkW");
#else
            = (BOOL (WINAPI *)(LPCTSTR, LPCTSTR, LPSECURITY_ATTRIBUTES))GetProcAddress(hKernel32, "CreateHardLinkA");
#endif
        if (CreateHardLink && CreateHardLink(Name[0], Name[1], NULL))
        {
            ConOutResPrintf(STRING_MKLINK_CREATED_HARD, Name[0], Name[1]);
            return 0;
        }
    }
    else
    {
        if (CreateJunction(Name[0], Name[1]))
        {
            ConOutResPrintf(STRING_MKLINK_CREATED_JUNCTION, Name[0], Name[1]);
            return 0;
        }
    }

    ErrorMessage(GetLastError(), _T("MKLINK"));
    return 1;
}

#endif /* INCLUDE_CMD_MKLINK */