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git: fix 'cmd/git.exe' cannot launcher symlink
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Use GetFinalPathByHandleW to find the target of a symbolic link

Signed-off-by: Force Charlie <charlieio@outlook.com>
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@fcharlie
fcharlie committed Dec 8, 2018
1 parent 7f04a3a commit 521a655
Showing 1 changed file with 20 additions and 186 deletions.
206 changes: 20 additions & 186 deletions mingw-w64-git/git-wrapper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@
#define UNICODE
#define _UNICODE
#include <windows.h>
#include <winioctl.h>
#include <shlwapi.h>
#include <shellapi.h>
#include <stdio.h>
Expand Down Expand Up @@ -42,196 +41,31 @@ static void print_error(LPCWSTR prefix, DWORD error_number)
LocalFree((HLOCAL)buffer);
}

#ifndef IO_REPARSE_TAG_APPEXECLINK
#define IO_REPARSE_TAG_APPEXECLINK (0x8000001BL)
#endif

// https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/content/ntifs/ns-ntifs-_reparse_data_buffer

typedef struct _REPARSE_DATA_BUFFER {
ULONG ReparseTag; // Reparse tag type
USHORT ReparseDataLength; // Length of the reparse data
USHORT Reserved; // Used internally by NTFS to store remaining length

union {
// Structure for IO_REPARSE_TAG_SYMLINK
// Handled by nt!IoCompleteRequest
struct {
USHORT SubstituteNameOffset;
USHORT SubstituteNameLength;
USHORT PrintNameOffset;
USHORT PrintNameLength;
ULONG Flags;
WCHAR PathBuffer[1];
} SymbolicLinkReparseBuffer;

// Structure for IO_REPARSE_TAG_MOUNT_POINT
// Handled by nt!IoCompleteRequest
struct {
USHORT SubstituteNameOffset;
USHORT SubstituteNameLength;
USHORT PrintNameOffset;
USHORT PrintNameLength;
WCHAR PathBuffer[1];
} MountPointReparseBuffer;

// Structure for IO_REPARSE_TAG_WIM
// Handled by wimmount!FPOpenReparseTarget->wimserv.dll
// (wimsrv!ImageExtract)
struct {
GUID ImageGuid; // GUID of the mounted VIM image
BYTE ImagePathHash[0x14]; // Hash of the path to the file within the image
} WimImageReparseBuffer;

// Structure for IO_REPARSE_TAG_WOF
// Handled by FSCTL_GET_EXTERNAL_BACKING, FSCTL_SET_EXTERNAL_BACKING in NTFS
// (Windows 10+)
struct {
//-- WOF_EXTERNAL_INFO --------------------
ULONG Wof_Version; // Should be 1 (WOF_CURRENT_VERSION)
ULONG Wof_Provider; // Should be 2 (WOF_PROVIDER_FILE)

//-- FILE_PROVIDER_EXTERNAL_INFO_V1 --------------------
ULONG FileInfo_Version; // Should be 1 (FILE_PROVIDER_CURRENT_VERSION)
ULONG
FileInfo_Algorithm; // Usually 0 (FILE_PROVIDER_COMPRESSION_XPRESS4K)
} WofReparseBuffer;

// Structure for IO_REPARSE_TAG_APPEXECLINK
struct {
ULONG StringCount; // Number of the strings in the StringList, separated
// by '\0'
WCHAR StringList[1]; // Multistring (strings separated by '\0', terminated
// by '\0\0')
} AppExecLinkReparseBuffer;

// Dummy structure
struct {
UCHAR DataBuffer[1];
} GenericReparseBuffer;
} DUMMYUNIONNAME;
} REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER;

BOOL win_readlink(LPCWSTR symfile, LPWSTR buf, DWORD maxsize) {
HANDLE hFile = INVALID_HANDLE_VALUE;
REPARSE_DATA_BUFFER *respbuf = NULL;
DWORD dwBytes = 0;
LPWSTR wstr = NULL;
int wlen = 0;
BOOL ret = FALSE;
hFile = CreateFileW(
symfile, 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
NULL);
if (hFile == INVALID_HANDLE_VALUE) {
return FALSE;
}
respbuf = malloc(MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
if (DeviceIoControl(hFile, FSCTL_GET_REPARSE_POINT, NULL, 0, respbuf,
MAXIMUM_REPARSE_DATA_BUFFER_SIZE, &dwBytes,
NULL) != TRUE) {
CloseHandle(hFile);
free(respbuf);
return FALSE;
}
CloseHandle(hFile);
switch (respbuf->ReparseTag) {
case IO_REPARSE_TAG_SYMLINK: {
wstr = respbuf->SymbolicLinkReparseBuffer.PathBuffer +
(respbuf->SymbolicLinkReparseBuffer.SubstituteNameOffset /
sizeof(WCHAR));
wlen =
respbuf->SymbolicLinkReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
if (wlen >= 4 && wstr[0] == L'\\' && wstr[1] == L'?' && wstr[2] == L'?' &&
wstr[3] == L'\\') {
/* Starts with \??\ */
if (wlen >= 6 &&
((wstr[4] >= L'A' && wstr[4] <= L'Z') ||
(wstr[4] >= L'a' && wstr[4] <= L'z')) &&
wstr[5] == L':' && (wlen == 6 || wstr[6] == L'\\')) {
/* \??\<drive>:\ */
wstr += 4;
wlen -= 4;

} else if (wlen >= 8 && (wstr[4] == L'U' || wstr[4] == L'u') &&
(wstr[5] == L'N' || wstr[5] == L'n') &&
(wstr[6] == L'C' || wstr[6] == L'c') && wstr[7] == L'\\') {
/* \??\UNC\<server>\<share>\ - make sure the final path looks like */
/* \\<server>\<share>\ */
wstr += 6;
wstr[0] = L'\\';
wlen -= 6;
}
}
if (wlen >= maxsize) {
break;
}
wcsncpy(buf, wstr, wlen);
ret = TRUE;
} break;
case IO_REPARSE_TAG_MOUNT_POINT: {
wstr =
respbuf->MountPointReparseBuffer.PathBuffer +
(respbuf->MountPointReparseBuffer.SubstituteNameOffset / sizeof(WCHAR));
wlen =
respbuf->MountPointReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
/* Only treat junctions that look like \??\<drive>:\ as symlink. */
/* Junctions can also be used as mount points, like \??\Volume{<guid>}, */
/* but that's confusing for programs since they wouldn't be able to */
/* actually understand such a path when returned by uv_readlink(). */
/* UNC paths are never valid for junctions so we don't care about them. */
if (!(wlen >= 6 && wstr[0] == L'\\' && wstr[1] == L'?' && wstr[2] == L'?' &&
wstr[3] == L'\\' &&
((wstr[4] >= L'A' && wstr[4] <= L'Z') ||
(wstr[4] >= L'a' && wstr[4] <= L'z')) &&
wstr[5] == L':' && (wlen == 6 || wstr[6] == L'\\'))) {
SetLastError(ERROR_SYMLINK_NOT_SUPPORTED);
break;
}

/* Remove leading \??\ */
wstr += 4;
wlen -= 4;
if (wlen >= maxsize) {
break;
}
wcsncpy(buf, wstr, wlen);
ret = TRUE;
} break;
case IO_REPARSE_TAG_APPEXECLINK: {
if (respbuf->AppExecLinkReparseBuffer.StringCount != 0) {
LPWSTR szString = NULL, szTarget = NULL;
szString = (LPWSTR)respbuf->AppExecLinkReparseBuffer.StringList;
ULONG i = 0;
for (; i < respbuf->AppExecLinkReparseBuffer.StringCount; i++) {
if (i == 2) {
szTarget = szString;
}
szString += wcslen(szString) + 1;
}
if (wlen >= maxsize || szTarget == NULL) {
break;
}
wcsncpy(buf, szTarget, wlen);
ret = TRUE;
}
} break;
default:
break;
}
free(respbuf);
return ret;
}

static void find_exe_realpath(LPWSTR exepath, int count) {
WCHAR mdexe[MAX_PATH];
WCHAR mdexe[MAX_PATH], realexe[MAX_PATH];
HANDLE hFile = INVALID_HANDLE_VALUE;
DWORD dwlen = 0;
/* get the installation location */
GetModuleFileName(NULL, mdexe, MAX_PATH);
if (win_readlink(mdexe, exepath, count)) {
GetModuleFileNameW(NULL, mdexe, MAX_PATH);
hFile = CreateFileW(mdexe, // file to open
GENERIC_READ, // open for reading
FILE_SHARE_READ, // share for reading
NULL, // default security
OPEN_EXISTING, // existing file only
FILE_ATTRIBUTE_NORMAL, // normal file
NULL); // no attr. template
if (hFile == INVALID_HANDLE_VALUE) {
wcscpy(exepath, mdexe);
return;
}
wcscpy(exepath, mdexe);
return;
dwlen = GetFinalPathNameByHandleW(hFile, realexe, MAX_PATH, VOLUME_NAME_DOS);
if (dwlen >= MAX_PATH) {
wcscpy(exepath, mdexe);
} else {
wcsncpy(exepath, realexe + 4, dwlen - 4);
}
CloseHandle(hFile);
}


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