1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
// **************************************************************************
// * 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) ZenJu (zhnmju123 AT gmx DOT de) - All Rights Reserved *
// **************************************************************************
#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
namespace zen
{
#ifdef FFS_WIN
bool isSymlink(const WIN32_FIND_DATA& data); //*not* a simple FILE_ATTRIBUTE_REPARSE_POINT check!
bool isSymlink(DWORD fileAttributes, DWORD reparseTag);
#endif
Zstring getSymlinkRawTargetString(const Zstring& linkPath); //throw FileError
}
//################################ implementation ################################
#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_impl(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
//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(),
GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
nullptr,
OPEN_EXISTING,
FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
nullptr);
if (hLink == INVALID_HANDLE_VALUE)
throw FileError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtFileName(linkPath)) + L"\n\n" + getLastErrorFormatted());
ZEN_ON_SCOPE_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 = 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 FileError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtFileName(linkPath)) + L"\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(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtFileName(linkPath)) + L"\n\n" + L"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 = replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtFileName(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
}
}
namespace zen
{
inline
Zstring getSymlinkRawTargetString(const Zstring& linkPath) { return getSymlinkRawTargetString_impl(linkPath); }
#ifdef FFS_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_WIN_H_INCLUDED
|
