[PATCH v2 2/2] mingw: fix getcwd when the parent directory cannot be queried
From: Anton Serbulov <aserbulov@plesk.com>
`GetLongPathName()` function may fail when it is unable to query the parent directory of a path component to determine the long name for that component. It happens, because it uses `FindFirstFile()` function for each next short part of path. The `FindFirstFile()` requires `List Directory` and `Synchronize` desired access for a calling process.
In case of lacking such permission for some part of path, the `GetLongPathName()` returns 0 as result and `GetLastError()` returns ERROR_ACCESS_DENIED.
`GetFinalPathNameByHandle()` function can help in such cases, because it requires `Read Attributes` and `Synchronize` desired access to the target path only.
The `GetFinalPathNameByHandle()` function was introduced on `Windows Server 2008/Windows Vista`. So we need to load it dynamically.
`CreateFile()` parameters:
`lpFileName` = path to the current directory
`dwDesiredAccess` = 0 (it means `Read Attributes` and `Synchronize`)
`dwShareMode` = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
(it prevents `Sharing Violation`)
`lpSecurityAttributes` = NULL (default security attributes)
`dwCreationDisposition` = OPEN_EXISTING
(required to obtain a directory handle)
`dwFlagsAndAttributes` = FILE_FLAG_BACKUP_SEMANTICS
(required to obtain a directory handle)
`hTemplateFile` = NULL (when opening an existing file or directory,
`CreateFile` ignores this parameter)The string that is returned by `GetFinalPathNameByHandle()` function uses the \\?\ syntax. To skip the prefix and convert backslashes to slashes, the `normalize_ntpath()` mingw function will be used.
Note: `GetFinalPathNameByHandle()` function returns a final path.
It is the path that is returned when a path is fully resolved.
For example, for a symbolic link named "C:\tmp\mydir" that points to
"D:\yourdir", the final path would be "D:\yourdir".
Signed-off-by: Anton Serbulov <aserbulov@plesk.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
compat/mingw.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
Show changes to compat/mingw.c +39 −0
diff --git a/compat/mingw.c b/compat/mingw.c
index 2c3e27ce9..19addfa5d 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -202,6 +202,31 @@ static int ask_yes_no_if_possible(const char *format, ...)
}
}
+/* Normalizes NT paths as returned by some low-level APIs. */
+static wchar_t *normalize_ntpath(wchar_t *wbuf)
+{
+ int i;
+ /* fix absolute path prefixes */
+ if (wbuf[0] == '\\') {
+ /* strip NT namespace prefixes */
+ if (!wcsncmp(wbuf, L"\\??\\", 4) ||
+ !wcsncmp(wbuf, L"\\\\?\\", 4))
+ wbuf += 4;
+ else if (!wcsnicmp(wbuf, L"\\DosDevices\\", 12))
+ wbuf += 12;
+ /* replace remaining '...UNC\' with '\\' */
+ if (!wcsnicmp(wbuf, L"UNC\\", 4)) {
+ wbuf += 2;
+ *wbuf = '\\';
+ }
+ }
+ /* convert backslashes to slashes */
+ for (i = 0; wbuf[i]; i++)
+ if (wbuf[i] == '\\')
+ wbuf[i] = '/';
+ return wbuf;
+}
+
int mingw_unlink(const char *pathname)
{
int ret, tries = 0;
@@ -925,6 +950,20 @@ char *mingw_getcwd(char *pointer, int len)
return NULL;
}
ret = GetLongPathNameW(cwd, wpointer, ARRAY_SIZE(wpointer));
+ if (!ret && GetLastError() == ERROR_ACCESS_DENIED) {
+ HANDLE hnd = CreateFileW(cwd, 0,
+ FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
+ OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+ if (hnd == INVALID_HANDLE_VALUE)
+ return NULL;
+ ret = GetFinalPathNameByHandleW(hnd, wpointer, ARRAY_SIZE(wpointer), 0);
+ CloseHandle(hnd);
+ if (!ret || ret >= ARRAY_SIZE(wpointer))
+ return NULL;
+ if (xwcstoutf(pointer, normalize_ntpath(wpointer), len) < 0)
+ return NULL;
+ return pointer;
+ }
if (!ret || ret >= ARRAY_SIZE(wpointer))
return NULL;
if (xwcstoutf(pointer, wpointer, len) < 0)
--
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