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Cygwin: path handling: never substitute virtual drive with target path 

Move the drive substitution code after the call to
GetFinalPathNameByHandleW into a local function revert_virtual_drive
and add code to handle non-remote virtual drives, i. e., those
created with the subst command.  (Try to) make sure that virtual
drives are never treated like symlinks.

Fixes: 19d59ce75d ("Cygwin: path_conv: Rework handling native symlinks as inner path components")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2022-12-12 21:56:14 +01:00
parent 45794e0d66
commit 5ba5e09b9d
1 changed files with 87 additions and 62 deletions
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149
winsup/cygwin/path.cc
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@ -3024,6 +3024,65 @@ symlink_info::parse_device (const char *contents)
return isdevice = true;
}
/* Probably we have a virtual drive input path and the resulting full path
starts with the substitution. Retrieve the target path of the virtual
drive and try to revert what GetFinalPathNameByHandleW did to the
drive letter. */
static bool
revert_virtual_drive (PUNICODE_STRING upath, PUNICODE_STRING fpath,
bool is_remote, ULONG ci_flag)
{
/* Get the drive's target path. */
WCHAR drive[3] = {(WCHAR) towupper (upath->Buffer[4]), L':', L'\0'};
WCHAR target[MAX_PATH];
UNICODE_STRING tpath;
WCHAR *p;
DWORD remlen = QueryDosDeviceW (drive, target, MAX_PATH);
if (remlen < 3)
return false;
remlen -= 2; /* Two L'\0' */
if (target[remlen - 1] == L'\\')
remlen--;
RtlInitCountedUnicodeString (&tpath, target, remlen * sizeof (WCHAR));
const USHORT uncp_len = is_remote ? ro_u_uncp.Length / sizeof (WCHAR) - 1 : 0;
if (is_remote)
{
/* target path starts with \??\UNC\. */
if (RtlEqualUnicodePathPrefix (&tpath, &ro_u_uncp, TRUE))
{
remlen -= uncp_len;
p = target + uncp_len;
}
/* target path starts with \Device\<redirector>. */
else if ((p = wcschr (target, L';'))
&& p + 3 < target + remlen
&& wcsncmp (p + 1, drive, 2) == 0
&& (p = wcschr (p + 3, L'\\')))
remlen -= p - target;
else
return false;
if (wcsncasecmp (fpath->Buffer + uncp_len, p, remlen))
return false;
}
else if (!RtlEqualUnicodePathPrefix (fpath, &tpath, TRUE))
return false;
/* Replace fpath with source drive letter and append reminder of
final path after skipping target path */
fpath->Buffer[4] = drive[0]; /* Drive letter */
fpath->Buffer[5] = L':';
WCHAR *to = fpath->Buffer + 6; /* Next to L':' */
WCHAR *from = fpath->Buffer + uncp_len + remlen;
memmove (to, from, (wcslen (from) + 1) * sizeof (WCHAR));
fpath->Length -= (from - to) * sizeof (WCHAR);
if (RtlEqualUnicodeString (upath, fpath, !!ci_flag))
return false;
return true;
}
/* Check if PATH is a symlink. PATH must be a valid Win32 path name.
If PATH is a symlink, put the value of the symlink--the file to
@ -3343,6 +3402,14 @@ restart:
continue;
}
/* Consider the situation where a virtual drive points to a native
symlink. Opening the virtual drive with FILE_OPEN_REPARSE_POINT
actually opens the symlink. If this symlink points to another
directory using a relative path, symlink evaluation goes totally
awry. We never want a virtual drive evaluated as symlink. */
if (upath.Length <= 14)
goto file_not_symlink;
/* Reparse points are potentially symlinks. This check must be
performed before checking the SYSTEM attribute for sysfile
symlinks, since reparse points can have this flag set, too. */
@ -3490,80 +3557,38 @@ restart:
RtlInitCountedUnicodeString (&fpath, fpbuf, ret * sizeof (WCHAR));
if (!RtlEqualUnicodeString (&upath, &fpath, !!ci_flag))
{
/* Check if the final path is an UNC path and the incoming
path isn't. If so... */
if (RtlEqualUnicodePathPrefix (&fpath, &ro_u_uncp, TRUE)
&& !RtlEqualUnicodePathPrefix (&upath, &ro_u_uncp, TRUE))
/* If the incoming path is a local drive letter path... */
if (!RtlEqualUnicodePathPrefix (&upath, &ro_u_uncp, TRUE))
{
/* ...get the remote path, replace remote path
with drive letter, check again. */
WCHAR drive[3] =
{(WCHAR) towupper (upath.Buffer[4]), L':', L'\0'};
WCHAR remote[MAX_PATH];
DWORD remlen = QueryDosDeviceW (drive, remote, MAX_PATH);
if (remlen < 3)
goto file_not_symlink; /* fallback */
remlen -= 2; /* Two L'\0' */
if (remote[remlen - 1] == L'\\')
remlen--;
WCHAR *p;
UNICODE_STRING rpath;
RtlInitCountedUnicodeString (&rpath, remote,
remlen * sizeof (WCHAR));
const USHORT uncp_len =
ro_u_uncp.Length / sizeof (WCHAR) - 1;
if (RtlEqualUnicodePathPrefix (&rpath, &ro_u_uncp, TRUE))
/* ...and the final path is an UNC path, revert to the
drive letter path syntax. */
if (RtlEqualUnicodePathPrefix (&fpath, &ro_u_uncp, TRUE))
{
remlen -= uncp_len;
p = remote + uncp_len;
if (!revert_virtual_drive (&upath, &fpath, true,
ci_flag))
goto file_not_symlink;
}
/* ...otherwise, if the final path changes the drive
letter, let revert_virtual_drive check for a
virtual drive and revert that. */
else if (upath.Buffer[5] == L':'
&& (WCHAR) towupper (upath.Buffer[4])
!= (WCHAR) towupper (fpath.Buffer[4]))
{
if (!revert_virtual_drive (&upath, &fpath, false,
ci_flag))
goto file_not_symlink;
}
else if ((p = wcschr (remote, L';'))
&& p + 3 < remote + remlen
&& wcsncmp (p + 1, drive, 2) == 0
&& (p = wcschr (p + 3, L'\\')))
remlen -= p - remote;
else
goto file_not_symlink; /* fallback */
if (wcsncasecmp (fpath.Buffer + uncp_len, p, remlen))
goto file_not_symlink; /* fallback (not expected) */
/* Hackfest */
fpath.Buffer[4] = drive[0]; /* Drive letter */
fpath.Buffer[5] = L':';
WCHAR *to = fpath.Buffer + 6; /* Next to L':' */
WCHAR *from = fpath.Buffer + uncp_len + remlen;
memmove (to, from,
(wcslen (from) + 1) * sizeof (WCHAR));
fpath.Length -= (from - to) * sizeof (WCHAR);
if (RtlEqualUnicodeString (&upath, &fpath, !!ci_flag))
goto file_not_symlink;
}
issymlink = true;
/* upath.Buffer is big enough and unused from this point on.
Reuse it here, avoiding yet another buffer allocation. */
char *nfpath = (char *) upath.Buffer;
sys_wcstombs (nfpath, NT_MAX_PATH, fpbuf);
res = posixify (nfpath);
/* If the incoming path consisted of a drive prefix only,
we just handle a virtual drive, created with, e.g.
subst X: C:\foo\bar
Treat it like a symlink. This is required to tell an
lstat caller that the "drive" is actually pointing
somewhere else, thus, it's a symlink in POSIX speak. */
if (upath.Length == 14) /* \??\X:\ */
{
fileattr &= ~FILE_ATTRIBUTE_DIRECTORY;
path_flags |= PATH_SYMLINK;
}
/* For final paths differing in inner path components return
length as negative value. This informs path_conv::check
to skip realpath handling on the last path component. */
else
res = -res;
res = -posixify (nfpath);
break;
}
}