mingw: refuse paths containing reserved names

There are a couple of reserved names that cannot be file names on
Windows, such as `AUX`, `NUL`, etc. For an almost complete list, see
https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file

If one would try to create a directory named `NUL`, it would actually
"succeed", i.e. the call would return success, but nothing would be
created.

Worse, even adding a file extension to the reserved name does not make
it a valid file name. To understand the rationale behind that behavior,
see https://devblogs.microsoft.com/oldnewthing/20031022-00/?p=42073

Let's just disallow them all.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin 2019-12-21 22:05:01 +00:00 committed by Junio C Hamano
parent 98d9b23e90
commit 4dc42c6c18
3 changed files with 110 additions and 18 deletions

View file

@ -393,7 +393,7 @@ int mingw_mkdir(const char *path, int mode)
int ret;
wchar_t wpath[MAX_PATH];
if (!is_valid_win32_path(path)) {
if (!is_valid_win32_path(path, 0)) {
errno = EINVAL;
return -1;
}
@ -479,7 +479,7 @@ int mingw_open (const char *filename, int oflags, ...)
mode = va_arg(args, int);
va_end(args);
if (!is_valid_win32_path(filename)) {
if (!is_valid_win32_path(filename, !create)) {
errno = create ? EINVAL : ENOENT;
return -1;
}
@ -550,14 +550,13 @@ FILE *mingw_fopen (const char *filename, const char *otype)
int hide = needs_hiding(filename);
FILE *file;
wchar_t wfilename[MAX_PATH], wotype[4];
if (!is_valid_win32_path(filename)) {
if (filename && !strcmp(filename, "/dev/null"))
wcscpy(wfilename, L"nul");
else if (!is_valid_win32_path(filename, 1)) {
int create = otype && strchr(otype, 'w');
errno = create ? EINVAL : ENOENT;
return NULL;
}
if (filename && !strcmp(filename, "/dev/null"))
wcscpy(wfilename, L"nul");
else if (xutftowcs_path(wfilename, filename) < 0)
} else if (xutftowcs_path(wfilename, filename) < 0)
return NULL;
if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
@ -580,14 +579,13 @@ FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream)
int hide = needs_hiding(filename);
FILE *file;
wchar_t wfilename[MAX_PATH], wotype[4];
if (!is_valid_win32_path(filename)) {
if (filename && !strcmp(filename, "/dev/null"))
wcscpy(wfilename, L"nul");
else if (!is_valid_win32_path(filename, 1)) {
int create = otype && strchr(otype, 'w');
errno = create ? EINVAL : ENOENT;
return NULL;
}
if (filename && !strcmp(filename, "/dev/null"))
wcscpy(wfilename, L"nul");
else if (xutftowcs_path(wfilename, filename) < 0)
} else if (xutftowcs_path(wfilename, filename) < 0)
return NULL;
if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
@ -2412,14 +2410,16 @@ static void setup_windows_environment(void)
}
}
int is_valid_win32_path(const char *path)
int is_valid_win32_path(const char *path, int allow_literal_nul)
{
const char *p = path;
int preceding_space_or_period = 0, i = 0, periods = 0;
if (!protect_ntfs)
return 1;
skip_dos_drive_prefix((char **)&path);
goto segment_start;
for (;;) {
char c = *(path++);
@ -2434,7 +2434,83 @@ int is_valid_win32_path(const char *path)
return 1;
i = periods = preceding_space_or_period = 0;
segment_start:
switch (*path) {
case 'a': case 'A': /* AUX */
if (((c = path[++i]) != 'u' && c != 'U') ||
((c = path[++i]) != 'x' && c != 'X')) {
not_a_reserved_name:
path += i;
continue;
}
break;
case 'c': case 'C': /* COM<N>, CON, CONIN$, CONOUT$ */
if ((c = path[++i]) != 'o' && c != 'O')
goto not_a_reserved_name;
c = path[++i];
if (c == 'm' || c == 'M') { /* COM<N> */
if (!isdigit(path[++i]))
goto not_a_reserved_name;
} else if (c == 'n' || c == 'N') { /* CON */
c = path[i + 1];
if ((c == 'i' || c == 'I') &&
((c = path[i + 2]) == 'n' ||
c == 'N') &&
path[i + 3] == '$')
i += 3; /* CONIN$ */
else if ((c == 'o' || c == 'O') &&
((c = path[i + 2]) == 'u' ||
c == 'U') &&
((c = path[i + 3]) == 't' ||
c == 'T') &&
path[i + 4] == '$')
i += 4; /* CONOUT$ */
} else
goto not_a_reserved_name;
break;
case 'l': case 'L': /* LPT<N> */
if (((c = path[++i]) != 'p' && c != 'P') ||
((c = path[++i]) != 't' && c != 'T') ||
!isdigit(path[++i]))
goto not_a_reserved_name;
break;
case 'n': case 'N': /* NUL */
if (((c = path[++i]) != 'u' && c != 'U') ||
((c = path[++i]) != 'l' && c != 'L') ||
(allow_literal_nul &&
!path[i + 1] && p == path))
goto not_a_reserved_name;
break;
case 'p': case 'P': /* PRN */
if (((c = path[++i]) != 'r' && c != 'R') ||
((c = path[++i]) != 'n' && c != 'N'))
goto not_a_reserved_name;
break;
default:
continue;
}
/*
* So far, this looks like a reserved name. Let's see
* whether it actually is one: trailing spaces, a file
* extension, or an NTFS Alternate Data Stream do not
* matter, the name is still reserved if any of those
* follow immediately after the actual name.
*/
i++;
if (path[i] == ' ') {
preceding_space_or_period = 1;
while (path[++i] == ' ')
; /* skip all spaces */
}
c = path[i];
if (c && c != '.' && c != ':' && c != '/' && c != '\\')
goto not_a_reserved_name;
/* contains reserved name */
return 0;
case '.':
periods++;
/* fallthru */

View file

@ -461,10 +461,17 @@ char *mingw_query_user_email(void);
*
* - contain any of the reserved characters, e.g. `:`, `;`, `*`, etc
*
* - correspond to reserved names (such as `AUX`, `PRN`, etc)
*
* The `allow_literal_nul` parameter controls whether the path `NUL` should
* be considered valid (this makes sense e.g. before opening files, as it is
* perfectly legitimate to open `NUL` on Windows, just as it is to open
* `/dev/null` on Unix/Linux).
*
* Returns 1 upon success, otherwise 0.
*/
int is_valid_win32_path(const char *path);
#define is_valid_path(path) is_valid_win32_path(path)
int is_valid_win32_path(const char *path, int allow_literal_nul);
#define is_valid_path(path) is_valid_win32_path(path, 0)
/**
* Converts UTF-8 encoded string to UTF-16LE.

View file

@ -470,6 +470,9 @@ test_expect_success MINGW 'is_valid_path() on Windows' '
"win32 x" \
../hello.txt \
C:\\git \
comm \
conout.c \
lptN \
\
--not \
"win32 " \
@ -477,7 +480,13 @@ test_expect_success MINGW 'is_valid_path() on Windows' '
"win32." \
"win32 . ." \
.../hello.txt \
colon:test
colon:test \
"AUX.c" \
"abc/conOut\$ .xyz/test" \
lpt8 \
"lpt*" \
Nul \
"PRN./abc"
'
test_done