freebsd-dev/lib/libc/string/wcsxfrm.c
Dimitry Andric aa8d126847 Fix a possible segfault in wcsxfrm(3) and wcsxfrm_l(3).
If the length of the source wide character string, passed in via the
"size_t n" parameter, is set to zero, the function should only return
the required length for the destination wide character string.  In this
case, it should *not* attempt to write to the destination, so the "dst"
parameter is permitted to be NULL.

However, when the internally called _collate_wxfrm() function returns an
error, such as when using the "C" locale, as a fallback wcscpy(3) or
wcsncpy(3) are used.  But if the input length is zero, wcsncpy(3) will
be called with a length of -1!  If the "dst" parameter is NULL, this
will immediately result in a segfault, or if "dst" is a valid pointer,
it will most likely result in unexpectedly overwritten memory.

Fix this by explicitly checking for an input length greater than zero,
before calling wcsncpy(3).

Note that a similar situation does not occur in strxfrm(3), the plain
character version of this function, as it uses strlcpy(3) for the error
case.  The strlcpy(3) function does not write to the destination if the
input length is zero.

MFC after:	1 week
2019-08-07 20:13:43 +00:00

88 lines
2.7 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright 2010 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 1995 Alex Tatmanjants <alex@elvisti.kiev.ua>
* at Electronni Visti IA, Kiev, Ukraine.
* All rights reserved.
*
* Copyright (c) 2011 The FreeBSD Foundation
* All rights reserved.
* Portions of this software were developed by David Chisnall
* under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#include "collate.h"
size_t
wcsxfrm_l(wchar_t * __restrict dest, const wchar_t * __restrict src, size_t len, locale_t locale)
{
size_t slen;
FIX_LOCALE(locale);
struct xlocale_collate *table =
(struct xlocale_collate*)locale->components[XLC_COLLATE];
if (*src == L'\0') {
if (len != 0)
*dest = L'\0';
return (0);
}
if ((table->__collate_load_error) ||
((slen = _collate_wxfrm(table, src, dest, len)) == (size_t)-1)) {
goto error;
}
/* Add null termination at the correct location. */
if (len > slen) {
dest[slen] = 0;
} else if (len) {
dest[len-1] = 0;
}
return (slen);
error:
slen = wcslen(src);
if (slen < len)
(void) wcscpy(dest, src);
else if (len > 0) {
(void) wcsncpy(dest, src, len - 1);
dest[len - 1] = L'\0';
}
return (slen);
}
size_t
wcsxfrm(wchar_t * __restrict dest, const wchar_t * __restrict src, size_t len)
{
return wcsxfrm_l(dest, src, len, __get_locale());
}