debug/vswprintf_chk.c

   1 /* Copyright (C) 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stdarg.h>
  19 #include <wchar.h>
  20 #include "../libio/libioP.h"
  21 #include "../libio/strfile.h"
  22
  23
  24 /* Write formatted output into S, according to the format
  25    string FORMAT, writing no more than MAXLEN characters.  */
  26 /* VARARGS5 */
  27 int
  28 __vswprintf_chk (wchar_t *s, size_t maxlen, int flags, size_t slen,
  29                  const wchar_t *format, va_list args)
  30 {
  31   /* XXX Maybe for less strict version do not fail immediately.
  32      Though, maxlen is supposed to be the size of buffer pointed
  33      to by s, so a conforming program can't pass such maxlen
  34      to *snprintf.  */
  35   if (__glibc_unlikely (slen < maxlen))
  36     __chk_fail ();
  37
  38   _IO_wstrnfile sf;
  39   struct _IO_wide_data wd;
  40   int ret;
  41 #ifdef _IO_MTSAFE_IO
  42   sf.f._sbf._f._lock = NULL;
  43 #endif
  44
  45   /* We need to handle the special case where MAXLEN is 0.  Use the
  46      overflow buffer right from the start.  */
  47   if (__glibc_unlikely (maxlen == 0))
  48     /* Since we have to write at least the terminating L'\0' a buffer
  49        length of zero always makes the function fail.  */
  50     return -1;
  51
  52   _IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, 0, &wd, &_IO_wstrn_jumps);
  53   _IO_fwide (&sf.f._sbf._f, 1);
  54   s[0] = L'\0';
  55
  56   /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
  57      can only come from read-only format strings.  */
  58   if (flags > 0)
  59     sf.f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
  60
  61   _IO_wstr_init_static (&sf.f._sbf._f, s, maxlen - 1, s);
  62   ret = _IO_vfwprintf ((_IO_FILE *) &sf.f._sbf, format, args);
  63
  64   if (sf.f._sbf._f._wide_data->_IO_buf_base == sf.overflow_buf)
  65     /* ISO C99 requires swprintf/vswprintf to return an error if the
  66        output does not fit int he provided buffer.  */
  67     return -1;
  68
  69   /* Terminate the string.  */
  70   *sf.f._sbf._f._wide_data->_IO_write_ptr = '\0';
  71
  72   return ret;
  73 }
  74 libc_hidden_def (__vswprintf_chk)