secure/stpncpy_chk.c

   1 /*
   2  * Copyright (c) 2010-2013 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include "secure.h"
  27
  28 char *
  29 __stpncpy_chk (char *restrict dest, char *restrict src,
  30                size_t len, size_t dstlen)
  31 {
  32   size_t n;
  33   char *retval;
  34
  35   if (__builtin_expect (dstlen < len, 0))
  36     __chk_fail_overflow ();
  37
  38   retval = stpncpy (dest, src, len); // Normally returns a pointer to the \0
  39   n = retval - dest + 1;
  40
  41   // Check if it's pointing to the location after the buffer after not writing \0
  42   if (n == len + 1)
  43     n--;
  44
  45   if (__builtin_expect (__chk_assert_no_overlap != 0, 1))
  46     __chk_overlap(dest, n, src, n);
  47
  48   return retval;
  49 }