secure/strcat_chk.c

   1 /*
   2  * Copyright (c) 2007 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 <stdio.h>
  27
  28 extern void __chk_fail (void) __attribute__((__noreturn__));
  29
  30 char *
  31 __strcat_chk (char *__restrict s, const char *__restrict append,
  32               size_t slen)
  33 {
  34   char *save = s;
  35
  36   /* Advance to the end. */
  37   for (; *s; ++s)
  38     if (__builtin_expect (slen-- == 0, 0))
  39       __chk_fail ();
  40
  41   do
  42     {
  43       /* Append the string.  Make sure we check before writing.  */
  44       if (__builtin_expect (slen-- == 0, 0))
  45         __chk_fail ();
  46
  47     } while (*s++ = *append++);
  48
  49   return save;
  50
  51 }