__strncat_chk.c revision 0a2301598c207fd1b50015984942fee5e8511593 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <string.h>
30#include <stdlib.h>
31#include <private/logd.h>
32
33/*
34 * Runtime implementation of __builtin____strncat_chk.
35 *
36 * See
37 *   http://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html
38 *   http://gcc.gnu.org/ml/gcc-patches/2004-09/msg02055.html
39 * for details.
40 *
41 * This strncat check is called if _FORTIFY_SOURCE is defined and
42 * greater than 0.
43 */
44char *__strncat_chk (char *dest, const char *src,
45              size_t len, size_t dest_buf_size)
46{
47    // TODO: optimize so we don't scan src/dest twice.
48    size_t dest_len = strlen(dest);
49    size_t src_len = strlen(src);
50    if (src_len > len) {
51        src_len = len;
52    }
53
54    if (dest_len + src_len + 1 > dest_buf_size) {
55        __libc_android_log_print(ANDROID_LOG_FATAL, "libc",
56            "*** strncat buffer overflow detected ***\n");
57        abort();
58    }
59
60    return strncat(dest, src, len);
61}
62