1 /*-
2  * Copyright (c) 2006,2008 Joseph Koshy
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  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  */
26 
27 #include <gelf.h>
28 
29 #include "_libelf.h"
30 
31 ELFTC_VCSID("$Id: libelf_checksum.c 3174 2015-03-27 17:13:41Z emaste $");
32 
33 static unsigned long
34 _libelf_sum(unsigned long c, const unsigned char *s, size_t size)
35 {
36 	if (s == NULL || size == 0)
37 		return (c);
38 
39 	while (size--)
40 		c += *s++;
41 
42 	return (c);
43 }
44 
45 long
46 _libelf_checksum(Elf *e, int elfclass)
47 {
48 	size_t shn;
49 	Elf_Scn *scn;
50 	Elf_Data *d;
51 	unsigned long checksum;
52 	GElf_Ehdr eh;
53 	GElf_Shdr shdr;
54 
55 	if (e == NULL) {
56 		LIBELF_SET_ERROR(ARGUMENT, 0);
57 		return (0L);
58 	}
59 
60 	if (e->e_class != elfclass) {
61 		LIBELF_SET_ERROR(CLASS, 0);
62 		return (0L);
63 	}
64 
65 	if (gelf_getehdr(e, &eh) == NULL)
66 		return (0);
67 
68 	/*
69 	 * Iterate over all sections in the ELF file, computing the
70 	 * checksum along the way.
71 	 *
72 	 * The first section is always SHN_UNDEF and can be skipped.
73 	 * Non-allocatable sections are skipped, as are sections that
74 	 * could be affected by utilities such as strip(1).
75 	 */
76 
77 	checksum = 0;
78 	for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
79 		if ((scn = elf_getscn(e, shn)) == NULL)
80 			return (0);
81 		if (gelf_getshdr(scn, &shdr) == NULL)
82 			return (0);
83 		if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
84 		    shdr.sh_type == SHT_DYNAMIC ||
85 		    shdr.sh_type == SHT_DYNSYM)
86 			continue;
87 
88 		d = NULL;
89 		while ((d = elf_rawdata(scn, d)) != NULL)
90 			checksum = _libelf_sum(checksum,
91 			    (unsigned char *) d->d_buf, (size_t) d->d_size);
92 	}
93 
94 	/*
95 	 * Return a 16-bit checksum compatible with Solaris.
96 	 */
97 	return (long) (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
98 }
99