pe_rich.c revision 303975 
1/*-
2 * Copyright (c) 2016 Kai Wang
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 <assert.h>
28#include <errno.h>
29
30#include "_libpe.h"
31
32ELFTC_VCSID("$Id: pe_rich.c 3312 2016-01-10 09:23:51Z kaiwang27 $");
33
34PE_RichHdr *
35pe_rich_header(PE *pe)
36{
37
38	if (pe == NULL) {
39		errno = EINVAL;
40		return (NULL);
41	}
42
43	if (pe->pe_rh == NULL && pe->pe_stub_ex > 0 &&
44	    (pe->pe_flags & LIBPE_F_LOAD_DOS_STUB) == 0) {
45		assert((pe->pe_flags & LIBPE_F_SPECIAL_FILE) == 0);
46		(void) libpe_read_msdos_stub(pe);
47	}
48
49	if (pe->pe_rh == NULL) {
50		errno = ENOENT;
51		return (NULL);
52	}
53
54	return (pe->pe_rh);
55}
56
57static uint32_t
58rol32(uint32_t n, int c)
59{
60
61	c &= 0x1f;
62
63	return ((n << c) | (n >> (0x20 - c)));
64}
65
66int
67pe_rich_header_validate(PE *pe)
68{
69	PE_RichHdr *rh;
70	uint32_t cksum;
71	char *p;
72	int i, off;
73
74	if (pe_rich_header(pe) == NULL)
75		return (-1);
76
77	assert(pe->pe_rh_start != NULL);
78
79	/*
80	 * Initial value of the checksum is the offset to the begin of
81	 * the Rich header.
82	 */
83	cksum = pe->pe_rh_start - pe->pe_stub;
84
85	/*
86	 * Add the bytes before the Rich header to the checksum, rotated
87	 * left by the offset.
88	 */
89	for (p = pe->pe_stub; p < pe->pe_rh_start; p++) {
90		/* Skip dh_lfanew. */
91		off = p - pe->pe_stub;
92		if (off >= 0x3c && off < 0x40)
93			continue;
94		cksum += rol32((unsigned char) *p, off);
95	}
96
97	/* Add each compid rotated left by its count to the checksum. */
98	rh = pe->pe_rh;
99	for (i = 0; (uint32_t) i < rh->rh_total; i++)
100		cksum += rol32(rh->rh_compid[i], rh->rh_cnt[i]);
101
102	/* Validate the checksum with the XOR mask stored after "Rich". */
103	if (cksum == rh->rh_xor)
104		return (1);
105
106	return (0);
107}
108