1/*-
2 * Copyright (c) 2015 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#include <stdlib.h>
30#include <string.h>
31
32#include "_libpe.h"
33
34ELFTC_VCSID("$Id: libpe_rich.c 3312 2016-01-10 09:23:51Z kaiwang27 $");
35
36static char *
37memfind(char *s, const char *find, size_t slen, size_t flen)
38{
39	int i;
40
41	if (slen == 0 || flen == 0 || flen > slen)
42		return (NULL);
43
44	for (i = 0; (size_t) i <= slen - flen; i++) {
45		if (s[i] != find[0])
46			continue;
47		if (flen == 1)
48			return (&s[i]);
49		if (memcmp(&s[i + 1], &find[1], flen - 1) == 0)
50			return (&s[i]);
51	}
52
53	return (NULL);
54}
55
56int
57libpe_parse_rich_header(PE *pe)
58{
59	PE_RichHdr *rh;
60	char *p, *r, *s;
61	uint32_t x;
62	int found, i;
63
64	assert(pe->pe_stub != NULL && pe->pe_stub_ex > 0);
65
66	/* Search for the "Rich" keyword to locate the Rich header. */
67	s = pe->pe_stub + sizeof(PE_DosHdr);
68	r = memfind(s, PE_RICH_TEXT, pe->pe_stub_ex, 4);
69	if (r == NULL || r + 8 > s + pe->pe_stub_ex) {
70		errno = ENOENT;
71		return (-1);
72	}
73
74	if ((rh = calloc(1, sizeof(*rh))) == NULL) {
75		errno = ENOMEM;
76		return (-1);
77	}
78
79	rh->rh_xor = le32dec(r + 4); /* Retrieve the "XOR mask" */
80
81	/*
82	 * Search for the hidden keyword "DanS" by XOR the dwords before
83	 * the "Rich" keyword with the XOR mask.
84	 */
85	found = 0;
86	for (p = r - 4; p >= s; p -= 4) {
87		x = le32dec(p) ^ rh->rh_xor;
88		if (x == PE_RICH_HIDDEN) {
89			found = 1;
90			break;
91		}
92	}
93	if (!found) {
94		free(rh);
95		errno = ENOENT;
96		return (-1);
97	}
98
99	/*
100	 * Found the "DanS" keyword, which is the start of the Rich header.
101	 * The next step is to skip the first 16 bytes (DanS, XOR mask,
102	 * XOR mask, XOR mask) and read the (compid,cnt) tuples.
103	 */
104	pe->pe_rh_start = p;
105	p += 16;
106	rh->rh_total = (r - p) / 8;
107	if ((rh->rh_compid = malloc(rh->rh_total * sizeof(*rh->rh_compid))) ==
108	    NULL) {
109		free(rh);
110		errno = ENOMEM;
111		return (-1);
112	}
113	if ((rh->rh_cnt = malloc(rh->rh_total * sizeof(*rh->rh_cnt))) ==
114	    NULL) {
115		free(rh->rh_compid);
116		free(rh);
117		errno = ENOMEM;
118		return (-1);
119	}
120	for (i = 0; (uint32_t) i < rh->rh_total; i++, p += 8) {
121		rh->rh_compid[i] = le32dec(p) ^ rh->rh_xor;
122		rh->rh_cnt[i] = le32dec(p + 4) ^ rh->rh_xor;
123	}
124
125	pe->pe_rh = rh;
126
127	return (0);
128}
129