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 
34 ELFTC_VCSID("$Id: libpe_rich.c 3312 2016-01-10 09:23:51Z kaiwang27 $");
35 
36 static char *
37 memfind(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 
56 int
57 libpe_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