1 /* $OpenBSD: mangle.c,v 1.2 2009/12/08 21:10:24 drahn Exp $ */
2 /*
3 * Copyright (c) 2009 Dale Rahn.
4 * All rights reserved.
5 *
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #include <sys/types.h>
29 #include <sys/stat.h>
30 #include <fcntl.h>
31 #include <unistd.h>
32 #include <stdio.h>
33 #include <string.h>
34 #include "mangle.h"
35
36 /*
37 * supports randomizing up to 32 characters, if an identifier is longer than
38 * 32 characters, we only modify the first 32 characters of it.
39 *
40 * However not all of the 32 characters will really be randomized as
41 * 2^32 (uint32_t gives a maximum string of cmpPQeaa[a]*
42 * Dont thing this will really matter....
43 *
44 * HOWEVER this does not mean we want to change the MAX_KEY_STR_LEN to 6
45 * because then all strings len >= 6 would use from the same index pool.
46 */
47 #define MAX_KEY_STR_LEN 32
48 uint32_t key[MAX_KEY_STR_LEN];
49
50 char *filename = "mangledata";
51
52 int key_fd = -1;
53 void
init_mangle_state()54 init_mangle_state()
55 {
56 int failed = 0;
57 ssize_t len;
58 int i, ret;
59
60 /* open file if it exists, else init to zeros */
61 struct stat sb;
62
63 ret = stat(filename, &sb);
64
65 if (ret != -1 && sb.st_size == sizeof(key)) {
66 key_fd = open(filename, O_RDWR);
67 }
68
69 if (ret == -1 || key_fd == -1)
70 failed = 1;
71
72 if (failed == 0) {
73 len = read(key_fd, key, sizeof(key));
74 if (len != sizeof(key)) {
75 failed = 1;
76 }
77 }
78
79 if (failed == 1) {
80 if (key_fd != -1) {
81 close(key_fd);
82 key_fd = -1;
83 }
84 for (i = 0; i < MAX_KEY_STR_LEN; i++) {
85 key[i] = 0;
86 }
87 }
88 }
89
90 void
fini_mangle_state()91 fini_mangle_state()
92 {
93 int len;
94 if (key_fd == -1) {
95 /* open file for create/truncate */
96 key_fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0666);
97 } else {
98 /* seek to the beginning */
99 lseek(key_fd, 0, SEEK_SET);
100 }
101 if (key_fd != -1) {
102 /* write file */
103 len = write(key_fd, key, sizeof(key));
104 if (len != sizeof(key)) {
105 printf("writing file failed\n");
106 }
107 close(key_fd);
108 key_fd = -1;
109 }
110 }
111
112 void
dump_mangle_state()113 dump_mangle_state()
114 {
115 int i;
116
117 for (i = 0; i < MAX_KEY_STR_LEN; i++) {
118 printf("key %d %d\n", i, key[i]);
119 }
120 }
121
122 char validchars[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
123 #define NUM_KEYS (sizeof(validchars)-1)
124
125 void
mangle_str(char * str)126 mangle_str(char *str)
127 {
128 int i;
129 int len;
130 int keyval;
131
132 len = strlen(str);
133 if (len == 0)
134 return; /* nothing to mangle */
135
136 if (len > MAX_KEY_STR_LEN)
137 len = MAX_KEY_STR_LEN;
138
139 keyval = key[len-1]++;
140
141 for (i = 0; i < len; i++) {
142 int idx = keyval % NUM_KEYS;
143 keyval = keyval / NUM_KEYS;
144 str[i] = validchars[idx];
145
146 }
147 }
148
149