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
48uint32_t key[MAX_KEY_STR_LEN];
49
50char *filename = "mangledata";
51
52int key_fd = -1;
53void
54init_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
90void
91fini_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
112void
113dump_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
122char validchars[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
123#define NUM_KEYS (sizeof(validchars)-1)
124
125void
126mangle_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