1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
|
/*
** OSSP uuid - Universally Unique Identifier
** Copyright (c) 2004-2006 Ralf S. Engelschall <rse@engelschall.com>
** Copyright (c) 2004-2006 The OSSP Project <http://www.ossp.org/>
**
** This file is part of OSSP uuid, a library for the generation
** of UUIDs which can found at http://www.ossp.org/pkg/lib/uuid/
**
** Permission to use, copy, modify, and distribute this software for
** any purpose with or without fee is hereby granted, provided that
** the above copyright notice and this permission notice appear in all
** copies.
**
** THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
** WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
** IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR
** CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
** USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
** OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
** SUCH DAMAGE.
**
** uuid_prng.c: PRNG API implementation
*/
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>
#include <fcntl.h>
#include "uuid_prng.h"
#include "uuid_md5.h"
struct prng_st {
int dev; /* system PRNG device */
md5_t *md5; /* local MD5 PRNG engine */
long cnt; /* time resolution compensation counter */
};
prng_rc_t prng_create(prng_t **prng)
{
int fd = -1;
struct timeval tv;
pid_t pid;
unsigned int i;
/* sanity check argument(s) */
if (prng == NULL)
return PRNG_RC_ARG;
/* allocate object */
if ((*prng = (prng_t *)malloc(sizeof(prng_t))) == NULL)
return PRNG_RC_MEM;
/* try to open the system PRNG device */
(*prng)->dev = -1;
if ((fd = open("/dev/urandom", O_RDONLY)) == -1)
fd = open("/dev/random", O_RDONLY|O_NONBLOCK);
if (fd != -1) {
(void)fcntl(fd, F_SETFD, FD_CLOEXEC);
(*prng)->dev = fd;
}
/* initialize MD5 engine */
if (md5_create(&((*prng)->md5)) != MD5_RC_OK) {
free(*prng);
return PRNG_RC_INT;
}
/* initialize time resolution compensation counter */
(*prng)->cnt = 0;
/* seed the C library PRNG once */
(void)gettimeofday(&tv, NULL);
pid = getpid();
srand((unsigned int)(
((unsigned int)pid << 16)
^ (unsigned int)pid
^ (unsigned int)tv.tv_sec
^ (unsigned int)tv.tv_usec));
for (i = (unsigned int)((tv.tv_sec ^ tv.tv_usec) & 0x1F); i > 0; i--)
(void)rand();
return PRNG_RC_OK;
}
prng_rc_t prng_data(prng_t *prng, void *data_ptr, size_t data_len)
{
size_t n;
unsigned char *p;
struct {
struct timeval tv;
long cnt;
int rnd;
} entropy;
unsigned char md5_buf[MD5_LEN_BIN];
unsigned char *md5_ptr;
size_t md5_len;
int retries;
int i;
/* sanity check argument(s) */
if (prng == NULL || data_len == 0)
return PRNG_RC_ARG;
/* prepare for generation */
p = (unsigned char *)data_ptr;
n = data_len;
/* approach 1: try to gather data via stronger system PRNG device */
if (prng->dev != -1) {
retries = 0;
while (n > 0) {
i = (int)read(prng->dev, (void *)p, n);
if (i <= 0) {
if (retries++ > 16)
break;
continue;
}
retries = 0;
n -= (unsigned int)i;
p += (unsigned int)i;
}
}
/* approach 2: try to gather data via weaker libc PRNG API. */
while (n > 0) {
/* gather new entropy */
(void)gettimeofday(&(entropy.tv), NULL); /* source: libc time */
entropy.rnd = rand(); /* source: libc PRNG */
entropy.cnt = prng->cnt++; /* source: local counter */
/* pass entropy into MD5 engine */
if (md5_update(prng->md5, (void *)&entropy, sizeof(entropy)) != MD5_RC_OK)
return PRNG_RC_INT;
/* store MD5 engine state as PRN output */
md5_ptr = md5_buf;
md5_len = sizeof(md5_buf);
if (md5_store(prng->md5, (void **)(void *)&md5_ptr, &md5_len) != MD5_RC_OK)
return PRNG_RC_INT;
for (i = 0; i < MD5_LEN_BIN && n > 0; i++, n--)
*p++ ^= md5_buf[i]; /* intentionally no assignment because arbitrary
caller buffer content is leveraged, too */
}
return PRNG_RC_OK;
}
prng_rc_t prng_destroy(prng_t *prng)
{
/* sanity check argument(s) */
if (prng == NULL)
return PRNG_RC_ARG;
/* close PRNG device */
if (prng->dev != -1)
(void)close(prng->dev);
/* destroy MD5 engine */
(void)md5_destroy(prng->md5);
/* free object */
free(prng);
return PRNG_RC_OK;
}
|
