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
|
/* $FreeBSD$ */
/*
* Arc4 random number generator for OpenBSD.
* Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
*
* Modification and redistribution in source and binary forms is
* permitted provided that due credit is given to the author and the
* OpenBSD project (for instance by leaving this copyright notice
* intact).
*/
/*
* This code is derived from section 17.1 of Applied Cryptography,
* second edition, which describes a stream cipher allegedly
* compatible with RSA Labs "RC4" cipher (the actual description of
* which is a trade secret). The same algorithm is used as a stream
* cipher called "arcfour" in Tatu Ylonen's ssh package.
*
* Here the stream cipher has been modified always to include the time
* when initializing the state. That makes it impossible to
* regenerate the same random sequence twice, so this can't be used
* for encryption, but will generate good random numbers.
*
* RC4 is a registered trademark of RSA Laboratories.
*/
#include "namespace.h"
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include "un-namespace.h"
struct arc4_stream {
u_int8_t i;
u_int8_t j;
u_int8_t s[256];
};
static int rs_initialized;
static struct arc4_stream rs;
static inline void
arc4_init(as)
struct arc4_stream *as;
{
int n;
for (n = 0; n < 256; n++)
as->s[n] = n;
as->i = 0;
as->j = 0;
}
static inline void
arc4_addrandom(as, dat, datlen)
struct arc4_stream *as;
u_char *dat;
int datlen;
{
int n;
u_int8_t si;
as->i--;
for (n = 0; n < 256; n++) {
as->i = (as->i + 1);
si = as->s[as->i];
as->j = (as->j + si + dat[n % datlen]);
as->s[as->i] = as->s[as->j];
as->s[as->j] = si;
}
}
static void
arc4_stir(as)
struct arc4_stream *as;
{
int fd;
struct {
struct timeval tv;
pid_t pid;
u_int8_t rnd[128 - sizeof(struct timeval) - sizeof(pid_t)];
} rdat;
gettimeofday(&rdat.tv, NULL);
rdat.pid = getpid();
fd = _open("/dev/urandom", O_RDONLY, 0);
if (fd >= 0) {
(void) _read(fd, rdat.rnd, sizeof(rdat.rnd));
_close(fd);
}
/* fd < 0? Ah, what the heck. We'll just take whatever was on the
* stack... */
arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
}
static inline u_int8_t
arc4_getbyte(as)
struct arc4_stream *as;
{
u_int8_t si, sj;
as->i = (as->i + 1);
si = as->s[as->i];
as->j = (as->j + si);
sj = as->s[as->j];
as->s[as->i] = sj;
as->s[as->j] = si;
return (as->s[(si + sj) & 0xff]);
}
static inline u_int32_t
arc4_getword(as)
struct arc4_stream *as;
{
u_int32_t val;
val = arc4_getbyte(as) << 24;
val |= arc4_getbyte(as) << 16;
val |= arc4_getbyte(as) << 8;
val |= arc4_getbyte(as);
return val;
}
void
arc4random_stir()
{
if (!rs_initialized) {
arc4_init(&rs);
rs_initialized = 1;
}
arc4_stir(&rs);
}
void
arc4random_addrandom(dat, datlen)
u_char *dat;
int datlen;
{
if (!rs_initialized)
arc4random_stir();
arc4_addrandom(&rs, dat, datlen);
}
u_int32_t
arc4random()
{
if (!rs_initialized)
arc4random_stir();
return arc4_getword(&rs);
}
#if 0
/*-------- Test code for i386 --------*/
#include <stdio.h>
#include <machine/pctr.h>
int
main(int argc, char **argv)
{
const int iter = 1000000;
int i;
pctrval v;
v = rdtsc();
for (i = 0; i < iter; i++)
arc4random();
v = rdtsc() - v;
v /= iter;
printf("%qd cycles\n", v);
}
#endif
|
