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
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
|
/* $OpenBSD: ip6_id.c,v 1.13 2017/09/08 05:36:53 deraadt Exp $ */
/* $NetBSD: ip6_id.c,v 1.7 2003/09/13 21:32:59 itojun Exp $ */
/* $KAME: ip6_id.c,v 1.8 2003/09/06 13:41:06 itojun Exp $ */
/*
* Copyright (C) 2003 WIDE Project.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the project nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS 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 PROJECT OR 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.
*/
/*
* Copyright 1998 Niels Provos <provos@citi.umich.edu>
* All rights reserved.
*
* Theo de Raadt <deraadt@openbsd.org> came up with the idea of using
* such a mathematical system to generate more random (yet non-repeating)
* ids to solve the resolver/named problem. But Niels designed the
* actual system based on the constraints.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 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 AUTHOR 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.
*/
/*
* seed = random (bits - 1) bit
* n = prime, g0 = generator to n,
* j = random so that gcd(j,n-1) == 1
* g = g0^j mod n will be a generator again.
*
* X[0] = random seed.
* X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator
* with a = 7^(even random) mod m,
* b = random with gcd(b,m) == 1
* m = constant and a maximal period of m-1.
*
* The transaction id is determined by:
* id[n] = seed xor (g^X[n] mod n)
*
* Effectivly the id is restricted to the lower (bits - 1) bits, thus
* yielding two different cycles by toggling the msb on and off.
* This avoids reuse issues caused by reseeding.
*/
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/socket.h>
#include <sys/systm.h>
#include <netinet/in.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
struct randomtab {
const int ru_bits; /* resulting bits */
const long ru_out; /* Time after wich will be reseeded */
const u_int32_t ru_max; /* Uniq cycle, avoid blackjack prediction */
const u_int32_t ru_gen; /* Starting generator */
const u_int32_t ru_n; /* ru_n: prime, ru_n - 1: product of pfacts[] */
const u_int32_t ru_agen; /* determine ru_a as ru_agen^(2*rand) */
const u_int32_t ru_m; /* ru_m = 2^x*3^y */
const u_int32_t pfacts[4]; /* factors of ru_n */
u_int32_t ru_counter;
u_int32_t ru_msb;
u_int32_t ru_x;
u_int32_t ru_seed, ru_seed2;
u_int32_t ru_a, ru_b;
u_int32_t ru_g;
long ru_reseed;
};
static struct randomtab randomtab_20 = {
20, /* resulting bits */
180, /* Time after wich will be reseeded */
200000, /* Uniq cycle, avoid blackjack prediction */
2, /* Starting generator */
524269, /* RU_N-1 = 2^2*3^2*14563 */
7, /* determine ru_a as RU_AGEN^(2*rand) */
279936, /* RU_M = 2^7*3^7 - don't change */
{ 2, 3, 14563, 0 }, /* factors of ru_n */
};
u_int32_t ip6id_pmod(u_int32_t, u_int32_t, u_int32_t);
void ip6id_initid(struct randomtab *);
u_int32_t ip6id_randomid(struct randomtab *);
/*
* Do a fast modular exponation, returned value will be in the range
* of 0 - (mod-1)
*/
u_int32_t
ip6id_pmod(u_int32_t gen, u_int32_t expo, u_int32_t mod)
{
u_int64_t s, t, u;
s = 1;
t = gen;
u = expo;
while (u) {
if (u & 1)
s = (s * t) % mod;
u >>= 1;
t = (t * t) % mod;
}
return (s);
}
/*
* Initializes the seed and chooses a suitable generator. Also toggles
* the msb flag. The msb flag is used to generate two distinct
* cycles of random numbers and thus avoiding reuse of ids.
*
* This function is called from id_randomid() when needed, an
* application does not have to worry about it.
*/
void
ip6id_initid(struct randomtab *p)
{
u_int32_t j, i;
int noprime = 1;
p->ru_x = arc4random_uniform(p->ru_m);
/* (bits - 1) bits of random seed */
p->ru_seed = arc4random() & (~0U >> (32 - p->ru_bits + 1));
p->ru_seed2 = arc4random() & (~0U >> (32 - p->ru_bits + 1));
/* Determine the LCG we use */
p->ru_b = (arc4random() & (~0U >> (32 - p->ru_bits))) | 1;
p->ru_a = ip6id_pmod(p->ru_agen,
(arc4random() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m);
while (p->ru_b % 3 == 0)
p->ru_b += 2;
j = arc4random_uniform(p->ru_n);
/*
* Do a fast gcd(j, RU_N - 1), so we can find a j with
* gcd(j, RU_N - 1) == 1, giving a new generator for
* RU_GEN^j mod RU_N
*/
while (noprime) {
for (i = 0; p->pfacts[i] > 0; i++)
if (j % p->pfacts[i] == 0)
break;
if (p->pfacts[i] == 0)
noprime = 0;
else
j = (j + 1) % p->ru_n;
}
p->ru_g = ip6id_pmod(p->ru_gen, j, p->ru_n);
p->ru_counter = 0;
p->ru_reseed = time_uptime + p->ru_out;
p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1));
}
u_int32_t
ip6id_randomid(struct randomtab *p)
{
int i, n;
if (p->ru_counter >= p->ru_max || time_uptime > p->ru_reseed)
ip6id_initid(p);
/* Skip a random number of ids */
n = arc4random() & 0x3;
if (p->ru_counter + n >= p->ru_max)
ip6id_initid(p);
for (i = 0; i <= n; i++) {
/* Linear Congruential Generator */
p->ru_x = (u_int32_t)((u_int64_t)p->ru_a * p->ru_x + p->ru_b) % p->ru_m;
}
p->ru_counter += i;
return (p->ru_seed ^ ip6id_pmod(p->ru_g, p->ru_seed2 + p->ru_x, p->ru_n)) |
p->ru_msb;
}
u_int32_t
ip6_randomflowlabel(void)
{
return ip6id_randomid(&randomtab_20) & 0xfffff;
}
|
