1 /*-
2 * Copyright (c) 2017 The FreeBSD Foundation
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer
10 * in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 */
27
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
30
31 #include <sys/types.h>
32 #include <sys/param.h>
33 #include <sys/kernel.h>
34 #include <sys/libkern.h>
35 #include <sys/linker.h>
36 #include <sys/lock.h>
37 #include <sys/malloc.h>
38 #include <sys/mutex.h>
39 #include <sys/random.h>
40 #include <sys/smp.h>
41 #include <sys/time.h>
42
43 #include <crypto/chacha20/chacha.h>
44
45 #define CHACHA20_RESEED_BYTES 65536
46 #define CHACHA20_RESEED_SECONDS 300
47 #define CHACHA20_KEYBYTES 32
48 #define CHACHA20_BUFFER_SIZE 64
49
50 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
51
52 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
53
54 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
55
56 struct chacha20_s {
57 struct mtx mtx;
58 int numbytes;
59 int first_time_done;
60 time_t t_reseed;
61 u_int8_t m_buffer[CHACHA20_BUFFER_SIZE];
62 struct chacha_ctx ctx;
63 } __aligned(CACHE_LINE_SIZE);
64
65 static struct chacha20_s *chacha20inst = NULL;
66
67 #define CHACHA20_FOREACH(_chacha20) \
68 for (_chacha20 = &chacha20inst[0]; \
69 _chacha20 <= &chacha20inst[mp_maxid]; \
70 _chacha20++)
71
72 /*
73 * Mix up the current context.
74 */
75 static void
chacha20_randomstir(struct chacha20_s * chacha20)76 chacha20_randomstir(struct chacha20_s* chacha20)
77 {
78 struct timeval tv_now;
79 size_t n, size;
80 u_int8_t key[CHACHA20_KEYBYTES], *data;
81 caddr_t keyfile;
82
83 /*
84 * This is making the best of what may be an insecure
85 * Situation. If the loader(8) did not have an entropy
86 * stash from the previous shutdown to load, then we will
87 * be improperly seeded. The answer is to make sure there
88 * is an entropy stash at shutdown time.
89 */
90 (void)read_random(key, CHACHA20_KEYBYTES);
91 if (!chacha20->first_time_done) {
92 keyfile = preload_search_by_type(RANDOM_CACHED_BOOT_ENTROPY_MODULE);
93 if (keyfile != NULL) {
94 data = preload_fetch_addr(keyfile);
95 size = MIN(preload_fetch_size(keyfile), CHACHA20_KEYBYTES);
96 for (n = 0; n < size; n++)
97 key[n] ^= data[n];
98 explicit_bzero(data, size);
99 if (bootverbose)
100 printf("arc4random: read %zu bytes from preloaded cache\n", size);
101 } else
102 printf("arc4random: no preloaded entropy cache\n");
103 chacha20->first_time_done = 1;
104 }
105 getmicrouptime(&tv_now);
106 mtx_lock(&chacha20->mtx);
107 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
108 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
109 /* Reset for next reseed cycle. */
110 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
111 chacha20->numbytes = 0;
112 mtx_unlock(&chacha20->mtx);
113 }
114
115 /*
116 * Initialize the contexts.
117 */
118 static void
chacha20_init(void)119 chacha20_init(void)
120 {
121 struct chacha20_s *chacha20;
122
123 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
124 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
125 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
126
127 CHACHA20_FOREACH(chacha20) {
128 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
129 chacha20->t_reseed = -1;
130 chacha20->numbytes = 0;
131 chacha20->first_time_done = 0;
132 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
133 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
134 }
135 }
136 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
137
138
139 static void
chacha20_uninit(void)140 chacha20_uninit(void)
141 {
142 struct chacha20_s *chacha20;
143
144 CHACHA20_FOREACH(chacha20)
145 mtx_destroy(&chacha20->mtx);
146 free(chacha20inst, M_CHACHA20RANDOM);
147 }
148 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
149
150
151 /*
152 * MPSAFE
153 */
154 void
arc4rand(void * ptr,u_int len,int reseed)155 arc4rand(void *ptr, u_int len, int reseed)
156 {
157 struct chacha20_s *chacha20;
158 struct timeval tv;
159 u_int length;
160 u_int8_t *p;
161
162 if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))
163 CHACHA20_FOREACH(chacha20)
164 chacha20_randomstir(chacha20);
165
166 chacha20 = &chacha20inst[curcpu];
167 getmicrouptime(&tv);
168 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
169 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
170 chacha20_randomstir(chacha20);
171
172 mtx_lock(&chacha20->mtx);
173 p = ptr;
174 while (len) {
175 length = MIN(CHACHA20_BUFFER_SIZE, len);
176 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
177 p += length;
178 len -= length;
179 chacha20->numbytes += length;
180 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
181 mtx_unlock(&chacha20->mtx);
182 chacha20_randomstir(chacha20);
183 mtx_lock(&chacha20->mtx);
184 }
185 }
186 mtx_unlock(&chacha20->mtx);
187 }
188
189 uint32_t
arc4random(void)190 arc4random(void)
191 {
192 uint32_t ret;
193
194 arc4rand(&ret, sizeof(ret), 0);
195 return ret;
196 }
197
198 void
arc4random_buf(void * ptr,size_t len)199 arc4random_buf(void *ptr, size_t len)
200 {
201
202 arc4rand(ptr, len, 0);
203 }
204