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 #include <crypto/sha2/sha256.h>
45 #include <dev/random/randomdev.h>
46 #include <machine/cpu.h>
47
48 #define CHACHA20_RESEED_BYTES 65536
49 #define CHACHA20_RESEED_SECONDS 300
50 #define CHACHA20_KEYBYTES 32
51 #define CHACHA20_BUFFER_SIZE 64
52
53 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
54
55 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
56
57 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
58
59 struct chacha20_s {
60 struct mtx mtx;
61 int numbytes;
62 time_t t_reseed;
63 u_int8_t m_buffer[CHACHA20_BUFFER_SIZE];
64 struct chacha_ctx ctx;
65 } __aligned(CACHE_LINE_SIZE);
66
67 static struct chacha20_s *chacha20inst = NULL;
68
69 #define CHACHA20_FOREACH(_chacha20) \
70 for (_chacha20 = &chacha20inst[0]; \
71 _chacha20 <= &chacha20inst[mp_maxid]; \
72 _chacha20++)
73
74 /*
75 * Mix up the current context.
76 */
77 static void
78 chacha20_randomstir(struct chacha20_s *chacha20)
79 {
80 struct timeval tv_now;
81 u_int8_t key[CHACHA20_KEYBYTES];
82
83 if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) {
84 SHA256_CTX ctx;
85 uint64_t cc;
86 uint32_t fver;
87
88 if (!arc4random_bypassed_before_seeding) {
89 arc4random_bypassed_before_seeding = true;
90 if (!random_bypass_disable_warnings)
91 printf("arc4random: WARNING: initial seeding "
92 "bypassed the cryptographic random device "
93 "because it was not yet seeded and the "
94 "knob 'bypass_before_seeding' was "
95 "enabled.\n");
96 }
97
98 /* Last ditch effort to inject something in a bad condition. */
99 cc = get_cyclecount();
100 SHA256_Init(&ctx);
101 SHA256_Update(&ctx, key, sizeof(key));
102 SHA256_Update(&ctx, &cc, sizeof(cc));
103 fver = __FreeBSD_version;
104 SHA256_Update(&ctx, &fver, sizeof(fver));
105 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH,
106 "make sure 256 bits is still 256 bits");
107 SHA256_Final(key, &ctx);
108 } else {
109 /*
110 * If the loader(8) did not have an entropy stash from the
111 * previous shutdown to load, then we will block. The answer is
112 * to make sure there is an entropy stash at shutdown time.
113 *
114 * On the other hand, if the random_bypass_before_seeding knob
115 * was set and we landed in this branch, we know this won't
116 * block because we know the random device is seeded.
117 */
118 read_random(key, CHACHA20_KEYBYTES);
119 }
120 getmicrouptime(&tv_now);
121 mtx_lock(&chacha20->mtx);
122 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
123 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
124 /* Reset for next reseed cycle. */
125 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
126 chacha20->numbytes = 0;
127 mtx_unlock(&chacha20->mtx);
128 }
129
130 /*
131 * Initialize the contexts.
132 */
133 static void
134 chacha20_init(void)
135 {
136 struct chacha20_s *chacha20;
137
138 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
139 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
140 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
141
142 CHACHA20_FOREACH(chacha20) {
143 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
144 chacha20->t_reseed = -1;
145 chacha20->numbytes = 0;
146 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
147 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
148 }
149 }
150 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
151
152
153 static void
154 chacha20_uninit(void)
155 {
156 struct chacha20_s *chacha20;
157
158 CHACHA20_FOREACH(chacha20)
159 mtx_destroy(&chacha20->mtx);
160 free(chacha20inst, M_CHACHA20RANDOM);
161 }
162 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
163
164
165 /*
166 * MPSAFE
167 */
168 void
169 arc4rand(void *ptr, u_int len, int reseed)
170 {
171 struct chacha20_s *chacha20;
172 struct timeval tv;
173 u_int length;
174 u_int8_t *p;
175
176 if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))
177 CHACHA20_FOREACH(chacha20)
178 chacha20_randomstir(chacha20);
179
180 chacha20 = &chacha20inst[curcpu];
181 getmicrouptime(&tv);
182 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
183 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
184 chacha20_randomstir(chacha20);
185
186 mtx_lock(&chacha20->mtx);
187 p = ptr;
188 while (len) {
189 length = MIN(CHACHA20_BUFFER_SIZE, len);
190 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
191 p += length;
192 len -= length;
193 chacha20->numbytes += length;
194 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
195 mtx_unlock(&chacha20->mtx);
196 chacha20_randomstir(chacha20);
197 mtx_lock(&chacha20->mtx);
198 }
199 }
200 mtx_unlock(&chacha20->mtx);
201 }
202
203 uint32_t
204 arc4random(void)
205 {
206 uint32_t ret;
207
208 arc4rand(&ret, sizeof(ret), 0);
209 return ret;
210 }
211
212 void
213 arc4random_buf(void *ptr, size_t len)
214 {
215
216 arc4rand(ptr, len, 0);
217 }
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