1 /*-
2 * Copyright (c) 2017 The FreeBSD Foundation
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer
9 * in this position and unchanged.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29
30 #include <sys/types.h>
31 #include <sys/param.h>
32 #include <sys/kernel.h>
33 #include <sys/libkern.h>
34 #include <sys/linker.h>
35 #include <sys/lock.h>
36 #include <sys/malloc.h>
37 #include <sys/mutex.h>
38 #include <sys/random.h>
39 #include <sys/smp.h>
40 #include <sys/time.h>
41
42 #include <machine/cpu.h>
43
44 #include <crypto/chacha20/chacha.h>
45 #include <crypto/sha2/sha256.h>
46 #include <dev/random/randomdev.h>
47 #ifdef RANDOM_FENESTRASX
48 #include <dev/random/fenestrasX/fx_pub.h>
49 #endif
50
51 #define CHACHA20_RESEED_BYTES 65536
52 #define CHACHA20_RESEED_SECONDS 300
53 #define CHACHA20_KEYBYTES 32
54 #define CHACHA20_BUFFER_SIZE 64
55
56 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
57
58 #ifndef RANDOM_FENESTRASX
59 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
60 #endif
61
62 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
63
64 struct chacha20_s {
65 struct mtx mtx;
66 int numbytes;
67 time_t t_reseed;
68 u_int8_t m_buffer[CHACHA20_BUFFER_SIZE];
69 struct chacha_ctx ctx;
70 #ifdef RANDOM_FENESTRASX
71 uint64_t seed_version;
72 #endif
73 } __aligned(CACHE_LINE_SIZE);
74
75 static struct chacha20_s *chacha20inst = NULL;
76
77 #define CHACHA20_FOREACH(_chacha20) \
78 for (_chacha20 = &chacha20inst[0]; \
79 _chacha20 <= &chacha20inst[mp_maxid]; \
80 _chacha20++)
81
82 /*
83 * Mix up the current context.
84 */
85 static void
chacha20_randomstir(struct chacha20_s * chacha20)86 chacha20_randomstir(struct chacha20_s *chacha20)
87 {
88 struct timeval tv_now;
89 u_int8_t key[CHACHA20_KEYBYTES];
90 #ifdef RANDOM_FENESTRASX
91 uint64_t seed_version;
92
93 #else
94 if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) {
95 SHA256_CTX ctx;
96 uint64_t cc;
97 uint32_t fver;
98
99 if (!arc4random_bypassed_before_seeding) {
100 arc4random_bypassed_before_seeding = true;
101 if (!random_bypass_disable_warnings)
102 printf("arc4random: WARNING: initial seeding "
103 "bypassed the cryptographic random device "
104 "because it was not yet seeded and the "
105 "knob 'bypass_before_seeding' was "
106 "enabled.\n");
107 }
108
109 /* Last ditch effort to inject something in a bad condition. */
110 cc = get_cyclecount();
111 SHA256_Init(&ctx);
112 SHA256_Update(&ctx, key, sizeof(key));
113 SHA256_Update(&ctx, &cc, sizeof(cc));
114 fver = __FreeBSD_version;
115 SHA256_Update(&ctx, &fver, sizeof(fver));
116 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH,
117 "make sure 256 bits is still 256 bits");
118 SHA256_Final(key, &ctx);
119 } else {
120 #endif
121 #ifdef RANDOM_FENESTRASX
122 read_random_key(key, CHACHA20_KEYBYTES, &seed_version);
123 #else
124 /*
125 * If the loader(8) did not have an entropy stash from the
126 * previous shutdown to load, then we will block. The answer is
127 * to make sure there is an entropy stash at shutdown time.
128 *
129 * On the other hand, if the random_bypass_before_seeding knob
130 * was set and we landed in this branch, we know this won't
131 * block because we know the random device is seeded.
132 */
133 read_random(key, CHACHA20_KEYBYTES);
134 }
135 #endif
136 getmicrouptime(&tv_now);
137 mtx_lock(&chacha20->mtx);
138 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
139 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
140 /* Reset for next reseed cycle. */
141 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
142 chacha20->numbytes = 0;
143 #ifdef RANDOM_FENESTRASX
144 chacha20->seed_version = seed_version;
145 #endif
146 mtx_unlock(&chacha20->mtx);
147 }
148
149 /*
150 * Initialize the contexts.
151 */
152 static void
153 chacha20_init(void)
154 {
155 struct chacha20_s *chacha20;
156
157 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
158 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
159 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
160
161 CHACHA20_FOREACH(chacha20) {
162 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
163 chacha20->t_reseed = -1;
164 chacha20->numbytes = 0;
165 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
166 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
167 }
168 }
169 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
170
171
172 static void
173 chacha20_uninit(void)
174 {
175 struct chacha20_s *chacha20;
176
177 CHACHA20_FOREACH(chacha20)
178 mtx_destroy(&chacha20->mtx);
179 free(chacha20inst, M_CHACHA20RANDOM);
180 }
181 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
182
183
184 /*
185 * MPSAFE
186 */
187 void
188 arc4rand(void *ptr, u_int len, int reseed)
189 {
190 struct chacha20_s *chacha20;
191 struct timeval tv;
192 u_int length;
193 u_int8_t *p;
194
195 #ifdef RANDOM_FENESTRASX
196 if (__predict_false(reseed))
197 #else
198 if (__predict_false(reseed ||
199 (arc4rand_iniseed_state == ARC4_ENTR_HAVE &&
200 atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))))
201 #endif
202 CHACHA20_FOREACH(chacha20)
203 chacha20_randomstir(chacha20);
204
205 getmicrouptime(&tv);
206 chacha20 = &chacha20inst[curcpu];
207 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
208 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
209 chacha20_randomstir(chacha20);
210
211 mtx_lock(&chacha20->mtx);
212 #ifdef RANDOM_FENESTRASX
213 if (__predict_false(
214 atomic_load_acq_64(&fxrng_root_generation) != chacha20->seed_version
215 )) {
216 mtx_unlock(&chacha20->mtx);
217 chacha20_randomstir(chacha20);
218 mtx_lock(&chacha20->mtx);
219 }
220 #endif
221
222 p = ptr;
223 while (len) {
224 length = MIN(CHACHA20_BUFFER_SIZE, len);
225 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
226 p += length;
227 len -= length;
228 chacha20->numbytes += length;
229 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
230 mtx_unlock(&chacha20->mtx);
231 chacha20_randomstir(chacha20);
232 mtx_lock(&chacha20->mtx);
233 }
234 }
235 mtx_unlock(&chacha20->mtx);
236 }
237
238 uint32_t
239 arc4random(void)
240 {
241 uint32_t ret;
242
243 arc4rand(&ret, sizeof(ret), 0);
244 return ret;
245 }
246
247 void
248 arc4random_buf(void *ptr, size_t len)
249 {
250
251 arc4rand(ptr, len, 0);
252 }
253