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 #include <sys/types.h>
29 #include <sys/param.h>
30 #include <sys/kernel.h>
31 #include <sys/libkern.h>
32 #include <sys/linker.h>
33 #include <sys/lock.h>
34 #include <sys/malloc.h>
35 #include <sys/msan.h>
36 #include <sys/mutex.h>
37 #include <sys/random.h>
38 #include <sys/smp.h>
39 #include <sys/time.h>
40
41 #include <machine/cpu.h>
42
43 #include <crypto/chacha20/chacha.h>
44 #include <crypto/sha2/sha256.h>
45 #include <dev/random/randomdev.h>
46 #ifdef RANDOM_FENESTRASX
47 #include <dev/random/fenestrasX/fx_pub.h>
48 #endif
49
50 #define CHACHA20_RESEED_BYTES 65536
51 #define CHACHA20_RESEED_SECONDS 300
52 #define CHACHA20_KEYBYTES 32
53 #define CHACHA20_BUFFER_SIZE 64
54
55 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
56
57 #ifndef RANDOM_FENESTRASX
58 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
59 #endif
60
61 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
62
63 struct chacha20_s {
64 struct mtx mtx;
65 int numbytes;
66 time_t t_reseed;
67 uint8_t m_buffer[CHACHA20_BUFFER_SIZE];
68 struct chacha_ctx ctx;
69 #ifdef RANDOM_FENESTRASX
70 uint64_t seed_version;
71 #endif
72 } __aligned(CACHE_LINE_SIZE);
73
74 static struct chacha20_s *chacha20inst = NULL;
75
76 #define CHACHA20_FOREACH(_chacha20) \
77 for (_chacha20 = &chacha20inst[0]; \
78 _chacha20 <= &chacha20inst[mp_maxid]; \
79 _chacha20++)
80
81 /*
82 * Mix up the current context.
83 */
84 static void
chacha20_randomstir(struct chacha20_s * chacha20)85 chacha20_randomstir(struct chacha20_s *chacha20)
86 {
87 struct timeval tv_now;
88 uint8_t key[CHACHA20_KEYBYTES];
89 #ifdef RANDOM_FENESTRASX
90 uint64_t seed_version;
91
92 #else
93 if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) {
94 SHA256_CTX ctx;
95 uint64_t cc;
96 uint32_t fver;
97
98 if (!arc4random_bypassed_before_seeding) {
99 arc4random_bypassed_before_seeding = true;
100 if (!random_bypass_disable_warnings)
101 printf("arc4random: WARNING: initial seeding "
102 "bypassed the cryptographic random device "
103 "because it was not yet seeded and the "
104 "knob 'bypass_before_seeding' was "
105 "enabled.\n");
106 }
107
108 /*
109 * "key" is intentionally left uninitialized here, so with KMSAN
110 * enabled the arc4random() return value may be marked
111 * uninitialized, leading to spurious reports. Lie to KMSAN to
112 * avoid this situation.
113 */
114 kmsan_mark(key, sizeof(key), KMSAN_STATE_INITED);
115
116 /* Last ditch effort to inject something in a bad condition. */
117 cc = get_cyclecount();
118 SHA256_Init(&ctx);
119 SHA256_Update(&ctx, key, sizeof(key));
120 SHA256_Update(&ctx, &cc, sizeof(cc));
121 fver = __FreeBSD_version;
122 SHA256_Update(&ctx, &fver, sizeof(fver));
123 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH,
124 "make sure 256 bits is still 256 bits");
125 SHA256_Final(key, &ctx);
126 } else {
127 #endif
128 #ifdef RANDOM_FENESTRASX
129 read_random_key(key, CHACHA20_KEYBYTES, &seed_version);
130 #else
131 /*
132 * If the loader(8) did not have an entropy stash from the
133 * previous shutdown to load, then we will block. The answer is
134 * to make sure there is an entropy stash at shutdown time.
135 *
136 * On the other hand, if the random_bypass_before_seeding knob
137 * was set and we landed in this branch, we know this won't
138 * block because we know the random device is seeded.
139 */
140 read_random(key, CHACHA20_KEYBYTES);
141 }
142 #endif
143 getmicrouptime(&tv_now);
144 mtx_lock(&chacha20->mtx);
145 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
146 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
147 /* Reset for next reseed cycle. */
148 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
149 chacha20->numbytes = 0;
150 #ifdef RANDOM_FENESTRASX
151 chacha20->seed_version = seed_version;
152 #endif
153 mtx_unlock(&chacha20->mtx);
154 }
155
156 /*
157 * Initialize the contexts.
158 */
159 static void
160 chacha20_init(void)
161 {
162 struct chacha20_s *chacha20;
163
164 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
165 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
166 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
167
168 CHACHA20_FOREACH(chacha20) {
169 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
170 chacha20->t_reseed = -1;
171 chacha20->numbytes = 0;
172 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
173 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
174 }
175 }
176 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
177
178
179 static void
180 chacha20_uninit(void)
181 {
182 struct chacha20_s *chacha20;
183
184 CHACHA20_FOREACH(chacha20)
185 mtx_destroy(&chacha20->mtx);
186 free(chacha20inst, M_CHACHA20RANDOM);
187 }
188 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
189
190
191 /*
192 * MPSAFE
193 */
194 void
195 arc4rand(void *ptr, u_int len, int reseed)
196 {
197 struct chacha20_s *chacha20;
198 struct timeval tv;
199 u_int length;
200 uint8_t *p;
201
202 #ifdef RANDOM_FENESTRASX
203 if (__predict_false(reseed))
204 #else
205 if (__predict_false(reseed ||
206 (arc4rand_iniseed_state == ARC4_ENTR_HAVE &&
207 atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))))
208 #endif
209 CHACHA20_FOREACH(chacha20)
210 chacha20_randomstir(chacha20);
211
212 getmicrouptime(&tv);
213 chacha20 = &chacha20inst[curcpu];
214 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
215 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
216 chacha20_randomstir(chacha20);
217
218 mtx_lock(&chacha20->mtx);
219 #ifdef RANDOM_FENESTRASX
220 if (__predict_false(
221 atomic_load_acq_64(&fxrng_root_generation) != chacha20->seed_version
222 )) {
223 mtx_unlock(&chacha20->mtx);
224 chacha20_randomstir(chacha20);
225 mtx_lock(&chacha20->mtx);
226 }
227 #endif
228
229 p = ptr;
230 while (len) {
231 length = MIN(CHACHA20_BUFFER_SIZE, len);
232 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
233 p += length;
234 len -= length;
235 chacha20->numbytes += length;
236 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
237 mtx_unlock(&chacha20->mtx);
238 chacha20_randomstir(chacha20);
239 mtx_lock(&chacha20->mtx);
240 }
241 }
242 mtx_unlock(&chacha20->mtx);
243 }
244
245 uint32_t
246 arc4random(void)
247 {
248 uint32_t ret;
249
250 arc4rand(&ret, sizeof(ret), 0);
251 return ret;
252 }
253
254 void
255 arc4random_buf(void *ptr, size_t len)
256 {
257
258 arc4rand(ptr, len, 0);
259 }
260