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