1 /*-
2 * Copyright (c) 2013 The FreeBSD Foundation
3 * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
4 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Portions of this software were developed by Konstantin Belousov
8 * under sponsorship from the FreeBSD Foundation.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer
15 * in this position and unchanged.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 *
31 */
32
33 #include <sys/param.h>
34 #include <sys/kernel.h>
35 #include <sys/conf.h>
36 #include <sys/lock.h>
37 #include <sys/malloc.h>
38 #include <sys/module.h>
39 #include <sys/random.h>
40 #include <sys/sysctl.h>
41 #include <sys/systm.h>
42
43 #include <machine/md_var.h>
44 #include <machine/specialreg.h>
45 #include <x86/ifunc.h>
46
47 #include <dev/random/randomdev.h>
48
49 #define RETRY_COUNT 10
50
51 static bool has_rdrand, has_rdseed;
52 static u_int random_ivy_read(void *, u_int);
53
54 static struct random_source random_ivy = {
55 .rs_ident = "Intel Secure Key RNG",
56 .rs_source = RANDOM_PURE_RDRAND,
57 .rs_read = random_ivy_read
58 };
59
60 SYSCTL_NODE(_kern_random, OID_AUTO, rdrand, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
61 "rdrand (ivy) entropy source");
62 static bool acquire_independent_seed_samples = false;
63 SYSCTL_BOOL(_kern_random_rdrand, OID_AUTO, rdrand_independent_seed,
64 CTLFLAG_RWTUN, &acquire_independent_seed_samples, 0,
65 "If non-zero, use more expensive and slow, but safer, seeded samples "
66 "where RDSEED is not present.");
67
68 static bool
x86_rdrand_store(u_long * buf)69 x86_rdrand_store(u_long *buf)
70 {
71 u_long rndval, seed_iterations, i;
72 int retry;
73
74 /* Per [1], "§ 5.2.6 Generating Seeds from RDRAND,"
75 * machines lacking RDSEED will guarantee RDRAND is reseeded every 8kB
76 * of generated output.
77 *
78 * [1]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide#inpage-nav-6-8
79 */
80 if (acquire_independent_seed_samples)
81 seed_iterations = 8 * 1024 / sizeof(*buf);
82 else
83 seed_iterations = 1;
84
85 for (i = 0; i < seed_iterations; i++) {
86 retry = RETRY_COUNT;
87 __asm __volatile(
88 "1:\n\t"
89 "rdrand %1\n\t" /* read randomness into rndval */
90 "jc 2f\n\t" /* CF is set on success, exit retry loop */
91 "dec %0\n\t" /* otherwise, retry-- */
92 "jne 1b\n\t" /* and loop if retries are not exhausted */
93 "2:"
94 : "+r" (retry), "=r" (rndval) : : "cc");
95 if (retry == 0)
96 return (false);
97 }
98 *buf = rndval;
99 return (true);
100 }
101
102 static bool
x86_rdseed_store(u_long * buf)103 x86_rdseed_store(u_long *buf)
104 {
105 u_long rndval;
106 int retry;
107
108 retry = RETRY_COUNT;
109 __asm __volatile(
110 "1:\n\t"
111 "rdseed %1\n\t" /* read randomness into rndval */
112 "jc 2f\n\t" /* CF is set on success, exit retry loop */
113 "dec %0\n\t" /* otherwise, retry-- */
114 "jne 1b\n\t" /* and loop if retries are not exhausted */
115 "2:"
116 : "+r" (retry), "=r" (rndval) : : "cc");
117 *buf = rndval;
118 return (retry != 0);
119 }
120
121 static bool
x86_unimpl_store(u_long * buf __unused)122 x86_unimpl_store(u_long *buf __unused)
123 {
124
125 panic("%s called", __func__);
126 }
127
128 DEFINE_IFUNC(static, bool, x86_rng_store, (u_long *buf))
129 {
130 has_rdrand = (cpu_feature2 & CPUID2_RDRAND);
131 has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED);
132
133 if (has_rdseed)
134 return (x86_rdseed_store);
135 else if (has_rdrand)
136 return (x86_rdrand_store);
137 else
138 return (x86_unimpl_store);
139 }
140
141 /* It is required that buf length is a multiple of sizeof(u_long). */
142 static u_int
random_ivy_read(void * buf,u_int c)143 random_ivy_read(void *buf, u_int c)
144 {
145 u_long *b, rndval;
146 u_int count;
147
148 KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
149 b = buf;
150 for (count = c; count > 0; count -= sizeof(*b)) {
151 if (!x86_rng_store(&rndval))
152 break;
153 *b++ = rndval;
154 }
155 return (c - count);
156 }
157
158 static int
rdrand_modevent(module_t mod,int type,void * unused)159 rdrand_modevent(module_t mod, int type, void *unused)
160 {
161 int error = 0;
162
163 switch (type) {
164 case MOD_LOAD:
165 if (has_rdrand || has_rdseed) {
166 random_source_register(&random_ivy);
167 printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident);
168 }
169 break;
170
171 case MOD_UNLOAD:
172 if (has_rdrand || has_rdseed)
173 random_source_deregister(&random_ivy);
174 break;
175
176 case MOD_SHUTDOWN:
177 break;
178
179 default:
180 error = EOPNOTSUPP;
181 break;
182
183 }
184
185 return (error);
186 }
187
188 static moduledata_t rdrand_mod = {
189 "rdrand",
190 rdrand_modevent,
191 0
192 };
193
194 DECLARE_MODULE(rdrand, rdrand_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
195 MODULE_VERSION(rdrand, 1);
196 MODULE_DEPEND(rdrand, random_harvestq, 1, 1, 1);
197