1 /*-
2 * Copyright (c) 2013, 2025, David E. O'Brien <deo@NUXI.org>
3 * Copyright (c) 2013 The FreeBSD Foundation
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 u_int random_rdseed_read(void *, u_int);
52
53 static struct random_source random_rdseed = {
54 .rs_ident = "Intel Secure Key Seed",
55 .rs_source = RANDOM_PURE_RDSEED,
56 .rs_read = random_rdseed_read
57 };
58
59 SYSCTL_NODE(_kern_random, OID_AUTO, rdseed, CTLFLAG_RW, 0,
60 "rdseed (x86) entropy source");
61 /* XXX: kern.random.rdseed.enabled=0 also disables RDRAND */
62 static bool enabled = true;
63 SYSCTL_BOOL(_kern_random_rdseed, OID_AUTO, enabled, CTLFLAG_RDTUN, &enabled, 0,
64 "If zero, disable the use of RDSEED.");
65
66 static bool
x86_rdseed_store(u_long * buf)67 x86_rdseed_store(u_long *buf)
68 {
69 u_long rndval;
70 int retry;
71
72 retry = RETRY_COUNT;
73 __asm __volatile(
74 "1:\n\t"
75 "rdseed %1\n\t" /* read randomness into rndval */
76 "jc 2f\n\t" /* CF is set on success, exit retry loop */
77 "dec %0\n\t" /* otherwise, retry-- */
78 "jne 1b\n\t" /* and loop if retries are not exhausted */
79 "2:"
80 : "+r" (retry), "=r" (rndval) : : "cc");
81 *buf = rndval;
82 return (retry != 0);
83 }
84
85 /* It is required that buf length is a multiple of sizeof(u_long). */
86 static u_int
random_rdseed_read(void * buf,u_int c)87 random_rdseed_read(void *buf, u_int c)
88 {
89 u_long *b, rndval;
90 u_int count;
91
92 KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
93 b = buf;
94 for (count = c; count > 0; count -= sizeof(*b)) {
95 if (!x86_rdseed_store(&rndval))
96 break;
97 *b++ = rndval;
98 }
99 return (c - count);
100 }
101
102 static int
rdseed_modevent(module_t mod,int type,void * unused)103 rdseed_modevent(module_t mod, int type, void *unused)
104 {
105 bool has_rdseed;
106 int error = 0;
107
108 has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED);
109
110 switch (type) {
111 case MOD_LOAD:
112 if (has_rdseed && enabled) {
113 random_source_register(&random_rdseed);
114 printf("random: fast provider: \"%s\"\n", random_rdseed.rs_ident);
115 }
116 break;
117
118 case MOD_UNLOAD:
119 if (has_rdseed)
120 random_source_deregister(&random_rdseed);
121 break;
122
123 case MOD_SHUTDOWN:
124 break;
125
126 default:
127 error = EOPNOTSUPP;
128 break;
129
130 }
131
132 return (error);
133 }
134
135 static moduledata_t rdseed_mod = {
136 "rdseed",
137 rdseed_modevent,
138 0
139 };
140
141 DECLARE_MODULE(rdseed, rdseed_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
142 MODULE_VERSION(rdseed, 1);
143 MODULE_DEPEND(rdseed, random_harvestq, 1, 1, 1);
144
145 /*
146 * Intel's RDSEED Entropy Assessment Report min-entropy claim is 0.6 Shannons
147 * per bit of data output. Rrefer to the following Entropy Source Validation
148 * (ESV) certificates:
149 *
150 * E#87: Junos OS Physical Entropy Source - Broadwell EP 10-Core Die
151 * Broadwell-EP-10 FCLGA2011 Intel(R) Xeon(R) E5-2620 V4 Processor
152 * https://csrc.nist.gov/projects/cryptographic-module-validation-program/entropy-validations/certificate/87
153 * (URLs below omitted for brevity but follow same format.)
154 *
155 * E#121: Junos OS Physical Entropy Source - Intel Atom C3000 Series
156 * (Denverton) 16 Core Die with FCBGA1310 Package
157 *
158 * E#122: Junos OS Physical Entropy Source - Intel Xeon D-1500 Family
159 * (Broadwell) 8 Core Die with FCBGA1667 Package
160 *
161 * E#123: Junos OS Physical Entropy Source - Intel Xeon D-2100 Series
162 * (Skylake) 18 Core Die with FCBGA2518 Package
163 *
164 * E#141: Junos OS Physical Entropy Source - Intel Xeon D-10 Series
165 * (Ice Lake-D-10) Die with FCBGA2227 Package
166 *
167 * E#169: Junos OS Physical Entropy Source - Intel Xeon AWS-1000 v4 and
168 * E5 v4 (Broadwell EP) 15 Core Die with FCLGA2011 Package
169 */
170