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/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include <sys/param.h> 37 #include <sys/kernel.h> 38 #include <sys/conf.h> 39 #include <sys/lock.h> 40 #include <sys/malloc.h> 41 #include <sys/module.h> 42 #include <sys/random.h> 43 #include <sys/sysctl.h> 44 #include <sys/systm.h> 45 46 #include <machine/md_var.h> 47 #include <machine/specialreg.h> 48 #include <x86/ifunc.h> 49 50 #include <dev/random/randomdev.h> 51 52 #define RETRY_COUNT 10 53 54 static bool has_rdrand, has_rdseed; 55 static u_int random_ivy_read(void *, u_int); 56 57 static struct random_source random_ivy = { 58 .rs_ident = "Intel Secure Key RNG", 59 .rs_source = RANDOM_PURE_RDRAND, 60 .rs_read = random_ivy_read 61 }; 62 63 SYSCTL_NODE(_kern_random, OID_AUTO, rdrand, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 64 "rdrand (ivy) entropy source"); 65 static bool acquire_independent_seed_samples = false; 66 SYSCTL_BOOL(_kern_random_rdrand, OID_AUTO, rdrand_independent_seed, 67 CTLFLAG_RWTUN, &acquire_independent_seed_samples, 0, 68 "If non-zero, use more expensive and slow, but safer, seeded samples " 69 "where RDSEED is not present."); 70 71 static bool 72 x86_rdrand_store(u_long *buf) 73 { 74 u_long rndval, seed_iterations, i; 75 int retry; 76 77 /* Per [1], "§ 5.2.6 Generating Seeds from RDRAND," 78 * machines lacking RDSEED will guarantee RDRAND is reseeded every 8kB 79 * of generated output. 80 * 81 * [1]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide#inpage-nav-6-8 82 */ 83 if (acquire_independent_seed_samples) 84 seed_iterations = 8 * 1024 / sizeof(*buf); 85 else 86 seed_iterations = 1; 87 88 for (i = 0; i < seed_iterations; i++) { 89 retry = RETRY_COUNT; 90 __asm __volatile( 91 "1:\n\t" 92 "rdrand %1\n\t" /* read randomness into rndval */ 93 "jc 2f\n\t" /* CF is set on success, exit retry loop */ 94 "dec %0\n\t" /* otherwise, retry-- */ 95 "jne 1b\n\t" /* and loop if retries are not exhausted */ 96 "2:" 97 : "+r" (retry), "=r" (rndval) : : "cc"); 98 if (retry == 0) 99 return (false); 100 } 101 *buf = rndval; 102 return (true); 103 } 104 105 static bool 106 x86_rdseed_store(u_long *buf) 107 { 108 u_long rndval; 109 int retry; 110 111 retry = RETRY_COUNT; 112 __asm __volatile( 113 "1:\n\t" 114 "rdseed %1\n\t" /* read randomness into rndval */ 115 "jc 2f\n\t" /* CF is set on success, exit retry loop */ 116 "dec %0\n\t" /* otherwise, retry-- */ 117 "jne 1b\n\t" /* and loop if retries are not exhausted */ 118 "2:" 119 : "+r" (retry), "=r" (rndval) : : "cc"); 120 *buf = rndval; 121 return (retry != 0); 122 } 123 124 static bool 125 x86_unimpl_store(u_long *buf __unused) 126 { 127 128 panic("%s called", __func__); 129 } 130 131 DEFINE_IFUNC(static, bool, x86_rng_store, (u_long *buf)) 132 { 133 has_rdrand = (cpu_feature2 & CPUID2_RDRAND); 134 has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED); 135 136 if (has_rdseed) 137 return (x86_rdseed_store); 138 else if (has_rdrand) 139 return (x86_rdrand_store); 140 else 141 return (x86_unimpl_store); 142 } 143 144 /* It is required that buf length is a multiple of sizeof(u_long). */ 145 static u_int 146 random_ivy_read(void *buf, u_int c) 147 { 148 u_long *b, rndval; 149 u_int count; 150 151 KASSERT(c % sizeof(*b) == 0, ("partial read %d", c)); 152 b = buf; 153 for (count = c; count > 0; count -= sizeof(*b)) { 154 if (!x86_rng_store(&rndval)) 155 break; 156 *b++ = rndval; 157 } 158 return (c - count); 159 } 160 161 static int 162 rdrand_modevent(module_t mod, int type, void *unused) 163 { 164 int error = 0; 165 166 switch (type) { 167 case MOD_LOAD: 168 if (has_rdrand || has_rdseed) { 169 random_source_register(&random_ivy); 170 printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident); 171 } 172 break; 173 174 case MOD_UNLOAD: 175 if (has_rdrand || has_rdseed) 176 random_source_deregister(&random_ivy); 177 break; 178 179 case MOD_SHUTDOWN: 180 break; 181 182 default: 183 error = EOPNOTSUPP; 184 break; 185 186 } 187 188 return (error); 189 } 190 191 static moduledata_t rdrand_mod = { 192 "rdrand", 193 rdrand_modevent, 194 0 195 }; 196 197 DECLARE_MODULE(rdrand, rdrand_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH); 198 MODULE_VERSION(rdrand, 1); 199 MODULE_DEPEND(rdrand, random_harvestq, 1, 1, 1); 200