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