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 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 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 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 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 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