1 /*- 2 * Copyright (c) 2015 Mark R V Murray 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer 10 * in this position and unchanged. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 */ 27 28 #include <sys/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include <sys/param.h> 32 #include <sys/systm.h> 33 #include <sys/kernel.h> 34 #include <sys/malloc.h> 35 #include <sys/random.h> 36 #include <sys/sysctl.h> 37 38 #if defined(RANDOM_LOADABLE) 39 #include <sys/lock.h> 40 #include <sys/sx.h> 41 #endif 42 43 #include <dev/random/randomdev.h> 44 45 /* Set up the sysctl root node for the entropy device */ 46 SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW, 0, 47 "Cryptographically Secure Random Number Generator"); 48 SYSCTL_NODE(_kern_random, OID_AUTO, initial_seeding, CTLFLAG_RW, 0, 49 "Initial seeding control and information"); 50 51 /* 52 * N.B., this is a dangerous default, but it matches the behavior prior to 53 * r346250 (and, say, OpenBSD -- although they get some guaranteed saved 54 * entropy from the prior boot because of their KARL system, on RW media). 55 */ 56 bool random_bypass_before_seeding = true; 57 SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO, 58 bypass_before_seeding, CTLFLAG_RDTUN, &random_bypass_before_seeding, 59 0, "If set non-zero, bypass the random device in requests for random " 60 "data when the random device is not yet seeded. This is considered " 61 "dangerous. Ordinarily, the random device will block requests until " 62 "it is seeded by sufficient entropy."); 63 64 /* 65 * This is a read-only diagnostic that reports the combination of the former 66 * tunable and actual bypass. It is intended for programmatic inspection by 67 * userspace administrative utilities after boot. 68 */ 69 bool read_random_bypassed_before_seeding = false; 70 SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO, 71 read_random_bypassed_before_seeding, CTLFLAG_RD, 72 &read_random_bypassed_before_seeding, 0, "If non-zero, the random device " 73 "was bypassed because the 'bypass_before_seeding' knob was enabled and a " 74 "request was submitted prior to initial seeding."); 75 76 /* 77 * This is a read-only diagnostic that reports the combination of the former 78 * tunable and actual bypass for arc4random initial seeding. It is intended 79 * for programmatic inspection by userspace administrative utilities after 80 * boot. 81 */ 82 bool arc4random_bypassed_before_seeding = false; 83 SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO, 84 arc4random_bypassed_before_seeding, CTLFLAG_RD, 85 &arc4random_bypassed_before_seeding, 0, "If non-zero, the random device " 86 "was bypassed when initially seeding the kernel arc4random(9), because " 87 "the 'bypass_before_seeding' knob was enabled and a request was submitted " 88 "prior to initial seeding."); 89 90 /* 91 * This knob is for users who do not want additional warnings in their logs 92 * because they intend to handle bypass by inspecting the status of the 93 * diagnostic sysctls. 94 */ 95 bool random_bypass_disable_warnings = false; 96 SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO, 97 disable_bypass_warnings, CTLFLAG_RDTUN, 98 &random_bypass_disable_warnings, 0, "If non-zero, do not log a warning " 99 "if the 'bypass_before_seeding' knob is enabled and a request is " 100 "submitted prior to initial seeding."); 101 102 MALLOC_DEFINE(M_ENTROPY, "entropy", "Entropy harvesting buffers and data structures"); 103 104 #if defined(RANDOM_LOADABLE) 105 struct random_algorithm *p_random_alg_context = NULL; 106 #else /* !defined(RANDOM_LOADABLE) */ 107 struct random_algorithm *p_random_alg_context = &random_alg_context; 108 #endif /* defined(RANDOM_LOADABLE) */ 109 110 #if defined(RANDOM_LOADABLE) 111 112 static void 113 null_read_random(void *dummy __unused, u_int dummy2 __unused) 114 { 115 panic("%s: no random module is loaded", __func__); 116 } 117 118 static bool 119 null_is_random_seeded(void) 120 { 121 return (false); 122 } 123 124 struct random_readers { 125 int (*read_random_uio)(struct uio *, bool); 126 void (*read_random)(void *, u_int); 127 bool (*is_random_seeded)(void); 128 } random_reader_context = { 129 (int (*)(struct uio *, bool))nullop, 130 null_read_random, 131 null_is_random_seeded, 132 }; 133 134 struct sx randomdev_config_lock; 135 136 static void 137 random_infra_sysinit(void *dummy __unused) 138 { 139 140 RANDOM_CONFIG_INIT_LOCK(); 141 } 142 SYSINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_FIRST, random_infra_sysinit, NULL); 143 144 void 145 random_infra_init(int (*p_random_read_uio)(struct uio *, bool), 146 void (*p_random_read)(void *, u_int), 147 bool (*p_is_random_seeded)(void)) 148 { 149 150 RANDOM_CONFIG_X_LOCK(); 151 random_reader_context.read_random_uio = p_random_read_uio; 152 random_reader_context.read_random = p_random_read; 153 random_reader_context.is_random_seeded = p_is_random_seeded; 154 RANDOM_CONFIG_X_UNLOCK(); 155 } 156 157 void 158 random_infra_uninit(void) 159 { 160 161 RANDOM_CONFIG_X_LOCK(); 162 random_reader_context.read_random_uio = (int (*)(struct uio *, bool))nullop; 163 random_reader_context.read_random = null_read_random; 164 random_reader_context.is_random_seeded = null_is_random_seeded; 165 RANDOM_CONFIG_X_UNLOCK(); 166 } 167 168 static void 169 random_infra_sysuninit(void *dummy __unused) 170 { 171 172 RANDOM_CONFIG_DEINIT_LOCK(); 173 } 174 SYSUNINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_FIRST, random_infra_sysuninit, NULL); 175 176 int 177 read_random_uio(struct uio *uio, bool nonblock) 178 { 179 int retval; 180 181 RANDOM_CONFIG_S_LOCK(); 182 retval = random_reader_context.read_random_uio(uio, nonblock); 183 RANDOM_CONFIG_S_UNLOCK(); 184 return (retval); 185 } 186 187 void 188 read_random(void *buf, u_int len) 189 { 190 191 RANDOM_CONFIG_S_LOCK(); 192 random_reader_context.read_random(buf, len); 193 RANDOM_CONFIG_S_UNLOCK(); 194 } 195 196 bool 197 is_random_seeded(void) 198 { 199 bool result; 200 201 RANDOM_CONFIG_S_LOCK(); 202 result = random_reader_context.is_random_seeded(); 203 RANDOM_CONFIG_S_UNLOCK(); 204 return (result); 205 } 206 207 208 #endif /* defined(RANDOM_LOADABLE) */ 209