1 /* 2 * Non-physical true random number generator based on timing jitter -- 3 * Linux Kernel Crypto API specific code 4 * 5 * Copyright Stephan Mueller <smueller@chronox.de>, 2015 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, and the entire permission notice in its entirety, 12 * including the disclaimer of warranties. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. The name of the author may not be used to endorse or promote 17 * products derived from this software without specific prior 18 * written permission. 19 * 20 * ALTERNATIVELY, this product may be distributed under the terms of 21 * the GNU General Public License, in which case the provisions of the GPL2 are 22 * required INSTEAD OF the above restrictions. (This clause is 23 * necessary due to a potential bad interaction between the GPL and 24 * the restrictions contained in a BSD-style copyright.) 25 * 26 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED 27 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF 29 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE 30 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT 32 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 33 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 34 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 36 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH 37 * DAMAGE. 38 */ 39 40 #include <linux/module.h> 41 #include <linux/slab.h> 42 #include <linux/module.h> 43 #include <linux/fips.h> 44 #include <linux/time.h> 45 #include <linux/crypto.h> 46 #include <crypto/internal/rng.h> 47 48 struct rand_data; 49 int jent_read_entropy(struct rand_data *ec, unsigned char *data, 50 unsigned int len); 51 int jent_entropy_init(void); 52 struct rand_data *jent_entropy_collector_alloc(unsigned int osr, 53 unsigned int flags); 54 void jent_entropy_collector_free(struct rand_data *entropy_collector); 55 56 /*************************************************************************** 57 * Helper function 58 ***************************************************************************/ 59 60 __u64 jent_rol64(__u64 word, unsigned int shift) 61 { 62 return rol64(word, shift); 63 } 64 65 void *jent_zalloc(unsigned int len) 66 { 67 return kzalloc(len, GFP_KERNEL); 68 } 69 70 void jent_zfree(void *ptr) 71 { 72 kzfree(ptr); 73 } 74 75 int jent_fips_enabled(void) 76 { 77 return fips_enabled; 78 } 79 80 void jent_panic(char *s) 81 { 82 panic("%s", s); 83 } 84 85 void jent_memcpy(void *dest, const void *src, unsigned int n) 86 { 87 memcpy(dest, src, n); 88 } 89 90 void jent_get_nstime(__u64 *out) 91 { 92 struct timespec ts; 93 __u64 tmp = 0; 94 95 tmp = random_get_entropy(); 96 97 /* 98 * If random_get_entropy does not return a value (which is possible on, 99 * for example, MIPS), invoke __getnstimeofday 100 * hoping that there are timers we can work with. 101 */ 102 if ((0 == tmp) && 103 (0 == __getnstimeofday(&ts))) { 104 tmp = ts.tv_sec; 105 tmp = tmp << 32; 106 tmp = tmp | ts.tv_nsec; 107 } 108 109 *out = tmp; 110 } 111 112 /*************************************************************************** 113 * Kernel crypto API interface 114 ***************************************************************************/ 115 116 struct jitterentropy { 117 spinlock_t jent_lock; 118 struct rand_data *entropy_collector; 119 }; 120 121 static int jent_kcapi_init(struct crypto_tfm *tfm) 122 { 123 struct jitterentropy *rng = crypto_tfm_ctx(tfm); 124 int ret = 0; 125 126 rng->entropy_collector = jent_entropy_collector_alloc(1, 0); 127 if (!rng->entropy_collector) 128 ret = -ENOMEM; 129 130 spin_lock_init(&rng->jent_lock); 131 return ret; 132 } 133 134 static void jent_kcapi_cleanup(struct crypto_tfm *tfm) 135 { 136 struct jitterentropy *rng = crypto_tfm_ctx(tfm); 137 138 spin_lock(&rng->jent_lock); 139 if (rng->entropy_collector) 140 jent_entropy_collector_free(rng->entropy_collector); 141 rng->entropy_collector = NULL; 142 spin_unlock(&rng->jent_lock); 143 } 144 145 static int jent_kcapi_random(struct crypto_rng *tfm, 146 const u8 *src, unsigned int slen, 147 u8 *rdata, unsigned int dlen) 148 { 149 struct jitterentropy *rng = crypto_rng_ctx(tfm); 150 int ret = 0; 151 152 spin_lock(&rng->jent_lock); 153 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); 154 spin_unlock(&rng->jent_lock); 155 156 return ret; 157 } 158 159 static int jent_kcapi_reset(struct crypto_rng *tfm, 160 const u8 *seed, unsigned int slen) 161 { 162 return 0; 163 } 164 165 static struct rng_alg jent_alg = { 166 .generate = jent_kcapi_random, 167 .seed = jent_kcapi_reset, 168 .seedsize = 0, 169 .base = { 170 .cra_name = "jitterentropy_rng", 171 .cra_driver_name = "jitterentropy_rng", 172 .cra_priority = 100, 173 .cra_ctxsize = sizeof(struct jitterentropy), 174 .cra_module = THIS_MODULE, 175 .cra_init = jent_kcapi_init, 176 .cra_exit = jent_kcapi_cleanup, 177 178 } 179 }; 180 181 static int __init jent_mod_init(void) 182 { 183 int ret = 0; 184 185 ret = jent_entropy_init(); 186 if (ret) { 187 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); 188 return -EFAULT; 189 } 190 return crypto_register_rng(&jent_alg); 191 } 192 193 static void __exit jent_mod_exit(void) 194 { 195 crypto_unregister_rng(&jent_alg); 196 } 197 198 module_init(jent_mod_init); 199 module_exit(jent_mod_exit); 200 201 MODULE_LICENSE("Dual BSD/GPL"); 202 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); 203 MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); 204 MODULE_ALIAS_CRYPTO("jitterentropy_rng"); 205