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/fips.h> 43 #include <linux/time.h> 44 #include <linux/crypto.h> 45 #include <crypto/internal/rng.h> 46 47 struct rand_data; 48 int jent_read_entropy(struct rand_data *ec, unsigned char *data, 49 unsigned int len); 50 int jent_entropy_init(void); 51 struct rand_data *jent_entropy_collector_alloc(unsigned int osr, 52 unsigned int flags); 53 void jent_entropy_collector_free(struct rand_data *entropy_collector); 54 55 /*************************************************************************** 56 * Helper function 57 ***************************************************************************/ 58 59 void *jent_zalloc(unsigned int len) 60 { 61 return kzalloc(len, GFP_KERNEL); 62 } 63 64 void jent_zfree(void *ptr) 65 { 66 kzfree(ptr); 67 } 68 69 int jent_fips_enabled(void) 70 { 71 return fips_enabled; 72 } 73 74 void jent_panic(char *s) 75 { 76 panic("%s", s); 77 } 78 79 void jent_memcpy(void *dest, const void *src, unsigned int n) 80 { 81 memcpy(dest, src, n); 82 } 83 84 /* 85 * Obtain a high-resolution time stamp value. The time stamp is used to measure 86 * the execution time of a given code path and its variations. Hence, the time 87 * stamp must have a sufficiently high resolution. 88 * 89 * Note, if the function returns zero because a given architecture does not 90 * implement a high-resolution time stamp, the RNG code's runtime test 91 * will detect it and will not produce output. 92 */ 93 void jent_get_nstime(__u64 *out) 94 { 95 __u64 tmp = 0; 96 97 tmp = random_get_entropy(); 98 99 /* 100 * If random_get_entropy does not return a value, i.e. it is not 101 * implemented for a given architecture, use a clock source. 102 * hoping that there are timers we can work with. 103 */ 104 if (tmp == 0) 105 tmp = ktime_get_ns(); 106 107 *out = tmp; 108 } 109 110 /*************************************************************************** 111 * Kernel crypto API interface 112 ***************************************************************************/ 113 114 struct jitterentropy { 115 spinlock_t jent_lock; 116 struct rand_data *entropy_collector; 117 }; 118 119 static int jent_kcapi_init(struct crypto_tfm *tfm) 120 { 121 struct jitterentropy *rng = crypto_tfm_ctx(tfm); 122 int ret = 0; 123 124 rng->entropy_collector = jent_entropy_collector_alloc(1, 0); 125 if (!rng->entropy_collector) 126 ret = -ENOMEM; 127 128 spin_lock_init(&rng->jent_lock); 129 return ret; 130 } 131 132 static void jent_kcapi_cleanup(struct crypto_tfm *tfm) 133 { 134 struct jitterentropy *rng = crypto_tfm_ctx(tfm); 135 136 spin_lock(&rng->jent_lock); 137 if (rng->entropy_collector) 138 jent_entropy_collector_free(rng->entropy_collector); 139 rng->entropy_collector = NULL; 140 spin_unlock(&rng->jent_lock); 141 } 142 143 static int jent_kcapi_random(struct crypto_rng *tfm, 144 const u8 *src, unsigned int slen, 145 u8 *rdata, unsigned int dlen) 146 { 147 struct jitterentropy *rng = crypto_rng_ctx(tfm); 148 int ret = 0; 149 150 spin_lock(&rng->jent_lock); 151 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); 152 spin_unlock(&rng->jent_lock); 153 154 return ret; 155 } 156 157 static int jent_kcapi_reset(struct crypto_rng *tfm, 158 const u8 *seed, unsigned int slen) 159 { 160 return 0; 161 } 162 163 static struct rng_alg jent_alg = { 164 .generate = jent_kcapi_random, 165 .seed = jent_kcapi_reset, 166 .seedsize = 0, 167 .base = { 168 .cra_name = "jitterentropy_rng", 169 .cra_driver_name = "jitterentropy_rng", 170 .cra_priority = 100, 171 .cra_ctxsize = sizeof(struct jitterentropy), 172 .cra_module = THIS_MODULE, 173 .cra_init = jent_kcapi_init, 174 .cra_exit = jent_kcapi_cleanup, 175 176 } 177 }; 178 179 static int __init jent_mod_init(void) 180 { 181 int ret = 0; 182 183 ret = jent_entropy_init(); 184 if (ret) { 185 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); 186 return -EFAULT; 187 } 188 return crypto_register_rng(&jent_alg); 189 } 190 191 static void __exit jent_mod_exit(void) 192 { 193 crypto_unregister_rng(&jent_alg); 194 } 195 196 module_init(jent_mod_init); 197 module_exit(jent_mod_exit); 198 199 MODULE_LICENSE("Dual BSD/GPL"); 200 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); 201 MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); 202 MODULE_ALIAS_CRYPTO("jitterentropy_rng"); 203