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 /* 91 * Obtain a high-resolution time stamp value. The time stamp is used to measure 92 * the execution time of a given code path and its variations. Hence, the time 93 * stamp must have a sufficiently high resolution. 94 * 95 * Note, if the function returns zero because a given architecture does not 96 * implement a high-resolution time stamp, the RNG code's runtime test 97 * will detect it and will not produce output. 98 */ 99 void jent_get_nstime(__u64 *out) 100 { 101 __u64 tmp = 0; 102 103 tmp = random_get_entropy(); 104 105 /* 106 * If random_get_entropy does not return a value, i.e. it is not 107 * implemented for a given architecture, use a clock source. 108 * hoping that there are timers we can work with. 109 */ 110 if (tmp == 0) 111 tmp = ktime_get_ns(); 112 113 *out = tmp; 114 } 115 116 /*************************************************************************** 117 * Kernel crypto API interface 118 ***************************************************************************/ 119 120 struct jitterentropy { 121 spinlock_t jent_lock; 122 struct rand_data *entropy_collector; 123 }; 124 125 static int jent_kcapi_init(struct crypto_tfm *tfm) 126 { 127 struct jitterentropy *rng = crypto_tfm_ctx(tfm); 128 int ret = 0; 129 130 rng->entropy_collector = jent_entropy_collector_alloc(1, 0); 131 if (!rng->entropy_collector) 132 ret = -ENOMEM; 133 134 spin_lock_init(&rng->jent_lock); 135 return ret; 136 } 137 138 static void jent_kcapi_cleanup(struct crypto_tfm *tfm) 139 { 140 struct jitterentropy *rng = crypto_tfm_ctx(tfm); 141 142 spin_lock(&rng->jent_lock); 143 if (rng->entropy_collector) 144 jent_entropy_collector_free(rng->entropy_collector); 145 rng->entropy_collector = NULL; 146 spin_unlock(&rng->jent_lock); 147 } 148 149 static int jent_kcapi_random(struct crypto_rng *tfm, 150 const u8 *src, unsigned int slen, 151 u8 *rdata, unsigned int dlen) 152 { 153 struct jitterentropy *rng = crypto_rng_ctx(tfm); 154 int ret = 0; 155 156 spin_lock(&rng->jent_lock); 157 ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); 158 spin_unlock(&rng->jent_lock); 159 160 return ret; 161 } 162 163 static int jent_kcapi_reset(struct crypto_rng *tfm, 164 const u8 *seed, unsigned int slen) 165 { 166 return 0; 167 } 168 169 static struct rng_alg jent_alg = { 170 .generate = jent_kcapi_random, 171 .seed = jent_kcapi_reset, 172 .seedsize = 0, 173 .base = { 174 .cra_name = "jitterentropy_rng", 175 .cra_driver_name = "jitterentropy_rng", 176 .cra_priority = 100, 177 .cra_ctxsize = sizeof(struct jitterentropy), 178 .cra_module = THIS_MODULE, 179 .cra_init = jent_kcapi_init, 180 .cra_exit = jent_kcapi_cleanup, 181 182 } 183 }; 184 185 static int __init jent_mod_init(void) 186 { 187 int ret = 0; 188 189 ret = jent_entropy_init(); 190 if (ret) { 191 pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); 192 return -EFAULT; 193 } 194 return crypto_register_rng(&jent_alg); 195 } 196 197 static void __exit jent_mod_exit(void) 198 { 199 crypto_unregister_rng(&jent_alg); 200 } 201 202 module_init(jent_mod_init); 203 module_exit(jent_mod_exit); 204 205 MODULE_LICENSE("Dual BSD/GPL"); 206 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); 207 MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); 208 MODULE_ALIAS_CRYPTO("jitterentropy_rng"); 209