crypto/jitterentropy-kcapi.c

   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");