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 /*
  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");