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/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");