linux/crypto/jitterentropy-kcapi.c
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   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
  48struct rand_data;
  49int jent_read_entropy(struct rand_data *ec, unsigned char *data,
  50                      unsigned int len);
  51int jent_entropy_init(void);
  52struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
  53                                               unsigned int flags);
  54void 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
  65void *jent_zalloc(unsigned int len)
  66{
  67        return kzalloc(len, GFP_KERNEL);
  68}
  69
  70void jent_zfree(void *ptr)
  71{
  72        kzfree(ptr);
  73}
  74
  75int jent_fips_enabled(void)
  76{
  77        return fips_enabled;
  78}
  79
  80void jent_panic(char *s)
  81{
  82        panic("%s", s);
  83}
  84
  85void 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 */
  99void 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
 120struct jitterentropy {
 121        spinlock_t jent_lock;
 122        struct rand_data *entropy_collector;
 123};
 124
 125static 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
 138static 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
 149static 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
 163static int jent_kcapi_reset(struct crypto_rng *tfm,
 164                            const u8 *seed, unsigned int slen)
 165{
 166        return 0;
 167}
 168
 169static 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
 185static 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
 197static void __exit jent_mod_exit(void)
 198{
 199        crypto_unregister_rng(&jent_alg);
 200}
 201
 202module_init(jent_mod_init);
 203module_exit(jent_mod_exit);
 204
 205MODULE_LICENSE("Dual BSD/GPL");
 206MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
 207MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
 208MODULE_ALIAS_CRYPTO("jitterentropy_rng");
 209