LXR linux/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
  47struct rand_data;
  48int jent_read_entropy(struct rand_data *ec, unsigned char *data,
  49                      unsigned int len);
  50int jent_entropy_init(void);
  51struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
  52                                               unsigned int flags);
  53void jent_entropy_collector_free(struct rand_data *entropy_collector);
  54
  55/***************************************************************************
  56 * Helper function
  57 ***************************************************************************/
  58
  59__u64 jent_rol64(__u64 word, unsigned int shift)
  60{
  61        return rol64(word, shift);
  62}
  63
  64void *jent_zalloc(unsigned int len)
  65{
  66        return kzalloc(len, GFP_KERNEL);
  67}
  68
  69void jent_zfree(void *ptr)
  70{
  71        kzfree(ptr);
  72}
  73
  74int jent_fips_enabled(void)
  75{
  76        return fips_enabled;
  77}
  78
  79void jent_panic(char *s)
  80{
  81        panic("%s", s);
  82}
  83
  84void jent_memcpy(void *dest, const void *src, unsigned int n)
  85{
  86        memcpy(dest, src, n);
  87}
  88
  89/*
  90 * Obtain a high-resolution time stamp value. The time stamp is used to measure
  91 * the execution time of a given code path and its variations. Hence, the time
  92 * stamp must have a sufficiently high resolution.
  93 *
  94 * Note, if the function returns zero because a given architecture does not
  95 * implement a high-resolution time stamp, the RNG code's runtime test
  96 * will detect it and will not produce output.
  97 */
  98void jent_get_nstime(__u64 *out)
  99{
 100        __u64 tmp = 0;
 101
 102        tmp = random_get_entropy();
 103
 104        /*
 105         * If random_get_entropy does not return a value, i.e. it is not
 106         * implemented for a given architecture, use a clock source.
 107         * hoping that there are timers we can work with.
 108         */
 109        if (tmp == 0)
 110                tmp = ktime_get_ns();
 111
 112        *out = tmp;
 113}
 114
 115/***************************************************************************
 116 * Kernel crypto API interface
 117 ***************************************************************************/
 118
 119struct jitterentropy {
 120        spinlock_t jent_lock;
 121        struct rand_data *entropy_collector;
 122};
 123
 124static int jent_kcapi_init(struct crypto_tfm *tfm)
 125{
 126        struct jitterentropy *rng = crypto_tfm_ctx(tfm);
 127        int ret = 0;
 128
 129        rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
 130        if (!rng->entropy_collector)
 131                ret = -ENOMEM;
 132
 133        spin_lock_init(&rng->jent_lock);
 134        return ret;
 135}
 136
 137static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
 138{
 139        struct jitterentropy *rng = crypto_tfm_ctx(tfm);
 140
 141        spin_lock(&rng->jent_lock);
 142        if (rng->entropy_collector)
 143                jent_entropy_collector_free(rng->entropy_collector);
 144        rng->entropy_collector = NULL;
 145        spin_unlock(&rng->jent_lock);
 146}
 147
 148static int jent_kcapi_random(struct crypto_rng *tfm,
 149                             const u8 *src, unsigned int slen,
 150                             u8 *rdata, unsigned int dlen)
 151{
 152        struct jitterentropy *rng = crypto_rng_ctx(tfm);
 153        int ret = 0;
 154
 155        spin_lock(&rng->jent_lock);
 156        ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
 157        spin_unlock(&rng->jent_lock);
 158
 159        return ret;
 160}
 161
 162static int jent_kcapi_reset(struct crypto_rng *tfm,
 163                            const u8 *seed, unsigned int slen)
 164{
 165        return 0;
 166}
 167
 168static struct rng_alg jent_alg = {
 169        .generate               = jent_kcapi_random,
 170        .seed                   = jent_kcapi_reset,
 171        .seedsize               = 0,
 172        .base                   = {
 173                .cra_name               = "jitterentropy_rng",
 174                .cra_driver_name        = "jitterentropy_rng",
 175                .cra_priority           = 100,
 176                .cra_ctxsize            = sizeof(struct jitterentropy),
 177                .cra_module             = THIS_MODULE,
 178                .cra_init               = jent_kcapi_init,
 179                .cra_exit               = jent_kcapi_cleanup,
 180
 181        }
 182};
 183
 184static int __init jent_mod_init(void)
 185{
 186        int ret = 0;
 187
 188        ret = jent_entropy_init();
 189        if (ret) {
 190                pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret);
 191                return -EFAULT;
 192        }
 193        return crypto_register_rng(&jent_alg);
 194}
 195
 196static void __exit jent_mod_exit(void)
 197{
 198        crypto_unregister_rng(&jent_alg);
 199}
 200
 201module_init(jent_mod_init);
 202module_exit(jent_mod_exit);
 203
 204MODULE_LICENSE("Dual BSD/GPL");
 205MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
 206MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
 207MODULE_ALIAS_CRYPTO("jitterentropy_rng");
 208