crypto/rng.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * RNG operations.
   5  *
   6  * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the Free
  10  * Software Foundation; either version 2 of the License, or (at your option)
  11  * any later version.
  12  *
  13  */
  14
  15 #include <asm/atomic.h>
  16 #include <crypto/internal/rng.h>
  17 #include <linux/err.h>
  18 #include <linux/module.h>
  19 #include <linux/mutex.h>
  20 #include <linux/random.h>
  21 #include <linux/seq_file.h>
  22 #include <linux/string.h>
  23
  24 static DEFINE_MUTEX(crypto_default_rng_lock);
  25 struct crypto_rng *crypto_default_rng;
  26 EXPORT_SYMBOL_GPL(crypto_default_rng);
  27 static int crypto_default_rng_refcnt;
  28
  29 static int rngapi_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
  30 {
  31         u8 *buf = NULL;
  32         int err;
  33
  34         if (!seed && slen) {
  35                 buf = kmalloc(slen, GFP_KERNEL);
  36                 if (!buf)
  37                         return -ENOMEM;
  38
  39                 get_random_bytes(buf, slen);
  40                 seed = buf;
  41         }
  42
  43         err = crypto_rng_alg(tfm)->rng_reset(tfm, seed, slen);
  44
  45         kfree(buf);
  46         return err;
  47 }
  48
  49 static int crypto_init_rng_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
  50 {
  51         struct rng_alg *alg = &tfm->__crt_alg->cra_rng;
  52         struct rng_tfm *ops = &tfm->crt_rng;
  53
  54         ops->rng_gen_random = alg->rng_make_random;
  55         ops->rng_reset = rngapi_reset;
  56
  57         return 0;
  58 }
  59
  60 static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
  61         __attribute__ ((unused));
  62 static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
  63 {
  64         seq_printf(m, "type         : rng\n");
  65         seq_printf(m, "seedsize     : %u\n", alg->cra_rng.seedsize);
  66 }
  67
  68 static unsigned int crypto_rng_ctxsize(struct crypto_alg *alg, u32 type,
  69                                        u32 mask)
  70 {
  71         return alg->cra_ctxsize;
  72 }
  73
  74 const struct crypto_type crypto_rng_type = {
  75         .ctxsize = crypto_rng_ctxsize,
  76         .init = crypto_init_rng_ops,
  77 #ifdef CONFIG_PROC_FS
  78         .show = crypto_rng_show,
  79 #endif
  80 };
  81 EXPORT_SYMBOL_GPL(crypto_rng_type);
  82
  83 int crypto_get_default_rng(void)
  84 {
  85         struct crypto_rng *rng;
  86         int err;
  87
  88         mutex_lock(&crypto_default_rng_lock);
  89         if (!crypto_default_rng) {
  90                 rng = crypto_alloc_rng("stdrng", 0, 0);
  91                 err = PTR_ERR(rng);
  92                 if (IS_ERR(rng))
  93                         goto unlock;
  94
  95                 err = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng));
  96                 if (err) {
  97                         crypto_free_rng(rng);
  98                         goto unlock;
  99                 }
 100
 101                 crypto_default_rng = rng;
 102         }
 103
 104         crypto_default_rng_refcnt++;
 105         err = 0;
 106
 107 unlock:
 108         mutex_unlock(&crypto_default_rng_lock);
 109
 110         return err;
 111 }
 112 EXPORT_SYMBOL_GPL(crypto_get_default_rng);
 113
 114 void crypto_put_default_rng(void)
 115 {
 116         mutex_lock(&crypto_default_rng_lock);
 117         if (!--crypto_default_rng_refcnt) {
 118                 crypto_free_rng(crypto_default_rng);
 119                 crypto_default_rng = NULL;
 120         }
 121         mutex_unlock(&crypto_default_rng_lock);
 122 }
 123 EXPORT_SYMBOL_GPL(crypto_put_default_rng);
 124
 125 MODULE_LICENSE("GPL");
 126 MODULE_DESCRIPTION("Random Number Generator");