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 <linux/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/slab.h>
  23 #include <linux/string.h>
  24
  25 static DEFINE_MUTEX(crypto_default_rng_lock);
  26 struct crypto_rng *crypto_default_rng;
  27 EXPORT_SYMBOL_GPL(crypto_default_rng);
  28 static int crypto_default_rng_refcnt;
  29
  30 static int rngapi_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen)
  31 {
  32         u8 *buf = NULL;
  33         int err;
  34
  35         if (!seed && slen) {
  36                 buf = kmalloc(slen, GFP_KERNEL);
  37                 if (!buf)
  38                         return -ENOMEM;
  39
  40                 get_random_bytes(buf, slen);
  41                 seed = buf;
  42         }
  43
  44         err = crypto_rng_alg(tfm)->rng_reset(tfm, seed, slen);
  45
  46         kfree(buf);
  47         return err;
  48 }
  49
  50 static int crypto_init_rng_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
  51 {
  52         struct rng_alg *alg = &tfm->__crt_alg->cra_rng;
  53         struct rng_tfm *ops = &tfm->crt_rng;
  54
  55         ops->rng_gen_random = alg->rng_make_random;
  56         ops->rng_reset = rngapi_reset;
  57
  58         return 0;
  59 }
  60
  61 static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
  62         __attribute__ ((unused));
  63 static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
  64 {
  65         seq_printf(m, "type         : rng\n");
  66         seq_printf(m, "seedsize     : %u\n", alg->cra_rng.seedsize);
  67 }
  68
  69 static unsigned int crypto_rng_ctxsize(struct crypto_alg *alg, u32 type,
  70                                        u32 mask)
  71 {
  72         return alg->cra_ctxsize;
  73 }
  74
  75 const struct crypto_type crypto_rng_type = {
  76         .ctxsize = crypto_rng_ctxsize,
  77         .init = crypto_init_rng_ops,
  78 #ifdef CONFIG_PROC_FS
  79         .show = crypto_rng_show,
  80 #endif
  81 };
  82 EXPORT_SYMBOL_GPL(crypto_rng_type);
  83
  84 int crypto_get_default_rng(void)
  85 {
  86         struct crypto_rng *rng;
  87         int err;
  88
  89         mutex_lock(&crypto_default_rng_lock);
  90         if (!crypto_default_rng) {
  91                 rng = crypto_alloc_rng("stdrng", 0, 0);
  92                 err = PTR_ERR(rng);
  93                 if (IS_ERR(rng))
  94                         goto unlock;
  95
  96                 err = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng));
  97                 if (err) {
  98                         crypto_free_rng(rng);
  99                         goto unlock;
 100                 }
 101
 102                 crypto_default_rng = rng;
 103         }
 104
 105         crypto_default_rng_refcnt++;
 106         err = 0;
 107
 108 unlock:
 109         mutex_unlock(&crypto_default_rng_lock);
 110
 111         return err;
 112 }
 113 EXPORT_SYMBOL_GPL(crypto_get_default_rng);
 114
 115 void crypto_put_default_rng(void)
 116 {
 117         mutex_lock(&crypto_default_rng_lock);
 118         if (!--crypto_default_rng_refcnt) {
 119                 crypto_free_rng(crypto_default_rng);
 120                 crypto_default_rng = NULL;
 121         }
 122         mutex_unlock(&crypto_default_rng_lock);
 123 }
 124 EXPORT_SYMBOL_GPL(crypto_put_default_rng);
 125
 126 MODULE_LICENSE("GPL");
 127 MODULE_DESCRIPTION("Random Number Generator");