/*
   * Cryptographic API.
   *
   * RNG operations.
   *
   * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>

   * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>

   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   *
   */

  #include <linux/atomic.h>

  #include <crypto/internal/rng.h>
  #include <linux/err.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/random.h>
  #include <linux/seq_file.h>

  #include <linux/slab.h>

  #include <linux/string.h>

  #include <linux/cryptouser.h>
  #include <net/netlink.h>

  #include "internal.h"

  static DEFINE_MUTEX(crypto_default_rng_lock);
  struct crypto_rng *crypto_default_rng;
  EXPORT_SYMBOL_GPL(crypto_default_rng);
  static int crypto_default_rng_refcnt;

  static inline struct crypto_rng *__crypto_rng_cast(struct crypto_tfm *tfm)
  {
  	return container_of(tfm, struct crypto_rng, base);
  }

  int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)

  {
  	u8 *buf = NULL;
  	int err;
  
  	if (!seed && slen) {
  		buf = kmalloc(slen, GFP_KERNEL);
  		if (!buf)
  			return -ENOMEM;
  
  		get_random_bytes(buf, slen);
  		seed = buf;
  	}

  	err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);

  	kzfree(buf);

  	return err;
  }

  EXPORT_SYMBOL_GPL(crypto_rng_reset);

  static int crypto_rng_init_tfm(struct crypto_tfm *tfm)

  {

  	return 0;
  }

  static unsigned int seedsize(struct crypto_alg *alg)
  {
  	struct rng_alg *ralg = container_of(alg, struct rng_alg, base);

  	return ralg->seedsize;

  }

  #ifdef CONFIG_NET

  static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
  {
  	struct crypto_report_rng rrng;

  	strncpy(rrng.type, "rng", sizeof(rrng.type));

  	rrng.seedsize = seedsize(alg);

  	if (nla_put(skb, CRYPTOCFGA_REPORT_RNG,
  		    sizeof(struct crypto_report_rng), &rrng))
  		goto nla_put_failure;

  	return 0;
  
  nla_put_failure:
  	return -EMSGSIZE;
  }

  #else
  static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
  {
  	return -ENOSYS;
  }
  #endif

  static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
  	__attribute__ ((unused));
  static void crypto_rng_show(struct seq_file *m, struct crypto_alg *alg)
  {
  	seq_printf(m, "type         : rng
  ");

  	seq_printf(m, "seedsize     : %u
  ", seedsize(alg));

  }

  static const struct crypto_type crypto_rng_type = {

  	.extsize = crypto_alg_extsize,
  	.init_tfm = crypto_rng_init_tfm,

  #ifdef CONFIG_PROC_FS
  	.show = crypto_rng_show,
  #endif

  	.report = crypto_rng_report,

  	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
  	.maskset = CRYPTO_ALG_TYPE_MASK,
  	.type = CRYPTO_ALG_TYPE_RNG,
  	.tfmsize = offsetof(struct crypto_rng, base),

  };

  struct crypto_rng *crypto_alloc_rng(const char *alg_name, u32 type, u32 mask)
  {
  	return crypto_alloc_tfm(alg_name, &crypto_rng_type, type, mask);
  }
  EXPORT_SYMBOL_GPL(crypto_alloc_rng);

  int crypto_get_default_rng(void)
  {
  	struct crypto_rng *rng;
  	int err;
  
  	mutex_lock(&crypto_default_rng_lock);
  	if (!crypto_default_rng) {
  		rng = crypto_alloc_rng("stdrng", 0, 0);
  		err = PTR_ERR(rng);
  		if (IS_ERR(rng))
  			goto unlock;
  
  		err = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng));
  		if (err) {
  			crypto_free_rng(rng);
  			goto unlock;
  		}
  
  		crypto_default_rng = rng;
  	}
  
  	crypto_default_rng_refcnt++;
  	err = 0;
  
  unlock:
  	mutex_unlock(&crypto_default_rng_lock);
  
  	return err;
  }
  EXPORT_SYMBOL_GPL(crypto_get_default_rng);
  
  void crypto_put_default_rng(void)
  {
  	mutex_lock(&crypto_default_rng_lock);

  	crypto_default_rng_refcnt--;

  	mutex_unlock(&crypto_default_rng_lock);
  }
  EXPORT_SYMBOL_GPL(crypto_put_default_rng);

  #if defined(CONFIG_CRYPTO_RNG) || defined(CONFIG_CRYPTO_RNG_MODULE)
  int crypto_del_default_rng(void)
  {
  	int err = -EBUSY;
  
  	mutex_lock(&crypto_default_rng_lock);
  	if (crypto_default_rng_refcnt)
  		goto out;
  
  	crypto_free_rng(crypto_default_rng);
  	crypto_default_rng = NULL;
  
  	err = 0;
  
  out:
  	mutex_unlock(&crypto_default_rng_lock);
  
  	return err;
  }
  EXPORT_SYMBOL_GPL(crypto_del_default_rng);
  #endif

  int crypto_register_rng(struct rng_alg *alg)
  {
  	struct crypto_alg *base = &alg->base;
  
  	if (alg->seedsize > PAGE_SIZE / 8)
  		return -EINVAL;
  
  	base->cra_type = &crypto_rng_type;
  	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
  	base->cra_flags |= CRYPTO_ALG_TYPE_RNG;
  
  	return crypto_register_alg(base);
  }
  EXPORT_SYMBOL_GPL(crypto_register_rng);
  
  void crypto_unregister_rng(struct rng_alg *alg)
  {
  	crypto_unregister_alg(&alg->base);
  }
  EXPORT_SYMBOL_GPL(crypto_unregister_rng);

  int crypto_register_rngs(struct rng_alg *algs, int count)
  {
  	int i, ret;
  
  	for (i = 0; i < count; i++) {
  		ret = crypto_register_rng(algs + i);
  		if (ret)
  			goto err;
  	}
  
  	return 0;
  
  err:
  	for (--i; i >= 0; --i)
  		crypto_unregister_rng(algs + i);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(crypto_register_rngs);
  
  void crypto_unregister_rngs(struct rng_alg *algs, int count)
  {
  	int i;
  
  	for (i = count - 1; i >= 0; --i)
  		crypto_unregister_rng(algs + i);
  }
  EXPORT_SYMBOL_GPL(crypto_unregister_rngs);

  MODULE_LICENSE("GPL");

  MODULE_DESCRIPTION("Random Number Generator");