/*
   * Copyright (c) 2016, Intel Corporation
   * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
   *
   * 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/kernel.h>
  #include <linux/export.h>
  #include <linux/err.h>
  #include <linux/string.h>
  #include <crypto/dh.h>
  #include <crypto/kpp.h>

  #define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))

  static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)

  {

  	if (!dst || size > end - dst)
  		return NULL;

  	memcpy(dst, src, size);
  	return dst + size;
  }
  
  static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
  {
  	memcpy(dst, src, size);
  	return src + size;
  }

  static inline unsigned int dh_data_size(const struct dh *p)

  {

  	return p->key_size + p->p_size + p->q_size + p->g_size;

  }

  unsigned int crypto_dh_key_len(const struct dh *p)

  {
  	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
  }
  EXPORT_SYMBOL_GPL(crypto_dh_key_len);
  
  int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
  {
  	u8 *ptr = buf;

  	u8 * const end = ptr + len;

  	struct kpp_secret secret = {
  		.type = CRYPTO_KPP_SECRET_TYPE_DH,
  		.len = len
  	};

  	if (unlikely(!len))

  		return -EINVAL;

  	ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
  	ptr = dh_pack_data(ptr, end, &params->key_size,
  			   sizeof(params->key_size));
  	ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
  	ptr = dh_pack_data(ptr, end, &params->q_size, sizeof(params->q_size));
  	ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
  	ptr = dh_pack_data(ptr, end, params->key, params->key_size);
  	ptr = dh_pack_data(ptr, end, params->p, params->p_size);
  	ptr = dh_pack_data(ptr, end, params->q, params->q_size);
  	ptr = dh_pack_data(ptr, end, params->g, params->g_size);
  	if (ptr != end)

  		return -EINVAL;

  	return 0;
  }
  EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
  
  int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
  {
  	const u8 *ptr = buf;
  	struct kpp_secret secret;
  
  	if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
  		return -EINVAL;
  
  	ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
  	if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
  		return -EINVAL;
  
  	ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
  	ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));

  	ptr = dh_unpack_data(&params->q_size, ptr, sizeof(params->q_size));

  	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
  	if (secret.len != crypto_dh_key_len(params))
  		return -EINVAL;

  	/*
  	 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
  	 * some drivers assume otherwise.
  	 */
  	if (params->key_size > params->p_size ||

  	    params->g_size > params->p_size || params->q_size > params->p_size)

  		return -EINVAL;

  	/* Don't allocate memory. Set pointers to data within
  	 * the given buffer
  	 */
  	params->key = (void *)ptr;
  	params->p = (void *)(ptr + params->key_size);

  	params->q = (void *)(ptr + params->key_size + params->p_size);
  	params->g = (void *)(ptr + params->key_size + params->p_size +
  			     params->q_size);

  	/*
  	 * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
  	 * to corner cases such as 'mod 0' being undefined or
  	 * crypto_kpp_maxsize() returning 0.
  	 */
  	if (memchr_inv(params->p, 0, params->p_size) == NULL)
  		return -EINVAL;

  	/* It is permissible to not provide Q. */
  	if (params->q_size == 0)
  		params->q = NULL;

  	return 0;
  }
  EXPORT_SYMBOL_GPL(crypto_dh_decode_key);