/*

 * Copyright (C) 2011-2012 Free Software Foundation, Inc.

 *

 * Author: Nikos Mavrogiannopoulos

 *

 * This file is part of GnuTLS.

 *

 * The GnuTLS is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>

 *

 */

#include "gnutls_int.h"

#include <algorithms.h>

#include "errors.h"

#include <x509/common.h>

typedef struct {

  const char *name;

  gnutls_sec_param_t sec_param;

  unsigned int bits;  /* security level */

  unsigned int pk_bits; /* DH, RSA, SRP */

  unsigned int dsa_bits;  /* bits for DSA. Handled differently since

         * choice of key size in DSA is political.

         */

  unsigned int subgroup_bits; /* subgroup bits */

  unsigned int ecc_bits;  /* bits for ECC keys */

} gnutls_sec_params_entry;

static const gnutls_sec_params_entry sec_params[] = {

  {"Insecure", GNUTLS_SEC_PARAM_INSECURE, 0, 0, 0, 0, 0},

  {"Export", GNUTLS_SEC_PARAM_EXPORT, 42, 512, 0, 84, 0},

  {"Very weak", GNUTLS_SEC_PARAM_VERY_WEAK, 64, 767, 0, 128, 0},

  {"Weak", GNUTLS_SEC_PARAM_WEAK, 72, 1008, 1008, 160, 160},

#ifdef ENABLE_FIPS140

  {"Low", GNUTLS_SEC_PARAM_LOW, 80, 1024, 1024, 160, 160},

  {"Legacy", GNUTLS_SEC_PARAM_LEGACY, 96, 1024, 1024, 192, 192},

  {"Medium", GNUTLS_SEC_PARAM_MEDIUM, 112, 2048, 2048, 224, 224},

  {"High", GNUTLS_SEC_PARAM_HIGH, 128, 3072, 3072, 256, 256},

#else

  {"Low", GNUTLS_SEC_PARAM_LOW, 80, 1024, 1024, 160, 160},  /* ENISA-LEGACY */

  {"Legacy", GNUTLS_SEC_PARAM_LEGACY, 96, 1776, 2048, 192, 192},

  {"Medium", GNUTLS_SEC_PARAM_MEDIUM, 112, 2048, 2048, 256, 224},

  {"High", GNUTLS_SEC_PARAM_HIGH, 128, 3072, 3072, 256, 256},

#endif

  {"Ultra", GNUTLS_SEC_PARAM_ULTRA, 192, 8192, 8192, 384, 384},

  {"Future", GNUTLS_SEC_PARAM_FUTURE, 256, 15360, 15360, 512, 512},

  {NULL, 0, 0, 0, 0, 0}

};

/**

 * gnutls_sec_param_to_pk_bits:

 * @algo: is a public key algorithm

 * @param: is a security parameter

 *

 * When generating private and public key pairs a difficult question

 * is which size of "bits" the modulus will be in RSA and the group size

 * in DSA. The easy answer is 1024, which is also wrong. This function

 * will convert a human understandable security parameter to an

 * appropriate size for the specific algorithm.

 *

 * Returns: The number of bits, or (0).

 *

 * Since: 2.12.0

 **/

unsigned int

gnutls_sec_param_to_pk_bits(gnutls_pk_algorithm_t algo,

          gnutls_sec_param_t param)

{

  unsigned int ret = 0;

  const gnutls_sec_params_entry *p;

  /* handle DSA differently */

  for (p = sec_params; p->name; p++) {

    if (p->sec_param == param) {

      if (algo == GNUTLS_PK_DSA)

        ret = p->dsa_bits;

      else if (IS_EC(algo) || IS_GOSTEC(algo))

        ret = p->ecc_bits;

      else

        ret = p->pk_bits;

      break;

    }

  }

  return ret;

}

/**

 * gnutls_sec_param_to_symmetric_bits:

 * @algo: is a public key algorithm

 * @param: is a security parameter

 *

 * This function will return the number of bits that correspond to

 * symmetric cipher strength for the given security parameter.

 *

 * Returns: The number of bits, or (0).

 *

 * Since: 3.3.0

 **/

unsigned int gnutls_sec_param_to_symmetric_bits(gnutls_sec_param_t param)

{

  unsigned int ret = 0;

  const gnutls_sec_params_entry *p;

  /* handle DSA differently */

  for (p = sec_params; p->name; p++) {

    if (p->sec_param == param) {

      ret = p->bits;

      break;

    }

  }

  return ret;

}

/* Returns the corresponding size for subgroup bits (q),

 * given the group bits (p).

 */

unsigned int _gnutls_pk_bits_to_subgroup_bits(unsigned int pk_bits)

{

  unsigned int ret = 0;

  const gnutls_sec_params_entry *p;

  for (p = sec_params; p->name; p++) {

    ret = p->subgroup_bits;

    if (p->pk_bits >= pk_bits)

      break;

  }

  return ret;

}

/* Returns a corresponding SHA algorithm size for the

 * public key bits given. It is based on the NIST mappings.

 */

gnutls_digest_algorithm_t _gnutls_pk_bits_to_sha_hash(unsigned int pk_bits)

{

  const gnutls_sec_params_entry *p;

  for (p = sec_params; p->name; p++) {

    if (p->pk_bits >= pk_bits) {

      if (p->bits <= 128)

        return GNUTLS_DIG_SHA256;

      else if (p->bits <= 192)

        return GNUTLS_DIG_SHA384;

      else

        return GNUTLS_DIG_SHA512;

    }

  }

  return GNUTLS_DIG_SHA256;

}

/**

 * gnutls_sec_param_get_name:

 * @param: is a security parameter

 *

 * Convert a #gnutls_sec_param_t value to a string.

 *

 * Returns: a pointer to a string that contains the name of the

 *   specified security level, or %NULL.

 *

 * Since: 2.12.0

 **/

const char *gnutls_sec_param_get_name(gnutls_sec_param_t param)

{

  const char *ret = "Unknown";

  const gnutls_sec_params_entry *p;

  for (p = sec_params; p->name; p++) {

    if (p->sec_param == param) {

      ret = p->name;

      break;

    }

  }

  return ret;

}

/**

 * gnutls_pk_bits_to_sec_param:

 * @algo: is a public key algorithm

 * @bits: is the number of bits

 *

 * This is the inverse of gnutls_sec_param_to_pk_bits(). Given an algorithm

 * and the number of bits, it will return the security parameter. This is

 * a rough indication.

 *

 * Returns: The security parameter.

 *

 * Since: 2.12.0

 **/

gnutls_sec_param_t

gnutls_pk_bits_to_sec_param(gnutls_pk_algorithm_t algo, unsigned int bits)

{

  gnutls_sec_param_t ret = GNUTLS_SEC_PARAM_INSECURE;

  const gnutls_sec_params_entry *p;

  if (bits == 0)

    return GNUTLS_SEC_PARAM_UNKNOWN;

  if (IS_EC(algo) || IS_GOSTEC(algo)) {

    for (p = sec_params; p->name; p++) {

      if (p->ecc_bits > bits)

        break;

      ret = p->sec_param;

    }

  } else {

    for (p = sec_params; p->name; p++) {

      if (p->pk_bits > bits)

        break;

      ret = p->sec_param;

    }

  }

  return ret;

}