/*

 * Copyright (C) 2010-2012 Free Software Foundation, Inc.

 * Copyright (C) 2022 Tobias Heider <tobias.heider@canonical.com>

 *

 * 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 "errors.h"

#include <num.h>

#include <mpi.h>

#include <nettle/bignum.h>  /* includes gmp.h */

static void gnutls_free_zero(void *data, size_t size);

static void *gnutls_realloc_zero(void *data, size_t old_size, size_t new_size);

static void *(*allocfunc)(size_t);

static void *(*reallocfunc)(void *, size_t, size_t);

static void (*freefunc)(void *, size_t);

/* Functions that refer to the initialization of the nettle library.

 */

int gnutls_crypto_init(void)

{

  void *(*defallocfunc)(size_t);

  void *(*defreallocfunc)(void *, size_t, size_t);

  void (*deffreefunc)(void *, size_t);

  /* Check if non-default allocators are being used.

   * Some applications like guile override GMP allocators

   * with GC capable alternatives. Do nothing if this is

   * the case.

   */

  mp_get_memory_functions(&allocfunc, &reallocfunc, &freefunc);

  mp_set_memory_functions(NULL, NULL, NULL);

  mp_get_memory_functions(&defallocfunc, &defreallocfunc, &deffreefunc);

  if (reallocfunc != defreallocfunc || freefunc != deffreefunc) {

    mp_set_memory_functions(allocfunc, reallocfunc, freefunc);

    return (0);

  }

  /* Overload GMP allocators with safe alternatives */

  mp_set_memory_functions(NULL, gnutls_realloc_zero, gnutls_free_zero);

  return 0;

}

/* Functions that refer to the deinitialization of the nettle library.

 */

void gnutls_crypto_deinit(void)

{

  mp_set_memory_functions(allocfunc, reallocfunc, freefunc);

}

/*-

 * gnutls_free_zero:

 * @data: the memory to free

 * @size: the size of memory

 *

 * This function will operate similarly to free(), but will safely

 * zeroize the memory pointed to by data before freeing.

 *

 -*/

static void gnutls_free_zero(void *data, size_t size)

{

  explicit_bzero(data, size);

  free(data);

}

/*-

 * gnutls_realloc_zero:

 * @data: the memory to free

 * @old_size: the size of memory before reallocation

 * @new_size: the size of memory after reallocation

 *

 * This function will operate similarly to realloc(), but will safely

 * zeroize discarded memory.

 *

 -*/

static void *gnutls_realloc_zero(void *data, size_t old_size, size_t new_size)

{

  void *p;

  if (data == NULL || old_size == 0) {

    p = realloc(data, new_size);

    if (p == NULL)

      abort();

    return p;

  }

  if (new_size == 0) {

    explicit_bzero(data, old_size);

    free(data);

    return NULL;

  }

  if (old_size == new_size)

    return data;

  p = malloc(new_size);

  if (p == NULL) {

    explicit_bzero(data, old_size);

    abort();

  }

  memcpy(p, data, MIN(old_size, new_size));

  explicit_bzero(data, old_size);

  free(data);

  return p;

}