/*
 * Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation
 *
 * Author: Nikos Mavroyanopoulos
 *
 * This file is part of GNUTLS.
 *
 * The GNUTLS library 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA
 *
 */

/* This file contains common stuff in Ephemeral Diffie Hellman (DHE) and
 * Anonymous DH key exchange(DHA). These are used in the handshake procedure 
 * of the certificate and anoymous authentication.
 */

#include "gnutls_int.h"
#include "gnutls_auth_int.h"
#include "gnutls_errors.h"
#include "gnutls_dh.h"
#include "gnutls_num.h"
#include "gnutls_sig.h"
#include <gnutls_datum.h>
#include <gnutls_x509.h>
#include <gnutls_extra.h>
#include <gnutls_state.h>
#include <auth_dh_common.h>

/* Frees the dh_info_st structure.
 */
void _gnutls_free_dh_info( dh_info_st* dh)
{
    dh->secret_bits = 0;
    _gnutls_free_datum( &dh->prime);
    _gnutls_free_datum( &dh->generator);
    _gnutls_free_datum( &dh->public_key);
}

int _gnutls_proc_dh_common_client_kx(gnutls_session_t session,
				     opaque * data, size_t _data_size,
				     mpi_t g, mpi_t p)
{
    uint16 n_Y;
    size_t _n_Y;
    int ret;
    ssize_t data_size = _data_size;


    DECR_LEN(data_size, 2);
    n_Y = _gnutls_read_uint16(&data[0]);
    _n_Y = n_Y;

    DECR_LEN(data_size, n_Y);
    if (_gnutls_mpi_scan_nz(&session->key->client_Y, &data[2], &_n_Y)) {
	gnutls_assert();
	return GNUTLS_E_MPI_SCAN_FAILED;
    }

    _gnutls_dh_set_peer_public(session, session->key->client_Y);

    session->key->KEY =
	gnutls_calc_dh_key(session->key->client_Y,
			   session->key->dh_secret, p);

    if (session->key->KEY == NULL) {
	gnutls_assert();
	return GNUTLS_E_MEMORY_ERROR;
    }

    _gnutls_mpi_release(&session->key->client_Y);
    _gnutls_mpi_release(&session->key->dh_secret);

    ret = _gnutls_generate_session_key(session->key);
    _gnutls_mpi_release(&session->key->KEY);

    if (ret < 0) {
	return ret;
    }

    return 0;
}

int _gnutls_gen_dh_common_client_kx(gnutls_session_t session,
				    opaque ** data)
{
    mpi_t x = NULL, X = NULL;
    size_t n_X;
    int ret;

    *data = NULL;

    X = gnutls_calc_dh_secret(&x, session->key->client_g,
			      session->key->client_p);
    if (X == NULL || x == NULL) {
	gnutls_assert();
	ret = GNUTLS_E_MEMORY_ERROR;
	goto error;
    }

    _gnutls_dh_set_secret_bits(session, _gnutls_mpi_get_nbits(x));

    _gnutls_mpi_print(NULL, &n_X, X);
    (*data) = gnutls_malloc(n_X + 2);
    if (*data == NULL) {
	ret = GNUTLS_E_MEMORY_ERROR;
	goto error;
    }

    _gnutls_mpi_print(&(*data)[2], &n_X, X);
    _gnutls_mpi_release(&X);

    _gnutls_write_uint16(n_X, &(*data)[0]);

    /* calculate the key after calculating the message */
    session->key->KEY =
	gnutls_calc_dh_key(session->key->client_Y, x,
			   session->key->client_p);

    _gnutls_mpi_release(&x);
    if (session->key->KEY == NULL) {
	gnutls_assert();
	ret = GNUTLS_E_MEMORY_ERROR;
	goto error;
    }

    _gnutls_dh_set_peer_public(session, session->key->client_Y);

    /* THESE SHOULD BE DISCARDED */
    _gnutls_mpi_release(&session->key->client_Y);
    _gnutls_mpi_release(&session->key->client_p);
    _gnutls_mpi_release(&session->key->client_g);

    ret = _gnutls_generate_session_key(session->key);
    _gnutls_mpi_release(&session->key->KEY);

    if (ret < 0) {
	gnutls_assert();
	goto error;
    }

    return n_X + 2;

  error:
    _gnutls_mpi_release(&x);
    _gnutls_mpi_release(&X);
    gnutls_free(*data);
    *data = NULL;
    return ret;
}

int _gnutls_proc_dh_common_server_kx(gnutls_session_t session,
				     opaque * data, size_t _data_size)
{
    uint16 n_Y, n_g, n_p;
    size_t _n_Y, _n_g, _n_p;
    uint8 *data_p;
    uint8 *data_g;
    uint8 *data_Y;
    int i, bits;
    ssize_t data_size = _data_size;

    i = 0;
    DECR_LEN(data_size, 2);
    n_p = _gnutls_read_uint16(&data[i]);
    i += 2;

    DECR_LEN(data_size, n_p);
    data_p = &data[i];
    i += n_p;
    if (i > data_size) {
	gnutls_assert();
	return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
    }
    DECR_LEN(data_size, 2);
    n_g = _gnutls_read_uint16(&data[i]);
    i += 2;

    DECR_LEN(data_size, n_g);
    data_g = &data[i];
    i += n_g;

    DECR_LEN(data_size, 2);
    n_Y = _gnutls_read_uint16(&data[i]);
    i += 2;

    DECR_LEN(data_size, n_Y);
    data_Y = &data[i];
    i += n_Y;

    _n_Y = n_Y;
    _n_g = n_g;
    _n_p = n_p;

    if (_gnutls_mpi_scan_nz(&session->key->client_Y, data_Y, &_n_Y) != 0) {
	gnutls_assert();
	return GNUTLS_E_MPI_SCAN_FAILED;
    }

    if (_gnutls_mpi_scan_nz(&session->key->client_g, data_g, &_n_g) != 0) {
	gnutls_assert();
	return GNUTLS_E_MPI_SCAN_FAILED;
    }
    if (_gnutls_mpi_scan_nz(&session->key->client_p, data_p, &_n_p) != 0) {
	gnutls_assert();
	return GNUTLS_E_MPI_SCAN_FAILED;
    }

    bits = _gnutls_dh_get_allowed_prime_bits(session);
    if (bits < 0) {
	gnutls_assert();
	return bits;
    }

    if (_gnutls_mpi_get_nbits(session->key->client_p) < (size_t) bits) {
	/* the prime used by the peer is not acceptable
	 */
	gnutls_assert();
	return GNUTLS_E_DH_PRIME_UNACCEPTABLE;
    }

    _gnutls_dh_set_group(session, session->key->client_g,
			 session->key->client_p);
    _gnutls_dh_set_peer_public(session, session->key->client_Y);

    return n_Y + n_p + n_g + 6;
}

int _gnutls_dh_common_print_server_kx(gnutls_session_t session,
				      mpi_t g, mpi_t p, opaque ** data)
{
    mpi_t x, X;
    size_t n_X, n_g, n_p;
    int ret;
    uint8 *data_p;
    uint8 *data_g;
    uint8 *data_X;

    X = gnutls_calc_dh_secret(&x, g, p);
    if (X == NULL || x == NULL) {
	gnutls_assert();
	return GNUTLS_E_MEMORY_ERROR;
    }

    session->key->dh_secret = x;
    _gnutls_dh_set_secret_bits(session, _gnutls_mpi_get_nbits(x));

    _gnutls_mpi_print(NULL, &n_g, g);
    _gnutls_mpi_print(NULL, &n_p, p);
    _gnutls_mpi_print(NULL, &n_X, X);
    (*data) = gnutls_malloc(n_g + n_p + n_X + 6);
    if (*data == NULL) {
	_gnutls_mpi_release(&X);
	return GNUTLS_E_MEMORY_ERROR;
    }

    data_p = &(*data)[0];
    _gnutls_mpi_print(&data_p[2], &n_p, p);

    _gnutls_write_uint16(n_p, data_p);

    data_g = &data_p[2 + n_p];
    _gnutls_mpi_print(&data_g[2], &n_g, g);

    _gnutls_write_uint16(n_g, data_g);

    data_X = &data_g[2 + n_g];
    _gnutls_mpi_print(&data_X[2], &n_X, X);
    _gnutls_mpi_release(&X);

    _gnutls_write_uint16(n_X, data_X);

    ret = n_p + n_g + n_X + 6;

    return ret;
}