path: root/lib/auth_rsa.c

/*
 * Copyright (C) 2000, 2001, 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 the RSA key exchange part of the certificate
 * authentication.
 */

#include "gnutls_int.h"
#include "gnutls_auth_int.h"
#include "gnutls_errors.h"
#include "gnutls_dh.h"
#include "gnutls_num.h"
#include "libtasn1.h"
#include "gnutls_datum.h"
#include "auth_cert.h"
#include <gnutls_random.h>
#include <gnutls_pk.h>
#include <gnutls_algorithms.h>
#include <gnutls_global.h>
#include "debug.h"
#include <gnutls_sig.h>
#include <gnutls_x509.h>
#include <gnutls_extra.h>

int _gnutls_gen_rsa_client_kx(gnutls_session_t, opaque **);
int _gnutls_proc_rsa_client_kx(gnutls_session_t, opaque *, size_t);

const mod_auth_st rsa_auth_struct = {
    "RSA",
    _gnutls_gen_cert_server_certificate,
    _gnutls_gen_cert_client_certificate,
    NULL,			/* gen server kx */
    _gnutls_gen_rsa_client_kx,
    _gnutls_gen_cert_client_cert_vrfy,	/* gen client cert vrfy */
    _gnutls_gen_cert_server_cert_req,	/* server cert request */

    _gnutls_proc_cert_server_certificate,
    _gnutls_proc_cert_client_certificate,
    NULL,			/* proc server kx */
    _gnutls_proc_rsa_client_kx,	/* proc client kx */
    _gnutls_proc_cert_client_cert_vrfy,	/* proc client cert vrfy */
    _gnutls_proc_cert_cert_req	/* proc server cert request */
};

/* This function reads the RSA parameters from peer's certificate;
 */
int _gnutls_get_public_rsa_params(gnutls_session_t session,
				  mpi_t params[MAX_PUBLIC_PARAMS_SIZE],
				  int *params_len)
{
    int ret;
    cert_auth_info_t info;
    gnutls_cert peer_cert;
    int i;

    /* normal non export case */

    info = _gnutls_get_auth_info(session);

    if (info == NULL || info->ncerts == 0) {
	gnutls_assert();
	return GNUTLS_E_INTERNAL_ERROR;
    }

    ret =
	_gnutls_raw_cert_to_gcert(&peer_cert,
				  session->security_parameters.cert_type,
				  &info->raw_certificate_list[0],
				  CERT_ONLY_PUBKEY | CERT_NO_COPY);

    if (ret < 0) {
	gnutls_assert();
	return ret;
    }


    /* EXPORT case: */
    if (_gnutls_cipher_suite_get_kx_algo
	(&session->security_parameters.current_cipher_suite)
	== GNUTLS_KX_RSA_EXPORT
	&& _gnutls_mpi_get_nbits(peer_cert.params[0]) > 512) {

	_gnutls_gcert_deinit(&peer_cert);

	if (session->key->rsa[0] == NULL || session->key->rsa[1] == NULL) {
	    gnutls_assert();
	    return GNUTLS_E_INTERNAL_ERROR;
	}

	if (*params_len < 2) {
	    gnutls_assert();
	    return GNUTLS_E_INTERNAL_ERROR;
	}
	*params_len = 2;
	for (i = 0; i < *params_len; i++) {
	    params[i] = _gnutls_mpi_copy(session->key->rsa[i]);
	}

	return 0;
    }

    /* end of export case */

    if (*params_len < peer_cert.params_size) {
	gnutls_assert();
	return GNUTLS_E_INTERNAL_ERROR;
    }
    *params_len = peer_cert.params_size;

    for (i = 0; i < *params_len; i++) {
	params[i] = _gnutls_mpi_copy(peer_cert.params[i]);
    }
    _gnutls_gcert_deinit(&peer_cert);

    return 0;
}

/* This function reads the RSA parameters from the private key
 */
int _gnutls_get_private_rsa_params(gnutls_session_t session,
				   mpi_t ** params, int *params_size)
{
    int bits;
    gnutls_certificate_credentials_t cred;
    gnutls_rsa_params_t rsa_params;

    cred = _gnutls_get_cred(session->key, GNUTLS_CRD_CERTIFICATE, NULL);
    if (cred == NULL) {
	gnutls_assert();
	return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
    }

    if (session->internals.selected_cert_list == NULL) {
	gnutls_assert();
	return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
    }

    bits =
	_gnutls_mpi_get_nbits(session->internals.selected_cert_list[0].
			      params[0]);

    if (_gnutls_cipher_suite_get_kx_algo
	(&session->security_parameters.current_cipher_suite)
	== GNUTLS_KX_RSA_EXPORT && bits > 512) {

	rsa_params = _gnutls_certificate_get_rsa_params(cred, session);
	/* EXPORT case: */
	if (rsa_params == NULL) {
	    gnutls_assert();
	    return GNUTLS_E_NO_TEMPORARY_RSA_PARAMS;
	}

	/* In the export case, we do use temporary RSA params
	 * of 512 bits size. The params in the certificate are
	 * used to sign this temporary stuff.
	 */
	*params_size = RSA_PRIVATE_PARAMS;
	*params = rsa_params->params;

	return 0;
    }

    /* non export cipher suites. */

    *params_size = session->internals.selected_key->params_size;
    *params = session->internals.selected_key->params;

    return 0;
}



#define RANDOMIZE_KEY(x, galloc, rand) x.size=TLS_MASTER_SIZE; x.data=galloc(x.size); \
		if (x.data==NULL) return GNUTLS_E_MEMORY_ERROR; \
		if (_gnutls_get_random( x.data, x.size, rand) < 0) { \
			gnutls_assert(); \
			return GNUTLS_E_MEMORY_ERROR; \
		}

int _gnutls_proc_rsa_client_kx(gnutls_session_t session, opaque * data,
			       size_t _data_size)
{
    gnutls_datum_t plaintext;
    gnutls_datum_t ciphertext;
    int ret, dsize;
    mpi_t *params;
    int params_len;
    int randomize_key = 0;
    ssize_t data_size = _data_size;

    if (gnutls_protocol_get_version(session) == GNUTLS_SSL3) {
	/* SSL 3.0 
	 */
	ciphertext.data = data;
	ciphertext.size = data_size;
    } else {
	/* TLS 1.0
	 */
	DECR_LEN(data_size, 2);
	ciphertext.data = &data[2];
	dsize = _gnutls_read_uint16(data);

	if (dsize != data_size) {
	    gnutls_assert();
	    return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
	}
	ciphertext.size = dsize;
    }

    ret = _gnutls_get_private_rsa_params(session, &params, &params_len);
    if (ret < 0) {
	gnutls_assert();
	return ret;
    }

    ret = _gnutls_pkcs1_rsa_decrypt(&plaintext, &ciphertext, params, params_len, 2);	/* btype==2 */

    if (ret < 0 || plaintext.size != TLS_MASTER_SIZE) {
	/* In case decryption fails then don't inform
	 * the peer. Just use a random key. (in order to avoid
	 * attack against pkcs-1 formating).
	 */
	gnutls_assert();
	_gnutls_x509_log("auth_rsa: Possible PKCS #1 format attack\n");
	randomize_key = 1;
    } else {
	/* If the secret was properly formatted, then
	 * check the version number.
	 */
	if (_gnutls_get_adv_version_major(session) != plaintext.data[0]
	    || _gnutls_get_adv_version_minor(session) != plaintext.data[1]) {
	    /* No error is returned here, if the version number check
	     * fails. We proceed normally.
	     * That is to defend against the attack described in the paper
	     * "Attacking RSA-based sessions in SSL/TLS" by Vlastimil Klima,
	     * Ondej Pokorny and Tomas Rosa.
	     */
	    gnutls_assert();
	    _gnutls_x509_log
		("auth_rsa: Possible PKCS #1 version check format attack\n");
	}
    }

    if (randomize_key != 0) {
	/* we do not need strong random numbers here.
	 */
	RANDOMIZE_KEY(session->key->key,
		      gnutls_malloc, GNUTLS_WEAK_RANDOM);

    } else {
	session->key->key.data = plaintext.data;
	session->key->key.size = plaintext.size;
    }

    /* This is here to avoid the version check attack
     * discussed above.
     */
    session->key->key.data[0] = _gnutls_get_adv_version_major(session);
    session->key->key.data[1] = _gnutls_get_adv_version_minor(session);

    return 0;
}



/* return RSA(random) using the peers public key 
 */
int _gnutls_gen_rsa_client_kx(gnutls_session_t session, opaque ** data)
{
    cert_auth_info_t auth = session->key->auth_info;
    gnutls_datum_t sdata;	/* data to send */
    mpi_t params[MAX_PUBLIC_PARAMS_SIZE];
    int params_len = MAX_PUBLIC_PARAMS_SIZE;
    int ret, i;
    gnutls_protocol_t ver;

    if (auth == NULL) {
	/* this shouldn't have happened. The proc_certificate
	 * function should have detected that.
	 */
	gnutls_assert();
	return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
    }
    RANDOMIZE_KEY(session->key->key, gnutls_secure_malloc,
		  GNUTLS_STRONG_RANDOM);

    ver = _gnutls_get_adv_version(session);

    if (session->internals.rsa_pms_version[0] == 0) {
	session->key->key.data[0] = _gnutls_version_get_major(ver);
	session->key->key.data[1] = _gnutls_version_get_minor(ver);
    } else {			/* use the version provided */
	session->key->key.data[0] = session->internals.rsa_pms_version[0];
	session->key->key.data[1] = session->internals.rsa_pms_version[1];
    }

    /* move RSA parameters to key (session).
     */
    if ((ret =
	 _gnutls_get_public_rsa_params(session, params,
				       &params_len)) < 0) {
	gnutls_assert();
	return ret;
    }

    if ((ret =
	 _gnutls_pkcs1_rsa_encrypt(&sdata, &session->key->key,
				   params, params_len, 2)) < 0) {
	gnutls_assert();
	return ret;
    }

    for (i = 0; i < params_len; i++)
	_gnutls_mpi_release(&params[i]);

    if (gnutls_protocol_get_version(session) == GNUTLS_SSL3) {
	/* SSL 3.0 */
	*data = sdata.data;
	return sdata.size;
    } else {			/* TLS 1 */
	*data = gnutls_malloc(sdata.size + 2);
	if (*data == NULL) {
	    _gnutls_free_datum(&sdata);
	    return GNUTLS_E_MEMORY_ERROR;
	}
	_gnutls_write_datum16(*data, sdata);
	ret = sdata.size + 2;
	_gnutls_free_datum(&sdata);
	return ret;
    }

}