library/ssl_tls13_client.c

/*
 *  TLS 1.3 client-side functions
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  This file is part of mbed TLS ( https://tls.mbed.org )
 */

#include "common.h"

#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)

#if defined(MBEDTLS_SSL_CLI_C)

#include "ssl_misc.h"
#include <mbedtls/debug.h>

/* Main entry point; orchestrates the other functions */
static int ssl_client_hello_process( mbedtls_ssl_context* ssl );

int mbedtls_ssl_handshake_client_step_tls1_3( mbedtls_ssl_context *ssl )
{
    int ret = 0;

    if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER || ssl->handshake == NULL )
    {
        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Handshake completed but ssl->handshake is NULL.\n" ) );
        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
    }

    MBEDTLS_SSL_DEBUG_MSG( 2, ( "client state: %d", ssl->state ) );

    switch( ssl->state )
    {
        case MBEDTLS_SSL_HELLO_REQUEST:
            mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_HELLO );
            break;

        case MBEDTLS_SSL_CLIENT_HELLO:
            ret = ssl_client_hello_process( ssl );
            break;

        case MBEDTLS_SSL_SERVER_HELLO:
            // Stop here : we haven't finished whole flow
            ret=MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
            mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS );
            break;

        default:
            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid state %d", ssl->state ) );
            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
    }

    return( ret );
}


static int ssl_client_hello_prepare( mbedtls_ssl_context* ssl );
static int ssl_client_hello_write_partial( mbedtls_ssl_context* ssl,
                                           unsigned char* buf, size_t buflen,
                                           size_t* len_without_binders,
                                           size_t* len_with_binders );
static int ssl_client_hello_postprocess( mbedtls_ssl_context* ssl );

static int ssl_client_hello_process( mbedtls_ssl_context* ssl )
{
    int ret = 0;
    unsigned char *buf;
    size_t buf_len, msg_len;
    size_t len_without_binders = 0;

    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write client hello" ) );

    MBEDTLS_SSL_PROC_CHK( ssl_client_hello_prepare, ( ssl ) );

    MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_start_handshake_msg, ( ssl,
                 MBEDTLS_SSL_HS_CLIENT_HELLO, &buf, &buf_len ) );

    MBEDTLS_SSL_PROC_CHK( ssl_client_hello_write_partial, ( ssl, buf, buf_len,
                                                  &len_without_binders,
                                                  &msg_len ) );

    mbedtls_ssl_add_hs_hdr_to_checksum( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO,
                                        msg_len );
    ssl->handshake->update_checksum( ssl, buf, len_without_binders );

    MBEDTLS_SSL_PROC_CHK( ssl_client_hello_postprocess, ( ssl ) );
    MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_finish_handshake_msg, ( ssl, buf_len, msg_len ) );

cleanup:

    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write client hello" ) );
    /* client_hello_process haven't finished */
    ret=MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
    return ret;
}

static int ssl_client_hello_prepare( mbedtls_ssl_context* ssl )
{
    int ret;
    size_t rand_bytes_len;

    if( ssl->conf->f_rng == NULL )
    {
        MBEDTLS_SSL_DEBUG_MSG( 1, ( "no RNG provided" ) );
        return( MBEDTLS_ERR_SSL_NO_RNG );
    }

    rand_bytes_len = 32;

    if( ( ret = ssl->conf->f_rng( ssl->conf->p_rng, ssl->handshake->randbytes, rand_bytes_len ) ) != 0 )
    {
        MBEDTLS_SSL_DEBUG_RET( 1, "ssl_generate_random", ret );
        return( ret );
    }

    return( 0 );
}

static int ssl_client_hello_postprocess( mbedtls_ssl_context* ssl )
{
    mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_HELLO );

    return( 0 );
}

static int ssl_client_hello_write_partial( mbedtls_ssl_context* ssl,
                                           unsigned char* buf, size_t buflen,
                                           size_t* len_without_binders,
                                           size_t* len_with_binders )
{
    ((void) ssl);
    ((void) buf);
    ((void) buflen);
    ((void) len_without_binders);
    ((void) len_with_binders);
    return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
}



#endif /* MBEDTLS_SSL_CLI_C */

#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */