442 lines
14 KiB
C
442 lines
14 KiB
C
/*
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* TLS 1.3 client-side functions
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS ( https://tls.mbed.org )
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*/
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#include "common.h"
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#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
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#if defined(MBEDTLS_SSL_CLI_C)
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#include <string.h>
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#include "ssl_misc.h"
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#include <mbedtls/debug.h>
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#define CLIENT_HELLO_RANDOM_LEN 32
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#define CLIENT_HELLO_LEGACY_VERSION_LEN 2
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/* Write extensions */
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/*
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* ssl_tls13_write_supported_versions_ext():
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*
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* struct {
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* ProtocolVersion versions<2..254>;
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* } SupportedVersions;
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*/
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static int ssl_tls13_write_supported_versions_ext( mbedtls_ssl_context *ssl,
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unsigned char *buf,
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unsigned char *end,
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size_t *olen )
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{
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unsigned char *p = buf;
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*olen = 0;
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MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding supported versions extension" ) );
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/*
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* Check space for extension header.
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*
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* extension_type 2
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* extension_data_length 2
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* version_length 1
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* versions 2
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*/
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, 7 );
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/* Write extension_type */
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MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS, p, 0 );
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/* Write extension_data_length */
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MBEDTLS_PUT_UINT16_BE( 3, p, 2 );
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p += 4;
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/* Length of versions */
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*p++ = 0x2;
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/* Write values of supported versions.
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*
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* They are defined by the configuration.
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*
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* Currently, only one version is advertised.
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*/
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mbedtls_ssl_write_version( ssl->conf->max_major_ver,
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ssl->conf->max_minor_ver,
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ssl->conf->transport, p );
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MBEDTLS_SSL_DEBUG_MSG( 3, ( "supported version: [%d:%d]",
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ssl->conf->max_major_ver,
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ssl->conf->max_minor_ver ) );
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*olen = 7;
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return( 0 );
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}
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#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
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static int ssl_tls13_write_supported_groups_ext( mbedtls_ssl_context *ssl,
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unsigned char *buf,
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unsigned char *end,
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size_t *olen )
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{
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((void) ssl);
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((void) buf);
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((void) end);
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((void) olen);
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return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
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}
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static int ssl_tls13_write_key_shares_ext( mbedtls_ssl_context *ssl,
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unsigned char *buf,
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unsigned char *end,
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size_t *olen )
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{
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((void) ssl);
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((void) buf);
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((void) end);
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((void) olen);
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return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
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}
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#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
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/*
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* Functions for writing ClientHello message.
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*/
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/* Write cipher_suites
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* CipherSuite cipher_suites<2..2^16-2>;
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*/
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static int ssl_tls13_write_client_hello_cipher_suites(
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mbedtls_ssl_context *ssl,
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unsigned char *buf,
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unsigned char *end,
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size_t *olen )
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{
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const int *ciphersuite_list;
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unsigned char *cipher_suites_ptr; /* Start of the cipher_suites list */
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unsigned char *p; /* Iteration over the cipher_suites list */
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size_t cipher_suites_len;
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*olen = 0 ;
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/*
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* Ciphersuite list
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*
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* This is a list of the symmetric cipher options supported by
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* the client, specifically the record protection algorithm
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* ( including secret key length ) and a hash to be used with
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* HKDF, in descending order of client preference.
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*/
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ciphersuite_list = ssl->conf->ciphersuite_list;
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/* Check there is space for the cipher suite list length (2 bytes). */
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MBEDTLS_SSL_CHK_BUF_PTR( buf, end, 2 );
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/* Write cipher_suites */
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cipher_suites_ptr = buf + 2;
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p = cipher_suites_ptr;
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for ( size_t i = 0; ciphersuite_list[i] != 0; i++ )
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{
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int cipher_suite = ciphersuite_list[i];
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const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
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ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( cipher_suite );
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if( ciphersuite_info == NULL )
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continue;
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if( !( MBEDTLS_SSL_MINOR_VERSION_4 >= ciphersuite_info->min_minor_ver &&
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MBEDTLS_SSL_MINOR_VERSION_4 <= ciphersuite_info->max_minor_ver ) )
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continue;
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MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, add ciphersuite: %04x, %s",
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(unsigned int) cipher_suite,
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ciphersuite_info->name ) );
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/* Check there is space for the cipher suite identifier (2 bytes). */
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, 2 );
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MBEDTLS_PUT_UINT16_BE( cipher_suite, p, 0 );
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p += 2;
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}
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/* Write the cipher_suites length in number of bytes */
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cipher_suites_len = p - cipher_suites_ptr;
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MBEDTLS_PUT_UINT16_BE( cipher_suites_len, buf, 0 );
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MBEDTLS_SSL_DEBUG_MSG( 3,
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( "client hello, got %" MBEDTLS_PRINTF_SIZET " cipher suites",
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cipher_suites_len/2 ) );
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/* Output the total length of cipher_suites field. */
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*olen = p - buf;
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return( 0 );
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}
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/*
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* Structure of ClientHello message:
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*
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* struct {
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* ProtocolVersion legacy_version = 0x0303; // TLS v1.2
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* Random random;
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* opaque legacy_session_id<0..32>;
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* CipherSuite cipher_suites<2..2^16-2>;
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* opaque legacy_compression_methods<1..2^8-1>;
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* Extension extensions<8..2^16-1>;
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* } ClientHello;
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*/
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static int ssl_tls13_write_client_hello_body( mbedtls_ssl_context *ssl,
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unsigned char *buf,
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unsigned char *end,
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size_t *olen )
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{
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int ret;
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unsigned char *extensions_len_ptr; /* Pointer to extensions length */
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size_t output_len; /* Length of buffer used by function */
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size_t extensions_len; /* Length of the list of extensions*/
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/* Buffer management */
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unsigned char *p = buf;
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*olen = 0;
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/* No validation needed here. It has been done by ssl_conf_check() */
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ssl->major_ver = ssl->conf->min_major_ver;
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ssl->minor_ver = ssl->conf->min_minor_ver;
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/*
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* Write legacy_version
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* ProtocolVersion legacy_version = 0x0303; // TLS v1.2
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*
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* For TLS 1.3 we use the legacy version number {0x03, 0x03}
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* instead of the true version number.
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*/
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, CLIENT_HELLO_LEGACY_VERSION_LEN );
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MBEDTLS_PUT_UINT16_BE( 0x0303, p, 0 );
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p += CLIENT_HELLO_LEGACY_VERSION_LEN;
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/* Write the random bytes ( random ).*/
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, CLIENT_HELLO_RANDOM_LEN );
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memcpy( p, ssl->handshake->randbytes, CLIENT_HELLO_RANDOM_LEN );
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MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, random bytes",
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p, CLIENT_HELLO_RANDOM_LEN );
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p += CLIENT_HELLO_RANDOM_LEN;
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/*
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* Write legacy_session_id
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*
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* Versions of TLS before TLS 1.3 supported a "session resumption" feature
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* which has been merged with pre-shared keys in this version. A client
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* which has a cached session ID set by a pre-TLS 1.3 server SHOULD set
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* this field to that value. In compatibility mode, this field MUST be
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* non-empty, so a client not offering a pre-TLS 1.3 session MUST generate
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* a new 32-byte value. This value need not be random but SHOULD be
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* unpredictable to avoid implementations fixating on a specific value
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* ( also known as ossification ). Otherwise, it MUST be set as a zero-length
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* vector ( i.e., a zero-valued single byte length field ).
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*/
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, 1 );
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*p++ = 0; /* session id length set to zero */
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/* Write cipher_suites */
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ret = ssl_tls13_write_client_hello_cipher_suites( ssl, p, end, &output_len );
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if( ret != 0 )
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return( ret );
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p += output_len;
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/* Write legacy_compression_methods
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*
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* For every TLS 1.3 ClientHello, this vector MUST contain exactly
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* one byte set to zero, which corresponds to the 'null' compression
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* method in prior versions of TLS.
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*/
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, 2 );
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*p++ = 1;
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*p++ = MBEDTLS_SSL_COMPRESS_NULL;
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/* Write extensions */
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/* Keeping track of the included extensions */
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ssl->handshake->extensions_present = MBEDTLS_SSL_EXT_NONE;
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/* First write extensions, then the total length */
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MBEDTLS_SSL_CHK_BUF_PTR( p, end, 2 );
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extensions_len_ptr = p;
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p += 2;
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/* Write supported_versions extension
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*
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* Supported Versions Extension is mandatory with TLS 1.3.
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*/
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ret = ssl_tls13_write_supported_versions_ext( ssl, p, end, &output_len );
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if( ret != 0 )
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return( ret );
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p += output_len;
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#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
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/* Write supported_groups extension
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*
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* It is REQUIRED for ECDHE cipher_suites.
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*/
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ret = ssl_tls13_write_supported_groups_ext( ssl, p, end, &output_len );
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if( ret != 0 )
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return( ret );
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p += output_len;
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/* Write key_share extension
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*
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* We need to send the key shares under three conditions:
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* 1) A certificate-based ciphersuite is being offered. In this case
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* supported_groups and supported_signature extensions have been
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* successfully added.
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* 2) A PSK-based ciphersuite with ECDHE is offered. In this case the
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* psk_key_exchange_modes has been added as the last extension.
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* 3) Or, in case all ciphers are supported ( which includes #1 and #2
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* from above )
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*/
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ret = ssl_tls13_write_key_shares_ext( ssl, p, end, &output_len );
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if( ret != 0 )
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return( ret );
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p += output_len;
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/* Write signature_algorithms extension
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*
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* It is REQUIRED for certificate authenticated cipher_suites.
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*/
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ret = mbedtls_ssl_tls13_write_sig_alg_ext( ssl, p, end, &output_len );
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if( ret != 0 )
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return( ret );
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p += output_len;
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#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
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/* Add more extensions here */
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/* Write the length of the list of extensions. */
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extensions_len = p - extensions_len_ptr - 2;
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MBEDTLS_PUT_UINT16_BE( extensions_len, extensions_len_ptr, 0 );
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MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, total extension length: %" MBEDTLS_PRINTF_SIZET ,
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extensions_len ) );
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MBEDTLS_SSL_DEBUG_BUF( 3, "client hello extensions", extensions_len_ptr, extensions_len );
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*olen = p - buf;
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return( 0 );
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}
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static int ssl_tls13_finalize_client_hello( mbedtls_ssl_context* ssl )
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{
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mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_HELLO );
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return( 0 );
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}
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static int ssl_tls13_prepare_client_hello( mbedtls_ssl_context *ssl )
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{
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int ret;
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if( ssl->conf->f_rng == NULL )
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "no RNG provided" ) );
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return( MBEDTLS_ERR_SSL_NO_RNG );
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}
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if( ( ret = ssl->conf->f_rng( ssl->conf->p_rng,
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ssl->handshake->randbytes,
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CLIENT_HELLO_RANDOM_LEN ) ) != 0 )
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{
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MBEDTLS_SSL_DEBUG_RET( 1, "f_rng", ret );
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return( ret );
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}
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return( 0 );
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}
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/*
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* Write ClientHello handshake message.
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*/
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static int ssl_tls13_write_client_hello( mbedtls_ssl_context *ssl )
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{
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int ret = 0;
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unsigned char *buf;
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size_t buf_len, msg_len;
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MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write client hello" ) );
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MBEDTLS_SSL_PROC_CHK( ssl_tls13_prepare_client_hello( ssl ) );
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MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_start_handshake_msg(
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ssl, MBEDTLS_SSL_HS_CLIENT_HELLO,
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&buf, &buf_len ) );
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MBEDTLS_SSL_PROC_CHK( ssl_tls13_write_client_hello_body( ssl, buf,
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buf + buf_len,
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&msg_len ) );
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mbedtls_ssl_tls13_add_hs_hdr_to_checksum( ssl,
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MBEDTLS_SSL_HS_CLIENT_HELLO,
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msg_len );
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ssl->handshake->update_checksum( ssl, buf, msg_len );
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MBEDTLS_SSL_PROC_CHK( ssl_tls13_finalize_client_hello( ssl ) );
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MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_finish_handshake_msg( ssl,
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buf_len,
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msg_len ) );
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cleanup:
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MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write client hello" ) );
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return ret;
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}
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int mbedtls_ssl_tls13_handshake_client_step( mbedtls_ssl_context *ssl )
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{
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int ret = 0;
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MBEDTLS_SSL_DEBUG_MSG( 2, ( "client state: %d", ssl->state ) );
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switch( ssl->state )
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{
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/*
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* ssl->state is initialized as HELLO_REQUEST. It is the same
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* as CLIENT_HELLO state.
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*/
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case MBEDTLS_SSL_HELLO_REQUEST:
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case MBEDTLS_SSL_CLIENT_HELLO:
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ret = ssl_tls13_write_client_hello( ssl );
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break;
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case MBEDTLS_SSL_SERVER_HELLO:
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// Stop here : we haven't finished whole flow
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ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
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mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS );
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break;
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default:
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid state %d", ssl->state ) );
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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}
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return( ret );
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}
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#endif /* MBEDTLS_SSL_CLI_C */
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#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
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