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mbedtls/library/ssl_tls13_client.c
Gabor Mezei 078e803d2c
Unify parsing of the signature algorithms extension 
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
2022-05-11 14:29:08 +02:00

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/*
* 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_CLI_C) && defined(MBEDTLS_SSL_PROTO_TLS1_3)
#include <string.h>
#include "mbedtls/debug.h"
#include "mbedtls/error.h"
#include "mbedtls/platform.h"
#include "ssl_misc.h"
#include "ssl_client.h"
#include "ssl_tls13_keys.h"
/* Write extensions */
/*
* ssl_tls13_write_supported_versions_ext():
*
* struct {
* ProtocolVersion versions<2..254>;
* } SupportedVersions;
*/
static int ssl_tls13_write_supported_versions_ext( mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
size_t *out_len )
{
unsigned char *p = buf;
unsigned char versions_len = ( ssl->handshake->min_tls_version <=
MBEDTLS_SSL_VERSION_TLS1_2 ) ? 4 : 2;
*out_len = 0;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding supported versions extension" ) );
/* Check if we have space to write the extension:
* - extension_type (2 bytes)
* - extension_data_length (2 bytes)
* - versions_length (1 byte )
* - versions (2 or 4 bytes)
*/
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 5 + versions_len );
MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS, p, 0 );
MBEDTLS_PUT_UINT16_BE( versions_len + 1, p, 2 );
p += 4;
/* Length of versions */
*p++ = versions_len;
/* Write values of supported versions.
* They are defined by the configuration.
* Currently, we advertise only TLS 1.3 or both TLS 1.3 and TLS 1.2.
*/
mbedtls_ssl_write_version( p, MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_VERSION_TLS1_3 );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "supported version: [3:4]" ) );
if( ssl->handshake->min_tls_version <= MBEDTLS_SSL_VERSION_TLS1_2 )
{
mbedtls_ssl_write_version( p + 2, MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_VERSION_TLS1_2 );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "supported version: [3:3]" ) );
}
*out_len = 5 + versions_len;
return( 0 );
}
static int ssl_tls13_parse_supported_versions_ext( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
((void) ssl);
MBEDTLS_SSL_CHK_BUF_READ_PTR( buf, end, 2 );
if( mbedtls_ssl_read_version( buf, ssl->conf->transport ) !=
MBEDTLS_SSL_VERSION_TLS1_3 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "unexpected version" ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER);
return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
}
if( &buf[2] != end )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "supported_versions ext data length incorrect" ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR,
MBEDTLS_ERR_SSL_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_DECODE_ERROR );
}
return( 0 );
}
#if defined(MBEDTLS_SSL_ALPN)
static int ssl_tls13_parse_alpn_ext( mbedtls_ssl_context *ssl,
const unsigned char *buf, size_t len )
{
size_t list_len, name_len;
const unsigned char *p = buf;
const unsigned char *end = buf + len;
/* If we didn't send it, the server shouldn't send it */
if( ssl->conf->alpn_list == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
/*
* opaque ProtocolName<1..2^8-1>;
*
* struct {
* ProtocolName protocol_name_list<2..2^16-1>
* } ProtocolNameList;
*
* the "ProtocolNameList" MUST contain exactly one "ProtocolName"
*/
/* Min length is 2 ( list_len ) + 1 ( name_len ) + 1 ( name ) */
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 4 );
list_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, list_len );
name_len = *p++;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, list_len - 1 );
/* Check that the server chosen protocol was in our list and save it */
for ( const char **alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++ )
{
if( name_len == strlen( *alpn ) &&
memcmp( buf + 3, *alpn, name_len ) == 0 )
{
ssl->alpn_chosen = *alpn;
return( 0 );
}
}
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
#endif /* MBEDTLS_SSL_ALPN */
static int ssl_tls13_reset_key_share( mbedtls_ssl_context *ssl )
{
uint16_t group_id = ssl->handshake->offered_group_id;
if( group_id == 0 )
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
#if defined(MBEDTLS_ECDH_C)
if( mbedtls_ssl_tls13_named_group_is_ecdhe( group_id ) )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
/* Destroy generated private key. */
status = psa_destroy_key( ssl->handshake->ecdh_psa_privkey );
if( status != PSA_SUCCESS )
{
ret = psa_ssl_status_to_mbedtls( status );
MBEDTLS_SSL_DEBUG_RET( 1, "psa_destroy_key", ret );
return( ret );
}
ssl->handshake->ecdh_psa_privkey = MBEDTLS_SVC_KEY_ID_INIT;
return( 0 );
}
else
#endif /* MBEDTLS_ECDH_C */
if( 0 /* other KEMs? */ )
{
/* Do something */
}
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
/*
* Functions for writing key_share extension.
*/
static int ssl_tls13_get_default_group_id( mbedtls_ssl_context *ssl,
uint16_t *group_id )
{
int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
#if defined(MBEDTLS_ECDH_C)
const uint16_t *group_list = mbedtls_ssl_get_groups( ssl );
/* Pick first available ECDHE group compatible with TLS 1.3 */
if( group_list == NULL )
return( MBEDTLS_ERR_SSL_BAD_CONFIG );
for ( ; *group_list != 0; group_list++ )
{
const mbedtls_ecp_curve_info *curve_info;
curve_info = mbedtls_ecp_curve_info_from_tls_id( *group_list );
if( curve_info != NULL &&
mbedtls_ssl_tls13_named_group_is_ecdhe( *group_list ) )
{
*group_id = *group_list;
return( 0 );
}
}
#else
((void) ssl);
((void) group_id);
#endif /* MBEDTLS_ECDH_C */
/*
* Add DHE named groups here.
* Pick first available DHE group compatible with TLS 1.3
*/
return( ret );
}
/*
* ssl_tls13_write_key_share_ext
*
* Structure of key_share extension in ClientHello:
*
* struct {
* NamedGroup group;
* opaque key_exchange<1..2^16-1>;
* } KeyShareEntry;
* struct {
* KeyShareEntry client_shares<0..2^16-1>;
* } KeyShareClientHello;
*/
static int ssl_tls13_write_key_share_ext( mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
size_t *out_len )
{
unsigned char *p = buf;
unsigned char *client_shares; /* Start of client_shares */
size_t client_shares_len; /* Length of client_shares */
uint16_t group_id;
int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
*out_len = 0;
/* Check if we have space for header and length fields:
* - extension_type (2 bytes)
* - extension_data_length (2 bytes)
* - client_shares_length (2 bytes)
*/
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 );
p += 6;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello: adding key share extension" ) );
/* HRR could already have requested something else. */
group_id = ssl->handshake->offered_group_id;
if( !mbedtls_ssl_tls13_named_group_is_ecdhe( group_id ) &&
!mbedtls_ssl_tls13_named_group_is_dhe( group_id ) )
{
MBEDTLS_SSL_PROC_CHK( ssl_tls13_get_default_group_id( ssl,
&group_id ) );
}
/*
* Dispatch to type-specific key generation function.
*
* So far, we're only supporting ECDHE. With the introduction
* of PQC KEMs, we'll want to have multiple branches, one per
* type of KEM, and dispatch to the corresponding crypto. And
* only one key share entry is allowed.
*/
client_shares = p;
#if defined(MBEDTLS_ECDH_C)
if( mbedtls_ssl_tls13_named_group_is_ecdhe( group_id ) )
{
/* Pointer to group */
unsigned char *group = p;
/* Length of key_exchange */
size_t key_exchange_len = 0;
/* Check there is space for header of KeyShareEntry
* - group (2 bytes)
* - key_exchange_length (2 bytes)
*/
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4 );
p += 4;
ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
ssl, group_id, p, end, &key_exchange_len );
p += key_exchange_len;
if( ret != 0 )
return( ret );
/* Write group */
MBEDTLS_PUT_UINT16_BE( group_id, group, 0 );
/* Write key_exchange_length */
MBEDTLS_PUT_UINT16_BE( key_exchange_len, group, 2 );
}
else
#endif /* MBEDTLS_ECDH_C */
if( 0 /* other KEMs? */ )
{
/* Do something */
}
else
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
/* Length of client_shares */
client_shares_len = p - client_shares;
if( client_shares_len == 0)
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "No key share defined." ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
/* Write extension_type */
MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_KEY_SHARE, buf, 0 );
/* Write extension_data_length */
MBEDTLS_PUT_UINT16_BE( client_shares_len + 2, buf, 2 );
/* Write client_shares_length */
MBEDTLS_PUT_UINT16_BE( client_shares_len, buf, 4 );
/* Update offered_group_id field */
ssl->handshake->offered_group_id = group_id;
/* Output the total length of key_share extension. */
*out_len = p - buf;
MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, key_share extension", buf, *out_len );
ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_KEY_SHARE;
cleanup:
return( ret );
}
/*
* ssl_tls13_parse_hrr_key_share_ext()
* Parse key_share extension in Hello Retry Request
*
* struct {
* NamedGroup selected_group;
* } KeyShareHelloRetryRequest;
*/
static int ssl_tls13_parse_hrr_key_share_ext( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
const mbedtls_ecp_curve_info *curve_info = NULL;
const unsigned char *p = buf;
int selected_group;
int found = 0;
const uint16_t *group_list = mbedtls_ssl_get_groups( ssl );
if( group_list == NULL )
return( MBEDTLS_ERR_SSL_BAD_CONFIG );
MBEDTLS_SSL_DEBUG_BUF( 3, "key_share extension", p, end - buf );
/* Read selected_group */
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
selected_group = MBEDTLS_GET_UINT16_BE( p, 0 );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "selected_group ( %d )", selected_group ) );
/* Upon receipt of this extension in a HelloRetryRequest, the client
* MUST first verify that the selected_group field corresponds to a
* group which was provided in the "supported_groups" extension in the
* original ClientHello.
* The supported_group was based on the info in ssl->conf->group_list.
*
* If the server provided a key share that was not sent in the ClientHello
* then the client MUST abort the handshake with an "illegal_parameter" alert.
*/
for( ; *group_list != 0; group_list++ )
{
curve_info = mbedtls_ecp_curve_info_from_tls_id( *group_list );
if( curve_info == NULL || curve_info->tls_id != selected_group )
continue;
/* We found a match */
found = 1;
break;
}
/* Client MUST verify that the selected_group field does not
* correspond to a group which was provided in the "key_share"
* extension in the original ClientHello. If the server sent an
* HRR message with a key share already provided in the
* ClientHello then the client MUST abort the handshake with
* an "illegal_parameter" alert.
*/
if( found == 0 || selected_group == ssl->handshake->offered_group_id )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Invalid key share in HRR" ) );
MBEDTLS_SSL_PEND_FATAL_ALERT(
MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
}
/* Remember server's preference for next ClientHello */
ssl->handshake->offered_group_id = selected_group;
return( 0 );
}
/*
* ssl_tls13_parse_key_share_ext()
* Parse key_share extension in Server Hello
*
* struct {
* KeyShareEntry server_share;
* } KeyShareServerHello;
* struct {
* NamedGroup group;
* opaque key_exchange<1..2^16-1>;
* } KeyShareEntry;
*/
static int ssl_tls13_parse_key_share_ext( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const unsigned char *p = buf;
uint16_t group, offered_group;
/* ...
* NamedGroup group; (2 bytes)
* ...
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
group = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
/* Check that the chosen group matches the one we offered. */
offered_group = ssl->handshake->offered_group_id;
if( offered_group != group )
{
MBEDTLS_SSL_DEBUG_MSG( 1,
( "Invalid server key share, our group %u, their group %u",
(unsigned) offered_group, (unsigned) group ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE,
MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
}
#if defined(MBEDTLS_ECDH_C)
if( mbedtls_ssl_tls13_named_group_is_ecdhe( group ) )
{
const mbedtls_ecp_curve_info *curve_info =
mbedtls_ecp_curve_info_from_tls_id( group );
if( curve_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Invalid TLS curve group id" ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
MBEDTLS_SSL_DEBUG_MSG( 2, ( "ECDH curve: %s", curve_info->name ) );
ret = mbedtls_ssl_tls13_read_public_ecdhe_share( ssl, p, end - p );
if( ret != 0 )
return( ret );
}
else
#endif /* MBEDTLS_ECDH_C */
if( 0 /* other KEMs? */ )
{
/* Do something */
}
else
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_KEY_SHARE;
return( ret );
}
/*
* ssl_tls13_parse_cookie_ext()
* Parse cookie extension in Hello Retry Request
*
* struct {
* opaque cookie<1..2^16-1>;
* } Cookie;
*
* When sending a HelloRetryRequest, the server MAY provide a "cookie"
* extension to the client (this is an exception to the usual rule that
* the only extensions that may be sent are those that appear in the
* ClientHello). When sending the new ClientHello, the client MUST copy
* the contents of the extension received in the HelloRetryRequest into
* a "cookie" extension in the new ClientHello. Clients MUST NOT use
* cookies in their initial ClientHello in subsequent connections.
*/
static int ssl_tls13_parse_cookie_ext( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
uint16_t cookie_len;
const unsigned char *p = buf;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
/* Retrieve length field of cookie */
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
cookie_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, cookie_len );
MBEDTLS_SSL_DEBUG_BUF( 3, "cookie extension", p, cookie_len );
mbedtls_free( handshake->cookie );
handshake->hrr_cookie_len = 0;
handshake->cookie = mbedtls_calloc( 1, cookie_len );
if( handshake->cookie == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1,
( "alloc failed ( %ud bytes )",
cookie_len ) );
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
}
memcpy( handshake->cookie, p, cookie_len );
handshake->hrr_cookie_len = cookie_len;
return( 0 );
}
static int ssl_tls13_write_cookie_ext( mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
size_t *out_len )
{
unsigned char *p = buf;
*out_len = 0;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
if( handshake->cookie == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 3, ( "no cookie to send; skip extension" ) );
return( 0 );
}
MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, cookie",
handshake->cookie,
handshake->hrr_cookie_len );
MBEDTLS_SSL_CHK_BUF_PTR( p, end, handshake->hrr_cookie_len + 6 );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding cookie extension" ) );
MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_COOKIE, p, 0 );
MBEDTLS_PUT_UINT16_BE( handshake->hrr_cookie_len + 2, p, 2 );
MBEDTLS_PUT_UINT16_BE( handshake->hrr_cookie_len, p, 4 );
p += 6;
/* Cookie */
memcpy( p, handshake->cookie, handshake->hrr_cookie_len );
*out_len = handshake->hrr_cookie_len + 6;
return( 0 );
}
int mbedtls_ssl_tls13_write_client_hello_exts( mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
size_t *out_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char *p = buf;
size_t ext_len;
*out_len = 0;
/* Write supported_versions extension
*
* Supported Versions Extension is mandatory with TLS 1.3.
*/
ret = ssl_tls13_write_supported_versions_ext( ssl, p, end, &ext_len );
if( ret != 0 )
return( ret );
p += ext_len;
/* Echo the cookie if the server provided one in its preceding
* HelloRetryRequest message.
*/
ret = ssl_tls13_write_cookie_ext( ssl, p, end, &ext_len );
if( ret != 0 )
return( ret );
p += ext_len;
if( mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
{
ret = ssl_tls13_write_key_share_ext( ssl, p, end, &ext_len );
if( ret != 0 )
return( ret );
p += ext_len;
}
*out_len = p - buf;
return( 0 );
}
/*
* Functions for parsing and processing Server Hello
*/
/**
* \brief Detect if the ServerHello contains a supported_versions extension
* or not.
*
* \param[in] ssl SSL context
* \param[in] buf Buffer containing the ServerHello message
* \param[in] end End of the buffer containing the ServerHello message
*
* \return 0 if the ServerHello does not contain a supported_versions extension
* \return 1 if the ServerHello contains a supported_versions extension
* \return A negative value if an error occurred while parsing the ServerHello.
*/
static int ssl_tls13_is_supported_versions_ext_present(
mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
const unsigned char *p = buf;
size_t legacy_session_id_echo_len;
size_t extensions_len;
const unsigned char *extensions_end;
/*
* Check there is enough data to access the legacy_session_id_echo vector
* length:
* - legacy_version 2 bytes
* - random MBEDTLS_SERVER_HELLO_RANDOM_LEN bytes
* - legacy_session_id_echo length 1 byte
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN + 3 );
p += MBEDTLS_SERVER_HELLO_RANDOM_LEN + 2;
legacy_session_id_echo_len = *p;
/*
* Jump to the extensions, jumping over:
* - legacy_session_id_echo (legacy_session_id_echo_len + 1) bytes
* - cipher_suite 2 bytes
* - legacy_compression_method 1 byte
*/
p += legacy_session_id_echo_len + 4;
/* Case of no extension */
if( p == end )
return( 0 );
/* ...
* Extension extensions<6..2^16-1>;
* ...
* struct {
* ExtensionType extension_type; (2 bytes)
* opaque extension_data<0..2^16-1>;
* } Extension;
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
/* Check extensions do not go beyond the buffer of data. */
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len );
extensions_end = p + extensions_len;
while( p < extensions_end )
{
unsigned int extension_type;
size_t extension_data_len;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, 4 );
extension_type = MBEDTLS_GET_UINT16_BE( p, 0 );
extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 );
p += 4;
if( extension_type == MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS )
return( 1 );
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len );
p += extension_data_len;
}
return( 0 );
}
/* Returns a negative value on failure, and otherwise
* - 1 if the last eight bytes of the ServerHello random bytes indicate that
* the server is TLS 1.3 capable but negotiating TLS 1.2 or below.
* - 0 otherwise
*/
static int ssl_tls13_is_downgrade_negotiation( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
/* First seven bytes of the magic downgrade strings, see RFC 8446 4.1.3 */
static const unsigned char magic_downgrade_string[] =
{ 0x44, 0x4F, 0x57, 0x4E, 0x47, 0x52, 0x44 };
const unsigned char *last_eight_bytes_of_random;
unsigned char last_byte_of_random;
MBEDTLS_SSL_CHK_BUF_READ_PTR( buf, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN + 2 );
last_eight_bytes_of_random = buf + 2 + MBEDTLS_SERVER_HELLO_RANDOM_LEN - 8;
if( memcmp( last_eight_bytes_of_random,
magic_downgrade_string,
sizeof( magic_downgrade_string ) ) == 0 )
{
last_byte_of_random = last_eight_bytes_of_random[7];
return( last_byte_of_random == 0 ||
last_byte_of_random == 1 );
}
return( 0 );
}
/* Returns a negative value on failure, and otherwise
* - SSL_SERVER_HELLO_COORDINATE_HELLO or
* - SSL_SERVER_HELLO_COORDINATE_HRR
* to indicate which message is expected and to be parsed next.
*/
#define SSL_SERVER_HELLO_COORDINATE_HELLO 0
#define SSL_SERVER_HELLO_COORDINATE_HRR 1
static int ssl_server_hello_is_hrr( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
/* Check whether this message is a HelloRetryRequest ( HRR ) message.
*
* Server Hello and HRR are only distinguished by Random set to the
* special value of the SHA-256 of "HelloRetryRequest".
*
* struct {
* ProtocolVersion legacy_version = 0x0303;
* Random random;
* opaque legacy_session_id_echo<0..32>;
* CipherSuite cipher_suite;
* uint8 legacy_compression_method = 0;
* Extension extensions<6..2^16-1>;
* } ServerHello;
*
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( buf, end,
2 + sizeof( mbedtls_ssl_tls13_hello_retry_request_magic ) );
if( memcmp( buf + 2, mbedtls_ssl_tls13_hello_retry_request_magic,
sizeof( mbedtls_ssl_tls13_hello_retry_request_magic ) ) == 0 )
{
return( SSL_SERVER_HELLO_COORDINATE_HRR );
}
return( SSL_SERVER_HELLO_COORDINATE_HELLO );
}
/* Fetch and preprocess
* Returns a negative value on failure, and otherwise
* - SSL_SERVER_HELLO_COORDINATE_HELLO or
* - SSL_SERVER_HELLO_COORDINATE_HRR or
* - SSL_SERVER_HELLO_COORDINATE_TLS1_2
*/
#define SSL_SERVER_HELLO_COORDINATE_TLS1_2 2
static int ssl_tls13_server_hello_coordinate( mbedtls_ssl_context *ssl,
unsigned char **buf,
size_t *buf_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const unsigned char *end;
MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl,
MBEDTLS_SSL_HS_SERVER_HELLO,
buf, buf_len ) );
end = *buf + *buf_len;
MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_is_supported_versions_ext_present(
ssl, *buf, end ) );
if( ret == 0 )
{
MBEDTLS_SSL_PROC_CHK_NEG(
ssl_tls13_is_downgrade_negotiation( ssl, *buf, end ) );
/* If the server is negotiating TLS 1.2 or below and:
* . we did not propose TLS 1.2 or
* . the server responded it is TLS 1.3 capable but negotiating a lower
* version of the protocol and thus we are under downgrade attack
* abort the handshake with an "illegal parameter" alert.
*/
if( ssl->handshake->min_tls_version > MBEDTLS_SSL_VERSION_TLS1_2 || ret )
{
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
}
ssl->keep_current_message = 1;
ssl->tls_version = MBEDTLS_SSL_VERSION_TLS1_2;
mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_SERVER_HELLO,
*buf, *buf_len );
if( mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
{
ret = ssl_tls13_reset_key_share( ssl );
if( ret != 0 )
return( ret );
}
return( SSL_SERVER_HELLO_COORDINATE_TLS1_2 );
}
ret = ssl_server_hello_is_hrr( ssl, *buf, end );
switch( ret )
{
case SSL_SERVER_HELLO_COORDINATE_HELLO:
MBEDTLS_SSL_DEBUG_MSG( 2, ( "received ServerHello message" ) );
break;
case SSL_SERVER_HELLO_COORDINATE_HRR:
MBEDTLS_SSL_DEBUG_MSG( 2, ( "received HelloRetryRequest message" ) );
/* If a client receives a second
* HelloRetryRequest in the same connection (i.e., where the ClientHello
* was itself in response to a HelloRetryRequest), it MUST abort the
* handshake with an "unexpected_message" alert.
*/
if( ssl->handshake->hello_retry_request_count > 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Multiple HRRs received" ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE,
MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
}
/*
* Clients must abort the handshake with an "illegal_parameter"
* alert if the HelloRetryRequest would not result in any change
* in the ClientHello.
* In a PSK only key exchange that what we expect.
*/
if( ! mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1,
( "Unexpected HRR in pure PSK key exchange." ) );
MBEDTLS_SSL_PEND_FATAL_ALERT(
MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER);
return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
}
ssl->handshake->hello_retry_request_count++;
break;
}
cleanup:
return( ret );
}
static int ssl_tls13_check_server_hello_session_id_echo( mbedtls_ssl_context *ssl,
const unsigned char **buf,
const unsigned char *end )
{
const unsigned char *p = *buf;
size_t legacy_session_id_echo_len;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 );
legacy_session_id_echo_len = *p++ ;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, legacy_session_id_echo_len );
/* legacy_session_id_echo */
if( ssl->session_negotiate->id_len != legacy_session_id_echo_len ||
memcmp( ssl->session_negotiate->id, p , legacy_session_id_echo_len ) != 0 )
{
MBEDTLS_SSL_DEBUG_BUF( 3, "Expected Session ID",
ssl->session_negotiate->id,
ssl->session_negotiate->id_len );
MBEDTLS_SSL_DEBUG_BUF( 3, "Received Session ID", p,
legacy_session_id_echo_len );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER);
return( MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
}
p += legacy_session_id_echo_len;
*buf = p;
MBEDTLS_SSL_DEBUG_BUF( 3, "Session ID", ssl->session_negotiate->id,
ssl->session_negotiate->id_len );
return( 0 );
}
/* Parse ServerHello message and configure context
*
* struct {
* ProtocolVersion legacy_version = 0x0303; // TLS 1.2
* Random random;
* opaque legacy_session_id_echo<0..32>;
* CipherSuite cipher_suite;
* uint8 legacy_compression_method = 0;
* Extension extensions<6..2^16-1>;
* } ServerHello;
*/
static int ssl_tls13_parse_server_hello( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end,
int is_hrr )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const unsigned char *p = buf;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
size_t extensions_len;
const unsigned char *extensions_end;
uint16_t cipher_suite;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
int fatal_alert = 0;
/*
* Check there is space for minimal fields
*
* - legacy_version ( 2 bytes)
* - random (MBEDTLS_SERVER_HELLO_RANDOM_LEN bytes)
* - legacy_session_id_echo ( 1 byte ), minimum size
* - cipher_suite ( 2 bytes)
* - legacy_compression_method ( 1 byte )
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN + 6 );
MBEDTLS_SSL_DEBUG_BUF( 4, "server hello", p, end - p );
MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, version", p, 2 );
/* ...
* ProtocolVersion legacy_version = 0x0303; // TLS 1.2
* ...
* with ProtocolVersion defined as:
* uint16 ProtocolVersion;
*/
if( mbedtls_ssl_read_version( p, ssl->conf->transport ) !=
MBEDTLS_SSL_VERSION_TLS1_2 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Unsupported version of TLS." ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION,
MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION );
ret = MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION;
goto cleanup;
}
p += 2;
/* ...
* Random random;
* ...
* with Random defined as:
* opaque Random[MBEDTLS_SERVER_HELLO_RANDOM_LEN];
*/
if( !is_hrr )
{
memcpy( &handshake->randbytes[MBEDTLS_CLIENT_HELLO_RANDOM_LEN], p,
MBEDTLS_SERVER_HELLO_RANDOM_LEN );
MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, random bytes",
p, MBEDTLS_SERVER_HELLO_RANDOM_LEN );
}
p += MBEDTLS_SERVER_HELLO_RANDOM_LEN;
/* ...
* opaque legacy_session_id_echo<0..32>;
* ...
*/
if( ssl_tls13_check_server_hello_session_id_echo( ssl, &p, end ) != 0 )
{
fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER;
goto cleanup;
}
/* ...
* CipherSuite cipher_suite;
* ...
* with CipherSuite defined as:
* uint8 CipherSuite[2];
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
cipher_suite = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( cipher_suite );
/*
* Check whether this ciphersuite is valid and offered.
*/
if( ( mbedtls_ssl_validate_ciphersuite( ssl, ciphersuite_info,
ssl->tls_version,
ssl->tls_version ) != 0 ) ||
!mbedtls_ssl_tls13_cipher_suite_is_offered( ssl, cipher_suite ) )
{
fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER;
}
/*
* If we received an HRR before and that the proposed selected
* ciphersuite in this server hello is not the same as the one
* proposed in the HRR, we abort the handshake and send an
* "illegal_parameter" alert.
*/
else if( ( !is_hrr ) && ( handshake->hello_retry_request_count > 0 ) &&
( cipher_suite != ssl->session_negotiate->ciphersuite ) )
{
fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER;
}
if( fatal_alert == MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid ciphersuite(%04x) parameter",
cipher_suite ) );
goto cleanup;
}
/* Configure ciphersuites */
mbedtls_ssl_optimize_checksum( ssl, ciphersuite_info );
handshake->ciphersuite_info = ciphersuite_info;
ssl->session_negotiate->ciphersuite = cipher_suite;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, chosen ciphersuite: ( %04x ) - %s",
cipher_suite, ciphersuite_info->name ) );
#if defined(MBEDTLS_HAVE_TIME)
ssl->session_negotiate->start = time( NULL );
#endif /* MBEDTLS_HAVE_TIME */
/* ...
* uint8 legacy_compression_method = 0;
* ...
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 );
if( p[0] != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad legacy compression method" ) );
fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER;
goto cleanup;
}
p++;
/* ...
* Extension extensions<6..2^16-1>;
* ...
* struct {
* ExtensionType extension_type; (2 bytes)
* opaque extension_data<0..2^16-1>;
* } Extension;
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
/* Check extensions do not go beyond the buffer of data. */
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len );
extensions_end = p + extensions_len;
MBEDTLS_SSL_DEBUG_BUF( 3, "server hello extensions", p, extensions_len );
while( p < extensions_end )
{
unsigned int extension_type;
size_t extension_data_len;
const unsigned char *extension_data_end;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, 4 );
extension_type = MBEDTLS_GET_UINT16_BE( p, 0 );
extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 );
p += 4;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len );
extension_data_end = p + extension_data_len;
switch( extension_type )
{
case MBEDTLS_TLS_EXT_COOKIE:
if( !is_hrr )
{
fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT;
goto cleanup;
}
ret = ssl_tls13_parse_cookie_ext( ssl,
p, extension_data_end );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1,
"ssl_tls13_parse_cookie_ext",
ret );
goto cleanup;
}
break;
case MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS:
ret = ssl_tls13_parse_supported_versions_ext( ssl,
p,
extension_data_end );
if( ret != 0 )
goto cleanup;
break;
case MBEDTLS_TLS_EXT_PRE_SHARED_KEY:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "found pre_shared_key extension." ) );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "pre_shared_key:Not supported yet" ) );
fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT;
goto cleanup;
case MBEDTLS_TLS_EXT_KEY_SHARE:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "found key_shares extension" ) );
if( ! mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
{
fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT;
goto cleanup;
}
if( is_hrr )
ret = ssl_tls13_parse_hrr_key_share_ext( ssl,
p, extension_data_end );
else
ret = ssl_tls13_parse_key_share_ext( ssl,
p, extension_data_end );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1,
"ssl_tls13_parse_key_share_ext",
ret );
goto cleanup;
}
break;
default:
MBEDTLS_SSL_DEBUG_MSG(
3,
( "unknown extension found: %u ( ignoring )",
extension_type ) );
fatal_alert = MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT;
goto cleanup;
}
p += extension_data_len;
}
cleanup:
if( fatal_alert == MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT )
{
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT,
MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION );
ret = MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION;
}
else if ( fatal_alert == MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER )
{
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER,
MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER );
ret = MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER;
}
return( ret );
}
static int ssl_tls13_postprocess_server_hello( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
/* Determine the key exchange mode:
* 1) If both the pre_shared_key and key_share extensions were received
* then the key exchange mode is PSK with EPHEMERAL.
* 2) If only the pre_shared_key extension was received then the key
* exchange mode is PSK-only.
* 3) If only the key_share extension was received then the key
* exchange mode is EPHEMERAL-only.
*/
switch( handshake->extensions_present &
( MBEDTLS_SSL_EXT_PRE_SHARED_KEY | MBEDTLS_SSL_EXT_KEY_SHARE ) )
{
/* Only the pre_shared_key extension was received */
case MBEDTLS_SSL_EXT_PRE_SHARED_KEY:
handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK;
break;
/* Only the key_share extension was received */
case MBEDTLS_SSL_EXT_KEY_SHARE:
handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL;
break;
/* Both the pre_shared_key and key_share extensions were received */
case ( MBEDTLS_SSL_EXT_PRE_SHARED_KEY | MBEDTLS_SSL_EXT_KEY_SHARE ):
handshake->tls13_kex_modes = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL;
break;
/* Neither pre_shared_key nor key_share extension was received */
default:
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Unknown key exchange." ) );
ret = MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
goto cleanup;
}
/* Start the TLS 1.3 key schedule: Set the PSK and derive early secret.
*
* TODO: We don't have to do this in case we offered 0-RTT and the
* server accepted it. In this case, we could skip generating
* the early secret. */
ret = mbedtls_ssl_tls13_key_schedule_stage_early( ssl );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_key_schedule_stage_early",
ret );
goto cleanup;
}
ret = mbedtls_ssl_tls13_compute_handshake_transform( ssl );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1,
"mbedtls_ssl_tls13_compute_handshake_transform",
ret );
goto cleanup;
}
mbedtls_ssl_set_inbound_transform( ssl, handshake->transform_handshake );
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Switch to handshake keys for inbound traffic" ) );
ssl->session_in = ssl->session_negotiate;
/*
* State machine update
*/
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS );
cleanup:
if( ret != 0 )
{
MBEDTLS_SSL_PEND_FATAL_ALERT(
MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE,
MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
}
return( ret );
}
static int ssl_tls13_postprocess_hrr( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
#if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE)
/* If not offering early data, the client sends a dummy CCS record
* immediately before its second flight. This may either be before
* its second ClientHello or before its encrypted handshake flight.
*/
mbedtls_ssl_handshake_set_state( ssl,
MBEDTLS_SSL_CLIENT_CCS_BEFORE_2ND_CLIENT_HELLO );
#else
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_HELLO );
#endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */
mbedtls_ssl_session_reset_msg_layer( ssl, 0 );
/*
* We are going to re-generate a shared secret corresponding to the group
* selected by the server, which is different from the group for which we
* generated a shared secret in the first client hello.
* Thus, reset the shared secret.
*/
ret = ssl_tls13_reset_key_share( ssl );
if( ret != 0 )
return( ret );
return( 0 );
}
/*
* Wait and parse ServerHello handshake message.
* Handler for MBEDTLS_SSL_SERVER_HELLO
*/
static int ssl_tls13_process_server_hello( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char *buf = NULL;
size_t buf_len = 0;
int is_hrr = 0;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> %s", __func__ ) );
/* Coordination step
* - Fetch record
* - Make sure it's either a ServerHello or a HRR.
* - Switch processing routine in case of HRR
*/
ssl->handshake->extensions_present = MBEDTLS_SSL_EXT_NONE;
ret = ssl_tls13_server_hello_coordinate( ssl, &buf, &buf_len );
if( ret < 0 )
goto cleanup;
else
is_hrr = ( ret == SSL_SERVER_HELLO_COORDINATE_HRR );
if( ret == SSL_SERVER_HELLO_COORDINATE_TLS1_2 )
{
ret = 0;
goto cleanup;
}
MBEDTLS_SSL_PROC_CHK( ssl_tls13_parse_server_hello( ssl, buf,
buf + buf_len,
is_hrr ) );
if( is_hrr )
MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_reset_transcript_for_hrr( ssl ) );
mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_SERVER_HELLO,
buf, buf_len );
if( is_hrr )
MBEDTLS_SSL_PROC_CHK( ssl_tls13_postprocess_hrr( ssl ) );
else
MBEDTLS_SSL_PROC_CHK( ssl_tls13_postprocess_server_hello( ssl ) );
cleanup:
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= %s ( %s )", __func__,
is_hrr?"HelloRetryRequest":"ServerHello" ) );
return( ret );
}
/*
*
* EncryptedExtensions message
*
* The EncryptedExtensions message contains any extensions which
* should be protected, i.e., any which are not needed to establish
* the cryptographic context.
*/
/*
* Overview
*/
/* Main entry point; orchestrates the other functions */
static int ssl_tls13_process_encrypted_extensions( mbedtls_ssl_context *ssl );
static int ssl_tls13_parse_encrypted_extensions( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end );
static int ssl_tls13_postprocess_encrypted_extensions( mbedtls_ssl_context *ssl );
/*
* Handler for MBEDTLS_SSL_ENCRYPTED_EXTENSIONS
*/
static int ssl_tls13_process_encrypted_extensions( mbedtls_ssl_context *ssl )
{
int ret;
unsigned char *buf;
size_t buf_len;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse encrypted extensions" ) );
MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl,
MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS,
&buf, &buf_len ) );
/* Process the message contents */
MBEDTLS_SSL_PROC_CHK(
ssl_tls13_parse_encrypted_extensions( ssl, buf, buf + buf_len ) );
mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS,
buf, buf_len );
MBEDTLS_SSL_PROC_CHK( ssl_tls13_postprocess_encrypted_extensions( ssl ) );
cleanup:
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse encrypted extensions" ) );
return( ret );
}
/* Parse EncryptedExtensions message
* struct {
* Extension extensions<0..2^16-1>;
* } EncryptedExtensions;
*/
static int ssl_tls13_parse_encrypted_extensions( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
int ret = 0;
size_t extensions_len;
const unsigned char *p = buf;
const unsigned char *extensions_end;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
MBEDTLS_SSL_DEBUG_BUF( 3, "encrypted extensions", p, extensions_len );
extensions_end = p + extensions_len;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len );
while( p < extensions_end )
{
unsigned int extension_type;
size_t extension_data_len;
/*
* struct {
* ExtensionType extension_type; (2 bytes)
* opaque extension_data<0..2^16-1>;
* } Extension;
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, 4 );
extension_type = MBEDTLS_GET_UINT16_BE( p, 0 );
extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 );
p += 4;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len );
/* The client MUST check EncryptedExtensions for the
* presence of any forbidden extensions and if any are found MUST abort
* the handshake with an "unsupported_extension" alert.
*/
switch( extension_type )
{
case MBEDTLS_TLS_EXT_SUPPORTED_GROUPS:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "found extensions supported groups" ) );
break;
#if defined(MBEDTLS_SSL_ALPN)
case MBEDTLS_TLS_EXT_ALPN:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "found alpn extension" ) );
if( ( ret = ssl_tls13_parse_alpn_ext( ssl, p, (size_t)extension_data_len ) ) != 0 )
{
return( ret );
}
break;
#endif /* MBEDTLS_SSL_ALPN */
default:
MBEDTLS_SSL_DEBUG_MSG(
3, ( "unsupported extension found: %u ", extension_type) );
MBEDTLS_SSL_PEND_FATAL_ALERT(
MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT,
MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION );
return ( MBEDTLS_ERR_SSL_UNSUPPORTED_EXTENSION );
}
p += extension_data_len;
}
/* Check that we consumed all the message. */
if( p != end )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "EncryptedExtension lengths misaligned" ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR,
MBEDTLS_ERR_SSL_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_DECODE_ERROR );
}
return( ret );
}
static int ssl_tls13_postprocess_encrypted_extensions( mbedtls_ssl_context *ssl )
{
#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
if( mbedtls_ssl_tls13_some_psk_enabled( ssl ) )
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED );
else
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CERTIFICATE_REQUEST );
#else
((void) ssl);
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED );
#endif
return( 0 );
}
#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
/*
*
* STATE HANDLING: CertificateRequest
*
*/
#define SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST 0
#define SSL_CERTIFICATE_REQUEST_SKIP 1
/* Coordination:
* Deals with the ambiguity of not knowing if a CertificateRequest
* will be sent. Returns a negative code on failure, or
* - SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST
* - SSL_CERTIFICATE_REQUEST_SKIP
* indicating if a Certificate Request is expected or not.
*/
static int ssl_tls13_certificate_request_coordinate( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if( mbedtls_ssl_tls13_some_psk_enabled( ssl ) )
{
MBEDTLS_SSL_DEBUG_MSG( 3, ( "<= skip parse certificate request" ) );
return( SSL_CERTIFICATE_REQUEST_SKIP );
}
if( ( ret = mbedtls_ssl_read_record( ssl, 0 ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
return( ret );
}
ssl->keep_current_message = 1;
if( ( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) &&
( ssl->in_msg[0] == MBEDTLS_SSL_HS_CERTIFICATE_REQUEST ) )
{
return( SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST );
}
return( SSL_CERTIFICATE_REQUEST_SKIP );
}
/*
* ssl_tls13_parse_certificate_request()
* Parse certificate request
* struct {
* opaque certificate_request_context<0..2^8-1>;
* Extension extensions<2..2^16-1>;
* } CertificateRequest;
*/
static int ssl_tls13_parse_certificate_request( mbedtls_ssl_context *ssl,
const unsigned char *buf,
const unsigned char *end )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const unsigned char *p = buf;
size_t certificate_request_context_len = 0;
size_t extensions_len = 0;
const unsigned char *extensions_end;
unsigned char sig_alg_ext_found = 0;
/* ...
* opaque certificate_request_context<0..2^8-1>
* ...
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 1 );
certificate_request_context_len = (size_t) p[0];
p += 1;
if( certificate_request_context_len > 0 )
{
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, certificate_request_context_len );
MBEDTLS_SSL_DEBUG_BUF( 3, "Certificate Request Context",
p, certificate_request_context_len );
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
handshake->certificate_request_context =
mbedtls_calloc( 1, certificate_request_context_len );
if( handshake->certificate_request_context == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return ( MBEDTLS_ERR_SSL_ALLOC_FAILED );
}
memcpy( handshake->certificate_request_context, p,
certificate_request_context_len );
p += certificate_request_context_len;
}
/* ...
* Extension extensions<2..2^16-1>;
* ...
*/
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
extensions_len = MBEDTLS_GET_UINT16_BE( p, 0 );
p += 2;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, extensions_len );
extensions_end = p + extensions_len;
while( p < extensions_end )
{
unsigned int extension_type;
size_t extension_data_len;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, 4 );
extension_type = MBEDTLS_GET_UINT16_BE( p, 0 );
extension_data_len = MBEDTLS_GET_UINT16_BE( p, 2 );
p += 4;
MBEDTLS_SSL_CHK_BUF_READ_PTR( p, extensions_end, extension_data_len );
switch( extension_type )
{
case MBEDTLS_TLS_EXT_SIG_ALG:
MBEDTLS_SSL_DEBUG_MSG( 3,
( "found signature algorithms extension" ) );
ret = mbedtls_ssl_parse_sig_alg_ext( ssl, p,
p + extension_data_len );
if( ret != 0 )
return( ret );
if( ! sig_alg_ext_found )
sig_alg_ext_found = 1;
else
{
MBEDTLS_SSL_DEBUG_MSG( 3,
( "Duplicate signature algorithms extensions found" ) );
goto decode_error;
}
break;
default:
MBEDTLS_SSL_DEBUG_MSG(
3,
( "unknown extension found: %u ( ignoring )",
extension_type ) );
break;
}
p += extension_data_len;
}
/* Check that we consumed all the message. */
if( p != end )
{
MBEDTLS_SSL_DEBUG_MSG( 1,
( "CertificateRequest misaligned" ) );
goto decode_error;
}
/* Check that we found signature algorithms extension */
if( ! sig_alg_ext_found )
{
MBEDTLS_SSL_DEBUG_MSG( 3,
( "no signature algorithms extension found" ) );
goto decode_error;
}
ssl->handshake->client_auth = 1;
return( 0 );
decode_error:
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR,
MBEDTLS_ERR_SSL_DECODE_ERROR );
return( MBEDTLS_ERR_SSL_DECODE_ERROR );
}
/*
* Handler for MBEDTLS_SSL_CERTIFICATE_REQUEST
*/
static int ssl_tls13_process_certificate_request( mbedtls_ssl_context *ssl )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate request" ) );
MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_certificate_request_coordinate( ssl ) );
if( ret == SSL_CERTIFICATE_REQUEST_EXPECT_REQUEST )
{
unsigned char *buf;
size_t buf_len;
MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_tls13_fetch_handshake_msg( ssl,
MBEDTLS_SSL_HS_CERTIFICATE_REQUEST,
&buf, &buf_len ) );
MBEDTLS_SSL_PROC_CHK( ssl_tls13_parse_certificate_request( ssl,
buf, buf + buf_len ) );
mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_CERTIFICATE_REQUEST,
buf, buf_len );
}
else if( ret == SSL_CERTIFICATE_REQUEST_SKIP )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate request" ) );
ret = 0;
}
else
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
goto cleanup;
}
MBEDTLS_SSL_DEBUG_MSG( 3, ( "got %s certificate request",
ssl->handshake->client_auth ? "a" : "no" ) );
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_CERTIFICATE );
cleanup:
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse certificate request" ) );
return( ret );
}
/*
* Handler for MBEDTLS_SSL_SERVER_CERTIFICATE
*/
static int ssl_tls13_process_server_certificate( mbedtls_ssl_context *ssl )
{
int ret;
ret = mbedtls_ssl_tls13_process_certificate( ssl );
if( ret != 0 )
return( ret );
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CERTIFICATE_VERIFY );
return( 0 );
}
/*
* Handler for MBEDTLS_SSL_CERTIFICATE_VERIFY
*/
static int ssl_tls13_process_certificate_verify( mbedtls_ssl_context *ssl )
{
int ret;
ret = mbedtls_ssl_tls13_process_certificate_verify( ssl );
if( ret != 0 )
return( ret );
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED );
return( 0 );
}
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
/*
* Handler for MBEDTLS_SSL_SERVER_FINISHED
*/
static int ssl_tls13_process_server_finished( mbedtls_ssl_context *ssl )
{
int ret;
ret = mbedtls_ssl_tls13_process_finished_message( ssl );
if( ret != 0 )
return( ret );
#if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE)
mbedtls_ssl_handshake_set_state(
ssl,
MBEDTLS_SSL_CLIENT_CCS_AFTER_SERVER_FINISHED );
#else
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE );
#endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */
return( 0 );
}
/*
* Handler for MBEDTLS_SSL_CLIENT_CERTIFICATE
*/
static int ssl_tls13_write_client_certificate( mbedtls_ssl_context *ssl )
{
int non_empty_certificate_msg = 0;
MBEDTLS_SSL_DEBUG_MSG( 1,
( "Switch to handshake traffic keys for outbound traffic" ) );
mbedtls_ssl_set_outbound_transform( ssl, ssl->handshake->transform_handshake );
#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
if( ssl->handshake->client_auth )
{
int ret = mbedtls_ssl_tls13_write_certificate( ssl );
if( ret != 0 )
return( ret );
if( mbedtls_ssl_own_cert( ssl ) != NULL )
non_empty_certificate_msg = 1;
}
else
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "No certificate message to send." ) );
}
#endif
if( non_empty_certificate_msg )
{
mbedtls_ssl_handshake_set_state( ssl,
MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY );
}
else
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_FINISHED );
return( 0 );
}
#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
/*
* Handler for MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY
*/
static int ssl_tls13_write_client_certificate_verify( mbedtls_ssl_context *ssl )
{
int ret = mbedtls_ssl_tls13_write_certificate_verify( ssl );
if( ret == 0 )
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_FINISHED );
return( ret );
}
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
/*
* Handler for MBEDTLS_SSL_CLIENT_FINISHED
*/
static int ssl_tls13_write_client_finished( mbedtls_ssl_context *ssl )
{
int ret;
ret = mbedtls_ssl_tls13_write_finished_message( ssl );
if( ret != 0 )
return( ret );
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_FLUSH_BUFFERS );
return( 0 );
}
/*
* Handler for MBEDTLS_SSL_FLUSH_BUFFERS
*/
static int ssl_tls13_flush_buffers( mbedtls_ssl_context *ssl )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "handshake: done" ) );
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_HANDSHAKE_WRAPUP );
return( 0 );
}
/*
* Handler for MBEDTLS_SSL_HANDSHAKE_WRAPUP
*/
static int ssl_tls13_handshake_wrapup( mbedtls_ssl_context *ssl )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Switch to application keys for inbound traffic" ) );
mbedtls_ssl_set_inbound_transform ( ssl, ssl->transform_application );
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Switch to application keys for outbound traffic" ) );
mbedtls_ssl_set_outbound_transform( ssl, ssl->transform_application );
mbedtls_ssl_tls13_handshake_wrapup( ssl );
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_HANDSHAKE_OVER );
return( 0 );
}
int mbedtls_ssl_tls13_handshake_client_step( mbedtls_ssl_context *ssl )
{
int ret = 0;
switch( ssl->state )
{
/*
* ssl->state is initialized as HELLO_REQUEST. It is the same
* as CLIENT_HELLO state.
*/
case MBEDTLS_SSL_HELLO_REQUEST:
case MBEDTLS_SSL_CLIENT_HELLO:
ret = mbedtls_ssl_write_client_hello( ssl );
break;
case MBEDTLS_SSL_SERVER_HELLO:
ret = ssl_tls13_process_server_hello( ssl );
break;
case MBEDTLS_SSL_ENCRYPTED_EXTENSIONS:
ret = ssl_tls13_process_encrypted_extensions( ssl );
break;
#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
case MBEDTLS_SSL_CERTIFICATE_REQUEST:
ret = ssl_tls13_process_certificate_request( ssl );
break;
case MBEDTLS_SSL_SERVER_CERTIFICATE:
ret = ssl_tls13_process_server_certificate( ssl );
break;
case MBEDTLS_SSL_CERTIFICATE_VERIFY:
ret = ssl_tls13_process_certificate_verify( ssl );
break;
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
case MBEDTLS_SSL_SERVER_FINISHED:
ret = ssl_tls13_process_server_finished( ssl );
break;
case MBEDTLS_SSL_CLIENT_CERTIFICATE:
ret = ssl_tls13_write_client_certificate( ssl );
break;
#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
case MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY:
ret = ssl_tls13_write_client_certificate_verify( ssl );
break;
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
case MBEDTLS_SSL_CLIENT_FINISHED:
ret = ssl_tls13_write_client_finished( ssl );
break;
case MBEDTLS_SSL_FLUSH_BUFFERS:
ret = ssl_tls13_flush_buffers( ssl );
break;
case MBEDTLS_SSL_HANDSHAKE_WRAPUP:
ret = ssl_tls13_handshake_wrapup( ssl );
break;
/*
* Injection of dummy-CCS's for middlebox compatibility
*/
#if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE)
case MBEDTLS_SSL_CLIENT_CCS_BEFORE_2ND_CLIENT_HELLO:
ret = mbedtls_ssl_tls13_write_change_cipher_spec( ssl );
if( ret == 0 )
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_HELLO );
break;
case MBEDTLS_SSL_CLIENT_CCS_AFTER_SERVER_FINISHED:
ret = mbedtls_ssl_tls13_write_change_cipher_spec( ssl );
if( ret == 0 )
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE );
break;
#endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */
default:
MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid state %d", ssl->state ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
return( ret );
}
#endif /* MBEDTLS_SSL_CLI_C && MBEDTLS_SSL_PROTO_TLS1_3 */
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