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Add logic to switch to TLS 1.2

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Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron
2022-02-10 16:45:15 +01:00
parent e1d3f06399
commit 9f0fba374c
2 changed files with 130 additions and 21 deletions
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121
library/ssl_tls13_client.c
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@ -710,6 +710,75 @@ int mbedtls_ssl_tls13_write_client_hello_exts( mbedtls_ssl_context *ssl,
/*
* Functions for parsing and processing Server Hello
*/
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 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
* - SSL_SERVER_HELLO_COORDINATE_HELLO or
* - SSL_SERVER_HELLO_COORDINATE_HRR
@ -755,8 +824,10 @@ static int ssl_server_hello_is_hrr( mbedtls_ssl_context *ssl,
/* Fetch and preprocess
* Returns a negative value on failure, and otherwise
* - SSL_SERVER_HELLO_COORDINATE_HELLO or
* - SSL_SERVER_HELLO_COORDINATE_HRR
* - 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 )
@ -767,6 +838,36 @@ static int ssl_tls13_server_hello_coordinate( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_HS_SERVER_HELLO,
buf, buf_len ) );
MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_is_supported_versions_ext_present(
ssl, *buf, *buf + *buf_len ) );
if( ret == 0 )
{
/* If the supported versions extension is not present but we were
* expecting it, abort the handshake. Otherwise, switch to TLS 1.2
* handshake.
*/
if( ssl->handshake->min_minor_ver > MBEDTLS_SSL_MINOR_VERSION_3 )
{
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->minor_ver = MBEDTLS_SSL_MINOR_VERSION_3;
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, *buf + *buf_len );
switch( ret )
{
@ -888,7 +989,6 @@ static int ssl_tls13_parse_server_hello( mbedtls_ssl_context *ssl,
const unsigned char *extensions_end;
uint16_t cipher_suite;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
int supported_versions_ext_found = 0;
int fatal_alert = 0;
/*
@ -1068,10 +1168,6 @@ static int ssl_tls13_parse_server_hello( mbedtls_ssl_context *ssl,
break;
case MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS:
supported_versions_ext_found = 1;
MBEDTLS_SSL_DEBUG_MSG( 3,
( "found supported_versions extension" ) );
ret = ssl_tls13_parse_supported_versions_ext( ssl,
p,
extension_data_end );
@ -1122,13 +1218,6 @@ static int ssl_tls13_parse_server_hello( mbedtls_ssl_context *ssl,
p += extension_data_len;
}
if( !supported_versions_ext_found )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "supported_versions not found" ) );
fatal_alert = MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER;
goto cleanup;
}
cleanup:
if( fatal_alert == MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_EXT )
@ -1317,6 +1406,12 @@ static int ssl_tls13_process_server_hello( mbedtls_ssl_context *ssl )
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 ) );