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Restructure SrvKeyExchange: Move msg skipping for PSK and RSA-PSK

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In the PSK and RSA-PSK ciphersuites, the ServerKeyExchange message
MAY be skipped. This commit moves the code-path peeking at the
incoming message to decide whether it's probably a ServerKeyExchange
to the new coordination function ssl_server_key_exchange_coordinate().
This commit is contained in:
Hanno Becker 2018-05-21 09:30:17 +01:00
parent eb76c20496
commit 8b7b879143
1 changed files with 68 additions and 34 deletions
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102
library/ssl_cli.c
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@ -2730,6 +2730,13 @@ static int ssl_server_key_exchange_coordinate( mbedtls_ssl_context *ssl )
mbedtls_ssl_ciphersuite_handle_t ciphersuite_info = mbedtls_ssl_ciphersuite_handle_t ciphersuite_info =
mbedtls_ssl_handshake_get_ciphersuite( ssl->handshake ); mbedtls_ssl_handshake_get_ciphersuite( ssl->handshake );
/* The ServerKeyExchange message is not used for
* - RSA or
* - static ECDH
* ciphersuites.
* It MAY be used in PSK or RSA-PSK.
*/
#if defined(MBEDTLS_KEY_EXCHANGE_RSA_ENABLED) #if defined(MBEDTLS_KEY_EXCHANGE_RSA_ENABLED)
if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) == if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) ==
MBEDTLS_KEY_EXCHANGE_RSA ) MBEDTLS_KEY_EXCHANGE_RSA )
@ -2750,6 +2757,33 @@ static int ssl_server_key_exchange_coordinate( mbedtls_ssl_context *ssl )
#endif /* MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED || #endif /* MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED ||
MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED */ MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED */
/*
* ServerKeyExchange may be skipped with PSK and RSA-PSK when the server
* doesn't use a psk_identity_hint. Peek at next message to decide whether
* the ServerKeyExchange is being skipped or not.
*/
if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
== MBEDTLS_KEY_EXCHANGE_PSK ||
mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
== MBEDTLS_KEY_EXCHANGE_RSA_PSK )
{
if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 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_SERVER_KEY_EXCHANGE )
{
/* Current message is probably either
* CertificateRequest or ServerHelloDone */
return( SSL_SRV_KEY_EXCHANGE_SKIP );
}
}
return( SSL_SRV_KEY_EXCHANGE_EXPECTED ); return( SSL_SRV_KEY_EXCHANGE_EXPECTED );
} }
@ -2825,44 +2859,44 @@ static int ssl_parse_server_key_exchange( mbedtls_ssl_context *ssl )
} }
#endif #endif
if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 ) /* if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 ) */
{ /* { */
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret ); /* MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret ); */
return( ret ); /* return( ret ); */
} /* } */
if( ssl->in_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE ) /* if( ssl->in_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE ) */
{ /* { */
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad server key exchange message" ) ); /* MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad server key exchange message" ) ); */
mbedtls_ssl_pend_fatal_alert( ssl, /* mbedtls_ssl_pend_fatal_alert( ssl, */
MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE ); /* MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE ); */
return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); /* return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); */
} /* } */
/* /* /\* */
* ServerKeyExchange may be skipped with PSK and RSA-PSK when the server /* * ServerKeyExchange may be skipped with PSK and RSA-PSK when the server */
* doesn't use a psk_identity_hint /* * doesn't use a psk_identity_hint */
*/ /* *\/ */
if( ssl->in_msg[0] != MBEDTLS_SSL_HS_SERVER_KEY_EXCHANGE ) /* if( ssl->in_msg[0] != MBEDTLS_SSL_HS_SERVER_KEY_EXCHANGE ) */
{ /* { */
if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) /* if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) */
== MBEDTLS_KEY_EXCHANGE_PSK || /* == MBEDTLS_KEY_EXCHANGE_PSK || */
mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) /* mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) */
== MBEDTLS_KEY_EXCHANGE_RSA_PSK ) /* == MBEDTLS_KEY_EXCHANGE_RSA_PSK ) */
{ /* { */
/* Current message is probably either /* /\* Current message is probably either */
* CertificateRequest or ServerHelloDone */ /* * CertificateRequest or ServerHelloDone *\/ */
ssl->keep_current_message = 1; /* ssl->keep_current_message = 1; */
goto exit; /* goto exit; */
} /* } */
MBEDTLS_SSL_DEBUG_MSG( 1, ( "server key exchange message must " /* MBEDTLS_SSL_DEBUG_MSG( 1, ( "server key exchange message must " */
"not be skipped" ) ); /* "not be skipped" ) ); */
mbedtls_ssl_pend_fatal_alert( ssl, /* mbedtls_ssl_pend_fatal_alert( ssl, */
MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE ); /* MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE ); */
return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); /* return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); */
} /* } */
#if defined(MBEDTLS_SSL__ECP_RESTARTABLE) #if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
if( ssl->handshake->ecrs_enabled ) if( ssl->handshake->ecrs_enabled )