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Introduce macros and functions to characterize certain ciphersuites.

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The routine `mbedtls_ssl_write_server_key_exchange` heavily depends on
what kind of cipher suite is active: some don't need a
ServerKeyExchange at all, some need (EC)DH parameters but no server
signature, some require both. Each time we want to restrict a certain
piece of code to some class of ciphersuites, it is guarded by a
lengthy concatentation of configuration checks determining whether at
least one of the relevant cipher suites is enabled in the config; on
the code level, it is guarded by the check whether one of these
cipher suites is the active one.

To ease readability of the code, this commit introduces several helper
macros and helper functions that can be used to determine whether a
certain class of ciphersuites (a) is active in the config, and
(b) contains the currently present ciphersuite.
This commit is contained in:
Hanno Becker 2017-04-28 17:08:27 +01:00
parent 63a48d10e9
commit b3e6872c93
5 changed files with 245 additions and 119 deletions
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83
library/ssl_srv.c
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@ -2563,52 +2563,45 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
const mbedtls_ssl_ciphersuite_t *ciphersuite_info =
ssl->transform_negotiate->ciphersuite_info;
#if defined(MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED)
#if defined(MBEDTLS_KEY_EXCHANGE__SOME_PFS__ENABLED)
unsigned char *p = ssl->out_msg + 4;
unsigned char *dig_signed = p;
size_t dig_signed_len = 0, len;
((void) dig_signed);
((void) dig_signed_len);
#endif
((void) len);
#endif /* MBEDTLS_KEY_EXCHANGE__SOME_PFS__ENABLED) */
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write server key exchange" ) );
#if defined(MBEDTLS_KEY_EXCHANGE_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip write server key exchange" ) );
ssl->state++;
return( 0 );
}
#endif
#if defined(MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDH_RSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA )
/* For key exchanges involving ECDH, extract DH parameters from certificate here. */
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__ECDH_ENABLED)
if( mbedtls_ssl_ciphersuite_uses_ecdh( ciphersuite_info ) )
{
ssl_get_ecdh_params_from_cert( ssl );
}
#endif /* MBEDTLS_KEY_EXCHANGE__SOME__ECDH_ENABLED */
/* Key exchanges not involving ephemeral keys don't use ServerKeyExchange, so end here. */
#if defined(MBEDTLS_KEY_EXCHANGE__SOME_NON_PFS__ENABLED)
if( mbedtls_ssl_ciphersuite_no_pfs( ciphersuite_info ) )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip write server key exchange" ) );
ssl->state++;
return( 0 );
}
#endif
#endif /* MBEDTLS_KEY_EXCHANGE__NON_PFS__ENABLED */
#if defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED) || \
/*
* For (EC)DHE key exchanges with PSK, parameters are prefixed by support
* identity hint (RFC 4279, Sec. 3). Until someone needs this feature,
* we use empty support identity hints here.
**/
#if defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK )
{
/* TODO: Support identity hints */
*(p++) = 0x00;
*(p++) = 0x00;
@ -2617,10 +2610,11 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
#endif /* MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED ||
MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED */
#if defined(MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_RSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK )
/*
* For DHE key exchanges, add the DH parameters here.
*/
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__DHE_ENABLED)
if( mbedtls_ssl_ciphersuite_uses_dhe( ciphersuite_info ) )
{
if( ssl->conf->dhm_P.p == NULL || ssl->conf->dhm_G.p == NULL )
{
@ -2663,13 +2657,13 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MPI( 3, "DHM: G ", &ssl->handshake->dhm_ctx.G );
MBEDTLS_SSL_DEBUG_MPI( 3, "DHM: GX", &ssl->handshake->dhm_ctx.GX );
}
#endif /* MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED ||
MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED */
#endif /* MBEDTLS_KEY_EXCHANGE__SOME__DHE_ENABLED */
/*
* For ECDHE key exchanges, add the ECDH parameters here.
*/
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__ECDHE_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_RSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK )
if( mbedtls_ssl_ciphersuite_uses_ecdhe( ciphersuite_info ) )
{
/*
* Ephemeral ECDH parameters:
@ -2722,12 +2716,12 @@ curve_matching_done:
}
#endif /* MBEDTLS_KEY_EXCHANGE__SOME__ECDHE_ENABLED */
#if defined(MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED) || \
defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_RSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_RSA ||
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA )
/*
* For key exchanges involving the server signing the (EC)DH parameters,
* compute and add the signature here.
*/
#if defined(MBEDTLS_KEY_EXCHANGE__WITH_SERVER_SIGNATURE__ENABLED)
if( mbedtls_ssl_ciphersuite_uses_server_signature( ciphersuite_info ) )
{
size_t signature_len = 0;
unsigned int hashlen = 0;
@ -2758,7 +2752,8 @@ curve_matching_done:
md_alg = MBEDTLS_MD_SHA1;
}
else
#endif
#endif /* MBEDTLS_SSL_PROTO_SSL3 || MBEDTLS_SSL_PROTO_TLS1 || \
MBEDTLS_SSL_PROTO_TLS1_1 */
{
md_alg = MBEDTLS_MD_NONE;
}
@ -2884,9 +2879,7 @@ curve_matching_done:
n += signature_len;
}
#endif /* MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED) ||
MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED ||
MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED */
#endif /* MBEDTLS_KEY_EXCHANGE__WITH_SERVER_SIGNATURE__ENABLED */
ssl->out_msglen = 4 + n;
ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;