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ssl_write_server_key_exchange refactor: create ssl_prepare_server_key_exchange

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This is in the process of splitting ssl_write_server_key_exchange
into several functions.
This commit is contained in:
Gilles Peskine 2018-01-06 01:46:17 +01:00
parent 3ce9b900d2
commit 184a3faa8a
1 changed files with 51 additions and 36 deletions
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87
library/ssl_srv.c
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@ -2826,9 +2826,8 @@ static int ssl_get_ecdh_params_from_cert( mbedtls_ssl_context *ssl )
#endif /* MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED) ||
MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED */
static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
static int ssl_prepare_server_key_exchange( mbedtls_ssl_context *ssl )
{
int ret;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info =
ssl->transform_negotiate->ciphersuite_info;
@ -2839,6 +2838,7 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
unsigned char *dig_signed = NULL;
#endif /* MBEDTLS_KEY_EXCHANGE__WITH_SERVER_SIGNATURE__ENABLED */
#endif /* MBEDTLS_KEY_EXCHANGE__SOME_PFS__ENABLED */
(void) ciphersuite_info; /* unused in some configurations */
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write server key exchange" ) );
@ -2855,34 +2855,7 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
/*
*
* Part 1: Extract static ECDH parameters and abort
* if ServerKeyExchange not needed.
*
*/
/* For suites involving ECDH, extract DH parameters
* from certificate at this point. */
#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 /* MBEDTLS_KEY_EXCHANGE__NON_PFS__ENABLED */
/*
*
* Part 2: Provide key exchange parameters for chosen ciphersuite.
* Part 1: Provide key exchange parameters for chosen ciphersuite.
*
*/
@ -2892,6 +2865,7 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
{
int ret;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
ret = mbedtls_ecjpake_write_round_two( &ssl->handshake->ecjpake_ctx,
@ -2928,6 +2902,8 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
#if defined(MBEDTLS_KEY_EXCHANGE__SOME__DHE_ENABLED)
if( mbedtls_ssl_ciphersuite_uses_dhe( ciphersuite_info ) )
{
int ret;
if( ssl->conf->dhm_P.p == NULL || ssl->conf->dhm_G.p == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "no DH parameters set" ) );
@ -2987,6 +2963,7 @@ static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
*/
const mbedtls_ecp_curve_info **curve = NULL;
const mbedtls_ecp_group_id *gid;
int ret;
/* Match our preference list against the offered curves */
for( gid = ssl->conf->curve_list; *gid != MBEDTLS_ECP_DP_NONE; gid++ )
@ -3031,7 +3008,7 @@ curve_matching_done:
/*
*
* Part 3: For key exchanges involving the server signing the
* Part 2: For key exchanges involving the server signing the
* exchange parameters, compute and add the signature here.
*
*/
@ -3042,9 +3019,10 @@ curve_matching_done:
size_t signature_len = 0;
unsigned int hashlen = 0;
unsigned char hash[MBEDTLS_MD_MAX_SIZE];
int ret;
/*
* 3.1: Choose hash algorithm:
* 2.1: Choose hash algorithm:
* A: For TLS 1.2, obey signature-hash-algorithm extension
* to choose appropriate hash.
* B: For SSL3, TLS1.0, TLS1.1 and ECDHE_ECDSA, use SHA1
@ -3091,7 +3069,7 @@ curve_matching_done:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "pick hash algorithm %d for signing", md_alg ) );
/*
* 3.2: Compute the hash to be signed
* 2.2: Compute the hash to be signed
*/
#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
defined(MBEDTLS_SSL_PROTO_TLS1_1)
@ -3176,7 +3154,7 @@ curve_matching_done:
MBEDTLS_SSL_DEBUG_BUF( 3, "parameters hash", hash, hashlen );
/*
* 3.3: Compute and add the signature
* 2.3: Compute and add the signature
*/
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 )
@ -3258,7 +3236,9 @@ curve_matching_done:
return( ret );
}
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
have_signature:
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
*(p++) = (unsigned char)( signature_len >> 8 );
*(p++) = (unsigned char)( signature_len );
@ -3268,9 +3248,44 @@ curve_matching_done:
}
#endif /* MBEDTLS_KEY_EXCHANGE__WITH_SERVER_SIGNATURE__ENABLED */
/* Done with actual work; add header and send. */
ssl->out_msglen = p - ssl->out_msg;
return( 0 );
}
static int ssl_write_server_key_exchange( mbedtls_ssl_context *ssl )
{
int ret;
/* Extract static ECDH parameters and abort if ServerKeyExchange
* is not needed. */
#if defined(MBEDTLS_KEY_EXCHANGE__SOME_NON_PFS__ENABLED)
const mbedtls_ssl_ciphersuite_t *ciphersuite_info =
ssl->transform_negotiate->ciphersuite_info;
if( mbedtls_ssl_ciphersuite_no_pfs( ciphersuite_info ) )
{
/* For suites involving ECDH, extract DH parameters
* from certificate at this point. */
#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. */
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip write server key exchange" ) );
ssl->state++;
return( 0 );
}
#endif /* MBEDTLS_KEY_EXCHANGE__NON_PFS__ENABLED */
/* ServerKeyExchange is needed. Prepare the message. */
ret = ssl_prepare_server_key_exchange( ssl );
if( ret != 0 )
return( ret );
/* Add header and send. */
ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
ssl->out_msg[0] = MBEDTLS_SSL_HS_SERVER_KEY_EXCHANGE;