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Add helper function to check whether a CRT msg is expected

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This commit adds a helper function `ssl_parse_certificate_coordinate()`
which checks whether a `Certificate` message is expected from the peer.

The logic is the following:
- For ciphersuites which don't use server-side CRTs, no Certificate
  message is expected (neither for the server, nor the client).
- On the server, no client certificate is expected in the following cases:
  * The server server didn't request a Certificate, which is controlled
    by the `authmode` setting.
  * A RSA-PSK suite is used; this is the only suite using server CRTs
    but not allowing client-side authentication.
This commit is contained in:
Hanno Becker 2019-02-07 10:11:07 +00:00
parent 7177a88a36
commit 28f2fcd08d
1 changed files with 42 additions and 20 deletions
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62
library/ssl_tls.c
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@ -5944,11 +5944,49 @@ static int ssl_srv_check_client_no_crt_notification( mbedtls_ssl_context *ssl )
}
#endif /* MBEDTLS_SSL_SRV_C */
/* Check if a certificate message is expected.
* Return either
* - SSL_CERTIFICATE_EXPECTED, or
* - SSL_CERTIFICATE_SKIP
* indicating whether a Certificate message is expected or not.
*/
#define SSL_CERTIFICATE_EXPECTED 0
#define SSL_CERTIFICATE_SKIP 1
static int ssl_parse_certificate_coordinate( mbedtls_ssl_context *ssl,
int authmode )
{
const mbedtls_ssl_ciphersuite_t *ciphersuite_info =
ssl->transform_negotiate->ciphersuite_info;
if( !mbedtls_ssl_ciphersuite_uses_srv_cert( ciphersuite_info ) )
return( SSL_CERTIFICATE_SKIP );
#if defined(MBEDTLS_SSL_SRV_C)
if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER )
{
if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
return( SSL_CERTIFICATE_SKIP );
if( authmode == MBEDTLS_SSL_VERIFY_NONE )
{
/* NOTE: Is it intentional that we set verify_result
* to SKIP_VERIFY on server-side only? */
ssl->session_negotiate->verify_result =
MBEDTLS_X509_BADCERT_SKIP_VERIFY;
return( SSL_CERTIFICATE_SKIP );
}
}
#endif /* MBEDTLS_SSL_SRV_C */
return( SSL_CERTIFICATE_EXPECTED );
}
int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
{
int ret = 0;
const mbedtls_ssl_ciphersuite_t * const ciphersuite_info =
ssl->transform_negotiate->ciphersuite_info;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info =
ssl->transform_negotiate->ciphersuite_info;
int crt_expected;
#if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
const int authmode = ssl->handshake->sni_authmode != MBEDTLS_SSL_VERIFY_UNSET
? ssl->handshake->sni_authmode
@ -5960,29 +5998,13 @@ int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate" ) );
if( !mbedtls_ssl_ciphersuite_uses_srv_cert( ciphersuite_info ) )
crt_expected = ssl_parse_certificate_coordinate( ssl, authmode );
if( crt_expected == SSL_CERTIFICATE_SKIP )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
goto exit;
}
#if defined(MBEDTLS_SSL_SRV_C)
if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
goto exit;
}
if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
authmode == MBEDTLS_SSL_VERIFY_NONE )
{
ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_SKIP_VERIFY;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
goto exit;
}
#endif
#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
if( ssl->handshake->ecrs_enabled &&
ssl->handshake->ecrs_state == ssl_ecrs_crt_verify )