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DTLS: treat bad MAC on Finished as an error

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This is not required nor recommended by the protocol, and it's a layering
violation, but it's a know flaw in the protocol that you can't detect a PSK
auth error in any other way, so it is probably the right thing to do.

closes #227
This commit is contained in:
Manuel Pégourié-Gonnard
2015-08-04 12:08:35 +02:00
parent 7381ff0046
commit 0a8857435c
2 changed files with 24 additions and 0 deletions
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17
library/ssl_tls.c
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@ -3573,6 +3573,23 @@ read_record_header:
if( ret == MBEDTLS_ERR_SSL_INVALID_RECORD ||
ret == MBEDTLS_ERR_SSL_INVALID_MAC )
{
/* Except when waiting for Finished as a bad mac here
* probably means something went wrong in the handshake
* (eg wrong psk used, mitm downgrade attempt, etc.) */
if( ssl->state == MBEDTLS_SSL_CLIENT_FINISHED ||
ssl->state == MBEDTLS_SSL_SERVER_FINISHED )
{
#if defined(MBEDTLS_SSL_ALL_ALERT_MESSAGES)
if( ret == MBEDTLS_ERR_SSL_INVALID_MAC )
{
mbedtls_ssl_send_alert_message( ssl,
MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_BAD_RECORD_MAC );
}
#endif
return( ret );
}
#if defined(MBEDTLS_SSL_DTLS_BADMAC_LIMIT)
if( ssl->conf->badmac_limit != 0 &&
++ssl->badmac_seen >= ssl->conf->badmac_limit )