Ensure SSL3_FLAGS_CCS_OK (or d1->change_cipher_spec_ok for DTLS) is reset

once the ChangeCipherSpec message is received. Previously, the server would
set the flag once at SSL3_ST_SR_CERT_VRFY and again at SSL3_ST_SR_FINISHED.
This would allow a second CCS to arrive and would corrupt the server state.

(Because the first CCS would latch the correct keys and subsequent CCS
messages would have to be encrypted, a MitM attacker cannot exploit this,
though.)

Thanks to Joeri de Ruiter for reporting this issue.

Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit e94a6c0ede)

ssl/t1_lib.c

@@ -2560,7 +2560,7 @@ static int ssl_scan_serverhello_tlsext(SSL *s, unsigned char **p, unsigned char
 #ifndef OPENSSL_NO_NEXTPROTONEG
 	s->s3->next_proto_neg_seen = 0;
 #endif
-        s->tlsext_ticket_expected = 0;
+	s->tlsext_ticket_expected = 0;
 
 	if (s->s3->alpn_selected)
 		{