Added BR_OPT_NO_RENEGOTIATION flag to forbid TLS renegociation (esp8266#6165)

Author: s-hadinger

libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.cpp

@@ -827,6 +827,7 @@ extern "C" {
     uint16_t suites[cipher_cnt];
     memcpy_P(suites, cipher_list, cipher_cnt * sizeof(cipher_list[0]));
     br_ssl_client_zero(cc);
+    br_ssl_engine_add_flags(&cc->eng, BR_OPT_NO_RENEGOTIATION);  // forbid SSL renegociation, as we free the Private Key after handshake
     br_ssl_engine_set_versions(&cc->eng, BR_TLS10, BR_TLS12);
     br_ssl_engine_set_suites(&cc->eng, suites, (sizeof suites) / (sizeof suites[0]));
     br_ssl_client_set_default_rsapub(cc);