If we receive an "update_requested" KeyUpdate then respond with a KeyUpdate

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2609)

ssl/statem/statem_clnt.c

@@ -439,6 +439,12 @@ static WRITE_TRAN ossl_statem_client13_write_transition(SSL *s)
         return WRITE_TRAN_CONTINUE;
 
     case TLS_ST_CR_KEY_UPDATE:
+        if (s->key_update != SSL_KEY_UPDATE_NONE) {
+            st->hand_state = TLS_ST_CW_KEY_UPDATE;
+            return WRITE_TRAN_CONTINUE;
+        }
+        /* Fall through */
+
     case TLS_ST_CW_KEY_UPDATE:
     case TLS_ST_CR_SESSION_TICKET:
     case TLS_ST_CW_FINISHED:

ssl/statem/statem_lib.c

@@ -525,6 +525,14 @@ MSG_PROCESS_RETURN tls_process_key_update(SSL *s, PACKET *pkt)
         return MSG_PROCESS_ERROR;
     }
 
+    /*
+     * If we get a request for us to update our sending keys too then, we need
+     * to additionally send a KeyUpdate message. However that message should
+     * not also request an update (otherwise we get into an infinite loop).
+     */
+    if (updatetype == SSL_KEY_UPDATE_REQUESTED)
+        s->key_update = SSL_KEY_UPDATE_NOT_REQUESTED;
+
     return MSG_PROCESS_FINISHED_READING;
 }
 

ssl/statem/statem_srvr.c

@@ -470,6 +470,12 @@ static WRITE_TRAN ossl_statem_server13_write_transition(SSL *s)
         return WRITE_TRAN_CONTINUE;
 
     case TLS_ST_SR_KEY_UPDATE:
+        if (s->key_update != SSL_KEY_UPDATE_NONE) {
+            st->hand_state = TLS_ST_SW_KEY_UPDATE;
+            return WRITE_TRAN_CONTINUE;
+        }
+        /* Fall through */
+
     case TLS_ST_SW_KEY_UPDATE:
     case TLS_ST_SW_SESSION_TICKET:
         st->hand_state = TLS_ST_OK;