Test KeyUpdate rejection

For now, just test that we don't generate any, since we don't really
expose the mechanics for encrypting one and the QUIC API is not
integrated into the TLSProxy setup.

test/sslapitest.c

@@ -6778,6 +6778,17 @@ static int test_quic_api(void)
             || !TEST_true(SSL_process_quic_post_handshake(clientssl)))
         goto end;
 
+    /* Dummy handshake call should succeed */
+    if (!TEST_true(SSL_do_handshake(clientssl)))
+        goto end;
+    /* Test that we (correctly) fail to send KeyUpdate */
+    if (!TEST_true(SSL_key_update(clientssl, SSL_KEY_UPDATE_NOT_REQUESTED))
+            || !TEST_int_le(SSL_do_handshake(clientssl), 0))
+        goto end;
+    if (!TEST_true(SSL_key_update(serverssl, SSL_KEY_UPDATE_NOT_REQUESTED))
+            || !TEST_int_le(SSL_do_handshake(serverssl), 0))
+        goto end;
+
     testresult = 1;
 
 end: