$direction = CLIENT_TO_SERVER;
$proxy->filter(\&modify_key_shares_filter);
$proxy->start() or plan skip_all => "Unable to start up Proxy for tests";
-plan tests => 17;
+plan tests => 19;
#TODO(TLS1.3): Actually this should succeed after a HelloRetryRequest - but
#we've not implemented that yet, so for now we look for a fail
ok(TLSProxy::Message->fail(), "Empty key_shares");
$proxy->start();
ok(TLSProxy::Message->fail(), "key_share trailing data in ServerHello");
+#Test 18: key_share should not be sent if the client is not capable of
+# negotiating TLSv1.3
+$proxy->clear();
+$proxy->filter(undef);
+$proxy->clientflags("-no_tls1_3");
+$proxy->start();
+my $clienthello = ${$proxy->message_list}[0];
+ok(TLSProxy::Message->success()
+ && !defined ${$clienthello->extension_data}{TLSProxy::Message::EXT_KEY_SHARE},
+ "No key_share for TLS<=1.2 client");
+$proxy->filter(\&modify_key_shares_filter);
+
+#Test 19: A server not capable of negotiating TLSv1.3 should not attempt to
+# process a key_share
+$proxy->clear();
+$direction = CLIENT_TO_SERVER;
+$testtype = NO_ACCEPTABLE_KEY_SHARES;
+$proxy->serverflags("-no_tls1_3");
+$proxy->start();
+ok(TLSProxy::Message->success(), "Ignore key_share for TLS<=1.2 server");
sub modify_key_shares_filter
{