keytool -genkey -keystore client.keystore -validity 3650
    -keyalg RSA -keysize 4096 -storetype pkcs12 -alias myClient

keytool -exportcert -keystore client.keystore -alias myClient
    -storetype pkcs12 -file myClient.crt

keytool -import -file myClient.crt
     -keystore /etc/pki/wildfly/client.truststore

<security-realm name="UndertowRealm">
  <server-identities>
    <ssl>
      <keystore path="/etc/pki/wildfly/server.keystore" keystore-password="123456" alias="server" key-password="123456"/>
    </ssl>
  </server-identities>
  <authentication>
    <truststore path="/etc/pki/wildfly/client.truststore" keystore-password="123456"/>
    <local default-user="$local" skip-group-loading="true"/>
    <properties path="mgmt-users.properties" relative-to="jboss.server.config.dir"/>
  </authentication>
</security-realm>
...
<subsystem xmlns="urn:jboss:domain:undertow:2.0">
  <server name="default-server">
    <https-listener name="https" socket-binding="https" security-realm="UndertowRealm" verify-client="REQUIRED"/>
     ...
   </server>
 </subsystem>

keytool -v -importkeystore -srckeystore client.keytool
    -srcalias myClient -destkeystore myClient.key.tmp.pem
    -deststoretype PKCS12 -destkeypass 123456

openssl pkcs12 -in myClient.key.tmp.pem -nocerts
    -nodes > myClient.key.pem

2016-10-31 09:50:55,102 DEBUG [io.undertow.request.io] (default I/O-1) Error reading request: javax.net.ssl.SSLException: Received fatal alert: unknown_ca
    at sun.security.ssl.Alerts.getSSLException(Alerts.java:208)
    at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1666)
    at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1634)
    at sun.security.ssl.SSLEngineImpl.recvAlert(SSLEngineImpl.java:1800)
    at sun.security.ssl.SSLEngineImpl.readRecord(SSLEngineImpl.java:1083)
    at sun.security.ssl.SSLEngineImpl.readNetRecord(SSLEngineImpl.java:907)
    at sun.security.ssl.SSLEngineImpl.unwrap(SSLEngineImpl.java:781)
    at javax.net.ssl.SSLEngine.unwrap(SSLEngine.java:624)
    at org.xnio.ssl.JsseSslConduitEngine.engineUnwrap(JsseSslConduitEngine.java:688)
    at org.xnio.ssl.JsseSslConduitEngine.unwrap(JsseSslConduitEngine.java:620)
    at org.xnio.ssl.JsseSslConduitEngine.unwrap(JsseSslConduitEngine.java:574)
    at org.xnio.ssl.JsseSslStreamSourceConduit.read(JsseSslStreamSourceConduit.java:89)
    at org.xnio.conduits.ConduitStreamSourceChannel.read(ConduitStreamSourceChannel.java:127)
    at io.undertow.server.protocol.http.HttpReadListener.handleEventWithNoRunningRequest(HttpReadListener.java:150)
    at io.undertow.server.protocol.http.HttpReadListener.handleEvent(HttpReadListener.java:128)
    at io.undertow.server.protocol.http.HttpReadListener.handleEvent(HttpReadListener.java:56)
    at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92)
    at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66)
    at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:88)
    at org.xnio.nio.WorkerThread.run(WorkerThread.java:539)