title: spring+saml Validation of protocol message signature failed
body: <p>please help. i have a sp, and a public key for remote idp.
  I uploaded sample of spring saml, and changed it, public key was added to jks file(used keytool, command -list showed that cer was imported) with alias and it was pointed in extended metadata of idp with signingKey. but in the end validation was failed.</p>
  
  <pre><code>org.springframework.security.authentication.AuthenticationServiceException: Incoming SAML message is invalid
  at org.springframework.security.saml.SAMLProcessingFilter.attemptAuthentication(SAMLProcessingFilter.java:100)
  at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:195)
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
  at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
  at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:166)
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
  at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
  at org.springframework.security.saml.metadata.MetadataGeneratorFilter.doFilter(MetadataGeneratorFilter.java:87)
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
  at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
  at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
  at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
  at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
  at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:154)
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368)
  at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877)
  at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671)
  at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930)
  at java.lang.Thread.run(Thread.java:745)
  </code></pre>
  
  <p>Caused by: org.opensaml.ws.security.SecurityPolicyException: Validation of protocol message signature failed</p>