wso2 identity server SAML2 bearer token request with Resident Identity Provider - saml-2.0

Question

I want to use the resident identity provider on wso2is as my Identity provider.
It works well for the SAML 2 simple functionnalities.
When i want to convert a saml assertion to a saml2 bearer token for REST api call. I got a NullPointerException
Blockquote
Error when issuing the access token. {org.wso2.carbon.identity.oauth2.OAuth2Service}
java.lang.NullPointerException
at org.opensaml.security.SAMLSignatureProfileValidator.validate(SAMLSignatureProfileValidator.java:47)
at org.wso2.carbon.identity.oauth2.token.handlers.grant.saml.SAML2BearerGrantHandler.validateGrant(SAML2BearerGrantHandler.java:386)
at org.wso2.carbon.identity.oauth2.token.AccessTokenIssuer.issue(AccessTokenIssuer.java:144)
at org.wso2.carbon.identity.oauth2.OAuth2Service.issueAccessToken(OAuth2Service.java:177)
at org.wso2.carbon.identity.oauth.endpoint.token.OAuth2TokenEndpoint.getAccessToken(OAuth2TokenEndpoint.java:233)
at org.wso2.carbon.identity.oauth.endpoint.token.OAuth2TokenEndpoint.issueAccessToken(OAuth2TokenEndpoint.java:108)
at sun.reflect.GeneratedMethodAccessor99.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.apache.cxf.service.invoker.AbstractInvoker.performInvocation(AbstractInvoker.java:180)
at org.apache.cxf.service.invoker.AbstractInvoker.invoke(AbstractInvoker.java:96)
at org.apache.cxf.jaxrs.JAXRSInvoker.invoke(JAXRSInvoker.java:194)
at org.apache.cxf.jaxrs.JAXRSInvoker.invoke(JAXRSInvoker.java:100)
at org.apache.cxf.interceptor.ServiceInvokerInterceptor$1.run(ServiceInvokerInterceptor.java:57)
at org.apache.cxf.interceptor.ServiceInvokerInterceptor.handleMessage(ServiceInvokerInterceptor.java:93)
at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:271)
at org.apache.cxf.transport.ChainInitiationObserver.onMessage(ChainInitiationObserver.java:121)
at org.apache.cxf.transport.http.AbstractHTTPDestination.invoke(AbstractHTTPDestination.java:239)
at org.apache.cxf.transport.servlet.ServletController.invokeDestination(ServletController.java:223)
at org.apache.cxf.transport.servlet.ServletController.invoke(ServletController.java:203)
at org.apache.cxf.transport.servlet.ServletController.invoke(ServletController.java:137)
at org.apache.cxf.transport.servlet.CXFNonSpringServlet.invoke(CXFNonSpringServlet.java:159)
at org.apache.cxf.transport.servlet.AbstractHTTPServlet.handleRequest(AbstractHTTPServlet.java:286)
at org.apache.cxf.transport.servlet.AbstractHTTPServlet.doPost(AbstractHTTPServlet.java:206)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:755)
at org.apache.cxf.transport.servlet.AbstractHTTPServlet.service(AbstractHTTPServlet.java:262)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.wso2.carbon.tomcat.ext.valves.CompositeValve.continueInvocation(CompositeValve.java:178)
at org.wso2.carbon.tomcat.ext.valves.CarbonTomcatValve$1.invoke(CarbonTomcatValve.java:47)
at org.wso2.carbon.webapp.mgt.TenantLazyLoaderValve.invoke(TenantLazyLoaderValve.java:56)
at org.wso2.carbon.tomcat.ext.valves.TomcatValveContainer.invokeValves(TomcatValveContainer.java:47)
at org.wso2.carbon.tomcat.ext.valves.CompositeValve.invoke(CompositeValve.java:141)
at org.wso2.carbon.tomcat.ext.valves.CarbonStuckThreadDetectionValve.invoke(CarbonStuckThreadDetectionValve.java:156)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.wso2.carbon.tomcat.ext.valves.CarbonContextCreatorValve.invoke(CarbonContextCreatorValve.java:52)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1653)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)
Blockquote

Answer 1

The solution is to always sign an assertion for bearer token service call.
So you have to Enable Assertion Encryption in your saml SP