PKIX path building failed in WSO2 ESB - wso2

Question

I'm getting below exception in WSO2 ESB when invoking REST API which suppose to invoke back end twitter API. I was following the steps given in this blog post. The twitter security certificate was successfully imported to the wso2 key store. What would be the reason for this? I'm using wso2 esb 4.8.1 version.
ERROR - TargetHandler I/O error: General SSLEngine problem
javax.net.ssl.SSLHandshakeException: General SSLEngine problem
at sun.security.ssl.Handshaker.checkThrown(Handshaker.java:1290)
at sun.security.ssl.SSLEngineImpl.checkTaskThrown(SSLEngineImpl.java:513)
at sun.security.ssl.SSLEngineImpl.writeAppRecord(SSLEngineImpl.java:1177)
at sun.security.ssl.SSLEngineImpl.wrap(SSLEngineImpl.java:1149)
at javax.net.ssl.SSLEngine.wrap(SSLEngine.java:469)
at org.apache.http.nio.reactor.ssl.SSLIOSession.doWrap(SSLIOSession.java:220)
at org.apache.http.nio.reactor.ssl.SSLIOSession.doHandshake(SSLIOSession.java:254)
at org.apache.http.nio.reactor.ssl.SSLIOSession.isAppInputReady(SSLIOSession.java:380)
at org.apache.http.impl.nio.reactor.AbstractIODispatch.inputReady(AbstractIODispatch.java:118)
at org.apache.http.impl.nio.reactor.BaseIOReactor.readable(BaseIOReactor.java:160)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvent(AbstractIOReactor.java:342)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvents(AbstractIOReactor.java:320)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.execute(AbstractIOReactor.java:280)
at org.apache.http.impl.nio.reactor.BaseIOReactor.execute(BaseIOReactor.java:106)
at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor$Worker.run(AbstractMultiworkerIOReactor.java:604)
at java.lang.Thread.run(Thread.java:745)
Caused by: javax.net.ssl.SSLHandshakeException: General SSLEngine problem
at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1683)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:278)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:270)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1341)
at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:153)
at sun.security.ssl.Handshaker.processLoop(Handshaker.java:868)
at sun.security.ssl.Handshaker$1.run(Handshaker.java:808)
at sun.security.ssl.Handshaker$1.run(Handshaker.java:806)
at java.security.AccessController.doPrivileged(Native Method)
at sun.security.ssl.Handshaker$DelegatedTask.run(Handshaker.java:1227)
at org.apache.http.nio.reactor.ssl.SSLIOSession.doRunTask(SSLIOSession.java:238)
at org.apache.http.nio.reactor.ssl.SSLIOSession.doHandshake(SSLIOSession.java:270)
... 9 more
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:385)
at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
at sun.security.validator.Validator.validate(Validator.java:260)
at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:326)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:283)
at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:138)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1328)
... 17 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:196)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268)
at sun.security.validator.PKIXValidator.doB`enter code here`uild(PKIXValidator.java:380)
... 23 more

Answer 1

Export Certificates
Go to https://YOUR_SERVER_HOST.com/, click on the lock icon at the address bar, click on the 'Connection' tab, then click on the link 'Certificate Information'. From the 'Certificate Viewer', select the tab 'Details' and click on the 'Export' button and download the certificate (YOUR_SERVER_HOST.com) to a preferred location.
Import to wso2esb "client-truststore" using following commands
$ cd %WSO2_HOME%/repository/resources/security
$ keytool -importcert -file $path/YOUR_SERVER_HOST.com.cer -keystore client-truststore.jks -alias "YOUR_SERVER_HOST.com"
Use Password "wso2carbon" when ask

Answer 2

I had a similar problem with another wso2 product. I had successfully imported the certificate into the store. It appears it only reloads the keystore on restart of the server, so yoo will have to restart your server (if you haven't already).
Also, there are 2 keystores, the wso2carbon.jks (which is what I assume you are referring to) and the client-truststore.jks. You maky need to import it into the client-truststore.jks.
Hope that is of some help.
Cheers
Matt