Getting "signed fields invalid" when configure HTTPS to Elastic HTTP layer with X-Pack

No, not really at this point. This looks like the certificate you are using is malformed. Elasticsearch fails to start because it deems the configuration invalid, which in turn is caused by:

Caused by: java.security.cert.CertificateParsingException: signed fields invalid at 
sun.security.x509.X509CertImpl.parse(X509CertImpl.java:1830) ~[?:?] at 
sun.security.x509.X509CertImpl.<init>(X509CertImpl.java:188) ~[?:?] at 
sun.security.provider.X509Factory.parseX509orPKCS7Cert(X509Factory.java:476) ~[?:?] at 
sun.security.provider.X509Factory.engineGenerateCertificates(X509Factory.java:361) ~[?:?] at 
java.security.cert.CertificateFactory.generateCertificates(CertificateFactory.java:478) ~[?:?]

This is not elasticsearch, it's code from sun.security.x509.X509CertImpl that throws this exception ( https://github.com/AdoptOpenJDK/openjdk-jdk11/blob/999dbd4192d0f819cb5224f26e9e7fa75ca6f289/src/java.base/share/classes/sun/security/x509/X509CertImpl.java#L1841) .

Which Java version are you using ?