We generate certificates that are intended to be used for server authentication in a couple of places:

- `bin/elasticsearch-certutil http` command  ( See `CertGenUtils.generateSignedCertificate` in `HttpCertificateCommand` )
- TLS auto-configuraion for node startup ( see [`AutoConfigureNode`](https://github.com/elastic/elasticsearch/blob/814f7f9f52cb8c05db6465b9bfc818ea5d76c575/x-pack/plugin/security/cli/src/main/java/org/elasticsearch/xpack/security/cli/AutoConfigureNode.java#L454) )

In these cases we know that the certificate is meant to be used for server authentication, so we can set Extended Key Usage extension to `1.3.6.1.5.5.7.3.1`
x-pack/plugin/security/cli/src/main/java/org/elasticsearch/xpack/security/cli/AutoConfigureNode.java
boolean canBecomeMaster = DiscoveryNode.isMasterNode(settings)
                && false == DiscoveryNode.hasRole(settings, DiscoveryNodeRole.VOTING_ONLY_NODE_ROLE);
            if (false == canBecomeMaster) {
                terminal.println(
                    Terminal.Verbosity.VERBOSE,
                    "Skipping security auto configuration because the node is configured such that it cannot become master."
                );
                throw new UserException(ExitCodes.NOOP, null);
            }
            
            boolean canHoldSecurityIndex = DiscoveryNode.canContainData(settings);
            if (false == canHoldSecurityIndex) {
                terminal.println(
                    Terminal.Verbosity.VERBOSE,
                    "Skipping security auto configuration because the node is configured such that it cannot contain data."
                );
                throw new UserException(ExitCodes.NOOP, null);
            }
        }
        
        
        
        
        
    }