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/HttpCertificateCommand.java
try {
            final X509Certificate[] certificates = CertParsingUtils.readX509Certificates(List.of(path));
            switch (certificates.length) {
                case 0:
                    terminal.errorPrintln("Could not read any certificates from " + path);
                    throw new UserException(ExitCodes.DATA_ERROR, path + ": No certificates found");
                case 1:
                    return certificates[0];
                default:
                    terminal.errorPrintln("Read [" + certificates.length + "] certificates from " + path + " but expected 1");
                    throw new UserException(ExitCodes.DATA_ERROR, path + ": Multiple certificates found");
            }
        } catch (CertificateException | IOException e) {
            throw new ElasticsearchException("Failed to read certificates from " + path, e);
        }
    }
    private PrivateKey readPrivateKey(Path path, Terminal terminal) {
        try {
            return PemUtils.readPrivateKey(path, () -> {
                terminal.println("");
                terminal.println("The PEM key stored in " + path + " requires a password.");
                terminal.println("");
                return terminal.readSecret("Password for " + path.getFileName() + ":");
            });
        } catch (IOException | GeneralSecurityException e) {
            throw new ElasticsearchException("Failed to read private key from " + path, e);
        }
    }
    private boolean askExistingCertificateAuthority(Terminal terminal) {
        printHeader("Do you have an existing Certificate Authority (CA) key-pair that you wish to use to sign your certificate?", terminal);