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
nodeKeystore.save(env.configFile(), nodeKeystorePassword.get() == null ? new char[0] : nodeKeystorePassword.get().getChars());
        } catch (Throwable t) {
            
            try {
                if (Files.exists(keystoreBackupPath)) {
                    Files.move(
                        keystoreBackupPath,
                        keystorePath,
                        StandardCopyOption.REPLACE_EXISTING,
                        StandardCopyOption.ATOMIC_MOVE,
                        StandardCopyOption.COPY_ATTRIBUTES
                    );
                } else {
                    Files.deleteIfExists(keystorePath);
                }
            } catch (Exception ex) {
                t.addSuppressed(ex);
            }
            try {
                deleteDirectory(tempGeneratedTlsCertsDir);
            } catch (Exception ex) {
                t.addSuppressed(ex);
            }
            throw t;
        } finally {
            if (nodeKeystorePassword.get() != null) {
                nodeKeystorePassword.get().close();
            }
        }