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
}
        }
        Path tmpPath = basePath.resolve(fileName + "." + UUIDs.randomBase64UUID() + ".tmp");
        try (OutputStream outputStream = Files.newOutputStream(tmpPath, StandardOpenOption.CREATE_NEW)) {
            writer.accept(outputStream);
        }
        
        try {
            PosixFileAttributeView view = Files.getFileAttributeView(tmpPath, PosixFileAttributeView.class);
            if (view != null) {
                view.setPermissions(permission);
                if (null != groupOwner) {
                    UserPrincipalLookupService lookupService = PathUtils.getDefaultFileSystem().getUserPrincipalLookupService();
                    GroupPrincipal groupPrincipal = lookupService.lookupPrincipalByGroupName(groupOwner);
                    view.setGroup(groupPrincipal);
                }
            }
            if (replace) {
                Files.move(tmpPath, filePath, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
            } else {
                Files.move(tmpPath, filePath, StandardCopyOption.ATOMIC_MOVE);
            }
        } finally {
            Files.deleteIfExists(tmpPath);
        }
    }
    private static void fullyWriteFile(Path basePath, String fileName, boolean replace, CheckedConsumer<OutputStream, Exception> writer)
        throws Exception {
        fullyWriteFile(basePath, fileName, replace, null, writer);
    }