private static boolean isBase64(String input) {

        try {
            Base64.getDecoder().decode(input);
            return true;
        } catch (IllegalArgumentException e) {
            return false;
        }
    }
Return true if the provided input is a valid base64-encoded string,
false otherwise.

@param input
    The string to check if base-64 encoded.

@return
    true if the provided input is a valid base64-encoded string,
    false otherwise.
extensions/guacamole-vault/modules/guacamole-vault-ksm/src/main/java/org/apache/guacamole/vault/ksm/conf/KsmAttributeService.java