1. A method of access rights validation for a multiprotocol supported file server, comprising: receiving a request to store a file on a file server from an owner protocol, the request to store comprising the file and a security descriptor; storing the file on the file server; storing the security descriptor according to a specification of the owner protocol in an extended attribute associated with the file; receiving a request to open the file from a requestor protocol having a user ID; expanding the security descriptor to extract a set of ACEs (access control entries), wherein the set of ACEs comprises at least one of an NTFS, an NFS, and a POSIX access control entry; transforming the user ID to a mapped ID according to the specification of the owner protocol; and validating the mapped ID against the set of ACEs expanded from the security descriptor according to the specification of the owner protocol.