Authentication Mechanisms for ONC RPC
RFC 2695

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Network Working Group                                           A. Chiu
Request for Comments: 2695                             Sun Microsystems
Category: Informational                                  September 1999

                 Authentication Mechanisms for ONC RPC

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

ABSTRACT

   This document describes two authentication mechanisms created by Sun
   Microsystems that are commonly used in conjunction with the ONC
   Remote Procedure Call (ONC RPC Version 2) protocol.

WARNING

   The DH authentication as defined in Section 2 in this document refers
   to the authentication mechanism with flavor AUTH_DH currently
   implemented in ONC RPC.  It uses the underlying Diffie-Hellman
   algorithm for key exchange.  The DH authentication defined in this
   document is flawed due to the selection of a small prime for the BASE
   field (Section 2.5). To avoid the flaw a new DH authentication
   mechanism could be defined with a larger prime.  However, the new DH
   authentication would not be interoperable with the existing DH
   authentication.

   As illustrated in [10], a large number of attacks are possible on ONC
   RPC system services that use non-secure authentication mechanisms.
   Other secure authentication mechanisms need to be developed for ONC
   RPC.  RFC 2203 describes the RPCSEC_GSS ONC RPC security flavor, a
   secure authentication mechanism that enables RPC protocols to use
   Generic Security Service Application Program Interface (RFC 2078) to
   provide security services, integrity and privacy, that are
   independent of the underlying security mechanisms.

Chiu                         Informational                      [Page 1]
RFC 2695         Authentication Mechanisms for ONC RPC    September 1999

Table of Contents

      1. Introduction ............................................... 2
      2. Diffie-Hellman Authentication .............................. 2
      2.1 Naming .................................................... 3
      2.2 DH Authentication Verifiers ............................... 3
      2.3 Nicknames and Clock Synchronization ....................... 5
      2.4 DH Authentication Protocol Specification .................. 5
      2.4.1 The Full Network Name Credential and Verifier (Client) .. 6
      2.4.2 The Nickname Credential and Verifier (Client) ........... 8
      2.4.3 The Nickname Verifier (Server) .......................... 9
      2.5 Diffie-Hellman Encryption ................................. 9
      3. Kerberos-based Authentication ............................. 10
      3.1 Naming ................................................... 11
      3.2 Kerberos-based Authentication Protocol Specification ..... 11
      3.2.1 The Full Network Name Credential and Verifier (Client) . 12
      3.2.2 The Nickname Credential and Verifier (Client) .......... 14
      3.2.3 The Nickname Verifier (Server) ......................... 15
      3.2.4 Kerberos-specific Authentication Status Values ......... 15
      4. Security Considerations ................................... 16
      5. REFERENCES ................................................ 16
      6. AUTHOR'S ADDRESS .......................................... 17
      7. FULL COPYRIGHT STATEMENT ...................................18

1. Introduction

   The ONC RPC protocol provides the fields necessary for a client to
   identify itself to a service, and vice-versa, in each call and reply
   message.  Security and access control mechanisms can be built on top
   of this message authentication.  Several different authentication
   protocols can be supported.

   This document specifies two authentication protocols created by Sun
   Microsystems that are commonly used: Diffie-Hellman (DH)
   authentication and Kerberos (Version 4) based authentication.

   As a prerequisite to reading this document, the reader is expected to
   be familiar with [1] and [2].  This document uses terminology and
   definitions from [1] and [2].

2. Diffie-Hellman Authentication

   System authentication (defined in [1]) suffers from some problems.
   It is very UNIX oriented, and can be easily faked (there is no
   attempt to provide cryptographically secure authentication).

Chiu                         Informational                      [Page 2]
RFC 2695         Authentication Mechanisms for ONC RPC    September 1999

   DH authentication was created to address these problems.  However, it
   has been compromised [9] due to the selection of a small length for
   the prime in the ONC RPC implementation.  While the information
   provided here will be useful for implementors to ensure
   interoperability with existing applications that use DH
   authentication, it is strongly recommended that new applications use