Security Negotiation for WebNFS
RFC 2755

Document Type RFC - Informational (January 2000; No errata)
Last updated 2013-03-02
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Network Working Group                                             A. Chiu
Request for Comments: 2755                                      M. Eisler
Category: Informational                                      B. Callaghan
                                                         Sun Microsystems
                                                             January 2000

                    Security Negotiation for WebNFS

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 (2000).  All Rights Reserved.

Abstract

   This document describes a protocol for a WebNFS client [RFC2054] to
   negotiate the desired security mechanism with a WebNFS server
   [RFC2055] before the WebNFS client falls back to the MOUNT v3
   protocol [RFC1813].  This document is provided so that people can
   write compatible implementations.

Table of Contents

   1. Introduction ..............................................  2
   2. Security Negotiation Multi-component LOOKUP ...............  3
   3  Overloaded Filehandle .....................................  4
   3.1  Overloaded NFS Version 2 Filehandle .....................  5
   3.2  Overloaded NFS Version 3 Filehandle .....................  6
   4. WebNFS Security Negotiation ...............................  6
   5. Security Considerations ................................... 10
   6. References ................................................ 10
   7. Acknowledgements .......................................... 10
   8. Authors' Addresses ........................................ 11
   9. Full Copyright Statement .................................. 12

Chiu, et al.                 Informational                      [Page 1]
RFC 2755            Security Negotiation for WebNFS         January 2000

1. Introduction

   The MOUNT protocol is used by an NFS client to obtain the necessary
   filehandle for data access.  MOUNT versions 1 and 2 [RFC1094] return
   NFS version 2 filehandles, whereas MOUNT version 3 [RFC1813] returns
   NFS version 3 filehandles.

   Among the existing versions of the MOUNT protocol, only the MOUNT v3
   provides an RPC procedure (MOUNTPROC3_MNT) which facilitates security
   negotiation between an NFS v3 client and an NSF v3 server.  When this
   RPC procedure succeeds (MNT3_OK) the server returns to the client an
   array of security mechanisms it supports for the specified pathname,
   in addition to an NFS v3 filehandle.

   A security mechanism referred to in this document is a generalized
   security flavor which can be an RPC authentication flavor [RFC1831]
   or a security flavor referred to in the RPCSEC_GSS protocol
   [RFC2203]. A security mechanism is represented as a four-octet
   integer.

   No RPC procedures are available for security negotiation in versions
   1 or 2 of the MOUNT protocol.

   The NFS mount command provides a "sec=" option for an NFS client to
   specify the desired security mechanism to use for NFS transactions.
   If this mount option is not specified, the default action is to use
   the default security mechanism over NFS v2 mounts, or to negotiate a
   security mechanism via the MOUNTPROC3_MNT procedure of MOUNT v3 and
   use it over NFS v3 mounts.  In the latter, the client picks the first
   security mechanism in the array returned from the server that is also
   supported on the client.

   As specified in RFC 2054, a WebNFS client first assumes that the
   server supports WebNFS and uses the publsc filehandle as the initial
   filehandle for data access, eliminating the need for the MOUNT
   protocol.  The WebNFS client falls back to MOUNT if the server does
   not support WebNFS.

   Since a WebNFS client does not use MOUNT initially, the
   MOUNTPROC3_MNT procedure of MOUNT v3 is not available for security
   negotiation until the WebNFS client falls back to MOUNT.  A viable
   protocol needs to be devised for the WebNFS client to negotiate
   security mechanisms with the server in the absence of the
   MOUNTPROC3_MNT procedure.

Chiu, et al.                 Informational                      [Page 2]
RFC 2755            Security Negotiation for WebNFS         January 2000

   The WebNFS security negotiation protocol must meet the following
   requirements:

      - Must work seamlessly with NFS v2 and v3, and the WebNFS
         protocols

      - Must be backward compatible with servers that do not support
         this negotiation

      - Minimum number of network turnarounds (latency)

   This document describes the WebNFS security negotiation protocol
   developed by Sun Microsystems, Inc.  Terminology and definitions from
   RFCs 2054 and 2055 are used in this document.  The reader is expected
   to be familiar with them.

2. Security Negotiation Multi-component LOOKUP

   The goal of the WebNFS security negotiation is to allow a WebNFS
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