





Network Working Group                                          J. Kabat
Request for Comments: 2853                               ValiCert, Inc.
Category: Standards Track                                   M. Upadhyay
                                                 Sun Microsystems, Inc.
                                                              June 2000


         Generic Security Service API Version 2 : Java Bindings

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   The Generic Security Services Application Program Interface (GSS-API)
   offers application programmers uniform access to security services
   atop a variety of underlying cryptographic mechanisms. This document
   specifies the Java bindings for GSS-API which is described at a
   language independent conceptual level in RFC 2743 [GSSAPIv2-UPDATE].

   The GSS-API allows a caller application to authenticate a principal
   identity, to delegate rights to a peer, and to apply security
   services such as confidentiality and integrity on a per-message
   basis. Examples of security mechanisms defined for GSS-API are The
   Simple Public-Key GSS-API Mechanism [SPKM] and The Kerberos Version 5
   GSS-API Mechanism [KERBV5].

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  GSS-API Operational Paradigm . . . . . . . . . . . . . . .   6
   3.  Additional Controls  . . . . . . . . . . . . . . . . . . .   8
   3.1.  Delegation . . . . . . . . . . . . . . . . . . . . . . .   9
   3.2.  Mutual Authentication  . . . . . . . . . . . . . . . . .  10
   3.3.  Replay and Out-of-Sequence Detection . . . . . . . . . .  10
   3.4.  Anonymous Authentication . . . . . . . . . . . . . . . .  11
   3.5.  Confidentiality  . . . . . . . . . . . . . . . . . . . .  12
   3.6.  Inter-process Context Transfer . . . . . . . . . . . . .  12
   3.7.  The Use of Incomplete Contexts . . . . . . . . . . . . .  13



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   4.  Calling Conventions  . . . . . . . . . . . . . . . . . . .  13
   4.1.  Package Name . . . . . . . . . . . . . . . . . . . . . .  13
   4.2.  Provider Framework . . . . . . . . . . . . . . . . . . .  13
   4.3.  Integer types  . . . . . . . . . . . . . . . . . . . . .  14
   4.4.  Opaque Data types  . . . . . . . . . . . . . . . . . . .  14
   4.5.  Strings  . . . . . . . . . . . . . . . . . . . . . . . .  15
   4.6.  Object Identifiers . . . . . . . . . . . . . . . . . . .  15
   4.7.  Object Identifier Sets . . . . . . . . . . . . . . . . .  15
   4.8.  Credentials  . . . . . . . . . . . . . . . . . . . . . .  16
   4.9.  Contexts . . . . . . . . . . . . . . . . . . . . . . . .  18
   4.10.  Authentication tokens . . . . . . . . . . . . . . . . .  18
   4.11.  Interprocess tokens . . . . . . . . . . . . . . . . . .  18
   4.12.  Error Reporting . . . . . . . . . . . . . . . . . . . .  19
   4.12.1.  GSS status codes  . . . . . . . . . . . . . . . . . .  19
   4.12.2.  Mechanism-specific status codes . . . . . . . . . . .  21
   4.12.3.  Supplementary status codes  . . . . . . . . . . . . .  21
   4.13.  Names . . . . . . . . . . . . . . . . . . . . . . . . .  22
   4.14.  Channel Bindings  . . . . . . . . . . . . . . . . . . .  25
   4.15.  Stream Objects  . . . . . . . . . . . . . . . . . . . .  26
   4.16.  Optional Parameters . . . . . . . . . . . . . . . . . .  26
   5.  Introduction to GSS-API Classes and Interfaces . . . . . .  26
   5.1.  GSSManager class . . . . . . . . . . . . . . . . . . . .  26
   5.2.  GSSName interface  . . . . . . . . . . . . . . . . . . .  27
   5.3.  GSSCredential interface  . . . . . . . . . . . . . . . .  28
   5.4.  GSSContext interface . . . . . . . . . . . . . . . . . .  28
   5.5.  MessageProp class  . . . . . . . . . . . . . . . . . . .  30
   5.6.  GSSException class . . . . . . . . . . . . . . . . . . .  30
   5.7.  Oid class  . . . . . . . . . . . . . . . . . . . . . . .  30
   5.8.  ChannelBinding class . . . . . . . . . . . . . . . . . .  31
   6.  Detailed GSS-API Class Description . . . . . . . . . . . .  31
   6.1.  public abstract class GSSManager . . . . . . . . . . . .  31
   6.1.1.  Example Code . . . . . . . . . . . . . . . . . . . . .  32
   6.1.2.  getInstance  . . . . . . . . . . . . . . . . . . . . .  33
   6.1.3.  getMechs . . . . . . . . . . . . . . . . . . . . . . .  33
   6.1.4.  getNamesForMech  . . . . . . . . . . . . . . . . . . .  33
   6.1.5.  getMechsForName  . . . . . . . . . . . . . . . . . . .  33
   6.1.6.  createName . . . . . . . . . . . . . . . . . . . . . .  33
   6.1.7.  createName . . . . . . . . . . . . . . . . . . . . . .  34
   6.1.8.  createName . . . . . . . . . . . . . . . . . . . . . .  35
   6.1.9.  createName . . . . . . . . . . . . . . . . . . . . . .  35
   6.1.10.  createCredential  . . . . . . . . . . . . . . . . . .  36
   6.1.11.  createCredential  . . . . . . . . . . . . . . . . . .  36
   6.1.12.  createCredential  . . . . . . . . . . . . . . . . . .  37
   6.1.13.  createContext . . . . . . . . . . . . . . . . . . . .  37
   6.1.14.  createContext . . . . . . . . . . . . . . . . . . . .  38
   6.1.15.  createContext . . . . . . . . . . . . . . . . . . . .  38
   6.1.16.  addProviderAtFront  . . . . . . . . . . . . . . . . .  38
   6.1.16.1.  Example Code  . . . . . . . . . . . . . . . . . . .  39



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   6.1.17.  addProviderAtEnd  . . . . . . . . . . . . . . . . . .  40
   6.1.17.1.  Example Code  . . . . . . . . . . . . . . . . . . .  41
   6.2.  public interface GSSName . . . . . . . . . . . . . . . .  42
   6.2.1.  Example Code . . . . . . . . . . . . . . . . . . . . .  42
   6.2.2.  Static Constants . . . . . . . . . . . . . . . . . . .  43
   6.2.3.  equals . . . . . . . . . . . . . . . . . . . . . . . .  44
   6.2.4.  equals . . . . . . . . . . . . . . . . . . . . . . . .  44
   6.2.5.  canonicalize . . . . . . . . . . . . . . . . . . . . .  44
   6.2.6.  export . . . . . . . . . . . . . . . . . . . . . . . .  45
   6.2.7.  toString . . . . . . . . . . . . . . . . . . . . . . .  45
   6.2.8.  getStringNameType  . . . . . . . . . . . . . . . . . .  45
   6.2.9.  isAnonymous  . . . . . . . . . . . . . . . . . . . . .  45
   6.2.10.  isMN  . . . . . . . . . . . . . . . . . . . . . . . .  45
   6.3.  public interface GSSCredential implements Cloneable  . .  45
   6.3.1.  Example Code . . . . . . . . . . . . . . . . . . . . .  46
   6.3.2.  Static Constants . . . . . . . . . . . . . . . . . . .  47
   6.3.3.  dispose  . . . . . . . . . . . . . . . . . . . . . . .  48
   6.3.4.  getName  . . . . . . . . . . . . . . . . . . . . . . .  48
   6.3.5.  getName  . . . . . . . . . . . . . . . . . . . . . . .  48
   6.3.6.  getRemainingLifetime . . . . . . . . . . . . . . . . .  48
   6.3.7.  getRemainingInitLifetime . . . . . . . . . . . . . . .  49
   6.3.8.  getRemainingAcceptLifetime . . . . . . . . . . . . . .  49
   6.3.9.  getUsage . . . . . . . . . . . . . . . . . . . . . . .  49
   6.3.10.  getUsage  . . . . . . . . . . . . . . . . . . . . . .  49
   6.3.11.  getMechs  . . . . . . . . . . . . . . . . . . . . . .  50
   6.3.12.  add . . . . . . . . . . . . . . . . . . . . . . . . .  50
   6.3.13.  equals  . . . . . . . . . . . . . . . . . . . . . . .  51
   6.4.  public interface GSSContext  . . . . . . . . . . . . . .  51
   6.4.1.  Example Code . . . . . . . . . . . . . . . . . . . . .  52
   6.4.2.  Static Constants . . . . . . . . . . . . . . . . . . .  54
   6.4.3.  initSecContext . . . . . . . . . . . . . . . . . . . .  54
   6.4.3.1.  Example Code . . . . . . . . . . . . . . . . . . . .  55
   6.4.4.  initSecContext . . . . . . . . . . . . . . . . . . . .  56
   6.4.4.1.  Example Code . . . . . . . . . . . . . . . . . . . .  56
   6.4.5.  acceptSecContext . . . . . . . . . . . . . . . . . . .  57
   6.4.5.1.  Example Code . . . . . . . . . . . . . . . . . . . .  58
   6.4.6.  acceptSecContext . . . . . . . . . . . . . . . . . . .  59
   6.4.6.1.  Example Code . . . . . . . . . . . . . . . . . . . .  59
   6.4.7.  isEstablished  . . . . . . . . . . . . . . . . . . . .  60
   6.4.8.  dispose  . . . . . . . . . . . . . . . . . . . . . . .  60
   6.4.9.  getWrapSizeLimit . . . . . . . . . . . . . . . . . . .  61
   6.4.10.  wrap  . . . . . . . . . . . . . . . . . . . . . . . .  61
   6.4.11.  wrap  . . . . . . . . . . . . . . . . . . . . . . . .  62
   6.4.12.  unwrap  . . . . . . . . . . . . . . . . . . . . . . .  63
   6.4.13.  unwrap  . . . . . . . . . . . . . . . . . . . . . . .  64
   6.4.14.  getMIC  . . . . . . . . . . . . . . . . . . . . . . .  65
   6.4.15.  getMIC  . . . . . . . . . . . . . . . . . . . . . . .  65
   6.4.16.  verifyMIC . . . . . . . . . . . . . . . . . . . . . .  66



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   6.4.17.  verifyMIC . . . . . . . . . . . . . . . . . . . . . .  67
   6.4.18.  export  . . . . . . . . . . . . . . . . . . . . . . .  68
   6.4.19.  requestMutualAuth . . . . . . . . . . . . . . . . . .  68
   6.4.20.  requestReplayDet  . . . . . . . . . . . . . . . . . .  69
   6.4.21.  requestSequenceDet  . . . . . . . . . . . . . . . . .  69
   6.4.22.  requestCredDeleg  . . . . . . . . . . . . . . . . . .  69
   6.4.23.  requestAnonymity  . . . . . . . . . . . . . . . . . .  69
   6.4.24.  requestConf . . . . . . . . . . . . . . . . . . . . .  70
   6.4.25.  requestInteg  . . . . . . . . . . . . . . . . . . . .  70
   6.4.26.  requestLifetime . . . . . . . . . . . . . . . . . . .  70
   6.4.27.  setChannelBinding . . . . . . . . . . . . . . . . . .  71
   6.4.28.  getCredDelegState . . . . . . . . . . . . . . . . . .  71
   6.4.29.  getMutualAuthState  . . . . . . . . . . . . . . . . .  71
   6.4.30.  getReplayDetState . . . . . . . . . . . . . . . . . .  71
   6.4.31.  getSequenceDetState . . . . . . . . . . . . . . . . .  71
   6.4.32.  getAnonymityState . . . . . . . . . . . . . . . . . .  72
   6.4.33.  isTransferable  . . . . . . . . . . . . . . . . . . .  72
   6.4.34.  isProtReady . . . . . . . . . . . . . . . . . . . . .  72
   6.4.35.  getConfState  . . . . . . . . . . . . . . . . . . . .  72
   6.4.36.  getIntegState . . . . . . . . . . . . . . . . . . . .  72
   6.4.37.  getLifetime . . . . . . . . . . . . . . . . . . . . .  73
   6.4.38.  getSrcName  . . . . . . . . . . . . . . . . . . . . .  73
   6.4.39.  getTargName . . . . . . . . . . . . . . . . . . . . .  73
   6.4.40.  getMech . . . . . . . . . . . . . . . . . . . . . . .  73
   6.4.41.  getDelegCred  . . . . . . . . . . . . . . . . . . . .  73
   6.4.42.  isInitiator . . . . . . . . . . . . . . . . . . . . .  73
   6.5.  public class MessageProp . . . . . . . . . . . . . . . .  74
   6.5.1.  Constructors . . . . . . . . . . . . . . . . . . . . .  74
   6.5.2.  getQOP . . . . . . . . . . . . . . . . . . . . . . . .  75
   6.5.3.  getPrivacy . . . . . . . . . . . . . . . . . . . . . .  75
   6.5.4.  getMinorStatus . . . . . . . . . . . . . . . . . . . .  75
   6.5.5.  getMinorString . . . . . . . . . . . . . . . . . . . .  75
   6.5.6.  setQOP . . . . . . . . . . . . . . . . . . . . . . . .  75
   6.5.7.  setPrivacy . . . . . . . . . . . . . . . . . . . . . .  75
   6.5.8.  isDuplicateToken . . . . . . . . . . . . . . . . . . .  76
   6.5.9.  isOldToken . . . . . . . . . . . . . . . . . . . . . .  76
   6.5.10.  isUnseqToken  . . . . . . . . . . . . . . . . . . . .  76
   6.5.11.  isGapToken  . . . . . . . . . . . . . . . . . . . . .  76
   6.5.12.  setSupplementaryStates  . . . . . . . . . . . . . . .  76
   6.6.  public class ChannelBinding  . . . . . . . . . . . . . .  77
   6.6.1.  Constructors . . . . . . . . . . . . . . . . . . . . .  77
   6.6.2.  getInitiatorAddress  . . . . . . . . . . . . . . . . .  78
   6.6.3.  getAcceptorAddress . . . . . . . . . . . . . . . . . .  78
   6.6.4.  getApplicationData . . . . . . . . . . . . . . . . . .  78
   6.6.5.  equals . . . . . . . . . . . . . . . . . . . . . . . .  78
   6.7.  public class Oid . . . . . . . . . . . . . . . . . . . .  79
   6.7.1.  Constructors . . . . . . . . . . . . . . . . . . . . .  79
   6.7.2.  toString . . . . . . . . . . . . . . . . . . . . . . .  80



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   6.7.3.  equals . . . . . . . . . . . . . . . . . . . . . . . .  80
   6.7.4.  getDER . . . . . . . . . . . . . . . . . . . . . . . .  80
   6.7.5.  containedIn  . . . . . . . . . . . . . . . . . . . . .  80
   6.8.  public class GSSException extends Exception  . . . . . .  80
   6.8.1.  Static Constants . . . . . . . . . . . . . . . . . . .  81
   6.8.2.  Constructors . . . . . . . . . . . . . . . . . . . . .  83
   6.8.3.  getMajor . . . . . . . . . . . . . . . . . . . . . . .  84
   6.8.4.  getMinor . . . . . . . . . . . . . . . . . . . . . . .  84
   6.8.5.  getMajorString . . . . . . . . . . . . . . . . . . . .  84
   6.8.6.  getMinorString . . . . . . . . . . . . . . . . . . . .  84
   6.8.7.  setMinor . . . . . . . . . . . . . . . . . . . . . . .  84
   6.8.8.  toString . . . . . . . . . . . . . . . . . . . . . . .  85
   6.8.9.  getMessage . . . . . . . . . . . . . . . . . . . . . .  85
   7.  Sample Applications  . . . . . . . . . . . . . . . . . . .  85
   7.1.  Simple GSS Context Initiator . . . . . . . . . . . . . .  85
   7.2.  Simple GSS Context Acceptor  . . . . . . . . . . . . . .  89
   8.  Security Considerations  . . . . . . . . . . . . . . . . .  93
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . .  94
   10.  Bibliography  . . . . . . . . . . . . . . . . . . . . . .  94
   11.  Authors' Addresses  . . . . . . . . . . . . . . . . . . .  95
   12.  Full Copyright Statement. . . . . . . . . . . . . . . . .  96

1.  Introduction

   This document specifies Java language bindings for the Generic
   Security Services Application Programming Interface Version 2 (GSS-
   API).  GSS-API Version 2 is described in a language independent
   format in RFC 2743 [GSSAPIv2-UPDATE]. The GSS-API allows a caller
   application to authenticate a principal identity, to delegate rights
   to a peer, and to apply security services such as confidentiality and
   integrity on a per-message basis.

   This document leverages the work performed by the WG in the area of
   RFC 2743 [GSSAPIv2-UPDATE] and the C-bindings RFC 2744 [GSSAPI-C].
   Whenever appropriate, text has been used from the C-bindings RFC 2744
   to explain generic concepts and provide direction to the
   implementors.

   The design goals of this API have been to satisfy all the
   functionality defined in RFC 2743 and to provide these services in an
   object oriented method.  The specification also aims to satisfy the
   needs of both types of Java application developers, those who would
   like access to a "system-wide" GSS-API implementation, as well as
   those who would want to provide their own "custom" implementation.







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   A "system-wide" implementation is one that is available to all
   applications in the form of a library package.  It may be a standard
   package in the Java runtime environment (JRE) being used or it may be
   additionally installed and accessible to any application via the
   CLASSPATH.

   A "custom" implementation of the GSS-API, on the other hand, is one
   that would, in most cases, be bundled with the application during
   distribution.  It is expected that such an implementation would be
   meant to provide for some particular need of the application, such as
   support for some specific mechanism.

   The design of this API also aims to provide a flexible framework to
   add and manage GSS-API mechanisms. GSS-API leverages the Java
   Cryptography Architecture (JCA) provider model to support the
   plugability of mechanisms.  Mechanisms can be added on a "system-
   wide" basis, where all users of the framework will have them
   available. The specification also allows for the addition of
   mechanisms per-instance of the GSS-API.

   Lastly, this specification presents an API that will naturally fit
   within the operation environment of the Java platform.  Readers are
   assumed to be familiar with both the GSS-API and the Java platform.

2.  GSS-API Operational Paradigm

   The Generic Security Service Application Programming Interface
   Version 2 [GSSAPIv2-UPDATE] defines a generic security API to calling
   applications.  It allows a communicating application to authenticate
   the user associated with another application, to delegate rights to
   another application, and to apply security services such as
   confidentiality and integrity on a per-message basis.

      There are four stages to using GSS-API:

      1) The application acquires a set of credentials with which it may
         prove its identity to other processes.  The application's
         credentials vouch for its global identity, which may or may not
         be related to any local username under which it may be running.

      2) A pair of communicating applications establish a joint security
         context using their credentials.  The security context
         encapsulates shared state information, which is required in
         order that per-message security services may be provided.
         Examples of state information that might be shared between
         applications as part of a security context are cryptographic
         keys, and message sequence numbers.  As part of the
         establishment of  a security context, the context initiator is



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         authenticated to the responder, and may require that the
         responder is authenticated back to the initiator.  The
         initiator may optionally give the responder the right to
         initiate further security contexts, acting as an agent or
         delegate of the initiator.  This transfer of rights is termed
         "delegation", and is achieved by creating a set of credentials,
         similar to those used by the initiating application, but which
         may be used by the responder.

         A GSSContext object is used to establish and maintain the
         shared information that makes up the security context.  Certain
         GSSContext methods will generate a token, which applications
         treat as cryptographically protected, opaque data.  The caller
         of such GSSContext method is responsible for transferring the
         token to the peer application, encapsulated if necessary in an
         application-to-application protocol.  On receipt of such a
         token, the peer application should pass it to a corresponding
         GSSContext method which will decode the token and extract the
         information, updating the security context state information
         accordingly.

      3) Per-message services are invoked on a GSSContext object to
         apply either:

         integrity and data origin authentication, or

         confidentiality, integrity and data origin authentication

         to application data, which are treated by GSS-API as arbitrary
         octet-strings.  An application transmitting a message that it
         wishes to protect will call the appropriate GSSContext method
         (getMIC or wrap) to apply protection, and send the resulting
         token to the receiving application.  The receiver will pass the
         received token (and, in the case of data protected by getMIC,
         the accompanying message-data) to the corresponding decoding
         method of the GSSContext interface (verifyMIC or unwrap) to
         remove the protection and validate the data.

      4) At the completion of a communications session (which may extend
         across several transport connections), each application uses a
         GSSContext method to invalidate the security context and
         release any system or cryptographic resources held.  Multiple
         contexts may also be used (either successively or
         simultaneously) within a single communications association, at
         the discretion of the applications.






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3.  Additional Controls

   This section discusses the optional services that a context initiator
   may request of the GSS-API before the context establishment.  Each of
   these services is requested by calling the appropriate mutator method
   in the GSSContext object before the first call to init is performed.
   Only the context initiator can request context flags.

   The optional services defined are:

   Delegation
         The (usually temporary) transfer of rights from initiator to
         acceptor, enabling the acceptor to authenticate itself as an
         agent of the initiator.

   Mutual Authentication
         In addition to the initiator authenticating its identity to the
         context acceptor, the context acceptor should also authenticate
         itself to the initiator.

   Replay Detection
         In addition to providing message integrity services, GSSContext
         per-message operations of getMIC and wrap should include
         message numbering information  to enable verifyMIC and unwrap
         to detect if a message has been duplicated.

   Out-of-Sequence Detection
         In addition to providing message integrity services, GSSContext
         per-message operations  (getMIC and wrap) should include
         message sequencing information to enable verifyMIC and unwrap
         to detect if a message has been received out of sequence.

   Anonymous Authentication
         The establishment of the security context should not reveal the
         initiator's identity to the context acceptor.

   Some mechanisms may not support all optional services, and some
   mechanisms may only support some services in conjunction with others.
   The GSSContext interface offers query methods to allow the
   verification by the calling application of which services will be
   available from the context when the establishment phase is complete.
   In general, if the security mechanism is capable of providing a
   requested service, it should do so even if additional services must
   be enabled in order to provide the requested service.  If the
   mechanism is incapable of providing a requested service, it should
   proceed without the service leaving the application to abort the
   context establishment process if it considers the requested service
   to be mandatory.



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   Some mechanisms may specify that support for some services is
   optional, and that implementors of the mechanism need not provide it.
   This is most commonly true of the confidentiality service, often
   because of legal restrictions on the use of data-encryption, but may
   apply to any of the services.  Such mechanisms are required to send
   at least one token from acceptor to initiator during context
   establishment when the initiator indicates a desire to use such a
   service, so that the initiating GSS-API can correctly indicate
   whether the service is supported by the acceptor's GSS-API.

3.1.  Delegation

   The GSS-API allows delegation to be controlled by the initiating
   application via the requestCredDeleg method before the first call to
   init has been issued.  Some mechanisms do not support delegation, and
   for such mechanisms attempts by an application to enable delegation
   are ignored.

   The acceptor of a security context, for which the initiator enabled
   delegation, can check if delegation was enabled by using the
   getCredDelegState method of the GSSContext interface.  In cases when
   it is, the delegated credential object can be obtained by calling the
   getDelegCred method.  The obtained GSSCredential object may then be
   used to initiate subsequent GSS-API security contexts as an agent or
   delegate of the initiator.  If the original initiator's identity is
   "A" and the delegate's identity is "B", then, depending on the
   underlying mechanism, the identity embodied by the delegated
   credential may be either "A" or "B acting for A".

   For many mechanisms that support delegation, a simple boolean does
   not provide enough control.  Examples of additional aspects of
   delegation control that a mechanism might provide to an application
   are duration of delegation, network addresses from which delegation
   is valid, and constraints on the tasks that may be performed by a
   delegate.  Such controls are presently outside the scope of the GSS-
   API.  GSS-API implementations supporting mechanisms offering
   additional controls should provide extension routines that allow
   these controls to be exercised (perhaps by modifying the initiator's
   GSS-API credential object prior to its use in establishing a
   context).  However, the simple delegation control provided by GSS-API
   should always be able to over-ride other mechanism-specific
   delegation controls.  If the application instructs the GSSContext
   object that delegation is not desired, then the implementation must
   not permit delegation to occur.  This is an exception to the general
   rule that a mechanism may enable services even if they are not
   requested - delegation may only be provided at the explicit request
   of the application.




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3.2.  Mutual Authentication

   Usually, a context acceptor will require that a context initiator
   authenticate itself so that the acceptor may make an access-control
   decision prior to performing a service for the initiator.  In some
   cases, the initiator may also request that the acceptor authenticate
   itself.  GSS-API allows the initiating application to request this
   mutual authentication service by calling the requestMutualAuth method
   of the GSSContext interface with a "true" parameter before making the
   first call to init.  The initiating application is informed as to
   whether or not the context acceptor has authenticated itself.  Note
   that some mechanisms may not support mutual authentication, and other
   mechanisms may always perform mutual authentication, whether or not
   the initiating application requests it.  In particular, mutual
   authentication may be required by some mechanisms in order to support
   replay or out-of-sequence message detection, and for such mechanisms
   a request for either of these services will automatically enable
   mutual authentication.

3.3.  Replay and Out-of-Sequence Detection

   The GSS-API may provide detection of mis-ordered messages once a
   security context has been established.  Protection may be applied to
   messages by either application, by calling either getMIC or wrap
   methods of the GSSContext interface, and verified by the peer
   application by calling verifyMIC or unwrap for the peer's GSSContext
   object.

   The getMIC method calculates a cryptographic checksum of an
   application message, and returns that checksum in a token.  The
   application should pass both the token and the message to the peer
   application, which presents them to the verifyMIC method of the
   peer's GSSContext object.

   The wrap method calculates a cryptographic checksum of an application
   message, and places both the checksum and the message inside a single
   token.  The application should pass the token to the peer
   application, which presents it to the unwrap method of the peer's
   GSSContext object to extract the message and verify the checksum.

   Either pair of routines may be capable of detecting out-of-sequence
   message delivery, or duplication of messages.  Details of such mis-
   ordered messages are indicated through supplementary query methods of
   the MessageProp object that is filled in by each of these routines.

   A mechanism need not maintain a list of all tokens that have been
   processed in order to support these status codes.  A typical
   mechanism might retain information about only the most recent "N"



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   tokens processed, allowing it to distinguish duplicates and missing
   tokens within the most recent "N" messages; the receipt of a token
   older than the most recent "N" would result in the isOldToken method
   of the instance of MessageProp to return "true".

3.4.  Anonymous Authentication

   In certain situations, an application may wish to initiate the
   authentication process to authenticate a peer, without revealing its
   own identity.  As an example, consider an application providing
   access to a database containing medical information, and offering
   unrestricted access to the service.  A client of such a service might
   wish to authenticate the service (in order to establish trust in any
   information retrieved from it), but might not wish the service to be
   able to obtain the client's identity (perhaps due to privacy concerns
   about the specific inquiries, or perhaps simply to avoid being placed
   on mailing-lists).

   In normal use of the GSS-API, the initiator's identity is made
   available to the acceptor as a result of the context establishment
   process.  However, context initiators may request that their identity
   not be revealed to the context acceptor.  Many mechanisms do not
   support anonymous authentication, and for such mechanisms the request
   will not be honored.  An authentication token will still be
   generated, but the application is always informed if a requested
   service is unavailable, and has the option to abort context
   establishment if anonymity is valued above the other security
   services that would require a context to be established.

   In addition to informing the application that a context is
   established anonymously (via the isAnonymous method of the GSSContext
   class), the getSrcName method of the acceptor's GSSContext object
   will, for such contexts, return a reserved internal-form name,
   defined by the implementation.

   The toString method for a GSSName object representing an anonymous
   entity will return a printable name.  The returned value will be
   syntactically distinguishable from any valid principal name supported
   by the implementation.  The associated name-type object identifier
   will be an oid representing the value of NT_ANONYMOUS.  This name-
   type oid will be defined as a public, static Oid object of the
   GSSName class.  The printable form of an anonymous name should be
   chosen such that it implies anonymity, since this name may appear in,
   for example, audit logs.  For example, the string "<anonymous>" might
   be a good choice, if no valid printable names supported by the
   implementation can begin with "<" and end with ">".





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   When using the equal method of the GSSName interface, and one of the
   operands is a GSSName instance representing an anonymous entity, the
   method must return "false".

3.5.  Confidentiality

   If a GSSContext supports the confidentiality service, wrap method may
   be used to encrypt application messages.  Messages are selectively
   encrypted, under the control of the setPrivacy method of the
   MessageProp object used in the wrap method.

3.6.  Inter-process Context Transfer

   GSS-API V2 provides functionality which allows a security context to
   be transferred between processes on a single machine.  These are
   implemented using the export method of GSSContext and a byte array
   constructor of the same class.  The most common use for such a
   feature is a client-server design where the server is implemented as
   a single process that accepts incoming security contexts, which then
   launches child processes to deal with the data on these contexts.  In
   such a design, the child processes must have access to the security
   context object created within the parent so that they can use per-
   message protection services and delete the security context when the
   communication session ends.

   Since the security context data structure is expected to contain
   sequencing information, it is impractical in general to share a
   context between processes.  Thus GSSContext interface provides an
   export method that the process, which currently owns the context, can
   call to declare that it has no intention to use the context
   subsequently, and to create an inter-process token containing
   information needed by the adopting process to successfully re-create
   the context.  After successful completion of export, the original
   security context is made inaccessible to the calling process by GSS-
   API and any further usage of this object will result in failures.
   The originating process transfers the inter-process token to the
   adopting process, which creates a new GSSContext object using the
   byte array constructor.  The properties of the context are equivalent
   to that of the original context.

   The inter-process token may contain sensitive data from the original
   security context (including cryptographic keys).  Applications using
   inter-process tokens to transfer security contexts must take
   appropriate steps to protect these tokens in transit.







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   Implementations are not required to support the inter-process
   transfer of security contexts.  Calling the isTransferable method of
   the GSSContext interface will indicate if the context object is
   transferable.

3.7.  The Use of Incomplete Contexts

   Some mechanisms may allow the per-message services to be used before
   the context establishment process is complete.  For example, a
   mechanism may include sufficient information in its initial context-
   level tokens for the context acceptor to immediately decode messages
   protected with wrap or getMIC.  For such a mechanism, the initiating
   application need not wait until subsequent context-level tokens have
   been sent and received before invoking the per-message protection
   services.

   An application can invoke the isProtReady method of the GSSContext
   class to determine if the per-message services are available in
   advance of complete context establishment.  Applications wishing to
   use per-message protection services on partially-established contexts
   should query this method before attempting to invoke wrap or getMIC.

4.  Calling Conventions

   Java provides the implementors with not just a syntax for the
   language, but also an operational environment.  For example, memory
   is automatically managed and does not require application
   intervention.  These language features have allowed for a simpler API
   and have led to the elimination of certain GSS-API functions.

   Moreover, the JCA defines a provider model which allows for
   implementation independent access to security services. Using this
   model, applications can seamlessly switch between different
   implementations and dynamically add new services. The GSS-API
   specification leverages these concepts by the usage of providers for
   the mechanism implementations.

4.1.  Package Name

   The classes and interfaces defined in this document reside in the
   package called "org.ietf.jgss".  Applications that wish to make use
   of this API should import this package name as shown in section 7.

4.2.  Provider Framework

   The Java security API's use a provider architecture that allows
   applications to be implementation independent and security API
   implementations to be modular and extensible.  The



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   java.security.Provider class is an abstract class that a vendor
   extends.  This class maps various properties that represent different
   security services that are available to the names of the actual
   vendor classes that implement those services.  When requesting a
   service, an application simply specifies the desired provider and the
   API delegates the request to service classes available from that
   provider.

   Using the Java security provider model insulates applications from
   implementation details of the services they wish to use.
   Applications can switch between providers easily and new providers
   can be added as needed, even at runtime.

   The GSS-API may use providers to find components for specific
   underlying security mechanisms.  For instance, a particular provider
   might contain components that will allow the GSS-API to support the
   Kerberos v5 mechanism and another might contain components to support
   the SPKM mechanism.  By delegating mechanism specific functionality
   to the components obtained from providers the GSS-API can be extended
   to support an arbitrary list of mechanism.

   How the GSS-API locates and queries these providers is beyond the
   scope of this document and is being deferred to a Service Provider
   Interface (SPI) specification.  The availability of such a SPI
   specification is not mandatory for the adoption of this API
   specification nor is it mandatory to use providers in the
   implementation of a GSS-API framework. However, by using the provider
   framework together with an SPI specification one can create an
   extensible and implementation independent GSS-API framework.

4.3.  Integer types

   All numeric values are declared as "int" primitive Java type.  The
   Java specification guarantees that this will be a 32 bit two's
   complement signed number.

   Throughout this API, the "boolean" primitive Java type is used
   wherever a boolean value is required or returned.

4.4.  Opaque Data types

   Java byte arrays are used to represent opaque data types which are
   consumed and produced by the GSS-API in the forms of tokens.  Java
   arrays contain a length field which enables the users to easily
   determine their size.  The language has automatic garbage collection
   which alleviates the need by developers to release memory and
   simplifies buffer ownership issues.




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4.5.  Strings

   The String object will be used to represent all textual data.  The
   Java String object, transparently treats all characters as two-byte
   Unicode characters which allows support for many locals.  All
   routines returning or accepting textual data will use the String
   object.

4.6.  Object Identifiers

   An Oid object will be used to represent Universal Object Identifiers
   (Oids).  Oids are ISO-defined, hierarchically globally-interpretable
   identifiers used within the GSS-API framework to identify security
   mechanisms and name formats.  The Oid object can be created from a
   string representation of its dot notation (e.g. "1.3.6.1.5.6.2") as
   well as from its ASN.1 DER encoding.  Methods are also provided to
   test equality and provide the DER representation for the object.

   An important feature of the Oid class is that its instances are
   immutable - i.e.  there are no methods defined that allow one to
   change the contents of an Oid.  This property allows one to treat
   these objects as "statics" without the need to perform copies.

   Certain routines allow the usage of a default oid.  A "null" value
   can be used in those cases.

4.7.  Object Identifier Sets

   The Java bindings represents object identifiers sets as arrays of Oid
   objects.  All Java arrays contain a length field which allows for
   easy manipulation and reference.

   In order to support the full functionality of RFC 2743, the Oid class
   includes a method which checks for existence of an Oid object within
   a specified array.  This is equivalent in functionality to
   gss_test_oid_set_member.  The use of Java arrays and Java's automatic
   garbage collection has eliminated the need for the following
   routines: gss_create_empty_oid_set, gss_release_oid_set, and
   gss_add_oid_set_member.  Java GSS-API implementations will not
   contain them.  Java's automatic garbage collection and the immutable
   property of the Oid object eliminates the complicated memory
   management issues of the C counterpart.

   When ever a default value for an Object Identifier Set is required, a
   "null" value can be used.  Please consult the detailed method
   description for details.





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4.8.  Credentials

   GSS-API credentials are represented by the GSSCredential interface.
   The interface contains several constructs to allow for the creation
   of most common credential objects for the initiator and the acceptor.
   Comparisons are performed using the interface's "equals" method.  The
   following general description of GSS-API credentials is included from
   the C-bindings specification:

   GSS-API credentials can contain mechanism-specific principal
   authentication data for multiple mechanisms.  A GSS-API credential is
   composed of a set of credential-elements, each of which is applicable
   to a single mechanism.  A credential may contain at most one
   credential-element for each supported mechanism.  A credential-
   element identifies the data needed by a single mechanism to
   authenticate a single principal, and conceptually contains two
   credential-references that describe the actual mechanism-specific
   authentication data, one to be used by GSS-API for initiating
   contexts, and one to be used for accepting contexts.  For mechanisms
   that do not distinguish between acceptor and initiator credentials,
   both references would point to the same underlying mechanism-specific
   authentication data.

   Credentials describe a set of mechanism-specific principals, and give
   their holder the ability to act as any of those principals.  All
   principal identities asserted by a single GSS-API credential should
   belong to the same entity, although enforcement of this property is
   an implementation-specific matter.  A single GSSCredential object
   represents all the credential elements that have been acquired.

   The creation's of an GSSContext object allows the value of "null" to
   be specified as the GSSCredential input parameter.  This will
   indicate a desire by the application to act as a default principal.
   While individual GSS-API implementations are free to determine such
   default behavior as appropriate to the mechanism, the following
   default behavior by these routines is recommended for portability:

      For the initiator side of the context:

      1) If there is only a single principal capable of initiating
         security contexts for the chosen mechanism that the application
         is authorized to act on behalf of, then that principal shall be
         used, otherwise








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      2) If the platform maintains a concept of a default network-
         identity for the chosen mechanism, and if the application is
         authorized to act on behalf of that identity for the purpose of
         initiating security contexts, then the principal corresponding
         to that identity shall be used, otherwise

      3) If the platform maintains a concept of a default local
         identity, and provides a means to map local identities into
         network-identities for the chosen mechanism, and if the
         application is authorized to act on behalf of the network-
         identity image of the default local identity for the purpose of
         initiating security contexts using the chosen mechanism, then
         the principal corresponding to that identity shall be used,
         otherwise

      4) A user-configurable default identity should be used.

      and for the acceptor side of the context

      1) If there is only a single authorized principal identity capable
         of accepting security contexts for the chosen mechanism, then
         that principal shall be used, otherwise

      2) If the mechanism can determine the identity of the target
         principal by examining the context-establishment token
         processed during the accept method, and if the accepting
         application is authorized to act as that principal for the
         purpose of accepting security contexts using the chosen
         mechanism, then that principal identity shall be used,
         otherwise

      3) If the mechanism supports context acceptance by any principal,
         and if mutual authentication was not requested, any principal
         that the application is authorized to accept security contexts
         under using the chosen mechanism may be used, otherwise

      4) A user-configurable default identity shall be used.

   The purpose of the above rules is to allow security contexts to be
   established by both initiator and acceptor using the default behavior
   whenever possible.  Applications requesting default behavior are
   likely to be more portable across mechanisms and implementations than
   ones that instantiate an GSSCredential object representing a specific
   identity.







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4.9.  Contexts

   The GSSContext interface is used to represent one end of a GSS-API
   security context, storing state information appropriate to that end
   of the peer communication, including cryptographic state information.
   The instantiation of the context object is done differently by the
   initiator and the acceptor.  After the context has been instantiated,
   the initiator may choose to set various context options which will
   determine the characteristics of the desired security context.  When
   all the application desired characteristics have been set, the
   initiator will call the initSecContext method which will produce a
   token for consumption by the peer's acceptSecContext method.  It is
   the responsibility of the application to deliver the authentication
   token(s) between the peer applications for processing.  Upon
   completion of the context establishment phase, context attributes can
   be retrieved, by both the initiator and acceptor, using the accessor
   methods.  These will reflect the actual attributes of the established
   context.  At this point the context can be used by the application to
   apply cryptographic services to its data.

4.10.  Authentication tokens

   A token is a caller-opaque type that GSS-API uses to maintain
   synchronization between each end of the GSS-API security context.
   The token is a cryptographically protected octet-string, generated by
   the underlying mechanism at one end of a GSS-API security context for
   use by the peer mechanism at the other end.  Encapsulation (if
   required) within the application protocol and transfer of the token
   are the responsibility of the peer applications.

   Java GSS-API uses byte arrays to represent authentication tokens.
   Overloaded methods exist which allow the caller to supply input and
   output streams which will be used for the reading and writing of the
   token data.

4.11.  Interprocess tokens

   Certain GSS-API routines are intended to transfer data between
   processes in multi-process programs.  These routines use a caller-
   opaque octet-string, generated by the GSS-API in one process for use
   by the GSS-API in another process.  The calling application is
   responsible for transferring such tokens between processes.  Note
   that, while GSS-API implementors are encouraged to avoid placing
   sensitive information within interprocess tokens, or to
   cryptographically protect them, many implementations will be unable
   to avoid placing key material or other sensitive data within them.
   It is the application's responsibility to ensure that interprocess
   tokens are protected in transit, and transferred only to processes



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   that are trustworthy.  An interprocess token is represented using a
   byte array emitted from the export method of the GSSContext
   interface.  The receiver of the interprocess token would initialize
   an GSSContext object with this token to create a new context.  Once a
   context has been exported, the GSSContext object is invalidated and
   is no longer available.

4.12.  Error Reporting

   RFC 2743 defined the usage of major and minor status values for
   signaling of GSS-API errors.  The major code, also called GSS status
   code, is used to signal errors at the GSS-API level independent of
   the underlying mechanism(s).  The minor status value or Mechanism
   status code, is a mechanism defined error value indicating a
   mechanism specific error code.

   Java GSS-API uses exceptions implemented by the GSSException class to
   signal both minor and major error values.  Both mechanism specific
   errors and GSS-API level errors are signaled through instances of
   this class.  The usage of exceptions replaces the need for major and
   minor codes to be used within the API calls.  GSSException class also
   contains methods to obtain textual representations for both the major
   and minor values, which is equivalent to the functionality of
   gss_display_status.

4.12.1.  GSS status codes

   GSS status codes indicate errors that are independent of the
   underlying mechanism(s) used to provide the security service.  The
   errors that can be indicated via a GSS status code are generic API
   routine errors (errors that are defined in the GSS-API
   specification).  These bindings take advantage of the Java exceptions
   mechanism, thus eliminating the need for calling errors.

   A GSS status code indicates a single fatal generic API error from the
   routine that has thrown the GSSException.  Using exceptions announces
   that a fatal error has occurred during the execution of the method.
   The GSS-API operational model also allows for the signaling of
   supplementary status information from the per-message calls.  These
   need to be handled as return values since using exceptions is not
   appropriate for informatory or warning-like information.  The methods
   that are capable of producing supplementary information are the two
   per-message methods GSSContext.verifyMIC() and GSSContext.unwrap().
   These methods fill the supplementary status codes in the MessageProp
   object that was passed in.






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   GSSException object, along with providing the functionality for
   setting of the various error codes and translating them into textual
   representation, also contains the definitions of all the numeric
   error values.  The following table lists the definitions of error
   codes:

      Table: GSS Status Codes

      Name                   Value   Meaning

      BAD_MECH                 1     An unsupported mechanism
                                     was requested.

      BAD_NAME                 2     An invalid name was supplied.

      BAD_NAMETYPE             3     A supplied name was of an
                                     unsupported type.

      BAD_BINDINGS             4     Incorrect channel bindings were
                                     supplied.

      BAD_STATUS               5     An invalid status code was
                                     supplied.

      BAD_MIC                  6     A token had an invalid MIC.

      NO_CRED                  7     No credentials were supplied, or
                                     the credentials were unavailable
                                     or inaccessible.

      NO_CONTEXT               8     Invalid context has been
                                     supplied.

      DEFECTIVE_TOKEN          9     A supplied token was invalid.

      DEFECTIVE_CREDENTIAL    10     A supplied credential was
                                     invalid.

      CREDENTIALS_EXPIRED     11     The referenced credentials
                                     have expired.

      CONTEXT_EXPIRED         12     The context has expired.

      FAILURE                 13     Miscellaneous failure,
                                     unspecified at the GSS-API level.

      BAD_QOP                 14     The quality-of-protection
                                     requested could not be provided.



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      UNAUTHORIZED            15     The operation is forbidden by
                                     local security policy.

      UNAVAILABLE             16     The operation or option is
                                     unavailable.

      DUPLICATE_ELEMENT       17     The requested credential
                                     element already exists.

      NAME_NOT_MN             18     The provided name was not a
                                     mechanism name.

      OLD_TOKEN               19     The token's validity period has
                                     expired.

      DUPLICATE_TOKEN         20     The token was a duplicate of an
                                     earlier version.

   The GSS major status code of FAILURE is used to indicate that the
   underlying mechanism detected an error for which no specific GSS
   status code is defined.  The mechanism-specific status code can
   provide more details about the error.

   The different major status codes that can be contained in the
   GSSException object thrown by the methods in this specification are
   the same as the major status codes returned by the corresponding
   calls in RFC 2743 [GSSAPIv2-UPDATE].

4.12.2.  Mechanism-specific status codes

   Mechanism-specific status codes are communicated in two ways, they
   are part of any GSSException thrown from the mechanism specific layer
   to signal a fatal error, or they are part of the MessageProp object
   that the per-message calls use to signal non-fatal errors.

   A default value of 0 in either the GSSException object or the
   MessageProp object will be used to represent the absence of any
   mechanism specific status code.

4.12.3.  Supplementary status codes

   Supplementary status codes are confined to the per-message methods of
   the GSSContext interface.  Because of the informative nature of these
   errors it is not appropriate to use exceptions to signal them.
   Instead, the per-message operations of the GSSContext interface
   return these values in a MessageProp object.





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   The MessageProp class defines query methods which return boolean
   values indicating the following supplementary states:

      Table: Supplementary Status Methods

      Method Name       Meaning when "true" is returned

      isDuplicateToken   The token was a duplicate of an
                         earlier token.

      isOldToken         The token's validity period has
                         expired.

      isUnseqToken       A later token has already been
                         processed.

      isGapToken         An expected per-message token was
                         not received.

   "true" return value for any of the above methods indicates that the
   token exhibited the specified property.  The application must
   determine the appropriate course of action for these supplementary
   values.  They are not treated as errors by the GSS-API.

4.13.  Names

   A name is used to identify a person or entity.  GSS-API authenticates
   the relationship between a name and the entity claiming the name.

   Since different authentication mechanisms may employ different
   namespaces for identifying their principals, GSS-API's naming support
   is necessarily complex in multi-mechanism environments (or even in
   some single-mechanism environments where the underlying mechanism
   supports multiple namespaces).

   Two distinct conceptual representations are defined for names:

   1) A GSS-API form represented by implementations of the GSSName
      interface: A single GSSName object may contain multiple names from
      different namespaces, but all names should refer to the same
      entity.  An example of such an internal name would be the name
      returned from a call to the getName method of the GSSCredential
      interface, when applied to a credential containing credential
      elements for multiple authentication mechanisms employing
      different namespaces.  This GSSName object will contain a distinct
      name for the entity for each authentication mechanism.





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      For GSS-API implementations supporting multiple namespaces,
      GSSName implementations must contain sufficient information to
      determine the namespace to which each primitive name belongs.

   2) Mechanism-specific contiguous byte array and string forms:
      Different GSSName initialization methods are provided to handle
      both byte array and string formats and to accommodate various
      calling applications and name types.  These formats are capable of
      containing only a single name (from a single namespace).
      Contiguous string names are always accompanied by an object
      identifier specifying the namespace to which the name belongs, and
      their format is dependent on the authentication mechanism that
      employs that name.  The string name forms are assumed to be
      printable, and may therefore be used by GSS-API applications for
      communication with their users.  The byte array name formats are
      assumed to be in non-printable formats (e.g.  the byte array
      returned from the export method of the GSSName interface).

   A GSSName object can be converted to a contiguous representation by
   using the toString method.  This will guarantee that the name will be
   converted to a printable format.  Different initialization methods in
   the GSSName interface are defined allowing support for multiple
   syntaxes for each supported namespace, and allowing users the freedom
   to choose a preferred name representation.  The toString method
   should use an implementation-chosen printable syntax for each
   supported name-type.  To obtain the printable name type,
   getStringNameType method can be used.

   There is no guarantee that calling the toString method on the GSSName
   interface will produce the same string form as the original imported
   string name.  Furthermore, it is possible that the name was not even
   constructed from a string representation.  The same applies to name-
   space identifiers which may not necessarily survive unchanged after a
   journey through the internal name-form.  An example of this might be
   a mechanism that authenticates X.500 names, but provides an
   algorithmic mapping of Internet DNS names into X.500.  That
   mechanism's implementation of GSSName might, when presented with a
   DNS name, generate an internal name that contained both the original
   DNS name and the equivalent X.500 name.  Alternatively, it might only
   store the X.500 name.  In the latter case, the toString method of
   GSSName would most likely generate a printable X.500 name, rather
   than the original DNS name.

   The context acceptor can obtain a GSSName object representing the
   entity performing the context initiation (through the usage of
   getSrcName method).  Since this name has been authenticated by a
   single mechanism, it contains only a single name (even if the
   internal name presented by the context initiator to the GSSContext



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   object had multiple components).  Such names are termed internal
   mechanism names, or "MN"s and the names emitted by GSSContext
   interface in the getSrcName and getTargName are always of this type.
   Since some applications may require MNs without wanting to incur the
   overhead of an authentication operation, creation methods are
   provided that take not only the name buffer and name type, but also
   the mechanism oid for which this name should be created.  When
   dealing with an existing GSSName object, the canonicalize method may
   be invoked to convert a general internal name into an MN.

   GSSName objects can be compared using their equal method, which
   returns "true" if the two names being compared refer to the same
   entity.  This is the preferred way to perform name comparisons
   instead of using the printable names that a given GSS-API
   implementation may support.  Since GSS-API assumes that all primitive
   names contained within a given internal name refer to the same
   entity, equal can return "true" if the two names have at least one
   primitive name in common.  If the implementation embodies knowledge
   of equivalence relationships between names taken from different
   namespaces, this knowledge may also allow successful comparisons of
   internal names containing no overlapping primitive elements.

   When used in large access control lists, the overhead of creating an
   GSSName object on each name and invoking the equal method on each
   name from the ACL may be prohibitive.  As an alternative way of
   supporting this case, GSS-API defines a special form of the
   contiguous byte array name which may be compared directly (byte by
   byte).  Contiguous names suitable for comparison are generated by the
   export method.  Exported names may be re-imported by using the byte
   array constructor and specifying the NT_EXPORT_NAME as the name type
   object identifier.  The resulting GSSName name will also be a MN.
   The GSSName interface defines public static Oid objects representing
   the standard name types.  Structurally, an exported name object
   consists of a header containing an OID identifying the mechanism that
   authenticated the name, and a trailer containing the name itself,
   where the syntax of the trailer is defined by the individual
   mechanism specification.  Detailed description of the format is
   specified in the language-independent GSS-API specification
   [GSSAPIv2-UPDATE].

   Note that the results obtained by using the equals method will in
   general be different from those obtained by invoking canonicalize and
   export, and then comparing the byte array output.  The first series
   of operation determines whether two (unauthenticated) names identify
   the same principal; the second whether a particular mechanism would
   authenticate them as the same principal.  These two operations will
   in general give the same results only for MNs.




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   It is important to note that the above are guidelines as how GSSName
   implementations should behave, and are not intended to be specific
   requirements of how names objects must be implemented.  The mechanism
   designers are free to decide on the details of their implementations
   of the GSSName interface as long as the behavior satisfies the above
   guidelines.

4.14.  Channel Bindings

   GSS-API supports the use of user-specified tags to identify a given
   context to the peer application.  These tags are intended to be used
   to identify the particular communications channel that carries the
   context.  Channel bindings are communicated to the GSS-API using the
   ChannelBinding object.  The application may use byte arrays to
   specify the application data to be used in the channel binding as
   well as using instances of the InetAddress.  The InetAddress for the
   initiator and/or acceptor can be used within an instance of a
   ChannelBinding.  ChannelBinding can be set for the GSSContext object
   using the setChannelBinding method before the first call to init or
   accept has been performed.  Unless the setChannelBinding method has
   been used to set the ChannelBinding for a GSSContext object, "null"
   ChannelBinding will be assumed.  InetAddress is currently the only
   address type defined within the Java platform and as such, it is the
   only one supported within the ChannelBinding class.  Applications
   that use other types of addresses can include them as part of the
   application specific data.

   Conceptually, the GSS-API concatenates the initiator and acceptor
   address information, and the application supplied byte array to form
   an octet string.  The mechanism calculates a MIC over this octet
   string and binds the MIC to the context establishment token emitted
   by init method of the GSSContext interface.  The same bindings are
   set by the context acceptor for its GSSContext object and during
   processing of the accept method a MIC is calculated in the same way.
   The calculated MIC is compared with that found in the token, and if
   the MICs differ, accept will throw a GSSException with the  major
   code set to BAD_BINDINGS, and the context will not be established.
   Some mechanisms may include the actual channel binding data in the
   token (rather than just a MIC); applications should therefore not use
   confidential data as channel-binding components.

   Individual mechanisms may impose additional constraints on addresses
   that may appear in channel bindings.  For example, a mechanism may
   verify that the initiator address field of the channel binding
   contains the correct network address of the host system.  Portable
   applications should therefore ensure that they either provide correct
   information for the address fields, or omit setting of the addressing
   information.



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4.15.  Stream Objects

   The context object provides overloaded methods which use input and
   output streams as the means to convey authentication and per-message
   GSS-API tokens.  It is important to note that the streams are
   expected to contain the usual GSS-API tokens which would otherwise be
   handled through the usage of byte arrays.  The tokens are expected to
   have a definite start and an end.  The callers are responsible for
   ensuring that the supplied streams will not block, or expect to block
   until a full token is processed by the GSS-API method.  Only a single
   GSS-API token will be processed per invocation of the stream based
   method.

   The usage of streams allows the callers to have control and
   management of the supplied buffers.  Because streams are non-
   primitive objects, the callers can make the streams as complicated or
   as simple as desired simply by using the streams defined in the
   java.io package or creating their own through the use of inheritance.
   This will allow for the application's greatest flexibility.

4.16.  Optional Parameters

   Whenever the application wishes to omit an optional parameter the
   "null" value shall be used.  The detailed method descriptions
   indicate which parameters are optional.  Methods overloading has also
   been used as a technique to indicate default parameters.

5.  Introduction to GSS-API Classes and Interfaces

   This section presents a brief description of the classes and
   interfaces that constitute the GSS-API.  The implementations of these
   are obtained from the CLASSPATH defined by the application.  If Java
   GSS becomes part of the standard Java API's then these classes will
   be available by default on all systems as part of the JRE's system
   classes.

   This section also shows the corresponding RFC 2743 functionality
   implemented by each of the classes.  Detailed description of these
   classes and their methods is presented in section 6.

5.1.  GSSManager class

   This abstract class serves as a factory to instantiate
   implementations of the GSS-API interfaces and also provides methods
   to make queries about underlying security mechanisms.






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   A default implementation can be obtained using the static method
   getInstance(). Applications that desire to provide their own
   implementation of the GSSManager class can simply extend the abstract
   class themselves.

   This class contains equivalents of the following RFC 2743 routines:

   gss_import_name              Create an internal name from   6.1.9-
                                the supplied information.      6.1.12

   gss_acquire_cred             Acquire credential             6.1.13-
                                for use.                       6.1.15

   gss_import_sec_context       Create a previously exported   6.1.18
                                context.

   gss_indicate_mechs           List the mechanisms            6.1.6
                                supported by this GSS-API
                                implementation.

   gss_inquire_mechs_for_name   List the mechanisms            6.1.8
                                supporting the
                                specified name type.

   gss_inquire_names_for_mech   List the name types            6.1.7
                                supported by the
                                specified mechanism.

5.2.  GSSName interface

   GSS-API names are represented in the Java bindings through the
   GSSName interface.  Different name formats and their definitions are
   identified with universal Object Identifiers (oids).  The format of
   the names can be derived based on the unique oid of each name type.
   The following GSS-API routines are provided by the GSSName interface:

   RFC 2743 Routine                 Function               Section(s)


   gss_display_name        Covert internal name             6.2.7
                           representation to text format.

   gss_compare_name        Compare two internal names.      6.2.3, 6.2.4

   gss_release_name        Release resources associated     N/A
                           with the internal name.





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   gss_canonicalize_name   Convert an internal name to a    6.1.11,
                           mechanism name.

   gss_export_name         Convert a mechanism name to      6.2.6
                           export format.

   gss_duplicate_name      Create a copy of the internal    N/A
                           name.

   The gss_release_name call is not provided as Java does its own
   garbage collection. The gss_duplicate_name call is also redundant;
   the GSSName interface has no mutator methods that can change the
   state of the object so it is safe for sharing.

5.3.  GSSCredential interface

   The GSSCredential interface is responsible for the encapsulation of
   GSS-API credentials.  Credentials identify a single entity and
   provide the necessary cryptographic information to enable the
   creation of a context on behalf of that entity.  A single credential
   may contain multiple mechanism specific credentials, each referred to
   as a credential element.  The GSSCredential interface provides the
   functionality of the following GSS-API routines:

   RFC 2743 Routine               Function                Section(s)

   gss_add_cred               Constructs credentials        6.3.12
                              incrementally.

   gss_inquire_cred           Obtain information about   6.3.4,6.3.5
                              credential.

   gss_inquire_cred_by_mech   Obtain per-mechanism       6.3.5-6.3.10
                              information about
                              a credential.

   gss_release_cred           Disposes of credentials       6.3.3
                              after use.

5.4.  GSSContext interface

   This interface encapsulates the functionality of context-level calls
   required for security context establishment and management between
   peers as well as the per-message services offered to applications.  A
   context is established between a pair of peers and allows the usage
   of security services on a per-message basis on application data.  It





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   is created over a single security mechanism.  The GSSContext
   interface provides the functionality of the following GSS-API
   routines:

   RFC 2743 Routine                 Function                Section(s)

   gss_init_sec_context     Initiate the creation of a       6.4.3,
                            security context with a peer.    6.4.4

   gss_accept_sec_context   Accept a security context        6.4.5,
                            initiated by a peer.             6.4.6

   gss_delete_sec_context   Destroy a security context.      6.4.8

   gss_context_time         Obtain remaining context         6.4.37
                            time.

   gss_inquire_context      Obtain context                   6.4.29 to
                            characteristics.                 6.3.42

   gss_wrap_size_limit      Determine token-size limit       6.4.9
                            for gss_wrap.

   gss_export_sec_context   Transfer security context        6.4.18
                            to another process.


   gss_get_mic              Calculate a cryptographic        6.4.14,
                            Message Integrity Code (MIC)     6.4.15
                            for a message.

   gss_verify_mic           Verify integrity on a received   6.4.16,
                            message.                         6.4.17

   gss_wrap                 Attach a MIC to a message and    6.4.10,
                            optionally encrypt the message   6.4.11
                            content.

   gss_unwrap               Obtain a previously wrapped      6.4.12,
                            application message verifying    6.4.13
                            its integrity and optionally
                            decrypting it.

   The functionality offered by the gss_process_context_token routine
   has not been included in the Java bindings specification.  The
   corresponding functionality of gss_delete_sec_context has also been
   modified to not return any peer tokens.  This has been proposed in




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   accordance to the recommendations stated in RFC 2743.  GSSContext
   does offer the functionality of destroying the locally-stored context
   information.

5.5.  MessageProp class

   This helper class is used in the per-message operations on the
   context.  An instance of this class is created by the application and
   then passed into the per-message calls.  In some cases, the
   application conveys information to the GSS-API implementation through
   this object and in other cases the GSS-API returns information to the
   application by setting it in this object.  See the description of the
   per-message operations wrap, unwrap, getMIC, and verifyMIC in the
   GSSContext interfaces for details.

5.6.  GSSException class

   Exceptions are used in the Java bindings to signal fatal errors to
   the calling applications.  This replaces the major and minor codes
   used in the C-bindings specification as a method of signaling
   failures.  The GSSException class handles both minor and major codes,
   as well as their translation into textual representation.  All GSS-
   API methods are declared as throwing this exception.

   RFC 2743 Routine           Function              Section

   gss_display_status   Retrieve textual          6.8.5, 6.8.6,
                        representation of error   6.8.8, 6.8.9
                        codes.

5.7.  Oid class

   This utility class is used to represent Universal Object Identifiers
   and their associated operations.  GSS-API uses object identifiers to
   distinguish between security mechanisms and name types.  This class,
   aside from being used whenever an object identifier is needed,
   implements the following GSS-API functionality:

   RFC 2743 Routine                  Function              Section

   gss_test_oid_set_member   Determine if the specified oid   6.7.5
                             is part of a set of oids.









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5.8.  ChannelBinding class

   An instance of this class is used to specify channel binding
   information to the GSSContext object before the start of a security
   context establishment.  The application may use a byte array to
   specify application data to be used in the channel binding as well as
   use instances of the InetAddress.  InetAddress is currently the only
   address type defined within the Java platform and as such, it is the
   only one supported within the ChannelBinding class. Applications that
   use other types of addresses can include them as part of the
   application data.

6.  Detailed GSS-API Class Description

   This section lists a detailed description of all the public methods
   that each of the GSS-API classes and interfaces must provide.

6.1.  public abstract class GSSManager

   The GSSManager class is an abstract class that serves as a factory
   for three GSS interfaces: GSSName, GSSCredential, and GSSContext. It
   also provides methods for applications to determine what mechanisms
   are available from the GSS implementation and what nametypes these
   mechanisms support. An instance of the default GSSManager subclass
   may be obtained through the static method getInstance(), but
   applications are free to instantiate other subclasses of GSSManager.

   All but one method in this class are declared abstract. This means
   that subclasses have to provide the complete implementation for those
   methods. The only exception to this is the static method
   getInstance() which will have platform specific code to return an
   instance of the default subclass.

   Platform providers of GSS are required not to add any constructors to
   this class, private, public, or protected. This will ensure that all
   subclasses invoke only the default constructor provided to the base
   class by the compiler.

   A subclass extending the GSSManager abstract class may be implemented
   as a modular provider based layer that utilizes some well known
   service provider specification. The GSSManager API provides the
   application with methods to set provider preferences on such an
   implementation. These methods also allow the implementation to throw
   a well-defined exception in case provider based configuration is not
   supported. Applications that expect to be portable should be aware of
   this and recover cleanly by catching the exception.





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   It is envisioned that there will be three most common ways in which
   providers will be used:

      1) The application does not care about what provider is used (the
         default case).

      2) The application wants a particular provider to be used
         preferentially, either for a particular mechanism or all the
         time, irrespective of mechanism.

      3) The application wants to use the locally configured providers
         as far as possible but if support is missing for one or more
         mechanisms then it wants to fall back on its own provider.

   The GSSManager class has two methods that enable these modes of
   usage:  addProviderAtFront() and addProviderAtEnd(). These methods
   have the effect of creating an ordered list of <provider, oid> pairs
   where each pair indicates a preference of provider for a given oid.

   The use of these methods does not require any knowledge of whatever
   service provider specification the GSSManager subclass follows. It is
   hoped that these methods will serve the needs of most applications.
   Additional methods may be added to an extended GSSManager that could
   be part of a service provider specification that is standardized
   later.

6.1.1.  Example Code

   GSSManager mgr = GSSManager.getInstance();

   // What mechs are available to us?
   Oid[] supportedMechs = mgr.getMechs();

   // Set a preference for the provider to be used when support is needed
   // for the mechanisms "1.2.840.113554.1.2.2" and "1.3.6.1.5.5.1.1".

   Oid krb = new Oid("1.2.840.113554.1.2.2");
   Oid spkm1 = new Oid("1.3.6.1.5.5.1.1");

   Provider p = (Provider) (new com.foo.security.Provider());

   mgr.addProviderAtFront(p, krb);
   mgr.addProviderAtFront(p, spkm1);

   // What name types does this spkm implementation support?
   Oid[] nameTypes = mgr.getNamesForMech(spkm1);





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6.1.2.  getInstance

   public static GSSManager getInstance()

   Returns the default GSSManager implementation.

6.1.3.  getMechs

   public abstract Oid[] getMechs()

   Returns an array of Oid objects indicating mechanisms available to
   GSS-API callers.  A "null" value is returned when no mechanism are
   available (an example of this would be when mechanism are dynamically
   configured, and currently no mechanisms are installed).

6.1.4.  getNamesForMech

   public abstract  Oid[] getNamesForMech(Oid mech)
                          throws GSSException

   Returns name type Oid's supported by the specified mechanism.

   Parameters:

      mech      The Oid object for the mechanism to query.

6.1.5.  getMechsForName

   public abstract  Oid[] getMechsForName(Oid nameType)

   Returns an array of Oid objects corresponding to the mechanisms that
   support the specific name type.  "null" is returned when no
   mechanisms are found to support the specified name type.

   Parameters:

      nameType  The Oid object for the name type.

6.1.6.  createName

   public abstract GSSName createName(String nameStr, Oid nameType)
                   throws GSSException

   Factory method to convert a contiguous string name from the specified
   namespace to a GSSName object.  In general, the GSSName object
   created will not be an MN; two examples that are exceptions to this
   are when the namespace type parameter indicates NT_EXPORT_NAME or
   when the GSS-API implementation is not multi-mechanism.



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   Parameters:

      nameStr   The string representing a printable form of the name
                to create.

      nameType  The Oid specifying the namespace of the printable name
                supplied. Note that nameType serves to describe and
                qualify the interpretation of the input nameStr, it
                does not necessarily imply a type for the output
                GSSName implementation. "null" value can be used to
                specify that a mechanism specific default printable
                syntax should be assumed by each mechanism that
                examines nameStr.

6.1.7.  createName

   public abstract GSSName createName(byte name[], Oid nameType)
                   throws GSSException

   Factory method to convert a contiguous byte array containing a name
   from the specified namespace to a GSSName object.  In general, the
   GSSName object created will not be an MN; two examples that are
   exceptions to this are when the namespace type parameter indicates
   NT_EXPORT_NAME or when the GSS-API implementation is not multi-
   mechanism.

   Parameters:

      name      The byte array containing the name to create.

      nameType  The Oid specifying the namespace of the name supplied
                in the byte array.  Note that nameType serves to
                describe and qualify the interpretation of the input
                name byte array, it does not necessarily imply a type
                for the output GSSName implementation. "null" value
                can be used to specify that a mechanism specific
                default syntax should be assumed by each mechanism
                that examines the byte array.













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6.1.8.  createName

   public abstract GSSName createName(String nameStr, Oid nameType,
                   Oid mech) throws GSSException

   Factory method to convert a contiguous string name from the specified
   namespace to an GSSName object that is a mechanism name (MN).  In
   other words, this method is a utility that does the equivalent of two
   steps: the createName described in 6.1.7 and then also the
   GSSName.canonicalize() described in 6.2.5.

   Parameters:

      nameStr   The string representing a printable form of the name
                to create.

      nameType  The Oid specifying the namespace of the printable name
                supplied.  Note that nameType serves to describe and
                qualify the interpretation of the input nameStr, it
                does not necessarily imply a type for the output
                GSSName implementation. "null" value can be used to
                specify that a mechanism specific default printable
                syntax should be assumed when the mechanism examines
                nameStr.

      mech      Oid specifying the mechanism for which this name
                should be created.

6.1.9.  createName

   public abstract createName(byte name[], Oid nameType, Oid mech)
                   throws GSSException

   Factory method to convert a contiguous byte array containing a name
   from the specified namespace to a GSSName object that is an MN.  In
   other words, this method is a utility that does the equivalent of two
   steps: the createName described in 6.1.8 and then also the
   GSSName.canonicalize() described in 6.2.5.

   Parameters:

      name      The byte array representing the name to create.

      nameType  The Oid specifying the namespace of the name supplied
                in the byte array.  Note that nameType serves to
                describe and qualify the interpretation of the input
                name byte array, it does not necessarily imply a type
                for the output GSSName implementation. "null" value



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                can be used to specify that a mechanism specific
                default syntax should be assumed by each mechanism
                that examines the byte array.

      mech      Oid specifying the mechanism for which this name
                should be created.

6.1.10.  createCredential

   public abstract GSSCredential createCredential (int usage)
                   throws GSSException

   Factory method for acquiring default credentials.  This will cause
   the GSS-API to use system specific defaults for the set of
   mechanisms, name, and a DEFAULT lifetime.

   Parameters:

      usage     The intended usage for this credential object.  The
                value of this parameter must be one of:
                GSSCredential.ACCEPT_AND_INITIATE,
                GSSCredential.ACCEPT_ONLY, GSSCredential.INITIATE_ONLY

6.1.11.  createCredential

   public abstract GSSCredential createCredential (GSSName aName,
                   int lifetime, Oid mech, int usage)
                   throws GSSException

   Factory method for acquiring a single mechanism credential.

   Parameters:

      aName     Name of the principal for whom this credential is to
                be acquired.  Use "null" to specify the default
                principal.

      lifetime  The number of seconds that credentials should remain
                valid.  Use GSSCredential.INDEFINITE_LIFETIME to
                request that the credentials have the maximum
                permitted lifetime.  Use
                GSSCredential.DEFAULT_LIFETIME to request default
                credential lifetime.

      mech      The oid of the desired mechanism.  Use "(Oid) null" to
                request the default mechanism(s).





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      usage     The intended usage for this credential object.  The
                value of this parameter must be one of:
                GSSCredential.ACCEPT_AND_INITIATE,
                GSSCredential.ACCEPT_ONLY, GSSCredential.INITIATE_ONLY

6.1.12.  createCredential

   public abstract GSSCredential createCredential(GSSName aName,
                   int lifetime, Oid mechs[], int usage)
                   throws GSSException

   Factory method for acquiring credentials over a set of mechanisms.
   Acquires credentials for each of the mechanisms specified in the
   array called mechs.  To determine the list of mechanisms' for which
   the acquisition of credentials succeeded, the caller should use the
   GSSCredential.getMechs() method.

   Parameters:

      aName     Name of the principal for whom this credential is to
                be acquired.  Use "null" to specify the default
                principal.

      lifetime  The number of seconds that credentials should remain
                valid.  Use GSSCredential.INDEFINITE_LIFETIME to
                request that the credentials have the maximum
                permitted lifetime.  Use
                GSSCredential.DEFAULT_LIFETIME to request default
                credential lifetime.

      mechs     The array of mechanisms over which the credential is
                to be acquired.  Use "(Oid[]) null" for requesting a
                system specific default set of mechanisms.

      usage     The intended usage for this credential object.  The
                value of this parameter must be one of:
                GSSCredential.ACCEPT_AND_INITIATE,
                GSSCredential.ACCEPT_ONLY, GSSCredential.INITIATE_ONLY

6.1.13.  createContext

   public abstract GSSContext createContext(GSSName peer, Oid mech,
                   GSSCredential myCred, int lifetime)
                   throws GSSException

   Factory method for creating a context on the initiator's side.
   Context flags may be modified through the mutator methods prior to
   calling GSSContext.initSecContext().



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   Parameters:

      peer      Name of the target peer.

      mech      Oid of the desired mechanism.  Use "(Oid) null" to
                request default mechanism.

      myCred    Credentials of the initiator.  Use "null" to act as a
                default initiator principal.

      lifetime  The request lifetime, in seconds, for the context.
                Use GSSContext.INDEFINITE_LIFETIME and
                GSSContext.DEFAULT_LIFETIME to request indefinite or
                default context lifetime.

6.1.14.  createContext

   public abstract GSSContext createContext(GSSCredential myCred)
                   throws GSSException

   Factory method for creating a context on the acceptor' side.  The
   context's properties will be determined from the input token supplied
   to the accept method.

   Parameters:

      myCred    Credentials for the acceptor.  Use "null" to act as a
                default acceptor principal.

6.1.15.  createContext

   public abstract GSSContext createContext(byte [] interProcessToken)
                   throws GSSException

   Factory method for creating a previously exported context.  The
   context properties will be determined from the input token and can't
   be modified through the set methods.

   Parameters:

      interProcessToken
                The token previously emitted from the export method.

6.1.16.  addProviderAtFront

   public abstract void addProviderAtFront(Provider p, Oid mech)
                throws GSSException




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   This method is used to indicate to the GSSManager that the
   application would like a particular provider to be used ahead of all
   others when support is desired for the given mechanism. When a value
   of null is used instead of an Oid for the mechanism, the GSSManager
   must use the indicated provider ahead of all others no matter what
   the mechanism is. Only when the indicated provider does not support
   the needed mechanism should the GSSManager move on to a different
   provider.

   Calling this method repeatedly preserves the older settings but
   lowers them in preference thus forming an ordered list of provider
   and Oid pairs that grows at the top.

   Calling addProviderAtFront with a null Oid will remove all previous
   preferences that were set for this provider in the GSSManager
   instance. Calling addProviderAtFront with a non-null Oid will remove
   any previous preference that was set using this mechanism and this
   provider together.

   If the GSSManager implementation does not support an SPI with a
   pluggable provider architecture it should throw a GSSException with
   the status code GSSException.UNAVAILABLE to indicate that the
   operation is unavailable.

   Parameters:

      p         The provider instance that should be used whenever
                support is needed for mech.

      mech      The mechanism for which the provider is being set

6.1.16.1.  Example Code

   Suppose an application desired that the provider A always be checked
   first when any mechanism is needed, it would call:

           GSSManager mgr = GSSManager.getInstance();
           // mgr may at this point have its own pre-configured list
           // of provider preferences. The following will prepend to
           // any such list:

           mgr.addProviderAtFront(A, null);

   Now if it also desired that the mechanism of Oid m1 always be
   obtained from the provider B before the previously set A was checked,
   it would call:

           mgr.addProviderAtFront(B, m1);



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   The GSSManager would then first check with B if m1 was needed. In
   case B did not provide support for m1, the GSSManager would continue
   on to check with A.  If any mechanism m2 is needed where m2 is
   different from m1 then the GSSManager would skip B and check with A
   directly.

   Suppose at a later time the following call is made to the same
   GSSManager instance:

           mgr.addProviderAtFront(B, null)

   then the previous setting with the pair (B, m1) is subsumed by this
   and should be removed. Effectively the list of preferences now
   becomes {(B, null), (A, null),
           ... //followed by the pre-configured list.

   Please note, however, that the following call:

           mgr.addProviderAtFront(A, m3)

   does not subsume the previous setting of (A, null) and the list will
   effectively become {(A, m3), (B, null), (A, null), ...}

6.1.17.  addProviderAtEnd

   public abstract addProviderAtEnd(Provider p, Oid mech)
                   throws GSSException

   This method is used to indicate to the GSSManager that the
   application would like a particular provider to be used if no other
   provider can be found that supports the given mechanism. When a value
   of null is used instead of an Oid for the mechanism, the GSSManager
   must use the indicated provider for any mechanism.

   Calling this method repeatedly preserves the older settings but
   raises them above newer ones in preference thus forming an ordered
   list of providers and Oid pairs that grows at the bottom. Thus the
   older provider settings will be utilized first before this one is.

   If there are any previously existing preferences that conflict with
   the preference being set here, then the GSSManager should ignore this
   request.

   If the GSSManager implementation does not support an SPI with a
   pluggable provider architecture it should throw a GSSException with
   the status code GSSException.UNAVAILABLE to indicate that the
   operation is unavailable.




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   Parameters:

      p         The provider instance that should be used whenever
                support is needed for mech.

      mech      The mechanism for which the provider is being set

6.1.17.1.  Example Code

   Suppose an application desired that when a mechanism of Oid m1 is
   needed the system default providers always be checked first, and only
   when they do not support m1 should a provider A be checked. It would
   then make the call:

           GSSManager mgr = GSSManager.getInstance();

           mgr.addProviderAtEnd(A, m1);

   Now, if it also desired that for all mechanisms the provider B be
   checked after all configured providers have been checked, it would
   then call:

           mgr.addProviderAtEnd(B, null);

   Effectively the list of preferences now becomes {..., (A, m1), (B,
   null)}.

   Suppose at a later time the following call is made to the same
   GSSManager instance:

           mgr.addProviderAtEnd(B, m2)

   then the previous setting with the pair (B, null) subsumes this and
   therefore this request should be ignored. The same would happen if a
   request is made for the already existing pairs of (A, m1) or (B,
   null).

   Please note, however, that the following call:

           mgr.addProviderAtEnd(A, null)

   is not subsumed by the previous setting of (A, m1) and the list will
   effectively become {..., (A, m1), (B, null), (A, null)}








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6.2.  public interface GSSName

   This interface encapsulates a single GSS-API principal entity.
   Different name formats and their definitions are identified with
   universal Object Identifiers (Oids).  The format of the names can be
   derived based on the unique oid of its namespace type.

6.2.1.  Example Code

   Included below are code examples utilizing the GSSName interface.
   The code below creates a GSSName, converts it to a mechanism name
   (MN), performs a comparison, obtains a printable representation of
   the name, exports it and then re-imports to obtain a new GSSName.

   GSSManager mgr = GSSManager.getInstance();

   // create a host based service name
   GSSName name = mgr.createName("service@host",
                   GSSName.NT_HOSTBASED_SERVICE);

   Oid krb5 = new Oid("1.2.840.113554.1.2.2");

   GSSName mechName = name.canonicalize(krb5);

   // the above two steps are equivalent to the following
   GSSName mechName = mgr.createName("service@host",
                   GSSName.NT_HOSTBASED_SERVICE, krb5);

   // perform name comparison
   if (name.equals(mechName))
           print("Names are equals.");

   // obtain textual representation of name and its printable
   // name type
   print(mechName.toString() +
                   mechName.getStringNameType().toString());

   // export and re-import the name
   byte [] exportName = mechName.export();

   // create a new name object from the exported buffer
   GSSName newName = mgr.createName(exportName,
                   GSSName.NT_EXPORT_NAME);








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6.2.2.  Static Constants

   public static final Oid NT_HOSTBASED_SERVICE

   Oid indicating a host-based service name form.  It is used to
   represent services associated with host computers.  This name form is
   constructed using two elements, "service" and "hostname", as follows:

        service@hostname

   Values for the "service" element are registered with the IANA. It
   represents the following value: { 1(iso), 3(org), 6(dod),
   1(internet), 5(security), 6(nametypes), 2(gss-host-based-services) }

   public static final Oid NT_USER_NAME

   Name type to indicate a named user on a local system.  It represents
   the following value: { iso(1) member-body(2) United States(840)
   mit(113554) infosys(1) gssapi(2) generic(1) user_name(1) }

   public static final Oid NT_MACHINE_UID_NAME

   Name type to indicate a numeric user identifier corresponding to a
   user on a local system. (e.g. Uid).  It represents the following
   value: { iso(1) member-body(2) United States(840) mit(113554)
   infosys(1) gssapi(2) generic(1) machine_uid_name(2) }

   public static final Oid NT_STRING_UID_NAME

   Name type to indicate a string of digits representing the numeric
   user identifier of a user on a local system. It represents the
   following value:  { iso(1) member-body(2) United States(840)
   mit(113554) infosys(1) gssapi(2) generic(1) string_uid_name(3) }

   public static final Oid NT_ANONYMOUS

   Name type for representing an anonymous entity. It represents the
   following value: { 1(iso), 3(org), 6(dod), 1(internet), 5(security),
   6(nametypes), 3(gss-anonymous-name) }

   public static final Oid NT_EXPORT_NAME

   Name type used to indicate an exported name produced by the export
   method. It represents the following value: { 1(iso), 3(org), 6(dod),
   1(internet), 5(security), 6(nametypes), 4(gss-api-exported-name) }






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6.2.3.  equals

   public boolean equals(GSSName another) throws GSSException

   Compares two GSSName objects to determine whether they refer to the
   same entity.  This method may throw a GSSException when the names
   cannot be compared.  If either of the names represents an anonymous
   entity, the method will return "false".

   Parameters:

      another   GSSName object to compare with.

6.2.4.  equals

   public boolean equals(Object another)

   A variation of the equals method described in 6.2.3 that is provided
   to override the Object.equals() method that the implementing class
   will inherit.  The behavior is exactly the same as that in 6.2.3
   except that no GSSException is thrown; instead, false will be
   returned in the situation where an error occurs.  (Note that the Java
   language specification requires that two objects that are equal
   according to the equals(Object) method must return the same integer
   result when the hashCode() method is called on them.)

   Parameters:

      another   GSSName object to compare with.

6.2.5.  canonicalize

   public GSSName canonicalize(Oid mech) throws GSSException

   Creates a mechanism name (MN) from an arbitrary internal name.  This
   is equivalent to using the factory methods described in 6.1.9 or
   6.1.10 that take the mechanism name as one of their parameters.

   Parameters:

      mech      The oid for the mechanism for which the canonical form
                of the name is requested.









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6.2.6.  export

   public byte[] export() throws GSSException

   Returns a canonical contiguous byte representation of a mechanism
   name (MN), suitable for direct, byte by byte comparison by
   authorization functions.  If the name is not an MN, implementations
   may throw a GSSException with the NAME_NOT_MN status code.  If an
   implementation chooses not to throw an exception, it should use some
   system specific default mechanism to canonicalize the name and then
   export it.  The format of the header of the output buffer is
   specified in RFC 2743.

6.2.7.  toString

   public String toString()

   Returns a textual representation of the GSSName object.  To retrieve
   the printed name format, which determines the syntax of the returned
   string, the getStringNameType method can be used.

6.2.8.  getStringNameType

   public Oid getStringNameType() throws GSSException

   Returns the oid representing the type of name returned through the
   toString method.  Using this oid, the syntax of the printable name
   can be determined.

6.2.9.  isAnonymous

   public boolean isAnonymous()

   Tests if this name object represents an anonymous entity.  Returns
   "true" if this is an anonymous name.

6.2.10.  isMN

   public boolean isMN()

   Tests if this name object contains only one mechanism element and is
   thus a mechanism name as defined by RFC 2743.

6.3.  public interface GSSCredential implements Cloneable

   This interface encapsulates the GSS-API credentials for an entity.  A
   credential contains all the necessary cryptographic information to
   enable the creation of a context on behalf of the entity that it



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   represents.  It may contain multiple, distinct, mechanism specific
   credential elements, each containing information for a specific
   security mechanism, but all referring to the same entity.

   A credential may be used to perform context initiation, acceptance,
   or both.

   GSS-API implementations must impose a local access-control policy on
   callers to prevent unauthorized callers from acquiring credentials to
   which they are not entitled.  GSS-API credential creation is not
   intended to provide a "login to the network" function, as such a
   function would involve the creation of new credentials rather than
   merely acquiring a handle to existing credentials.  Such functions,
   if required, should be defined in implementation-specific extensions
   to the API.

   If credential acquisition is time-consuming for a mechanism, the
   mechanism may choose to delay the actual acquisition until the
   credential is required (e.g.  by GSSContext).  Such mechanism-
   specific implementation decisions should be invisible to the calling
   application; thus the query methods immediately following the
   creation of a credential object must return valid credential data,
   and may therefore incur the overhead of a deferred credential
   acquisition.

   Applications will create a credential object passing the desired
   parameters.  The application can then use the query methods to obtain
   specific information about the instantiated credential object
   (equivalent to the gss_inquire routines).  When the credential is no
   longer needed, the application should call the dispose (equivalent to
   gss_release_cred) method to release any resources held by the
   credential object and to destroy any cryptographically sensitive
   information.

   Classes implementing this interface also implement the Cloneable
   interface. This indicates the the class will support the clone()
   method that will allow the creation of duplicate credentials.  This
   is useful when called just before the add() call to retain a copy of
   the original credential.

6.3.1.  Example Code

   This example code demonstrates the creation of a GSSCredential
   implementation for a specific entity, querying of its fields, and its
   release when it is no longer needed.






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   GSSManager mgr = GSSManager.getInstance();

   // start by creating a name object for the entity
   GSSName name = mgr.createName("userName", GSSName.NT_USER_NAME);

   // now acquire credentials for the entity
   GSSCredential cred = mgr.createCredential(name,
                   GSSCredential.ACCEPT_ONLY);

   // display credential information - name, remaining lifetime,
   // and the mechanisms it has been acquired over
   print(cred.getName().toString());
   print(cred.getRemainingLifetime());

   Oid [] mechs = cred.getMechs();
   if (mechs != null) {
           for (int i = 0; i < mechs.length; i++)
                   print(mechs[i].toString());
   }

   // release system resources held by the credential
   cred.dispose();

6.3.2.  Static Constants

   public static final int INITIATE_AND_ACCEPT

   Credential usage flag requesting that it be able to be used for both
   context initiation and acceptance.

   public static final int INITIATE_ONLY

   Credential usage flag requesting that it be able to be used for
   context initiation only.

   public static final int ACCEPT_ONLY

   Credential usage flag requesting that it be able to be used for
   context acceptance only.

   public static final int DEFAULT_LIFETIME

   A lifetime constant representing the default credential lifetime.

   This value must be set to 0.

   public static final int INDEFINITE_LIFETIME




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   A lifetime constant representing indefinite credential lifetime.
   This value must be set to the maximum integer value in Java -
   Integer.MAX_VALUE.

6.3.3.  dispose

   public void dispose() throws GSSException

   Releases any sensitive information that the GSSCredential object may
   be containing.  Applications should call this method as soon as the
   credential is no longer needed to minimize the time any sensitive
   information is maintained.

6.3.4.  getName

   public GSSName getName() throws GSSException

   Retrieves the name of the entity that the credential asserts.

6.3.5.  getName

   public GSSName getName(Oid mechOID) throws GSSException

   Retrieves a mechanism name of the entity that the credential asserts.
   Equivalent to calling canonicalize() on the name returned by 7.3.3.

   Parameters:

      mechOID   The mechanism for which information should be
                returned.

6.3.6.  getRemainingLifetime

   public int getRemainingLifetime() throws GSSException

   Returns the remaining lifetime in seconds for a credential.  The
   remaining lifetime is the minimum lifetime for any of the underlying
   credential mechanisms.  A return value of
   GSSCredential.INDEFINITE_LIFETIME indicates that the credential does
   not expire.  A return value of 0 indicates that the credential is
   already expired.










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6.3.7.  getRemainingInitLifetime

   public int getRemainingInitLifetime(Oid mech) throws GSSException

   Returns the remaining lifetime is seconds for the credential to
   remain capable of initiating security contexts under the specified
   mechanism.  A return value of GSSCredential.INDEFINITE_LIFETIME
   indicates that the credential does not expire for context initiation.
   A return value of 0 indicates that the credential is already expired.

   Parameters:

      mechOID   The mechanism for which information should be
                returned.

6.3.8.  getRemainingAcceptLifetime

   public int getRemainingAcceptLifetime(Oid mech) throws GSSException

   Returns the remaining lifetime is seconds for the credential to
   remain capable of accepting security contexts under the specified
   mechanism.  A return value of GSSCredential.INDEFINITE_LIFETIME
   indicates that the credential does not expire for context acceptance.
   A return value of 0 indicates that the credential is already expired.

   Parameters:

      mechOID   The mechanism for which information should be
                returned.

6.3.9.  getUsage

   public int getUsage() throws GSSException

   Returns the credential usage flag.  The return value will be one of
   GSSCredential.INITIATE_ONLY, GSSCredential.ACCEPT_ONLY, or
   GSSCredential.INITIATE_AND_ACCEPT.

6.3.10.  getUsage

   public int getUsage(Oid mechOID) throws GSSException

   Returns the credential usage flag for the specified credential
   mechanism.  The return value will be one of
   GSSCredential.INITIATE_ONLY, GSSCredential.ACCEPT_ONLY, or
   GSSCredential.INITIATE_AND_ACCEPT.





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   Parameters:

      mechOID   The mechanism for which information should be
                returned.

6.3.11.  getMechs

   public Oid[] getMechs() throws GSSException

   Returns an array of mechanisms supported by this credential.

6.3.12.  add

   public void add(GSSName aName, int initLifetime, int acceptLifetime,
                   Oid mech, int usage) throws GSSException

   Adds a mechanism specific credential-element to an existing
   credential.  This method allows the construction of credentials one
   mechanism at a time.

   This routine is envisioned to be used mainly by context acceptors
   during the creation of acceptance credentials which are to be used
   with a variety of clients using different security mechanisms.

   This routine adds the new credential element "in-place".  To add the
   element in a new credential, first call clone() to obtain a copy of
   this credential, then call its add() method.

   Parameters:

      aName     Name of the principal for whom this credential is to
                be acquired. Use "null" to specify the default
                principal.

      initLifetime
                The number of seconds that credentials should remain
                valid for initiating of security contexts.  Use
                GSSCredential.INDEFINITE_LIFETIME to request that the
                credentials have the maximum permitted lifetime. Use
                GSSCredential.DEFAULT_LIFETIME to request default
                credential lifetime.

      acceptLifetime
                The number of seconds that credentials should remain
                valid for accepting of security contexts.  Use
                GSSCredential.INDEFINITE_LIFETIME to request that the





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                credentials have the maximum permitted lifetime.  Use
                GSSCredential.DEFAULT_LIFETIME to request default
                credential lifetime.

      mech      The mechanisms over which the credential is to be
                acquired.

      usage     The intended usage for this credential object. The
                value of this parameter must be one of:
                GSSCredential.ACCEPT_AND_INITIATE,
                GSSCredential.ACCEPT_ONLY, GSSCredential.INITIATE_ONLY

6.3.13.  equals

   public boolean equals(Object another)

   Tests if this GSSCredential refers to the same entity as the supplied
   object.  The two credentials must be acquired over the same
   mechanisms and must refer to the same principal.  Returns "true" if
   the two GSSCredentials refer to the same entity; "false" otherwise.
   (Note that the Java language specification requires that two objects
   that are equal according to the equals(Object) method must return the
   same integer result when the hashCode() method is called on them.)

   Parameters:

      another   Another GSSCredential object for comparison.

6.4.  public interface GSSContext

   This interface encapsulates the GSS-API security context and provides
   the security services (wrap, unwrap, getMIC, verifyMIC) that are
   available over the context.  Security contexts are established
   between peers using locally acquired credentials.  Multiple contexts
   may exist simultaneously between a pair of peers, using the same or
   different set of credentials.  GSS-API functions in a manner
   independent of the underlying transport protocol and depends on its
   calling application to transport its tokens between peers.

   Before the context establishment phase is initiated, the context
   initiator may request specific characteristics desired of the
   established context.  These can be set using the set methods.  After
   the context is established, the caller can check the actual
   characteristic and services offered by the context using the query
   methods.






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   The context establishment phase begins with the first call to the
   init method by the context initiator.  During this phase the
   initSecContext and acceptSecContext methods will produce GSS-API
   authentication tokens which the calling application needs to send to
   its peer.  If an error occurs at any point, an exception will get
   thrown and the code will start executing in a catch block.  If not,
   the normal flow of code continues and the application can make a call
   to the isEstablished() method.  If this method returns false it
   indicates that a token is needed from its peer in order to continue
   the context establishment phase.  A return value of true signals that
   the local end of the context is established.  This may still require
   that a token be sent to the peer, if one is produced by GSS-API.
   During the context establishment phase, the isProtReady() method may
   be called to determine if the context can be used for the per-message
   operations.  This allows applications to use per-message operations
   on contexts which aren't fully established.

   After the context has been established or the isProtReady() method
   returns "true", the query routines can be invoked to determine the
   actual characteristics and services of the established context.  The
   application can also start using the per-message methods of wrap and
   getMIC to obtain cryptographic operations on application supplied
   data.

   When the context is no longer needed, the application should call
   dispose to release any system resources the context may be using.

6.4.1.  Example Code

   The example code presented below demonstrates the usage of the
   GSSContext interface for the initiating peer.  Different operations
   on the GSSContext object are presented, including: object
   instantiation, setting of desired flags, context establishment, query
   of actual context flags, per-message operations on application data,
   and finally context deletion.

   GSSManager mgr = GSSManager.getInstance();

   // start by creating the name for a service entity
   GSSName targetName = mgr.createName("service@host",
                   GSSName.NT_HOSTBASED_SERVICE);

   // create a context using default credentials for the above entity
   // and the implementation specific default mechanism
   GSSContext context = mgr.createContext(targetName,
                   null,   /* default mechanism */
                   null,   /* default credentials */
                   GSSContext.INDEFINITE_LIFETIME);



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   // set desired context options - all others are false by default
   context.requestConf(true);
   context.requestMutualAuth(true);
   context.requestReplayDet(true);
   context.requestSequenceDet(true);

   // establish a context between peers - using byte arrays
   byte []inTok = new byte[0];

   try {
           do {
                   byte[] outTok = context.initSecContext(inTok, 0,
                                                     inTok.length);

                   // send the token if present
                   if (outTok != null)
                           sendToken(outTok);

                   // check if we should expect more tokens
                   if (context.isEstablished())
                           break;

                   // another token expected from peer
                   inTok = readToken();

           } while (true);

   } catch (GSSException e) {
           print("GSSAPI error: " + e.getMessage());
   }


   // display context information
   print("Remaining lifetime in seconds = " + context.getLifetime());
   print("Context mechanism = " + context.getMech().toString());
   print("Initiator = " + context.getSrcName().toString());
   print("Acceptor = " + context.getTargName().toString());

   if (context.getConfState())
           print("Confidentiality security service available");

   if (context.getIntegState())
           print("Integrity security service available");

   // perform wrap on an application supplied message, appMsg,
   // using QOP = 0, and requesting privacy service
   byte [] appMsg ...




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   MessageProp mProp = new MessageProp(0, true);

   byte []tok = context.wrap(appMsg, 0, appMsg.length, mProp);

   if (mProp.getPrivacy())
           print("Message protected with privacy.");

   sendToken(tok);


   // release the local-end of the context
   context.dispose();

6.4.2.  Static Constants

   public static final int DEFAULT_LIFETIME

   A lifetime constant representing the default context lifetime.  This
   value must be set to 0.

   public static final int INDEFINITE_LIFETIME

   A lifetime constant representing indefinite context lifetime.  This
   value must be set to the maximum integer value in Java -
   Integer.MAX_VALUE.

6.4.3.  initSecContext

   public byte[] initSecContext(byte inputBuf[], int offset, int len)
                   throws GSSException

   Called by the context initiator to start the context creation
   process.  This is equivalent to the stream based method except that
   the token buffers are handled as byte arrays instead of using stream
   objects.  This method may return an output token which the
   application will need to send to the peer for processing by the
   accept call.  Typically, the application would do so by calling the
   flush() method on an OutputStream that encapsulates the connection
   between the two peers.  The application can call isEstablished() to
   determine if the context establishment phase is complete for this
   peer.  A return value of "false" from isEstablished() indicates that
   more tokens are expected to be supplied to the initSecContext()
   method.  Note that it is possible that the initSecContext() method
   return a token for the peer, and isEstablished() return "true" also.
   This indicates that the token needs to be sent to the peer, but the
   local end of the context is now fully established.





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   Upon completion of the context establishment, the available context
   options may be queried through the get methods.

   Parameters:

      inputBuf  Token generated by the peer. This parameter is ignored
                on the first call.

      offset    The offset within the inputBuf where the token begins.

      len       The length of the token within the inputBuf (starting
                at the offset).

6.4.3.1.  Example Code

   // Create a new GSSContext implementation object.
   // GSSContext wrapper implements interface GSSContext.
   GSSContext context = mgr.createContext(...);


   byte []inTok = new byte[0];

   try {

           do {
                   byte[] outTok = context.initSecContext(inTok, 0,
                                           inTok.length);

                   // send the token if present
                   if (outTok != null)
                           sendToken(outTok);


                   // check if we should expect more tokens
                   if (context.isEstablished())
                           break;

                   // another token expected from peer
                   inTok = readToken();
           } while (true);

   } catch (GSSException e) {
           print("GSSAPI error: " + e.getMessage());
   }







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6.4.4.  initSecContext

   public int initSecContext(InputStream inStream,
                   OutputStream outStream) throws GSSException

   Called by the context initiator to start the context creation
   process.  This is equivalent to the byte array based method.  This
   method may write an output token to the outStream, which the
   application will need to send to the peer for processing by the
   accept call. Typically, the application would do so by calling the
   flush() method on an OutputStream that encapsulates the connection
   between the two peers.  The application can call isEstablished() to
   determine if the context establishment phase is complete for this
   peer.  A return value of "false" from isEstablished indicates that
   more tokens are expected to be supplied to the initSecContext method.
   Note that it is possible that the initSecContext() method return a
   token for the peer, and isEstablished() return "true" also.  This
   indicates that the token needs to be sent to the peer, but the local
   end of the context is now fully established.

   The GSS-API authentication tokens contain a definitive start and end.
   This method will attempt to read one of these tokens per invocation,
   and may block on the stream if only part of the token is available.

   Upon completion of the context establishment, the available context
   options may be queried through the get methods.

   Parameters:

      inStream  Contains the token generated by the peer. This
                parameter is ignored on the first call.

      outStream Output stream where the output token will be written.
                During the final stage of context establishment, there
                may be no bytes written.

6.4.4.1.  Example Code

   This sample code merely demonstrates the token exchange during the
   context establishment phase. It is expected that most Java
   applications will use custom implementations of the Input and Output
   streams that encapsulate the communication routines.  For instance, a
   simple read on the application InputStream, when called by the
   Context, might cause a token to be read from the peer, and a simple
   flush() on the application OutputStream might cause a previously
   written token to be transmitted to the peer.

   // Create a new GSSContext implementation object.



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   // GSSContext wrapper implements interface GSSContext.
   GSSContext context = mgr.createContext(...);

   // use standard java.io stream objects
   ByteArrayOutputStream os = new ByteArrayOutputStream();
   ByteArrayInputStream is = null;


   try {

           do {
                   context.initSecContext(is, os);

                   // send token if present
                   if (os.size() > 0)
                           sendToken(os);

                   // check if we should expect more tokens
                   if (context.isEstablished())
                           break;

                   // another token expected from peer
                   is = recvToken();

           } while (true);

   } catch (GSSException e) {
           print("GSSAPI error: " + e.getMessage());
   }

6.4.5.  acceptSecContext

   public byte[] acceptSecContext(byte inTok[], int offset, int len)
                   throws GSSException

   Called by the context acceptor upon receiving a token from the peer.
   This call is equivalent to the stream based method except that the
   token buffers are handled as byte arrays instead of using stream
   objects.

   This method may return an output token which the application will
   need to send to the peer for further processing by the init call.

   "null" return value indicates that no token needs to be sent to the
   peer.  The application can call isEstablished() to determine if the
   context establishment phase is complete for this peer.  A return
   value of "false" from isEstablished() indicates that more tokens are
   expected to be supplied to this method.



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   Note that it is possible that acceptSecContext() return a token for
   the peer, and isEstablished() return "true" also.  This indicates
   that the token needs to be sent to the peer, but the local end of the
   context is now fully established.

   Upon completion of the context establishment, the available context
   options may be queried through the get methods.

   Parameters:

      inTok     Token generated by the peer.

      offset    The offset within the inTok where the token begins.

      len       The length of the token within the inTok (starting at
                the offset).

6.4.5.1.  Example Code

   // acquire server credentials
   GSSCredential server = mgr.createCredential(...);

   // create acceptor GSS-API context from the default provider
   GSSContext context = mgr.createContext(server, null);

   try {
           do {
                   byte [] inTok = readToken();

                   byte []outTok = context.acceptSecContext(inTok, 0,
                                           inTok.length);

                   // possibly send token to peer
                   if (outTok != null)
                           sendToken(outTok);

                   // check if local context establishment is complete
                   if (context.isEstablished())
                           break;
           } while (true);

   } catch (GSSException e) {
           print("GSS-API error: " + e.getMessage());
   }







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6.4.6.  acceptSecContext

   public void acceptSecContext(InputStream inStream,
                   OutputStream outStream) throws GSSException

   Called by the context acceptor upon receiving a token from the peer.
   This call is equivalent to the byte array method.  It may write an
   output token to the outStream, which the application will need to
   send to the peer for processing by its initSecContext method.
   Typically, the application would do so by calling the flush() method
   on an OutputStream that encapsulates the connection between the two
   peers. The application can call isEstablished() to determine if the
   context establishment phase is complete for this peer.  A return
   value of "false" from isEstablished() indicates that more tokens are
   expected to be supplied to this method.

   Note that it is possible that acceptSecContext() return a token for
   the peer, and isEstablished() return "true" also.  This indicates
   that the token needs to be sent to the peer, but the local end of the
   context is now fully established.

   The GSS-API authentication tokens contain a definitive start and end.
   This method will attempt to read one of these tokens per invocation,
   and may block on the stream if only part of the token is available.

   Upon completion of the context establishment, the available context
   options may be queried through the get methods.

   Parameters:

      inStream  Contains the token generated by the peer.

      outStream Output stream where the output token will be written.
                During the final stage of context establishment, there
                may be no bytes written.

6.4.6.1.  Example Code

   This sample code merely demonstrates the token exchange during the
   context establishment phase. It is expected that most Java
   applications will use custom implementations of the Input and Output
   streams that encapsulate the communication routines.  For instance, a
   simple read on the application InputStream, when called by the
   Context, might cause a token to be read from the peer, and a simple
   flush() on the application OutputStream might cause a previously
   written token to be transmitted to the peer.

   // acquire server credentials



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   GSSCredential server = mgr.createCredential(...);

   // create acceptor GSS-API context from the default provider
   GSSContext context = mgr.createContext(server, null);

   // use standard java.io stream objects
   ByteArrayOutputStream os = new ByteArrayOutputStream();
   ByteArrayInputStream is = null;

   try {
           do {

                   is = recvToken();

                   context.acceptSecContext(is, os);

                   // possibly send token to peer
                   if (os.size() > 0)
                           sendToken(os);

                   // check if local context establishment is complete
                   if (context.isEstablished())
                           break;
           } while (true);

   } catch (GSSException e) {
           print("GSS-API error: " + e.getMessage());
   }

6.4.7.  isEstablished

   public boolean isEstablished()

   Used during context establishment to determine the state of the
   context.  Returns "true" if this is a fully established context on
   the caller's side and no more tokens are needed from the peer.
   Should be called after a call to initSecContext() or
   acceptSecContext() when no GSSException is thrown.

6.4.8.  dispose

   public void dispose() throws GSSException

   Releases any system resources and cryptographic information stored in
   the context object.  This will invalidate the context.






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6.4.9.  getWrapSizeLimit

   public int getWrapSizeLimit(int qop, boolean confReq,
                   int maxTokenSize) throws GSSException

   Returns the maximum message size that, if presented to the wrap
   method with the same confReq and qop parameters, will result in an
   output token containing no more than the maxTokenSize bytes.

   This call is intended for use by applications that communicate over
   protocols that impose a maximum message size.  It enables the
   application to fragment messages prior to applying protection.

   GSS-API implementations are recommended but not required to detect
   invalid QOP values when getWrapSizeLimit is called.  This routine
   guarantees only a maximum message size, not the availability of
   specific QOP values for message protection.

   Successful completion of this call does not guarantee that wrap will
   be able to protect a message of the computed length, since this
   ability may depend on the availability of system resources at the
   time that wrap is called.  However, if the implementation itself
   imposes an upper limit on the length of messages that may be
   processed by wrap, the implementation should not return a value that
   is greater than this length.

   Parameters:

      qop       Indicates the level of protection wrap will be asked
                to provide.

      confReq   Indicates if wrap will be asked to provide privacy
                service.

      maxTokenSize
                The desired maximum size of the token emitted by wrap.

6.4.10.  wrap

   public byte[] wrap(byte inBuf[], int offset, int len,
                   MessageProp msgProp) throws GSSException

   Applies per-message security services over the established security
   context.  The method will return a token with a cryptographic MIC and
   may optionally encrypt the specified inBuf.  This method is
   equivalent in functionality to its stream counterpart.  The returned
   byte array will contain both the MIC and the message.




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   The MessageProp object is instantiated by the application and used to
   specify a QOP value which selects cryptographic algorithms, and a
   privacy service to optionally encrypt the message.  The underlying
   mechanism that is used in the call may not be able to provide the
   privacy service.  It sets the actual privacy service that it does
   provide in this MessageProp object which the caller should then query
   upon return.  If the mechanism is not able to provide the requested
   QOP, it throws a GSSException with the BAD_QOP code.

   Since some application-level protocols may wish to use tokens emitted
   by wrap to provide "secure framing", implementations should support
   the wrapping of zero-length messages.

   The application will be responsible for sending the token to the
   peer.

   Parameters:

      inBuf     Application data to be protected.

      offset    The offset within the inBuf where the data begins.

      len       The length of the data within the inBuf (starting at
                the offset).

      msgProp   Instance of MessageProp that is used by the
                application to set the desired QOP and privacy state.
                Set the desired QOP to 0 to request the default QOP.
                Upon return from this method, this object will contain
                the the actual privacy state that was applied to the
                message by the underlying mechanism.

6.4.11.  wrap

   public void wrap(InputStream inStream, OutputStream outStream,
                   MessageProp msgProp) throws GSSException

   Allows to apply per-message security services over the established
   security context.  The method will produce a token with a
   cryptographic MIC and may optionally encrypt the message in inStream.
   The outStream will contain both the MIC and the message.

   The MessageProp object is instantiated by the application and used to
   specify a QOP value which selects cryptographic algorithms, and a
   privacy service to optionally encrypt the message.  The underlying
   mechanism that is used in the call may not be able to provide the
   privacy service.  It sets the actual privacy service that it does




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   provide in this MessageProp object which the caller should then query
   upon return.  If the mechanism is not able to provide the requested
   QOP, it throws a GSSException with the BAD_QOP code.

   Since some application-level protocols may wish to use tokens emitted
   by wrap to provide "secure framing", implementations should support
   the wrapping of zero-length messages.

   The application will be responsible for sending the token to the
   peer.

   Parameters:

      inStream  Input stream containing the application data to be
                protected.

      outStream The output stream to write the protected message to.
                The application is responsible for sending this to the
                other peer for processing in its unwrap method.

      msgProp   Instance of MessageProp that is used by the
                application to set the desired QOP and privacy state.
                Set the desired QOP to 0 to request the default QOP.
                Upon return from this method, this object will contain
                the the actual privacy state that was applied to the
                message by the underlying mechanism.

6.4.12.  unwrap

   public byte [] unwrap(byte[] inBuf, int offset, int len,
                   MessageProp msgProp) throws GSSException

   Used by the peer application to process tokens generated with the
   wrap call.  This call is equal in functionality to its stream
   counterpart.  The method will return the message supplied in the peer
   application to the wrap call, verifying the embedded MIC.

   The MessageProp object is instantiated by the application and is used
   by the underlying mechanism to return information to the caller such
   as the QOP, whether confidentiality was applied to the message, and
   other supplementary message state information.

   Since some application-level protocols may wish to use tokens emitted
   by wrap to provide "secure framing", implementations should support
   the wrapping and unwrapping of zero-length messages.






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   Parameters:

      inBuf     GSS-API wrap token received from peer.

      offset    The offset within the inBuf where the token begins.

      len       The length of the token within the inBuf (starting at
                the offset).

      msgProp   Upon return from the method, this object will contain
                the applied QOP, the privacy state of the message, and
                supplementary information described in 4.12.3 stating
                whether the token was a duplicate, old, out of
                sequence or arriving after a gap.

6.4.13.  unwrap

   public void unwrap(InputStream inStream, OutputStream outStream,
                   MessageProp msgProp) throws GSSException

   Used by the peer application to process tokens generated with the
   wrap call.  This call is equal in functionality to its byte array
   counterpart.  It will produce the message supplied in the peer
   application to the wrap call, verifying the embedded MIC.

   The MessageProp object is instantiated by the application and is used
   by the underlying mechanism to return information to the caller such
   as the QOP, whether confidentiality was applied to the message, and
   other supplementary message state information.

   Since some application-level protocols may wish to use tokens emitted
   by wrap to provide "secure framing", implementations should support
   the wrapping and unwrapping of zero-length messages.

   Parameters:

      inStream  Input stream containing the GSS-API wrap token
                received from the peer.

      outStream The output stream to write the application message to.

      msgProp   Upon return from the method, this object will contain
                the applied QOP, the privacy state of the message, and
                supplementary information described in 4.12.3 stating
                whether the token was a duplicate, old, out of
                sequence or arriving after a gap.





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6.4.14.  getMIC

   public byte[] getMIC(byte []inMsg, int offset, int len,
                   MessageProp msgProp) throws GSSException

   Returns a token containing a cryptographic MIC for the supplied
   message,  for transfer to the peer application.  Unlike wrap, which
   encapsulates the user message in the returned token, only the message
   MIC is returned in the output token.  This method is identical in
   functionality to its stream counterpart.

   Note that privacy can only be applied through the wrap call.

   Since some application-level protocols may wish to use tokens emitted
   by getMIC to provide "secure framing", implementations should support
   derivation of MICs from zero-length messages.

   Parameters:

      inMsg     Message to generate MIC over.

      offset    The offset within the inMsg where the token begins.

      len       The length of the token within the inMsg (starting at
                the offset).

      msgProp   Instance of MessageProp that is used by the
                application to set the desired QOP.  Set the desired
                QOP to 0 in msgProp to request the default QOP.
                Alternatively pass in "null" for msgProp to request
                default QOP.

6.4.15.  getMIC

   public void getMIC(InputStream inStream, OutputStream outStream,
                   MessageProp msgProp) throws GSSException

   Produces a token containing a cryptographic MIC for the supplied
   message, for transfer to the peer application.  Unlike wrap, which
   encapsulates the user message in the returned token, only the message
   MIC is produced in the output token.  This method is identical in
   functionality to its byte array counterpart.

   Note that privacy can only be applied through the wrap call.

   Since some application-level protocols may wish to use tokens emitted
   by getMIC to provide "secure framing", implementations should support
   derivation of MICs from zero-length messages.



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   Parameters:

      inStream  inStream  Input stream containing the message to
                generate MIC over.

      outStream outStream Output stream to write the GSS-API output
                token to.

      msgProp   Instance of MessageProp that is used by the
                application to set the desired QOP.  Set the desired
                QOP to 0 in msgProp to request the default QOP.
                Alternatively pass in "null" for msgProp to request
                default QOP.

6.4.16.  verifyMIC

   public void verifyMIC(byte []inTok, int tokOffset, int tokLen,
                   byte[] inMsg, int msgOffset, int msgLen,
                   MessageProp msgProp) throws GSSException

   Verifies the cryptographic MIC, contained in the token parameter,
   over the supplied message.  This method is equivalent in
   functionality to its stream counterpart.

   The MessageProp object is instantiated by the application and is used
   by the underlying mechanism to return information to the caller such
   as the QOP indicating the strength of protection that was applied to
   the message and other supplementary message state information.

   Since some application-level protocols may wish to use tokens emitted
   by getMIC to provide "secure framing", implementations should support
   the calculation and verification of MICs over zero-length messages.

   Parameters:

      inTok     Token generated by peer's getMIC method.

      tokOffset The offset within the inTok where the token begins.

      tokLen    The length of the token within the inTok (starting at
                the offset).

      inMsg     Application message to verify the cryptographic MIC
                over.

      msgOffset The offset within the inMsg where the message begins.





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      msgLen    The length of the message within the inMsg (starting
                at the offset).

      msgProp   Upon return from the method, this object will contain
                the applied QOP and supplementary information
                described in 4.12.3 stating whether the token was a
                duplicate, old, out of sequence or arriving after a
                gap.  The confidentiality state will be set to
                "false".

6.4.17.  verifyMIC

   public void verifyMIC(InputStream tokStream, InputStream msgStream,
                   MessageProp msgProp) throws GSSException

   Verifies the cryptographic MIC, contained in the token parameter,
   over the supplied message.  This method is equivalent in
   functionality to its byte array counterpart.

   The MessageProp object is instantiated by the application and is used
   by the underlying mechanism to return information to the caller such
   as the QOP indicating the strength of protection that was applied to
   the message and other supplementary message state information.

   Since some application-level protocols may wish to use tokens emitted
   by getMIC to provide "secure framing", implementations should support
   the calculation and verification of MICs over zero-length messages.

   Parameters:

      tokStream Input stream containing the token generated by peer's
                getMIC method.

      msgStream Input stream containing the application message to
                verify the cryptographic MIC over.

      msgProp   Upon return from the method, this object will contain
                the applied QOP and supplementary information
                described in 4.12.3 stating whether the token was a
                duplicate, old, out of sequence or arriving after a
                gap.  The confidentiality state will be set to
                "false".









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6.4.18.  export

   public byte [] export() throws GSSException

   Provided to support the sharing of work between multiple processes.
   This routine will typically be used by the context-acceptor, in an
   application where a single process receives incoming connection
   requests and accepts security contexts over them, then passes the
   established context to one or more other processes for message
   exchange.

   This method deactivates the security context and creates an
   interprocess token which, when passed to the byte array constructor
   of the GSSContext interface in another process, will re-activate the
   context in the second process.  Only a single instantiation of a
   given context may be active at any one time; a subsequent attempt by
   a context exporter to access the exported security context will fail.

   The implementation may constrain the set of processes by which the
   interprocess token may be imported, either as a function of local
   security policy, or as a result of implementation decisions.  For
   example, some implementations may constrain contexts to be passed
   only between processes that run under the same account, or which are
   part of the same process group.

   The interprocess token may contain security-sensitive information
   (for example cryptographic keys).  While mechanisms are encouraged to
   either avoid placing such sensitive information within interprocess
   tokens, or to encrypt the token before returning it to the
   application, in a typical GSS-API implementation this may not be
   possible.  Thus the application must take care to protect the
   interprocess token, and ensure that any process to which the token is
   transferred is trustworthy.

6.4.19.  requestMutualAuth

   public void requestMutualAuth(boolean state) throws GSSException

   Sets the request state of the mutual authentication flag for the
   context.  This method is only valid before the context creation
   process begins and only for the initiator.

   Parameters:

      state     Boolean representing if mutual authentication should
                be requested during context establishment.





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6.4.20.  requestReplayDet

   public void requestReplayDet(boolean state) throws GSSException

   Sets the request state of the replay detection service for the
   context.  This method is only valid before the context creation
   process begins and only for the initiator.

   Parameters:

      state     Boolean representing if replay detection is desired
                over the established context.

6.4.21.  requestSequenceDet

   public void requestSequenceDet(boolean state) throws GSSException

   Sets the request state for the sequence checking service of the
   context.  This method is only valid before the context creation
   process begins and only for the initiator.

   Parameters:

      state     Boolean representing if sequence detection is desired
                over the established context.

6.4.22.  requestCredDeleg

   public void requestCredDeleg(boolean state) throws GSSException

   Sets the request state for the credential delegation flag for the
   context.  This method is only valid before the context creation
   process begins and only for the initiator.

   Parameters:

      state     Boolean representing if credential delegation is
                desired.

6.4.23.  requestAnonymity

   public void requestAnonymity(boolean state) throws GSSException

   Requests anonymous support over the context.  This method is only
   valid before the context creation process begins and only for the
   initiator.





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   Parameters:

      state     Boolean representing if anonymity support is
                requested.

6.4.24.  requestConf

   public void requestConf(boolean state) throws GSSException

   Requests that confidentiality service be available over the context.
   This method is only valid before the context creation process begins
   and only for the initiator.

   Parameters:

      state     Boolean indicating if confidentiality services are to
                be requested for the context.

6.4.25.  requestInteg

   public void requestInteg(boolean state) throws GSSException

   Requests that integrity services be available over the context.  This
   method is only valid before the context creation process begins and
   only for the initiator.

   Parameters:

      state     Boolean indicating if integrity services are to be
                requested for the context.

6.4.26.  requestLifetime

   public void requestLifetime(int lifetime) throws GSSException

   Sets the desired lifetime for the context in seconds.  This method is
   only valid before the context creation process begins and only for
   the initiator. Use GSSContext.INDEFINITE_LIFETIME and
   GSSContext.DEFAULT_LIFETIME to request indefinite or default context
   lifetime.

   Parameters:

      lifetime  The desired context lifetime in seconds.







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6.4.27.  setChannelBinding

   public void setChannelBinding(ChannelBinding cb) throws GSSException

   Sets the channel bindings to be used during context establishment.
   This method is only valid before the context creation process begins.

   Parameters:

      cb        Channel bindings to be used.

6.4.28.  getCredDelegState

   public boolean getCredDelegState()

   Returns the state of the delegated credentials for the context.  When
   issued before context establishment is completed or when the
   isProtReady method returns "false", it returns the desired state,
   otherwise it will indicate the actual state over the established
   context.

6.4.29.  getMutualAuthState

   public boolean getMutualAuthState()

   Returns the state of the mutual authentication option for the
   context.  When issued before context establishment completes or when
   the isProtReady method returns "false", it returns the desired state,
   otherwise it will indicate the actual state over the established
   context.

6.4.30.  getReplayDetState

   public boolean getReplayDetState()

   Returns the state of the replay detection option for the context.
   When issued before context establishment completes or when the
   isProtReady method returns "false", it returns the desired state,
   otherwise it will indicate the actual state over the established
   context.

6.4.31.  getSequenceDetState

   public boolean getSequenceDetState()

   Returns the state of the sequence detection option for the context.
   When issued before context establishment completes or when the
   isProtReady method returns "false", it returns the desired state,



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   otherwise it will indicate the actual state over the established
   context.

6.4.32.  getAnonymityState

   public boolean getAnonymityState()

   Returns "true" if this is an anonymous context.  When issued before
   context establishment completes or when the isProtReady method
   returns "false", it returns the desired state, otherwise it will
   indicate the actual state over the established context.

6.4.33.  isTransferable

   public boolean isTransferable() throws GSSException

   Returns "true" if the context is transferable to other processes
   through the use of the export method.  This call is only valid on
   fully established contexts.

6.4.34.  isProtReady

   public boolean isProtReady()

   Returns "true" if the per message operations can be applied over the
   context.  Some mechanisms may allow the usage of per-message
   operations before the context is fully established.  This will also
   indicate that the get methods will return actual context state
   characteristics instead of the desired ones.

6.4.35.  getConfState

   public boolean getConfState()

   Returns the confidentiality service state over the context.  When
   issued before context establishment completes or when the isProtReady
   method returns "false", it returns the desired state, otherwise it
   will indicate the actual state over the established context.

6.4.36.  getIntegState

   public boolean getIntegState()

   Returns the integrity service state over the context.  When issued
   before context establishment completes or when the isProtReady method
   returns "false", it returns the desired state, otherwise it will
   indicate the actual state over the established context.




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6.4.37.  getLifetime

   public int getLifetime()

   Returns the context lifetime in seconds.  When issued before context
   establishment completes or when the isProtReady method returns
   "false", it returns the desired lifetime, otherwise it will indicate
   the remaining lifetime for the context.

6.4.38.  getSrcName

   public GSSName getSrcName() throws GSSException

   Returns the name of the context initiator.  This call is valid only
   after the context is fully established or the isProtReady method
   returns "true".  It is guaranteed to return an MN.

6.4.39.  getTargName

   public GSSName getTargName() throws GSSException

   Returns the name of the context target (acceptor).  This call is
   valid only after the context is fully established or the isProtReady
   method returns "true".  It is guaranteed to return an MN.

6.4.40.  getMech

   public Oid getMech() throws GSSException

   Returns the mechanism oid for this context. This method may be called
   before the context is fully established, but the mechanism returned
   may change on successive calls in negotiated mechanism case.

6.4.41.  getDelegCred

   public GSSCredential getDelegCred() throws GSSException

   Returns the delegated credential object on the acceptor's side.  To
   check for availability of delegated credentials call
   getDelegCredState.  This call is only valid on fully established
   contexts.

6.4.42.  isInitiator

   public boolean isInitiator() throws GSSException

   Returns "true" if this is the initiator of the context.  This call is
   only valid after the context creation process has started.



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6.5.  public class MessageProp

   This is a utility class used within the per-message GSSContext
   methods to convey per-message properties.

   When used with the GSSContext interface's wrap and getMIC methods, an
   instance of this class is used to indicate the desired QOP and to
   request if confidentiality services are to be applied to caller
   supplied data (wrap only).  To request default QOP, the value of 0
   should be used for QOP.

   When used with the unwrap and verifyMIC methods of the GSSContext
   interface, an instance of this class will be used to indicate the
   applied QOP and confidentiality services over the supplied message.
   In the case of verifyMIC, the confidentiality state will always be
   "false".  Upon return from these methods, this object will also
   contain any supplementary status values applicable to the processed
   token.  The supplementary status values can indicate old tokens, out
   of sequence tokens, gap tokens or duplicate tokens.

6.5.1.  Constructors

   public MessageProp(boolean privState)

   Constructor which sets QOP to 0 indicating that the default QOP is
   requested.

   Parameters:

      privState The desired privacy state. "true" for privacy and
                "false" for integrity only.


   public MessageProp(int qop, boolean privState)

   Constructor which sets the values for the qop and privacy state.

   Parameters:

      qop       The desired QOP.  Use 0 to request a default QOP.

      privState The desired privacy state. "true" for privacy and
                "false" for integrity only.








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6.5.2.  getQOP

   public int getQOP()

   Retrieves the QOP value.

6.5.3.  getPrivacy

   public boolean getPrivacy()

   Retrieves the privacy state.

6.5.4.  getMinorStatus

   public int getMinorStatus()

   Retrieves the minor status that the underlying mechanism might have
   set.

6.5.5.  getMinorString

   public String getMinorString()

   Returns a string explaining the mechanism specific error code. null
   will be returned when no mechanism error code has been set.

6.5.6.  setQOP

   public void setQOP(int qopVal)

   Sets the QOP value.

   Parameters:

      qopVal    The QOP value to be set.  Use 0 to request a default
                QOP value.

6.5.7.  setPrivacy

   public void setPrivacy(boolean privState)

   Sets the privacy state.

   Parameters:

      privState The privacy state to set.





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6.5.8.  isDuplicateToken

   public boolean isDuplicateToken()

   Returns "true" if this is a duplicate of an earlier token.

6.5.9.  isOldToken

   public boolean isOldToken()

   Returns "true" if the token's validity period has expired.

6.5.10.  isUnseqToken

   public boolean isUnseqToken()

   Returns "true" if a later token has already been processed.

6.5.11.  isGapToken

   public boolean isGapToken()

   Returns "true" if an expected per-message token was not received.

6.5.12.  setSupplementaryStates

   public void setSupplementaryStates(boolean duplicate,
                   boolean old, boolean unseq, boolean gap,
                   int minorStatus, String minorString)

   This method sets the state for the supplementary information flags
   and the minor status in MessageProp.  It is not used by the
   application but by the GSS implementation to return this information
   to the caller of a per-message context method.

   Parameters:

      duplicate true if the token was a duplicate of an earlier token,
                false otherwise

      old       true if the token's validity period has expired, false
                otherwise

      unseq     true if a later token has already been processed,
                false otherwise

      gap       true if one or more predecessor tokens have not yet
                been successfully processed, false otherwise



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      minorStatus   the integer minor status code that the underlying
                    mechanism wants to set

      minorString   the textual representation of the minorStatus
                    value

6.6.  public class ChannelBinding

   The GSS-API accommodates the concept of caller-provided channel
   binding information.  Channel bindings are used to strengthen the
   quality with which peer entity authentication is provided during
   context establishment.  They enable the GSS-API callers to bind the
   establishment of the security context to relevant characteristics
   like addresses or to application specific data.

   The caller initiating the security context must determine the
   appropriate channel binding values to set in the GSSContext object.
   The acceptor must provide an identical binding in order to validate
   that received tokens possess correct channel-related characteristics.

   Use of channel bindings is optional in GSS-API.  Since channel-
   binding information may be transmitted in context establishment
   tokens, applications should therefore not use confidential data as
   channel-binding components.

6.6.1.  Constructors

   public ChannelBinding(InetAddress initAddr, InetAddress acceptAddr,
                   byte[] appData)

   Create a ChannelBinding object with user supplied address information
   and data.  "null" values can be used for any fields which the
   application does not want to specify.

   Parameters:

      initAddr  The address of the context initiator.  "null" value
                can be supplied to indicate that the application does
                not want to set this value.

      acceptAddrThe address of the context acceptor.  "null" value can
                be supplied to indicate that the application does not
                want to set this value.

      appData   Application supplied data to be used as part of the
                channel bindings.  "null" value can be supplied to
                indicate that the application does not want to set
                this value.



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   public ChannelBinding(byte[] appData)

   Creates a ChannelBinding object without any addressing information.

   Parameters:

      appData   Application supplied data to be used as part of the
                channel bindings.

6.6.2.  getInitiatorAddress

   public InetAddress getInitiatorAddress()

   Returns the initiator's address for this channel binding. "null" is
   returned if the address has not been set.

6.6.3.  getAcceptorAddress

   public InetAddress getAcceptorAddress()

   Returns the acceptor's address for this channel binding. "null" is
   returned if the address has not been set.

6.6.4.  getApplicationData

   public byte[] getApplicationData()

   Returns application data being used as part of the ChannelBinding.
   "null" is returned if no application data has been specified for the
   channel binding.

6.6.5.  equals

   public boolean equals(Object obj)

   Returns "true" if two channel bindings match. (Note that the Java
   language specification requires that two objects that are equal
   according to the equals(Object) method must return the same integer
   result when the hashCode() method is called on them.)

   Parameters:

      obj       Another channel binding to compare with.








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6.7.  public class Oid

   This class represents Universal Object Identifiers (Oids) and their
   associated operations.

   Oids are hierarchically globally-interpretable identifiers used
   within the GSS-API framework to identify mechanisms and name formats.

   The structure and encoding of Oids is defined in ISOIEC-8824 and
   ISOIEC-8825.  For example the Oid representation of Kerberos V5
   mechanism is "1.2.840.113554.1.2.2"

   The GSSName name class contains public static Oid objects
   representing the standard name types defined in GSS-API.

6.7.1.  Constructors

   public Oid(String strOid) throws GSSException

   Creates an Oid object from a string representation of its integer
   components (e.g. "1.2.840.113554.1.2.2").

   Parameters:

      strOid    The string representation for the oid.

   public Oid(InputStream derOid) throws GSSException

   Creates an Oid object from its DER encoding.  This refers to the full
   encoding including tag and length.  The structure and encoding of
   Oids is defined in ISOIEC-8824 and ISOIEC-8825.  This method is
   identical in functionality to its byte array counterpart.

   Parameters:

      derOid    Stream containing the DER encoded oid.

   public Oid(byte[] DEROid) throws GSSException

   Creates an Oid object from its DER encoding.  This refers to the full
   encoding including tag and length.  The structure and encoding of
   Oids is defined in ISOIEC-8824 and ISOIEC-8825.  This method is
   identical in functionality to its byte array counterpart.

   Parameters:

      derOid    Byte array storing a DER encoded oid.




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6.7.2.  toString

   public String toString()

   Returns a string representation of the oid's integer components in
   dot separated notation (e.g. "1.2.840.113554.1.2.2").

6.7.3.  equals

   public boolean equals(Object Obj)

   Returns "true" if the two Oid objects represent the same oid value.
   (Note that the Java language specification requires that two objects
   that are equal according to the equals(Object) method must return the
   same integer result when the hashCode() method is called on them.)

   Parameters:

      obj       Another Oid object to compare with.

6.7.4.  getDER

   public byte[] getDER()

   Returns the full ASN.1 DER encoding for this oid object, which
   includes the tag and length.

6.7.5.  containedIn

   public boolean containedIn(Oid[] oids)

   A utility method to test if an Oid object is contained within the
   supplied Oid object array.

   Parameters:

      oids      An array of oids to search.

6.8.  public class GSSException extends Exception

   This exception is thrown whenever a fatal GSS-API error occurs
   including mechanism specific errors.  It may contain both, the major
   and minor, GSS-API status codes.  The mechanism implementers are
   responsible for setting appropriate minor status codes when throwing
   this exception.  Aside from delivering the numeric error code(s) to
   the caller, this class performs the mapping from their numeric values
   to textual representations.  All Java GSS-API methods are declared
   throwing this exception.



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   All implementations are encouraged to use the Java
   internationalization techniques to provide local translations of the
   message strings.

6.8.1.  Static Constants

   All valid major GSS-API error code values are declared as constants
   in this class.

   public static final int BAD_BINDINGS

   Channel bindings mismatch error.


   public static final int BAD_MECH

   Unsupported mechanism requested error.


   public static final int BAD_NAME

   Invalid name provided error.


   public static final int BAD_NAMETYPE

   Name of unsupported type provided error.


   public static final int BAD_STATUS

   Invalid status code error - this is the default status value.


   public static final int BAD_MIC

   Token had invalid integrity check error.


   public static final int CONTEXT_EXPIRED

   Specified security context expired error.


   public static final int CREDENTIALS_EXPIRED

   Expired credentials detected error.




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   public static final int DEFECTIVE_CREDENTIAL

   Defective credential error.


   public static final int DEFECTIVE_TOKEN

   Defective token error.


   public static final int FAILURE

   General failure, unspecified at GSS-API level.


   public static final int NO_CONTEXT

   Invalid security context error.


   public static final int NO_CRED

   Invalid credentials error.


   public static final int BAD_QOP

   Unsupported QOP value error.


   public static final int UNAUTHORIZED

   Operation unauthorized error.


   public static final int UNAVAILABLE

   Operation unavailable error.


   public static final int DUPLICATE_ELEMENT

   Duplicate credential element requested error.


   public static final int NAME_NOT_MN

   Name contains multi-mechanism elements error.



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   public static final int DUPLICATE_TOKEN

   The token was a duplicate of an earlier token.  This is a fatal error
   code that may occur during context establishment.  It is not used to
   indicate supplementary status values.  The MessageProp object is used
   for that purpose.

   public static final int OLD_TOKEN

   The token's validity period has expired.  This is a fatal error code
   that may occur during context establishment.  It is not used to
   indicate supplementary status values.  The MessageProp object is used
   for that purpose.

   public static final int UNSEQ_TOKEN

   A later token has already been processed.  This is a fatal error code
   that may occur during context establishment.  It is not used to
   indicate supplementary status values.  The MessageProp object is used
   for that purpose.

   public static final int GAP_TOKEN

   An expected per-message token was not received.  This is a fatal
   error code that may occur during context establishment.  It is not
   used to indicate supplementary status values.  The MessageProp object
   is used for that purpose.

6.8.2.  Constructors

   public GSSException(int majorCode)

   Creates a GSSException object with a specified major code.

   Parameters:

      majorCode The GSS error code causing this exception to be
                thrown.

   public GSSException(int majorCode, int minorCode, String minorString)

   Creates a GSSException object with the specified major code, minor
   code, and minor code textual explanation.  This constructor is to be
   used when the exception is originating from the security mechanism.
   It allows to specify the GSS code and the mechanism code.






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   Parameters:

      majorCode      The GSS error code causing this exception to be
                     thrown.

      minorCode      The mechanism error code causing this exception
                     to be thrown.

      minorString    The textual explanation of the mechanism error
                     code.

6.8.3.  getMajor

   public int getMajor()

   Returns the major code representing the GSS error code that caused
   this exception to be thrown.

6.8.4.  getMinor

   public int getMinor()

   Returns the mechanism error code that caused this exception.  The
   minor code is set by the underlying mechanism.  Value of 0 indicates
   that mechanism error code is not set.

6.8.5.  getMajorString

   public String getMajorString()

   Returns a string explaining the GSS major error code causing this
   exception to be thrown.

6.8.6.  getMinorString

   public String getMinorString()

   Returns a string explaining the mechanism specific error code.  null
   will be returned when no mechanism error code has been set.

6.8.7.  setMinor

   public void setMinor(int minorCode, String message)

   Used internally by the GSS-API implementation and the underlying
   mechanisms to set the minor code and its textual representation.





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   Parameters:

      minorCode The mechanism specific error code.

      message   A textual explanation of the mechanism error code.

6.8.8.  toString

   public String toString()

   Returns a textual representation of both the major and minor status
   codes.

6.8.9.  getMessage

   public String getMessage()

   Returns a detailed message of this exception.  Overrides
   Throwable.getMessage.  It is customary in Java to use this method to
   obtain exception information.

7.  Sample Applications

7.1.  Simple GSS Context Initiator

   import org.ietf.jgss.*;

   /**
    * This is a partial sketch for a simple client program that acts
    * as a GSS context initiator.  It illustrates how to use the Java
    * bindings for the GSS-API specified in
    * Generic Security Service API Version 2 : Java bindings
    *
    *
    * This code sketch assumes the existence of a GSS-API
    * implementation that supports the mechanism that it will need and
    * is present as a library package (org.ietf.jgss) either as part of
    * the standard JRE or in the CLASSPATH the application specifies.
    */

   public class SimpleClient {

       private String serviceName; // name of peer (ie. server)
       private GSSCredential clientCred = null;
       private GSSContext context = null;
       private Oid mech; // underlying mechanism to use

       private GSSManager mgr = GSSManager.getInstance();



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       ...
       ...

       private void clientActions() {
           initializeGSS();
           establishContext();
           doCommunication();
       }

       /**
        * Acquire credentials for the client.
        */
       private void initializeGSS() {

           try {

               clientCred = mgr.createCredential(null /*default princ*/,
                   GSSCredential.INDEFINITE_LIFETIME /* max lifetime */,
                   mech /* mechanism  to use */,
                   GSSCredential.INITIATE_ONLY /* init context */);

               print("GSSCredential created for " +
                     cred.getName().toString());
               print("Credential lifetime (sec)=" +
                     cred.getRemainingLifetime());
           } catch (GSSException e) {
                   print("GSS-API error in credential acquisition: "
                         + e.getMessage());
                   ...
                   ...
           }

           ...
           ...
       }

       /**
        * Does the security context establishment with the
        * server.
        */
       private void establishContext() {

           byte[] inToken = new byte[0];
           byte[] outToken = null;

           try {

               GSSName peer = mgr.createName(serviceName,



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                                  GSSName.NT_HOSTBASED_SERVICE);

               context = mgr.createContext(peer, mech, gssCred,
                        GSSContext.INDEFINITE_LIFETIME/*lifetime*/);

               // Will need to support confidentiality
               context.requestConf(true);

               while (!context.isEstablished()) {

                   outToken = context.initSecContext(inToken, 0,
                                                     inToken.length);

                   if (outToken != null)
                       writeGSSToken(outToken);

                   if (!context.isEstablished())
                       inToken = readGSSToken();
               }

               GSSName peer = context.getSrcName();
               print("Security context established with " + peer +
                     " using underlying mechanism " + mech.toString());
           } catch (GSSException e) {
                   print("GSS-API error during context establishment: "
                         + e.getMessage());
               ...
               ...
           }

           ...
           ...
       }

       /**
        * Sends some data to the server and reads back the
        * response.
        */
       private void doCommunication()  {
               byte[] inToken = null;
               byte[] outToken = null;
               byte[] buffer;

               // Container for multiple input-output arguments to and
               // from the per-message routines (e.g., wrap/unwrap).
               MessageProp messgInfo = new MessageProp();

               try {



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                   /*
                    * Now send some bytes to the server to be
                    * processed. They will be integrity protected but
                    * not encrypted for privacy.
                    */

                   buffer = readFromFile();

                   // Set privacy to false and use the default QOP
                   messgInfo.setPrivacy(false);

                   outToken = context.wrap(buffer, 0, buffer.length,
                                           messgInfo);

                   writeGSSToken(outToken);

                   /*
                    * Now read the response from the server.
                    */

                   inToken = readGSSToken();
                   buffer = context.unwrap(inToken, 0, inToken.length,
                                           messgInfo);
                   // All ok if no exception was thrown!

                   GSSName peer = context.getSrcName();

                   print("Message from "       + peer.toString()
                         + " arrived.");
                   print("Was it encrypted? "  +
                         messgInfo.getPrivacy());
                   print("Duplicate Token? "   +
                         messgInfo.isDuplicateToken());
                   print("Old Token? "         +
                         messgInfo.isOldToken());
                   print("Unsequenced Token? " +
                         messgInfo.isUnseqToken());
                   print("Gap Token? "         +
                         messgInfo.isGapToken());

                   ...
                   ...

               } catch (GSSException e) {
                   print("GSS-API error in per-message calls: "
                         + e.getMessage());
                   ...
                   ...



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               }

               ...

               ...

       } // end of doCommunication method

       ...
       ...

   } // end of class SimpleClient

7.2.  Simple GSS Context Acceptor

   import org.ietf.jgss.*;

   /**
    * This is a partial sketch for a simple server program that acts
    * as a GSS context acceptor. It illustrates how to use the Java
    * bindings for the GSS-API specified in
    * Generic Security Service API Version 2 : Java bindings
    *
    * This code sketch assumes the existence of a GSS-API
    * implementation that supports the mechanisms that it will need and
    * is present as a library package (org.ietf.jgss) either as part of
    * the standard JRE or in the CLASSPATH the application specifies.
    */

   import org.ietf.jgss.*;

   public class SimpleServer {

       private String serviceName;
       private GSSName name;
       private GSSCredential cred;

       private GSSManager mgr;

       ...
       ...

       /**
        * Wait for client connections, establish security contexts and
        * provide service.
        */
       private void loop() {




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       ...
       ...

           mgr = GSSManager.getInstance();

           name = mgr.createName(serviceName,
                      GSSName.NT_HOSTBASED_SERVICE);

           cred = mgr.createCredential(name,
                      GSSCredential.INDEFINITE_LIFETIME,
                      null,
                      GSSCredential.ACCEPT_ONLY);


           // Loop infinitely
           while (true) {

               Socket s = serverSock.accept();

               // Start a new thread to serve this connection
               Thread serverThread = new ServerThread(s);
               serverThread.start();

           }
       }

       /**
        * Inner class ServerThread whose run() method provides the
        * secure service to a connection.
        */

       private class ServerThread extends Thread {

       ...
       ...

           /**
            * Deals with the connection from one client. It also
            * handles all GSSException's thrown while talking to
            * this client.
            */
           public void run() {

               byte[] inToken = null;
               byte[] outToken = null;
               byte[] buffer;

               GSSName peer;



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               // Container for multiple input-output arguments to and
               // from the per-message routines (ie. wrap/unwrap).
               MessageProp supplInfo = new MessageProp();

               GSSContext secContext = null;

               try {


                   // Now do the context establishment loop

                   GSSContext context = mgr.createContext(cred);

                   while (!context.isEstablished()) {

                       inToken = readGSSToken();

                       outToken = context.acceptSecContext(inToken, 0,
                                                   inToken.length);

                       if (outToken != null)
                           writeGSSToken(outToken);

                   }


                   // SimpleServer wants confidentiality to be
                   // available. Check for it.
                   if (!context.getConfState()){
                       ...
                       ...
                   }

                   GSSName peer = context.getSrcName();
                   Oid mech = context.getMech();
                   print("Security context established with " +
                         peer.toString() +
                         " using underlying mechanism " +
                         mech.toString() +
                         " from Provider " +
                         context.getProvider().getName());


                   // Now read the bytes sent by the client to be
                   // processed.
                   inToken = readGSSToken();

                   // Unwrap the message



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                   buffer = context.unwrap(inToken, 0, inToken.length,
                                             supplInfo);
                   // All ok if no exception was thrown!

                   // Print other supplementary per-message status
                   // information

                   print("Message from " +
                           peer.toString() + " arrived.");
                   print("Was it encrypted? " +
                           supplInfo.getPrivacy());
                   print("Duplicate Token? " +
                           supplInfo.isDuplicateToken());
                   print("Old Token? "  + supplInfo.isOldToken());
                   print("Unsequenced Token? " +
                           supplInfo.isUnseqToken());
                   print("Gap Token? "  + supplInfo.isGapToken());

                   /*
                    * Now process the bytes and send back an encrypted
                    * response.
                    */

                   buffer = serverProcess(buffer);

                   // Encipher it and send it across

                   supplInfo.setPrivacy(true); // privacy requested
                   supplInfo.setQOP(0); // default QOP
                   outToken = context.wrap(buffer, 0, buffer.length,
                                              supplInfo);
                   writeGSSToken(outToken);

               } catch (GSSException e) {
                   print("GSS-API Error: " + e.getMessage());
                   // Alternatively, could call e.getMajorMessage()
                   // and e.getMinorMessage()
                   print("Abandoning security context.");

                   ...
                   ...

               }

               ...
               ...

           } // end of run method in ServerThread



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       } // end of inner class ServerThread

       ...
       ...

   } // end of class SimpleServer

8.  Security Considerations

   The Java language security model allows platform providers to have
   policy based fine-grained access control over any resource that an
   application wants. When using a Java security manager (such as, but
   not limited to, the case of applets running in browsers) the
   application code is in a sandbox by default.

   Administrators of the platform JRE determine what permissions, if
   any, are to be given to source from different codebases. Thus the
   administrator has to be aware of any special requirements that the
   GSS provider might have for system resources. For instance, a
   Kerberos provider might wish to make a network connection to the KDC
   to obtain initial credentials. This would not be allowed under the
   sandbox unless the administrator had granted permissions for this.
   Also note that this granting and checking of permissions happens
   transparently to the application and is outside the scope of this
   document.

   The Java language allows administrators to pre-configure a list of
   security service providers in the <JRE>/lib/security/java.security
   file. At runtime, the system approaches these providers in order of
   preference when looking for security related services. Applications
   have a means to modify this list through methods in the "Security"
   class in the "java.security" package. However, since these
   modifications would be visible in the entire JVM and thus affect all
   code executing in it, this operation is not available in the sandbox
   and requires special permissions to perform. Thus when a GSS
   application has special needs that are met by a particular security
   provider, it has two choices:

      1) To install the provider on a JVM wide basis using the
         java.security.Security class and then depend on the system to
         find the right provider automatically when the need arises.
         (This would require the application to be granted a
         "insertProvider SecurityPermission".)

      2) To pass an instance of the provider to the local instance of
         GSSManager so that only factory calls going through that
         GSSManager use the desired provider. (This would not require
         any permissions.)



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9.  Acknowledgments

   This proposed API leverages earlier work performed by the IETF's CAT
   WG as outlined in both RFC 2743 and RFC 2744.  Many conceptual
   definitions, implementation directions, and explanations have been
   included from these documents.

   We would like to thank Mike Eisler, Lin Ling, Ram Marti, Michael
   Saltz and other members of Sun's development team for their helpful
   input, comments and suggestions.

   We would also like to thank Joe Salowey, and Michael Smith for many
   insightful ideas and suggestions that have contributed to this
   document.

10.  Bibliography

   [GSSAPIv2]        Linn, J., "Generic Security Service Application
                     Program Interface, Version 2", RFC 2078, January
                     1997.

   [GSSAPIv2-UPDATE] Linn, J., "Generic Security Service Application
                     Program Interface, Version 2, Update 1", RFC 2743,
                     January 2000.

   [GSSAPI-Cbind]    Wray, J., "Generic Security Service API Version 2 :
                     C-bindings", RFC 2744, January 2000.

   [KERBV5]          Linn, J., "The Kerberos Version 5 GSS-API
                     Mechanism", RFC 1964, June 1996.

   [SPKM]            Adams, C., "The Simple Public-Key GSS-API
                     Mechanism", RFC 2025, October 1996.


















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11.  Authors' Addresses

   Address comments related to this memorandum to:

        <cat-ietf@mit.edu>

   Jack Kabat
   ValiCert, Inc.
   339 N. Bernardo Avenue
   Mountain View, CA
   94043, USA

   Phone: +1-650-567-5496
   EMail: jackk@valicert.com


   Mayank Upadhyay
   Sun Microsystems, Inc.
   901 San Antonio Road, MS CUP02-102
   Palo Alto, CA 94303

   Phone: +1-408-517-5956
   EMail: mdu@eng.sun.com




























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12.  Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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