RFC 2853
Generic Security Service API Version 2 : Java Bindings
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
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
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
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
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. . . . . . . . . . . . . . . . . 961. 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.
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
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.
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.
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.
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"
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 ">".
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.
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
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.
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.
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
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.
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
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.
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.
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.
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.
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
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.
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.
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.
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