rfc8353
Internet Engineering Task Force (IETF) M. Upadhyay
Request for Comments: 8353 Google
Obsoletes: 5653 S. Malkani
Category: Standards Track ActivIdentity
ISSN: 2070-1721 W. Wang
Oracle
May 2018
Generic Security Service API Version 2: Java Bindings Update
Abstract
The Generic Security Services Application Programming Interface
(GSS-API) offers application programmers uniform access to security
services atop a variety of underlying cryptographic mechanisms. This
document updates the Java bindings for the GSS-API that are specified
in "Generic Security Service API Version 2: Java Bindings Update"
(RFC 5653). This document obsoletes RFC 5653 by adding a new output
token field to the GSSException class so that when the initSecContext
or acceptSecContext methods of the GSSContext class fail, it has a
chance to emit an error token that can be sent to the peer for
debugging or informational purpose. The stream-based GSSContext
methods are also removed in this version.
The GSS-API is described at a language-independent conceptual level
in "Generic Security Service Application Program Interface Version 2,
Update 1" (RFC 2743). 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)"
(RFC 2025) and "The Kerberos Version 5 Generic Security Service
Application Program Interface (GSS-API) Mechanism: Version 2"
(RFC 4121).
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Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8353.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Without obtaining an adequate license from the person(s) controlling
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not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 7
3. GSS-API Operational Paradigm . . . . . . . . . . . . . . . . 7
4. Additional Controls . . . . . . . . . . . . . . . . . . . . . 9
4.1. Delegation . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Mutual Authentication . . . . . . . . . . . . . . . . . . 11
4.3. Replay and Out-of-Sequence Detection . . . . . . . . . . 11
4.4. Anonymous Authentication . . . . . . . . . . . . . . . . 12
4.5. Integrity and Confidentiality . . . . . . . . . . . . . . 13
4.6. Inter-process Context Transfer . . . . . . . . . . . . . 13
4.7. The Use of Incomplete Contexts . . . . . . . . . . . . . 14
5. Calling Conventions . . . . . . . . . . . . . . . . . . . . . 15
5.1. Package Name . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Provider Framework . . . . . . . . . . . . . . . . . . . 15
5.3. Integer Types . . . . . . . . . . . . . . . . . . . . . . 16
5.4. Opaque Data Types . . . . . . . . . . . . . . . . . . . . 16
5.5. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.6. Object Identifiers . . . . . . . . . . . . . . . . . . . 16
5.7. Object Identifier Sets . . . . . . . . . . . . . . . . . 17
5.8. Credentials . . . . . . . . . . . . . . . . . . . . . . . 17
5.9. Contexts . . . . . . . . . . . . . . . . . . . . . . . . 19
5.10. Authentication Tokens . . . . . . . . . . . . . . . . . . 20
5.11. Inter-process Tokens . . . . . . . . . . . . . . . . . . 20
5.12. Error Reporting . . . . . . . . . . . . . . . . . . . . . 20
5.12.1. GSS Status Codes . . . . . . . . . . . . . . . . . . 21
5.12.2. Mechanism-Specific Status Codes . . . . . . . . . . 23
5.12.3. Supplementary Status Codes . . . . . . . . . . . . . 23
5.13. Names . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.14. Channel Bindings . . . . . . . . . . . . . . . . . . . . 27
5.15. Optional Parameters . . . . . . . . . . . . . . . . . . . 28
6. Introduction to GSS-API Classes and Interfaces . . . . . . . 28
6.1. GSSManager Class . . . . . . . . . . . . . . . . . . . . 28
6.2. GSSName Interface . . . . . . . . . . . . . . . . . . . . 29
6.3. GSSCredential Interface . . . . . . . . . . . . . . . . . 30
6.4. GSSContext Interface . . . . . . . . . . . . . . . . . . 31
6.5. MessageProp Class . . . . . . . . . . . . . . . . . . . . 32
6.6. GSSException Class . . . . . . . . . . . . . . . . . . . 32
6.7. Oid Class . . . . . . . . . . . . . . . . . . . . . . . . 32
6.8. ChannelBinding Class . . . . . . . . . . . . . . . . . . 33
7. Detailed GSS-API Class Description . . . . . . . . . . . . . 33
7.1. public abstract class GSSManager . . . . . . . . . . . . 33
7.1.1. getInstance . . . . . . . . . . . . . . . . . . . . . 34
7.1.2. getMechs . . . . . . . . . . . . . . . . . . . . . . 34
7.1.3. getNamesForMech . . . . . . . . . . . . . . . . . . . 35
7.1.4. getMechsForName . . . . . . . . . . . . . . . . . . . 35
7.1.5. createName . . . . . . . . . . . . . . . . . . . . . 35
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7.1.6. createName . . . . . . . . . . . . . . . . . . . . . 36
7.1.7. createName . . . . . . . . . . . . . . . . . . . . . 36
7.1.8. createName . . . . . . . . . . . . . . . . . . . . . 37
7.1.9. createCredential . . . . . . . . . . . . . . . . . . 38
7.1.10. createCredential . . . . . . . . . . . . . . . . . . 38
7.1.11. createCredential . . . . . . . . . . . . . . . . . . 39
7.1.12. createContext . . . . . . . . . . . . . . . . . . . . 39
7.1.13. createContext . . . . . . . . . . . . . . . . . . . . 40
7.1.14. createContext . . . . . . . . . . . . . . . . . . . . 40
7.1.15. addProviderAtFront . . . . . . . . . . . . . . . . . 41
7.1.15.1. addProviderAtFront Example Code . . . . . . . . 42
7.1.16. addProviderAtEnd . . . . . . . . . . . . . . . . . . 43
7.1.16.1. addProviderAtEnd Example Code . . . . . . . . . 43
7.1.17. Example Code . . . . . . . . . . . . . . . . . . . . 44
7.2. public interface GSSName . . . . . . . . . . . . . . . . 45
7.2.1. Static Constants . . . . . . . . . . . . . . . . . . 45
7.2.2. equals . . . . . . . . . . . . . . . . . . . . . . . 46
7.2.3. equals . . . . . . . . . . . . . . . . . . . . . . . 46
7.2.4. canonicalize . . . . . . . . . . . . . . . . . . . . 47
7.2.5. export . . . . . . . . . . . . . . . . . . . . . . . 47
7.2.6. toString . . . . . . . . . . . . . . . . . . . . . . 47
7.2.7. getStringNameType . . . . . . . . . . . . . . . . . . 47
7.2.8. isAnonymous . . . . . . . . . . . . . . . . . . . . . 47
7.2.9. isMN . . . . . . . . . . . . . . . . . . . . . . . . 48
7.2.10. Example Code . . . . . . . . . . . . . . . . . . . . 48
7.3. public interface GSSCredential implements Cloneable . . . 49
7.3.1. Static Constants . . . . . . . . . . . . . . . . . . 50
7.3.2. dispose . . . . . . . . . . . . . . . . . . . . . . . 50
7.3.3. getName . . . . . . . . . . . . . . . . . . . . . . . 50
7.3.4. getName . . . . . . . . . . . . . . . . . . . . . . . 51
7.3.5. getRemainingLifetime . . . . . . . . . . . . . . . . 51
7.3.6. getRemainingInitLifetime . . . . . . . . . . . . . . 51
7.3.7. getRemainingAcceptLifetime . . . . . . . . . . . . . 51
7.3.8. getUsage . . . . . . . . . . . . . . . . . . . . . . 52
7.3.9. getUsage . . . . . . . . . . . . . . . . . . . . . . 52
7.3.10. getMechs . . . . . . . . . . . . . . . . . . . . . . 52
7.3.11. add . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.3.12. equals . . . . . . . . . . . . . . . . . . . . . . . 53
7.3.13. Example Code . . . . . . . . . . . . . . . . . . . . 54
7.4. public interface GSSContext . . . . . . . . . . . . . . . 54
7.4.1. Static Constants . . . . . . . . . . . . . . . . . . 55
7.4.2. initSecContext . . . . . . . . . . . . . . . . . . . 56
7.4.3. acceptSecContext . . . . . . . . . . . . . . . . . . 56
7.4.4. isEstablished . . . . . . . . . . . . . . . . . . . . 57
7.4.5. dispose . . . . . . . . . . . . . . . . . . . . . . . 57
7.4.6. getWrapSizeLimit . . . . . . . . . . . . . . . . . . 58
7.4.7. wrap . . . . . . . . . . . . . . . . . . . . . . . . 58
7.4.8. unwrap . . . . . . . . . . . . . . . . . . . . . . . 59
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7.4.9. getMIC . . . . . . . . . . . . . . . . . . . . . . . 60
7.4.10. verifyMIC . . . . . . . . . . . . . . . . . . . . . . 61
7.4.11. export . . . . . . . . . . . . . . . . . . . . . . . 62
7.4.12. requestMutualAuth . . . . . . . . . . . . . . . . . . 62
7.4.13. requestReplayDet . . . . . . . . . . . . . . . . . . 63
7.4.14. requestSequenceDet . . . . . . . . . . . . . . . . . 63
7.4.15. requestCredDeleg . . . . . . . . . . . . . . . . . . 63
7.4.16. requestAnonymity . . . . . . . . . . . . . . . . . . 64
7.4.17. requestConf . . . . . . . . . . . . . . . . . . . . . 64
7.4.18. requestInteg . . . . . . . . . . . . . . . . . . . . 64
7.4.19. requestLifetime . . . . . . . . . . . . . . . . . . . 64
7.4.20. setChannelBinding . . . . . . . . . . . . . . . . . . 65
7.4.21. getCredDelegState . . . . . . . . . . . . . . . . . . 65
7.4.22. getMutualAuthState . . . . . . . . . . . . . . . . . 65
7.4.23. getReplayDetState . . . . . . . . . . . . . . . . . . 65
7.4.24. getSequenceDetState . . . . . . . . . . . . . . . . . 66
7.4.25. getAnonymityState . . . . . . . . . . . . . . . . . . 66
7.4.26. isTransferable . . . . . . . . . . . . . . . . . . . 66
7.4.27. isProtReady . . . . . . . . . . . . . . . . . . . . . 66
7.4.28. getConfState . . . . . . . . . . . . . . . . . . . . 66
7.4.29. getIntegState . . . . . . . . . . . . . . . . . . . . 67
7.4.30. getLifetime . . . . . . . . . . . . . . . . . . . . . 67
7.4.31. getSrcName . . . . . . . . . . . . . . . . . . . . . 67
7.4.32. getTargName . . . . . . . . . . . . . . . . . . . . . 67
7.4.33. getMech . . . . . . . . . . . . . . . . . . . . . . . 67
7.4.34. getDelegCred . . . . . . . . . . . . . . . . . . . . 68
7.4.35. isInitiator . . . . . . . . . . . . . . . . . . . . . 68
7.4.36. Example Code . . . . . . . . . . . . . . . . . . . . 68
7.5. public class MessageProp . . . . . . . . . . . . . . . . 70
7.5.1. Constructors . . . . . . . . . . . . . . . . . . . . 70
7.5.2. getQOP . . . . . . . . . . . . . . . . . . . . . . . 71
7.5.3. getPrivacy . . . . . . . . . . . . . . . . . . . . . 71
7.5.4. getMinorStatus . . . . . . . . . . . . . . . . . . . 71
7.5.5. getMinorString . . . . . . . . . . . . . . . . . . . 71
7.5.6. setQOP . . . . . . . . . . . . . . . . . . . . . . . 71
7.5.7. setPrivacy . . . . . . . . . . . . . . . . . . . . . 72
7.5.8. isDuplicateToken . . . . . . . . . . . . . . . . . . 72
7.5.9. isOldToken . . . . . . . . . . . . . . . . . . . . . 72
7.5.10. isUnseqToken . . . . . . . . . . . . . . . . . . . . 72
7.5.11. isGapToken . . . . . . . . . . . . . . . . . . . . . 72
7.5.12. setSupplementaryStates . . . . . . . . . . . . . . . 72
7.6. public class ChannelBinding . . . . . . . . . . . . . . . 73
7.6.1. Constructors . . . . . . . . . . . . . . . . . . . . 73
7.6.2. getInitiatorAddress . . . . . . . . . . . . . . . . . 74
7.6.3. getAcceptorAddress . . . . . . . . . . . . . . . . . 74
7.6.4. getApplicationData . . . . . . . . . . . . . . . . . 74
7.6.5. equals . . . . . . . . . . . . . . . . . . . . . . . 75
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7.7. public class Oid . . . . . . . . . . . . . . . . . . . . 75
7.7.1. Constructors . . . . . . . . . . . . . . . . . . . . 75
7.7.2. toString . . . . . . . . . . . . . . . . . . . . . . 76
7.7.3. equals . . . . . . . . . . . . . . . . . . . . . . . 76
7.7.4. getDER . . . . . . . . . . . . . . . . . . . . . . . 76
7.7.5. containedIn . . . . . . . . . . . . . . . . . . . . . 77
7.8. public class GSSException extends Exception . . . . . . . 77
7.8.1. Static Constants . . . . . . . . . . . . . . . . . . 77
7.8.2. Constructors . . . . . . . . . . . . . . . . . . . . 80
7.8.3. getMajor . . . . . . . . . . . . . . . . . . . . . . 81
7.8.4. getMinor . . . . . . . . . . . . . . . . . . . . . . 81
7.8.5. getMajorString . . . . . . . . . . . . . . . . . . . 81
7.8.6. getMinorString . . . . . . . . . . . . . . . . . . . 81
7.8.7. getOutputToken . . . . . . . . . . . . . . . . . . . 82
7.8.8. setMinor . . . . . . . . . . . . . . . . . . . . . . 82
7.8.9. toString . . . . . . . . . . . . . . . . . . . . . . 82
7.8.10. getMessage . . . . . . . . . . . . . . . . . . . . . 82
8. Sample Applications . . . . . . . . . . . . . . . . . . . . . 83
8.1. Simple GSS Context Initiator . . . . . . . . . . . . . . 83
8.2. Simple GSS Context Acceptor . . . . . . . . . . . . . . . 87
9. Security Considerations . . . . . . . . . . . . . . . . . . . 90
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 91
11. Changes since RFC 5653 . . . . . . . . . . . . . . . . . . . 91
12. Changes since RFC 2853 . . . . . . . . . . . . . . . . . . . 93
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 94
13.1. Normative References . . . . . . . . . . . . . . . . . . 94
13.2. Informative References . . . . . . . . . . . . . . . . . 95
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 96
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 96
1. Introduction
This document specifies Java language bindings for the Generic
Security Services Application Programming Interface (GSS-API) version
2. GSS-API version 2 is described in a language-independent format
in RFC 2743 [RFC2743]. The GSS-API allows a caller application to
authenticate a principal identity, delegate rights to a peer, and
apply security services such as confidentiality and integrity on a
per-message basis.
This document and its predecessors, RFC 2853 [RFC2853] and RFC 5653
[RFC5653], leverage the work done by the working group (WG) in the
area of RFC 2743 [RFC2743] and the C-bindings of RFC 2744 [RFC2744].
Whenever appropriate, text has been used from the C-bindings document
(RFC 2744) to explain generic concepts and provide direction to the
implementors.
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The design goals of this API have been to satisfy all the
functionality defined in RFC 2743 [RFC2743] 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 the
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. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. GSS-API Operational Paradigm
"Generic Security Service Application Programming Interface, Version
2" [RFC2743] 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.
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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 a
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 before sending the resulting
token to the receiving application. The receiver will pass the
received token (and, in the case of data protected by getMIC, the
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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.
4. 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
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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 it
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.
4.1. 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 enabled, 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
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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 override 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.
4.2. 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.
4.3. 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 (authentication
tag) 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.
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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 the 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".
4.4. 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
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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
(OID) 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".
4.5. Integrity and Confidentiality
If a GSSContext supports the integrity service, the getMic method may
be used to create message integrity check tokens on application
messages.
If a GSSContext supports the confidentiality service, the 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. Confidentiality will
be applied if the privacy state is set to true.
4.6. Inter-process Context Transfer
GSS-APIv2 provides functionality that 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, the GSSContext interface provides
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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 recreate
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.
4.7. 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.
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5. 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 that 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.
5.1. 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 8.
5.2. Provider Framework
Java security APIs 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 [RFC4121], and another might contain components
to support the Simple Public-Key GSS-API Mechanism (SPKM) [RFC2025].
By delegating mechanism-specific functionality to the components
obtained from providers, the GSS-API can be extended to support an
arbitrary list of mechanisms.
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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 an 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.
5.3. Integer Types
All numeric values are declared as the "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.
5.4. Opaque Data Types
Java byte arrays are used to represent opaque data types that are
consumed and produced by the GSS-API in the form of tokens. Java
arrays contain a length field that enables the users to easily
determine their size. The language has automatic garbage collection
that alleviates the need by developers to release memory and
simplifies buffer ownership issues.
5.5. 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.
5.6. 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.
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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 object. 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.
5.7. Object Identifier Sets
The Java bindings represent Object Identifier 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 [RFC2743], the
Oid class includes a method that 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 memory management issues of
the C counterpart.
Whenever a default value for an Object Identifier set is required, a
"null" value can be used. Please consult the detailed method
description for details.
5.8. 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 [RFC2744]:
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
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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 of a 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.
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,
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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 a GSSCredential object representing a specific
identity.
5.9. 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 that 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 and might not match the initiator-requested values. If any
retrieved attribute does not match the desired value but it is
necessary for the application protocol, the application SHOULD
destroy the security context and not use it for application traffic.
Otherwise, at this point, the context can be used by the application
to apply cryptographic services to its data.
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5.10. 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.
5.11. Inter-process 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 inter-process 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 inter-process
tokens are protected in transit and transferred only to processes
that are trustworthy. An inter-process token is represented using a
byte array emitted from the export method of the GSSContext
interface. The receiver of the inter-process token would initialize
a 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.
5.12. Error Reporting
RFC 2743 [RFC2743] defined the usage of major and minor status values
for the signaling of GSS-API errors. The major code, also called the
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. The GSSException class
also contains methods to obtain textual representations for both the
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major and minor values, which is equivalent to the functionality of
gss_display_status. A GSSException object MAY also include an output
token that SHOULD be sent to the peer.
If an exception is thrown during context establishment, the context
negotiation has failed and the GSSContext object MUST be abandoned.
If it is thrown in a per-message call, the context MAY remain useful.
5.12.1. 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.
A GSSException object, along with providing the functionality for
setting 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:
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Table: GSS Status Codes
+----------------------+-------+------------------------------------+
| Name | Value | Meaning |
+----------------------+-------+------------------------------------+
| BAD_BINDINGS | 1 | Incorrect channel bindings were |
| | | supplied. |
| BAD_MECH | 2 | An unsupported mechanism was |
| | | requested. |
| BAD_NAME | 3 | An invalid name was supplied. |
| BAD_NAMETYPE | 4 | A supplied name was of an |
| | | unsupported type. |
| BAD_STATUS | 5 | An invalid status code was |
| | | supplied. |
| BAD_MIC | 6 | A token had an invalid MIC. |
| CONTEXT_EXPIRED | 7 | The context has expired. |
| CREDENTIALS_EXPIRED | 8 | The referenced credentials have |
| | | expired. |
| DEFECTIVE_CREDENTIAL | 9 | A supplied credential was invalid. |
| DEFECTIVE_TOKEN | 10 | A supplied token was invalid. |
| FAILURE | 11 | Miscellaneous failure, unspecified |
| | | at the GSS-API level. |
| NO_CONTEXT | 12 | Invalid context has been supplied. |
| NO_CRED | 13 | No credentials were supplied, or |
| | | the credentials were unavailable |
| | | or inaccessible. |
| BAD_QOP | 14 | The quality of protection (QOP) |
| | | requested could not be provided. |
| UNAUTHORIZED | 15 | The operation is forbidden by the |
| | | 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. |
+----------------------+-------+------------------------------------+
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The following four status codes (DUPLICATE_TOKEN, OLD_TOKEN,
UNSEQ_TOKEN, and GAP_TOKEN) are contained in a GSSException only if
detected during context establishment, in which case it is a fatal
error. (During per-message calls, these values are indicated as
supplementary information contained in the MessageProp object.) They
are:
+-----------------+-------+-----------------------------------------+
| Name | Value | Meaning |
+-----------------+-------+-----------------------------------------+
| DUPLICATE_TOKEN | 19 | The token was a duplicate of an earlier |
| | | version. |
| OLD_TOKEN | 20 | The token's validity period has |
| | | expired. |
| UNSEQ_TOKEN | 21 | A later token has already been |
| | | processed. |
| GAP_TOKEN | 22 | The expected token was not received. |
+-----------------+-------+-----------------------------------------+
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 [RFC2743].
5.12.2. 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.
5.12.3. 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 that 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. |
+------------------+------------------------------------------------+
A "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.
5.13. 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.
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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 to allow support for multiple
syntaxes for each supported namespace and to allow 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, the
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
namespace 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 the
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 MNs), and the names emitted by the GSSContext
interface's getSrcName and getTargName methods are always of this
type. Since some applications may require MNs without wanting to
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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.
However, applications SHOULD note that to avoid surprising behavior,
it is best to ensure that the names being compared are either both
mechanism names for the same mechanism or both internal names that
are not mechanism names. This holds whether the equals method is
used directly or the export method is used to generate byte strings
that are then compared byte-by-byte.
When used in large access control lists, the overhead of creating a
GSSName object on each name and invoking the equal method on each
name from the Access Control List (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 an 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
[RFC2743].
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
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same principal; the second determines 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 to how
GSSName implementations SHOULD behave and are not intended to be
specific requirements of how name 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.
5.14. 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 as well
as instances of InetAddress to specify the application data to be
used in the channel binding. 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 Message Integrity Code
(MIC) over this octet string and binds the MIC to the context
establishment token emitted by the 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.
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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 the setting of the
addressing information.
5.15. 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. Method overloading has also
been used as a technique to indicate default parameters.
6. 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 APIs, 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 [RFC2743]
functionality implemented by each of the classes. Detailed
description of these classes and their methods is presented in
Section 7.
6.1. 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.
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.
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This class contains equivalents of the following RFC 2743 [RFC2743]
routines:
+----------------------------+-------------------------+------------+
| RFC 2743 Routine | Function | Section(s) |
+----------------------------+-------------------------+------------+
| gss_import_name | Create an internal name | 7.1.5 - |
| | from the supplied | 7.1.8 |
| | information. | |
| gss_acquire_cred | Acquire credential for | 7.1.9 - |
| | use. | 7.1.11 |
| gss_import_sec_context | Create a previously | 7.1.14 |
| | exported context. | |
| gss_indicate_mechs | List the mechanisms | 7.1.2 |
| | supported by this GSS- | |
| | API implementation. | |
| gss_inquire_mechs_for_name | List the mechanisms | 7.1.4 |
| | supporting the | |
| | specified name type. | |
| gss_inquire_names_for_mech | List the name types | 7.1.3 |
| | supported by the | |
| | specified mechanism. | |
+----------------------------+-------------------------+------------+
6.2. 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 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:
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+-----------------------+------------------------------+------------+
| RFC 2743 Routine | Function | Section(s) |
+-----------------------+------------------------------+------------+
| gss_display_name | Convert internal name | 7.2.6 |
| | representation to text | |
| | format. | |
| gss_compare_name | Compare two internal names. | 7.2.2, |
| | | 7.2.3 |
| gss_release_name | Release resources associated | N/A |
| | with the internal name. | |
| gss_canonicalize_name | Convert an internal name to | 7.2.4 |
| | a mechanism name. | |
| gss_export_name | Convert a mechanism name to | 7.2.5 |
| | export format. | |
| gss_duplicate_name | Create a copy of the | N/A |
| | internal 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 across threads.
6.3. 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 | 7.3.11 |
| | incrementally. | |
| gss_inquire_cred | Obtain information about | 7.3.3 - |
| | credential. | 7.3.10 |
| gss_inquire_cred_by_mech | Obtain per-mechanism | 7.3.4 - |
| | information about a | 7.3.9 |
| | credential. | |
| gss_release_cred | Dispose of credentials | 7.3.2 |
| | after use. | |
+--------------------------+---------------------------+------------+
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6.4. 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
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 | 7.4.2 |
| | security context with a | |
| | peer. | |
| gss_accept_sec_context | Accept a security context | 7.4.3 |
| | initiated by a peer. | |
| gss_delete_sec_context | Destroy a security context. | 7.4.5 |
| gss_context_time | Obtain remaining context | 7.4.30 |
| | time. | |
| gss_inquire_context | Obtain context | 7.4.21 - |
| | characteristics. | 7.4.35 |
| gss_wrap_size_limit | Determine token-size limit | 7.4.6 |
| | for gss_wrap. | |
| gss_export_sec_context | Transfer security context | 7.4.11 |
| | to another process. | |
| gss_get_mic | Calculate a cryptographic | 7.4.9 |
| | Message Integrity Code | |
| | (MIC) for a message. | |
| gss_verify_mic | Verify integrity on a | 7.4.10 |
| | received message. | |
| gss_wrap | Attach a MIC to a message | 7.4.7 |
| | and optionally encrypt the | |
| | message content. | |
| gss_unwrap | Obtain a previously wrapped | 7.4.8 |
| | application message | |
| | verifying 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 [RFC2743].
GSSContext does offer the functionality of destroying the locally
stored context information.
6.5. 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.
6.6. 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 | 7.8.5, 7.8.6, |
| | representation of error | 7.8.9, 7.8.10 |
| | codes. | |
+--------------------+----------------------------+-----------------+
6.7. 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 | 7.7.5 |
| | OID is part of a set of OIDs. | |
+-------------------------+-------------------------------+---------+
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6.8. 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
to 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.
7. 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.
7.1. 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 name types 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, whether the constructor is 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 the 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.
When neither of the methods is called, the implementation SHOULD
choose a default provider for each mechanism it supports.
7.1.1. getInstance
public static GSSManager getInstance()
Returns the default GSSManager implementation.
7.1.2. getMechs
public abstract Oid[] getMechs()
Returns an array of Oid objects indicating the mechanisms available
to GSS-API callers. A "null" value is returned when no mechanisms
are available (an example of this would be when mechanisms are
dynamically configured, and currently no mechanisms are installed).
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7.1.3. getNamesForMech
public abstract Oid[] getNamesForMech(Oid mech)
throws GSSException
Returns name type OIDs supported by the specified mechanism.
Parameters:
mech The Oid object for the mechanism to query.
7.1.4. 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.
7.1.5. 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 does not support multiple mechanisms.
Parameters:
nameStr The string representing a printable form of the
name to create.
nameType The OID specifying the namespace of the printable
name is 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. The
"null" value can be used to specify that a
mechanism-specific default printable syntax
SHOULD be assumed by each mechanism that examines
nameStr.
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7.1.6. 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 a 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. The "null" value can be used to
specify that a mechanism-specific default syntax
SHOULD be assumed by each mechanism that examines
the byte array.
7.1.7. 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 a 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 Section 7.1.5 and also the
GSSName.canonicalize() described in Section 7.2.4.
Parameters:
nameStr The string representing a printable form of the
name to create.
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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. The
"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.
7.1.8. createName
public abstract GSSName 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 Section 7.1.6 and also the
GSSName.canonicalize() described in Section 7.2.4.
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. The "null" value 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.
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7.1.9. 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.INITIATE_AND_ACCEPT(0),
GSSCredential.INITIATE_ONLY(1), or
GSSCredential.ACCEPT_ONLY(2)
7.1.10. 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.
usage The intended usage for this credential object.
The value of this parameter MUST be one of:
GSSCredential.INITIATE_AND_ACCEPT(0),
GSSCredential.INITIATE_ONLY(1), or
GSSCredential.ACCEPT_ONLY(2)
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7.1.11. 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.INITIATE_AND_ACCEPT(0),
GSSCredential.INITIATE_ONLY(1), or
GSSCredential.ACCEPT_ONLY(2)
7.1.12. 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 the 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.
7.1.13. createContext
public abstract GSSContext createContext(GSSCredential myCred)
throws GSSException
Factory method for creating a context on the acceptor's 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.
7.1.14. createContext
public abstract GSSContext createContext(byte[] interProcessToken)
throws GSSException
Factory method for importing 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.
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7.1.15. addProviderAtFront
public abstract void addProviderAtFront(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 ahead of all
others when support is desired for the given mechanism. When a value
of "null" is used instead of an Oid object 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.
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7.1.15.1. addProviderAtFront Example Code
Suppose an application desired that provider A always be checked
first when any mechanism is needed, it would call:
<CODE BEGINS>
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);
<CODE ENDS>
Now if it also desired that the mechanism of OID m1 always be
obtained from provider B before the previous set A was checked, it
would call:
<CODE BEGINS>
mgr.addProviderAtFront(B, m1);
<CODE ENDS>
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:
<CODE BEGINS>
mgr.addProviderAtFront(B, null)
<CODE ENDS>
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:
<CODE BEGINS>
mgr.addProviderAtFront(A, m3)
<CODE ENDS>
does not subsume the previous setting of (A, null), and the list will
effectively become {(A, m3), (B, null), (A, null), ...}
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7.1.16. addProviderAtEnd
public abstract void 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 object 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.
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.
7.1.16.1. addProviderAtEnd 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:
<CODE BEGINS>
GSSManager mgr = GSSManager.getInstance();
mgr.addProviderAtEnd(A, m1);
<CODE ENDS>
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Now, if it also desired that provider B be checked for all mechanisms
after all configured providers have been checked, it would then call:
<CODE BEGINS>
mgr.addProviderAtEnd(B, null);
<CODE ENDS>
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:
<CODE BEGINS>
mgr.addProviderAtEnd(B, m2)
<CODE ENDS>
then the previous setting with the pair (B, null) subsumes this;
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:
<CODE BEGINS>
mgr.addProviderAtEnd(A, null)
<CODE ENDS>
is not subsumed by the previous setting of (A, m1), and the list will
effectively become {..., (A, m1), (B, null), (A, null)}.
7.1.17. Example Code
<CODE BEGINS>
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());
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mgr.addProviderAtFront(p, krb);
mgr.addProviderAtFront(p, spkm1);
// What name types does this spkm implementation support?
Oid[] nameTypes = mgr.getNamesForMech(spkm1);
<CODE ENDS>
7.2. public interface GSSName
This interface encapsulates a single GSS-API principal entity.
Different name formats and their definitions are identified with
Universal OIDs. The format of the names can be derived based on the
unique OID of its namespace type.
7.2.1. 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: { iso(1) member-body(2) United
States(840) mit(113554) infosys(1) gssapi(2) generic(1)
service_name(4) }
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) }
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public static final Oid NT_ANONYMOUS
Name type for representing an anonymous entity. It represents the
following value: { iso(1), org(3), dod(6), internet(1), security(5),
nametypes(6), gss-anonymous-name(3) }
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: { iso(1), org(3), dod(6),
internet(1), security(5), nametypes(6), gss-api-exported-name(4) }
7.2.2. 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 with which to compare.
7.2.3. equals
public boolean equals(Object another)
A variation of the equals method, described in Section 7.2.2, that is
provided to override the Object.equals() method that the implementing
class will inherit. The behavior is exactly the same as that in
Section 7.2.2 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 with which to compare.
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7.2.4. canonicalize
public GSSName canonicalize(Oid mech) throws GSSException
Creates an MN from an arbitrary internal name. This is equivalent to
using the factory methods described in Sections 7.1.7 or 7.1.8 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.
7.2.5. export
public byte[] export() throws GSSException
Returns a canonical contiguous byte representation of an 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 [RFC2743].
7.2.6. 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.
7.2.7. 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.
7.2.8. isAnonymous
public boolean isAnonymous()
Tests if this name object represents an anonymous entity. Returns
"true" if this is an anonymous name.
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7.2.9. 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 [RFC2743].
7.2.10. Example Code
Included below are code examples utilizing the GSSName interface.
The code below creates a GSSName, converts it to an MN, performs a
comparison, obtains a printable representation of the name, exports
it, and then re-imports to obtain a new GSSName.
<CODE BEGINS>
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 the name
byte[] exportName = mechName.export();
// create a new name object from the exported buffer
GSSName newName = mgr.createName(exportName,
GSSName.NT_EXPORT_NAME);
<CODE ENDS>
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7.3. 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
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 that 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.
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7.3.1. 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. The value of this constant is 0.
public static final int INITIATE_ONLY
Credential usage flag requesting that it be able to be used for
context initiation only. The value of this constant is 1.
public static final int ACCEPT_ONLY
Credential usage flag requesting that it be able to be used for
context acceptance only. The value of this constant is 2.
public static final int DEFAULT_LIFETIME
A lifetime constant representing the default credential lifetime.
The value of this constant is 0.
public static final int INDEFINITE_LIFETIME
A lifetime constant representing indefinite credential lifetime. The
value of this constant is the maximum integer value in Java --
Integer.MAX_VALUE.
7.3.2. 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.
7.3.3. getName
public GSSName getName() throws GSSException
Retrieves the name of the entity that the credential asserts.
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7.3.4. 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
Section 7.3.3.
Parameters:
mechOID The mechanism for which information should be
returned.
7.3.5. 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.
7.3.6. getRemainingInitLifetime
public int getRemainingInitLifetime(Oid mech) throws GSSException
Returns the remaining lifetime in 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.
7.3.7. getRemainingAcceptLifetime
public int getRemainingAcceptLifetime(Oid mech) throws GSSException
Returns the remaining lifetime in 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.
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Parameters:
mechOID The mechanism for which information should be
returned.
7.3.8. getUsage
public int getUsage() throws GSSException
Returns the credential usage flag as a union over all mechanisms.
The return value will be one of GSSCredential.INITIATE_AND_ACCEPT(0),
GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2).
Specifically, GSSCredential.INITIATE_AND_ACCEPT(0) SHOULD be returned
as long as there exists one credential element allowing context
initiation and one credential element allowing context acceptance.
These two credential elements are not necessarily the same one, nor
do they need to use the same mechanism(s).
7.3.9. getUsage
public int getUsage(Oid mechOID) throws GSSException
Returns the credential usage flag for the specified mechanism only.
The return value will be one of GSSCredential.INITIATE_AND_ACCEPT(0),
GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2).
Parameters:
mechOID The mechanism for which information should be
returned.
7.3.10. getMechs
public Oid[] getMechs() throws GSSException
Returns an array of mechanisms supported by this credential.
7.3.11. 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.
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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 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 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.
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.INITIATE_AND_ACCEPT(0),
GSSCredential.INITIATE_ONLY(1), or
GSSCredential.ACCEPT_ONLY(2)
7.3.12. 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, or "false"
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otherwise. (Note that the Java language specification [JLS] 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.
7.3.13. 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.
<CODE BEGINS>
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.INDEFINITE_LIFETIME,
(Oid[])null,
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();
<CODE ENDS>
7.4. public interface GSSContext
This interface encapsulates the GSS-API security context and provides
the security services (wrap, unwrap, getMIC, and 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
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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.
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 where the
exception may contain an output token that should be sent to the peer
for debugging or informational purpose. 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 that 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.
7.4.1. Static Constants
public static final int DEFAULT_LIFETIME
A lifetime constant representing the default context lifetime. The
value of this constant is 0.
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public static final int INDEFINITE_LIFETIME
A lifetime constant representing indefinite context lifetime. The
value of this constant is the maximum integer value in Java --
Integer.MAX_VALUE.
7.4.2. initSecContext
public byte[] initSecContext(byte[] inputBuf, int offset, int len)
throws GSSException
Called by the context initiator to start the context creation
process. This method MAY return an output token that the application
will need to send to the peer for processing by the accept call. 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 will return a token for the
peer and isEstablished() will 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.
A GSSException will be thrown if the call fails. Users SHOULD call
its getOutputToken() method to find out if there is a token that can
be sent to the acceptor to communicate the reason for the error.
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).
7.4.3. acceptSecContext
public byte[] acceptSecContext(byte[] inTok, int offset, int len)
throws GSSException
Called by the context acceptor upon receiving a token from the peer.
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This method MAY return an output token that the application will need
to send to the peer for further processing by the init call.
The "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.
Note that it is possible that acceptSecContext() will return a token
for the peer and isEstablished() will 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.
A GSSException will be thrown if the call fails. Users SHOULD call
its getOutputToken() method to find out if there is a token that can
be sent to the initiator to communicate the reason for the error.
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).
7.4.4. 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.
7.4.5. 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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7.4.6. 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.
7.4.7. 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. 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 that 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 actual privacy state that
was applied to the message by the underlying
mechanism.
7.4.8. 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. 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.
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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:
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 Section 5.12.3, stating whether the token was
a duplicate, old, out of sequence, or arriving
after a gap.
7.4.9. 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.
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 over which to generate MIC.
offset The offset within the inMsg where the token
begins.
len The length of the token within the inMsg
(starting at the offset).
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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.
7.4.10. 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.
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 over which to verify the
cryptographic MIC.
msgOffset The offset within the inMsg where the message
begins.
msgLen The length of the message within the inMsg
(starting at the offset).
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msgProp Upon return from the method, this object will
contain the applied QOP and supplementary
information, described in Section 5.12.3, stating
whether the token was a duplicate, old, out of
sequence, or arriving after a gap. The
confidentiality state will be set to "false".
7.4.11. 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 inter-
process token that, 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
inter-process 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 inter-process token MAY contain security-sensitive information
(for example, cryptographic keys). While mechanisms are encouraged
either to avoid placing such sensitive information within inter-
process 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 inter-
process token and ensure that any process to which the token is
transferred is trustworthy.
7.4.12. 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.
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Parameters:
state Boolean representing if mutual authentication
should be requested during context establishment.
7.4.13. 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.
7.4.14. 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.
7.4.15. 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.
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7.4.16. 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.
Parameters:
state Boolean representing if anonymity support is
requested.
7.4.17. 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.
7.4.18. 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.
7.4.19. 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.
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Parameters:
lifetime The desired context lifetime in seconds.
7.4.20. 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.
7.4.21. 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.
7.4.22. 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.
7.4.23. 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.
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7.4.24. 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;
otherwise, it will indicate the actual state over the established
context.
7.4.25. 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.
7.4.26. 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.
7.4.27. 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.
7.4.28. 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.
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7.4.29. 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.
7.4.30. 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.
7.4.31. 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.
7.4.32. 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.
7.4.33. 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 a negotiated mechanism
case.
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7.4.34. 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.
7.4.35. 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.
7.4.36. 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.
<CODE BEGINS>
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);
// 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];
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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());
// If the exception contains an output token,
// it should be sent to the acceptor.
byte[] outTok = e.getOutputToken();
if (outTok != null) {
sendToken(outTok);
}
return;
}
// 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 ...
MessageProp mProp = new MessageProp(0, true);
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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();
<CODE ENDS>
7.5. 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. A QOP is an integer value defined by an
mechanism.
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.
7.5.1. Constructors
public MessageProp(boolean privState)
Constructor that 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 that sets the values for the QOP and privacy state.
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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.
7.5.2. getQOP
public int getQOP()
Retrieves the QOP value.
7.5.3. getPrivacy
public boolean getPrivacy()
Retrieves the privacy state.
7.5.4. getMinorStatus
public int getMinorStatus()
Retrieves the minor status that the underlying mechanism might have
set.
7.5.5. 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.
7.5.6. 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.
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7.5.7. setPrivacy
public void setPrivacy(boolean privState)
Sets the privacy state.
Parameters:
privState The privacy state to set.
7.5.8. isDuplicateToken
public boolean isDuplicateToken()
Returns "true" if this is a duplicate of an earlier token.
7.5.9. isOldToken
public boolean isOldToken()
Returns "true" if the token's validity period has expired.
7.5.10. isUnseqToken
public boolean isUnseqToken()
Returns "true" if a later token has already been processed.
7.5.11. isGapToken
public boolean isGapToken()
Returns "true" if an expected per-message token was not received.
7.5.12. 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.
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Parameters:
duplicate "true" if the token was a duplicate of an earlier
token; otherwise, "false".
old "true" if the token's validity period has
expired; otherwise, "false".
unseq "true" if a later token has already been
processed; otherwise, "false".
gap "true" if one or more predecessor tokens have not
yet been successfully processed; otherwise,
"false".
minorStatus The integer minor status code that the underlying
mechanism wants to set.
minorString The textual representation of the minorStatus
value.
7.6. 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.
7.6.1. 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 that the
application does not want to specify.
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Parameters:
initAddr The address of the context initiator. The "null"
value can be supplied to indicate that the
application does not want to set this value.
acceptAddr The address of the context acceptor. The "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. The "null" value can be
supplied to indicate that the application does
not want to set this value.
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.
7.6.2. getInitiatorAddress
public InetAddress getInitiatorAddress()
Returns the initiator's address for this channel binding. "null" is
returned if the address has not been set.
7.6.3. getAcceptorAddress
public InetAddress getAcceptorAddress()
Returns the acceptor's address for this channel binding. "null" is
returned if the address has not been set.
7.6.4. 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.
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7.6.5. 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 with which to compare.
7.7. public class Oid
This class represents Universal 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
[ISOIEC-8824] and ISOIEC-8825 [ISOIEC-8825]. For example, the OID
representation of the 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.
7.7.1. 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 [ISOIEC-8824] and ISOIEC-8825
[ISOIEC-8825]. This method is identical in functionality to its byte
array counterpart.
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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 [ISOIEC-8824] and ISOIEC-8825
[ISOIEC-8825]. This method is identical in functionality to its byte
array counterpart.
Parameters:
derOid Byte array storing a DER-encoded OID.
7.7.2. 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").
7.7.3. equals
public boolean equals(Object Obj)
Returns "true" if the two Oid objects represent the same OID value.
(Note that the Java language specification [JLS] 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 with which to compare.
7.7.4. getDER
public byte[] getDER()
Returns the full ASN.1 DER encoding for this Oid object, which
includes the tag and length.
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7.7.5. 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.
7.8. 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 implementors 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. This exception MAY also include an
output token that SHOULD be sent to the peer. For example, when an
initSecContext call fails due to a fatal error, the mechanism MAY
define an error token that SHOULD be sent to the peer for debugging
or informational purposes. All Java GSS-API methods are declared
throwing this exception.
All implementations are encouraged to use the Java
internationalization techniques to provide local translations of the
message strings.
7.8.1. 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. The value of this constant is 1.
public static final int BAD_MECH
Unsupported mechanism requested error. The value of this constant is
2.
public static final int BAD_NAME
Invalid name provided error. The value of this constant is 3.
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public static final int BAD_NAMETYPE
Name of unsupported type provided error. The value of this constant
is 4.
public static final int BAD_STATUS
Invalid status code error - this is the default status value. The
value of this constant is 5.
public static final int BAD_MIC
Token had invalid integrity check error. The value of this constant
is 6.
public static final int CONTEXT_EXPIRED
Specified security context expired error. The value of this constant
is 7.
public static final int CREDENTIALS_EXPIRED
Expired credentials detected error. The value of this constant is 8.
public static final int DEFECTIVE_CREDENTIAL
Defective credential error. The value of this constant is 9.
public static final int DEFECTIVE_TOKEN
Defective token error. The value of this constant is 10.
public static final int FAILURE
General failure, unspecified at GSS-API level. The value of this
constant is 11.
public static final int NO_CONTEXT
Invalid security context error. The value of this constant is 12.
public static final int NO_CRED
Invalid credentials error. The value of this constant is 13.
public static final int BAD_QOP
Unsupported QOP value error. The value of this constant is 14.
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public static final int UNAUTHORIZED
Operation unauthorized error. The value of this constant is 15.
public static final int UNAVAILABLE
Operation unavailable error. The value of this constant is 16.
public static final int DUPLICATE_ELEMENT
Duplicate credential element requested error. The value of this
constant is 17.
public static final int NAME_NOT_MN
Name contains multi-mechanism elements error. The value of this
constant is 18.
public static final int DUPLICATE_TOKEN
The token was a duplicate of an earlier token. This is contained in
an exception only when detected during context establishment, in
which case it is considered a fatal error. (Non-fatal supplementary
codes are indicated via the MessageProp object.) The value of this
constant is 19.
public static final int OLD_TOKEN
The token's validity period has expired. This is contained in an
exception only when detected during context establishment, in which
case it is considered a fatal error. (Non-fatal supplementary codes
are indicated via the MessageProp object.) The value of this
constant is 20.
public static final int UNSEQ_TOKEN
A later token has already been processed. This is contained in an
exception only when detected during context establishment, in which
case it is considered a fatal error. (Non-fatal supplementary codes
are indicated via the MessageProp object.) The value of this
constant is 21.
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public static final int GAP_TOKEN
An expected per-message token was not received. This is contained in
an exception only when detected during context establishment, in
which case it is considered a fatal error. (Non-fatal supplementary
codes are indicated via the MessageProp object.) The value of this
constant is 22.
7.8.2. Constructors
public GSSException(int majorCode)
Creates a GSSException object with a specified major code.
Calling this constructor is equivalent to calling
GSSException(majorCode, null, 0, null, null).
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.
Calling this constructor is equivalent to calling
GSSException(majorCode, null, minorCode, minorString, null).
public GSSException(int majorCode, String majorString,
int minorCode, String minorString,
byte[] outputToken)
Creates a GSSException object with the specified major code, major
code textual explanation, minor code, minor code textual explanation,
and an output token. This is a general-purpose constructor that can
be used to create any type of GSSException.
Parameters:
majorCode The GSS error code causing this exception to be
thrown.
majorString The textual explanation of the GSS error code.
If null is provided, a default explanation that
matches the majorCode will be set.
minorCode The mechanism error code causing this exception
to be thrown. Can be 0 if no mechanism error
code is available.
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minorString The textual explanation of the mechanism error
code. Can be null if no textual explanation is
available.
outputToken The output token that SHOULD be sent to the peer.
Can be null if no such token is available. It
MUST NOT be an empty array. When provided, the
array will be cloned to protect against
subsequent modifications.
7.8.3. getMajor
public int getMajor()
Returns the major code representing the GSS error code that caused
this exception to be thrown.
7.8.4. getMinor
public int getMinor()
Returns the mechanism error code that caused this exception. The
minor code is set by the underlying mechanism. The value of 0
indicates that the mechanism error code is not set.
7.8.5. getMajorString
public String getMajorString()
Returns a string explaining the GSS major error code causing this
exception to be thrown.
7.8.6. getMinorString
public String getMinorString()
Returns a string explaining the mechanism-specific error code. "null"
will be returned when no string explaining the mechanism error code
has been set.
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7.8.7. getOutputToken
public byte[] getOutputToken
Returns the output token in a new byte array.
If the method (for example, GSSContext#initSecContext) that throws
this GSSException needs to generate an output token that SHOULD be
sent to the peer, that token will be stored in this GSSException and
can be retrieved with this method.
The return value MUST be null if no such token is generated. It MUST
NOT be an empty byte array.
7.8.8. 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.
Parameters:
minorCode The mechanism-specific error code.
message A textual explanation of the mechanism error
code.
7.8.9. toString
public String toString()
Returns a textual representation of both the major and minor status
codes.
7.8.10. 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.
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8. Sample Applications
8.1. Simple GSS Context Initiator
<CODE BEGINS>
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 RFC 8353.
*
*
* 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 (i.e., server)
private GSSCredential clientCred = null;
private GSSContext context = null;
private Oid mech; // underlying mechanism to use
private GSSManager mgr = GSSManager.getInstance();
...
...
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 */,
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GSSCredential.INITIATE_ONLY /* init context */);
print("GSSCredential created for " +
clientCred.getName().toString());
print("Credential lifetime (sec)=" +
clientCred.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,
GSSName.NT_HOSTBASED_SERVICE);
context = mgr.createContext(peer, mech, clientCred,
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();
}
peer = context.getTargName();
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print("Security context established with " + peer +
" using underlying mechanism " + mech.toString());
} catch (GSSException e) {
print("GSS-API error during context establishment: "
+ e.getMessage());
// If the exception contains an output token,
// it should be sent to the acceptor.
byte[] outTok = e.getOutputToken();
if (outTok != null) {
writeGSSToken(outTok);
}
...
...
}
...
...
}
/**
* 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(true);
try {
/*
* 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);
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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.getTargName();
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());
...
...
}
...
...
} // end of doCommunication method
...
...
} // end of class SimpleClient
<CODE ENDS>
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8.2. Simple GSS Context Acceptor
<CODE BEGINS>
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() throws Exception {
...
...
mgr = GSSManager.getInstance();
name = mgr.createName(serviceName,
GSSName.NT_HOSTBASED_SERVICE);
cred = mgr.createCredential(name,
GSSCredential.INDEFINITE_LIFETIME,
(Oid[])null,
GSSCredential.ACCEPT_ONLY);
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// 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;
// Container for multiple input-output arguments to
// and from the per-message routines
// (i.e., wrap/unwrap).
MessageProp supplInfo = new MessageProp(true);
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);
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}
// 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());
// Now read the bytes sent by the client to be
// processed.
inToken = readGSSToken();
// Unwrap the message
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);
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// 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()
// If the exception contains an output token,
// it should be sent to the initiator.
byte[] outTok = e.getOutputToken();
if (outTok != null) {
writeGSSToken(outTok);
}
print("Abandoning security context.");
...
...
}
...
...
} // end of run method in ServerThread
} // end of inner class ServerThread
...
...
} // end of class SimpleServer
<CODE ENDS>
9. 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 Key
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Distribution Center (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 Java Virtual Machine
(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) 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) 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.)
10. IANA Considerations
This document has no IANA actions.
11. Changes since RFC 5653
This document has following changes:
1) New error token embedded in GSSException
There is a design flaw in the initSecContext and acceptSecContext
methods of the GSSContext class defined in "Generic Security
Service API Version 2: Java Bindings Update" [RFC5653].
The methods could either return a token (possibly null if no more
tokens are needed) when the call succeeds or throw a GSSException
if there is a failure, but NOT both. On the other hand, the
C-bindings of GSS-API [RFC2744] can return both; that is to say, a
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call to the GSS_Init_sec_context() function can return a major
status code, and at the same time, fill in the output_token
argument if there is one.
Without the ability to emit an error token when there is a
failure, a Java application has no mechanism to tell the other
side what the error is. For example, a "reject" NegTokenResp
token can never be transmitted for the SPNEGO mechanism [RFC4178].
While a Java method can never return a value and throw an
exception at the same time, we can embed the error token inside
the exception so that the caller has a chance to retrieve it.
This update adds a new GSSException constructor to include this
token inside a GSSException object and a getOutputToken() method
to retrieve the token. The specification for the initSecContext
and acceptSecContext methods are updated to describe the new
behavior. Various examples are also updated.
New JGSS programs SHOULD make use of this new feature, but it is
not mandatory. A program that intends to run with both old and
new GSS Java bindings can use reflection to check the availability
of this new method and call it accordingly.
2) Removing Stream-Based GSSContext Methods
The overloaded methods of GSSContext that use input and output
streams as the means to convey authentication and per-message
GSS-API tokens as described in Section 5.15 of RFC 5653 [RFC5653]
are removed in this update as the wire protocol should be defined
by an application and not a library. It's also impossible to
implement these methods correctly when the token has no self-
framing (where the end cannot be determined), or the library has
no knowledge of the token format (for example, as a bridge talking
to another GSS library). These methods include initSecContext
(Section 7.4.5 of RFC 5653 [RFC5653]), acceptSecContext
(Section 7.4.9 of RFC 5653 [RFC5653]), wrap (Section 7.4.15 of RFC
5653 [RFC5653]), unwrap (Section 7.4.17 of RFC 5653 [RFC5653]),
getMIC (Section 7.4.19 of RFC 5653 [RFC5653]), and verifyMIC
(Section 7.4.21 of RFC 5653 [RFC5653]).
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12. Changes since RFC 2853
This document has the following changes:
1) Major GSS Status Code Constant Values
RFC 2853 listed all the GSS status code values in two different
sections: Section 4.12.1 defined numeric values for them, and
Section 6.8.1 defined them as static constants in the GSSException
class without assigning any values. Due to an inconsistent
ordering between these two sections, all of the GSS major status
codes resulted in misalignment and a subsequent disagreement
between deployed implementations.
This document defines the numeric values of the GSS status codes
in both sections, while maintaining the original ordering from
Section 6.8.1 of RFC 2853 [RFC2853], and it obsoletes the GSS
status code values defined in Section 4.12.1. The relevant
sections in this document are Sections 5.12.1 and 7.8.1.
2) GSS Credential Usage Constant Values
RFC 2853, Section 6.3.2 defines static constants for the
GSSCredential usage flags. However, the values of these constants
were not defined anywhere in RFC 2853 [RFC2853].
This document defines the credential usage values in
Section 7.3.1. The original ordering of these values from
Section 6.3.2 of RFC 2853 [RFC2853] is maintained.
3) GSS Host-Based Service Name
RFC 2853 [RFC2853], Section 6.2.2 defines the static constant for
the GSS host-based service OID NT_HOSTBASED_SERVICE, using a
deprecated OID value.
This document updates the NT_HOSTBASED_SERVICE OID value in
Section 7.2.1 to be consistent with the C-bindings in RFC 2744
[RFC2744].
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13. References
13.1. Normative References
[RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism
(SPKM)", RFC 2025, DOI 10.17487/RFC2025, October 1996,
<https://www.rfc-editor.org/info/rfc2025>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743,
DOI 10.17487/RFC2743, January 2000,
<https://www.rfc-editor.org/info/rfc2743>.
[RFC2744] Wray, J., "Generic Security Service API Version 2 :
C-bindings", RFC 2744, DOI 10.17487/RFC2744, January 2000,
<https://www.rfc-editor.org/info/rfc2744>.
[RFC2853] Kabat, J. and M. Upadhyay, "Generic Security Service API
Version 2 : Java Bindings", RFC 2853,
DOI 10.17487/RFC2853, June 2000,
<https://www.rfc-editor.org/info/rfc2853>.
[RFC4121] Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
Version 5 Generic Security Service Application Program
Interface (GSS-API) Mechanism: Version 2", RFC 4121,
DOI 10.17487/RFC4121, July 2005,
<https://www.rfc-editor.org/info/rfc4121>.
[RFC4178] Zhu, L., Leach, P., Jaganathan, K., and W. Ingersoll, "The
Simple and Protected Generic Security Service Application
Program Interface (GSS-API) Negotiation Mechanism",
RFC 4178, DOI 10.17487/RFC4178, October 2005,
<https://www.rfc-editor.org/info/rfc4178>.
[RFC5653] Upadhyay, M. and S. Malkani, "Generic Security Service API
Version 2: Java Bindings Update", RFC 5653,
DOI 10.17487/RFC5653, August 2009,
<https://www.rfc-editor.org/info/rfc5653>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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13.2. Informative References
[ISOIEC-8824]
International Organization for Standardization,
"Information technology -- Abstract Syntax Notation One
(ASN.1): Specification of basic notation", ISO/
IEC 8824-1:2014, November 2015,
<https://www.iso.org/standard/68350.html>.
[ISOIEC-8825]
International Organization for Standardization,
"Information technology -- ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ISO/IEC 8825-1:2015, November 2015,
<https://www.iso.org/standard/68345.html>.
[JLS] Gosling, J., Joy, B., Steele, G., Bracha, G., Buckley, A.,
and D. Smith, "The Java Language Specification", Java SE
10 Edition, February 2018,
<https://docs.oracle.com/javase/specs/jls/se10/html/
index.html>.
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Acknowledgments
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 Greg Hudson, Benjamin Kaduk, Joe Salowey
and Michael Smith for many insightful ideas and suggestions that have
contributed to this document.
Authors' Addresses
Mayank D. Upadhyay
Google Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States of America
Email: m.d.upadhyay+ietf@gmail.com
Seema Malkani
ActivIdentity Corp.
6623 Dumbarton Circle
Fremont, California 94555
United States of America
Email: Seema.Malkani@gmail.com
Weijun Wang
Oracle
Building No. 24, Zhongguancun Software Park
Beijing 100193
China
Email: weijun.wang@oracle.com
Upadhyay, et al. Standards Track [Page 96]
ERRATA
