Internet DRAFT - draft-ietf-kitten-gssapi-csharp-bindings
draft-ietf-kitten-gssapi-csharp-bindings
NETWORK WORKING GROUP J. C. Luciani
INTERNET-DRAFT Novell, Inc.
Expires: April 8, 2006 November 8, 2005
GSS_API V2: C# Bindings
draft-ietf-kitten-gssapi-csharp-bindings-00.txt
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Abstract
The Generic Security Services Application Program Interface (GSS-API)
offers application programmers uniform access to security services
atop a variety of underlying cryptographic mechanisms. This document
specifies the C# language bindings for GSS-API which is described at
a language independent conceptual level in RFC 2743 [RFC2743].
The GSS-API C# bindings were designed to emulate the Java bindings as
defined in RFC 2853 [RFC2853].
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Table of Contents
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. GSS-API Operational Paradigm. . . . . . . . . . . . . . . . . . . . 6
3. Additional Controls . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Delegation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Mutual Authentication . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Replay and Out-of-Sequence Detection. . . . . . . . . . . . . . 10
3.4. Anonymous Authentication. . . . . . . . . . . . . . . . . . . . 11
3.5. Confidentiality . . . . . . . . . . . . . . . . . . . . . . . . 12
3.6. Inter-process Context Transfer. . . . . . . . . . . . . . . . . 12
3.7. The Use of Incomplete Contexts. . . . . . . . . . . . . . . . . 13
4. C# GSS-API Overview . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Object Identifiers. . . . . . . . . . . . . . . . . . . . . . . 14
4.2. Object Identifier Sets. . . . . . . . . . . . . . . . . . . . . 14
4.3. Credentials . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.4. Contexts. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.5. Authentication Tokens . . . . . . . . . . . . . . . . . . . . . 17
4.6. Interprocess Tokens . . . . . . . . . . . . . . . . . . . . . . 17
4.7. Error Reporting . . . . . . . . . . . . . . . . . . . . . . . . 17
4.7.1. GSS Status Codes. . . . . . . . . . . . . . . . . . . . . . . 18
4.7.2. Mechanism-specific Codes. . . . . . . . . . . . . . . . . . . 20
4.7.3. Suplementary Status Codes . . . . . . . . . . . . . . . . . . 20
4.8. Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.9. Channel Bindings. . . . . . . . . . . . . . . . . . . . . . . . 23
5. Introduction to GSS-API Classes and Interfaces. . . . . . . . . . 24
5.1. GSSManager Class. . . . . . . . . . . . . . . . . . . . . . . . 24
5.2. GSSName Interface . . . . . . . . . . . . . . . . . . . . . . . 25
5.3. GSSCredential Interface . . . . . . . . . . . . . . . . . . . . 25
5.4. GSSContext Interface. . . . . . . . . . . . . . . . . . . . . . 26
5.5. MessageProp Class . . . . . . . . . . . . . . . . . . . . . . . 27
5.6. GSSException Class. . . . . . . . . . . . . . . . . . . . . . . 27
5.7. Oid Class . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.8. ChannelBinding Class. . . . . . . . . . . . . . . . . . . . . . 27
5.9. GSSConstants Class. . . . . . . . . . . . . . . . . . . . . . . 28
5.10. GSSNameTypes Class . . . . . . . . . . . . . . . . . . . . . . 28
5.11. GSSCredentialUsage Enumeration . . . . . . . . . . . . . . . . 28
6. Detailed GSS-API Description. . . . . . . . . . . . . . . . . . . 28
6.1. public abstract class GSSManager. . . . . . . . . . . . . . . . 28
6.1.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.2. getInstance . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.3. getMechs. . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.4. getNamesForMech . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.5. getMechsForName . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.6. createName. . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1.7. createName. . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1.8. createName. . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.1.9. createName. . . . . . . . . . . . . . . . . . . . . . . . . . 32
6.1.10. createCredential . . . . . . . . . . . . . . . . . . . . . . 32
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6.1.11. createCredential . . . . . . . . . . . . . . . . . . . . . . 33
6.1.12. createCredential . . . . . . . . . . . . . . . . . . . . . . 33
6.1.13. createContext. . . . . . . . . . . . . . . . . . . . . . . . 34
6.1.14. createContext. . . . . . . . . . . . . . . . . . . . . . . . 35
6.1.15. createContext. . . . . . . . . . . . . . . . . . . . . . . . 35
6.2. public class GSSConstants . . . . . . . . . . . . . . . . . . . 35
6.2.1. DEFAULT_LIFETIME. . . . . . . . . . . . . . . . . . . . . . . 35
6.2.2. INDEFINITE_LIFETIME . . . . . . . . . . . . . . . . . . . . . 36
6.3. public class GSSNameTypes . . . . . . . . . . . . . . . . . . . 36
6.3.1. NT_HOSTBASED_SERVICE. . . . . . . . . . . . . . . . . . . . . 36
6.3.2. NT_USER_NAME. . . . . . . . . . . . . . . . . . . . . . . . . 36
6.3.3. NT_MACHINE_UID_NAME . . . . . . . . . . . . . . . . . . . . . 36
6.3.4. NT_STRING_UID_NAME. . . . . . . . . . . . . . . . . . . . . . 37
6.3.5. NT_ANONYMOUS. . . . . . . . . . . . . . . . . . . . . . . . . 37
6.3.6. NT_EXPORT_NAME. . . . . . . . . . . . . . . . . . . . . . . . 37
6.4. public interface GSSName. . . . . . . . . . . . . . . . . . . . 38
6.4.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . . 38
6.4.2. Equals. . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6.4.3. Equals. . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6.4.4. canonicalize. . . . . . . . . . . . . . . . . . . . . . . . . 39
6.4.5. export. . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.4.6. ToString. . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.4.7. stringNameType. . . . . . . . . . . . . . . . . . . . . . . . 40
6.4.8. isAnonymous . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.4.9. isMN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.5. public enum GSSCredentialUsage. . . . . . . . . . . . . . . . . 41
6.5.1. INITIATE_AND_ACCEPT . . . . . . . . . . . . . . . . . . . . . 41
6.5.2. INITIATE_ONLY . . . . . . . . . . . . . . . . . . . . . . . . 41
6.5.3. ACCEPT_ONLY . . . . . . . . . . . . . . . . . . . . . . . . . 41
6.6. public interface GSSCredential. . . . . . . . . . . . . . . . . 41
6.6.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . . 42
6.6.2. dispose . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.6.3. getName . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.6.4. getName . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.6.5. getRemainingLifetime. . . . . . . . . . . . . . . . . . . . . 43
6.6.6. getRemainingInitLifetime. . . . . . . . . . . . . . . . . . . 44
6.6.7. getRemainingAcceptLifetime. . . . . . . . . . . . . . . . . . 44
6.6.8. getUsage. . . . . . . . . . . . . . . . . . . . . . . . . . . 44
6.6.9. getUsage. . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.6.10. getMechs . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.6.11. add. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.6.12. Equals . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
6.7. public interface GSSContext . . . . . . . . . . . . . . . . . . 47
6.7.1. Example Context . . . . . . . . . . . . . . . . . . . . . . . 48
6.7.2. initSecContext. . . . . . . . . . . . . . . . . . . . . . . . 50
6.7.2.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . 51
6.7.3. initSecContext. . . . . . . . . . . . . . . . . . . . . . . . 52
6.7.3.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . 53
6.7.4. acceptSecContext. . . . . . . . . . . . . . . . . . . . . . . 54
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6.7.4.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . 55
6.7.5. acceptSecContext. . . . . . . . . . . . . . . . . . . . . . . 56
6.7.5.1. Example Code. . . . . . . . . . . . . . . . . . . . . . . . 57
6.7.6. isEstablished . . . . . . . . . . . . . . . . . . . . . . . . 57
6.7.7. dispose . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
6.7.8. getWrapSizeLimit. . . . . . . . . . . . . . . . . . . . . . . 58
6.7.9. wrap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.7.10. wrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.7.11. unWrap . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
6.7.12. unWrap . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6.7.13. getMIC . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.7.14. getMIC . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.7.15. verifyMIC. . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.7.16. verifyMIC. . . . . . . . . . . . . . . . . . . . . . . . . . 66
6.7.17. export . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.7.18. mutualAuthenitcation . . . . . . . . . . . . . . . . . . . . 67
6.7.19. replayDetection. . . . . . . . . . . . . . . . . . . . . . . 68
6.7.20. sequenceDetection. . . . . . . . . . . . . . . . . . . . . . 68
6.7.21. credentialDelegation . . . . . . . . . . . . . . . . . . . . 68
6.7.22. anonymity. . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.7.23. confidentiality. . . . . . . . . . . . . . . . . . . . . . . 69
6.7.24. integrity. . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.7.25. lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.7.26. channelBinding . . . . . . . . . . . . . . . . . . . . . . . 70
6.7.27. isTransferable . . . . . . . . . . . . . . . . . . . . . . . 70
6.7.28. isProtReady. . . . . . . . . . . . . . . . . . . . . . . . . 70
6.7.29. srcName. . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.7.30. targName . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.7.31. mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.7.32. delegatedCredential. . . . . . . . . . . . . . . . . . . . . 71
6.7.33. isInitiator. . . . . . . . . . . . . . . . . . . . . . . . . 72
6.8. public class MessageProp. . . . . . . . . . . . . . . . . . . . 72
6.8.1. Constructors. . . . . . . . . . . . . . . . . . . . . . . . . 73
6.8.2. QOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.8.3. privacy . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.8.4. minorStatus . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.8.5. minorString . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.8.6. isDuplicateToken. . . . . . . . . . . . . . . . . . . . . . . 74
6.8.7. isOldToken. . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.8.8. isUnseqToken. . . . . . . . . . . . . . . . . . . . . . . . . 74
6.8.9. isGapToken. . . . . . . . . . . . . . . . . . . . . . . . . . 75
6.9. public class ChannelBinding . . . . . . . . . . . . . . . . . . 75
6.9.1. Constructors. . . . . . . . . . . . . . . . . . . . . . . . . 76
6.9.2. initiatorAddress. . . . . . . . . . . . . . . . . . . . . . . 76
6.9.3. acceptorAddress . . . . . . . . . . . . . . . . . . . . . . . 77
6.9.4. applicationData . . . . . . . . . . . . . . . . . . . . . . . 77
6.9.5. Equals. . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.10. public class Oid . . . . . . . . . . . . . . . . . . . . . . . 77
6.10.1. Constructor. . . . . . . . . . . . . . . . . . . . . . . . . 78
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6.10.2. ToString . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.10.3. Equals . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.10.4. DER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.10.5. containedIn. . . . . . . . . . . . . . . . . . . . . . . . . 79
6.11. public class GSSException. . . . . . . . . . . . . . . . . . . 79
6.11.1. Constants. . . . . . . . . . . . . . . . . . . . . . . . . . 80
6.11.2. Constructors . . . . . . . . . . . . . . . . . . . . . . . . 82
6.11.3. major. . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
6.11.4. minor. . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
6.11.5. majorString. . . . . . . . . . . . . . . . . . . . . . . . . 83
6.11.6. minorString. . . . . . . . . . . . . . . . . . . . . . . . . 83
6.11.7. ToString . . . . . . . . . . . . . . . . . . . . . . . . . . 83
6.11.8. Message. . . . . . . . . . . . . . . . . . . . . . . . . . . 83
7. Sample Applications . . . . . . . . . . . . . . . . . . . . . . . 84
7.1. Simple GSS Context Initiator. . . . . . . . . . . . . . . . . . 84
7.2. Simple GSS Context Acceptor . . . . . . . . . . . . . . . . . . 89
8. Security Considerations . . . . . . . . . . . . . . . . . . . . . 93
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 93
10. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . 93
11. Normative References . . . . . . . . . . . . . . . . . . . . . . 94
12. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 94
13. Intellectual Property Statement. . . . . . . . . . . . . . . . . 94
14. Disclaimer of Validity . . . . . . . . . . . . . . . . . . . . . 95
15. Copyright Statement. . . . . . . . . . . . . . . . . . . . . . . 95
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1.Introduction
This document specifies the C# language bindings for the Generic
Security Services Application Programming Interface Version 2
(GSS-API v2). 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.
One of the design goals utilized when defining the C# bindings for
GSS-API was to emulate the Java bindings specified in RFC 2853 as
much as possible while still taking advantage of C# features such
as Properties. By emulating the Java bindings, we hoped to leverage
work already done and to make life easier for developers utilizing
GSS-API under C# and Java. As a result of this design goal, the C#
bindings match the Java bindings very closely.
Because of the similarity between the Java and C# bindings and in the
spirit of leveraging work already done, this document borrows heavily
from RFC 2853.
2.GSS-API Operational Paradigm
The Generic Security Service Application Programming Interface
Version 2 defines a generic security API to calling applications. It
allows a communicating application to authenticate a user associated
with another application, to delegate rights to another application,
and to apply security services such as confidentiality and integrity
on a per-message basis.
There are four stages to using GSS-API:
1) The application acquires a set of credentials with which it may
prove its identity to other processes. The application's
credentials vouch for its global identity, which may or may not
be related to any local username under which it may be running.
2) A pair of communicating applications establish a joint security
context using their credentials. The security context
encapsulates shared state information, which is required in
order that per-message security services may be provided.
Examples of state information that might be shared between
applications as part of a security context are cryptographic
keys, and message sequence numbers. As part of the
establishment of a security context, the context initiator is
authenticated to the responder, and may require that the
responder is authenticated back to the initiator. The
initiator may optionally give the responder the right to
initiate further security contexts, acting as an agent or
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delegate of the initiator. This transfer of rights is termed
"delegation", and is achieved by creating a set of credentials,
similar to those used by the initiating application, but which
may be used by the responder.
A GSSContext object is used to establish and maintain the
shared information that makes up the security context. Certain
GSSContext methods will generate a token, which applications
treat as cryptographically protected, opaque data. The caller
of such GSSContext method is responsible for transferring the
token to the peer application, encapsulated if necessary in an
application-to-application protocol. On receipt of such a
token, the peer application should pass it to a corresponding
GSSContext method which will decode the token and extract the
information, updating the security context state information
accordingly.
3) Per-message services are invoked on a GSSContext object to
apply either:
integrity and data origin authentication, or
confidentiality, integrity and data origin authentication
to application data, which are treated by GSS-API as arbitrary
octet-strings. An application transmitting a message that it
wishes to protect will call the appropriate GSSContext method
(getMIC or wrap) to apply protection, and send the resulting
token to the receiving application. The receiver will pass the
received token (and, in the case of data protected by getMIC,
the accompanying message-data) to the corresponding decoding
method of the GSSContext interface (verifyMIC or unwrap) to
remove the protection and validate the data.
4) At the completion of a communications session (which may extend
across several transport connections), each application uses a
GSSContext method to invalidate the security context and
release any system or cryptographic resources held. Multiple
contexts may also be used (either successively or
simultaneously) within a single communications association, at
the discretion of the applications.
3. Additional Controls
This section discusses the optional services that a context initiator
may request of the GSS-API before the context establishment. Each of
these services is requested by manipulating the appropriate property
of the GSSContext interface before the first call to init is
performed.
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Only the context initiator can request context flags.
The optional services defined are:
Delegation
The (usually temporary) transfer of rights from initiator to
acceptor, enabling the acceptor to authenticate itself as an
agent of the initiator.
Mutual Authentication
In addition to the initiator authenticating its identity to the
context acceptor, the context acceptor should also authenticate
itself to the initiator.
Replay Detection
In addition to providing message integrity services, GSSContext
per-message operations of getMIC and wrap should include
message numbering information to enable verifyMIC and unwrap to
detect if a message has been duplicated.
Out-of-Sequence Detection
In addition to providing message integrity services, GSSContext
per-message operations (getMIC and wrap) should include
message sequencing information to enable verifyMIC and unwrap
to detect if a message has been received out of sequence.
Anonymous Authentication
The establishment of the security context should not reveal the
initiator's identity to the context acceptor.
Some mechanisms may not support all optional services, and some
mechanisms may only support some services in conjunction with others.
The GSSContext interface offers query methods to allow the
verification by the calling application of which services will be
available from the context when the establishment phase is complete.
In general, if the security mechanism is capable of providing a
requested service, it should do so even if additional services must
be enabled in order to provide the requested service. If the
mechanism is incapable of providing a requested service, it should
proceed without the service leaving the application to abort the
context establishment process if it considers the requested service
to be mandatory.
Some mechanisms may specify that support for some services is
optional, and that implementers of the mechanism need not provide it.
This is most commonly true of the confidentiality service, often
because of legal restrictions on the use of data-encryption, but may
apply to any of the services. Such mechanisms are required to send
at least one token from acceptor to initiator during context
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establishment when the initiator indicates a desire to use such a
service, so that the initiating GSS-API can correctly indicate
whether the service is supported by the acceptor's GSS-API.
3.1. Delegation
The GSS-API allows delegation to be controlled by the initiating
application via manipulation of the credential delegation property
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 reading the
credential delegation property of the GSSContext object. In cases
when it is, the delegated credential object can be obtained by
reading the delegated credential property. The obtained GSSCredential
object may then be used to initiate subsequent GSS-API security
contexts as an agent or delegate of the initiator. If the original
initiator's identity is "A" and the delegate's identity is "B", then,
depending on the underlying mechanism, the identity embodied by the
delegated credential may be either "A" or "B acting for A".
For many mechanisms that support delegation, a simple boolean does
not provide enough control. Examples of additional aspects of
delegation control that a mechanism might provide to an application
are duration of delegation, network addresses from which delegation
is valid, and constraints on the tasks that may be performed by a
delegate. Such controls are presently outside the scope of the GSS-
API. GSS-API implementations supporting mechanisms offering
additional controls should provide extension routines that allow
these controls to be exercised (perhaps by modifying the initiator's
GSS-API credential object prior to its use in establishing a
context). However, the simple delegation control provided by GSS-API
should always be able to over-ride other mechanism-specific
delegation controls. If the application instructs the GSSContext
object that delegation is not desired, then the implementation must
not permit delegation to occur. This is an exception to the general
rule that a mechanism may enable services even if they are not
requested - delegation may only be provided at the explicit request
of the application.
3.2. Mutual Authentication
Usually, a context acceptor will require that a context initiator
authenticate itself so that the acceptor may make an access-control
decision prior to performing a service for the initiator. In some
cases, the initiator may also request that the acceptor authenticate
itself. GSS-API allows the initiating application to request this
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mutual authentication service by setting the mutual authentication
property of the GSSContext object to "true" before making the first
call to init. The initiating application is informed as to whether
or not the context acceptor has authenticated itself. Note that some
mechanisms may not support mutual authentication, and other
mechanisms may always perform mutual authentication, whether or not
the initiating application requests it. In particular, mutual
authentication may be required by some mechanisms in order to support
replay or out-of-sequence message detection, and for such mechanisms
a request for either of these services will automatically enable
mutual authentication.
3.3. Replay and Out-of-Sequence Detection
The GSS-API may provide detection of mis-ordered messages once a
security context has been established. Protection may be applied to
messages by either application, by calling either getMIC or wrap
methods of the GSSContext object, and verified by the peer
application by calling verifyMIC or unwrap for the peer's GSSContext
object.
The getMIC method calculates a cryptographic checksum of an
application message, and returns that checksum in a token. The
application should pass both the token and the message to the peer
application, which presents them to the verifyMIC method of the
peer's GSSContext object.
The wrap method calculates a cryptographic checksum of an application
message, and places both the checksum and the message inside a single
token. The application should pass the token to the peer
application, which presents it to the unwrap method of the peer's
GSSContext object to extract the message and verify the checksum.
Either pair of routines may be capable of detecting out-of-sequence
message delivery, or duplication of messages. Details of such mis-
ordered messages are indicated through supplementary query methods of
the MessageProp object that is filled in by each of these routines.
A mechanism need not maintain a list of all tokens that have been
processed in order to support these status codes. A typical
mechanism might retain information about only the most recent "N"
tokens processed, allowing it to distinguish duplicates and missing
tokens within the most recent "N" messages; the receipt of a token
older than the most recent "N" would result in the isOldToken
property of the instance of MessageProp to be set to "true".
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3.4. Anonymous Authentication
In certain situations, an application may wish to initiate the
authentication process to authenticate a peer, without revealing its
own identity. As an example, consider an application providing
access to a database containing medical information, and offering
unrestricted access to the service. A client of such a service might
wish to authenticate the service (in order to establish trust in any
information retrieved from it), but might not wish the service to be
able to obtain the client's identity (perhaps due to privacy concerns
about the specific inquiries, or perhaps simply to avoid being placed
on mailing-lists).
In normal use of the GSS-API, the initiator's identity is made
available to the acceptor as a result of the context establishment
process. However, context initiators may request that their identity
not be revealed to the context acceptor. Many mechanisms do not
support anonymous authentication, and for such mechanisms the request
will not be honored. An authentication token will still be
generated, but the application is always informed if a requested
service is unavailable, and has the option to abort context
establishment if anonymity is valued above the other security
services that would require a context to be established.
In addition to informing the application that a context is
established anonymously (via the isAnonymous property of the
GSSContext interface), the srcName property of the acceptor's
GSSContext object will, for such contexts, be set to a reserved
internal-form name, defined by the implementation.
The ToString method for a GSSName object representing an anonymous
entity will return a printable name. The returned value will be
syntactically distinguishable from any valid principal name supported
by the implementation. The associated name-type object identifier
will be an oid representing the value of GSSNameTypes.NT_ANONYMOUS.
This name-type oid will be defined as a public, static Oid object of
the GSSName interface. 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".
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3.5. Confidentiality
If a GSSContext supports the confidentiality service, wrap method may
be used to encrypt application messages. Messages are selectively
encrypted, under the control of the setPrivacy property of the
MessageProp object used in the wrap method.
3.6. Inter-process Context Transfer
GSS-API V2 provides functionality which allows a security context to
be transferred between processes on a single machine. These are
implemented using the export method of GSSContext and a byte array
constructor of the same interface. The most common use for such a
feature is a client-server design where the server is implemented as
a single process that accepts incoming security contexts, which then
launches child processes to deal with the data on these contexts. In
such a design, the child processes must have access to the security
context object created within the parent so that they can use per-
message protection services and delete the security context when the
communication session ends.
Since the security context data structure is expected to contain
sequencing information, it is impractical in general to share a
context between processes. Thus GSSContext interface provides an
export method that the process, which currently owns the context, can
call to declare that it has no intention to use the context
subsequently, and to create an inter-process token containing
information needed by the adopting process to successfully re-create
the context. After successful completion of export, the original
security context is made inaccessible to the calling process by GSS-
API and any further usage of this object will result in failures.
The originating process transfers the inter-process token to the
adopting process, which creates a new GSSContext object using the
byte array constructor. The properties of the context are equivalent
to that of the original context.
The inter-process token may contain sensitive data from the original
security context (including cryptographic keys). Applications using
inter-process tokens to transfer security contexts must take
appropriate steps to protect these tokens in transit.
Implementations are not required to support the inter-process
transfer of security contexts. Reading the isTransferable property
of the GSSContext interface will indicate if the context object is
transferable.
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3.7. The Use of Incomplete Contexts
Some mechanisms may allow the per-message services to be used before
the context establishment process is complete. For example, a
mechanism may include sufficient information in its initial context-
level tokens for the context acceptor to immediately decode messages
protected with wrap or getMIC. For such a mechanism, the initiating
application need not wait until subsequent context-level tokens have
been sent and received before invoking the per-message protection
services.
An application can read the isProtReady property of the GSSContext
object to determine if the per-message services are available in
advance of complete context establishment. Applications wishing to
use per-message protection services on partially-established contexts
should query this method before attempting to invoke wrap or getMIC.
4. C# GSS-API Overview
The C# GSS-API leverages many of the native C# types as well as
features of the operating environment such as automatic garbage
collection, exception handling, and encapsulation. This allows for an
API that is simpler and with fewer functions than the API described
in RFC 1509 [RFC1509].
The assemblies implementing GSS-API are not part of the .NET and Mono
frameworks. Because of this, it is necessary for the assemblies to
be installed before they can be used by applications.
C# GSS-API, unlike its Java counterpart does not allow applications
to choose between different security providers. The provider utilized
by the application is determine at application build time based on
the C# GSS-API assemblies linked in. The mechanisms supported by the
C# GSS-API assemblies are not controlled by the application. C#
GSS-API assemblies are vendor specific.
The GSS-API types are present in the org.ietf.gss namespace.
Applications need to include the following line at the top of their
listings to make use of the GSS-API types:
using org.ietf.gss;
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4.1. Object Identifiers
An Oid object will be used to represent Universal Object Identifiers
(Oids). Oids are ISO-defined, hierarchically globally-interpretable
identifiers used within the GSS-API framework to identify security
mechanisms and name formats. The Oid object can be created from a
string representation of its dot notation (e.g. "1.3.6.1.5.6.2") as
well as from its ASN.1 DER encoding. Methods are also provided to
test equality and provide the DER representation for the object.
An important feature of the Oid class is that its instances are
immutable - i.e. there are no methods defined that allow one to
change the contents of an Oid. This property allows one to treat
these objects as "statics" without the need to perform copies.
Certain routines allow the usage of a default oid. A "null" value
can be used in those cases.
4.2. Object Identifier Sets
Object identifiers sets are represented as arrays of Oid
objects. C# arrays contain a length field which allows for
easy manipulation and reference.
In order to support the full functionality of RFC 2743, the Oid class
includes a method which checks for existence of an Oid object within
a specified array. This is equivalent in functionality to
gss_test_oid_set_member. The use of C# arrays and C#'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. C# GSS-API implementations will not
contain them. C#'s automatic garbage collection and the immutable
property of the Oid object eliminates the complicated memory
management issues of the C counterpart.
When ever a default value for an Object Identifier Set is required, a
"null" value can be used. Please consult the detailed method
description for details.
4.3. 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:
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GSS-API credentials can contain mechanism-specific principal
authentication data for multiple mechanisms. A GSS-API credential is
composed of a set of credential-elements, each of which is applicable
to a single mechanism. A credential may contain at most one
credential-element for each supported mechanism. A credential-
element identifies the data needed by a single mechanism to
authenticate a single principal, and conceptually contains two
credential-references that describe the actual mechanism-specific
authentication data, one to be used by GSS-API for initiating
contexts, and one to be used for accepting contexts. For mechanisms
that do not distinguish between acceptor and initiator credentials,
both references would point to the same underlying mechanism-specific
authentication data.
Credentials describe a set of mechanism-specific principals, and give
their holder the ability to act as any of those principals. All
principal identities asserted by a single GSS-API credential should
belong to the same entity, although enforcement of this property is
an implementation-specific matter. A single GSSCredential object
represents all the credential elements that have been acquired.
The creation's of an GSSContext object allows the value of "null" to
be specified as the GSSCredential input parameter. This will
indicate a desire by the application to act as a default principal.
While individual GSS-API implementations are free to determine such
default behavior as appropriate to the mechanism, the following
default behavior by these routines is recommended for portability:
For the initiator side of the context:
1) If there is only a single principal capable of initiating
security contexts for the chosen mechanism that the application
is authorized to act on behalf of, then that principal shall be
used, otherwise
2) If the platform maintains a concept of a default network-
identity for the chosen mechanism, and if the application is
authorized to act on behalf of that identity for the purpose of
initiating security contexts, then the principal corresponding
to that identity shall be used, otherwise
3) If the platform maintains a concept of a default local
identity, and provides a means to map local identities into
network-identities for the chosen mechanism, and if the
application is authorized to act on behalf of the network-
identity image of the default local identity for the purpose of
initiating security contexts using the chosen mechanism, then
the principal corresponding to that identity shall be used,
otherwise
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4) A user-configurable default identity should be used.
and for the acceptor side of the context
1) If there is only a single authorized principal identity capable
of accepting security contexts for the chosen mechanism, then
that principal shall be used, otherwise
2) If the mechanism can determine the identity of the target
principal by examining the context-establishment token
processed during the accept method, and if the accepting
application is authorized to act as that principal for the
purpose of accepting security contexts using the chosen
mechanism, then that principal identity shall be used,
otherwise
3) If the mechanism supports context acceptance by any principal,
and if mutual authentication was not requested, any principal
that the application is authorized to accept security contexts
under using the chosen mechanism may be used, otherwise
4) A user-configurable default identity shall be used.
The purpose of the above rules is to allow security contexts to be
established by both initiator and acceptor using the default behavior
whenever possible. Applications requesting default behavior are
likely to be more portable across mechanisms and implementations than
ones that instantiate an GSSCredential object representing a specific
identity.
4.4. Contexts
The GSSContext interface is used to represent one end of a GSS-API
security context, storing state information appropriate to that end
of the peer communication, including cryptographic state information.
The instantiation of the context object is done differently by the
initiator and the acceptor. After the context has been instantiated,
the initiator may choose to set various context options which will
determine the characteristics of the desired security context. When
all the application desired characteristics have been set, the
initiator will call the initSecContext method which will produce a
token for consumption by the peer's acceptSecContext method. It is
the responsibility of the application to deliver the authentication
token(s) between the peer applications for processing. Upon
completion of the context establishment phase, context attributes can
be retrieved, by both the initiator and acceptor, reading the
properties of the GSSContext object. These will reflect the actual
attributes of the established context. At this point the context can
be used by the application to apply cryptographic services to its
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data.
4.5. 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.
C# GSS-API uses byte arrays to represent authentication tokens.
Overloaded methods exist which allow the caller to supply streams
which will be used for the reading and writing of the token data.
4.6. Interprocess Tokens
Certain GSS-API routines are intended to transfer data between
processes in multi-process programs. These routines use a caller-
opaque octet-string, generated by the GSS-API in one process for use
by the GSS-API in another process. The calling application is
responsible for transferring such tokens between processes. Note
that, while GSS-API implementors are encouraged to avoid placing
sensitive information within interprocess tokens, or to
cryptographically protect them, many implementations will be unable
to avoid placing key material or other sensitive data within them.
It is the application's responsibility to ensure that interprocess
tokens are protected in transit, and transferred only to processes
that are trustworthy. An interprocess token is represented using a
byte array emitted from the export method of the GSSContext
interface. The receiver of the interprocess token would initialize
a GSSContext object with this token to create a new context. Once a
context has been exported, the GSSContext object is invalidated.
4.7. Error Reporting
RFC 2743 defined the usage of major and minor status values for
signaling of GSS-API errors. The major code, also called GSS status
code, is used to signal errors at the GSS-API level independent of
the underlying mechanism(s). The minor status value or Mechanism
status code, is a mechanism defined error value indicating a
mechanism specific error code.
C# GSS-API uses exceptions implemented by the GSSException class to
signal both minor and major error values. Both mechanism specific
errors and GSS-API level errors are signaled through instances of
this class. The usage of exceptions replaces the need for major and
minor codes to be used within the API calls. GSSException class also
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contains methods to obtain textual representations for both the major
and minor values, which is equivalent to the functionality of
gss_display_status.
4.7.1. 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 C# exceptions
mechanism, thus eliminating the need for calling errors.
A GSS status code indicates a single fatal generic API error from the
routine that has thrown the GSSException. Using exceptions announces
that a fatal error has occurred during the execution of the method.
The GSS-API operational model also allows for the signaling of
supplementary status information from the per-message calls. These
need to be handled as return values since using exceptions is not
appropriate for informatory or warning-like information. The methods
that are capable of producing supplementary information are the two
per-message methods GSSContext.verifyMIC() and GSSContext.unwrap().
These methods fill the supplementary status codes in the MessageProp
object that was passed in.
GSSException object, along with providing the functionality for
setting of the various error codes and translating them into textual
representation, also contains the definitions of all the numeric
error values. The following table lists the definitions of error
codes:
Table: GSS Status Codes
Name Value Meaning
BAD_MECH 1 An unsupported mechanism
was requested.
BAD_NAME 2 An invalid name was supplied.
BAD_NAMETYPE 3 A supplied name was of an
unsupported type.
BAD_BINDINGS 4 Incorrect channel bindings were
supplied.
BAD_STATUS 5 An invalid status code was
supplied.
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BAD_MIC 6 A token had an invalid MIC.
NO_CRED 7 No credentials were supplied, or
the credentials were unavailable
or inaccessible.
NO_CONTEXT 8 Invalid context has been
supplied.
DEFECTIVE_TOKEN 9 A supplied token was invalid.
DEFECTIVE_CREDENTIAL 10 A supplied credential was
invalid.
CREDENTIALS_EXPIRED 11 The referenced credentials
have expired.
CONTEXT_EXPIRED 12 The context has expired.
FAILURE 13 Miscellaneous failure,
unspecified at the GSS-API level.
BAD_QOP 14 The quality-of-protection
requested could not be provided.
UNAUTHORIZED 15 The operation is forbidden by
local security policy.
UNAVAILABLE 16 The operation or option is
unavailable.
DUPLICATE_ELEMENT 17 The requested credential
element already exists.
NAME_NOT_MN 18 The provided name was not a
mechanism name.
OLD_TOKEN 19 The token's validity period has
expired.
DUPLICATE_TOKEN 20 The token was a duplicate of an
earlier version.
The GSS major status code of FAILURE is used to indicate that the
underlying mechanism detected an error for which no specific GSS
status code is defined. The mechanism-specific status code can
provide more details about the error.
The different major status codes that can be contained in the
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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.
4.7.2. Mechanism-specific Status Codes
Mechanism-specific status codes are communicated in two ways, they
are part of any GSSException thrown from the mechanism specific layer
to signal a fatal error, or they are part of the MessageProp object
that the per-message calls use to signal non-fatal errors.
A default value of 0 in either the GSSException object or the
MessageProp object will be used to represent the absence of any
mechanism specific status code.
4.7.3. Supplementary Status Codes
Supplementary status codes are confined to the per-message methods of
the GSSContext interface. Because of the informative nature of these
errors it is not appropriate to use exceptions to signal them.
Instead, the per-message operations of the GSSContext interface
return these values in a MessageProp object.
The MessageProp class defines boolean properties indicating the
following supplementary states:
Table: Supplementary Status Methods
Method Name Meaning when set to "true"
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" value for any of the above properties 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.
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4.8. Names
A name is used to identify a person or entity. GSS-API authenticates
the relationship between a name and the entity claiming the name.
Since different authentication mechanisms may employ different
namespaces for identifying their principals, GSS-API's naming support
is necessarily complex in multi-mechanism environments (or even in
some single-mechanism environments where the underlying mechanism
supports multiple namespaces).
Two distinct conceptual representations are defined for names:
1) A GSS-API form represented by implementations of the GSSName
interface: A single GSSName object may contain multiple names from
different namespaces, but all names should refer to the same
entity. An example of such an internal name would be the name
returned from a call to the getName method of the GSSCredential
interface, when applied to a credential containing credential
elements for multiple authentication mechanisms employing
different namespaces. This GSSName object will contain a distinct
name for the entity for each authentication mechanism.
For GSS-API implementations supporting multiple namespaces,
GSSName implementations must contain sufficient information to
determine the namespace to which each primitive name belongs.
2) Mechanism-specific contiguous byte array and string forms:
Different GSSName initialization methods are provided to handle
both byte array and string formats and to accommodate various
calling applications and name types. These formats are capable of
containing only a single name (from a single namespace).
Contiguous string names are always accompanied by an object
identifier specifying the namespace to which the name belongs, and
their format is dependent on the authentication mechanism that
employs that name. The string name forms are assumed to be
printable, and may therefore be used by GSS-API applications for
communication with their users. The byte array name formats are
assumed to be in non-printable formats (e.g. the byte array
returned from the export method of the GSSName interface).
A GSSName object can be converted to a contiguous representation by
using the ToString method. This will guarantee that the name will be
converted to a printable format. Different initialization methods in
the GSSName interface are defined allowing support for multiple
syntaxes for each supported namespace, and allowing users the freedom
to choose a preferred name representation. The ToString method
should use an implementation-chosen printable syntax for each
supported name-type. To obtain the printable name type, the
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getStringNameType method can be used.
There is no guarantee that calling the ToString method on the GSSName
interface will produce the same string form as the original imported
string name. Furthermore, it is possible that the name was not even
constructed from a string representation. The same applies to name-
space identifiers which may not necessarily survive unchanged after a
journey through the internal name-form. An example of this might be
a mechanism that authenticates X.500 names, but provides an
algorithmic mapping of Internet DNS names into X.500. That
mechanism's implementation of GSSName might, when presented with a
DNS name, generate an internal name that contained both the original
DNS name and the equivalent X.500 name. Alternatively, it might only
store the X.500 name. In the latter case, the ToString method of
GSSName would most likely generate a printable X.500 name, rather
than the original DNS name.
The context acceptor can obtain a GSSName object representing the
entity performing the context initiation (by reading the srcName
property). Since this name has been authenticated by a
single mechanism, it contains only a single name (even if the
internal name presented by the context initiator to the GSSContext
object had multiple components). Such names are termed internal
mechanism names, or "MN"s and the property values srcName and
targName of the GSSContext interface are always of this type.
Since some applications may require MNs without wanting to incur the
overhead of an authentication operation, creation methods are
provided that take not only the name buffer and name type, but also
the mechanism oid for which this name should be created. When
dealing with an existing GSSName object, the canonicalize method may
be invoked to convert a general internal name into an MN.
GSSName objects can be compared using their Equal method, which
returns "true" if the two names being compared refer to the same
entity. This is the preferred way to perform name comparisons
instead of using the printable names that a given GSS-API
implementation may support. Since GSS-API assumes that all primitive
names contained within a given internal name refer to the same
entity, equal can return "true" if the two names have at least one
primitive name in common. If the implementation embodies knowledge
of equivalence relationships between names taken from different
namespaces, this knowledge may also allow successful comparisons of
internal names containing no overlapping primitive elements.
When used in large access control lists, the overhead of creating an
GSSName object on each name and invoking the equal method on each
name from the ACL may be prohibitive. As an alternative way of
supporting this case, GSS-API defines a special form of the
contiguous byte array name which may be compared directly (byte by
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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 GSSNameTypes.NT_EXPORT_NAME as
the name type object identifier. The resulting GSSName name will
also be a MN. The GSSName interface defines public static Oid
objects representing the standard name types. Structurally, an
exported name object consists of a header containing an OID
identifying the mechanism that authenticated the name, and a trailer
containing the name itself, where the syntax of the trailer is
defined by the individual mechanism specification. Detailed
description of the format is specified in the language-independent
GSS-API specification [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 same principal; the second whether a particular mechanism would
authenticate them as the same principal. These two operations will
in general give the same results only for MNs.
It is important to note that the above are guidelines as how GSSName
implementations should behave, and are not intended to be specific
requirements of how names objects must be implemented. The mechanism
designers are free to decide on the details of their implementations
of the GSSName interface as long as the behavior satisfies the above
guidelines.
4.9. Channel Bindings
GSS-API supports the use of user-specified tags to identify a given
context to the peer application. These tags are intended to be used
to identify the particular communications channel that carries the
context. Channel bindings are communicated to the GSS-API using the
ChannelBinding object. The application may use byte arrays to
specify the application data to be used in the channel binding as
well as using instances of the EndPoint class. The EndPoint for the
initiator and/or acceptor can be used within an instance of a
ChannelBinding. ChannelBinding can be set for the GSSContext object
by setting the channelBinding property before the first call to init
or accept has been performed. The channelBinding property of a
GSSContext object defaults to "null". Currently the ChannelBinding
class only supports addresses of type IP. Applications that use
other types of addresses can include them as part of the application
specific data.
Conceptually, the GSS-API concatenates the initiator and acceptor
address information, and the application supplied byte array to form
an octet string. The mechanism calculates a MIC over this octet
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string and binds the MIC to the context establishment token emitted
by init method of the GSSContext interface. The same bindings are
set by the context acceptor for its GSSContext object and during
processing of the accept method a MIC is calculated in the same way.
The calculated MIC is compared with that found in the token, and if
the MICs differ, accept will throw a GSSException with the major
code set to BAD_BINDINGS, and the context will not be established.
Some mechanisms may include the actual channel binding data in the
token (rather than just a MIC); applications should therefore not use
confidential data as channel-binding components.
Individual mechanisms may impose additional constraints on addresses
that may appear in channel bindings. For example, a mechanism may
verify that the initiator address field of the channel binding
contains the correct network address of the host system. Portable
applications should therefore ensure that they either provide correct
information for the address fields, or omit setting of the addressing
information.
5. Introduction to GSS-API Classes and Interfaces
This section presents a brief description of the classes and
interfaces that constitute the GSS-API.
This section also shows the corresponding RFC 2743 functionality
implemented by each of the classes. Detailed description of these
classes and their methods is presented in section 6.
5.1. GSSManager Class
This abstract class serves as a factory to instantiate
implementations of the GSS-API interfaces and also provides methods
to make queries about underlying security mechanisms.
A default implementation can be obtained using the static method
getInstance(). Applications that desire to provide their own
implementation of the GSSManager class can simply extend the abstract
class themselves.
This class contains equivalents of the following RFC 2743 routines:
gss_import_name Create an internal name from the
supplied information.
gss_acquire_cred Acquire credential for use.
gss_import_sec_context Create a previously exported context.
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gss_indicate_mechs List the mechanisms supported by this
GSS-API implementation.
gss_inquire_mechs_for_name List the mechanisms supporting the
specified name type.
gss_inquire_names_for_mech List the name types supported by the
specified mechanism.
5.2. GSSName Interface
GSS-API names are represented in the C# bindings through the
GSSName interface. Different name formats and their definitions are
identified with universal Object Identifiers (oids). The format of
the names can be derived based on the unique oid of each name type.
The following GSS-API routines are provided by the GSSName interface:
RFC 2743 Routine Function
gss_display_name Covert internal name representation to text
format.
gss_compare_name Compare two internal names.
gss_canonicalize_name Convert an internal name to a mechanism name.
gss_export_name Convert a mechanism name to export format.
The gss_release_name call is not provided as C# does its own
garbage collection. The gss_duplicate_name call is also redundant;
the GSSName interface has no methods that can change the state of the
object so it is safe for sharing.
5.3. GSSCredential Interface
The GSSCredential interface is responsible for the encapsulation of
GSS-API credentials. Credentials identify a single entity and
provide the necessary cryptographic information to enable the
creation of a context on behalf of that entity. A single credential
may contain multiple mechanism specific credentials, each referred to
as a credential element. The GSSCredential interface provides the
functionality of the following GSS-API routines:
RFC 2743 Routine Function
gss_add_cred Constructs credentials incrementally.
gss_inquire_cred Obtain information about credential.
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gss_inquire_cred_by_mech Obtain per-mechanism information about
a credential.
gss_release_cred Disposes of credentials after use.
5.4. GSSContext Interface
This interface encapsulates the functionality of context-level calls
required for security context establishment and management between
peers as well as the per-message services offered to applications. A
context is established between a pair of peers and allows the usage
of security services on a per-message basis on application data. It
is created over a single security mechanism. The GSSContext
interface provides the functionality of the following GSS-API
routines:
RFC 2743 Routine Function
gss_init_sec_context Initiate the creation of a security context
with a peer.
gss_accept_sec_context Accept a security context initiated by a
peer.
gss_delete_sec_context Destroy a security context.
gss_context_time Obtain remaining context time.
gss_inquire_context Obtain context characteristics.
gss_wrap_size_limit Determine token-size limit for gss_wrap.
gss_export_sec_context Transfer security context to another
process.
gss_get_mic Calculate a cryptographic Message Integrity
Code (MIC) for a message.
gss_verify_mic Verify integrity on a received message.
gss_wrap Attach a MIC to a message and optionally
encrypt the message content.
gss_unwrap Obtain a previously wrapped 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 C# bindings specification. The
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corresponding functionality of gss_delete_sec_context has also been
modified to not return any peer tokens. This has been proposed in
accordance to the recommendations stated in RFC 2743. GSSContext
does offer the functionality of destroying the locally-stored context
information.
5.5. MessageProp Class
This helper class is used in the per-message operations on the
context. An instance of this class is created by the application and
then passed into the per-message calls. In some cases, the
application conveys information to the GSS-API implementation through
this object and in other cases the GSS-API returns information to the
application by setting it in this object. See the description of the
per-message operations wrap, unwrap, getMIC, and verifyMIC in the
GSSContext interface for details.
5.6. GSSException Class
Exceptions are used in the C# 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 can throw this exception.
RFC 2743 Routine Function
gss_display_status Retrieve textual representation of
error codes.
5.7. Oid Class
This utility class is used to represent Universal Object Identifiers
and their associated operations. GSS-API uses object identifiers to
distinguish between security mechanisms and name types. This class,
aside from being used whenever an object identifier is needed,
implements the following GSS-API functionality:
RFC 2743 Routine Function
gss_test_oid_set_member Determine if the specified oid is part of a
set of oids.
5.8. ChannelBinding Class
An instance of this class is used to specify channel binding
information to the GSSContext object before the start of a security
context establishment. The application may use a byte array to
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specify application data to be used in the channel binding as well as
use instances of the EndPoint. Currently the ChannelBinding class
only supports addresses of type IP. Applications that use other
types of addresses can include them as part of the application
specific data.
5.9. GSSConstants Class
This utility class defines various constants utilized throughout the
API.
5.10. GSSNameTypes Class
This class defines OIDs which specify different types of GSSNames.
5.11. GSSCredentialUsage Enumeration
This enumeration defines the usage categories for GSSCredentials.
GSSCredentials can be used for context initiation and context
acceptance or only one of those functions.
6. Detailed GSS-API Description
This section lists a detailed description of all the public methods
that each of the GSS-API classes and interfaces must provide.
6.1. public abstract class GSSManager
The GSSManager class is an abstract class that serves as a factory
for three GSS interfaces: GSSName, GSSCredential, and GSSContext. It
also provides methods for applications to determine what mechanisms
are available from the GSS implementation and what nametypes these
mechanisms support. An instance of the default GSSManager subclass
may be obtained through the static method getInstance(), but
applications are free to instantiate other subclasses of GSSManager.
All but one method in this class are declared abstract. This means
that subclasses have to provide the complete implementation for those
methods. The only exception to this is the static method
getInstance() which will have platform specific code to return an
instance of the default subclass.
Platform providers of GSS are required not to add any constructors to
this class, private, public, or protected. This will ensure that all
subclasses invoke only the default constructor provided to the base
class by the compiler.
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6.1.1. Example Code
GSSManager mgr = GSSManager.getInstance();
// What mechs are available to us?
Oid[] supportedMechs = mgr.getMechs();
// What name types does this spkm implementation support?
Oid[] nameTypes = mgr.getNamesForMech(spkm1);
6.1.2. getInstance
public static GSSManager getInstance();
Returns the default GSSManager implementation.
Throws GSSException if an error is detected.
6.1.3. getMechs
public abstract Oid[] getMechs();
Returns an array of Oid objects indicating mechanisms available to
GSS-API callers. A "null" value is returned when no mechanism are
available (an example of this would be when mechanism are dynamically
configured, and currently no mechanisms are installed).
Throws GSSException if an error is detected.
6.1.4. getNamesForMech
public abstract Oid[] getNamesForMech(Oid mech);
Returns name type Oid's supported by the specified mechanism.
Throws GSSException if an error is detected.
Parameters:
mech The Oid object for the mechanism to query.
6.1.5. getMechsForName
public abstract Oid[] getMechsForName(Oid nameType);
Returns an array of Oid objects corresponding to the mechanisms that
support the specific name type. "null" is returned when no
mechanisms are found to support the specified name type.
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Throws GSSException if an error is detected.
Parameters:
nameType The Oid object for the name type.
6.1.6. createName
public abstract GSSName createName(string nameStr,
Oid nameType);
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
GSSNameTypes.NT_EXPORT_NAME or when the GSS-API implementation is not
multi-mechanism.
Throws GSSException if an error is detected.
Parameters:
nameStr The string representing a printable form of the name
to create.
nameType The Oid specifying the namespace of the printable name
supplied. Note that nameType serves to describe and
qualify the interpretation of the input nameStr, it
does not necessarily imply a type for the output
GSSName implementation. "null" value specifies that a
mechanism specific default printable syntax should be
assumed by each mechanism that examines nameStr.
6.1.7. createName
public abstract GSSName createName(byte[] name,
Oid nameType);
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
GSSNameTypes.NT_EXPORT_NAME or when the GSS-API implementation is not
multi-mechanism.
Throws GSSException if an error is detected.
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Parameters:
name The byte array containing the name to create.
nameType The Oid specifying the namespace of the name supplied
in the byte array. Note that nameType serves to
describe and qualify the interpretation of the input
name byte array, it does not necessarily imply a type
for the output GSSName implementation. "null" value can
be used to specify that a mechanism specific default
syntax should be assumed by each mechanism that examines
the byte array.
6.1.8. createName
public abstract GSSName createName(string nameStr,
Oid nameType,
Oid mech);
Factory method to convert a contiguous string name from the specified
namespace to an GSSName object that is a mechanism name (MN). In
other words, this method is a utility that does the equivalent of two
steps: the createName described in 6.1.6 and then also the
GSSName.canonicalize() described in 6.2.5.
Throws GSSException if an error is detected.
Parameters:
nameStr The string representing a printable form of the name
to create.
nameType The Oid specifying the namespace of the printable name
supplied. Note that nameType serves to describe and
qualify the interpretation of the input nameStr, it
does not necessarily imply a type for the output
GSSName implementation. "null" value can be used to
specify that a mechanism specific default printable
syntax should be assumed when the mechanism examines
nameStr.
mech Oid specifying the mechanism for which this name
should be created.
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6.1.9. createName
public abstract GSSName createName(byte[] name,
Oid nameType,
Oid mech);
Throws GSSException if an error is detected.
Factory method to convert a contiguous byte array containing a name
from the specified namespace to a GSSName object that is an MN. In
other words, this method is a utility that does the equivalent of two
steps: the createName described in 6.1.7 and then also the
GSSName.canonicalize() described in 6.2.5.
Parameters:
name The byte array representing the name to create.
nameType The Oid specifying the namespace of the name supplied
in the byte array. Note that nameType serves to
describe and qualify the interpretation of the input
name byte array, it does not necessarily imply a type
for the output GSSName implementation. "null" value
can be used to specify that a mechanism specific
default syntax should be assumed by each mechanism
that examines the byte array.
mech Oid specifying the mechanism for which this name
should be created.
6.1.10. createCredential
public abstract GSSCredential createCredential(int usage);
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.
Throws GSSException if an error is detected.
Parameters:
usage The intended usage for this credential object. The
value of this parameter must be one of:
GSSCredential.ACCEPT_AND_INITIATE
GSSCredential.ACCEPT_ONLY
GSSCredential.INITIATE_ONLY
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6.1.11. createCredential
public abstract GSSCredential createCredential(GSSName aName,
int lifetime,
Oid mech,
int usage);
Throws GSSException if an error is detected.
Factory method for acquiring a single mechanism credential.
Parameters:
aName Name of the principal for whom this credential is to
be acquired. Use "null" to specify the default
principal.
lifetime The number of seconds that credentials should remain
valid. Use GSSCredential.INDEFINITE_LIFETIME to
request that the credentials have the maximum
permitted lifetime. Use GSSCredential.DEFAULT_LIFETIME
to request default credential lifetime.
mech The oid of the desired mechanism. Use "(Oid) null" to
request the default mechanism(s).
usage The intended usage for this credential object. The
value of this parameter must be one of:
GSSCredential.ACCEPT_AND_INITIATE
GSSCredential.ACCEPT_ONLY
GSSCredential.INITIATE_ONLY
6.1.12. createCredential
public abstract GSSCredential createCredential(GSSName aName,
int lifetime,
Oid mechs[],
int usage);
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.
Throws GSSException if an error is detected.
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Parameters:
aName Name of the principal for whom this credential is to
be acquired. Use "null" to specify the default
principal.
lifetime The number of seconds that credentials should remain
valid. Use GSSCredential.INDEFINITE_LIFETIME to
request that the credentials have the maximum
permitted lifetime. Use GSSCredential.DEFAULT_LIFETIME
to request default credential lifetime.
mechs The array of mechanisms over which the credential is
to be acquired. Use "(Oid[]) null" for requesting a
system specific default set of mechanisms.
usage The intended usage for this credential object. The
value of this parameter must be one of:
GSSCredential.ACCEPT_AND_INITIATE
GSSCredential.ACCEPT_ONLY
GSSCredential.INITIATE_ONLY
6.1.13. createContext
public abstract GSSContext createContext(GSSName peer,
Oid mech,
GSSCredential myCred,
int lifetime);
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().
Throws GSSException if an error is detected.
Parameters:
peer Name of the target peer.
mech Oid of the desired mechanism. Use "(Oid) null" to
request default mechanism.
myCred Credentials of the initiator. Use "null" to act as a
default initiator principal.
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lifetime The request lifetime, in seconds, for the context.
Use GSSContext.INDEFINITE_LIFETIME and
GSSContext.DEFAULT_LIFETIME to request indefinite or
default context lifetime.
6.1.14. createContext
public abstract GSSContext createContext(GSSCredential myCred);
Factory method for creating a context on the acceptor' side. The
context's properties will be determined from the input token supplied
to the accept method.
Throws GSSException if an error is detected.
Parameters:
myCred Credentials for the acceptor. Use "null" to act as a
default acceptor principal.
6.1.15. createContext
public abstract GSSContext createContext(byte[] interProcessToken);
Factory method for creating a previously exported context. The
context properties will be determined from the input token and can't
be modified through the set methods.
Throws GSSException if an error is detected.
Parameters:
interProcessToken The token previously emitted from the export
method.
6.2. public class GSSConstants
This class defines constants that are common among various interfaces
and/or classes of the API.
6.2.1. DEFAULT_LIFETIME
const int DEFAULT_LIFETIME = 0;
A constant representing the default lifetime for a context or
credential.
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6.2.2. INDEFINITE_LIFETIME
const int INDEFINITE_LIFETIME = Int32.MaxValue;
A constant representing indefinite lifetime for a context or
credential.
6.3. public class GSSNameTypes
This class defines the various types of GSSNames.
6.3.1. NT_HOSTBASED_SERVICE
public static Oid NT_HOSTBASED_SERVICE;
Property which indicates Oid of name type of a host-based service
name form. It is used to represent services associated with host
computers. This name form is constructed using two elements,
"service" and "hostname", as follows:
service@hostname
Values for the "service" element are registered with the IANA. It
represents the following value: { 1(iso), 3(org), 6(dod),
1(internet), 5(security), 6(nametypes), 2(gss-host-based-services) }
6.3.2. NT_USER_NAME
public static Oid NT_USER_NAME;
Property which indicates Oid of name type of a named user on a local
system. It represents the following value: { 1(iso), 2(member-body),
840(United States), 113554(mit), 1(infosys), 2(gssapi), 1(generic),
1(user_name) }
6.3.3. NT_MACHINE_UID_NAME
public static Oid NT_MACHINE_UID_NAME;
Property which indicates Oid of name type of a numeric user
identifier corresponding to a user on a local system. (e.g. Uid).
It represents the following value: { 1(iso), 2(member-body),
840(United States), 113554(mit), 1(infosys), 2(gssapi), 1(generic),
2(machine_uid_name) }
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6.3.4. NT_STRING_UID_NAME
public static Oid NT_STRING_UID_NAME;
Property which indicates Oid of name type of a string of digits
representing the numeric user identifier of a user on a local system.
It represents the following value: { 1(iso), 2(member-body),
840(United States), 113554(mit), 1(infosys), 2(gssapi), 1(generic),
3(string_uid_name) }
6.3.5. NT_ANONYMOUS
public static Oid NT_ANONYMOUS;
Property which indicates Oid of name type of an anonymous entity.
It represents the following value: { 1(iso), 3(org), 6(dod),
1(internet), 5(security), 6(nametypes), 3(gss-anonymous-name) }
6.3.6. NT_EXPORT_NAME
public static Oid NT_EXPORT_NAME;
Property which indicates Oid of name type of an exported name
produced by the export method. It represents the following value:
{ 1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
4(gss-api-exported-name) }
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6.4. public interface GSSName
This interface encapsulates a single GSS-API principal entity.
Different name formats and their definitions are identified with
universal Object Identifiers (Oids). The format of the names can be
derived based on the unique oid of its namespace type.
6.4.1. Example Code
Included below are code examples utilizing the GSSName interface.
The code below creates a GSSName, converts it to a mechanism name
(MN), performs a comparison, obtains a printable representation of
the name, exports it and then re-imports to obtain a new GSSName.
GSSManager mgr = GSSManager.getInstance();
// create a host based service name
GSSName name = mgr.createName("service@host",
GSSNameTypes.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",
GSSNameTypes.NT_HOSTBASED_SERVICE,
krb5);
// perform name comparison
if (name.Equals(mechName))
Console.WriteLine("Names are equals.");
// obtain textual representation of name and its printable
// name type
Console.WriteLine(mechName.ToString() +
mechName.getStringNameType().ToString());
// export and re-import the name
byte[] exportName = mechName.export();
// create a new name object from the exported buffer
GSSName newName = mgr.createName(exportName,
GSSNameTypes.NT_EXPORT_NAME);
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6.4.2. Equals
bool Equals(GSSName another);
Compares two GSSName objects to determine whether they refer to the
same entity. If either of the names represents an anonymous
entity, the method will return "false".
Throws GSSException if an error is detected.
Parameters:
another GSSName object to compare with.
6.4.3. Equals
bool Equals(Object another);
A variation of the equals method described in 6.2.3 that is provided
to override the Object.Equals() method that the implementing class
will inherit. The behavior is exactly the same as that in 6.2.3
except that no GSSException is thrown; instead, false will be
returned in the situation where an error occurs. (Note that the C#
language specification requires that two objects that are equal
according to the Equals(Object) method must return the same integer
result when the GetHashCode() method is called on them.)
Parameters:
another GSSName object to compare with.
6.4.4. canonicalize
GSSName canonicalize(Oid mech);
Creates a mechanism name (MN) from an arbitrary internal name. This
is equivalent to using the factory methods described in 6.1.8 or
6.1.9 that take the mechanism name as one of their parameters.
Throws GSSException if an error is detected.
Parameters:
mech The oid for the mechanism for which the canonical form
of the name is requested.
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6.4.5. export
byte[] export();
Returns a canonical contiguous byte representation of a mechanism
name (MN), suitable for direct, byte by byte comparison by
authorization functions. If the name is not an MN, implementations
may throw a GSSException with the NAME_NOT_MN status code. If an
implementation chooses not to throw an exception, it should use some
system specific default mechanism to canonicalize the name and then
export it. The format of the header of the output buffer is
specified in RFC 2743.
6.4.6. ToString
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.
Throws GSSException if an error is detected.
6.4.7. stringNameType
Oid stringNameType;
Property of the object containing the oid representing the type of
name returned through the ToString method. Using this oid, the
syntax of the printable name can be determined.
Throws GSSException if an error is detected.
6.4.8. isAnonymous
bool isAnonymous;
Property which indicates whether the name object represents an
anonymous entity or not. If "true" then it is an anonymous name.
6.4.9. isMN
bool isMN;
Property which indicates whether the name object contains only one
mechanism element and is a mechanism name as defined by RFC 2743.
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6.5. public enum GSSCredentialUsage
This enumeration defines the usage categories for credentials.
6.5.1. INITIATE_AND_ACCEPT
Credentials of this type can be used for both context initiation
and acceptance.
6.5.2. INITIATE_ONLY
Credentials of this type can be used for context initiation only.
6.5.3. ACCEPT_ONLY
Credentials of this type can be used for context acceptance only.
6.6. public interface GSSCredential: ICloneable
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.
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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 ICloneable
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.
6.6.1. Example Code
This example code demonstrates the creation of a GSSCredential
implementation for a specific entity, querying of its fields, and its
release when it is no longer needed.
GSSManager mgr = GSSManager.getInstance();
// start by creating a name object for the entity
GSSName name = mgr.createName("userName", GSSNameTypes.NT_USER_NAME);
// now acquire credentials for the entity
GSSCredential cred = mgr.createCredential(name,
GSSCredentialUsage.ACCEPT_ONLY);
// display credential information - name, remaining lifetime,
// and the mechanisms it has been acquired over
Console.WriteLine(cred.getName().ToString());
Console.WriteLine(cred.getRemainingLifetime());
Oid[] mechs = cred.getMechs();
if (mechs != null) {
for (int i = 0; i < mechs.length; i++)
Console.WriteLine(mechs[i].ToString());
}
// release system resources held by the credential
cred.dispose();
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6.6.2. dispose
void dispose();
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.
Throws GSSException if an error is detected.
6.6.3. getName
GSSName getName();
Retrieves the name of the entity that the credential asserts.
Throws GSSException if an error is detected.
6.6.4. getName
GSSName getName(Oid mechOID);
Retrieves a mechanism name of the entity that the credential asserts.
Throws GSSException if an error is detected.
Parameters:
mechOID The mechanism for which information should be
returned.
6.6.5. getRemainingLifetime
int getRemainingLifetime();
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
GSSConstants.INDEFINITE_LIFETIME indicates that the credential does
not expire. A return value of 0 indicates that the credential is
already expired.
Throws GSSException if an error is detected.
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6.6.6. getRemainingInitLifetime
int getRemainingInitLifetime(Oid mech);
Returns the remaining lifetime is seconds for the credential to
remain capable of initiating security contexts under the specified
mechanism. A return value of GSSConstants.INDEFINITE_LIFETIME
indicates that the credential does not expire for context initiation.
A return value of 0 indicates that the credential is already expired.
Throws GSSException if an error is detected.
Parameters:
mechOID The mechanism for which information should be
returned.
6.6.7. getRemainingAcceptLifetime
int getRemainingAcceptLifetime(Oid mech);
Returns the remaining lifetime is seconds for the credential to
remain capable of accepting security contexts under the specified
mechanism. A return value of GSSConstants.INDEFINITE_LIFETIME
indicates that the credential does not expire for context acceptance.
A return value of 0 indicates that the credential is already expired.
Throws GSSException if an error is detected.
Parameters:
mechOID The mechanism for which information should be
returned.
6.6.8. getUsage
GSSCredentialUsage getUsage();
Returns the usage category for the credential.
Throws GSSException if an error is detected.
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6.6.9. getUsage
GSSCredentialUsage getUsage(Oid mechOID);
Returns the usage category for the specified credential mechanism.
Throws GSSException if an error is detected.
Parameters:
mechOID The mechanism for which information should be
returned.
6.6.10. getMechs
Oid[] getMechs();
Returns an array of mechanisms supported by this credential.
Throws GSSException if an error is detected.
6.6.11. add
void add(GSSName aName,
int initLifetime,
int acceptLifetime,
Oid mech,
int usage);
Adds a mechanism specific credential-element to an existing
credential. This method allows the construction of credentials one
mechanism at a time.
This routine is envisioned to be used mainly by context acceptors
during the creation of acceptance credentials which are to be used
with a variety of clients using different security mechanisms.
This routine adds the new credential element "in-place". To add the
element in a new credential, first call Clone() to obtain a copy of
this credential, then call its add() method.
Throws GSSException if an error is detected.
Parameters:
aName Name of the principal for whom this credential is to
be acquired. Use "null" to specify the default
principal.
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initLifetime
The number of seconds that credentials should remain
valid for initiating of security contexts. Use
GSSCredential.INDEFINITE_LIFETIME to request that the
credentials have the maximum permitted lifetime. Use
GSSCredential.DEFAULT_LIFETIME to request default
credential lifetime.
acceptLifetime
The number of seconds that credentials should remain
valid for accepting of security contexts. Use
GSSCredential.INDEFINITE_LIFETIME to request that the
credentials have the maximum permitted lifetime. Use
GSSCredential.DEFAULT_LIFETIME to request default
credential lifetime.
mech The mechanisms over which the credential is to be
acquired.
usage The intended usage for this credential object. The
value of this parameter must be one of:
GSSCredential.ACCEPT_AND_INITIATE,
GSSCredential.ACCEPT_ONLY, GSSCredential.INITIATE_ONLY
6.6.12. Equals
bool Equals(Object another);
Tests if this GSSCredential refers to the same entity as the supplied
object. The two credentials must be acquired over the same
mechanisms and must refer to the same principal. Returns "true" if
the two GSSCredentials refer to the same entity; "false" otherwise.
Parameters:
another Another GSSCredential object for comparison.
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6.7. public interface GSSContext
This interface encapsulates the GSS-API security context and provides
the security services (wrap, unwrap, getMIC, verifyMIC) that are
available over the context. Security contexts are established
between peers using locally acquired credentials. Multiple contexts
may exist simultaneously between a pair of peers, using the same or
different set of credentials. GSS-API functions in a manner
independent of the underlying transport protocol and depends on its
calling application to transport its tokens between peers.
Before the context establishment phase is initiated, the context
initiator may request specific characteristics desired of the
established context. These can be set by manipulating the
GSSContext properties. After the context is established, the caller
can check the actual characteristic and services offered by the
context by examining the GSSContext properties.
The context establishment phase begins with the first call to the
init method by the context initiator. During this phase the
initSecContext and acceptSecContext methods will produce GSS-API
authentication tokens which the calling application needs to send to
its peer. If an error occurs at any point, an exception will get
thrown and the code will start executing in a catch block. If not,
the normal flow of code continues and the application can read the
isEstablished property. If this property is false it indicates that
a token is needed from its peer in order to continue the context
establishment phase. A setting 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 property indicates whether or
not the context can be used for the per-message operations. This
allows applications to use per-message operations on contexts which
aren't fully established.
After the context has been established or the isProtReady property is
"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.
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6.7.1. Example Code
The example code presented below demonstrates the usage of the
GSSContext interface for the initiating peer. Different operations
on the GSSContext object are presented, including: object
instantiation, setting of desired flags, context establishment, query
of actual context flags, per-message operations on application data,
and finally context deletion.
GSSManager mgr = GSSManager.getInstance();
// start by creating the name for a service entity
GSSName targetName = mgr.createName("service@host",
GSSNameTypes.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 */
GSSConstants.INDEFINITE_LIFETIME);
// set desired context options - all others are false by default
context.confidentiality = true;
context.mutualAuthentication = true;
context.replayDetection = true;
context.sequenceDetection = true;
// establish a context between peers - using byte arrays
byte[] inTok = new byte[0];
try {
do {
byte[] outTok = context.initSecContext(inTok,
0,
inTok.length);
// send the token if present
if (outTok != null)
sendToken(outTok);
// check if we should expect more tokens
if (context.isEstablished)
break;
// another token expected from peer
inTok = readToken();
} while (true);
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} catch (GSSException e) {
Console.Writeline("GSSAPI error: " + e.Message);
}
// display context information
Console.Writeline("Remaining lifetime in seconds = " +
context.lifetime);
Console.Writeline("Context mechanism = " + context.Mech.ToString());
Console.Writeline("Initiator = " + context.srcName.ToString());
Console.Writeline("Acceptor = " + context.targName.ToString());
if (context.confidentiality)
Console.Writeline("Confidentiality security service available");
if (context.integrity)
Console.Writeline("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);
byte[] tok = context.wrap(appMsg, 0, appMsg.length, mProp);
if (mProp.privacy)
Console.Writeline("Message protected with privacy.");
sendToken(tok);
// release the local-end of the context
context.dispose();
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6.7.2. initSecContext
byte[] initSecContext(byte[] inputBuf,
int offset,
int len);
Called by the context initiator to start the context creation
process. This is equivalent to the stream based method except that
the token buffers are handled as byte arrays instead of using stream
objects. This method may return an output token which the
application will need to send to the peer for processing by the
accept call. The application can check the isEstablished property to
determine if the context establishment phase is complete for this
peer. A value of "false" for isEstablished indicates that more
tokens are expected to be supplied to the initSecContext method.
Note that it is possible for the initSecContext() method to return a
token for the peer when isEstablished is set to "true". This
indicates that the token needs to be sent to the peer, but the local
end of the context is now fully established.
Throws GSSException if an error is detected.
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).
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6.7.2.1. Example Code
// Create a new GSSContext implementation object.
// GSSContext wrapper implements interface GSSContext.
GSSContext context = mgr.createContext(...);
byte[] inTok = new byte[0];
try {
do {
byte[] outTok = context.initSecContext(inTok,
0,
inTok.length);
// send the token if present
if (outTok != null)
sendToken(outTok);
// check if we should expect more tokens
if (context.isEstablished)
break;
// another token expected from peer
inTok = readToken();
} while (true);
} catch (GSSException e) {
Console.Writeline("GSSAPI error: " + e.Message);
}
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6.7.3. initSecContext
void initSecContext(Stream inStream,
Stream outStream);
Called by the context initiator to start the context creation
process. This is equivalent to the byte array based method. This
method may write an output token to the outStream, which the
application will need to send to the peer for processing by the
accept call. The application can check the isEstablished property to
determine if the context establishment phase is complete for this
peer. A value of "false" for isEstablished indicates that more
tokens are expected to be supplied to the initSecContext method.
Note that it is possible that the initSecContext() method to return a
token for the peer when isEstablished is set to "true". This
indicates that the token needs to be sent to the peer, but the local
end of the context is now fully established.
The GSS-API authentication tokens contain a definitive start and end.
This method will attempt to read one of these tokens per invocation,
and may block on the stream if only part of the token is available.
Throws GSSException if an error is detected.
Parameters:
inStream Stream to read the token generated by the peer. This
parameter is ignored on the first call.
outStream Stream where the output token will be written.
During the final stage of context establishment, there
may be no bytes written.
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6.7.3.1. Example Code
// Create a new GSSContext implementation object.
// GSSContext wrapper implements interface GSSContext.
GSSContext context = mgr.createContext(...);
MemoryStream os = new MemoryStream();
Stream is = null;
try {
do {
context.initSecContext(is, os);
// send token if present
if (os.Length > 0)
sendToken(os);
// check if we should expect more tokens
if (context.isEstablished)
break;
// another token expected from peer
is = recvToken();
} while (true);
} catch (GSSException e) {
Console.Writeline("GSSAPI error: " + e.Message);
}
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6.7.4. acceptSecContext
byte[] acceptSecContext(byte[] inTok,
int offset,
int len);
Called by the context acceptor upon receiving a token from the peer.
This call is equivalent to the stream based method except that the
token buffers are handled as byte arrays instead of using stream
objects.
This method may return an output token which the application will
need to send to the peer for further processing by the init call.
A "null" return value indicates that no token needs to be sent to the
peer. The application can check the isEstablished property to
determine if the context establishment phase is complete for this
peer. A value of "false" for isEstablished indicates that more
tokens are expected to be supplied to this method. Note that it is
possible that the acceptSecContext() method to return a token for the
peer when isEstablished is set to "true". 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.
Throws GSSException if an error is detected.
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).
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6.7.4.1. Example Code
// acquire server credentials
GSSCredential server = mgr.createCredential(...);
// create acceptor GSS-API context from the default provider
GSSContext context = mgr.createContext(server, null);
try {
do {
byte[] inTok = readToken();
byte[] outTok = context.acceptSecContext(inTok,
0,
inTok.length);
// possibly send token to peer
if (outTok != null)
sendToken(outTok);
// check if local context establishment is complete
if (context.isEstablished)
break;
} while (true);
} catch (GSSException e) {
Console.Writeline("GSS-API error: " + e.Message);
}
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6.7.5. acceptSecContext
void acceptSecContext(Stream inStream,
Stream outStream);
Called by the context acceptor upon receiving a token from the peer.
This call is equivalent to the byte array method. It may write an
output token to the outStream, which the application will need to
send to the peer for processing by its initSecContext method. The
application can check the isEstablished property to determine if the
context establishment phase is complete for this peer. A value of
"false" for isEstablished indicates that more tokens are expected to
be supplied to this method. Note that it is possible for the
acceptSecContext() method to return a token for the peer when
isEstablished is set to "true". This indicates that the token needs
to be sent to the peer, but the local end of the context is now fully
established.
The GSS-API authentication tokens contain a definitive start and end.
This method will attempt to read one of these tokens per invocation,
and may block on the stream if only part of the token is available.
Throws GSSException if an error is detected.
Parameters:
inStream Contains the token generated by the peer.
outStream Stream where the output token will be written.
During the final stage of context establishment, there
may be no bytes written.
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6.7.5.1. Example Code
// acquire server credentials
GSSCredential server = mgr.createCredential(...);
// create acceptor GSS-API context from the default provider
GSSContext context = mgr.createContext(server, null);
MemoryStream os = new MemoryStream();
Stream is = null;
try {
do {
is = recvToken();
context.acceptSecContext(is, os);
// possibly send token to peer
if (os.Length > 0)
sendToken(os);
// check if local context establishment is complete
if (context.isEstablished)
break;
} while (true);
} catch (GSSException e) {
Console.Writeline("GSS-API error: " + e.Message);
}
6.7.6. isEstablished
bool isEstablished;
Property which indicates the state of the context. A setting of
"true" for the property indicates that the context has been fully
established on the caller's side and no more tokens are needed from
the peer. The property should be examined after calls to
initSecContext() or acceptSecContext() when no GSSException is
thrown.
6.7.7. dispose
void dispose();
Releases any system resources and cryptographic information stored in
the context object. This will invalidate the context.
Throws GSSException if an error is detected.
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6.7.8. getWrapSizeLimit
int getWrapSizeLimit(int qop,
bool confReq,
int maxTokenSize);
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.
Throws GSSException if an error is detected.
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.
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6.7.9. wrap
byte[] wrap(byte[] inBuf,
int offset,
int len,
MessageProp msgProp);
Applies per-message security services over the established security
context. The method will return a token with a cryptographic MIC and
may optionally encrypt the specified inBuf. This method is
equivalent in functionality to its stream counterpart. The returned
byte array will contain both the MIC and the message.
The MessageProp object is instantiated by the application and used to
specify a QOP value which selects cryptographic algorithms, and a
privacy service to optionally encrypt the message. The underlying
mechanism that is used in the call may not be able to provide the
privacy service. It sets the actual privacy service that it does
provide in this MessageProp object which the caller should then query
upon return. If the mechanism is not able to provide the requested
QOP, it throws a GSSException with the BAD_QOP code.
Since some application-level protocols may wish to use tokens emitted
by wrap to provide "secure framing", implementations should support
the wrapping of zero-length messages.
The application will be responsible for sending the token to the
peer.
Throws GSSException if an error is detected.
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.
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6.7.10. wrap
void wrap(Stream inStream,
Stream outStream,
MessageProp msgProp);
Applies per-message security services over the established
security context. The method will produce a token with a
cryptographic MIC and may optionally encrypt the message in inStream.
The outStream will contain both the MIC and the message.
The MessageProp object is instantiated by the application and used to
specify a QOP value which selects cryptographic algorithms, and a
privacy service to optionally encrypt the message. The underlying
mechanism that is used in the call may not be able to provide the
privacy service. It sets the actual privacy service that it does
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.
Throws GSSException if an error is detected.
Parameters:
inStream Stream containing the application data to be
protected.
outStream The stream to write the protected message to.
The application is responsible for sending this to the
other peer for processing in its unwrap method.
msgProp Instance of MessageProp that is used by the
application to set the desired QOP and privacy state.
Set the desired QOP to 0 to request the default QOP.
Upon return from this method, this object will contain
the the actual privacy state that was applied to the
message by the underlying mechanism.
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6.7.11. unwrap
byte[] unwrap(byte[] inBuf,
int offset,
int len,
MessageProp msgProp);
Used by the peer application to process tokens generated with the
wrap call. This call is equal in functionality to its stream
counterpart. The method will return the message supplied in the peer
application to the wrap call, verifying the embedded MIC.
The MessageProp object is instantiated by the application and is used
by the underlying mechanism to return information to the caller such
as the QOP, whether confidentiality was applied to the message, and
other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted
by wrap to provide "secure framing", implementations should support
the wrapping and unwrapping of zero-length messages.
Throws GSSException if an error is detected.
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 stating whether the token was
a duplicate, old, out of sequence or arriving after a
gap.
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6.7.12. unwrap
void unwrap(Stream inStream,
Stream outStream,
MessageProp msgProp);
Used by the peer application to process tokens generated with the
wrap call. This call is equal in functionality to its byte array
counterpart. It will produce the message supplied in the peer
application to the wrap call, verifying the embedded MIC.
The MessageProp object is instantiated by the application and is used
by the underlying mechanism to return information to the caller such
as the QOP, whether confidentiality was applied to the message, and
other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted
by wrap to provide "secure framing", implementations should support
the wrapping and unwrapping of zero-length messages.
Throws GSSException if an error is detected.
Parameters:
inStream Stream containing the GSS-API wrap token received from
the peer.
outStream The stream to write the application message to.
msgProp Upon return from the method, this object will contain
the applied QOP, the privacy state of the message, and
supplementary information stating whether the token was
a duplicate, old, out of sequence or arriving after a
gap.
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6.7.13. getMIC
byte[] getMIC(byte[] inMsg,
int offset,
int len,
MessageProp msgProp);
Produces a token containing a cryptographic MIC for the supplied
message, for transfer to the peer application. Unlike wrap, which
encapsulates the user message in the returned token, only the message
MIC is returned in the output token. This method is identical in
functionality to its stream counterpart.
Note that privacy can only be applied through the wrap call.
Since some application-level protocols may wish to use tokens emitted
by getMIC to provide "secure framing", implementations should support
derivation of MICs from zero-length messages.
Throws GSSException if an error is detected.
Parameters:
inMsg Message to generate MIC over.
offset The offset within the inMsg where the token begins.
len The length of the token within the inMsg (starting at
the offset).
msgProp Instance of MessageProp that is used by the
application to set the desired QOP. Set the desired
QOP to 0 in msgProp to request the default QOP.
Alternatively pass in "null" for msgProp to request
default QOP.
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6.7.14. getMIC
void getMIC(Stream inStream,
Stream outStream,
MessageProp msgProp);
Produces a token containing a cryptographic MIC for the supplied
message, for transfer to the peer application. Unlike wrap, which
encapsulates the user message in the returned token, only the message
MIC is produced in the output token. This method is identical in
functionality to its byte array counterpart.
Note that privacy can only be applied through the wrap call.
Since some application-level protocols may wish to use tokens emitted
by getMIC to provide "secure framing", implementations should support
derivation of MICs from zero-length messages.
Throws GSSException if an error is detected.
Parameters:
inStream Stream containing the message to generate MIC over.
outStream Stream to write the GSS-API output token to.
msgProp Instance of MessageProp that is used by the
application to set the desired QOP. Set the desired
QOP to 0 in msgProp to request the default QOP.
Alternatively pass in "null" for msgProp to request
default QOP.
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6.7.15. verifyMIC
void verifyMIC(byte[] inTok,
int tokOffset,
int tokLen,
byte[] inMsg,
int msgOffset,
int msgLen,
MessageProp msgProp);
Verifies the cryptographic MIC, contained in the token parameter,
over the supplied message. This method is equivalent in
functionality to its stream counterpart.
The MessageProp object is instantiated by the application and is used
by the underlying mechanism to return information to the caller such
as the QOP indicating the strength of protection that was applied to
the message and other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted
by getMIC to provide "secure framing", implementations should support
the calculation and verification of MICs over zero-length messages.
Throws GSSException if an error is detected.
Parameters:
inTok Token generated by peer's getMIC method.
tokOffset The offset within the inTok where the token begins.
tokLen The length of the token within the inTok (starting at
the offset).
inMsg Application message to verify the cryptographic MIC
over.
msgOffset The offset within the inMsg where the message begins.
msgLen The length of the message within the inMsg (starting
at the offset).
msgProp Upon return from the method, this object will contain
the applied QOP and supplementary information stating
whether the token was a duplicate, old, out of sequence
or arriving after a gap. The confidentiality state will
be set to "false".
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6.7.16. verifyMIC
void verifyMIC(Stream tokStream,
Stream msgStream,
MessageProp msgProp);
Verifies the cryptographic MIC, contained in the token parameter,
over the supplied message. This method is equivalent in
functionality to its byte array counterpart.
The MessageProp object is instantiated by the application and is used
by the underlying mechanism to return information to the caller such
as the QOP indicating the strength of protection that was applied to
the message and other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted
by getMIC to provide "secure framing", implementations should support
the calculation and verification of MICs over zero-length messages.
Throws GSSException if an error is detected.
Parameters:
tokStream Stream containing the token generated by peer's
getMIC method.
msgStream Stream containing the application message to
verify the cryptographic MIC over.
msgProp Upon return from the method, this object will contain
the applied QOP and supplementary information stating
whether the token was a duplicate, old, out of sequence
or arriving after a gap. The confidentiality state will
be set to "false".
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6.7.17. export
byte[] export();
Provided to support the sharing of work between multiple processes.
This routine will typically be used by the context-acceptor, in an
application where a single process receives incoming connection
requests and accepts security contexts over them, then passes the
established context to one or more other processes for message
exchange.
This method deactivates the security context and creates an
interprocess token which, when passed to the byte array constructor
of the GSSContext interface in another process, will re-activate the
context in the second process. Only a single instantiation of a
given context may be active at any one time; a subsequent attempt by
a context exporter to access the exported security context will fail.
The implementation may constrain the set of processes by which the
interprocess token may be imported, either as a function of local
security policy, or as a result of implementation decisions. For
example, some implementations may constrain contexts to be passed
only between processes that run under the same account, or which are
part of the same process group.
The interprocess token may contain security-sensitive information
(for example cryptographic keys). While mechanisms are encouraged to
either avoid placing such sensitive information within interprocess
tokens, or to encrypt the token before returning it to the
application, in a typical GSS-API implementation this may not be
possible. Thus the application must take care to protect the
interprocess token, and ensure that any process to which the token is
transferred is trustworthy.
Throws GSSException if an error is detected.
6.7.18. mutualAuthentication
bool mutualAuthentication;
Mutual Authentication context property. When the value of this
property is set to "true" before the context creation process
begins then it indicates to the underlying mechanisms that mutual
authentication should be requested during context establishment.
The value of this property after context establishment is completed
indicates whether or not mutual authentication was performed when
the context was established.
Throws GSSException if an error is detected.
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6.7.19. replayDetection
bool replayDetection;
Replay Detection context property. When the value of this
property is set to "true" before the context creation process
begins then it indicates to the underlying mechanisms that the
replay detection service should be requested during context
establishment. The value of this property after context
establishment is completed or after the value of the isProtReady
property becomes "true" indicates whether or not the replay
detection service is in effect for the context.
Throws GSSException if an error is detected.
6.7.20. sequenceDetection
bool sequenceDetection;
Sequence Detection context property. When the value of this
property is set to "true" before the context creation process
begins then it indicates to the underlying mechanisms that the
sequence checking service should be requested during context
establishment. The value of this property after context
establishment is completed or after the value of the isProtReady
property becomes "true" indicates whether or not the sequence
checking service is in effect for the context.
Throws GSSException if an error is detected.
6.7.21. credentialDelegation
bool credentialDelegation;
Credential Delegate context property. When the value of this
property is set to "true" before the context creation process
begins then it indicates to the underlying mechanisms that
credential delegation is desired. The value of this property after
context establishment is completed or after the value of the
isProtReady property becomes "true" indicates whether or not
credential delegation was performed when the context was established.
Throws GSSException if an error is detected.
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6.7.22. anonymity
bool anonymity;
Anonimity context property. When the value of this property is set
to "true" before the context creation process begins then it
indicates to the underlying mechanisms that anonymity has been
requested. The value of this property after context establishment is
completed or after the value of the isProtReady property becomes
"true" indicates whether or not anonymity was used during the
establishment of the context.
Throws GSSException if an error is detected.
6.7.23. confidentiality
bool confidentiality;
Confidentiality context property. When the value of this
property is set to "true" before the context creation process
begins then it indicates to the underlying mechanisms that the
confidentiality service should be requested during context
establishment. The value of this property after context
establishment is completed or after the value of the isProtReady
property becomes "true" indicates whether or not the confidentiality
service is in effect for the context.
Throws GSSException if an error is detected.
6.7.24. integrity
bool integrity;
Integrity context property. When the value of this property is set
to "true" before the context creation process begins then it
indicates to the underlying mechanisms that the integrity service
should be requested during context establishment. The value of this
property after context establishment is completed or after the value
of the isProtReady property becomes "true" indicates whether or not
the integrity service is in effect for the context.
Throws GSSException if an error is detected.
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6.7.25. lifetime
int lifetime;
Lifetime context property. The value of this property indicates
the lifetime in seconds for the context. This property can only be
set by the initiator before the context creation process is
started. Set the property to GSSConstants.INDEFINITE_LIFETIME and
GSSConstants.DEFAULT_LIFETIME to request indefinite or default
context lifetime. The value of this property after context
establishment is completed or after the value of the isProtReady
property becomes "true" indicates the remaining lifetime for the
context.
Throws GSSException if an error is detected.
6.7.26. channelBinding
ChannelBinding channelBinding;
Channel Binding context property. This value of this property can be
set to specify a Channel Binding to be used during context
establishment. This property can only be set before the context
creation process begins.
Throws GSSException if an error is detected.
6.7.27. isTransferable
bool isTransferable;
Property which indicates whether or not the context can be
transferred to other processes. The value of this property is only
valid on fully established contexts.
Throws GSSException if an error is detected.
6.7.28. isProtReady
bool isProtReady;
Property which indicates whether or not 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.
Throws GSSException if an error is detected.
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6.7.29. srcName
GSSName srcName;
Property which contains the name of the context initiator. The
value of this property is valid only after the context is fully
established or the isProtReady property is set to "true". The
property is guaranteed to be set to an MN after it becomes valid.
Throws GSSException if an error is detected.
6.7.30. targName
GSSName targName;
Property which contains the name of the context target (acceptor).
The value of this property is valid only after the context is fully
established or the isProtReady property is set to "true". The
property is guaranteed to be set to an MN after it becomes valid.
Throws GSSException if an error is detected.
6.7.31. mechanism
Oid mechanism;
Property which contains the mechanism oid for the context.
The value of this property may change from time to time if mechanism
negotiation takes place.
Throws GSSException if an error is detected.
6.7.32. delegatedCredential
GSSCredential delegatedCredential;
Property which contains the credential delegated by the context
initiator. The value of this property is only valid on the
acceptors side after the context has been fully established and if
the credentialDelegation property is set to "true".
Throws GSSException if an error is detected.
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6.7.33. isInitiator
bool isInitiator;
Property which contains indication of whether or not the context
creation process started on this side. The value of this property
is only valid after the context creation process has started.
Throws GSSException if an error is detected.
6.8. public class MessageProp
This is a utility class used within the per-message GSSContext
methods to convey per-message properties.
When used with the GSSContext interface's wrap and getMIC methods, an
instance of this class is used to indicate the desired QOP and to
request if confidentiality services are to be applied to caller
supplied data (wrap only). To request default QOP, the value of 0
should be used for QOP.
When used with the unwrap and verifyMIC methods of the GSSContext
interface, an instance of this class will be used to indicate the
applied QOP and confidentiality services over the supplied message.
In the case of verifyMIC, the confidentiality state will always be
"false". Upon return from these methods, this object will also
contain any supplementary status values applicable to the processed
token. The supplementary status values can indicate old tokens, out
of sequence tokens, gap tokens or duplicate tokens.
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6.8.1. Constructors
public MessageProp(bool privState);
Constructor which sets QOP to 0 indicating that the default QOP is
requested.
Throws GSSException if an error is detected.
Parameters:
privState The desired privacy state. "true" for privacy and
"false" for integrity only.
public MessageProp(int qop, bool privState);
Constructor which sets the values for the qop and privacy state.
Throws GSSException if an error is detected.
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.
6.8.2. QOP
public int QOP;
QOP property. Use this to set or get the value of the QOP property.
Set to 0 to request the default value.
Throws GSSException if an error is detected.
6.8.3. privacy
public bool privacy;
Privacy property. Use this to set or get the value of the privacy
property.
Throws GSSException if an error is detected.
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6.8.4. minorStatus
public int minorStatus;
Minor Status property. This property maintains the minor status that
the underlying mechanism might have set.
Throws GSSException if an error is detected.
6.8.5. minorString
public string minorString;
Minor String property. This property maintains a string explaining
the mechanism specific error code. The string will be empty if no
mechanism error code has been set.
Throws GSSException if an error is detected.
6.8.6. isDuplicateToken
public bool isDuplicateToken;
Is Duplicate Token property. The value of this property indicates
whether or not the token is a duplicate of an earlier token.
Throws GSSException if an error is detected.
6.8.7. isOldToken
public bool isOldToken;
Is Old Token property. The value of this property indicates whether
or not the token's validity period has expired.
Throws GSSException if an error is detected.
6.8.8. isUnseqToken
public bool isUnseqToken;
Is Un-sequenced Token property. The value of this property indicates
whether or not the token is being processed out of sequence.
Throws GSSException if an error is detected.
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6.8.9. isGapToken
public bool isGapToken;
Is Gap Token property. The value of this property indicates
whether or not an expected per-message was not received.
Throws GSSException if an error is detected.
6.9. 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.
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6.9.1. Constructors
public ChannelBinding(EndPoint initAddr,
EndPoint acceptAddr,
byte[] appData);
Create a ChannelBinding object with user supplied address information
and data. "null" values can be used for any fields which the
application does not want to specify.
Throws GSSException if an error is detected.
Parameters:
initAddr The address of the context initiator. "null" value
can be supplied to indicate that the application does
not want to set this value.
acceptAddrThe address of the context acceptor. "null" value can
be supplied to indicate that the application does not
want to set this value.
appData Application supplied data to be used as part of the
channel bindings. "null" value can be supplied to
indicate that the application does not want to set
this value.
public ChannelBinding(byte[] appData);
Creates a ChannelBinding object without any addressing information.
Throws GSSException if an error is detected.
Parameters:
appData Application supplied data to be used as part of the
channel bindings.
6.9.2. initiatorAddress
public EndPoint initiatorAddress;
Initiator Address property. The value of this property indicates
the initiator's address for the channel binding. The property value
will be set to "null" if not set.
Throws GSSException if an error is detected.
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6.9.3. acceptorAddress
public EndPoint acceptorAddress;
Acceptor Address property. The value of this property indicates
the acceptor's address for the channel binding. The property value
will be set to "null" if not set.
Throws GSSException if an error is detected.
6.9.4. applicationData
public byte[] applicationData;
Application Data property. The value of this property indicates
the application data being used for the channel binding. The
property value will be set to "null" if not set.
Throws GSSException if an error is detected.
6.9.8. Equals
public override bool Equals(Object obj);
Tests whether or not two channel binding objects match.
Throws GSSException if an error is detected.
Parameters:
obj Another channel binding to compare with.
6.10. public class Oid
This class represents Universal Object Identifiers (Oids) and their
associated operations.
Oids are hierarchically globally-interpretable identifiers used
within the GSS-API framework to identify mechanisms and name formats.
The structure and encoding of Oids is defined in ISOIEC-8824 and
ISOIEC-8825. For example the Oid representation of Kerberos V5
mechanism is "1.2.840.113554.1.2.2"
The GSSName name class contains public static Oid objects
representing the standard name types defined in GSS-API.
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6.10.1. Constructors
public Oid(string strOid);
Creates an Oid object from a string representation of its integer
components (e.g. "1.2.840.113554.1.2.2").
Throws GSSException if an error is detected.
Parameters:
strOid The string representation for the oid.
public Oid(Stream derOid);
Creates an Oid object from its DER encoding. This refers to the full
encoding including tag and length. The structure and encoding of
Oids is defined in ISOIEC-8824 and ISOIEC-8825. This method is
identical in functionality to its byte array counterpart.
Throws GSSException if an error is detected.
Parameters:
derOid Stream containing the DER encoded oid.
public Oid(byte[] DEROid);
Creates an Oid object from its DER encoding. This refers to the full
encoding including tag and length. The structure and encoding of
Oids is defined in ISOIEC-8824 and ISOIEC-8825. This method is
identical in functionality to its byte array counterpart.
Throws GSSException if an error is detected.
Parameters:
derOid Byte array storing a DER encoded oid.
6.10.2. ToString
public override 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").
Throws GSSException if an error is detected.
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6.10.3. Equals
public override bool Equals(Object Obj);
Tests if two OID objects represent the same oid value.
Throws GSSException if an error is detected.
Parameters:
obj Another Oid object to compare with.
6.10.4. DER
public byte[] DER;
DER property. Property of the object which refers to its full ASN.1
DER encoding, the property includes the tag and length.
Throws GSSException if an error is detected.
6.10.5. containedIn
public bool containedIn(Oid[] oids);
Method to test if an Oid object is contained within the
supplied Oid object array.
Throws GSSException if an error is detected.
Parameters:
oids An array of oids to search.
6.11. public class GSSException : Exception
This exception is thrown whenever a fatal GSS-API error occurs
including mechanism specific errors. It may contain both, the major
and minor, GSS-API status codes. The mechanism implementers are
responsible for setting appropriate minor status codes when throwing
this exception. Aside from delivering the numeric error code(s) to
the caller, this class performs the mapping from their numeric values
to textual representations. All C# GSS-API methods and properties
are declared throwing this exception.
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6.11.1. Constants
All valid major GSS-API error code values are declared as constants
in this class.
public const int BAD_BINDINGS
Channel bindings mismatch error.
public const int BAD_MECH
Unsupported mechanism requested error.
public const int BAD_NAME
Invalid name provided error.
public const int BAD_NAMETYPE
Name of unsupported type provided error.
public const int BAD_STATUS
Invalid status code error - this is the default status value.
public const int BAD_MIC
Token had invalid integrity check error.
public const int CONTEXT_EXPIRED
Specified security context expired error.
public const int CREDENTIALS_EXPIRED
Expired credentials detected error.
public const int DEFECTIVE_CREDENTIAL
Defective credential error.
public const int DEFECTIVE_TOKEN
Defective token error.
public const int FAILURE
General failure, unspecified at GSS-API level.
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public const int NO_CONTEXT
Invalid security context error.
public const int NO_CRED
Invalid credentials error.
public const int BAD_QOP
Unsupported QOP value error.
public const int UNAUTHORIZED
Operation unauthorized error.
public const int UNAVAILABLE
Operation unavailable error.
public const int DUPLICATE_ELEMENT
Duplicate credential element requested error.
public const int NAME_NOT_MN
Name contains multi-mechanism elements error.
public const int DUPLICATE_TOKEN
The token was a duplicate of an earlier token. This is a fatal error
code that may occur during context establishment. It is not used to
indicate supplementary status values. The MessageProp object is used
for that purpose.
public const int OLD_TOKEN
The token's validity period has expired. This is a fatal error code
that may occur during context establishment. It is not used to
indicate supplementary status values. The MessageProp object is used
for that purpose.
public const int UNSEQ_TOKEN
A later token has already been processed. This is a fatal error code
that may occur during context establishment. It is not used to
indicate supplementary status values. The MessageProp object is used
for that purpose.
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public const int GAP_TOKEN
An expected per-message token was not received. This is a fatal
error code that may occur during context establishment. It is not
used to indicate supplementary status values. The MessageProp object
is used for that purpose.
6.11.2. Constructors
public GSSException(int majorCode);
Creates a GSSException object with a specified major code.
Parameters:
majorCode The GSS error code causing this exception to be
thrown.
public GSSException(int majorCode, int minorCode,
string minorString);
Creates a GSSException object with the specified major code, minor
code, and minor code textual explanation. This constructor is to be
used when the exception is originating from the security mechanism.
It allows to specify the GSS code and the mechanism code.
Parameters:
majorCode The GSS error code causing this exception to be
thrown.
minorCode The mechanism error code causing this exception
to be thrown.
minorString The textual explanation of the mechanism error
code.
6.11.3. major
public int major;
Major code property. Property of the object representing the GSS
error code that caused the exception to be thrown.
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6.11.4. minor
public int minor;
Minor code property. Property of the object representing the
mechanism error code that caused the exception to be thrown. The
minor code property is set by the underlying mechanism. A setting of
0 for this property indicates that the mechanism error code is not
set.
6.11.5. majorString
public string majorString;
Major string property. Property of the object explaining the GSS
major error code causing the exception to be thrown.
6.11.6. minorString
public string minorString;
Minor string property. Property of the object explaining the
mechanism specific error code causing the exception to be thrown.
The string will be empty if no mechanism error code has been set.
6.11.7. ToString
public override string ToString();
Returns a textual representation of both the major and minor status
codes.
6.11.8. Message
public string Message;
Message property. Error message explaining the reason for the
exception.
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7. Sample Applications
7.1. Simple GSS Context Initiator
using org.ietf.gss;
/**
* This is a partial sketch for a simple client program that acts
* as a GSS context initiator. It illustrates how to use the C#
* bindings for the GSS-API specified in
* Generic Security Service API Version 2 : C# bindings
*
*
* This code sketch assumes the existence of a GSS-API
* implementation that supports the mechanism that it will need and
* is present as a library package (org.ietf.jgss) either as part of
* the standard JRE or in the CLASSPATH the application specifies.
*/
public class SimpleClient {
private string serviceName; // name of peer (ie. server)
private GSSCredential clientCred = null;
private GSSContext context = null;
private Oid mech; // underlying mechanism to use
private GSSManager mgr = GSSManager.getInstance();
...
...
private void clientActions() {
initializeGSS();
establishContext();
doCommunication();
}
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/**
* Acquire credentials for the client.
*/
private void initializeGSS() {
try {
clientCred = mgr.createCredential(null /*default princ*/,
GSSConstants.INDEFINITE_LIFETIME /* max lifetime */,
mech /* mechanism to use */,
GSSCredentialUsage.INITIATE_ONLY /* init context */);
Console.Writeline("GSSCredential created for " +
cred.getName().ToString());
Console.Writeline("Credential lifetime (sec)=" +
cred.getRemainingLifetime());
} catch (GSSException e) {
Console.Writeline("GSS-API error in credential acquisition:"
+ e.Message);
...
...
}
...
...
}
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/**
* 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,
GSSNameTypes.NT_HOSTBASED_SERVICE);
context = mgr.createContext(
peer,
mech,
gssCred,
GSSConstants.INDEFINITE_LIFETIME/*lifetime*/);
// Will need to support confidentiality
context.confidentiality = true;
while (!context.isEstablished) {
outToken = context.initSecContext(inToken,
0,
inToken.length);
if (outToken != null)
writeGSSToken(outToken);
if (!context.isEstablished)
inToken = readGSSToken();
}
GSSName peer = context.srcName;
Console.Writeline(
"Security context established with " +
peer +
" using underlying mechanism " + mech.toString());
} catch (GSSException e) {
Console.Writeline(
"GSS-API error during context establishment: " +
e.Message);
}
...
}
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/**
* Sends some data to the server and reads back the
* response.
*/
private void doCommunication() {
byte[] inToken = null;
byte[] outToken = null;
byte[] buffer;
// Container for multiple input-output arguments to and
// from the per-message routines (e.g., wrap/unwrap).
MessageProp messgInfo = new MessageProp();
try {
/*
* 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.privacy = false;
outToken = context.wrap(buffer,
0,
buffer.length,
messgInfo);
writeGSSToken(outToken);
/*
* Now read the response from the server.
*/
inToken = readGSSToken();
buffer = context.unwrap(inToken,
0,
inToken.length,
messgInfo);
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// All ok if no exception was thrown!
GSSName peer = context.srcName;
Console.Writeline("Message from " +
peer.ToString() +
" arrived.");
Console.Writeline("Was it encrypted? " +
messgInfo.privacy);
Console.Writeline("Duplicate Token? " +
messgInfo.isDuplicateToken);
Console.Writeline("Old Token? " +
messgInfo.isOldToken);
Console.Writeline("Unsequenced Token? " +
messgInfo.isUnseqToken);
Console.Writeline("Gap Token? " +
messgInfo.isGapToken);
...
...
} catch (GSSException e) {
Console.Writeline("GSS-API error in per-message calls: " +
e.Message);
...
...
}
...
...
} // end of doCommunication method
...
...
} // end of class SimpleClient
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7.2. Simple GSS Context Acceptor
using org.ietf.gss;
/**
* This is a partial sketch for a simple server program that acts
* as a GSS context acceptor. It illustrates how to use the C#
* bindings for the GSS-API specified in
* Generic Security Service API Version 2 : C# 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.
*/
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() {
...
...
mgr = GSSManager.getInstance();
name = mgr.createName(serviceName,
GSSNameTypes.NT_HOSTBASED_SERVICE);
cred = mgr.createCredential(name,
GSSConstants.INDEFINITE_LIFETIME,
null,
GSSCredentialUsage.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;
GSSName peer;
// Container for multiple input-output arguments to and
// from the per-message routines (ie. wrap/unwrap).
MessageProp supplInfo = new MessageProp();
GSSContext secContext = null;
try {
// Now do the context establishment loop
GSSContext context = mgr.createContext(cred);
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while (!context.isEstablished) {
inToken = readGSSToken();
outToken = context.acceptSecContext(inToken,
0,
inToken.length);
if (outToken != null)
writeGSSToken(outToken);
}
// SimpleServer wants confidentiality to be
// available. Check for it.
if (!context.confidentiality) {
...
...
}
GSSName peer = context.srcName;
Oid mech = context.getMech();
Console.Writeline("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!
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// Print other supplementary per-message status
// information
Console.Writeline("Message from " +
peer.ToString() +
" arrived.");
Console.Writeline("Was it encrypted? " +
supplInfo.privacy);
Console.Writeline("Duplicate Token? " +
supplInfo.isDuplicateToken);
Console.Writeline("Old Token? " + supplInfo.isOldToken);
Console.Writeline("Unsequenced Token? " +
supplInfo.isUnseqToken);
Console.Writeline("Gap Token? " + supplInfo.isGapToken);
/*
* Now process the bytes and send back an encrypted
* response.
*/
buffer = serverProcess(buffer);
// Encipher it and send it across
supplInfo.privacy = true; // privacy requested
supplInfo.QOP = 0; // default QOP
outToken = context.wrap(buffer,
0,
buffer.length,
supplInfo);
writeGSSToken(outToken);
} catch (GSSException e) {
Console.Writeline("GSS-API Error: " + e.Message);
// Alternatively, could read the e.majorString
// and the e.minorString properties.
Console.Writeline("Abandoning security context.");
...
...
}
...
...
} // end of run method in ServerThread
} // end of inner class ServerThread
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...
...
} // end of class SimpleServer
8. Security Considerations
The level of security that can be obtained by using GSS-API is
dependent on the following factors:
- The integrity of the libraries being utilized.
- The integrity of the systems where the application executes.
- The GSS-API mechanism utilized.
- The GSS-API services utilized by the application.
- The way that the application utilizes GSS-API.
Application as well as system installers need to be aware of
the factors mentioned above to avoid security vulnerabilities.
9. IANA Considerations
This document has no actions for IANA.
10. Acknowledgments
The author would like to thank the following:
Kabat, J. and Upadhyay, M. for writing the Generic Security Service
API Version 2 : Java Bindings specification [RFC2853] that
constitutes the basis of this work.
Jeff Altman for his support and suggestions.
Corby Morris for his initial implementation.
Funding for the RFC Editor function is currently provided by the
Internet Society.
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11. Normative References
[RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2853] Kabat, J. and Upadhyay, M., "Generic Security Service API
Version 2 : Java Bindings", RFC 2853, June 2000.
[RFC1509] Wray, J., "Generic Security Service API : C-bindings",
RFC 1509, September 1993.
12. Authors' Addresses
Juan Carlos Luciani
Novell, Inc.
1800 South Novell Place
Provo, Utah 84606
US
EMail: jluciani@novell.com
13. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
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14. Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
15. Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
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