This document is obsolete. Please
refer to RFC 8353.
Network Working Group M. Upadhyay Request for Comments: 5653 Google Obsoletes: 2853 S. Malkani Category: Standards Track ActivIdentity August 2009
Generic Security Service API Version 2: Java Bindings Update
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 updates the Java bindings for the GSS-API that are specified in "Generic Security Service API Version 2 : Java Bindings" (RFC 2853). This document obsoletes RFC 2853 by making specific and incremental clarifications and corrections to it in response to identification of transcription errors and implementation experience.
The GSS-API is described at a language-independent conceptual level in "Generic Security Service Application Program Interface Version 2, Update 1" (RFC 2743). The GSS-API allows a caller application to authenticate a principal identity, to delegate rights to a peer, and to apply security services such as confidentiality and integrity on a per-message basis. Examples of security mechanisms defined for GSS- API are "The Simple Public-Key GSS-API Mechanism" (RFC 2025) and "The Kerberos Version 5 Generic Security Service Application Program Interface (GSS-API) Mechanism: Version 2" (RFC 4121).
Status of This Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document.
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This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.
This document specifies Java language bindings for the Generic Security Services Application Programming Interface version 2 (GSS- API). GSS-API version 2 is described in a language-independent format in RFC 2743 [GSSAPIv2-UPDATE]. The GSS-API allows a caller application to authenticate a principal identity, to delegate rights to a peer, and to apply security services such as confidentiality and integrity on a per-message basis.
This document and its predecessor, RFC 2853 [RFC2853], leverage the work done by the working group (WG) in the area of RFC 2743 [GSSAPIv2-UPDATE] and the C-bindings of RFC 2744 [GSSAPI-Cbind]. Whenever appropriate, text has been used from the C-bindings document (RFC 2744) to explain generic concepts and provide direction to the implementors.
The design goals of this API have been to satisfy all the functionality defined in RFC 2743 [GSSAPIv2-UPDATE] and to provide these services in an object-oriented method. The specification also aims to satisfy the needs of both types of Java application developers, those who would like access to a "system-wide" GSS-API implementation, as well as those who would want to provide their own "custom" implementation.
A system-wide implementation is one that is available to all applications in the form of a library package. It may be the standard package in the Java runtime environment (JRE) being used or it may be additionally installed and accessible to any application via the CLASSPATH.
A custom implementation of the GSS-API, on the other hand, is one that would, in most cases, be bundled with the application during distribution. It is expected that such an implementation would be meant to provide for some particular need of the application, such as support for some specific mechanism.
The design of this API also aims to provide a flexible framework to add and manage GSS-API mechanisms. GSS-API leverages the Java Cryptography Architecture (JCA) provider model to support the plugability of mechanisms. Mechanisms can be added on a system-wide basis, where all users of the framework will have them available. The specification also allows for the addition of mechanisms per- instance of the GSS-API.
Lastly, this specification presents an API that will naturally fit within the operation environment of the Java platform. Readers are assumed to be familiar with both the GSS-API and the Java platform.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
The following license applies to all code segments included in this specification. If code is extracted from this specification, please include the following text in the code:
/* -- Copyright (c) 2009 IETF Trust and the persons identified as -- authors of the code. All rights reserved. -- -- Redistribution and use in source and binary forms, with or without -- modification, are permitted provided that the following conditions -- are met: -- -- - Redistributions of source code must retain the above copyright -- notice, this list of conditions and the following disclaimer. -- -- - Redistributions in binary form must reproduce the above copyright -- notice, this list of conditions and the following disclaimer in -- the documentation and/or other materials provided with the -- distribution. -- -- - Neither the name of Internet Society, IETF or IETF Trust, nor the -- names of specific contributors, may be used to endorse or promote -- products derived from this software without specific prior -- written permission. -- -- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND -- CONTRIBUTORS 'AS IS' AND ANY EXPRESS OR IMPLIED WARRANTIES, -- INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF -- MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE -- DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS -- BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, -- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED -- TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, -- DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON -- ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, -- OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -- OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE -- POSSIBILITY OF SUCH DAMAGE. -- -- This code is part of RFC 5653; see the RFC itself for full legal -- notices. */
"Generic Security Service Application Programming Interface, Version 2" [GSSAPIv2-UPDATE] defines a generic security API to calling applications. It allows a communicating application to authenticate the user associated with another application, to delegate rights to another application, and to apply security services such as confidentiality and integrity on a per-message basis.
There are four stages to using GSS-API:
1) The application acquires a set of credentials with which it may prove its identity to other processes. The application's credentials vouch for its global identity, which may or may not be related to any local username under which it may be running.
2) A pair of communicating applications establish a joint security context using their credentials. The security context encapsulates shared state information, which is required in order that per-message security services may be provided. Examples of state information that might be shared between applications as part of a security context are cryptographic keys and message sequence numbers. As part of the establishment of a security context, the context initiator is authenticated to the responder, and may require that the responder is authenticated back to the initiator. The initiator may optionally give the responder the right to initiate further security contexts, acting as an agent or delegate of the initiator. This transfer of rights is termed "delegation", and is achieved by creating a set of credentials, similar to those used by the initiating application, but which may be used by the responder.
A GSSContext object is used to establish and maintain the shared information that makes up the security context. Certain GSSContext methods will generate a token, which applications treat as cryptographically protected, opaque data. The caller of such a GSSContext method is responsible for transferring the token to the peer application, encapsulated if necessary in an application-to- application protocol. On receipt of such a token, the peer application should pass it to a corresponding GSSContext method which will decode the token and extract the information, updating the security context state information accordingly.
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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.
This section discusses the optional services that a context initiator may request of the GSS-API before the context establishment. Each of these services is requested by calling the appropriate mutator method in the GSSContext object before the first call to init is performed. Only the context initiator can request context flags.
The optional services defined are:
Delegation: The (usually temporary) transfer of rights from initiator to acceptor, enabling the acceptor to authenticate itself as an agent of the initiator.
Mutual Authentication: In addition to the initiator authenticating its identity to the context acceptor, the context acceptor should also authenticate itself to the initiator.
Replay Detection: In addition to providing message integrity services, GSSContext per-message operations of getMIC and wrap should include message numbering information to enable verifyMIC and unwrap to detect if a message has been duplicated.
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Out-of-Sequence Detection: In addition to providing message integrity services, GSSContext per-message operations (getMIC and wrap) should include message sequencing information to enable verifyMIC and unwrap to detect if a message has been received out of sequence.
Anonymous Authentication: The establishment of the security context should not reveal the initiator's identity to the context acceptor.
Some mechanisms may not support all optional services, and some mechanisms may only support some services in conjunction with others. The GSSContext interface offers query methods to allow the verification by the calling application of which services will be available from the context when the establishment phase is complete. In general, if the security mechanism is capable of providing a requested service, it should do so even if additional services must be enabled in order to provide the requested service. If the mechanism is incapable of providing a requested service, it should proceed without the service leaving the application to abort the context establishment process if it considers the requested service to be mandatory.
Some mechanisms may specify that support for some services is optional, and that implementors of the mechanism need not provide it. This is most commonly true of the confidentiality service, often because of legal restrictions on the use of data-encryption, but may apply to any of the services. Such mechanisms are required to send at least one token from acceptor to initiator during context establishment when the initiator indicates a desire to use such a service, so that the initiating GSS-API can correctly indicate whether the service is supported by the acceptor's GSS-API.
The GSS-API allows delegation to be controlled by the initiating application via the requestCredDeleg method before the first call to init has been issued. Some mechanisms do not support delegation, and for such mechanisms, attempts by an application to enable delegation are ignored.
The acceptor of a security context, for which the initiator enabled delegation, can check if delegation was enabled by using the getCredDelegState method of the GSSContext interface. In cases when it is enabled, the delegated credential object can be obtained by calling the getDelegCred method. The obtained GSSCredential object may then be used to initiate subsequent GSS-API security contexts as an agent or delegate of the initiator. If the original initiator's
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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 override other mechanism-specific delegation controls. If the application instructs the GSSContext object that delegation is not desired, then the implementation must not permit delegation to occur. This is an exception to the general rule that a mechanism may enable services even if they are not requested -- delegation may only be provided at the explicit request of the application.
Usually, a context acceptor will require that a context initiator authenticate itself so that the acceptor may make an access-control decision prior to performing a service for the initiator. In some cases, the initiator may also request that the acceptor authenticate itself. GSS-API allows the initiating application to request this mutual authentication service by calling the requestMutualAuth method of the GSSContext interface with a "true" parameter before making the first call to init. The initiating application is informed as to whether or not the context acceptor has authenticated itself. Note that some mechanisms may not support mutual authentication, and other mechanisms may always perform mutual authentication, whether or not the initiating application requests it. In particular, mutual authentication may be required by some mechanisms in order to support replay or out-of-sequence message detection, and for such mechanisms, a request for either of these services will automatically enable mutual authentication.
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
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methods of the GSSContext interface, and verified by the peer application by calling verifyMIC or unwrap for the peer's GSSContext object.
The getMIC method calculates a cryptographic checksum of an application message, and returns that checksum in a token. The application should pass both the token and the message to the peer application, which presents them to the verifyMIC method of the peer's GSSContext object.
The wrap method calculates a cryptographic checksum of an application message, and places both the checksum and the message inside a single token. The application should pass the token to the peer application, which presents it to the unwrap method of the peer's GSSContext object to extract the message and verify the checksum.
Either pair of routines may be capable of detecting out-of-sequence message delivery or the duplication of messages. Details of such mis-ordered messages are indicated through supplementary query methods of the MessageProp object that is filled in by each of these routines.
A mechanism need not maintain a list of all tokens that have been processed in order to support these status codes. A typical mechanism might retain information about only the most recent "N" tokens processed, allowing it to distinguish duplicates and missing tokens within the most recent "N" messages; the receipt of a token older than the most recent "N" would result in the isOldToken method of the instance of MessageProp to return "true".
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
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request will not be honored. An authentication token will still be generated, but the application is always informed if a requested service is unavailable, and has the option to abort context establishment if anonymity is valued above the other security services that would require a context to be established.
In addition to informing the application that a context is established anonymously (via the isAnonymous method of the GSSContext class), the getSrcName method of the acceptor's GSSContext object will, for such contexts, return a reserved internal-form name, defined by the implementation.
The toString method for a GSSName object representing an anonymous entity will return a printable name. The returned value will be syntactically distinguishable from any valid principal name supported by the implementation. The associated name-type object identifier will be an oid representing the value of NT_ANONYMOUS. This name- type oid will be defined as a public, static Oid object of the GSSName class. The printable form of an anonymous name should be chosen such that it implies anonymity, since this name may appear in, for example, audit logs. For example, the string "<anonymous>" might be a good choice, if no valid printable names supported by the implementation can begin with "<" and end with ">".
When using the equal method of the GSSName interface, and one of the operands is a GSSName instance representing an anonymous entity, the method must return "false".
If a GSSContext supports the confidentiality service, wrap method may be used to encrypt application messages. Messages are selectively encrypted, under the control of the setPrivacy method of the MessageProp object used in the wrap method.
GSS-APIv2 provides functionality that allows a security context to be transferred between processes on a single machine. These are implemented using the export method of GSSContext and a byte array constructor of the same class. The most common use for such a feature is a client-server design where the server is implemented as a single process that accepts incoming security contexts, which then launches child processes to deal with the data on these contexts. In such a design, the child processes must have access to the security context object created within the parent so that they can use per- message protection services and delete the security context when the communication session ends.
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Since the security context data structure is expected to contain sequencing information, it is impractical in general to share a context between processes. Thus, the GSSContext interface provides an export method that the process, which currently owns the context, can call to declare that it has no intention to use the context subsequently, and to create an inter-process token containing information needed by the adopting process to successfully recreate the context. After successful completion of export, the original security context is made inaccessible to the calling process by GSS- API, and any further usage of this object will result in failures. The originating process transfers the inter-process token to the adopting process, which creates a new GSSContext object using the byte array constructor. The properties of the context are equivalent to that of the original context.
The inter-process token may contain sensitive data from the original security context (including cryptographic keys). Applications using inter-process tokens to transfer security contexts must take appropriate steps to protect these tokens in transit.
Implementations are not required to support the inter-process transfer of security contexts. Calling the isTransferable method of the GSSContext interface will indicate if the context object is transferable.
Some mechanisms may allow the per-message services to be used before the context establishment process is complete. For example, a mechanism may include sufficient information in its initial context- level tokens for the context acceptor to immediately decode messages protected with wrap or getMIC. For such a mechanism, the initiating application need not wait until subsequent context-level tokens have been sent and received before invoking the per-message protection services.
An application can invoke the isProtReady method of the GSSContext class to determine if the per-message services are available in advance of complete context establishment. Applications wishing to use per-message protection services on partially established contexts should query this method before attempting to invoke wrap or getMIC.
Java provides the implementors with not just a syntax for the language, but also an operational environment. For example, memory is automatically managed and does not require application intervention. These language features have allowed for a simpler API and have led to the elimination of certain GSS-API functions.
Moreover, the JCA defines a provider model that allows for implementation-independent access to security services. Using this model, applications can seamlessly switch between different implementations and dynamically add new services. The GSS-API specification leverages these concepts by the usage of providers for the mechanism implementations.
The classes and interfaces defined in this document reside in the package called "org.ietf.jgss". Applications that wish to make use of this API should import this package name as shown in section 8.
The Java security API's use a provider architecture that allows applications to be implementation independent and security API implementations to be modular and extensible. The java.security.Provider class is an abstract class that a vendor extends. This class maps various properties that represent different security services that are available to the names of the actual vendor classes that implement those services. When requesting a service, an application simply specifies the desired provider and the API delegates the request to service classes available from that provider.
Using the Java security provider model insulates applications from implementation details of the services they wish to use. Applications can switch between providers easily and new providers can be added as needed, even at runtime.
The GSS-API may use providers to find components for specific underlying security mechanisms. For instance, a particular provider might contain components that will allow the GSS-API to support the Kerberos v5 mechanism [RFC4121] and another might contain components to support the Simple Public-Key GSS-API Mechanism (SPKM) [RFC2025]. By delegating mechanism-specific functionality to the components obtained from providers, the GSS-API can be extended to support an arbitrary list of mechanism.
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How the GSS-API locates and queries these providers is beyond the scope of this document and is being deferred to a Service Provider Interface (SPI) specification. The availability of such an SPI specification is not mandatory for the adoption of this API specification nor is it mandatory to use providers in the implementation of a GSS-API framework. However, by using the provider framework together with an SPI specification, one can create an extensible and implementation-independent GSS-API framework.
All numeric values are declared as "int" primitive Java type. The Java specification guarantees that this will be a 32-bit two's complement signed number.
Throughout this API, the "boolean" primitive Java type is used wherever a boolean value is required or returned.
Java byte arrays are used to represent opaque data types that are consumed and produced by the GSS-API in the form of tokens. Java arrays contain a length field that enables the users to easily determine their size. The language has automatic garbage collection that alleviates the need by developers to release memory and simplifies buffer ownership issues.
The String object will be used to represent all textual data. The Java String object transparently treats all characters as two-byte Unicode characters, which allows support for many locals. All routines returning or accepting textual data will use the String object.
An Oid object will be used to represent Universal Object Identifiers (Oids). Oids are ISO-defined, hierarchically globally interpretable identifiers used within the GSS-API framework to identify security mechanisms and name formats. The Oid object can be created from a string representation of its dot notation (e.g., "1.3.6.1.5.6.2") as well as from its ASN.1 DER encoding. Methods are also provided to test equality and provide the DER representation for the object.
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An important feature of the Oid class is that its instances are immutable -- i.e., there are no methods defined that allow one to change the contents of an Oid. 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.
The Java bindings represent object identifier sets as arrays of Oid objects. All Java arrays contain a length field, which allows for easy manipulation and reference.
In order to support the full functionality of RFC 2743 [GSSAPIv2- UPDATE], the Oid class includes a method that checks for existence of an Oid object within a specified array. This is equivalent in functionality to gss_test_oid_set_member. The use of Java arrays and Java's automatic garbage collection has eliminated the need for the following routines: gss_create_empty_oid_set, gss_release_oid_set, and gss_add_oid_set_member. Java GSS-API implementations will not contain them. Java's automatic garbage collection and the immutable property of the Oid object eliminates the memory management issues of the C counterpart.
Whenever a default value for an Object Identifier Set is required, a "null" value can be used. Please consult the detailed method description for details.
GSS-API credentials are represented by the GSSCredential interface. The interface contains several constructs to allow for the creation of most common credential objects for the initiator and the acceptor. Comparisons are performed using the interface's "equals" method. The following general description of GSS-API credentials is included from the C-bindings specification:
GSS-API credentials can contain mechanism-specific principal authentication data for multiple mechanisms. A GSS-API credential is composed of a set of credential-elements, each of which is applicable to a single mechanism. A credential may contain at most one credential-element for each supported mechanism. A credential-element identifies the data needed by a single mechanism to authenticate a single principal, and conceptually contains two credential-references that describe the actual mechanism-specific authentication data, one to be used by GSS-API for initiating contexts, and one to be used for accepting
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contexts. For mechanisms that do not distinguish between acceptor and initiator credentials, both references would point to the same underlying mechanism-specific authentication data.
Credentials describe a set of mechanism-specific principals, and give their holder the ability to act as any of those principals. All principal identities asserted by a single GSS-API credential should belong to the same entity, although enforcement of this property is an implementation-specific matter. A single GSSCredential object represents all the credential elements that have been acquired.
The creation of an GSSContext object allows the value of "null" to be specified as the GSSCredential input parameter. This will indicate a desire by the application to act as a default principal. While individual GSS-API implementations are free to determine such default behavior as appropriate to the mechanism, the following default behavior by these routines is recommended for portability:
For the initiator side of the context:
1) If there is only a single principal capable of initiating security contexts for the chosen mechanism that the application is authorized to act on behalf of, then that principal shall be used; otherwise,
2) If the platform maintains a concept of a default network-identity for the chosen mechanism, and if the application is authorized to act on behalf of that identity for the purpose of initiating security contexts, then the principal corresponding to that identity shall be used; otherwise,
3) If the platform maintains a concept of a default local identity, and provides a means to map local identities into network- identities for the chosen mechanism, and if the application is authorized to act on behalf of the network-identity image of the default local identity for the purpose of initiating security contexts using the chosen mechanism, then the principal corresponding to that identity shall be used; otherwise,
4) A user-configurable default identity should be used.
For the acceptor side of the context:
1) If there is only a single authorized principal identity capable of accepting security contexts for the chosen mechanism, then that principal shall be used; otherwise,
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2) If the mechanism can determine the identity of the target principal by examining the context-establishment token processed during the accept method, and if the accepting application is authorized to act as that principal for the purpose of accepting security contexts using the chosen mechanism, then that principal identity shall be used; otherwise,
3) If the mechanism supports context acceptance by any principal, and if mutual authentication was not requested, any principal that the application is authorized to accept security contexts under using the chosen mechanism may be used; otherwise,
4) A user-configurable default identity shall be used.
The purpose of the above rules is to allow security contexts to be established by both initiator and acceptor using the default behavior whenever possible. Applications requesting default behavior are likely to be more portable across mechanisms and implementations than ones that instantiate an GSSCredential object representing a specific identity.
The GSSContext interface is used to represent one end of a GSS-API security context, storing state information appropriate to that end of the peer communication, including cryptographic state information. The instantiation of the context object is done differently by the initiator and the acceptor. After the context has been instantiated, the initiator may choose to set various context options that will determine the characteristics of the desired security context. When all the application-desired characteristics have been set, the initiator will call the initSecContext method, which will produce a token for consumption by the peer's acceptSecContext method. It is the responsibility of the application to deliver the authentication token(s) between the peer applications for processing. Upon completion of the context-establishment phase, context attributes can be retrieved, by both the initiator and acceptor, using the accessor methods. These will reflect the actual attributes of the established context. At this point, the context can be used by the application to apply cryptographic services to its data.
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
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the underlying mechanism at one end of a GSS-API security context for use by the peer mechanism at the other end. Encapsulation (if required) within the application protocol and transfer of the token are the responsibility of the peer applications.
Java GSS-API uses byte arrays to represent authentication tokens. Overloaded methods exist that allow the caller to supply input and output streams that will be used for the reading and writing of the token data.
Certain GSS-API routines are intended to transfer data between processes in multi-process programs. These routines use a caller- opaque octet-string, generated by the GSS-API in one process for use by the GSS-API in another process. The calling application is responsible for transferring such tokens between processes. Note that, while GSS-API implementors are encouraged to avoid placing sensitive information within inter-process tokens, or to cryptographically protect them, many implementations will be unable to avoid placing key material or other sensitive data within them. It is the application's responsibility to ensure that inter-process tokens are protected in transit, and transferred only to processes that are trustworthy. An inter-process token is represented using a byte array emitted from the export method of the GSSContext interface. The receiver of the inter-process token would initialize an GSSContext object with this token to create a new context. Once a context has been exported, the GSSContext object is invalidated and is no longer available.
RFC 2743 [GSSAPIv2-UPDATE] defined the usage of major and minor status values for the signaling of GSS-API errors. The major code, also called GSS status code, is used to signal errors at the GSS-API level, independent of the underlying mechanism(s). The minor status value or Mechanism status code, is a mechanism-defined error value indicating a mechanism-specific error code.
Java GSS-API uses exceptions implemented by the GSSException class to signal both minor and major error values. Both mechanism-specific errors and GSS-API level errors are signaled through instances of this class. The usage of exceptions replaces the need for major and minor codes to be used within the API calls. The GSSException class also contains methods to obtain textual representations for both the major and minor values, which is equivalent to the functionality of gss_display_status.
GSS status codes indicate errors that are independent of the underlying mechanism(s) used to provide the security service. The errors that can be indicated via a GSS status code are generic API routine errors (errors that are defined in the GSS-API specification). These bindings take advantage of the Java exceptions mechanism, thus, eliminating the need for calling errors.
A GSS status code indicates a single fatal generic API error from the routine that has thrown the GSSException. Using exceptions announces that a fatal error has occurred during the execution of the method. The GSS-API operational model also allows for the signaling of supplementary status information from the per-message calls. These need to be handled as return values since using exceptions is not appropriate for informatory or warning-like information. The methods that are capable of producing supplementary information are the two per-message methods GSSContext.verifyMIC() and GSSContext.unwrap(). These methods fill the supplementary status codes in the MessageProp object that was passed in.
A GSSException object, along with providing the functionality for setting 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_BINDINGS 1 Incorrect channel bindings were supplied.
BAD_MECH 2 An unsupported mechanism was requested.
BAD_NAME 3 An invalid name was supplied.
BAD_NAMETYPE 4 A supplied name was of an unsupported type.
BAD_STATUS 5 An invalid status code was supplied.
BAD_MIC 6 A token had an invalid MIC.
CONTEXT_EXPIRED 7 The context has expired.
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CREDENTIALS_EXPIRED 8 The referenced credentials have expired.
DEFECTIVE_CREDENTIAL 9 A supplied credential was invalid.
DEFECTIVE_TOKEN 10 A supplied token was invalid.
FAILURE 11 Miscellaneous failure, unspecified at the GSS-API level.
NO_CONTEXT 12 Invalid context has been supplied.
NO_CRED 13 No credentials were supplied, or the credentials were unavailable or inaccessible.
BAD_QOP 14 The quality-of-protection (QOP) requested could not be provided.
UNAUTHORIZED 15 The operation is forbidden by the local security policy.
UNAVAILABLE 16 The operation or option is unavailable.
DUPLICATE_ELEMENT 17 The requested credential element already exists.
NAME_NOT_MN 18 The provided name was not a mechanism name.
The following four status codes (DUPLICATE_TOKEN, OLD_TOKEN, UNSEQ_TOKEN, and GAP_TOKEN) are contained in a GSSException only if detected during context establishment, in which case it is a fatal error. (During per-message calls, these values are indicated as supplementary information contained in the MessageProp object.) They are:
DUPLICATE_TOKEN 19 The token was a duplicate of an earlier version.
OLD_TOKEN 20 The token's validity period has expired.
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UNSEQ_TOKEN 21 A later token has already been processed.
GAP_TOKEN 22 The expected token was not received.
The GSS major status code of FAILURE is used to indicate that the underlying mechanism detected an error for which no specific GSS status code is defined. The mechanism-specific status code can provide more details about the error.
The different major status codes that can be contained in the GSSException object thrown by the methods in this specification are the same as the major status codes returned by the corresponding calls in RFC 2743 [GSSAPIv2-UPDATE].
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.
Supplementary status codes are confined to the per-message methods of the GSSContext interface. Because of the informative nature of these errors it is not appropriate to use exceptions to signal them. Instead, the per-message operations of the GSSContext interface return these values in a MessageProp object.
The MessageProp class defines query methods that return boolean values indicating the following supplementary states:
Table: Supplementary Status Methods
Method Name Meaning when "true" is returned
isDuplicateToken The token was a duplicate of an earlier token.
isOldToken The token's validity period has expired.
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isUnseqToken A later token has already been processed.
isGapToken An expected per-message token was not received.
A "true" return value for any of the above methods indicates that the token exhibited the specified property. The application must determine the appropriate course of action for these supplementary values. They are not treated as errors by the GSS-API.
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
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communication with their users. The byte array name formats are assumed to be in non-printable formats (e.g., the byte array returned from the export method of the GSSName interface).
A GSSName object can be converted to a contiguous representation by using the toString method. This will guarantee that the name will be converted to a printable format. Different initialization methods in the GSSName interface are defined allowing support for multiple syntaxes for each supported namespace, and allowing users the freedom to choose a preferred name representation. The toString method should use an implementation-chosen printable syntax for each supported name type. To obtain the printable name type, getStringNameType method can be used.
There is no guarantee that calling the toString method on the GSSName interface will produce the same string form as the original imported string name. Furthermore, it is possible that the name was not even constructed from a string representation. The same applies to namespace identifiers, which may not necessarily survive unchanged after a journey through the internal name form. An example of this might be a mechanism that authenticates X.500 names, but provides an algorithmic mapping of Internet DNS names into X.500. That mechanism's implementation of GSSName might, when presented with a DNS name, generate an internal name that contained both the original DNS name and the equivalent X.500 name. Alternatively, it might only store the X.500 name. In the latter case, the toString method of GSSName would most likely generate a printable X.500 name, rather than the original DNS name.
The context acceptor can obtain a GSSName object representing the entity performing the context initiation (through the usage of getSrcName method). Since this name has been authenticated by a single mechanism, it contains only a single name (even if the internal name presented by the context initiator to the GSSContext object had multiple components). Such names are termed internal- mechanism names (or MNs), and the names emitted by GSSContext interface in the getSrcName and getTargName are always of this type. Since some applications may require MNs without wanting to incur the overhead of an authentication operation, creation methods are provided that take not only the name buffer and name type, but also the mechanism oid for which this name should be created. When dealing with an existing GSSName object, the canonicalize method may be invoked to convert a general internal name into an MN.
GSSName objects can be compared using their equal method, which returns "true" if the two names being compared refer to the same entity. This is the preferred way to perform name comparisons instead of using the printable names that a given GSS-API
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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 a GSSName object on each name and invoking the equal method on each name from the Access Control List (ACL) may be prohibitive. As an alternative way of supporting this case, GSS-API defines a special form of the contiguous byte array name, which may be compared directly (byte by byte). Contiguous names suitable for comparison are generated by the export method. Exported names may be re- imported by using the byte array constructor and specifying the NT_EXPORT_NAME as the name type object identifier. The resulting GSSName name will also be a MN.
The GSSName interface defines public static Oid objects representing the standard name types. Structurally, an exported name object consists of a header containing an OID identifying the mechanism that authenticated the name, and a trailer containing the name itself, where the syntax of the trailer is defined by the individual mechanism specification. Detailed description of the format is specified in the language-independent GSS-API specification [GSSAPIv2-UPDATE].
Note that the results obtained by using the equals method will in general be different from those obtained by invoking canonicalize and export, and then comparing the byte array output. The first series of operation determines whether two (unauthenticated) names identify the same principal; the second whether a particular mechanism would authenticate them as the same principal. These two operations will in general give the same results only for MNs.
It is important to note that the above are guidelines as to how GSSName implementations should behave, and are not intended to be specific requirements of how name objects must be implemented. The mechanism designers are free to decide on the details of their implementations of the GSSName interface as long as the behavior satisfies the above guidelines.
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
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context. Channel bindings are communicated to the GSS-API using the ChannelBinding object. The application may use byte arrays to specify the application data to be used in the channel binding as well as using instances of the InetAddress. The InetAddress for the initiator and/or acceptor can be used within an instance of a ChannelBinding. ChannelBinding can be set for the GSSContext object using the setChannelBinding method before the first call to init or accept has been performed. Unless the setChannelBinding method has been used to set the ChannelBinding for a GSSContext object, "null" ChannelBinding will be assumed. InetAddress is currently the only address type defined within the Java platform and as such, it is the only one supported within the ChannelBinding class. Applications that use other types of addresses can include them as part of the application-specific data.
Conceptually, the GSS-API concatenates the initiator and acceptor address information, and the application-supplied byte array to form an octet-string. The mechanism calculates a Message Integrity Code (MIC) over this octet-string and binds the MIC to the context establishment token emitted by the init method of the GSSContext interface. The same bindings are set by the context acceptor for its GSSContext object and during processing of the accept method, a MIC is calculated in the same way. The calculated MIC is compared with that found in the token, and if the MICs differ, accept will throw a GSSException with the major code set to BAD_BINDINGS, and the context will not be established. Some mechanisms may include the actual channel binding data in the token (rather than just a MIC); applications should therefore not use confidential data as channel- binding components.
Individual mechanisms may impose additional constraints on addresses that may appear in channel bindings. For example, a mechanism may verify that the initiator address field of the channel binding contains the correct network address of the host system. Portable applications should therefore ensure that they either provide correct information for the address fields, or omit the setting of the addressing information.
The context object provides overloaded methods that use input and output streams as the means to convey authentication and per-message GSS-API tokens. It is important to note that the streams are expected to contain the usual GSS-API tokens, which would otherwise be handled through the usage of byte arrays. The tokens are expected to have a definite start and an end. The callers are responsible for
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ensuring that the supplied streams will not block, or expect to block until a full token is processed by the GSS-API method. Only a single GSS-API token will be processed per invocation of the stream-based method.
The usage of streams allows the callers to have control and management of the supplied buffers. Because streams are non- primitive objects, the callers can make the streams as complicated or as simple as desired simply by using the streams defined in the java.io package or creating their own through the use of inheritance. This will allow for the application's greatest flexibility.
Whenever the application wishes to omit an optional parameter the "null" value shall be used. The detailed method descriptions indicate which parameters are optional. Method overloading has also been used as a technique to indicate default parameters.
This section presents a brief description of the classes and interfaces that constitute the GSS-API. The implementations of these are obtained from the CLASSPATH defined by the application. If Java GSS becomes part of the standard Java APIs, then these classes will be available by default on all systems as part of the JRE's system classes.
This section also shows the corresponding RFC 2743 [GSSAPIv2-UPDATE] functionality implemented by each of the classes. Detailed description of these classes and their methods is presented in section 7.
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 [GSSAPIv2- UPDATE] routines:
GSS-API names are represented in the Java bindings through the GSSName interface. Different name formats and their definitions are identified with Universal Object Identifiers (oids). The format of the names can be derived based on the unique oid of each name type. The following GSS-API routines are provided by the GSSName interface:
gss_display_name Covert internal name 7.2.7 representation to text format.
gss_compare_name Compare two internal names. 7.2.3, 7.2.4
gss_release_name Release resources associated N/A with the internal name.
gss_canonicalize_name Convert an internal name to a 7.2.5 mechanism name.
gss_export_name Convert a mechanism name to 7.2.6 export format.
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gss_duplicate_name Create a copy of the internal N/A name.
The gss_release_name call is not provided as Java does its own garbage collection. The gss_duplicate_name call is also redundant; the GSSName interface has no mutator methods that can change the state of the object so it is safe for sharing across threads.
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:
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:
gss_wrap_size_limit Determine token-size limit 7.4.13 for gss_wrap.
gss_export_sec_context Transfer security context 7.4.22 to another process.
gss_get_mic Calculate a cryptographic 7.4.18, Message Integrity Code (MIC) 7.4.19 for a message.
gss_verify_mic Verify integrity on a received 7.4.20, message. 7.4.21
gss_wrap Attach a MIC to a message and 7.4.14, optionally encrypt the message 7.4.15 content.
gss_unwrap Obtain a previously wrapped 7.4.16, application message verifying 7.4.17 its integrity and optionally decrypting it.
The functionality offered by the gss_process_context_token routine has not been included in the Java bindings specification. The corresponding functionality of gss_delete_sec_context has also been modified to not return any peer tokens. This has been proposed in accordance to the recommendations stated in RFC 2743 [GSSAPIv2- UPDATE]. GSSContext does offer the functionality of destroying the locally stored context information.
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
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this object and in other cases the GSS-API returns information to the application by setting it in this object. See the description of the per-message operations wrap, unwrap, getMIC, and verifyMIC in the GSSContext interfaces for details.
Exceptions are used in the Java bindings to signal fatal errors to the calling applications. This replaces the major and minor codes used in the C-bindings specification as a method of signaling failures. The GSSException class handles both minor and major codes, as well as their translation into textual representation. All GSS- API methods are declared as throwing this exception.
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:
An instance of this class is used to specify channel binding information to the GSSContext object before the start of a security context establishment. The application may use a byte array to specify application data to be used in the channel binding as well as to use instances of the InetAddress. InetAddress is currently the only address type defined within the Java platform and as such, it is the only one supported within the ChannelBinding class. Applications that use other types of addresses can include them as part of the application data.
The GSSManager class is an abstract class that serves as a factory for three GSS interfaces: GSSName, GSSCredential, and GSSContext. It also provides methods for applications to determine what mechanisms are available from the GSS implementation and what name types these mechanisms support. An instance of the default GSSManager subclass may be obtained through the static method getInstance(), but applications are free to instantiate other subclasses of GSSManager.
All but one method in this class are declared abstract. This means that subclasses have to provide the complete implementation for those methods. The only exception to this is the static method getInstance(), which will have platform-specific code to return an instance of the default subclass.
Platform providers of GSS are required not to add any constructors to this class, private, public, or protected. This will ensure that all subclasses invoke only the default constructor provided to the base class by the compiler.
A subclass extending the GSSManager abstract class may be implemented as a modular provider-based layer that utilizes some well-known service provider specification. The GSSManager API provides the application with methods to set provider preferences on such an implementation. These methods also allow the implementation to throw a well-defined exception in case provider-based configuration is not supported. Applications that expect to be portable should be aware of this and recover cleanly by catching the exception.
It is envisioned that there will be three most common ways in which providers will be used:
1) The application does not care about what provider is used (the default case).
2) The application wants a particular provider to be used preferentially, either for a particular mechanism or all the time, irrespective of the mechanism.
3) The application wants to use the locally configured providers as far as possible, but if support is missing for one or more mechanisms, then it wants to fall back on its own provider.
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The GSSManager class has two methods that enable these modes of usage: addProviderAtFront() and addProviderAtEnd(). These methods have the effect of creating an ordered list of <provider, oid> pairs where each pair indicates a preference of provider for a given oid.
The use of these methods does not require any knowledge of whatever service provider specification the GSSManager subclass follows. It is hoped that these methods will serve the needs of most applications. Additional methods may be added to an extended GSSManager that could be part of a service provider specification that is standardized later.
Returns an array of Oid objects indicating the 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).
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.
public abstract GSSName createName(String nameStr, Oid nameType) throws GSSException
Factory method to convert a contiguous string name from the specified namespace to a GSSName object. In general, the GSSName object created will not be an MN; two examples that are exceptions to this are when the namespace type parameter indicates NT_EXPORT_NAME or when the GSS-API implementation is not multi-mechanism.
Parameters:
nameStr: The string representing a printable form of the name to create.
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nameType: The Oid specifying the namespace of the printable name is supplied. Note that nameType serves to describe and qualify the interpretation of the input nameStr, it does not necessarily imply a type for the output GSSName implementation. The "null" value can be used to specify that a mechanism-specific default printable syntax should be assumed by each mechanism that examines nameStr.
public abstract GSSName createName(byte[] name, Oid nameType) throws GSSException
Factory method to convert a contiguous byte array containing a name from the specified namespace to a GSSName object. In general, the GSSName object created will not be an MN; two examples that are exceptions to this are when the namespace type parameter indicates NT_EXPORT_NAME or when the GSS-API implementation is not multi- mechanism.
Parameters:
name: The byte array containing the name to create.
nameType: The Oid specifying the namespace of the name supplied in the byte array. Note that nameType serves to describe and qualify the interpretation of the input name byte array; it does not necessarily imply a type for the output GSSName implementation. The "null" value can be used to specify that a mechanism-specific default syntax should be assumed by each mechanism that examines the byte array.
public abstract GSSName createName(String nameStr, Oid nameType, Oid mech) throws GSSException
Factory method to convert a contiguous string name from the specified namespace to a GSSName object that is a mechanism name (MN). In other words, this method is a utility that does the equivalent of two steps: the createName described in section 7.1.6, and then also the GSSName.canonicalize() described in section 7.2.5.
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Parameters:
nameStr: The string representing a printable form of the name to create.
nameType: The Oid specifying the namespace of the printable name supplied. Note that nameType serves to describe and qualify the interpretation of the input nameStr; it does not necessarily imply a type for the output GSSName implementation. The "null" value can be used to specify that a mechanism-specific default printable syntax should be assumed when the mechanism examines nameStr.
mech: Oid specifying the mechanism for which this name should be created.
public abstract GSSName createName(byte[] name, Oid nameType, Oid mech) throws GSSException
Factory method to convert a contiguous byte array containing a name from the specified namespace to a GSSName object that is an MN. In other words, this method is a utility that does the equivalent of two steps: the createName described in section 7.1.7, and then also the GSSName.canonicalize() described in section 7.2.5.
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. The "null" value can be used to specify that a mechanism-specific default syntax should be assumed by each mechanism that examines the byte array.
mech: Oid specifying the mechanism for which this name should be created.
public abstract GSSCredential createCredential(int usage) throws GSSException
Factory method for acquiring default credentials. This will cause the GSS-API to use system-specific defaults for the set of mechanisms, name, and a DEFAULT lifetime.
Parameters:
usage: The intended usage for this credential object. The value of this parameter must be one of:
GSSCredential.INITIATE_AND_ACCEPT(0), GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2)
public abstract GSSCredential createCredential(GSSName aName, int lifetime, Oid mech, int usage) throws GSSException
Factory method for acquiring a single mechanism credential.
Parameters:
aName: Name of the principal for whom this credential is to be acquired. Use "null" to specify the default principal.
lifetime: The number of seconds that credentials should remain valid. Use GSSCredential.INDEFINITE_LIFETIME to request that the credentials have the maximum permitted lifetime. Use GSSCredential.DEFAULT_LIFETIME to request default credential lifetime.
mech: The oid of the desired mechanism. Use "(Oid) null" to request the default mechanism(s).
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usage: The intended usage for this credential object. The value of this parameter must be one of:
GSSCredential.INITIATE_AND_ACCEPT(0), GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2)
public abstract GSSCredential createCredential(GSSName aName, int lifetime, Oid[] mechs, int usage) throws GSSException
Factory method for acquiring credentials over a set of mechanisms. Acquires credentials for each of the mechanisms specified in the array called mechs. To determine the list of mechanisms' for which the acquisition of credentials succeeded, the caller should use the GSSCredential.getMechs() method.
Parameters:
aName: Name of the principal for whom this credential is to be acquired. Use "null" to specify the default principal.
lifetime: The number of seconds that credentials should remain valid. Use GSSCredential.INDEFINITE_LIFETIME to request that the credentials have the maximum permitted lifetime. Use GSSCredential.DEFAULT_LIFETIME to request default credential lifetime.
mechs: The array of mechanisms over which the credential is to be acquired. Use "(Oid[]) null" for requesting a system-specific default set of mechanisms.
usage: The intended usage for this credential object. The value of this parameter must be one of:
GSSCredential.INITIATE_AND_ACCEPT(0), GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2)
public abstract GSSContext createContext(GSSName peer, Oid mech, GSSCredential myCred, int lifetime) throws GSSException
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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().
Parameters:
peer: Name of the target peer.
mech: Oid of the desired mechanism. Use "(Oid) null" to request the default mechanism.
myCred: Credentials of the initiator. Use "null" to act as a default initiator principal.
lifetime: The request lifetime, in seconds, for the context. Use GSSContext.INDEFINITE_LIFETIME and GSSContext.DEFAULT_LIFETIME to request indefinite or default context lifetime.
public abstract GSSContext createContext(GSSCredential myCred) throws GSSException
Factory method for creating a context on the acceptor' side. The context's properties will be determined from the input token supplied to the accept method.
Parameters:
myCred: Credentials for the acceptor. Use "null" to act as a default acceptor principal.
public abstract GSSContext createContext(byte[] interProcessToken) throws GSSException
Factory method for creating a previously exported context. The context properties will be determined from the input token and can't be modified through the set methods.
Parameters:
interProcessToken: The token previously emitted from the export method.
public abstract void addProviderAtFront(Provider p, Oid mech) throws GSSException
This method is used to indicate to the GSSManager that the application would like a particular provider to be used ahead of all others when support is desired for the given mechanism. When a value of "null" is used instead of an Oid for the mechanism, the GSSManager must use the indicated provider ahead of all others no matter what the mechanism is. Only when the indicated provider does not support the needed mechanism should the GSSManager move on to a different provider.
Calling this method repeatedly preserves the older settings but lowers them in preference thus forming an ordered list of provider and Oid pairs that grows at the top.
Calling addProviderAtFront with a null Oid will remove all previous preferences that were set for this provider in the GSSManager instance. Calling addProviderAtFront with a non-null Oid will remove any previous preference that was set using this mechanism and this provider together.
If the GSSManager implementation does not support an SPI with a pluggable provider architecture, it should throw a GSSException with the status code GSSException.UNAVAILABLE to indicate that the operation is unavailable.
Parameters:
p: The provider instance that should be used whenever support is needed for mech.
mech: The mechanism for which the provider is being set.
Suppose an application desired that the provider A always be checked first when any mechanism is needed, it would call:
GSSManager mgr = GSSManager.getInstance(); // mgr may at this point have its own pre-configured list // of provider preferences. The following will prepend to // any such list:
mgr.addProviderAtFront(A, null);
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Now if it also desired that the mechanism of Oid m1 always be obtained from the provider B before the previously set A was checked, it would call:
mgr.addProviderAtFront(B, m1);
The GSSManager would then first check with B if m1 was needed. In case B did not provide support for m1, the GSSManager would continue on to check with A. If any mechanism m2 is needed where m2 is different from m1, then the GSSManager would skip B and check with A directly.
Suppose, at a later time, the following call is made to the same GSSManager instance:
mgr.addProviderAtFront(B, null)
then the previous setting with the pair (B, m1) is subsumed by this and should be removed. Effectively, the list of preferences now becomes {(B, null), (A, null), ... //followed by the pre-configured list.
Please note, however, that the following call:
mgr.addProviderAtFront(A, m3)
does not subsume the previous setting of (A, null), and the list will effectively become {(A, m3), (B, null), (A, null), ...}
public abstract void addProviderAtEnd(Provider p, Oid mech) throws GSSException
This method is used to indicate to the GSSManager that the application would like a particular provider to be used if no other provider can be found that supports the given mechanism. When a value of "null" is used instead of an Oid for the mechanism, the GSSManager must use the indicated provider for any mechanism.
Calling this method repeatedly preserves the older settings, but raises them above newer ones in preference thus forming an ordered list of providers and Oid pairs that grows at the bottom. Thus, the older provider settings will be utilized first before this one is.
If there are any previously existing preferences that conflict with the preference being set here, then the GSSManager should ignore this request.
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If the GSSManager implementation does not support an SPI with a pluggable provider architecture, it should throw a GSSException with the status code GSSException.UNAVAILABLE to indicate that the operation is unavailable.
Parameters:
p: The provider instance that should be used whenever support is needed for mech.
mech: The mechanism for which the provider is being set.
Suppose an application desired that when a mechanism of Oid m1 is needed, the system default providers always be checked first, and only when they do not support m1 should a provider A be checked. It would then make the call:
GSSManager mgr = GSSManager.getInstance();
mgr.addProviderAtEnd(A, m1);
Now, if it also desired that for all mechanisms the provider B be checked after all configured providers have been checked, it would then call:
mgr.addProviderAtEnd(B, null);
Effectively, the list of preferences now becomes {..., (A, m1), (B, null)}.
Suppose, at a later time, the following call is made to the same GSSManager instance:
mgr.addProviderAtEnd(B, m2)
then the previous setting with the pair (B, null) subsumes this; therefore, this request should be ignored. The same would happen if a request is made for the already existing pairs of (A, m1) or (B, null).
Please note, however, that the following call:
mgr.addProviderAtEnd(A, null)
is not subsumed by the previous setting of (A, m1) and the list will effectively become {..., (A, m1), (B, null), (A, null)}.
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.
Included below are code examples utilizing the GSSName interface. The code below creates a GSSName, converts it to a mechanism name (MN), performs a comparison, obtains a printable representation of the name, exports it and then re-imports to obtain a new GSSName.
GSSManager mgr = GSSManager.getInstance();
// create a host-based service name GSSName name = mgr.createName("service@host", GSSName.NT_HOSTBASED_SERVICE);
Oid krb5 = new Oid("1.2.840.113554.1.2.2");
GSSName mechName = name.canonicalize(krb5);
// the above two steps are equivalent to the following GSSName mechName = mgr.createName("service@host", GSSName.NT_HOSTBASED_SERVICE, krb5);
// perform name comparison if (name.equals(mechName)) print("Names are equals.");
// obtain textual representation of name and its printable // name type print(mechName.toString() + mechName.getStringNameType().toString());
// export and re-import the name byte[] exportName = mechName.export();
// create a new name object from the exported buffer GSSName newName = mgr.createName(exportName, GSSName.NT_EXPORT_NAME);
Oid indicating a host-based service name form. It is used to represent services associated with host computers. This name form is constructed using two elements, "service" and "hostname", as follows:
service@hostname
Values for the "service" element are registered with the IANA. It represents the following value: { iso(1) member-body(2) Unites States(840) mit(113554) infosys(1) gssapi(2) generic(1) service_name(4) }
public static final Oid NT_USER_NAME
Name type to indicate a named user on a local system. It represents the following value: { iso(1) member-body(2) United States(840) mit(113554) infosys(1) gssapi(2) generic(1) user_name(1) }
public static final Oid NT_MACHINE_UID_NAME
Name type to indicate a numeric user identifier corresponding to a user on a local system (e.g., Uid). It represents the following value: { iso(1) member-body(2) United States(840) mit(113554) infosys(1) gssapi(2) generic(1) machine_uid_name(2) }
public static final Oid NT_STRING_UID_NAME
Name type to indicate a string of digits representing the numeric user identifier of a user on a local system. It represents the following value: { iso(1) member-body(2) United States(840) mit(113554) infosys(1) gssapi(2) generic(1) string_uid_name(3) }
public static final Oid NT_ANONYMOUS
Name type for representing an anonymous entity. It represents the following value: { iso(1), org(3), dod(6), internet(1), security(5), nametypes(6), gss-anonymous-name(3) }
public static final Oid NT_EXPORT_NAME
Name type used to indicate an exported name produced by the export method. It represents the following value: { iso(1), org(3), dod(6), internet(1), security(5), nametypes(6), gss-api-exported-name(4) }
public boolean equals(GSSName another) throws GSSException
Compares two GSSName objects to determine whether they refer to the same entity. This method may throw a GSSException when the names cannot be compared. If either of the names represents an anonymous entity, the method will return "false".
A variation of the equals method, described in section 7.2.3, that is provided to override the Object.equals() method that the implementing class will inherit. The behavior is exactly the same as that in section 7.2.3 except that no GSSException is thrown; instead, "false" will be returned in the situation where an error occurs. (Note that the Java language specification requires that two objects that are equal according to the equals(Object) method must return the same integer result when the hashCode() method is called on them.)
public GSSName canonicalize(Oid mech) throws GSSException
Creates a mechanism name (MN) from an arbitrary internal name. This is equivalent to using the factory methods described in sections 7.1.8 or 7.1.9 that take the mechanism name as one of their parameters.
Parameters:
mech: The oid for the mechanism for which the canonical form of the name is requested.
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 [GSSAPIv2-UPDATE].
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.
public Oid getStringNameType() throws GSSException
Returns the oid representing the type of name returned through the toString method. Using this oid, the syntax of the printable name can be determined.
Tests if this name object contains only one mechanism element and is thus a mechanism name as defined by RFC 2743 [GSSAPIv2-UPDATE].
7.3. public interface GSSCredential implements Cloneable
This interface encapsulates the GSS-API credentials for an entity. A credential contains all the necessary cryptographic information to enable the creation of a context on behalf of the entity that it
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represents. It may contain multiple, distinct, mechanism-specific credential elements, each containing information for a specific security mechanism, but all referring to the same entity.
A credential may be used to perform context initiation, acceptance, or both.
GSS-API implementations must impose a local access-control policy on callers to prevent unauthorized callers from acquiring credentials to which they are not entitled. GSS-API credential creation is not intended to provide a "login to the network" function, as such a function would involve the creation of new credentials rather than merely acquiring a handle to existing credentials. Such functions, if required, should be defined in implementation-specific extensions to the API.
If credential acquisition is time-consuming for a mechanism, the mechanism may choose to delay the actual acquisition until the credential is required (e.g., by GSSContext). Such mechanism- specific implementation decisions should be invisible to the calling application; thus, the query methods immediately following the creation of a credential object must return valid credential data, and may therefore incur the overhead of a deferred credential acquisition.
Applications will create a credential object passing the desired parameters. The application can then use the query methods to obtain specific information about the instantiated credential object (equivalent to the gss_inquire routines). When the credential is no longer needed, the application should call the dispose (equivalent to gss_release_cred) method to release any resources held by the credential object and to destroy any cryptographically sensitive information.
Classes implementing this interface also implement the Cloneable interface. This indicates 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.
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", GSSName.NT_USER_NAME);
// now acquire credentials for the entity GSSCredential cred = mgr.createCredential(name, GSSCredential.ACCEPT_ONLY);
// display credential information - name, remaining lifetime, // and the mechanisms it has been acquired over print(cred.getName().toString()); print(cred.getRemainingLifetime());
Oid[] mechs = cred.getMechs(); if (mechs != null) { for (int i = 0; i < mechs.length; i++) print(mechs[i].toString()); } // release system resources held by the credential cred.dispose();
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.
public int getRemainingLifetime() throws GSSException
Returns the remaining lifetime in seconds for a credential. The remaining lifetime is the minimum lifetime for any of the underlying credential mechanisms. A return value of GSSCredential.INDEFINITE_LIFETIME indicates that the credential does not expire. A return value of 0 indicates that the credential is already expired.
public int getRemainingInitLifetime(Oid mech) throws GSSException
Returns the remaining lifetime in seconds for the credential to remain capable of initiating security contexts under the specified mechanism. A return value of GSSCredential.INDEFINITE_LIFETIME indicates that the credential does not expire for context initiation. A return value of 0 indicates that the credential is already expired.
Parameters:
mechOID: The mechanism for which information should be returned.
public int getRemainingAcceptLifetime(Oid mech) throws GSSException
Returns the remaining lifetime in seconds for the credential to remain capable of accepting security contexts under the specified mechanism. A return value of GSSCredential.INDEFINITE_LIFETIME indicates that the credential does not expire for context acceptance. A return value of 0 indicates that the credential is already expired.
Parameters:
mechOID: The mechanism for which information should be returned.
Returns the credential usage flag as a union over all mechanisms. The return value will be one of GSSCredential.INITIATE_AND_ACCEPT(0), GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2).
public int getUsage(Oid mechOID) throws GSSException
Returns the credential usage flag for the specified mechanism only. The return value will be one of GSSCredential.INITIATE_AND_ACCEPT(0), GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2).
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Parameters:
mechOID: The mechanism for which information should be returned.
public void add(GSSName aName, int initLifetime, int acceptLifetime, Oid mech, int usage) throws GSSException
Adds a mechanism-specific credential-element to an existing credential. This method allows the construction of credentials one mechanism at a time.
This routine is envisioned to be used mainly by context acceptors during the creation of acceptance credentials, which are to be used with a variety of clients using different security mechanisms.
This routine adds the new credential element "in-place". To add the element in a new credential, first call clone() to obtain a copy of this credential, then call its add() method.
Parameters:
aName: Name of the principal for whom this credential is to be acquired. Use "null" to specify the default principal.
initLifetime: The number of seconds that credentials should remain valid for initiating of security contexts. Use GSSCredential.INDEFINITE_LIFETIME to request that the credentials have the maximum permitted lifetime. Use GSSCredential.DEFAULT_LIFETIME to request default credential lifetime.
acceptLifetime: The number of seconds that credentials should remain valid for accepting of security contexts.
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Use GSSCredential.INDEFINITE_LIFETIME to request that the credentials have the maximum permitted lifetime. Use GSSCredential.DEFAULT_LIFETIME to request default credential lifetime.
mech: The mechanisms over which the credential is to be acquired.
usage: The intended usage for this credential object. The value of this parameter must be one of:
GSSCredential.INITIATE_AND_ACCEPT(0), GSSCredential.INITIATE_ONLY(1), or GSSCredential.ACCEPT_ONLY(2)
Tests if this GSSCredential refers to the same entity as the supplied object. The two credentials must be acquired over the same mechanisms and must refer to the same principal. Returns "true" if the two GSSCredentials refer to the same entity; "false" otherwise. (Note that the Java language specification [JLS] requires that two objects that are equal according to the equals(Object) method must return the same integer result when the hashCode() method is called on them.)
Parameters:
another: Another GSSCredential object for comparison.
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.
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Before the context establishment phase is initiated, the context initiator may request specific characteristics desired of the established context. These can be set using the set methods. After the context is established, the caller can check the actual characteristic and services offered by the context using the query methods.
The context establishment phase begins with the first call to the init method by the context initiator. During this phase, the initSecContext and acceptSecContext methods will produce GSS-API authentication tokens, which the calling application needs to send to its peer. If an error occurs at any point, an exception will get thrown and the code will start executing in a catch block. If not, the normal flow of code continues and the application can make a call to the isEstablished() method. If this method returns "false" it indicates that a token is needed from its peer in order to continue the context establishment phase. A return value of "true" signals that the local end of the context is established. This may still require that a token be sent to the peer, if one is produced by GSS- API. During the context establishment phase, the isProtReady() method may be called to determine if the context can be used for the per-message operations. This allows applications to use per-message operations on contexts that aren't fully established.
After the context has been established or the isProtReady() method returns "true", the query routines can be invoked to determine the actual characteristics and services of the established context. The application can also start using the per-message methods of wrap and getMIC to obtain cryptographic operations on application supplied data.
When the context is no longer needed, the application should call dispose to release any system resources the context may be using.
The example code presented below demonstrates the usage of the GSSContext interface for the initiating peer. Different operations on the GSSContext object are presented, including: object instantiation, setting of desired flags, context establishment, query of actual context flags, per-message operations on application data, and finally context deletion.
GSSManager mgr = GSSManager.getInstance();
// start by creating the name for a service entity GSSName targetName = mgr.createName("service@host", GSSName.NT_HOSTBASED_SERVICE);
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// create a context using default credentials for the above entity // and the implementation-specific default mechanism GSSContext context = mgr.createContext(targetName, null, /* default mechanism */ null, /* default credentials */ GSSContext.INDEFINITE_LIFETIME);
// set desired context options - all others are "false" by default context.requestConf(true); context.requestMutualAuth(true); context.requestReplayDet(true); context.requestSequenceDet(true);
// establish a context between peers - using byte arrays byte[]inTok = new byte[0];
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();
public byte[] initSecContext(byte[] inputBuf, int offset, int len) throws GSSException
Called by the context initiator to start the context creation process. This is equivalent to the stream-based method except that the token buffers are handled as byte arrays instead of using stream objects. This method may return an output token that the application will need to send to the peer for processing by the accept call. Typically, the application would do so by calling the flush() method on an OutputStream that encapsulates the connection between the two peers. The application can call isEstablished() to determine if the context establishment phase is complete for this peer. A return value of "false" from isEstablished() indicates that more tokens are expected to be supplied to the initSecContext() method. Note that it is possible that the initSecContext() method will return a token for
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the peer and isEstablished() will return "true" also. This indicates that the token needs to be sent to the peer, but the local end of the context is now fully established.
Upon completion of the context establishment, the available context options may be queried through the get methods.
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).
public int initSecContext(InputStream inStream, OutputStream outStream) throws GSSException
Called by the context initiator to start the context creation process. This is equivalent to the byte-array-based method. This method may write an output token to the outStream, which the application will need to send to the peer for processing by the accept call. Typically, the application would do so by calling the flush() method on an OutputStream that encapsulates the connection between the two peers. The application can call isEstablished() to determine if the context establishment phase is complete for this peer. A return value of "false" from isEstablished indicates that more tokens are expected to be supplied to the initSecContext method. Note that it is possible that the initSecContext() method will return a token for the peer and isEstablished() will return "true" also. This indicates that the token needs to be sent to the peer, but the local end of the context is now fully established.
The GSS-API authentication tokens contain a definitive start and end. This method will attempt to read one of these tokens per invocation, and may block on the stream if only part of the token is available.
Upon completion of the context establishment, the available context options may be queried through the get methods.
Parameters:
inStream: Contains the token generated by the peer. This parameter is ignored on the first call.
outStream: Output stream where the output token will be written. During the final stage of context establishment, there may be no bytes written.
This sample code merely demonstrates the token exchange during the context establishment phase. It is expected that most Java applications will use custom implementations of the Input and Output streams that encapsulate the communication routines. For instance, a simple read on the application InputStream, when called by the Context, might cause a token to be read from the peer, and a simple flush() on the application OutputStream might cause a previously written token to be transmitted to the peer.
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// Create a new GSSContext implementation object. // GSSContext wrapper implements interface GSSContext. GSSContext context = mgr.createContext(...); // use standard java.io stream objects ByteArrayOutputStream os = new ByteArrayOutputStream(); ByteArrayInputStream is = null;
try { do { context.initSecContext(is, os);
// send token if present if (os.size() > 0) sendToken(os);
// check if we should expect more tokens if (context.isEstablished()) break;
// another token expected from peer is = recvToken();
public byte[] acceptSecContext(byte[] inTok, int offset, int len) throws GSSException
Called by the context acceptor upon receiving a token from the peer. This call is equivalent to the stream-based method except that the token buffers are handled as byte arrays instead of using stream objects.
This method may return an output token that the application will need to send to the peer for further processing by the init call.
The "null" return value indicates that no token needs to be sent to the peer. The application can call isEstablished() to determine if the context establishment phase is complete for this peer. A return value of "false" from isEstablished() indicates that more tokens are expected to be supplied to this method.
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Note that it is possible that acceptSecContext() will return a token for the peer and isEstablished() will return "true" also. This indicates that the token needs to be sent to the peer, but the local end of the context is now fully established.
Upon completion of the context establishment, the available context options may be queried through the get methods.
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).
public void acceptSecContext(InputStream inStream, OutputStream outStream) throws GSSException
Called by the context acceptor upon receiving a token from the peer. This call is equivalent to the byte array method. It may write an output token to the outStream, which the application will need to send to the peer for processing by its initSecContext method. Typically, the application would do so by calling the flush() method on an OutputStream that encapsulates the connection between the two peers. The application can call isEstablished() to determine if the context establishment phase is complete for this peer. A return value of "false" from isEstablished() indicates that more tokens are expected to be supplied to this method.
Note that it is possible that acceptSecContext() will return a token for the peer and isEstablished() will return "true" also. This indicates that the token needs to be sent to the peer, but the local end of the context is now fully established.
The GSS-API authentication tokens contain a definitive start and end. This method will attempt to read one of these tokens per invocation, and may block on the stream if only part of the token is available.
Upon completion of the context establishment, the available context options may be queried through the get methods.
Parameters:
inStream: Contains the token generated by the peer.
outStream: Output stream where the output token will be written. During the final stage of context establishment, there may be no bytes written.
This sample code merely demonstrates the token exchange during the context establishment phase. It is expected that most Java applications will use custom implementations of the Input and Output streams that encapsulate the communication routines. For instance, a simple read on the application InputStream, when called by the Context, might cause a token to be read from the peer, and a simple flush() on the application OutputStream might cause a previously written token to be transmitted to the peer.
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// acquire server credentials GSSCredential server = mgr.createCredential(...);
// create acceptor GSS-API context from the default provider GSSContext context = mgr.createContext(server, null);
// use standard java.io stream objects ByteArrayOutputStream os = new ByteArrayOutputStream(); ByteArrayInputStream is = null;
try { do {
is = recvToken();
context.acceptSecContext(is, os);
// possibly send token to peer if (os.size() > 0) sendToken(os);
// check if local context establishment is complete if (context.isEstablished()) break; } while (true);
Used during context establishment to determine the state of the context. Returns "true" if this is a fully established context on the caller's side and no more tokens are needed from the peer. Should be called after a call to initSecContext() or acceptSecContext() when no GSSException is thrown.
public int getWrapSizeLimit(int qop, boolean confReq, int maxTokenSize) throws GSSException
Returns the maximum message size that, if presented to the wrap method with the same confReq and qop parameters, will result in an output token containing no more than the maxTokenSize bytes.
This call is intended for use by applications that communicate over protocols that impose a maximum message size. It enables the application to fragment messages prior to applying protection.
GSS-API implementations are recommended but not required to detect invalid QOP values when getWrapSizeLimit is called. This routine guarantees only a maximum message size, not the availability of specific QOP values for message protection.
Successful completion of this call does not guarantee that wrap will be able to protect a message of the computed length, since this ability may depend on the availability of system resources at the time that wrap is called. However, if the implementation itself imposes an upper limit on the length of messages that may be processed by wrap, the implementation should not return a value that is greater than this length.
Parameters:
qop: Indicates the level of protection wrap will be asked to provide.
confReq: Indicates if wrap will be asked to provide privacy service.
maxTokenSize: The desired maximum size of the token emitted by wrap.
public byte[] wrap(byte[] inBuf, int offset, int len, MessageProp msgProp) throws GSSException
Applies per-message security services over the established security context. The method will return a token with a cryptographic MIC and may optionally encrypt the specified inBuf. This method is equivalent in functionality to its stream counterpart. The returned byte array will contain both the MIC and the message.
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The MessageProp object is instantiated by the application and used to specify a QOP value that selects cryptographic algorithms, and a privacy service to optionally encrypt the message. The underlying mechanism that is used in the call may not be able to provide the privacy service. It sets the actual privacy service that it does provide in this MessageProp object, which the caller should then query upon return. If the mechanism is not able to provide the requested QOP, it throws a GSSException with the BAD_QOP code.
Since some application-level protocols may wish to use tokens emitted by wrap to provide "secure framing", implementations should support the wrapping of zero-length messages.
The application will be responsible for sending the token to the peer.
Parameters:
inBuf: Application data to be protected.
offset: The offset within the inBuf where the data begins.
len: The length of the data within the inBuf (starting at the offset).
msgProp: Instance of MessageProp that is used by the application to set the desired QOP and privacy state. Set the desired QOP to 0 to request the default QOP. Upon return from this method, this object will contain the actual privacy state that was applied to the message by the underlying mechanism.
public void wrap(InputStream inStream, OutputStream outStream, MessageProp msgProp) throws GSSException
Allows to apply per-message security services over the established security context. The method will produce a token with a cryptographic MIC and may optionally encrypt the message in inStream. The outStream will contain both the MIC and the message.
The MessageProp object is instantiated by the application and used to specify a QOP value that selects cryptographic algorithms, and a privacy service to optionally encrypt the message. The underlying mechanism that is used in the call may not be able to provide the privacy service. It sets the actual privacy service that it does
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provide in this MessageProp object, which the caller should then query upon return. If the mechanism is not able to provide the requested QOP, it throws a GSSException with the BAD_QOP code.
Since some application-level protocols may wish to use tokens emitted by wrap to provide "secure framing", implementations should support the wrapping of zero-length messages.
The application will be responsible for sending the token to the peer.
Parameters:
inStream: Input stream containing the application data to be protected.
outStream: The output stream to which to write the protected message. 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 actual privacy state that was applied to the message by the underlying mechanism.
public byte[] unwrap(byte[] inBuf, int offset, int len, MessageProp msgProp) throws GSSException
Used by the peer application to process tokens generated with the wrap call. This call is equal in functionality to its stream counterpart. The method will return the message supplied in the peer application to the wrap call, verifying the embedded MIC.
The MessageProp object is instantiated by the application and is used by the underlying mechanism to return information to the caller such as the QOP, whether confidentiality was applied to the message, and other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted by wrap to provide "secure framing", implementations should support the wrapping and unwrapping of zero-length messages.
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Parameters:
inBuf: GSS-API wrap token received from peer.
offset: The offset within the inBuf where the token begins.
len: The length of the token within the inBuf (starting at the offset).
msgProp: Upon return from the method, this object will contain the applied QOP, the privacy state of the message, and supplementary information, described in section 5.12.3, stating whether the token was a duplicate, old, out of sequence, or arriving after a gap.
public void unwrap(InputStream inStream, OutputStream outStream, MessageProp msgProp) throws GSSException
Used by the peer application to process tokens generated with the wrap call. This call is equal in functionality to its byte array counterpart. It will produce the message supplied in the peer application to the wrap call, verifying the embedded MIC.
The MessageProp object is instantiated by the application and is used by the underlying mechanism to return information to the caller such as the QOP, whether confidentiality was applied to the message, and other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted by wrap to provide "secure framing", implementations should support the wrapping and unwrapping of zero-length messages.
Parameters:
inStream: Input stream containing the GSS-API wrap token received from the peer.
outStream: The output stream to which to write the application message.
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msgProp: Upon return from the method, this object will contain the applied QOP, the privacy state of the message, and supplementary information, described in section 5.12.3, stating whether the token was a duplicate, old, out of sequence, or arriving after a gap.
public byte[] getMIC(byte[] inMsg, int offset, int len, MessageProp msgProp) throws GSSException
Returns a token containing a cryptographic MIC for the supplied message for transfer to the peer application. Unlike wrap, which encapsulates the user message in the returned token, only the message MIC is returned in the output token. This method is identical in functionality to its stream counterpart.
Note that privacy can only be applied through the wrap call.
Since some application-level protocols may wish to use tokens emitted by getMIC to provide "secure framing", implementations should support derivation of MICs from zero-length messages.
Parameters:
inMsg: Message over which to generate MIC.
offset: The offset within the inMsg where the token begins.
len: The length of the token within the inMsg (starting at the offset).
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.
public void getMIC(InputStream inStream, OutputStream outStream, MessageProp msgProp) throws GSSException
Produces a token containing a cryptographic MIC for the supplied message, for transfer to the peer application. Unlike wrap, which encapsulates the user message in the returned token, only the message MIC is produced in the output token. This method is identical in functionality to its byte array counterpart.
Note that privacy can only be applied through the wrap call.
Since some application-level protocols may wish to use tokens emitted by getMIC to provide "secure framing", implementations should support derivation of MICs from zero-length messages.
Parameters:
inStream: Input stream containing the message over which to generate MIC.
outStream: Output stream to which to write the GSS-API output token.
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.
public void verifyMIC(byte[] inTok, int tokOffset, int tokLen, byte[] inMsg, int msgOffset, int msgLen, MessageProp msgProp) throws GSSException
Verifies the cryptographic MIC, contained in the token parameter, over the supplied message. This method is equivalent in functionality to its stream counterpart.
The MessageProp object is instantiated by the application and is used by the underlying mechanism to return information to the caller such as the QOP indicating the strength of protection that was applied to the message and other supplementary message state information.
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Since some application-level protocols may wish to use tokens emitted by getMIC to provide "secure framing", implementations should support the calculation and verification of MICs over zero-length messages.
Parameters:
inTok: Token generated by peer's getMIC method.
tokOffset: The offset within the inTok where the token begins.
tokLen: The length of the token within the inTok (starting at the offset).
inMsg: Application message over which to verify the cryptographic MIC.
msgOffset: The offset within the inMsg where the message begins.
msgLen: The length of the message within the inMsg (starting at the offset).
msgProp: Upon return from the method, this object will contain the applied QOP and supplementary information, described in section 5.12.3, stating whether the token was a duplicate, old, out of sequence, or arriving after a gap. The confidentiality state will be set to "false".
public void verifyMIC(InputStream tokStream, InputStream msgStream, MessageProp msgProp) throws GSSException
Verifies the cryptographic MIC, contained in the token parameter, over the supplied message. This method is equivalent in functionality to its byte array counterpart.
The MessageProp object is instantiated by the application and is used by the underlying mechanism to return information to the caller such as the QOP indicating the strength of protection that was applied to the message and other supplementary message state information.
Since some application-level protocols may wish to use tokens emitted by getMIC to provide "secure framing", implementations should support the calculation and verification of MICs over zero-length messages.
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Parameters:
tokStream: Input stream containing the token generated by the peer's getMIC method.
msgStream: Input stream containing the application message over which to verify the cryptographic MIC.
msgProp: Upon return from the method, this object will contain the applied QOP and supplementary information, described in section 5.12.3, stating whether the token was a duplicate, old, out of sequence, or arriving after a gap. The confidentiality state will be set to "false".
Provided to support the sharing of work between multiple processes. This routine will typically be used by the context acceptor, in an application where a single process receives incoming connection requests and accepts security contexts over them, then passes the established context to one or more other processes for message exchange.
This method deactivates the security context and creates an inter- process token 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 inter-process token may be imported, either as a function of local security policy, or as a result of implementation decisions. For example, some implementations may constrain contexts to be passed only between processes that run under the same account, or which are part of the same process group.
The inter-process token may contain security-sensitive information (for example, cryptographic keys). While mechanisms are encouraged to either avoid placing such sensitive information within inter- process tokens or to encrypt the token before returning it to the application, in a typical GSS-API implementation, this may not be possible. Thus, the application must take care to protect the inter-process token, and ensure that any process to which the token is transferred is trustworthy.
public void requestMutualAuth(boolean state) throws GSSException
Sets the request state of the mutual authentication flag for the context. This method is only valid before the context creation process begins and only for the initiator.
Parameters:
state: Boolean representing if mutual authentication should be requested during context establishment.
public void requestReplayDet(boolean state) throws GSSException
Sets the request state of the replay detection service for the context. This method is only valid before the context creation process begins and only for the initiator.
Parameters:
state: Boolean representing if replay detection is desired over the established context.
public void requestSequenceDet(boolean state) throws GSSException
Sets the request state for the sequence checking service of the context. This method is only valid before the context creation process begins and only for the initiator.
Parameters:
state: Boolean representing if sequence detection is desired over the established context.
public void requestCredDeleg(boolean state) throws GSSException
Sets the request state for the credential delegation flag for the context. This method is only valid before the context creation process begins and only for the initiator.
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Parameters:
state: Boolean representing if credential delegation is desired.
public void requestConf(boolean state) throws GSSException
Requests that confidentiality service be available over the context. This method is only valid before the context creation process begins and only for the initiator.
Parameters:
state: Boolean indicating if confidentiality services are to be requested for the context.
public void requestInteg(boolean state) throws GSSException
Requests that integrity services be available over the context. This method is only valid before the context creation process begins and only for the initiator.
Parameters:
state: Boolean indicating if integrity services are to be requested for the context.
public void requestLifetime(int lifetime) throws GSSException
Sets the desired lifetime for the context in seconds. This method is only valid before the context creation process begins and only for the initiator. Use GSSContext.INDEFINITE_LIFETIME and GSSContext.DEFAULT_LIFETIME to request indefinite or default context lifetime.
Parameters:
lifetime: The desired context lifetime in seconds.
Returns the state of the delegated credentials for the context. When issued before context establishment is completed or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
Returns the state of the mutual authentication option for the context. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
Returns the state of the replay detection option for the context. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
Returns the state of the sequence detection option for the context. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
Returns "true" if this is an anonymous context. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
public boolean isTransferable() throws GSSException
Returns "true" if the context is transferable to other processes through the use of the export method. This call is only valid on fully established contexts.
Returns "true" if the per-message operations can be applied over the context. Some mechanisms may allow the usage of per-message operations before the context is fully established. This will also indicate that the get methods will return actual context state characteristics instead of the desired ones.
Returns the confidentiality service state over the context. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
Returns the integrity service state over the context. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired state; otherwise, it will indicate the actual state over the established context.
Returns the context lifetime in seconds. When issued before context establishment completes or when the isProtReady method returns "false", it returns the desired lifetime; otherwise, it will indicate the remaining lifetime for the context.
Returns the name of the context initiator. This call is valid only after the context is fully established or the isProtReady method returns "true". It is guaranteed to return an MN.
Returns the name of the context target (acceptor). This call is valid only after the context is fully established or the isProtReady method returns "true". It is guaranteed to return an MN.
Returns the mechanism oid for this context. This method may be called before the context is fully established, but the mechanism returned may change on successive calls in negotiated mechanism case.
public GSSCredential getDelegCred() throws GSSException
Returns the delegated credential object on the acceptor's side. To check for availability of delegated credentials call getDelegCredState. This call is only valid on fully established contexts.
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.
public void setSupplementaryStates(boolean duplicate, boolean old, boolean unseq, boolean gap, int minorStatus, String minorString)
This method sets the state for the supplementary information flags and the minor status in MessageProp. It is not used by the application but by the GSS implementation to return this information to the caller of a per-message context method.
Parameters:
duplicate: "true" if the token was a duplicate of an earlier token; otherwise, "false".
old: "true" if the token's validity period has expired; otherwise, "false".
unseq: "true" if a later token has already been processed; otherwise, "false".
gap: "true" if one or more predecessor tokens have not yet been successfully processed; otherwise, "false".
minorStatus: The integer minor status code that the underlying mechanism wants to set.
minorString: The textual representation of the minorStatus value.
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.
public ChannelBinding(InetAddress initAddr, InetAddress acceptAddr, byte[] appData)
Create a ChannelBinding object with user-supplied address information and data. "null" values can be used for any fields that the application does not want to specify.
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.
acceptAddr: The 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.
Parameters:
appData: Application supplied data to be used as part of the channel bindings.
Returns application data being used as part of the ChannelBinding. "null" is returned if no application data has been specified for the channel binding.
Returns "true" if two channel bindings match. (Note that the Java language specification requires that two objects that are equal according to the equals(Object) method must return the same integer result when the hashCode() method is called on them.)
Parameters:
obj: Another channel binding with which to compare.
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 the Kerberos v5 mechanism is "1.2.840.113554.1.2.2".
The GSSName name class contains public static Oid objects representing the standard name types defined in GSS-API.
Creates an Oid object from a string representation of its integer components (e.g., "1.2.840.113554.1.2.2").
Parameters:
strOid: The string representation for the oid.
public Oid(InputStream derOid) throws GSSException
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Creates an Oid object from its DER encoding. This refers to the full encoding including tag and length. The structure and encoding of Oids is defined in ISOIEC-8824 and ISOIEC-8825. This method is identical in functionality to its byte array counterpart.
Parameters:
derOid: Stream containing the DER-encoded oid.
public Oid(byte[] DEROid) throws GSSException
Creates an Oid object from its DER encoding. This refers to the full encoding including tag and length. The structure and encoding of Oids is defined in ISOIEC-8824 and ISOIEC-8825. This method is identical in functionality to its byte array counterpart.
Returns "true" if the two Oid objects represent the same oid value. (Note that the Java language specification [JLS] requires that two objects that are equal according to the equals(Object) method must return the same integer result when the hashCode() method is called on them.)
This exception is thrown whenever a fatal GSS-API error occurs including mechanism-specific errors. It may contain both, the major and minor, GSS-API status codes. The mechanism implementors are responsible for setting appropriate minor status codes when throwing this exception. Aside from delivering the numeric error code(s) to the caller, this class performs the mapping from their numeric values to textual representations. All Java GSS-API methods are declared throwing this exception.
All implementations are encouraged to use the Java internationalization techniques to provide local translations of the message strings.
All valid major GSS-API error code values are declared as constants in this class.
public static final int BAD_BINDINGS
Channel bindings mismatch error. The value of this constant is 1.
public static final int BAD_MECH
Unsupported mechanism requested error. The value of this constant is 2.
public static final int BAD_NAME
Invalid name provided error. The value of this constant is 3.
public static final int BAD_NAMETYPE
Name of unsupported type provided error. The value of this constant is 4.
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public static final int BAD_STATUS
Invalid status code error - this is the default status value. The value of this constant is 5.
public static final int BAD_MIC
Token had invalid integrity check error. The value of this constant is 6.
public static final int CONTEXT_EXPIRED
Specified security context expired error. The value of this constant is 7.
public static final int CREDENTIALS_EXPIRED
Expired credentials detected error. The value of this constant is 8.
public static final int DEFECTIVE_CREDENTIAL
Defective credential error. The value of this constant is 9.
public static final int DEFECTIVE_TOKEN
Defective token error. The value of this constant is 10.
public static final int FAILURE
General failure, unspecified at GSS-API level. The value of this constant is 11.
public static final int NO_CONTEXT
Invalid security context error. The value of this constant is 12.
public static final int NO_CRED
Invalid credentials error. The value of this constant is 13.
public static final int BAD_QOP
Unsupported QOP value error. The value of this constant is 14.
public static final int UNAUTHORIZED
Operation unauthorized error. The value of this constant is 15.
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public static final int UNAVAILABLE
Operation unavailable error. The value of this constant is 16.
public static final int DUPLICATE_ELEMENT
Duplicate credential element requested error. The value of this constant is 17.
public static final int NAME_NOT_MN
Name contains multi-mechanism elements error. The value of this constant is 18.
public static final int DUPLICATE_TOKEN
The token was a duplicate of an earlier token. This is contained in an exception only when detected during context establishment, in which case it is considered a fatal error. (Non-fatal supplementary codes are indicated via the MessageProp object.) The value of this constant is 19.
public static final int OLD_TOKEN
The token's validity period has expired. This is contained in an exception only when detected during context establishment, in which case it is considered a fatal error. (Non-fatal supplementary codes are indicated via the MessageProp object.) The value of this constant is 20.
public static final int UNSEQ_TOKEN
A later token has already been processed. This is contained in an exception only when detected during context establishment, in which case it is considered a fatal error. (Non-fatal supplementary codes are indicated via the MessageProp object.) The value of this constant is 21.
public static final int GAP_TOKEN
An expected per-message token was not received. This is contained in an exception only when detected during context establishment, in which case it is considered a fatal error. (Non-fatal supplementary codes are indicated via the MessageProp object.) The value of this constant is 22.
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.
Returns the mechanism error code that caused this exception. The minor code is set by the underlying mechanism. Value of 0 indicates that mechanism error code is not set.
Returns a detailed message of this exception. Overrides Throwable.getMessage. It is customary in Java to use this method to obtain exception information.
/** * This is a partial sketch for a simple client program that acts * as a GSS context initiator. It illustrates how to use the Java * bindings for the GSS-API specified in * Generic Security Service API Version 2 : Java bindings * * * This code sketch assumes the existence of a GSS-API * implementation that supports the mechanism that it will need * and is present as a library package (org.ietf.jgss) either as * part of the standard JRE or in the CLASSPATH the application * specifies. */
public class SimpleClient {
private String serviceName; // name of peer (i.e., server) private GSSCredential clientCred = null; private GSSContext context = null; private Oid mech; // underlying mechanism to use
if (!context.isEstablished()) inToken = readGSSToken(); }
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GSSName peer = context.getSrcName(); print("Security context established with " + peer + " using underlying mechanism " + mech.toString()); } catch (GSSException e) { print("GSS-API error during context establishment: " + e.getMessage()); ... ... }
... ... }
/** * Sends some data to the server and reads back the * response. */ private void doCommunication() { byte[] inToken = null; byte[] outToken = null; byte[] buffer;
// Container for multiple input-output arguments to and // from the per-message routines (e.g., wrap/unwrap). MessageProp messgInfo = new MessageProp();
try {
/* * Now send some bytes to the server to be * processed. They will be integrity protected * but not encrypted for privacy. */
buffer = readFromFile();
// Set privacy to "false" and use the default QOP messgInfo.setPrivacy(false);
/** * This is a partial sketch for a simple server program that acts * as a GSS context acceptor. It illustrates how to use the Java * bindings for the GSS-API specified in * Generic Security Service API Version 2 : Java bindings. * * This code sketch assumes the existence of a GSS-API * implementation that supports the mechanisms that it will need * and is present as a library package (org.ietf.jgss) either as * part of the standard JRE or in the CLASSPATH the application * specifies. */
// Container for multiple input-output arguments to // and from the per-message routines // (i.e., wrap/unwrap). MessageProp supplInfo = new MessageProp(); GSSContext secContext = null;
The Java language security model allows platform providers to have policy-based fine-grained access control over any resource that an application wants. When using a Java security manager (such as, but not limited to, the case of applets running in browsers) the application code is in a sandbox by default.
Administrators of the platform JRE determine what permissions, if any, are to be given to source from different codebases. Thus, the administrator has to be aware of any special requirements that the GSS provider might have for system resources. For instance, a Kerberos provider might wish to make a network connection to the Key Distribution Center (KDC) to obtain initial credentials. This would not be allowed under the sandbox unless the administrator had granted permissions for this. Also, note that this granting and checking of permissions happens transparently to the application and is outside the scope of this document.
The Java language allows administrators to pre-configure a list of security service providers in the <JRE>/lib/security/java.security file. At runtime, the system approaches these providers in order of preference when looking for security related services. Applications have a means to modify this list through methods in the "Security" class in the "java.security" package. However, since these modifications would be visible in the entire Java Virtual Machine (JVM) and thus affect all code executing in it, this operation is not available in the sandbox and requires special permissions to perform. Thus, when a GSS application has special needs that are met by a particular security provider, it has two choices:
1) To install the provider on a JVM-wide basis using the java.security.Security class and then depend on the system to find the right provider automatically when the need arises. (This would require the application to be granted a "insertProvider SecurityPermission".)
2) To pass an instance of the provider to the local instance of GSSManager so that only factory calls going through that GSSManager use the desired provider. (This would not require any permissions.)
This proposed API leverages earlier work performed by the IETF's CAT WG as outlined in both RFC 2743 [GSSAPIv2-UPDATE] and RFC 2744 [GSSAPI-Cbind]. Many conceptual definitions, implementation directions, and explanations have been included from these documents.
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We would like to thank Mike Eisler, Lin Ling, Ram Marti, Michael Saltz, and other members of Sun's development team for their helpful input, comments, and suggestions.
We would also like to thank Joe Salowey, and Michael Smith for many insightful ideas and suggestions that have contributed to this document.
RFC 2853 listed all the GSS status code values in two different sections: section 4.12.1 defined numeric values for them, and section 6.8.1 defined them as static constants in the GSSException class without assigning any values. Due to an inconsistent ordering between these two sections, all of the GSS major status codes resulted in misalignment, and a subsequent disagreement between deployed implementations.
This document defines the numeric values of the GSS status codes in both sections, while maintaining the original ordering from section 6.8.1 of RFC 2853 [RFC2853], and obsoletes the GSS status code values defined in section 4.12.1. The relevant sections in this document are sections 5.12.1 and 7.8.1.
2) GSS Credential Usage Constant Values
RFC 2853 section 6.3.2 defines static constants for the GSSCredential usage flags. However, the values of these constants were not defined anywhere in RFC 2853 [RFC2853].
[GSSAPI-Cbind] Wray, J., "Generic Security Service API Version 2 : C-bindings", RFC 2744, January 2000.
[GSSAPIv2-UPDATE] Linn, J., "Generic Security Service Application Program Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism (SPKM)", RFC 2025, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2853] Kabat, J. and M. Upadhyay, "Generic Security Service API Version 2 : Java Bindings", RFC 2853, June 2000.
[RFC4121] Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos Version 5 Generic Security Service Application Program Interface (GSS-API) Mechanism: Version 2", RFC 4121, July 2005.