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Network Working Group J. Linn Request for Comments: 2078 OpenVision Technologies Category: Standards Track January 1997 Obsoletes: 1508

 Generic Security Service Application Program Interface, Version 2

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.

Abstract

 The Generic Security Service Application Program Interface (GSS-API),
 as defined in RFC-1508, provides security services to callers in a
 generic fashion, supportable with a range of underlying mechanisms
 and technologies and hence allowing source-level portability of
 applications to different environments. This specification defines
 GSS-API services and primitives at a level independent of underlying
 mechanism and programming language environment, and is to be
 complemented by other, related specifications:
    documents defining specific parameter bindings for particular
    language environments
    documents defining token formats, protocols, and procedures to be
    implemented in order to realize GSS-API services atop particular
    security mechanisms
 This memo revises RFC-1508, making specific, incremental changes in
 response to implementation experience and liaison requests. It is
 intended, therefore, that this memo or a successor version thereto
 will become the basis for subsequent progression of the GSS-API
 specification on the standards track.

Table of Contents

 1: GSS-API Characteristics and Concepts..........................  3
 1.1: GSS-API Constructs..........................................  6
 1.1.1:  Credentials..............................................  6
 1.1.1.1: Credential Constructs and Concepts......................  6
 1.1.1.2: Credential Management...................................  7
 1.1.1.3: Default Credential Resolution...........................  8

Linn Standards Track [Page 1] RFC 2078 GSS-API January 1997

 1.1.2: Tokens....................................................  9
 1.1.3:  Security Contexts........................................ 10
 1.1.4:  Mechanism Types.......................................... 11
 1.1.5:  Naming................................................... 12
 1.1.6:  Channel Bindings......................................... 14
 1.2:  GSS-API Features and Issues................................ 15
 1.2.1:  Status Reporting......................................... 15
 1.2.2: Per-Message Security Service Availability................. 17
 1.2.3: Per-Message Replay Detection and Sequencing............... 18
 1.2.4:  Quality of Protection.................................... 20
 1.2.5: Anonymity Support......................................... 21
 1.2.6: Initialization............................................ 22
 1.2.7: Per-Message Protection During Context Establishment....... 22
 1.2.8: Implementation Robustness................................. 23
 2:  Interface Descriptions....................................... 23
 2.1:  Credential management calls................................ 25
 2.1.1:  GSS_Acquire_cred call.................................... 26
 2.1.2:  GSS_Release_cred call.................................... 28
 2.1.3:  GSS_Inquire_cred call.................................... 29
 2.1.4:  GSS_Add_cred call........................................ 31
 2.1.5:  GSS_Inquire_cred_by_mech call............................ 33
 2.2:  Context-level calls........................................ 34
 2.2.1:  GSS_Init_sec_context call................................ 34
 2.2.2:  GSS_Accept_sec_context call.............................. 40
 2.2.3:  GSS_Delete_sec_context call.............................. 44
 2.2.4:  GSS_Process_context_token call........................... 46
 2.2.5:  GSS_Context_time call.................................... 47
 2.2.6:  GSS_Inquire_context call................................. 47
 2.2.7:  GSS_Wrap_size_limit call................................. 49
 2.2.8:  GSS_Export_sec_context call.............................. 50
 2.2.9:  GSS_Import_sec_context call.............................. 52
 2.3:  Per-message calls.......................................... 53
 2.3.1:  GSS_GetMIC call.......................................... 54
 2.3.2:  GSS_VerifyMIC call....................................... 55
 2.3.3:  GSS_Wrap call............................................ 56
 2.3.4:  GSS_Unwrap call.......................................... 58
 2.4:  Support calls.............................................. 59
 2.4.1:  GSS_Display_status call.................................. 60
 2.4.2:  GSS_Indicate_mechs call.................................. 60
 2.4.3:  GSS_Compare_name call.................................... 61
 2.4.4:  GSS_Display_name call.................................... 62
 2.4.5:  GSS_Import_name call..................................... 63
 2.4.6:  GSS_Release_name call.................................... 64
 2.4.7:  GSS_Release_buffer call.................................. 65
 2.4.8:  GSS_Release_OID_set call................................. 65
 2.4.9:  GSS_Create_empty_OID_set call............................ 66
 2.4.10: GSS_Add_OID_set_member call.............................. 67
 2.4.11: GSS_Test_OID_set_member call............................. 67

Linn Standards Track [Page 2] RFC 2078 GSS-API January 1997

 2.4.12: GSS_Release_OID call..................................... 68
 2.4.13: GSS_OID_to_str call...................................... 68
 2.4.14: GSS_Str_to_OID call...................................... 69
 2.4.15: GSS_Inquire_names_for_mech call.......................... 69
 2.4.16: GSS_Inquire_mechs_for_name call.......................... 70
 2.4.17: GSS_Canonicalize_name call............................... 71
 2.4.18: GSS_Export_name call..................................... 72
 2.4.19: GSS_Duplicate_name call.................................. 73
 3: Data Structure Definitions for GSS-V2 Usage................... 73
 3.1: Mechanism-Independent Token Format.......................... 74
 3.2: Mechanism-Independent Exported Name Object Format........... 77
 4: Name Type Definitions......................................... 77
 4.1: Host-Based Service Name Form................................ 77
 4.2: User Name Form.............................................. 78
 4.3: Machine UID Form............................................ 78
 4.4: String UID Form............................................. 79
 5:  Mechanism-Specific Example Scenarios......................... 79
 5.1: Kerberos V5, single-TGT..................................... 79
 5.2: Kerberos V5, double-TGT..................................... 80
 5.3:  X.509 Authentication Framework............................. 81
 6:  Security Considerations...................................... 82
 7:  Related Activities........................................... 82
 Appendix A: Mechanism Design Constraints......................... 83
 Appendix B: Compatibility with GSS-V1............................ 83

1: GSS-API Characteristics and Concepts

 GSS-API operates in the following paradigm.  A typical GSS-API caller
 is itself a communications protocol, calling on GSS-API in order to
 protect its communications with authentication, integrity, and/or
 confidentiality security services.  A GSS-API caller accepts tokens
 provided to it by its local GSS-API implementation and transfers the
 tokens to a peer on a remote system; that peer passes the received
 tokens to its local GSS-API implementation for processing. The
 security services available through GSS-API in this fashion are
 implementable (and have been implemented) over a range of underlying
 mechanisms based on secret-key and public-key cryptographic
 technologies.
 The GSS-API separates the operations of initializing a security
 context between peers, achieving peer entity authentication (This
 security service definition, and other definitions used in this
 document, corresponds to that provided in International Standard ISO
 7498-2-1988(E), Security Architecture.) (GSS_Init_sec_context()  and
 GSS_Accept_sec_context() calls), from the operations of providing
 per-message data origin authentication and data integrity protection
 (GSS_GetMIC()  and GSS_VerifyMIC()  calls) for messages subsequently
 transferred in conjunction with that context.  When establishing a

Linn Standards Track [Page 3] RFC 2078 GSS-API January 1997

 security context, the GSS-API enables a context initiator to
 optionally permit its credentials to be delegated, meaning that the
 context acceptor may initiate further security contexts on behalf of
 the initiating caller. Per-message GSS_Wrap()  and GSS_Unwrap() calls
 provide the data origin authentication and data integrity services
 which GSS_GetMIC()  and GSS_VerifyMIC() offer, and also support
 selection of confidentiality services as a caller option.  Additional
 calls provide supportive functions to the GSS-API's users.
 The following paragraphs provide an example illustrating the
 dataflows involved in use of the GSS-API by a client and server in a
 mechanism-independent fashion, establishing a security context and
 transferring a protected message. The example assumes that credential
 acquisition has already been completed.  The example assumes that the
 underlying authentication technology is capable of authenticating a
 client to a server using elements carried within a single token, and
 of authenticating the server to the client (mutual authentication)
 with a single returned token; this assumption holds for presently-
 documented CAT mechanisms but is not necessarily true for other
 cryptographic technologies and associated protocols.
 The client calls GSS_Init_sec_context()  to establish a security
 context to the server identified by targ_name, and elects to set the
 mutual_req_flag so that mutual authentication is performed in the
 course of context establishment. GSS_Init_sec_context()  returns an
 output_token to be passed to the server, and indicates
 GSS_S_CONTINUE_NEEDED status pending completion of the mutual
 authentication sequence. Had mutual_req_flag not been set, the
 initial call to GSS_Init_sec_context()  would have returned
 GSS_S_COMPLETE status. The client sends the output_token to the
 server.
 The server passes the received token as the input_token parameter to
 GSS_Accept_sec_context().  GSS_Accept_sec_context indicates
 GSS_S_COMPLETE status, provides the client's authenticated identity
 in the src_name result, and provides an output_token to be passed to
 the client. The server sends the output_token to the client.
 The client passes the received token as the input_token parameter to
 a successor call to GSS_Init_sec_context(),  which processes data
 included in the token in order to achieve mutual authentication from
 the client's viewpoint. This call to GSS_Init_sec_context()  returns
 GSS_S_COMPLETE status, indicating successful mutual authentication
 and the completion of context establishment for this example.
 The client generates a data message and passes it to GSS_Wrap().
 GSS_Wrap() performs data origin authentication, data integrity, and
 (optionally) confidentiality processing on the message and

Linn Standards Track [Page 4] RFC 2078 GSS-API January 1997

 encapsulates the result into output_message, indicating
 GSS_S_COMPLETE status. The client sends the output_message to the
 server.
 The server passes the received message to GSS_Unwrap().  GSS_Unwrap()
 inverts the encapsulation performed by GSS_Wrap(),  deciphers the
 message if the optional confidentiality feature was applied, and
 validates the data origin authentication and data integrity checking
 quantities. GSS_Unwrap()  indicates successful validation by
 returning GSS_S_COMPLETE status along with the resultant
 output_message.
 For purposes of this example, we assume that the server knows by
 out-of-band means that this context will have no further use after
 one protected message is transferred from client to server. Given
 this premise, the server now calls GSS_Delete_sec_context() to flush
 context-level information.  Optionally, the server-side application
 may provide a token buffer to GSS_Delete_sec_context(), to receive a
 context_token to be transferred to the client in order to request
 that client-side context-level information be deleted.
 If a context_token is transferred, the client passes the
 context_token to GSS_Process_context_token(), which returns
 GSS_S_COMPLETE status after deleting context-level information at the
 client system.
 The GSS-API design assumes and addresses several basic goals,
 including:
    Mechanism independence: The GSS-API defines an interface to
    cryptographically implemented strong authentication and other
    security services at a generic level which is independent of
    particular underlying mechanisms. For example, GSS-API-provided
    services can be implemented by secret-key technologies (e.g.,
    Kerberos) or public-key approaches (e.g., X.509).
    Protocol environment independence: The GSS-API is independent of
    the communications protocol suites with which it is employed,
    permitting use in a broad range of protocol environments. In
    appropriate environments, an intermediate implementation "veneer"
    which is oriented to a particular communication protocol (e.g.,
    Remote Procedure Call (RPC)) may be interposed between
    applications which call that protocol and the GSS-API, thereby
    invoking GSS-API facilities in conjunction with that protocol's
    communications invocations.
    Protocol association independence: The GSS-API's security context
    construct is independent of communications protocol association

Linn Standards Track [Page 5] RFC 2078 GSS-API January 1997

    constructs. This characteristic allows a single GSS-API
    implementation to be utilized by a variety of invoking protocol
    modules on behalf of those modules' calling applications. GSS-API
    services can also be invoked directly by applications, wholly
    independent of protocol associations.
    Suitability to a range of implementation placements: GSS-API
    clients are not constrained to reside within any Trusted Computing
    Base (TCB) perimeter defined on a system where the GSS-API is
    implemented; security services are specified in a manner suitable
    to both intra-TCB and extra-TCB callers.

1.1: GSS-API Constructs

 This section describes the basic elements comprising the GSS-API.

1.1.1: Credentials

1.1.1.1: Credential Constructs and Concepts

 Credentials provide the prerequisites which permit GSS-API peers to
 establish security contexts with each other. A caller may designate
 that the credential elements which are to be applied for context
 initiation or acceptance be selected by default.  Alternately, those
 GSS-API callers which need to make explicit selection of particular
 credentials structures may make references to those credentials
 through GSS-API-provided credential handles ("cred_handles").  In all
 cases, callers' credential references are indirect, mediated by GSS-
 API implementations and not requiring callers to access the selected
 credential elements.
 A single credential structure may be used to initiate outbound
 contexts and to accept inbound contexts. Callers needing to operate
 in only one of these modes may designate this fact when credentials
 are acquired for use, allowing underlying mechanisms to optimize
 their processing and storage requirements. The credential elements
 defined by a particular mechanism may contain multiple cryptographic
 keys, e.g., to enable authentication and message encryption to be
 performed with different algorithms.
 A GSS-API credential structure may contain multiple credential
 elements, each containing mechanism-specific information for a
 particular underlying mechanism (mech_type), but the set of elements
 within a given credential structure represent a common entity.  A
 credential structure's contents will vary depending on the set of
 mech_types supported by a particular GSS-API implementation. Each
 credential element identifies the data needed by its mechanism in
 order to establish contexts on behalf of a particular principal, and

Linn Standards Track [Page 6] RFC 2078 GSS-API January 1997

 may contain separate credential references for use in context
 initiation and context acceptance.  Multiple credential elements
 within a given credential having overlapping combinations of
 mechanism, usage mode, and validity period are not permitted.
 Commonly, a single mech_type will be used for all security contexts
 established by a particular initiator to a particular target. A major
 motivation for supporting credential sets representing multiple
 mech_types is to allow initiators on systems which are equipped to
 handle multiple types to initiate contexts to targets on other
 systems which can accommodate only a subset of the set supported at
 the initiator's system.

1.1.1.2: Credential Management

 It is the responsibility of underlying system-specific mechanisms and
 OS functions below the GSS-API to ensure that the ability to acquire
 and use credentials associated with a given identity is constrained
 to appropriate processes within a system. This responsibility should
 be taken seriously by implementors, as the ability for an entity to
 utilize a principal's credentials is equivalent to the entity's
 ability to successfully assert that principal's identity.
 Once a set of GSS-API credentials is established, the transferability
 of that credentials set to other processes or analogous constructs
 within a system is a local matter, not defined by the GSS-API. An
 example local policy would be one in which any credentials received
 as a result of login to a given user account, or of delegation of
 rights to that account, are accessible by, or transferable to,
 processes running under that account.
 The credential establishment process (particularly when performed on
 behalf of users rather than server processes) is likely to require
 access to passwords or other quantities which should be protected
 locally and exposed for the shortest time possible. As a result, it
 will often be appropriate for preliminary credential establishment to
 be performed through local means at user login time, with the
 result(s) cached for subsequent reference. These preliminary
 credentials would be set aside (in a system-specific fashion) for
 subsequent use, either:
    to be accessed by an invocation of the GSS-API GSS_Acquire_cred()
    call, returning an explicit handle to reference that credential
    to comprise default credential elements to be installed, and to be
    used when default credential behavior is requested on behalf of a
    process

Linn Standards Track [Page 7] RFC 2078 GSS-API January 1997

1.1.1.3: Default Credential Resolution

 The gss_init_sec_context and gss_accept_sec_context routines allow
 the value GSS_C_NO_CREDENTIAL to be specified as their credential
 handle parameter.  This special credential-handle indicates 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:
 GSS_Init_sec_context:
    (i) If there is only a single principal capable of initiating
    security contexts that the application is authorized to act on
    behalf of, then that principal shall be used, otherwise
    (ii) If the platform maintains a concept of a default network-
    identity, 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
    (iii) If the platform maintains a concept of a default local
    identity, and provides a means to map local identities into
    network-identities, 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, then the
    principal corresponding to that identity shall be used, otherwise
    (iv) A user-configurable default identity should be used.
 GSS_Accept_sec_context:
    (i) If there is only a single authorized principal identity
    capable of accepting security contexts, then that principal shall
    be used, otherwise
    (ii) If the mechanism can determine the identity of the target
    principal by examining the context-establishment token, and if the
    accepting application is authorized to act as that principal for
    the purpose of accepting security contexts, then that principal
    identity shall be used, otherwise
    (iii) If the mechanism supports context acceptance by any
    principal, and mutual authentication was not requested, any
    principal that the application is authorized to accept security
    contexts under may be used, otherwise

Linn Standards Track [Page 8] RFC 2078 GSS-API January 1997

    (iv) 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
 wherever possible.  Applications requesting default behavior are
 likely to be more portable across mechanisms and platforms than ones
 that use GSS_Acquire_cred to request a specific identity.

1.1.2: Tokens

 Tokens are data elements transferred between GSS-API callers, and are
 divided into two classes. Context-level tokens are exchanged in order
 to establish and manage a security context between peers. Per-message
 tokens relate to an established context and are exchanged to provide
 protective security services (i.e., data origin authentication,
 integrity, and optional confidentiality) for corresponding data
 messages.
 The first context-level token obtained from GSS_Init_sec_context() is
 required to indicate at its very beginning a globally-interpretable
 mechanism identifier, i.e., an Object Identifier (OID) of the
 security mechanism. The remaining part of this token as well as the
 whole content of all other tokens are specific to the particular
 underlying mechanism used to support the GSS-API. Section 3 of this
 document provides, for designers of GSS-API support mechanisms, the
 description of the header of the first context-level token which is
 then followed by mechanism-specific information.
 Tokens' contents are opaque from the viewpoint of GSS-API callers.
 They are generated within the GSS-API implementation at an end
 system, provided to a GSS-API caller to be transferred to the peer
 GSS-API caller at a remote end system, and processed by the GSS-API
 implementation at that remote end system. Tokens may be output by
 GSS-API calls (and should be transferred to GSS-API peers) whether or
 not the calls' status indicators indicate successful completion.
 Token transfer may take place in an in-band manner, integrated into
 the same protocol stream used by the GSS-API callers for other data
 transfers, or in an out-of-band manner across a logically separate
 channel.
 Different GSS-API tokens are used for different purposes (e.g.,
 context initiation, context acceptance, protected message data on an
 established context), and it is the responsibility of a GSS-API
 caller receiving tokens to distinguish their types, associate them
 with corresponding security contexts, and pass them to appropriate
 GSS-API processing routines.  Depending on the caller protocol
 environment, this distinction may be accomplished in several ways.

Linn Standards Track [Page 9] RFC 2078 GSS-API January 1997

 The following examples illustrate means through which tokens' types
 may be distinguished:
  1. implicit tagging based on state information (e.g., all tokens on

a new association are considered to be context establishment

    tokens until context establishment is completed, at which point
    all tokens are considered to be wrapped data objects for that
    context),
  1. explicit tagging at the caller protocol level,
  1. a hybrid of these approaches.
 Commonly, the encapsulated data within a token includes internal
 mechanism-specific tagging information, enabling mechanism-level
 processing modules to distinguish tokens used within the mechanism
 for different purposes.  Such internal mechanism-level tagging is
 recommended to mechanism designers, and enables mechanisms to
 determine whether a caller has passed a particular token for
 processing by an inappropriate GSS-API routine.
 Development of GSS-API support primitives based on a particular
 underlying cryptographic technique and protocol (i.e., conformant to
 a specific GSS-API mechanism definition) does not necessarily imply
 that GSS-API callers using that GSS-API mechanism will be able to
 interoperate with peers invoking the same technique and protocol
 outside the GSS-API paradigm, or with peers implementing a different
 GSS-API mechanism based on the same underlying technology.  The
 format of GSS-API tokens defined in conjunction with a particular
 mechanism, and the techniques used to integrate those tokens into
 callers' protocols, may not be interoperable with the tokens used by
 non-GSS-API callers of the same underlying technique.

1.1.3: Security Contexts

 Security contexts are established between peers, using credentials
 established locally in conjunction with each peer or received by
 peers via delegation. Multiple contexts may exist simultaneously
 between a pair of peers, using the same or different sets of
 credentials. Coexistence of multiple contexts using different
 credentials allows graceful rollover when credentials expire.
 Distinction among multiple contexts based on the same credentials
 serves applications by distinguishing different message streams in a
 security sense.
 The GSS-API is independent of underlying protocols and addressing
 structure, and depends on its callers to transport GSS-API-provided
 data elements. As a result of these factors, it is a caller

Linn Standards Track [Page 10] RFC 2078 GSS-API January 1997

 responsibility to parse communicated messages, separating GSS-API-
 related data elements from caller-provided data.  The GSS-API is
 independent of connection vs. connectionless orientation of the
 underlying communications service.
 No correlation between security context and communications protocol
 association is dictated. (The optional channel binding facility,
 discussed in Section 1.1.6 of this document, represents an
 intentional exception to this rule, supporting additional protection
 features within GSS-API supporting mechanisms.) This separation
 allows the GSS-API to be used in a wide range of communications
 environments, and also simplifies the calling sequences of the
 individual calls. In many cases (depending on underlying security
 protocol, associated mechanism, and availability of cached
 information), the state information required for context setup can be
 sent concurrently with initial signed user data, without interposing
 additional message exchanges.

1.1.4: Mechanism Types

 In order to successfully establish a security context with a target
 peer, it is necessary to identify an appropriate underlying mechanism
 type (mech_type) which both initiator and target peers support. The
 definition of a mechanism embodies not only the use of a particular
 cryptographic technology (or a hybrid or choice among alternative
 cryptographic technologies), but also definition of the syntax and
 semantics of data element exchanges which that mechanism will employ
 in order to support security services.
 It is recommended that callers initiating contexts specify the
 "default" mech_type value, allowing system-specific functions within
 or invoked by the GSS-API implementation to select the appropriate
 mech_type, but callers may direct that a particular mech_type be
 employed when necessary.
 The means for identifying a shared mech_type to establish a security
 context with a peer will vary in different environments and
 circumstances; examples include (but are not limited to):
    use of a fixed mech_type, defined by configuration, within an
    environment
    syntactic convention on a target-specific basis, through
    examination of a target's name
    lookup of a target's name in a naming service or other database in
    order to identify mech_types supported by that target

Linn Standards Track [Page 11] RFC 2078 GSS-API January 1997

    explicit negotiation between GSS-API callers in advance of
    security context setup
 When transferred between GSS-API peers, mech_type specifiers (per
 Section 3, represented as Object Identifiers (OIDs)) serve to qualify
 the interpretation of associated tokens. (The structure and encoding
 of Object Identifiers is defined in ISO/IEC 8824, "Specification of
 Abstract Syntax Notation One (ASN.1)" and in ISO/IEC 8825,
 "Specification of Basic Encoding Rules for Abstract Syntax Notation
 One (ASN.1)".) Use of hierarchically structured OIDs serves to
 preclude ambiguous interpretation of mech_type specifiers. The OID
 representing the DASS MechType, for example, is 1.3.12.2.1011.7.5,
 and that of the Kerberos V5 mechanism, once advanced to the level of
 Proposed Standard, will be 1.2.840.113554.1.2.2.

1.1.5: Naming

 The GSS-API avoids prescribing naming structures, treating the names
 which are transferred across the interface in order to initiate and
 accept security contexts as opaque objects.  This approach supports
 the GSS-API's goal of implementability atop a range of underlying
 security mechanisms, recognizing the fact that different mechanisms
 process and authenticate names which are presented in different
 forms. Generalized services offering translation functions among
 arbitrary sets of naming environments are outside the scope of the
 GSS-API; availability and use of local conversion functions to
 translate among the naming formats supported within a given end
 system is anticipated.
 Different classes of name representations are used in conjunction
 with different GSS-API parameters:
  1. Internal form (denoted in this document by INTERNAL NAME),

opaque to callers and defined by individual GSS-API

    implementations.  GSS-API implementations supporting multiple
    namespace types must maintain internal tags to disambiguate the
    interpretation of particular names.  A Mechanism Name (MN) is a
    special case of INTERNAL NAME, guaranteed to contain elements
    corresponding to one and only one mechanism; calls which are
    guaranteed to emit MNs or which require MNs as input are so
    identified within this specification.
  1. Contiguous string ("flat") form (denoted in this document by

OCTET STRING); accompanied by OID tags identifying the namespace

    to which they correspond.  Depending on tag value, flat names may
    or may not be printable strings for direct acceptance from and
    presentation to users. Tagging of flat names allows GSS-API
    callers and underlying GSS-API mechanisms to disambiguate name

Linn Standards Track [Page 12] RFC 2078 GSS-API January 1997

    types and to determine whether an associated name's type is one
    which they are capable of processing, avoiding aliasing problems
    which could result from misinterpreting a name of one type as a
    name of another type.
  1. The GSS-API Exported Name Object, a special case of flat name

designated by a reserved OID value, carries a canonicalized form

    of a name suitable for binary comparisons.
 In addition to providing means for names to be tagged with types,
 this specification defines primitives to support a level of naming
 environment independence for certain calling applications. To provide
 basic services oriented towards the requirements of callers which
 need not themselves interpret the internal syntax and semantics of
 names, GSS-API calls for name comparison (GSS_Compare_name()),
 human-readable display (GSS_Display_name()), input conversion
 (GSS_Import_name()), internal name deallocation (GSS_Release_name()),
 and internal name duplication (GSS_Duplicate_name()) functions are
 defined. (It is anticipated that these proposed GSS-API calls will be
 implemented in many end systems based on system-specific name
 manipulation primitives already extant within those end systems;
 inclusion within the GSS-API is intended to offer GSS-API callers a
 portable means to perform specific operations, supportive of
 authorization and audit requirements, on authenticated names.)
 GSS_Import_name() implementations can, where appropriate, support
 more than one printable syntax corresponding to a given namespace
 (e.g., alternative printable representations for X.500 Distinguished
 Names), allowing flexibility for their callers to select among
 alternative representations. GSS_Display_name() implementations
 output a printable syntax selected as appropriate to their
 operational environments; this selection is a local matter. Callers
 desiring portability across alternative printable syntaxes should
 refrain from implementing comparisons based on printable name forms
 and should instead use the GSS_Compare_name()  call to determine
 whether or not one internal-format name matches another.
 The GSS_Canonicalize_name() and GSS_Export_name() calls enable
 callers to acquire and process Exported Name Objects, canonicalized
 and translated in accordance with the procedures of a particular
 GSS-API mechanism.  Exported Name Objects can, in turn, be input to
 GSS_Import_name(), yielding equivalent MNs. These facilities are
 designed specifically to enable efficient storage and comparison of
 names (e.g., for use in access control lists).

Linn Standards Track [Page 13] RFC 2078 GSS-API January 1997

 The following diagram illustrates the intended dataflow among name-
 related GSS-API processing routines.
                      GSS-API library defaults
                             |
                             |
                             V                         text, for
 text -------------->  internal_name (IN) -----------> display only
       import_name()          /          display_name()
                             /
                            /
                           /
  accept_sec_context()    /
        |                /
        |               /
        |              /  canonicalize_name()
        |             /
        |            /
        |           /
        |          /
        |         /
        |        |
        V        V     <---------------------
  single mechanism        import_name()         exported name: flat
  internal_name (MN)                            binary "blob" usable
                       ---------------------->  for access control
                          export_name()

1.1.6: Channel Bindings

 The GSS-API accommodates the concept of caller-provided channel
 binding ("chan_binding") information.  Channel bindings are used to
 strengthen the quality with which peer entity authentication is
 provided during context establishment, by limiting the scope within
 which an intercepted context establishment token can be reused by an
 attacker. Specifically, they enable GSS-API callers to bind the
 establishment of a security context to relevant characteristics
 (e.g., addresses, transformed representations of encryption keys) of
 the underlying communications channel, of protection mechanisms
 applied to that communications channel, and to application-specific
 data.
 The caller initiating a security context must determine the
 appropriate channel binding values to provide as input to the
 GSS_Init_sec_context() call, and consistent values must be provided
 to GSS_Accept_sec_context() by the context's target, in order for
 both peers' GSS-API mechanisms to validate that received tokens
 possess correct channel-related characteristics. Use or non-use of

Linn Standards Track [Page 14] RFC 2078 GSS-API January 1997

 the GSS-API channel binding facility is a caller option.  GSS-API
 mechanisms can operate in an environment where NULL channel bindings
 are presented; mechanism implementors are encouraged, but not
 required, to make use of caller-provided channel binding data within
 their mechanisms. Callers should not assume that underlying
 mechanisms provide confidentiality protection for channel binding
 information.
 When non-NULL channel bindings are provided by callers, certain
 mechanisms can offer enhanced security value by interpreting the
 bindings' content (rather than simply representing those bindings, or
 integrity check values computed on them, within tokens) and will
 therefore depend on presentation of specific data in a defined
 format. To this end, agreements among mechanism implementors are
 defining conventional interpretations for the contents of channel
 binding arguments, including address specifiers (with content
 dependent on communications protocol environment) for context
 initiators and acceptors. (These conventions are being incorporated
 in GSS-API mechanism specifications and into the GSS-API C language
 bindings specification.) In order for GSS-API callers to be portable
 across multiple mechanisms and achieve the full security
 functionality which each mechanism can provide, it is strongly
 recommended that GSS-API callers provide channel bindings consistent
 with these conventions and those of the networking environment in
 which they operate.

1.2: GSS-API Features and Issues

 This section describes aspects of GSS-API operations, of the security
 services which the GSS-API provides, and provides commentary on
 design issues.

1.2.1: Status Reporting

 Each GSS-API call provides two status return values. Major_status
 values provide a mechanism-independent indication of call status
 (e.g., GSS_S_COMPLETE, GSS_S_FAILURE, GSS_S_CONTINUE_NEEDED),
 sufficient to drive normal control flow within the caller in a
 generic fashion. Table 1 summarizes the defined major_status return
 codes in tabular fashion.

Linn Standards Track [Page 15] RFC 2078 GSS-API January 1997

Table 1: GSS-API Major Status Codes

 FATAL ERROR CODES
 GSS_S_BAD_BINDINGS            channel binding mismatch
 GSS_S_BAD_MECH                unsupported mechanism requested
 GSS_S_BAD_NAME                invalid name provided
 GSS_S_BAD_NAMETYPE            name of unsupported type provided
 GSS_S_BAD_STATUS              invalid input status selector
 GSS_S_BAD_SIG                 token had invalid integrity check
 GSS_S_CONTEXT_EXPIRED         specified security context expired
 GSS_S_CREDENTIALS_EXPIRED     expired credentials detected
 GSS_S_DEFECTIVE_CREDENTIAL    defective credential detected
 GSS_S_DEFECTIVE_TOKEN         defective token detected
 GSS_S_FAILURE                 failure, unspecified at GSS-API
                                 level
 GSS_S_NO_CONTEXT              no valid security context specified
 GSS_S_NO_CRED                 no valid credentials provided
 GSS_S_BAD_QOP                 unsupported QOP value
 GSS_S_UNAUTHORIZED            operation unauthorized
 GSS_S_UNAVAILABLE             operation unavailable
 GSS_S_DUPLICATE_ELEMENT       duplicate credential element requested
 GSS_S_NAME_NOT_MN             name contains multi-mechanism elements
 INFORMATORY STATUS CODES
 GSS_S_COMPLETE                normal completion
 GSS_S_CONTINUE_NEEDED         continuation call to routine
                                required
 GSS_S_DUPLICATE_TOKEN         duplicate per-message token
                                detected
 GSS_S_OLD_TOKEN               timed-out per-message token
                                detected
 GSS_S_UNSEQ_TOKEN             reordered (early) per-message token
                                detected
 GSS_S_GAP_TOKEN               skipped predecessor token(s)
                                detected
 Minor_status provides more detailed status information which may
 include status codes specific to the underlying security mechanism.
 Minor_status values are not specified in this document.
 GSS_S_CONTINUE_NEEDED major_status returns, and optional message
 outputs, are provided in GSS_Init_sec_context() and
 GSS_Accept_sec_context()  calls so that different mechanisms'
 employment of different numbers of messages within their
 authentication sequences need not be reflected in separate code paths
 within calling applications. Instead, such cases are accommodated

Linn Standards Track [Page 16] RFC 2078 GSS-API January 1997

 with sequences of continuation calls to GSS_Init_sec_context()  and
 GSS_Accept_sec_context().  The same mechanism is used to encapsulate
 mutual authentication within the GSS-API's context initiation calls.
 For mech_types which require interactions with third-party servers in
 order to establish a security context, GSS-API context establishment
 calls may block pending completion of such third-party interactions.
 On the other hand, no GSS-API calls pend on serialized interactions
 with GSS-API peer entities.  As a result, local GSS-API status
 returns cannot reflect unpredictable or asynchronous exceptions
 occurring at remote peers, and reflection of such status information
 is a caller responsibility outside the GSS-API.

1.2.2: Per-Message Security Service Availability

 When a context is established, two flags are returned to indicate the
 set of per-message protection security services which will be
 available on the context:
    the integ_avail flag indicates whether per-message integrity and
    data origin authentication services are available
    the conf_avail flag indicates whether per-message confidentiality
    services are available, and will never be returned TRUE unless the
    integ_avail flag is also returned TRUE
    GSS-API callers desiring per-message security services should
    check the values of these flags at context establishment time, and
    must be aware that a returned FALSE value for integ_avail means
    that invocation of GSS_GetMIC()  or GSS_Wrap() primitives on the
    associated context will apply no cryptographic protection to user
    data messages.
 The GSS-API per-message integrity and data origin authentication
 services provide assurance to a receiving caller that protection was
 applied to a message by the caller's peer on the security context,
 corresponding to the entity named at context initiation.  The GSS-API
 per-message confidentiality service provides assurance to a sending
 caller that the message's content is protected from access by
 entities other than the context's named peer.

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 The GSS-API per-message protection service primitives, as the
 category name implies, are oriented to operation at the granularity
 of protocol data units. They perform cryptographic operations on the
 data units, transfer cryptographic control information in tokens,
 and, in the case of GSS_Wrap(), encapsulate the protected data unit.
 As such, these primitives are not oriented to efficient data
 protection for stream-paradigm protocols (e.g., Telnet) if
 cryptography must be applied on an octet-by-octet basis.

1.2.3: Per-Message Replay Detection and Sequencing

 Certain underlying mech_types offer support for replay detection
 and/or sequencing of messages transferred on the contexts they
 support. These optionally-selectable protection features are distinct
 from replay detection and sequencing features applied to the context
 establishment operation itself; the presence or absence of context-
 level replay or sequencing features is wholly a function of the
 underlying mech_type's capabilities, and is not selected or omitted
 as a caller option.
 The caller initiating a context provides flags (replay_det_req_flag
 and sequence_req_flag) to specify whether the use of per-message
 replay detection and sequencing features is desired on the context
 being established. The GSS-API implementation at the initiator system
 can determine whether these features are supported (and whether they
 are optionally selectable) as a function of mech_type, without need
 for bilateral negotiation with the target. When enabled, these
 features provide recipients with indicators as a result of GSS-API
 processing of incoming messages, identifying whether those messages
 were detected as duplicates or out-of-sequence. Detection of such
 events does not prevent a suspect message from being provided to a
 recipient; the appropriate course of action on a suspect message is a
 matter of caller policy.
 The semantics of the replay detection and sequencing services applied
 to received messages, as visible across the interface which the GSS-
 API provides to its clients, are as follows:
 When replay_det_state is TRUE, the possible major_status returns for
 well-formed and correctly signed messages are as follows:
    1. GSS_S_COMPLETE indicates that the message was within the window
    (of time or sequence space) allowing replay events to be detected,
    and that the message was not a replay of a previously-processed
    message within that window.

Linn Standards Track [Page 18] RFC 2078 GSS-API January 1997

    2. GSS_S_DUPLICATE_TOKEN indicates that the cryptographic
    checkvalue on the received message was correct, but that the
    message was recognized as a duplicate of a previously-processed
    message.
    3. GSS_S_OLD_TOKEN indicates that the cryptographic checkvalue on
    the received message was correct, but that the message is too old
    to be checked for duplication.
 When sequence_state is TRUE, the possible major_status returns for
 well-formed and correctly signed messages are as follows:
    1. GSS_S_COMPLETE indicates that the message was within the window
    (of time or sequence space) allowing replay events to be detected,
    that the message was not a replay of a previously-processed
    message within that window, and that no predecessor sequenced
    messages are missing relative to the last received message (if
    any) processed on the context with a correct cryptographic
    checkvalue.
    2. GSS_S_DUPLICATE_TOKEN indicates that the integrity check value
    on the received message was correct, but that the message was
    recognized as a duplicate of a previously-processed message.
    3. GSS_S_OLD_TOKEN indicates that the integrity check value on the
    received message was correct, but that the token is too old to be
    checked for duplication.
    4. GSS_S_UNSEQ_TOKEN indicates that the cryptographic checkvalue
    on the received message was correct, but that it is earlier in a
    sequenced stream than a message already processed on the context.
    [Note: Mechanisms can be architected to provide a stricter form of
    sequencing service, delivering particular messages to recipients
    only after all predecessor messages in an ordered stream have been
    delivered.  This type of support is incompatible with the GSS-API
    paradigm in which recipients receive all messages, whether in
    order or not, and provide them (one at a time, without intra-GSS-
    API message buffering) to GSS-API routines for validation.  GSS-
    API facilities provide supportive functions, aiding clients to
    achieve strict message stream integrity in an efficient manner in
    conjunction with sequencing provisions in communications
    protocols, but the GSS-API does not offer this level of message
    stream integrity service by itself.]

Linn Standards Track [Page 19] RFC 2078 GSS-API January 1997

    5. GSS_S_GAP_TOKEN indicates that the cryptographic checkvalue on
    the received message was correct, but that one or more predecessor
    sequenced messages have not been successfully processed relative
    to the last received message (if any) processed on the context
    with a correct cryptographic checkvalue.
 As the message stream integrity features (especially sequencing) may
 interfere with certain applications' intended communications
 paradigms, and since support for such features is likely to be
 resource intensive, it is highly recommended that mech_types
 supporting these features allow them to be activated selectively on
 initiator request when a context is established. A context initiator
 and target are provided with corresponding indicators
 (replay_det_state and sequence_state), signifying whether these
 features are active on a given context.
 An example mech_type supporting per-message replay detection could
 (when replay_det_state is TRUE) implement the feature as follows: The
 underlying mechanism would insert timestamps in data elements output
 by GSS_GetMIC()  and GSS_Wrap(), and would maintain (within a time-
 limited window) a cache (qualified by originator-recipient pair)
 identifying received data elements processed by GSS_VerifyMIC()  and
 GSS_Unwrap(). When this feature is active, exception status returns
 (GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN) will be provided when
 GSS_VerifyMIC()  or GSS_Unwrap() is presented with a message which is
 either a detected duplicate of a prior message or which is too old to
 validate against a cache of recently received messages.

1.2.4: Quality of Protection

 Some mech_types provide their users with fine granularity control
 over the means used to provide per-message protection, allowing
 callers to trade off security processing overhead dynamically against
 the protection requirements of particular messages. A per-message
 quality-of-protection parameter (analogous to quality-of-service, or
 QOS) selects among different QOP options supported by that mechanism.
 On context establishment for a multi-QOP mech_type, context-level
 data provides the prerequisite data for a range of protection
 qualities.
 It is expected that the majority of callers will not wish to exert
 explicit mechanism-specific QOP control and will therefore request
 selection of a default QOP. Definitions of, and choices among, non-
 default QOP values are mechanism-specific, and no ordered sequences
 of QOP values can be assumed equivalent across different mechanisms.
 Meaningful use of non-default QOP values demands that callers be
 familiar with the QOP definitions of an underlying mechanism or
 mechanisms, and is therefore a non-portable construct.  The

Linn Standards Track [Page 20] RFC 2078 GSS-API January 1997

 GSS_S_BAD_QOP major_status value is defined in order to indicate that
 a provided QOP value is unsupported for a security context, most
 likely because that value is unrecognized by the underlying
 mechanism.

1.2.5: Anonymity Support

 In certain situations or environments, an application may wish to
 authenticate a peer and/or protect communications using GSS-API per-
 message services without revealing its own identity.  For example,
 consider an application which provides read access to a research
 database, and which permits queries by arbitrary requestors.  A
 client of such a service might wish to authenticate the service, to
 establish trust in the information received from it, but might not
 wish to disclose its identity to the service for privacy reasons.
 In ordinary GSS-API usage, a context initiator's identity is made
 available to the context acceptor as part of the context
 establishment process.  To provide for anonymity support, a facility
 (input anon_req_flag to GSS_Init_sec_context()) is provided through
 which context initiators may request that their identity not be
 provided to the context acceptor.  Mechanisms are not required to
 honor this request, but a caller will be informed (via returned
 anon_state indicator from GSS_Init_sec_context()) whether or not the
 request is honored. Note that authentication as the anonymous
 principal does not necessarily imply that credentials are not
 required in order to establish a context.
 The following Object Identifier value is provided as a means to
 identify anonymous names, and can be compared against in order to
 determine, in a mechanism-independent fashion, whether a name refers
 to an anonymous principal:
 {1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
 3(gss-anonymous-name)}
 The recommended symbolic name corresponding to this definition is
 GSS_C_NT_ANONYMOUS.
 Four possible combinations of anon_state and mutual_state are
 possible, with the following results:
    anon_state == FALSE, mutual_state == FALSE: initiator
    authenticated to target.
    anon_state == FALSE, mutual_state == TRUE: initiator authenticated
    to target, target authenticated to initiator.

Linn Standards Track [Page 21] RFC 2078 GSS-API January 1997

    anon_state == TRUE, mutual_state == FALSE: initiator authenticated
    as anonymous principal to target.
    anon_state == TRUE, mutual_state == TRUE: initiator authenticated
    as anonymous principal to target, target authenticated to
    initiator.

1.2.6: Initialization

 No initialization calls (i.e., calls which must be invoked prior to
 invocation of other facilities in the interface) are defined in GSS-
 API.  As an implication of this fact, GSS-API implementations must
 themselves be self-initializing.

1.2.7: Per-Message Protection During Context Establishment

 A facility is defined in GSS-V2 to enable protection and buffering of
 data messages for later transfer while a security context's
 establishment is in GSS_S_CONTINUE_NEEDED status, to be used in cases
 where the caller side already possesses the necessary session key to
 enable this processing. Specifically, a new state Boolean, called
 prot_ready_state, is added to the set of information returned by
 GSS_Init_sec_context(), GSS_Accept_sec_context(), and
 GSS_Inquire_context().
 For context establishment calls, this state Boolean is valid and
 interpretable when the associated major_status is either
 GSS_S_CONTINUE_NEEDED, or GSS_S_COMPLETE.  Callers of GSS-API (both
 initiators and acceptors) can assume that per-message protection (via
 GSS_Wrap(), GSS_Unwrap(), GSS_GetMIC() and GSS_VerifyMIC()) is
 available and ready for use if either: prot_ready_state == TRUE, or
 major_status == GSS_S_COMPLETE, though mutual authentication (if
 requested) cannot be guaranteed until GSS_S_COMPLETE is returned.
 This achieves full, transparent backward compatibility for GSS-API V1
 callers, who need not even know of the existence of prot_ready_state,
 and who will get the expected behavior from GSS_S_COMPLETE, but who
 will not be able to use per-message protection before GSS_S_COMPLETE
 is returned.
 It is not a requirement that GSS-V2 mechanisms ever return TRUE
 prot_ready_state before completion of context establishment (indeed,
 some mechanisms will not evolve usable message protection keys,
 especially at the context acceptor, before context establishment is
 complete).  It is expected but not required that GSS-V2 mechanisms
 will return TRUE prot_ready_state upon completion of context
 establishment if they support per-message protection at all (however
 GSS-V2 applications should not assume that TRUE prot_ready_state will

Linn Standards Track [Page 22] RFC 2078 GSS-API January 1997

 always be returned together with the GSS_S_COMPLETE major_status,
 since GSS-V2 implementations may continue to support GSS-V1 mechanism
 code, which will never return TRUE prot_ready_state).
 When prot_ready_state is returned TRUE, mechanisms shall also set
 those context service indicator flags (deleg_state, mutual_state,
 replay_det_state, sequence_state, anon_state, trans_state,
 conf_avail, integ_avail) which represent facilities confirmed, at
 that time, to be available on the context being established.  In
 situations where prot_ready_state is returned before GSS_S_COMPLETE,
 it is possible that additional facilities may be confirmed and
 subsequently indicated when GSS_S_COMPLETE is returned.

1.2.8: Implementation Robustness

 This section recommends aspects of GSS-API implementation behavior in
 the interests of overall robustness.
 If a token is presented for processing on a GSS-API security context
 and that token is determined to be invalid for that context, the
 context's state should not be disrupted for purposes of processing
 subsequent valid tokens.
 Certain local conditions at a GSS-API implementation (e.g.,
 unavailability of memory) may preclude, temporarily or permanently,
 the successful processing of tokens on a GSS-API security context,
 typically generating GSS_S_FAILURE major_status returns along with
 locally-significant minor_status.  For robust operation under such
 conditions, the following recommendations are made:
    Failing calls should free any memory they allocate, so that
    callers may retry without causing further loss of resources.
    Failure of an individual call on an established context should not
    preclude subsequent calls from succeeding on the same context.
    Whenever possible, it should be possible for
    GSS_Delete_sec_context() calls to be successfully processed even
    if other calls cannot succeed, thereby enabling context-related
    resources to be released.

2: Interface Descriptions

 This section describes the GSS-API's service interface, dividing the
 set of calls offered into four groups. Credential management calls
 are related to the acquisition and release of credentials by
 principals. Context-level calls are related to the management of
 security contexts between principals. Per-message calls are related

Linn Standards Track [Page 23] RFC 2078 GSS-API January 1997

 to the protection of individual messages on established security
 contexts. Support calls provide ancillary functions useful to GSS-API
 callers. Table 2 groups and summarizes the calls in tabular fashion.

Table 2: GSS-API Calls

 CREDENTIAL MANAGEMENT
 GSS_Acquire_cred             acquire credentials for use
 GSS_Release_cred             release credentials after use
 GSS_Inquire_cred             display information about
                              credentials
 GSS_Add_cred                 construct credentials incrementally
 GSS_Inquire_cred_by_mech     display per-mechanism credential
                              information
 CONTEXT-LEVEL CALLS
 GSS_Init_sec_context         initiate outbound security context
 GSS_Accept_sec_context       accept inbound security context
 GSS_Delete_sec_context       flush context when no longer needed
 GSS_Process_context_token    process received control token on
                              context
 GSS_Context_time             indicate validity time remaining on
                                    context
 GSS_Inquire_context          display information about context
 GSS_Wrap_size_limit          determine GSS_Wrap token size limit
 GSS_Export_sec_context       transfer context to other process
 GSS_Import_sec_context       import transferred context
 PER-MESSAGE CALLS
 GSS_GetMIC                   apply integrity check, receive as
                              token separate from message
 GSS_VerifyMIC                validate integrity check token
                              along with message
 GSS_Wrap                     sign, optionally encrypt,
                              encapsulate
 GSS_Unwrap                   decapsulate, decrypt if needed,
                              validate integrity check

Linn Standards Track [Page 24] RFC 2078 GSS-API January 1997

 SUPPORT CALLS
 GSS_Display_status           translate status codes to printable
                              form
 GSS_Indicate_mechs           indicate mech_types supported on
                              local system
 GSS_Compare_name             compare two names for equality
 GSS_Display_name             translate name to printable form
 GSS_Import_name              convert printable name to
                              normalized form
 GSS_Release_name             free storage of normalized-form
                              name
 GSS_Release_buffer           free storage of printable name
 GSS_Release_OID              free storage of OID object
 GSS_Release_OID_set          free storage of OID set object
 GSS_Create_empty_OID_set     create empty OID set
 GSS_Add_OID_set_member       add member to OID set
 GSS_Test_OID_set_member      test if OID is member of OID set
 GSS_OID_to_str               display OID as string
 GSS_Str_to_OID               construct OID from string
 GSS_Inquire_names_for_mech   indicate name types supported by
                              mechanism
 GSS_Inquire_mechs_for_name   indicates mechanisms supporting name
                              type
 GSS_Canonicalize_name        translate name to per-mechanism form
 GSS_Export_name              externalize per-mechanism name
 GSS_Duplicate_name           duplicate name object

2.1: Credential management calls

 These GSS-API calls provide functions related to the management of
 credentials. Their characterization with regard to whether or not
 they may block pending exchanges with other network entities (e.g.,
 directories or authentication servers) depends in part on OS-specific
 (extra-GSS-API) issues, so is not specified in this document.
 The GSS_Acquire_cred() call is defined within the GSS-API in support
 of application portability, with a particular orientation towards
 support of portable server applications. It is recognized that (for
 certain systems and mechanisms) credentials for interactive users may
 be managed differently from credentials for server processes; in such
 environments, it is the GSS-API implementation's responsibility to
 distinguish these cases and the procedures for making this
 distinction are a local matter. The GSS_Release_cred()  call provides
 a means for callers to indicate to the GSS-API that use of a
 credentials structure is no longer required. The GSS_Inquire_cred()
 call allows callers to determine information about a credentials
 structure.  The GSS_Add_cred() call enables callers to append

Linn Standards Track [Page 25] RFC 2078 GSS-API January 1997

 elements to an existing credential structure, allowing iterative
 construction of a multi-mechanism credential. The
 GSS_Inquire_cred_by_mech() call enables callers to extract per-
 mechanism information describing a credentials structure.

2.1.1: GSS_Acquire_cred call

 Inputs:
 o  desired_name INTERNAL NAME, -NULL requests locally-determined
    default
 o  lifetime_req INTEGER,-in seconds; 0 requests default
 o  desired_mechs SET OF OBJECT IDENTIFIER,-empty set requests
    system-selected default
 o  cred_usage INTEGER -0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
    2=ACCEPT-ONLY
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_cred_handle CREDENTIAL HANDLE,
 o  actual_mechs SET OF OBJECT IDENTIFIER,
 o  lifetime_rec INTEGER -in seconds, or reserved value for
    INDEFINITE
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that requested credentials were
    successfully established, for the duration indicated in
    lifetime_rec, suitable for the usage requested in cred_usage,
    for the set of mech_types indicated in actual_mechs, and that
    those credentials can be referenced for subsequent use with
    the handle returned in output_cred_handle.
 o  GSS_S_BAD_MECH indicates that a mech_type unsupported by the
    GSS-API implementation type was requested, causing the
    credential establishment operation to fail.

Linn Standards Track [Page 26] RFC 2078 GSS-API January 1997

 o  GSS_S_BAD_NAMETYPE indicates that the provided desired_name is
    uninterpretable or of a type unsupported by the applicable
    underlying GSS-API mechanism(s), so no credentials could be
    established for the accompanying desired_name.
 o  GSS_S_BAD_NAME indicates that the provided desired_name is
    inconsistent in terms of internally-incorporated type specifier
    information, so no credentials could be established for the
    accompanying desired_name.
 o  GSS_S_FAILURE indicates that credential establishment failed
    for reasons unspecified at the GSS-API level, including lack
    of authorization to establish and use credentials associated
    with the identity named in the input desired_name argument.
 GSS_Acquire_cred()  is used to acquire credentials so that a
 principal can (as a function of the input cred_usage parameter)
 initiate and/or accept security contexts under the identity
 represented by the desired_name input argument. On successful
 completion, the returned output_cred_handle result provides a handle
 for subsequent references to the acquired credentials.  Typically,
 single-user client processes requesting that default credential
 behavior be applied for context establishment purposes will have no
 need to invoke this call.
 A caller may provide the value NULL for desired_name, signifying a
 request for credentials corresponding to a principal identity
 selected by default for the caller. The procedures used by GSS-API
 implementations to select the appropriate principal identity in
 response to such a request are local matters. It is possible that
 multiple pre-established credentials may exist for the same principal
 identity (for example, as a result of multiple user login sessions)
 when GSS_Acquire_cred() is called; the means used in such cases to
 select a specific credential are local matters.  The input
 lifetime_req argument to GSS_Acquire_cred() may provide useful
 information for local GSS-API implementations to employ in making
 this disambiguation in a manner which will best satisfy a caller's
 intent.
 The lifetime_rec result indicates the length of time for which the
 acquired credentials will be valid, as an offset from the present. A
 mechanism may return a reserved value indicating INDEFINITE if no
 constraints on credential lifetime are imposed.  A caller of
 GSS_Acquire_cred()  can request a length of time for which acquired
 credentials are to be valid (lifetime_req argument), beginning at the
 present, or can request credentials with a default validity interval.
 (Requests for postdated credentials are not supported within the
 GSS-API.) Certain mechanisms and implementations may bind in

Linn Standards Track [Page 27] RFC 2078 GSS-API January 1997

 credential validity period specifiers at a point preliminary to
 invocation of the GSS_Acquire_cred() call (e.g., in conjunction with
 user login procedures). As a result, callers requesting non-default
 values for lifetime_req must recognize that such requests cannot
 always be honored and must be prepared to accommodate the use of
 returned credentials with different lifetimes as indicated in
 lifetime_rec.
 The caller of GSS_Acquire_cred()  can explicitly specify a set of
 mech_types which are to be accommodated in the returned credentials
 (desired_mechs argument), or can request credentials for a system-
 defined default set of mech_types. Selection of the system-specified
 default set is recommended in the interests of application
 portability. The actual_mechs return value may be interrogated by the
 caller to determine the set of mechanisms with which the returned
 credentials may be used.

2.1.2: GSS_Release_cred call

 Input:
 o  cred_handle CREDENTIAL HANDLE - NULL specifies that
    the credential elements used when default credential behavior
    is requested be released.
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the credentials referenced by the
    input cred_handle were released for purposes of subsequent
    access by the caller. The effect on other processes which may
    be authorized shared access to such credentials is a local
    matter.
 o  GSS_S_NO_CRED indicates that no release operation was
    performed, either because the input cred_handle was invalid or
    because the caller lacks authorization to access the
    referenced credentials.
 o  GSS_S_FAILURE indicates that the release operation failed for
    reasons unspecified at the GSS-API level.

Linn Standards Track [Page 28] RFC 2078 GSS-API January 1997

 Provides a means for a caller to explicitly request that credentials
 be released when their use is no longer required. Note that system-
 specific credential management functions are also likely to exist,
 for example to assure that credentials shared among processes are
 properly deleted when all affected processes terminate, even if no
 explicit release requests are issued by those processes. Given the
 fact that multiple callers are not precluded from gaining authorized
 access to the same credentials, invocation of GSS_Release_cred()
 cannot be assumed to delete a particular set of credentials on a
 system-wide basis.

2.1.3: GSS_Inquire_cred call

 Input:
 o  cred_handle CREDENTIAL HANDLE -NULL specifies that the
    credential elements used when default credential behavior is
    requested are to be queried
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  cred_name INTERNAL NAME,
 o  lifetime_rec INTEGER -in seconds, or reserved value for
    INDEFINITE
 o  cred_usage INTEGER, -0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
    2=ACCEPT-ONLY
 o  mech_set SET OF OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the credentials referenced by the
    input cred_handle argument were valid, and that the output
    cred_name, lifetime_rec, and cred_usage values represent,
    respectively, the credentials' associated principal name,
    remaining lifetime, suitable usage modes, and supported
    mechanism types.
 o  GSS_S_NO_CRED indicates that no information could be returned
    about the referenced credentials, either because the input
    cred_handle was invalid or because the caller lacks
    authorization to access the referenced credentials.

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 o  GSS_S_DEFECTIVE_CREDENTIAL indicates that the referenced
    credentials are invalid.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the referenced
    credentials have expired.
 o  GSS_S_FAILURE indicates that the operation failed for
    reasons unspecified at the GSS-API level.
 The GSS_Inquire_cred() call is defined primarily for the use of those
 callers which request use of default credential behavior rather than
 acquiring credentials explicitly with GSS_Acquire_cred().  It enables
 callers to determine a credential structure's associated principal
 name, remaining validity period, usability for security context
 initiation and/or acceptance, and supported mechanisms.
 For a multi-mechanism credential, the returned "lifetime" specifier
 indicates the shortest lifetime of any of the mechanisms' elements in
 the credential (for either context initiation or acceptance
 purposes).
 GSS_Inquire_cred() should indicate INITIATE-AND-ACCEPT for
 "cred_usage" if both of the following conditions hold:
    (1) there exists in the credential an element which allows context
    initiation using some mechanism
    (2) there exists in the credential an element which allows context
    acceptance using some mechanism (allowably, but not necessarily,
    one of the same mechanism(s) qualifying for (1)).
 If condition (1) holds but not condition (2), GSS_Inquire_cred()
 should indicate INITIATE-ONLY for "cred_usage".  If condition (2)
 holds but not condition (1), GSS_Inquire_cred() should indicate
 ACCEPT-ONLY for "cred_usage".
 Callers requiring finer disambiguation among available combinations
 of lifetimes, usage modes, and mechanisms should call the
 GSS_Inquire_cred_by_mech() routine, passing that routine one of the
 mech OIDs returned by GSS_Inquire_cred().

Linn Standards Track [Page 30] RFC 2078 GSS-API January 1997

2.1.4: GSS_Add_cred call

 Inputs:
 o  input_cred_handle CREDENTIAL HANDLE - handle to credential
    structure created with prior GSS_Acquire_cred() or
    GSS_Add_cred() call, or NULL to append elements to the set
    which are applied for the caller when default credential
    behavior is specified.
 o  desired_name INTERNAL NAME - NULL requests locally-determined
    default
 o  initiator_time_req INTEGER - in seconds; 0 requests default
 o  acceptor_time_req INTEGER - in seconds; 0 requests default
 o  desired_mech OBJECT IDENTIFIER
 o  cred_usage INTEGER - 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
     2=ACCEPT-ONLY
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_cred_handle CREDENTIAL HANDLE, - NULL to request that
    credential elements be added "in place" to the credential
    structure  identified by input_cred_handle, non-NULL pointer
    to request that a new credential structure and handle be created.
 o  actual_mechs SET OF OBJECT IDENTIFIER,
 o  initiator_time_rec INTEGER - in seconds, or reserved value for
    INDEFINITE
 o  acceptor_time_rec INTEGER - in seconds, or reserved value for
    INDEFINITE
 o  cred_usage INTEGER, -0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
    2=ACCEPT-ONLY
 o  mech_set SET OF OBJECT IDENTIFIER -- full set of mechanisms
    supported by resulting credential.

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 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the credentials referenced by
    the input_cred_handle argument were valid, and that the
    resulting credential from GSS_Add_cred() is valid for the
    durations indicated in initiator_time_rec and acceptor_time_rec,
    suitable for the usage requested in cred_usage, and for the
    mechanisms indicated in actual_mechs.
 o  GSS_S_DUPLICATE_ELEMENT indicates that the input desired_mech
    specified a mechanism for which the referenced credential
    already contained a credential element with overlapping
    cred_usage and validity time specifiers.
 o  GSS_S_BAD_MECH indicates that the input desired_mech specified
    a mechanism unsupported by the GSS-API implementation, causing
    the GSS_Add_cred() operation to fail.
 o  GSS_S_BAD_NAMETYPE indicates that the provided desired_name
    is uninterpretable or of a type unsupported by the applicable
    underlying GSS-API mechanism(s), so the GSS_Add_cred() operation
    could not be performed for that name.
 o  GSS_S_BAD_NAME indicates that the provided desired_name is
    inconsistent in terms of internally-incorporated type specifier
    information, so the GSS_Add_cred() operation could not be
    performed for that name.
 o  GSS_S_NO_CRED indicates that the input_cred_handle referenced
    invalid or inaccessible credentials.
 o  GSS_S_FAILURE indicates that the operation failed for
    reasons unspecified at the GSS-API level, including lack of
    authorization to establish or use credentials representing
    the requested identity.
 GSS_Add_cred() enables callers to construct credentials iteratively
 by adding credential elements in successive operations, corresponding
 to different mechanisms.  This offers particular value in multi-
 mechanism environments, as the major_status and minor_status values
 returned on each iteration are individually visible and can therefore
 be interpreted unambiguously on a per-mechanism basis.
 The same input desired_name, or default reference, should be used on
 all GSS_Acquire_cred() and GSS_Add_cred() calls corresponding to a
 particular credential.

Linn Standards Track [Page 32] RFC 2078 GSS-API January 1997

2.1.5: GSS_Inquire_cred_by_mech call

 Inputs:
 o  cred_handle CREDENTIAL HANDLE  -- NULL specifies that the
    credential elements used when default credential behavior is
    requested are to be queried
 o  mech_type OBJECT IDENTIFIER  -- specific mechanism for
    which credentials are being queried
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  cred_name INTERNAL NAME, -- guaranteed to be MN
 o  lifetime_rec_initiate INTEGER -- in seconds, or reserved value for
    INDEFINITE
 o  lifetime_rec_accept INTEGER -- in seconds, or reserved value for
    INDEFINITE
 o  cred_usage INTEGER, -0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
    2=ACCEPT-ONLY
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the credentials referenced by the
    input cred_handle argument were valid, that the mechanism
    indicated by the input mech_type was represented with elements
    within those credentials, and that the output cred_name,
    lifetime_rec_initiate, lifetime_rec_accept, and cred_usage values
    represent, respectively, the credentials' associated principal
    name, remaining lifetimes, and suitable usage modes.
 o  GSS_S_NO_CRED indicates that no information could be returned
    about the referenced credentials, either because the input
    cred_handle was invalid or because the caller lacks
    authorization to access the referenced credentials.
 o  GSS_S_DEFECTIVE_CREDENTIAL indicates that the referenced
    credentials are invalid.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the referenced
    credentials have expired.

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 o  GSS_S_BAD_MECH indicates that the referenced credentials do not
    contain elements for the requested mechanism.
 o  GSS_S_FAILURE indicates that the operation failed for reasons
    unspecified at the GSS-API level.
 The GSS_Inquire_cred_by_mech() call enables callers in multi-
 mechanism environments to acquire specific data about available
 combinations of lifetimes, usage modes, and mechanisms within a
 credential structure.  The lifetime_rec_initiate result indicates the
 available lifetime for context initiation purposes; the
 lifetime_rec_accept result indicates the available lifetime for
 context acceptance purposes.

2.2: Context-level calls

 This group of calls is devoted to the establishment and management of
 security contexts between peers. A context's initiator calls
 GSS_Init_sec_context(),  resulting in generation of a token which the
 caller passes to the target. At the target, that token is passed to
 GSS_Accept_sec_context().  Depending on the underlying mech_type and
 specified options, additional token exchanges may be performed in the
 course of context establishment; such exchanges are accommodated by
 GSS_S_CONTINUE_NEEDED status returns from GSS_Init_sec_context()  and
 GSS_Accept_sec_context().
 Either party to an established context may invoke
 GSS_Delete_sec_context() to flush context information when a context
 is no longer required. GSS_Process_context_token()  is used to
 process received tokens carrying context-level control information.
 GSS_Context_time()  allows a caller to determine the length of time
 for which an established context will remain valid.
 GSS_Inquire_context() returns status information describing context
 characteristics. GSS_Wrap_size_limit() allows a caller to determine
 the size of a token which will be generated by a GSS_Wrap()
 operation.  GSS_Export_sec_context() and GSS_Import_sec_context()
 enable transfer of active contexts between processes on an end
 system.

2.2.1: GSS_Init_sec_context call

 Inputs:
 o  claimant_cred_handle CREDENTIAL HANDLE, -NULL specifies "use
    default"
 o  input_context_handle CONTEXT HANDLE, -0 specifies "none assigned
    yet"

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 o  targ_name INTERNAL NAME,
 o  mech_type OBJECT IDENTIFIER, -NULL parameter specifies "use
    default"
 o  deleg_req_flag BOOLEAN,
 o  mutual_req_flag BOOLEAN,
 o  replay_det_req_flag BOOLEAN,
 o  sequence_req_flag BOOLEAN,
 o  anon_req_flag BOOLEAN,
 o  lifetime_req INTEGER,-0 specifies default lifetime
 o  chan_bindings OCTET STRING,
 o  input_token OCTET STRING-NULL or token received from target
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_context_handle CONTEXT HANDLE,
 o  mech_type OBJECT IDENTIFIER, -actual mechanism always
    indicated, never NULL
 o  output_token OCTET STRING, -NULL or token to pass to context
    target
 o  deleg_state BOOLEAN,
 o  mutual_state BOOLEAN,
 o  replay_det_state BOOLEAN,
 o  sequence_state BOOLEAN,
 o  anon_state BOOLEAN,
 o  trans_state BOOLEAN,
 o  prot_ready_state BOOLEAN, -- see Section 1.2.7

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 o  conf_avail BOOLEAN,
 o  integ_avail BOOLEAN,
 o  lifetime_rec INTEGER - in seconds, or reserved value for
    INDEFINITE
 This call may block pending network interactions for those mech_types
 in which an authentication server or other network entity must be
 consulted on behalf of a context initiator in order to generate an
 output_token suitable for presentation to a specified target.
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that context-level information was
    successfully initialized, and that the returned output_token
    will provide sufficient information for the target to perform
    per-message processing on the newly-established context.
 o  GSS_S_CONTINUE_NEEDED indicates that control information in the
    returned output_token must be sent to the target, and that a
    reply must be received and passed as the input_token argument
    to a continuation call to GSS_Init_sec_context(),  before
    per-message processing can be performed in conjunction with
    this context.
 o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks
    performed on the input_token failed, preventing further
    processing from being performed based on that token.
 o  GSS_S_DEFECTIVE_CREDENTIAL indicates that consistency checks
    performed on the credential structure referenced by
    claimant_cred_handle failed, preventing further processing from
    being performed using that credential structure.
 o  GSS_S_BAD_SIG indicates that the received input_token
    contains an incorrect integrity check, so context setup cannot
    be accomplished.
 o  GSS_S_NO_CRED indicates that no context was established,
    either because the input cred_handle was invalid, because the
    referenced credentials are valid for context acceptor use
    only, or because the caller lacks authorization to access the
    referenced credentials.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the credentials
    provided through the input claimant_cred_handle argument are no
    longer valid, so context establishment cannot be completed.

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 o  GSS_S_BAD_BINDINGS indicates that a mismatch between the
    caller-provided chan_bindings and those extracted from the
    input_token was detected, signifying a security-relevant
    event and preventing context establishment. (This result will
    be returned by GSS_Init_sec_context only for contexts where
    mutual_state is TRUE.)
 o  GSS_S_OLD_TOKEN indicates that the input_token is too old to
    be checked for integrity. This is a fatal error during context
    establishment.
 o  GSS_S_DUPLICATE_TOKEN indicates that the input token has a
    correct integrity check, but is a duplicate of a token already
    processed. This is a fatal error during context establishment.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided; this major status will
    be returned only for successor calls following GSS_S_CONTINUE_
    NEEDED status returns.
 o  GSS_S_BAD_NAMETYPE indicates that the provided targ_name is
    of a type uninterpretable or unsupported by the applicable
    underlying GSS-API mechanism(s), so context establishment
    cannot be completed.
 o  GSS_S_BAD_NAME indicates that the provided targ_name is
    inconsistent in terms of internally-incorporated type specifier
    information, so context establishment cannot be accomplished.
 o  GSS_S_BAD_MECH indicates receipt of a context establishment token
    or of a caller request specifying a mechanism unsupported by
    the local system or with the caller's active credentials
 o  GSS_S_FAILURE indicates that context setup could not be
    accomplished for reasons unspecified at the GSS-API level, and
    that no interface-defined recovery action is available.
 This routine is used by a context initiator, and ordinarily emits one
 (or, for the case of a multi-step exchange, more than one)
 output_token suitable for use by the target within the selected
 mech_type's protocol. Using information in the credentials structure
 referenced by claimant_cred_handle, GSS_Init_sec_context()
 initializes the data structures required to establish a security
 context with target targ_name. The targ_name may be any valid
 INTERNAL NAME; it need not be an MN. The claimant_cred_handle must
 correspond to the same valid credentials structure on the initial
 call to GSS_Init_sec_context()  and on any successor calls resulting
 from GSS_S_CONTINUE_NEEDED status returns; different protocol

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 sequences modeled by the GSS_S_CONTINUE_NEEDED facility will require
 access to credentials at different points in the context
 establishment sequence.
 The input_context_handle argument is 0, specifying "not yet
 assigned", on the first GSS_Init_sec_context()  call relating to a
 given context. If successful (i.e., if accompanied by major_status
 GSS_S_COMPLETE or GSS_S_CONTINUE_NEEDED), and only if successful, the
 initial GSS_Init_sec_context() call returns a non-zero
 output_context_handle for use in future references to this context.
 Once a non-zero output_context_handle has been returned, GSS-API
 callers should call GSS_Delete_sec_context() to release context-
 related resources if errors occur in later phases of context
 establishment, or when an established context is no longer required.
 When continuation attempts to GSS_Init_sec_context() are needed to
 perform context establishment, the previously-returned non-zero
 handle value is entered into the input_context_handle argument and
 will be echoed in the returned output_context_handle argument. On
 such continuation attempts (and only on continuation attempts) the
 input_token value is used, to provide the token returned from the
 context's target.
 The chan_bindings argument is used by the caller to provide
 information binding the security context to security-related
 characteristics (e.g., addresses, cryptographic keys) of the
 underlying communications channel. See Section 1.1.6 of this document
 for more discussion of this argument's usage.
 The input_token argument contains a message received from the target,
 and is significant only on a call to GSS_Init_sec_context()  which
 follows a previous return indicating GSS_S_CONTINUE_NEEDED
 major_status.
 It is the caller's responsibility to establish a communications path
 to the target, and to transmit any returned output_token (independent
 of the accompanying returned major_status value) to the target over
 that path. The output_token can, however, be transmitted along with
 the first application-provided input message to be processed by
 GSS_GetMIC() or GSS_Wrap() in conjunction with a successfully-
 established context.
 The initiator may request various context-level functions through
 input flags: the deleg_req_flag requests delegation of access rights,
 the mutual_req_flag requests mutual authentication, the
 replay_det_req_flag requests that replay detection features be
 applied to messages transferred on the established context, and the
 sequence_req_flag requests that sequencing be enforced. (See Section

Linn Standards Track [Page 38] RFC 2078 GSS-API January 1997

 1.2.3 for more information on replay detection and sequencing
 features.)  The anon_req_flag requests that the initiator's identity
 not be transferred within tokens to be sent to the acceptor.
 Not all of the optionally-requestable features will be available in
 all underlying mech_types. The corresponding return state values
 deleg_state, mutual_state, replay_det_state, and sequence_state
 indicate, as a function of mech_type processing capabilities and
 initiator-provided input flags, the set of features which will be
 active on the context.  The returned trans_state value indicates
 whether the context is transferable to other processes through use of
 GSS_Export_sec_context().  These state indicators' values are
 undefined unless either the routine's major_status indicates
 GSS_S_COMPLETE, or TRUE prot_ready_state is returned along with
 GSS_S_CONTINUE_NEEDED major_status; for the latter case, it is
 possible that additional features, not confirmed or indicated along
 with TRUE prot_ready_state, will be confirmed and indicated when
 GSS_S_COMPLETE is subsequently returned.
 The returned anon_state and prot_ready_state values are significant
 for both GSS_S_COMPLETE and GSS_S_CONTINUE_NEEDED major_status
 returns from GSS_Init_sec_context().  When anon_state is returned
 TRUE, this indicates that neither the current token nor its
 predecessors delivers or has delivered the initiator's identity.
 Callers wishing to perform context establishment only if anonymity
 support is provided should transfer a returned token from
 GSS_Init_sec_context() to the peer only if it is accompanied by a
 TRUE anon_state indicator.  When prot_ready_state is returned TRUE in
 conjunction with GSS_S_CONTINUE_NEEDED major_status, this indicates
 that per-message protection operations may be applied on the context:
 see Section 1.2.7 for further discussion of this facility.
 Failure to provide the precise set of features requested by the
 caller does not cause context establishment to fail; it is the
 caller's prerogative to delete the context if the feature set
 provided is unsuitable for the caller's use.
 The returned mech_type value indicates the specific mechanism
 employed on the context, is valid only along with major_status
 GSS_S_COMPLETE, and will never indicate the value for "default".
 Note that, for the case of certain mechanisms which themselves
 perform negotiation, the returned mech_type result may indicate
 selection of a mechanism identified by an OID different than that
 passed in the input mech_type argument.
 The conf_avail return value indicates whether the context supports
 per-message confidentiality services, and so informs the caller
 whether or not a request for encryption through the conf_req_flag

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 input to GSS_Wrap()  can be honored. In similar fashion, the
 integ_avail return value indicates whether per-message integrity
 services are available (through either GSS_GetMIC() or GSS_Wrap()) on
 the established context. These state indicators' values are undefined
 unless either the routine's major_status indicates GSS_S_COMPLETE, or
 TRUE prot_ready_state is returned along with GSS_S_CONTINUE_NEEDED
 major_status.
 The lifetime_req input specifies a desired upper bound for the
 lifetime of the context to be established, with a value of 0 used to
 request a default lifetime. The lifetime_rec return value indicates
 the length of time for which the context will be valid, expressed as
 an offset from the present; depending on mechanism capabilities,
 credential lifetimes, and local policy, it may not correspond to the
 value requested in lifetime_req.  If no constraints on context
 lifetime are imposed, this may be indicated by returning a reserved
 value representing INDEFINITE lifetime_req. The value of lifetime_rec
 is undefined unless the routine's major_status indicates
 GSS_S_COMPLETE.
 If the mutual_state is TRUE, this fact will be reflected within the
 output_token. A call to GSS_Accept_sec_context()  at the target in
 conjunction with such a context will return a token, to be processed
 by a continuation call to GSS_Init_sec_context(),  in order to
 achieve mutual authentication.

2.2.2: GSS_Accept_sec_context call

 Inputs:
 o  acceptor_cred_handle CREDENTIAL HANDLE, -- NULL specifies
    "use default"
 o  input_context_handle CONTEXT HANDLE, -- 0 specifies
    "not yet assigned"
 o  chan_bindings OCTET STRING,
 o  input_token OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  src_name INTERNAL NAME, -- guaranteed to be MN

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 o  mech_type OBJECT IDENTIFIER,
 o  output_context_handle CONTEXT HANDLE,
 o  deleg_state BOOLEAN,
 o  mutual_state BOOLEAN,
 o  replay_det_state BOOLEAN,
 o  sequence_state BOOLEAN,
 o  anon_state BOOLEAN,
 o  trans_state BOOLEAN,
 o  prot_ready_state BOOLEAN, -- see Section 1.2.7 for discussion
 o  conf_avail BOOLEAN,
 o  integ_avail BOOLEAN,
 o  lifetime_rec INTEGER, - in seconds, or reserved value for
    INDEFINITE
 o  delegated_cred_handle CREDENTIAL HANDLE,
 o  output_token OCTET STRING -NULL or token to pass to context
    initiator
 This call may block pending network interactions for those mech_types
 in which a directory service or other network entity must be
 consulted on behalf of a context acceptor in order to validate a
 received input_token.
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that context-level data structures
    were successfully initialized, and that per-message processing
    can now be performed in conjunction with this context.
 o  GSS_S_CONTINUE_NEEDED indicates that control information in the
    returned output_token must be sent to the initiator, and that
    a response must be received and passed as the input_token
    argument to a continuation call to GSS_Accept_sec_context(),
    before per-message processing can be performed in conjunction
    with this context.

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 o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
    on the input_token failed, preventing further processing from
    being performed based on that token.
 o  GSS_S_DEFECTIVE_CREDENTIAL indicates that consistency checks
    performed on the credential structure referenced by
    acceptor_cred_handle failed, preventing further processing from
    being performed using that credential structure.
 o  GSS_S_BAD_SIG indicates that the received input_token contains
    an incorrect integrity check, so context setup cannot be
    accomplished.
 o  GSS_S_DUPLICATE_TOKEN indicates that the integrity check on the
    received input_token was correct, but that the input_token
    was recognized as a duplicate of an input_token already
    processed. No new context is established.
 o  GSS_S_OLD_TOKEN indicates that the integrity check on the received
    input_token was correct, but that the input_token is too old
    to be checked for duplication against previously-processed
    input_tokens. No new context is established.
 o  GSS_S_NO_CRED indicates that no context was established, either
    because the input cred_handle was invalid, because the
    referenced credentials are valid for context initiator use
    only, or because the caller lacks authorization to access the
    referenced credentials.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the credentials provided
    through the input acceptor_cred_handle argument are no
    longer valid, so context establishment cannot be completed.
 o  GSS_S_BAD_BINDINGS indicates that a mismatch between the
    caller-provided chan_bindings and those extracted from the
    input_token was detected, signifying a security-relevant
    event and preventing context establishment.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided; this major status will
    be returned only for successor calls following GSS_S_CONTINUE_
    NEEDED status returns.
 o  GSS_S_BAD_MECH indicates receipt of a context establishment token
    specifying a mechanism unsupported by the local system or with
    the caller's active credentials.

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 o  GSS_S_FAILURE indicates that context setup could not be
    accomplished for reasons unspecified at the GSS-API level, and
    that no interface-defined recovery action is available.
 The GSS_Accept_sec_context()  routine is used by a context target.
 Using information in the credentials structure referenced by the
 input acceptor_cred_handle, it verifies the incoming input_token and
 (following the successful completion of a context establishment
 sequence) returns the authenticated src_name and the mech_type used.
 The returned src_name is guaranteed to be an MN, processed by the
 mechanism under which the context was established. The
 acceptor_cred_handle must correspond to the same valid credentials
 structure on the initial call to GSS_Accept_sec_context() and on any
 successor calls resulting from GSS_S_CONTINUE_NEEDED status returns;
 different protocol sequences modeled by the GSS_S_CONTINUE_NEEDED
 mechanism will require access to credentials at different points in
 the context establishment sequence.
 The input_context_handle argument is 0, specifying "not yet
 assigned", on the first GSS_Accept_sec_context()  call relating to a
 given context.  If successful (i.e., if accompanied by major_status
 GSS_S_COMPLETE or GSS_S_CONTINUE_NEEDED), and only if successful, the
 initial GSS_Accept_sec_context() call returns a non-zero
 output_context_handle for use in future references to this context.
 Once a non-zero output_context_handle has been returned, GSS-API
 callers should call GSS_Delete_sec_context() to release context-
 related resources if errors occur in later phases of context
 establishment, or when an established context is no longer required.
 The chan_bindings argument is used by the caller to provide
 information binding the security context to security-related
 characteristics (e.g., addresses, cryptographic keys) of the
 underlying communications channel. See Section 1.1.6 of this document
 for more discussion of this argument's usage.
 The returned state results (deleg_state, mutual_state,
 replay_det_state, sequence_state, anon_state, trans_state, and
 prot_ready_state) reflect the same information as described for
 GSS_Init_sec_context(), and their values are significant under the
 same return state conditions.

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 The conf_avail return value indicates whether the context supports
 per-message confidentiality services, and so informs the caller
 whether or not a request for encryption through the conf_req_flag
 input to GSS_Wrap()  can be honored. In similar fashion, the
 integ_avail return value indicates whether per-message integrity
 services are available (through either GSS_GetMIC()  or GSS_Wrap())
 on the established context.  These values are significant under the
 same return state conditions as described under
 GSS_Init_sec_context().
 The lifetime_rec return value is significant only in conjunction with
 GSS_S_COMPLETE major_status, and indicates the length of time for
 which the context will be valid, expressed as an offset from the
 present.
 The mech_type return value indicates the specific mechanism employed
 on the context, is valid only along with major_status GSS_S_COMPLETE,
 and will never indicate the value for "default".
 The delegated_cred_handle result is significant only when deleg_state
 is TRUE, and provides a means for the target to reference the
 delegated credentials. The output_token result, when non-NULL,
 provides a context-level token to be returned to the context
 initiator to continue a multi-step context establishment sequence. As
 noted with GSS_Init_sec_context(),  any returned token should be
 transferred to the context's peer (in this case, the context
 initiator), independent of the value of the accompanying returned
 major_status.
 Note: A target must be able to distinguish a context-level
 input_token, which is passed to GSS_Accept_sec_context(),  from the
 per-message data elements passed to GSS_VerifyMIC()  or GSS_Unwrap().
 These data elements may arrive in a single application message, and
 GSS_Accept_sec_context()  must be performed before per-message
 processing can be performed successfully.

2.2.3: GSS_Delete_sec_context call

 Input:
 o  context_handle CONTEXT HANDLE
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,

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 o  output_context_token OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the context was recognized, and that
    relevant context-specific information was flushed.  If the caller
    provides a non-null buffer to receive an output_context_token, and
    the mechanism returns a non-NULL token into that buffer, the
    returned output_context_token is ready for transfer to the
    context's peer.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided, so no deletion was
    performed.
 o  GSS_S_FAILURE indicates that the context is recognized, but
    that the GSS_Delete_sec_context()  operation could not be
    performed for reasons unspecified at the GSS-API level.
 This call may block pending network interactions for mech_types in
 which active notification must be made to a central server when a
 security context is to be deleted.
 This call can be made by either peer in a security context, to flush
 context-specific information.  If a non-null output_context_token
 parameter is provided by the caller, an output_context_token may be
 returned to the caller.  If an output_context_token is provided to
 the caller, it can be passed to the context's peer to inform the
 peer's GSS-API implementation that the peer's corresponding context
 information can also be flushed. (Once a context is established, the
 peers involved are expected to retain cached credential and context-
 related information until the information's expiration time is
 reached or until a GSS_Delete_sec_context() call is made.)
 The facility for context_token usage to signal context deletion is
 retained for compatibility with GSS-API Version 1.  For current
 usage, it is recommended that both peers to a context invoke
 GSS_Delete_sec_context() independently, passing a null
 output_context_token buffer to indicate that no context_token is
 required.  Implementations of GSS_Delete_sec_context() should delete
 relevant locally-stored context information.
 Attempts to perform per-message processing on a deleted context will
 result in error returns.

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2.2.4: GSS_Process_context_token call

 Inputs:
 o  context_handle CONTEXT HANDLE,
 o  input_context_token OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the input_context_token was
    successfully processed in conjunction with the context
    referenced by context_handle.
 o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks
    performed on the received context_token failed, preventing
    further processing from being performed with that token.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided.
 o  GSS_S_FAILURE indicates that the context is recognized, but
    that the GSS_Process_context_token()  operation could not be
    performed for reasons unspecified at the GSS-API level.
 This call is used to process context_tokens received from a peer once
 a context has been established, with corresponding impact on
 context-level state information. One use for this facility is
 processing of the context_tokens generated by
 GSS_Delete_sec_context();  GSS_Process_context_token() will not block
 pending network interactions for that purpose. Another use is to
 process tokens indicating remote-peer context establishment failures
 after the point where the local GSS-API implementation has already
 indicated GSS_S_COMPLETE status.

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2.2.5: GSS_Context_time call

 Input:
 o  context_handle CONTEXT HANDLE,
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  lifetime_rec INTEGER - in seconds, or reserved value for
    INDEFINITE
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the referenced context is valid,
    and will remain valid for the amount of time indicated in
    lifetime_rec.
 o  GSS_S_CONTEXT_EXPIRED indicates that data items related to the
    referenced context have expired.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the context is
    recognized, but that its associated credentials have expired.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided.
 o  GSS_S_FAILURE indicates that the requested operation failed for
     reasons unspecified at the GSS-API level.
 This call is used to determine the amount of time for which a
 currently established context will remain valid.

2.2.6: GSS_Inquire_context call

 Input:
 o  context_handle CONTEXT HANDLE,
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,

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 o  src_name INTERNAL NAME,  -- name of context initiator,
                             -- guaranteed to be MN
 o  targ_name INTERNAL NAME,  -- name of context target,
                              -- guaranteed to be MN
 o  lifetime_rec INTEGER -- in seconds, or reserved value for
    INDEFINITE,
 o  mech_type OBJECT IDENTIFIER, -- the mechanism supporting this
    security context
 o  deleg_state BOOLEAN,
 o  mutual_state BOOLEAN,
 o  replay_det_state BOOLEAN,
 o  sequence_state BOOLEAN,
 o  anon_state BOOLEAN,
 o  trans_state BOOLEAN,
 o  prot_ready_state BOOLEAN,
 o  conf_avail BOOLEAN,
 o  integ_avail BOOLEAN,
 o  locally_initiated BOOLEAN, -- TRUE if initiator, FALSE if acceptor
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the referenced context is valid
    and that src_name, targ_name, lifetime_rec, mech_type, deleg_state,
    mutual_state, replay_det_state, sequence_state, anon_state,
    trans_state, prot_ready_state, conf_avail, integ_avail, and
    locally_initiated return values describe the corresponding
    characteristics of the context.
 o  GSS_S_CONTEXT_EXPIRED indicates that the provided input
    context_handle is recognized, but that the referenced context
    has expired.  Return values other than major_status and
    minor_status are undefined.

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 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided. Return values other than
    major_status and minor_status are undefined.
 o  GSS_S_FAILURE indicates that the requested operation failed for
   reasons unspecified at the GSS-API level. Return values other than
       major_status and minor_status are undefined.
 This call is used to extract information describing characteristics
 of a security context.

2.2.7: GSS_Wrap_size_limit call

 Inputs:
 o  context_handle CONTEXT HANDLE,
 o  qop INTEGER,
 o  output_size INTEGER
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  max_input_size INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates a successful token size determination:
 an input message with a length in octets equal to the
 returned max_input_size value will, when passed to GSS_Wrap()
 for processing on the context identified by the context_handle
 parameter and with the quality of protection specifier provided
 in the qop parameter, yield an output token no larger than the
 value of the provided output_size parameter.
 o  GSS_S_CONTEXT_EXPIRED indicates that the provided input
 context_handle is recognized, but that the referenced context
 has expired.  Return values other than major_status and
 minor_status are undefined.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
 for the input context_handle provided. Return values other than
 major_status and minor_status are undefined.

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 o  GSS_S_BAD_QOP indicates that the provided QOP value is not
 recognized or supported for the context.
 o  GSS_S_FAILURE indicates that the requested operation failed for
 reasons unspecified at the GSS-API level. Return values other than
 major_status and minor_status are undefined.
 This call is used to determine the largest input datum which may be
 passed to GSS_Wrap() without yielding an output token larger than a
 caller-specified value.

2.2.8: GSS_Export_sec_context call

 Inputs:
 o  context_handle CONTEXT HANDLE
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  interprocess_token OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the referenced context has been
 successfully exported to a representation in the interprocess_token,
 and is no longer available for use by the caller.
 o  GSS_S_UNAVAILABLE indicates that the context export facility
 is not available for use on the referenced context.  (This status
 should occur only for contexts for which the trans_state value is
 FALSE.) Return values other than major_status and minor_status are
 undefined.
 o GSS_S_CONTEXT_EXPIRED indicates that the provided input
 context_handle is recognized, but that the referenced context has
 expired.  Return values other than major_status and minor_status are
 undefined.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
 for the input context_handle provided. Return values other than
 major_status and minor_status are undefined.

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 o  GSS_S_FAILURE indicates that the requested operation failed for
 reasons unspecified at the GSS-API level. Return values other than
 major_status and minor_status are undefined.
 This call generates an interprocess token for transfer to another
 process within an end system, in order to transfer control of a
 security context to that process.  The recipient of the interprocess
 token will call GSS_Import_sec_context() to accept the transfer.  The
 GSS_Export_sec_context() operation is defined for use only with
 security contexts which are fully and successfully established (i.e.,
 those for which GSS_Init_sec_context() and GSS_Accept_sec_context()
 have returned GSS_S_COMPLETE major_status).
 To ensure portability, a caller of GSS_Export_sec_context() must not
 assume that a context may continue to be used once it has been
 exported; following export, the context referenced by the
 context_handle cannot be assumed to remain valid.  Further, portable
 callers must not assume that a given interprocess token can be
 imported by GSS_Import_sec_context() more than once, thereby creating
 multiple instantiations of a single context.  GSS-API implementations
 may detect and reject attempted multiple imports, but are not
 required to do so.
 The internal representation contained within the interprocess token
 is an implementation-defined local matter.  Interprocess tokens
 cannot be assumed to be transferable across different GSS-API
 implementations.
 It is recommended that GSS-API implementations adopt policies suited
 to their operational environments in order to define the set of
 processes eligible to import a context, but specific constraints in
 this area are local matters.  Candidate examples include transfers
 between processes operating on behalf of the same user identity, or
 processes comprising a common job.  However, it may be impossible to
 enforce such policies in some implementations.
 In support of the above goals, implementations may protect the
 transferred context data by using cryptography to protect data within
 the interprocess token, or by using interprocess tokens as a means to
 reference local interprocess communication facilities (protected by
 other means) rather than storing the context data directly within the
 tokens.
 Transfer of an open context may, for certain mechanisms and
 implementations, reveal data about the credential which was used to
 establish the context.  Callers should, therefore, be cautious about
 the trustworthiness of processes to which they transfer contexts.
 Although the GSS-API implementation may provide its own set of

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 protections over the exported context, the caller is responsible for
 protecting the interprocess token from disclosure, and for taking
 care that the context is transferred to an appropriate destination
 process.

2.2.9: GSS_Import_sec_context call

 Inputs:
 o  interprocess_token OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  context_handle CONTEXT HANDLE
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the context represented by the
 input interprocess_token has been successfully transferred to
 the caller, and is available for future use via the output
 context_handle.
 o  GSS_S_CONTEXT_EXPIRED indicates that the context represented by
 the input interprocess_token has expired. Return values other
 than major_status and minor_status are undefined.
 o  GSS_S_NO_CONTEXT indicates that the context represented by the
 input interprocess_token was invalid. Return values other than
 major_status and minor_status are undefined.
 o  GSS_S_DEFECTIVE_TOKEN indicates that the input interprocess_token
 was defective.  Return values other than major_status and
 minor_status are undefined.
 o  GSS_S_UNAVAILABLE indicates that the context import facility
 is not available for use on the referenced context.  Return values
 other than major_status and minor_status are undefined.
 o  GSS_S_UNAUTHORIZED indicates that the context represented by
 the input interprocess_token is unauthorized for transfer to the
 caller. Return values other than major_status and minor_status
 are undefined.

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 o  GSS_S_FAILURE indicates that the requested operation failed for
 reasons unspecified at the GSS-API level. Return values other than
 major_status and minor_status are undefined.
 This call processes an interprocess token generated by
 GSS_Export_sec_context(), making the transferred context available
 for use by the caller.  After a successful GSS_Import_sec_context()
 operation, the imported context is available for use by the importing
 process.
 For further discussion of the security and authorization issues
 regarding this call, please see the discussion in Section 2.2.8.

2.3: Per-message calls

 This group of calls is used to perform per-message protection
 processing on an established security context. None of these calls
 block pending network interactions. These calls may be invoked by a
 context's initiator or by the context's target.  The four members of
 this group should be considered as two pairs; the output from
 GSS_GetMIC()  is properly input to GSS_VerifyMIC(),  and the output
 from GSS_Wrap() is properly input to GSS_Unwrap().
 GSS_GetMIC() and GSS_VerifyMIC() support data origin authentication
 and data integrity services. When GSS_GetMIC()  is invoked on an
 input message, it yields a per-message token containing data items
 which allow underlying mechanisms to provide the specified security
 services. The original message, along with the generated per-message
 token, is passed to the remote peer; these two data elements are
 processed by GSS_VerifyMIC(),  which validates the message in
 conjunction with the separate token.
 GSS_Wrap() and GSS_Unwrap() support caller-requested confidentiality
 in addition to the data origin authentication and data integrity
 services offered by GSS_GetMIC()  and GSS_VerifyMIC(). GSS_Wrap()
 outputs a single data element, encapsulating optionally enciphered
 user data as well as associated token data items.  The data element
 output from GSS_Wrap()  is passed to the remote peer and processed by
 GSS_Unwrap()  at that system. GSS_Unwrap() combines decipherment (as
 required) with validation of data items related to authentication and
 integrity.

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2.3.1: GSS_GetMIC call

 Note: This call is functionally equivalent to the GSS_Sign call as
 defined in previous versions of this specification. In the interests
 of backward compatibility, it is recommended that implementations
 support this function under both names for the present; future
 references to this function as GSS_Sign are deprecated.
 Inputs:
 o  context_handle CONTEXT HANDLE,
 o  qop_req INTEGER,-0 specifies default QOP
 o  message OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  per_msg_token OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that an integrity check, suitable for an
    established security context, was successfully applied and
    that the message and corresponding per_msg_token are ready
    for transmission.
 o  GSS_S_CONTEXT_EXPIRED indicates that context-related data
    items have expired, so that the requested operation cannot be
    performed.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the context is recognized,
    but that its associated credentials have expired, so
    that the requested operation cannot be performed.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided.
 o  GSS_S_BAD_QOP indicates that the provided QOP value is not
    recognized or supported for the context.
 o  GSS_S_FAILURE indicates that the context is recognized, but
    that the requested operation could not be performed for
    reasons unspecified at the GSS-API level.

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 Using the security context referenced by context_handle, apply an
 integrity check to the input message (along with timestamps and/or
 other data included in support of mech_type-specific mechanisms) and
 return the result in per_msg_token. The qop_req parameter,
 interpretation of which is discussed in Section 1.2.4, allows
 quality-of-protection control. The caller passes the message and the
 per_msg_token to the target.
 The GSS_GetMIC()  function completes before the message and
 per_msg_token is sent to the peer; successful application of
 GSS_GetMIC()  does not guarantee that a corresponding GSS_VerifyMIC()
 has been (or can necessarily be) performed successfully when the
 message arrives at the destination.
 Mechanisms which do not support per-message protection services
 should return GSS_S_FAILURE if this routine is called.

2.3.2: GSS_VerifyMIC call

 Note: This call is functionally equivalent to the GSS_Verify call as
 defined in previous versions of this specification. In the interests
 of backward compatibility, it is recommended that implementations
 support this function under both names for the present; future
 references to this function as GSS_Verify are deprecated.
 Inputs:
 o  context_handle CONTEXT HANDLE,
 o  message OCTET STRING,
 o  per_msg_token OCTET STRING
 Outputs:
 o  qop_state INTEGER,
 o  major_status INTEGER,
 o  minor_status INTEGER,
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the message was successfully
    verified.

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 o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
    on the received per_msg_token failed, preventing
    further processing from being performed with that token.
 o  GSS_S_BAD_SIG indicates that the received per_msg_token contains
    an incorrect integrity check for the message.
 o  GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN, GSS_S_UNSEQ_TOKEN,
    and GSS_S_GAP_TOKEN values appear in conjunction with the
    optional per-message replay detection features described
    in Section 1.2.3; their semantics are described in that section.
 o  GSS_S_CONTEXT_EXPIRED indicates that context-related data
    items have expired, so that the requested operation cannot be
    performed.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the context is
 recognized,
    but that its associated credentials have expired, so
    that the requested operation cannot be performed.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided.
 o  GSS_S_FAILURE indicates that the context is recognized, but
    that the GSS_VerifyMIC() operation could not be performed for
    reasons unspecified at the GSS-API level.
 Using the security context referenced by context_handle, verify that
 the input per_msg_token contains an appropriate integrity check for
 the input message, and apply any active replay detection or
 sequencing features. Return an indication of the quality-of-
 protection applied to the processed message in the qop_state result.
 Since the GSS_VerifyMIC() routine never provides a confidentiality
 service, its implementations should not return non-zero values in the
 confidentiality fields of the output qop_state.
 Mechanisms which do not support per-message protection services
 should return GSS_S_FAILURE if this routine is called.

2.3.3: GSS_Wrap call

 Note: This call is functionally equivalent to the GSS_Seal call as
 defined in previous versions of this specification. In the interests
 of backward compatibility, it is recommended that implementations
 support this function under both names for the present; future
 references to this function as GSS_Seal are deprecated.

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 Inputs:
 o  context_handle CONTEXT HANDLE,
 o  conf_req_flag BOOLEAN,
 o  qop_req INTEGER,-0 specifies default QOP
 o  input_message OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  conf_state BOOLEAN,
 o  output_message OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the input_message was successfully
    processed and that the output_message is ready for
    transmission.
 o  GSS_S_CONTEXT_EXPIRED indicates that context-related data
    items have expired, so that the requested operation cannot be
    performed.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the context is
 recognized,
    but that its associated credentials have expired, so
    that the requested operation cannot be performed.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided.
 o  GSS_S_BAD_QOP indicates that the provided QOP value is not
    recognized or supported for the context.
 o  GSS_S_FAILURE indicates that the context is recognized, but
    that the GSS_Wrap()  operation could not be performed for
    reasons unspecified at the GSS-API level.
 Performs the data origin authentication and data integrity functions
 of GSS_GetMIC().  If the input conf_req_flag is TRUE, requests that
 confidentiality be applied to the input_message.  Confidentiality may

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 not be supported in all mech_types or by all implementations; the
 returned conf_state flag indicates whether confidentiality was
 provided for the input_message. The qop_req parameter, interpretation
 of which is discussed in Section 1.2.4, allows quality-of-protection
 control.
 In all cases, the GSS_Wrap()  call yields a single output_message
 data element containing (optionally enciphered) user data as well as
 control information.
 Mechanisms which do not support per-message protection services
 should return GSS_S_FAILURE if this routine is called.

2.3.4: GSS_Unwrap call

 Note: This call is functionally equivalent to the GSS_Unseal call as
 defined in previous versions of this specification. In the interests
 of backward compatibility, it is recommended that implementations
 support this function under both names for the present; future
 references to this function as GSS_Unseal are deprecated.
 Inputs:
 o  context_handle CONTEXT HANDLE,
 o  input_message OCTET STRING
 Outputs:
 o  conf_state BOOLEAN,
 o  qop_state INTEGER,
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_message OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the input_message was
    successfully processed and that the resulting output_message is
    available.
 o  GSS_S_DEFECTIVE_TOKEN indicates that consistency checks performed
    on the per_msg_token extracted from the input_message
    failed, preventing further processing from being performed.

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 o  GSS_S_BAD_SIG indicates that an incorrect integrity check was
 detected
    for the message.
 o  GSS_S_DUPLICATE_TOKEN, GSS_S_OLD_TOKEN, GSS_S_UNSEQ_TOKEN,
    and GSS_S_GAP_TOKEN values appear in conjunction with the
    optional per-message replay detection features described
    in Section 1.2.3; their semantics are described in that section.
 o  GSS_S_CONTEXT_EXPIRED indicates that context-related data
    items have expired, so that the requested operation cannot be
    performed.
 o  GSS_S_CREDENTIALS_EXPIRED indicates that the context is
 recognized,
    but that its associated credentials have expired, so
    that the requested operation cannot be performed.
 o  GSS_S_NO_CONTEXT indicates that no valid context was recognized
    for the input context_handle provided.
 o  GSS_S_FAILURE indicates that the context is recognized, but
    that the GSS_Unwrap()  operation could not be performed for
    reasons unspecified at the GSS-API level.
 Processes a data element generated (and optionally enciphered) by
 GSS_Wrap(),  provided as input_message. The returned conf_state value
 indicates whether confidentiality was applied to the input_message.
 If conf_state is TRUE, GSS_Unwrap()  deciphers the input_message.
 Returns an indication of the quality-of-protection applied to the
 processed message in the qop_state result. GSS_Wrap()  performs the
 data integrity and data origin authentication checking functions of
 GSS_VerifyMIC()  on the plaintext data. Plaintext data is returned in
 output_message.
 Mechanisms which do not support per-message protection services
 should return GSS_S_FAILURE if this routine is called.

2.4: Support calls

 This group of calls provides support functions useful to GSS-API
 callers, independent of the state of established contexts. Their
 characterization with regard to blocking or non-blocking status in
 terms of network interactions is unspecified.

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2.4.1: GSS_Display_status call

 Inputs:
 o  status_value INTEGER,-GSS-API major_status or minor_status
    return value
 o  status_type INTEGER,-1 if major_status, 2 if minor_status
 o  mech_type OBJECT IDENTIFIER-mech_type to be used for minor_
    status translation
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  status_string_set SET OF OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a valid printable status
    representation (possibly representing more than one status event
    encoded within the status_value) is available in the returned
    status_string_set.
 o  GSS_S_BAD_MECH indicates that translation in accordance with an
    unsupported mech_type was requested, so translation could not
    be performed.
 o  GSS_S_BAD_STATUS indicates that the input status_value was
    invalid, or that the input status_type carried a value other
    than 1 or 2, so translation could not be performed.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Provides a means for callers to translate GSS-API-returned major and
 minor status codes into printable string representations.

2.4.2: GSS_Indicate_mechs call

 Input:
 o  (none)

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 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  mech_set SET OF OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a set of available mechanisms has
    been returned in mech_set.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to determine the set of mechanism types available on
 the local system. This call is intended for support of specialized
 callers who need to request non-default mech_type sets from
 GSS_Acquire_cred(),  and should not be needed by other callers.

2.4.3: GSS_Compare_name call

 Inputs:
 o  name1 INTERNAL NAME,
 o  name2 INTERNAL NAME
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  name_equal BOOLEAN
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that name1 and name2 were comparable,
    and that the name_equal result indicates whether name1 and
    name2 represent the same entity.
 o  GSS_S_BAD_NAMETYPE indicates that one or both of name1 and
    name2 contained internal type specifiers uninterpretable
    by the applicable underlying GSS-API mechanism(s), or that
    the two names' types are different and incomparable, so that
    the comparison operation could not be completed.

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 o  GSS_S_BAD_NAME indicates that one or both of the input names
    was ill-formed in terms of its internal type specifier, so
    the comparison operation could not be completed.
 o  GSS_S_FAILURE indicates that the call's operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to compare two internal name representations to
 determine whether they refer to the same entity.  If either name
 presented to GSS_Compare_name() denotes an anonymous principal,
 GSS_Compare_name() shall indicate FALSE.  It is not required that
 either or both inputs name1 and name2 be MNs; for some
 implementations and cases, GSS_S_BAD_NAMETYPE may be returned,
 indicating name incomparability, for the case where neither input
 name is an MN.

2.4.4: GSS_Display_name call

 Inputs:
 o  name INTERNAL NAME
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  name_string OCTET STRING,
 o  name_type OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a valid printable name
    representation is available in the returned name_string.
 o  GSS_S_BAD_NAMETYPE indicates that the provided name was of a
    type uninterpretable by the applicable underlying GSS-API
    mechanism(s), so no printable representation could be generated.
 o  GSS_S_BAD_NAME indicates that the contents of the provided name
    were inconsistent with the internally-indicated name type, so
    no printable representation could be generated.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.

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 Allows callers to translate an internal name representation into a
 printable form with associated namespace type descriptor. The syntax
 of the printable form is a local matter.
 If the input name represents an anonymous identity, a reserved value
 (GSS_C_NT_ANONYMOUS) shall be returned for name_type.

2.4.5: GSS_Import_name call

 Inputs:
 o  input_name_string OCTET STRING,
 o  input_name_type OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_name INTERNAL NAME
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a valid name representation is
    output in output_name and described by the type value in
    output_name_type.
 o  GSS_S_BAD_NAMETYPE indicates that the input_name_type is unsupported
    by the applicable underlying GSS-API mechanism(s), so the import
    operation could not be completed.
 o  GSS_S_BAD_NAME indicates that the provided input_name_string
    is ill-formed in terms of the input_name_type, so the import
    operation could not be completed.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to provide a name representation as a contiguous octet
 string, designate the type of namespace in conjunction with which it
 should be parsed, and convert that representation to an internal form
 suitable for input to other GSS-API routines.  The syntax of the
 input_name_string is defined in conjunction with its associated name
 type; depending on the input_name_type, the associated
 input_name_string may or may not be a printable string. Note: The
 input_name_type argument serves to describe and qualify the

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 interpretation of the associated input_name_string; it does not
 specify the data type of the returned output_name.
 If a mechanism claims support for a particular name type, its
 GSS_Import_name() operation shall be able to accept all possible
 values conformant to the external name syntax as defined for that
 name type.  These imported values may correspond to:
    (1) locally registered entities (for which credentials may be
    acquired),
    (2) non-local entities (for which local credentials cannot be
    acquired, but which may be referenced as targets of initiated
    security contexts or initiators of accepted security contexts), or
    to
    (3) neither of the above.
 Determination of whether a particular name belongs to class (1), (2),
 or (3) as described above is not guaranteed to be performed by the
 GSS_Import_name() function.
 The internal name generated by a GSS_Import_name() operation may be a
 single-mechanism MN, and is likely to be an MN within a single-
 mechanism implementation, but portable callers must not depend on
 this property (and must not, therefore, assume that the output from
 GSS_Import_name() can be passed directly to GSS_Export_name() without
 first being processed through GSS_Canonicalize_name()).

2.4.6: GSS_Release_name call

 Inputs:
 o  name INTERNAL NAME
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the storage associated with the
    input name was successfully released.
 o  GSS_S_BAD_NAME indicates that the input name argument did not
    contain a valid name.

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 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to release the storage associated with an internal
 name representation.  This call's specific behavior depends on the
 language and programming environment within which a GSS-API
 implementation operates, and is therefore detailed within applicable
 bindings specifications; in particular, this call may be superfluous
 within bindings where memory management is automatic.

2.4.7: GSS_Release_buffer call

 Inputs:
 o  buffer OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the storage associated with the
    input buffer was successfully released.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to release the storage associated with an OCTET STRING
 buffer allocated by another GSS-API call.  This call's specific
 behavior depends on the language and programming environment within
 which a GSS-API implementation operates, and is therefore detailed
 within applicable bindings specifications; in particular, this call
 may be superfluous within bindings where memory management is
 automatic.

2.4.8: GSS_Release_OID_set call

 Inputs:
 o  buffer SET OF OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER,

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 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the storage associated with the
    input object identifier set was successfully released.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to release the storage associated with an object
 identifier set object allocated by another GSS-API call.  This call's
 specific behavior depends on the language and programming environment
 within which a GSS-API implementation operates, and is therefore
 detailed within applicable bindings specifications; in particular,
 this call may be superfluous within bindings where memory management
 is automatic.

2.4.9: GSS_Create_empty_OID_set call

 Inputs:
 o  (none)
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  oid_set SET OF OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates successful completion
 o  GSS_S_FAILURE indicates that the operation failed
 Creates an object identifier set containing no object identifiers, to
 which members may be subsequently added using the
 GSS_Add_OID_set_member() routine.  These routines are intended to be
 used to construct sets of mechanism object identifiers, for input to
 GSS_Acquire_cred().

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2.4.10: GSS_Add_OID_set_member call

 Inputs:
 o  member_oid OBJECT IDENTIFIER,
 o  oid_set SET OF OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 Return major_status codes:
 o  GSS_S_COMPLETE indicates successful completion
 o  GSS_S_FAILURE indicates that the operation failed
 Adds an Object Identifier to an Object Identifier set.  This routine
 is intended for use in conjunction with GSS_Create_empty_OID_set()
 when constructing a set of mechanism OIDs for input to
 GSS_Acquire_cred().

2.4.11: GSS_Test_OID_set_member call

 Inputs:
 o  member OBJECT IDENTIFIER,
 o  set SET OF OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  present BOOLEAN
 Return major_status codes:
 o  GSS_S_COMPLETE indicates successful completion
 o  GSS_S_FAILURE indicates that the operation failed

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 Interrogates an Object Identifier set to determine whether a
 specified Object Identifier is a member.  This routine is intended to
 be used with OID sets returned by GSS_Indicate_mechs(),
 GSS_Acquire_cred(), and GSS_Inquire_cred().

2.4.12: GSS_Release_OID call

 Inputs:
 o  oid OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates successful completion
 o  GSS_S_FAILURE indicates that the operation failed
 Allows the caller to release the storage associated with an OBJECT
 IDENTIFIER buffer allocated by another GSS-API call. This call's
 specific behavior depends on the language and programming environment
 within which a GSS-API implementation operates, and is therefore
 detailed within applicable bindings specifications; in particular,
 this call may be superfluous within bindings where memory management
 is automatic.

2.4.13: GSS_OID_to_str call

 Inputs:
 o  oid OBJECT IDENTIFIER
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  oid_str OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates successful completion

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 o  GSS_S_FAILURE indicates that the operation failed
 The function GSS_OID_to_str() returns a string representing the input
 OID in numeric ASN.1 syntax format (curly-brace enclosed, space-
 delimited, e.g., "{2 16 840 1 113687 1 2 1}"). The string is
 releasable using GSS_Release_buffer(). If the input "oid" does not
 represent a syntactically valid object identifier, GSS_S_FAILURE
 status is returned and the returned oid_str result is NULL.

2.4.14: GSS_Str_to_OID call

 Inputs:
 o  oid_str OCTET STRING
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  oid OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates successful completion
 o  GSS_S_FAILURE indicates that the operation failed
 The function GSS_Str_to_OID() constructs and returns an OID from its
 printable form; implementations should be able to accept the numeric
 ASN.1 syntax form as described for GSS_OID_to_str(), and this form
 should be used for portability, but implementations of this routine
 may also accept other formats (e.g., "1.2.3.3"). The OID is suitable
 for release using the function GSS_Release_OID(). If the input
 oid_str cannot be translated into an OID, GSS_S_FAILURE status is
 returned and the "oid" result is NULL.

2.4.15: GSS_Inquire_names_for_mech call

 Input:
 o  input_mech_type OBJECT IDENTIFIER, -- mechanism type
 Outputs:
 o  major_status INTEGER,

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 o  minor_status INTEGER,
 o  name_type_set SET OF OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that the output name_type_set contains
    a list of name types which are supported by the locally available
    mechanism identified by input_mech_type.
 o  GSS_S_BAD_MECH indicates that the mechanism identified by
    input_mech_type was unsupported within the local implementation,
    causing the query to fail.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 Allows callers to determine the set of name types which are
 supportable by a specific locally-available mechanism.

2.4.16: GSS_Inquire_mechs_for_name call

 Inputs:
 o  input_name INTERNAL NAME,
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  mech_types SET OF OBJECT IDENTIFIER
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a set of object identifiers,
    corresponding to the set of mechanisms suitable for processing
    the input_name, is available in mech_types.
 o  GSS_S_BAD_NAME indicates that the input_name could not be
    processed.
 o  GSS_S_BAD_NAMETYPE indicates that the type of the input_name
    is unsupported by the GSS-API implementation.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.

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 This routine returns the mechanism set with which the input_name may
 be processed.  After use, the mech_types object should be freed by
 the caller via the GSS_Release_OID_set() call.  Note: it is
 anticipated that implementations of GSS_Inquire_mechs_for_name() will
 commonly operate based on type information describing the
 capabilities of available mechanisms; it is not guaranteed that all
 identified mechanisms will necessarily be able to canonicalize (via
 GSS_Canonicalize_name()) a particular name.

2.4.17: GSS_Canonicalize_name call

 Inputs:
 o  input_name INTERNAL NAME,
 o  mech_type OBJECT IDENTIFIER  -- must be explicit mechanism,
                                    not "default" specifier
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_name INTERNAL NAME
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a mechanism-specific reduction of
    the input_name, as processed by the mechanism identified by
    mech_type, is available in output_name.
 o  GSS_S_BAD_MECH indicates that the identified mechanism is
    unsupported.
 o  GSS_S_BAD_NAMETYPE indicates that the input name does not
    contain an element with suitable type for processing by the
    identified mechanism.
 o  GSS_S_BAD_NAME indicates that the input name contains an
    element with suitable type for processing by the identified
    mechanism, but that this element could not be processed
    successfully.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.

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 This routine reduces a GSS-API internal name, which may in general
 contain elements corresponding to multiple mechanisms, to a
 mechanism-specific Mechanism Name (MN) by applying the translations
 corresponding to the mechanism identified by mech_type.

2.4.18: GSS_Export_name call

 Inputs:
 o  input_name INTERNAL NAME, -- required to be MN
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  output_name OCTET STRING
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that a flat representation of the
    input name is available in output_name.
 o  GSS_S_NAME_NOT_MN indicates that the input name contained
    elements corresponding to multiple mechanisms, so cannot
    be exported into a single-mechanism flat form.
 o  GSS_S_BAD_NAME indicates that the input name was an MN,
    but could not be processed.
 o  GSS_S_BAD_NAMETYPE indicates that the input name was an MN,
    but that its type is unsupported by the GSS-API implementation.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 This routine creates a flat name representation, suitable for
 bytewise comparison or for input to GSS_Import_name() in conjunction
 with the reserved GSS-API Exported Name Object OID, from a internal-
 form Mechanism Name (MN) as emitted, e.g., by GSS_Canonicalize_name()
 or GSS_Accept_sec_context().
 The emitted GSS-API Exported Name Object is self-describing; no
 associated parameter-level OID need be emitted by this call.  This
 flat representation consists of a mechanism-independent wrapper
 layer, defined in Section 3.2 of this document, enclosing a
 mechanism-defined name representation.

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 In all cases, the flat name output by GSS_Export_name() to correspond
 to a particular input MN must be invariant over time within a
 particular installation.
 The GSS_S_NAME_NOT_MN status code is provided to enable
 implementations to reject input names which are not MNs.  It is not,
 however, required for purposes of conformance to this specification
 that all non-MN input names must necessarily be rejected.

2.4.19: GSS_Duplicate_name call

 Inputs:
 o  src_name INTERNAL NAME
 Outputs:
 o  major_status INTEGER,
 o  minor_status INTEGER,
 o  dest_name INTERNAL NAME
 Return major_status codes:
 o  GSS_S_COMPLETE indicates that dest_name references an internal
    name object containing the same name as passed to src_name.
 o  GSS_S_BAD_NAME indicates that the input name was invalid.
 o  GSS_S_BAD_NAMETYPE indicates that the input name's type
    is unsupported by the GSS-API implementation.
 o  GSS_S_FAILURE indicates that the requested operation could not
    be performed for reasons unspecified at the GSS-API level.
 This routine takes input internal name src_name, and returns another
 reference (dest_name) to that name which can be used even if src_name
 is later freed.  (Note: This may be implemented by copying or through
 use of reference counts.)

3: Data Structure Definitions for GSS-V2 Usage

 Subsections of this section define, for interoperability and
 portability purposes, certain data structures for use with GSS-V2.

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3.1: Mechanism-Independent Token Format

 This section specifies a mechanism-independent level of encapsulating
 representation for the initial token of a GSS-API context
 establishment sequence, incorporating an identifier of the mechanism
 type to be used on that context and enabling tokens to be interpreted
 unambiguously at GSS-API peers. Use of this format is required for
 initial context establishment tokens of Internet standards-track
 GSS-API mechanisms; use in non-initial tokens is optional.
 The encoding format for the token tag is derived from ASN.1 and DER
 (per illustrative ASN.1 syntax included later within this
 subsection), but its concrete representation is defined directly in
 terms of octets rather than at the ASN.1 level in order to facilitate
 interoperable implementation without use of general ASN.1 processing
 code.  The token tag consists of the following elements, in order:
    1. 0x60 -- Tag for [APPLICATION 0] SEQUENCE; indicates that
    constructed form, definite length encoding follows.
    2. Token length octets, specifying length of subsequent data
    (i.e., the summed lengths of elements 3-5 in this list, and of the
    mechanism-defined token object following the tag).  This element
    comprises a variable number of octets:
    2a. If the indicated value is less than 128, it shall be
    represented in a single octet with bit 8 (high order) set to "0"
    and the remaining bits representing the value.
    2b. If the indicated value is 128 or more, it shall be represented
    in two or more octets, with bit 8 of the first octet set to "1"
    and the remaining bits of the first octet specifying the number of
    additional octets.  The subsequent octets carry the value, 8 bits
    per octet, most significant digit first.  The minimum number of
    octets shall be used to encode the length (i.e., no octets
    representing leading zeros shall be included within the length
    encoding).
    3. 0x06 -- Tag for OBJECT IDENTIFIER
    4. Object identifier length -- length (number of octets) of the
    encoded object identifier contained in element 5, encoded per
    rules as described in 2a. and 2b. above.
    5. Object identifier octets -- variable number of octets, encoded
    per ASN.1 BER rules:

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    5a. The first octet contains the sum of two values: (1) the top-
    level object identifier component, multiplied by 40 (decimal), and
    (2) the second-level object identifier component.  This special
    case is the only point within an object identifier encoding where
    a single octet represents contents of more than one component.
    5b. Subsequent octets, if required, encode successively-lower
    components in the represented object identifier.  A component's
    encoding may span multiple octets, encoding 7 bits per octet (most
    significant bits first) and with bit 8 set to "1" on all but the
    final octet in the component's encoding.  The minimum number of
    octets shall be used to encode each component (i.e., no octets
    representing leading zeros shall be included within a component's
    encoding).
    (Note: In many implementations, elements 3-5 may be stored and
    referenced as a contiguous string constant.)
 The token tag is immediately followed by a mechanism-defined token
 object.  Note that no independent size specifier intervenes following
 the object identifier value to indicate the size of the mechanism-
 defined token object.  While ASN.1 usage within mechanism-defined
 tokens is permitted, there is no requirement that the mechanism-
 specific innerContextToken, innerMsgToken, and sealedUserData data
 elements must employ ASN.1 BER/DER encoding conventions.

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 The following ASN.1 syntax is included for descriptive purposes only,
 to illustrate structural relationships among token and tag objects.
 For interoperability purposes, token and tag encoding shall be
 performed using the concrete encoding procedures described earlier in
 this subsection.
     GSS-API DEFINITIONS ::=
     BEGIN
     MechType ::= OBJECT IDENTIFIER
     -- data structure definitions
  1. - callers must be able to distinguish among
  2. - InitialContextToken, SubsequentContextToken,
  3. - PerMsgToken, and SealedMessage data elements
  4. - based on the usage in which they occur
     InitialContextToken ::=
     -- option indication (delegation, etc.) indicated within
     -- mechanism-specific token
     [APPLICATION 0] IMPLICIT SEQUENCE {
             thisMech MechType,
             innerContextToken ANY DEFINED BY thisMech
                -- contents mechanism-specific
                -- ASN.1 structure not required
             }
     SubsequentContextToken ::= innerContextToken ANY
     -- interpretation based on predecessor InitialContextToken
     -- ASN.1 structure not required
     PerMsgToken ::=
     -- as emitted by GSS_GetMIC and processed by GSS_VerifyMIC
     -- ASN.1 structure not required
             innerMsgToken ANY
     SealedMessage ::=
     -- as emitted by GSS_Wrap and processed by GSS_Unwrap
     -- includes internal, mechanism-defined indicator
     -- of whether or not encrypted
     -- ASN.1 structure not required
             sealedUserData ANY
     END

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3.2: Mechanism-Independent Exported Name Object Format

 This section specifies a mechanism-independent level of encapsulating
 representation for names exported via the GSS_Export_name() call,
 including an object identifier representing the exporting mechanism.
 The format of names encapsulated via this representation shall be
 defined within individual mechanism drafts.  Name objects of this
 type will be identified with the following Object Identifier:
 {1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
 4(gss-api-exported-name)}
 No name type OID is included in this mechanism-independent level of
 format definition, since (depending on individual mechanism
 specifications) the enclosed name may be implicitly typed or may be
 explicitly typed using a means other than OID encoding.
      Length    Name          Description
      2               TOK_ID          Token Identifier
                                      For exported name objects, this
                                      must be hex 04 01.
      2               MECH_OID_LEN    Length of the Mechanism OID
      MECH_OID_LEN    MECH_OID        Mechanism OID, in DER
      4               NAME_LEN        Length of name
      NAME_LEN        NAME            Exported name; format defined in
                                      applicable mechanism draft.

4: Name Type Definitions

 This section includes definitions for name types and associated
 syntaxes which are defined in a mechanism-independent fashion at the
 GSS-API level rather than being defined in individual mechanism
 specifications.

4.1: Host-Based Service Name Form

 The following Object Identifier value is provided as a means to
 identify this name form:
 {1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
 2(gss-host-based-services)}
 The recommended symbolic name for this type is
 "GSS_C_NT_HOSTBASED_SERVICE".

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 This name type is used to represent services associated with host
 computers.  This name form is constructed using two elements,
 "service" and "hostname", as follows:
                           service@hostname
 When a reference to a name of this type is resolved, the "hostname"
 is canonicalized by attempting a DNS lookup and using the fully-
 qualified domain name which is returned, or by using the "hostname"
 as provided if the DNS lookup fails.  The canonicalization operation
 also maps the host's name into lower-case characters.
 The "hostname" element may be omitted. If no "@" separator is
 included, the entire name is interpreted as the service specifier,
 with the "hostname" defaulted to the canonicalized name of the local
 host.
 Values for the "service" element are registered with the IANA.

4.2: User Name Form

 This name form shall be represented by the Object Identifier {iso(1)
 member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
 generic(1) user_name(1)}. The recommended mechanism-independent
 symbolic name for this type is "GSS_C_NT_USER_NAME". (Note: the same
 name form and OID is defined within the Kerberos V5 GSS-API
 mechanism, but the symbolic name recommended there begins with a
 "GSS_KRB5_NT_" prefix.)
 This name type is used to indicate a named user on a local system.
 Its interpretation is OS-specific.  This name form is constructed as:
                               username

4.3: Machine UID Form

 This name form shall be represented by the Object Identifier {iso(1)
 member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
 generic(1) machine_uid_name(2)}.  The recommended mechanism-
 independent symbolic name for this type is
 "GSS_C_NT_MACHINE_UID_NAME".  (Note: the same name form and OID is
 defined within the Kerberos V5 GSS-API mechanism, but the symbolic
 name recommended there begins with a "GSS_KRB5_NT_" prefix.)
 This name type is used to indicate a numeric user identifier
 corresponding to a user on a local system.  Its interpretation is
 OS-specific.  The gss_buffer_desc representing a name of this type
 should contain a locally-significant uid_t, represented in host byte

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 order.  The GSS_Import_name() operation resolves this uid into a
 username, which is then treated as the User Name Form.

4.4: String UID Form

 This name form shall be represented by the Object Identifier {iso(1)
 member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
 generic(1) string_uid_name(3)}.  The recommended symbolic name for
 this type is "GSS_C_NT_STRING_UID_NAME".  (Note: the same name form
 and OID is defined within the Kerberos V5 GSS-API mechanism, but the
 symbolic name recommended there begins with a "GSS_KRB5_NT_" prefix.)
 This name type is used to indicate a string of digits representing
 the numeric user identifier of a user on a local system.  Its
 interpretation is OS-specific. This name type is similar to the
 Machine UID Form, except that the buffer contains a string
 representing the uid_t.

5: Mechanism-Specific Example Scenarios

 This section provides illustrative overviews of the use of various
 candidate mechanism types to support the GSS-API. These discussions
 are intended primarily for readers familiar with specific security
 technologies, demonstrating how GSS-API functions can be used and
 implemented by candidate underlying mechanisms. They should not be
 regarded as constrictive to implementations or as defining the only
 means through which GSS-API functions can be realized with a
 particular underlying technology, and do not demonstrate all GSS-API
 features with each technology.

5.1: Kerberos V5, single-TGT

 OS-specific login functions yield a TGT to the local realm Kerberos
 server; TGT is placed in a credentials structure for the client.
 Client calls GSS_Acquire_cred()  to acquire a cred_handle in order to
 reference the credentials for use in establishing security contexts.
 Client calls GSS_Init_sec_context().  If the requested service is
 located in a different realm, GSS_Init_sec_context()  gets the
 necessary TGT/key pairs needed to traverse the path from local to
 target realm; these data are placed in the owner's TGT cache. After
 any needed remote realm resolution, GSS_Init_sec_context()  yields a
 service ticket to the requested service with a corresponding session
 key; these data are stored in conjunction with the context. GSS-API
 code sends KRB_TGS_REQ request(s) and receives KRB_TGS_REP
 response(s) (in the successful case) or KRB_ERROR.

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 Assuming success, GSS_Init_sec_context()  builds a Kerberos-formatted
 KRB_AP_REQ message, and returns it in output_token.  The client sends
 the output_token to the service.
 The service passes the received token as the input_token argument to
 GSS_Accept_sec_context(),  which verifies the authenticator, provides
 the service with the client's authenticated name, and returns an
 output_context_handle.
 Both parties now hold the session key associated with the service
 ticket, and can use this key in subsequent GSS_GetMIC(),
 GSS_VerifyMIC(),  GSS_Wrap(), and GSS_Unwrap() operations.

5.2: Kerberos V5, double-TGT

 TGT acquisition as above.
 Note: To avoid unnecessary frequent invocations of error paths when
 implementing the GSS-API atop Kerberos V5, it seems appropriate to
 represent "single-TGT K-V5" and "double-TGT K-V5" with separate
 mech_types, and this discussion makes that assumption.
 Based on the (specified or defaulted) mech_type,
 GSS_Init_sec_context()  determines that the double-TGT protocol
 should be employed for the specified target. GSS_Init_sec_context()
 returns GSS_S_CONTINUE_NEEDED major_status, and its returned
 output_token contains a request to the service for the service's TGT.
 (If a service TGT with suitably long remaining lifetime already
 exists in a cache, it may be usable, obviating the need for this
 step.) The client passes the output_token to the service.  Note: this
 scenario illustrates a different use for the GSS_S_CONTINUE_NEEDED
 status return facility than for support of mutual authentication;
 note that both uses can coexist as successive operations within a
 single context establishment operation.
 The service passes the received token as the input_token argument to
 GSS_Accept_sec_context(),  which recognizes it as a request for TGT.
 (Note that current Kerberos V5 defines no intra-protocol mechanism to
 represent such a request.) GSS_Accept_sec_context()  returns
 GSS_S_CONTINUE_NEEDED major_status and provides the service's TGT in
 its output_token. The service sends the output_token to the client.
 The client passes the received token as the input_token argument to a
 continuation of GSS_Init_sec_context(). GSS_Init_sec_context() caches
 the received service TGT and uses it as part of a service ticket
 request to the Kerberos authentication server, storing the returned
 service ticket and session key in conjunction with the context.
 GSS_Init_sec_context()  builds a Kerberos-formatted authenticator,

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 and returns it in output_token along with GSS_S_COMPLETE return
 major_status. The client sends the output_token to the service.
 Service passes the received token as the input_token argument to a
 continuation call to GSS_Accept_sec_context().
 GSS_Accept_sec_context()  verifies the authenticator, provides the
 service with the client's authenticated name, and returns
 major_status GSS_S_COMPLETE.
 GSS_GetMIC(),  GSS_VerifyMIC(), GSS_Wrap(), and GSS_Unwrap()  as
 above.

5.3: X.509 Authentication Framework

 This example illustrates use of the GSS-API in conjunction with
 public-key mechanisms, consistent with the X.509 Directory
 Authentication Framework.
 The GSS_Acquire_cred()  call establishes a credentials structure,
 making the client's private key accessible for use on behalf of the
 client.
 The client calls GSS_Init_sec_context(),  which interrogates the
 Directory to acquire (and validate) a chain of public-key
 certificates, thereby collecting the public key of the service.  The
 certificate validation operation determines that suitable integrity
 checks were applied by trusted authorities and that those
 certificates have not expired. GSS_Init_sec_context()  generates a
 secret key for use in per-message protection operations on the
 context, and enciphers that secret key under the service's public
 key.
 The enciphered secret key, along with an authenticator quantity
 signed with the client's private key, is included in the output_token
 from GSS_Init_sec_context().  The output_token also carries a
 certification path, consisting of a certificate chain leading from
 the service to the client; a variant approach would defer this path
 resolution to be performed by the service instead of being asserted
 by the client. The client application sends the output_token to the
 service.
 The service passes the received token as the input_token argument to
 GSS_Accept_sec_context().  GSS_Accept_sec_context() validates the
 certification path, and as a result determines a certified binding
 between the client's distinguished name and the client's public key.
 Given that public key, GSS_Accept_sec_context() can process the
 input_token's authenticator quantity and verify that the client's
 private key was used to sign the input_token. At this point, the

Linn Standards Track [Page 81] RFC 2078 GSS-API January 1997

 client is authenticated to the service. The service uses its private
 key to decipher the enciphered secret key provided to it for per-
 message protection operations on the context.
 The client calls GSS_GetMIC()  or GSS_Wrap() on a data message, which
 causes per-message authentication, integrity, and (optional)
 confidentiality facilities to be applied to that message. The service
 uses the context's shared secret key to perform corresponding
 GSS_VerifyMIC()  and GSS_Unwrap() calls.

6: Security Considerations

 Security issues are discussed throughout this memo.

7: Related Activities

 In order to implement the GSS-API atop existing, emerging, and future
 security mechanisms:
    object identifiers must be assigned to candidate GSS-API
    mechanisms and the name types which they support
    concrete data element formats and processing procedures must be
    defined for candidate mechanisms
 Calling applications must implement formatting conventions which will
 enable them to distinguish GSS-API tokens from other data carried in
 their application protocols.
 Concrete language bindings are required for the programming
 environments in which the GSS-API is to be employed, as RFC-1509
 defines for the C programming language and GSS-V1.

Linn Standards Track [Page 82] RFC 2078 GSS-API January 1997

APPENDIX A

MECHANISM DESIGN CONSTRAINTS

 The following constraints on GSS-API mechanism designs are adopted in
 response to observed caller protocol requirements, and adherence
 thereto is anticipated in subsequent descriptions of GSS-API
 mechanisms to be documented in standards-track Internet
 specifications.
 It is strongly recommended that mechanisms offering per-message
 protection services also offer at least one of the replay detection
 and sequencing services, as mechanisms offering neither of the latter
 will fail to satisfy recognized requirements of certain candidate
 caller protocols.

APPENDIX B

                       COMPATIBILITY WITH GSS-V1
 It is the intent of this document to define an interface and
 procedures which preserve compatibility between GSS-V1 (RFC-1508)
 callers and GSS- V2 providers.  All calls defined in GSS-V1 are
 preserved, and it has been a goal that GSS-V1 callers should be able
 to operate atop GSS-V2 provider implementations.  Certain detailed
 changes, summarized in this section, have been made in order to
 resolve omissions identified in GSS-V1.
 The following GSS-V1 constructs, while supported within GSS-V2, are
 deprecated:
    Names for per-message processing routines: GSS_Seal() deprecated
    in favor of GSS_Wrap(); GSS_Sign() deprecated in favor of
    GSS_GetMIC(); GSS_Unseal() deprecated in favor of GSS_Unwrap();
    GSS_Verify() deprecated in favor of GSS_VerifyMIC().
    GSS_Delete_sec_context() facility for context_token usage,
    allowing mechanisms to signal context deletion, is retained for
    compatibility with GSS-V1.  For current usage, it is recommended
    that both peers to a context invoke GSS_Delete_sec_context()
    independently, passing a null output_context_token buffer to
    indicate that no context_token is required.  Implementations of
    GSS_Delete_sec_context() should delete relevant locally-stored
    context information.

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 This GSS-V2 specification adds the following calls which are not
 present in GSS-V1:
    Credential management calls: GSS_Add_cred(),
    GSS_Inquire_cred_by_mech().
    Context-level calls: GSS_Inquire_context(), GSS_Wrap_size_limit(),
    GSS_Export_sec_context(), GSS_Import_sec_context().
    Per-message calls: No new calls.  Existing calls have been renamed.
    Support calls: GSS_Create_empty_OID_set(),
    GSS_Add_OID_set_member(), GSS_Test_OID_set_member(),
    GSS_Release_OID(), GSS_OID_to_str(), GSS_Str_to_OID(),
    GSS_Inquire_names_for_mech(), GSS_Inquire_mechs_for_name(),
    GSS_Canonicalize_name(), GSS_Export_name(), GSS_Duplicate_name().
 This GSS-V2 specification introduces three new facilities applicable
 to security contexts, indicated using the following context state
 values which are not present in GSS-V1:
    anon_state, set TRUE to indicate that a context's initiator is
    anonymous from the viewpoint of the target; Section 1.2.5 of this
    specification provides a summary description of the GSS-V2
    anonymity support facility, support and use of which is optional.
    prot_ready_state, set TRUE to indicate that a context may be used
    for per-message protection before final completion of context
    establishment; Section 1.2.7 of this specification provides a
    summary description of the GSS-V2 facility enabling mechanisms to
    selectively permit per-message protection during context
    establishment, support and use of which is optional.
    trans_state, set TRUE to indicate that a context is transferable to
    another process using the GSS-V2 GSS_Export_sec_context() facility.
 These state values are represented (at the C bindings level) in
 positions within a bit vector which are unused in GSS-V1, and may be
 safely ignored by GSS-V1 callers.
 Relative to GSS-V1, GSS-V2 provides additional guidance to GSS-API
 implementors in the following areas: implementation robustness,
 credential management, behavior in multi-mechanism configurations,
 naming support, and inclusion of optional sequencing services.  The
 token tagging facility as defined in GSS-V2, Section 3.1, is now
 described directly in terms of octets to facilitate interoperable
 implementation without general ASN.1 processing code; the
 corresponding ASN.1 syntax, included for descriptive purposes, is

Linn Standards Track [Page 84] RFC 2078 GSS-API January 1997

 unchanged from that in GSS-V1. For use in conjunction with added
 naming support facilities, a new Exported Name Object construct is
 added.  Additional name types are introduced in Section 4.
 This GSS-V2 specification adds the following major_status values
 which are not defined in GSS-V1:
   GSS_S_BAD_QOP                 unsupported QOP value
   GSS_S_UNAUTHORIZED            operation unauthorized
   GSS_S_UNAVAILABLE             operation unavailable
   GSS_S_DUPLICATE_ELEMENT       duplicate credential element requested
   GSS_S_NAME_NOT_MN             name contains multi-mechanism elements
   GSS_S_GAP_TOKEN               skipped predecessor token(s)
                                  detected
 Of these added status codes, only two values are defined to be
 returnable by calls existing in GSS-V1: GSS_S_BAD_QOP (returnable by
 GSS_GetMIC() and GSS_Wrap()), and GSS_S_GAP_TOKEN (returnable by
 GSS_VerifyMIC() and GSS_Unwrap()).
 Additionally, GSS-V2 descriptions of certain calls present in GSS-V1
 have been updated to allow return of additional major_status values
 from the set as defined in GSS-V1: GSS_Inquire_cred() has
 GSS_S_DEFECTIVE_CREDENTIAL and GSS_S_CREDENTIALS_EXPIRED defined as
 returnable, GSS_Init_sec_context() has GSS_S_OLD_TOKEN,
 GSS_S_DUPLICATE_TOKEN, and GSS_S_BAD_MECH defined as returnable, and
 GSS_Accept_sec_context() has GSS_S_BAD_MECH defined as returnable.

Author's Address

 John Linn
 OpenVision Technologies
 One Main St.
 Cambridge, MA  02142  USA
 Phone: +1 617.374.2245
 EMail: John.Linn@ov.com

Linn Standards Track [Page 85]

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