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.Dd January 26, 2010
.Dt GSSAPI 3
.Os
.Sh NAME
.Nm gssapi
.Nd "Generic Security Services API"
.Sh LIBRARY
GSS-API Library (libgssapi, -lgssapi)
.Sh SYNOPSIS
.In gssapi/gssapi.h
.Sh DESCRIPTION
The Generic Security Service Application Programming Interface
provides security services to its callers,
and is intended for implementation atop a variety of underlying
cryptographic mechanisms.
Typically, GSS-API callers will be application protocols into which
security enhancements are integrated through invocation of services
provided by the GSS-API.
The GSS-API allows a caller application to authenticate a principal
identity associated with a peer application, to delegate rights to a
peer,
and to apply security services such as confidentiality and integrity
on a per-message basis.
.Pp
There are four stages to using the GSS-API:
.Pp
.Bl -tag -width "a)"
.It a)
The application acquires a set of credentials with which it may prove
its identity to other processes.
The application's credentials vouch for its global identity,
which may or may not be related to any local username under which it
may be running.
.It b)
A pair of communicating applications establish a joint security
context using their credentials.
The security context is a pair of GSS-API data structures that contain
shared state information, which is required in order that per-message
security services may be provided.
Examples of state that might be shared between applications as part of
a security context are cryptographic keys,
and message sequence numbers.
As part of the establishment of a security context,
the context initiator is authenticated to the responder,
and may require that the responder is authenticated in turn.
The initiator may optionally give the responder the right to initiate
further security contexts,
acting as an agent or delegate of the initiator.
This transfer of rights is termed delegation,
and is achieved by creating a set of credentials,
similar to those used by the initiating application,
but which may be used by the responder.
.Pp
To establish and maintain the shared information that makes up the
security context,
certain GSS-API calls will return a token data structure,
which is an opaque data type that may contain cryptographically
protected data.
The caller of such a GSS-API routine is responsible for transferring
the token to the peer application,
encapsulated if necessary in an application protocol.
On receipt of such a token, the peer application should pass it to a
corresponding GSS-API routine which will decode the token and extract
the information,
updating the security context state information accordingly.
.It c)
Per-message services are invoked to apply either:
.Pp
integrity and data origin authentication, or confidentiality,
integrity and data origin authentication to application data,
which are treated by GSS-API as arbitrary octet-strings.
An application transmitting a message that it wishes to protect will
call the appropriate GSS-API routine (gss_get_mic or gss_wrap) to
apply protection,
specifying the appropriate security context,
and send the resulting token to the receiving application.
The receiver will pass the received token (and, in the case of data
protected by gss_get_mic, the accompanying message-data) to the
corresponding decoding routine (gss_verify_mic or gss_unwrap) to
remove the protection and validate the data.
.It d)
At the completion of a communications session (which may extend across
several transport connections),
each application calls a GSS-API routine to delete the security
context.
Multiple contexts may also be used (either successively or
simultaneously) within a single communications association, at the
option of the applications.
.El
.Sh GSS-API ROUTINES
This section lists the routines that make up the GSS-API,
and offers a brief description of the purpose of each routine.
.Pp
GSS-API Credential-management Routines:
.Bl -tag -width "gss_inquire_cred_by_mech"
.It gss_acquire_cred
Assume a global identity; Obtain a GSS-API credential handle for
pre-existing credentials.
.It gss_add_cred
Construct credentials incrementally
.It gss_inquire_cred
Obtain information about a credential
.It gss_inquire_cred_by_mech
Obtain per-mechanism information about a credential.
.It gss_release_cred
Discard a credential handle.
.El
.Pp
GSS-API Context-Level Routines:
.Bl -tag -width "gss_inquire_cred_by_mech"
.It gss_init_sec_context
Initiate a security context with a peer application
.It gss_accept_sec_context
 Accept a security context initiated by a peer application
.It gss_delete_sec_context
Discard a security context
.It gss_process_context_token
Process a token on a security context from a peer application
.It gss_context_time
Determine for how long a context will remain valid
.It gss_inquire_context
Obtain information about a security context
.It gss_wrap_size_limit
Determine token-size limit for
.Xr gss_wrap 3
on a context
.It gss_export_sec_context
Transfer a security context to another process
.It gss_import_sec_context
Import a transferred context
.El
.Pp
GSS-API Per-message Routines:
.Bl -tag -width "gss_inquire_cred_by_mech"
.It gss_get_mic
Calculate a cryptographic message integrity code (MIC) for a message;
integrity service
.It gss_verify_mic
Check a MIC against a message;
verify integrity of a received message
.It gss_wrap
Attach a MIC to a message, and optionally encrypt the message content;
confidentiality service
.It gss_unwrap
Verify a message with attached MIC, and decrypt message content if
necessary.
.El
.Pp
GSS-API Name manipulation Routines:
.Bl -tag -width "gss_inquire_cred_by_mech"
.It gss_import_name
Convert a contiguous string name to internal-form
.It gss_display_name
Convert internal-form name to text
.It gss_compare_name
Compare two internal-form names
.It gss_release_name
Discard an internal-form name
.It gss_inquire_names_for_mech
List the name-types supported by the specified mechanism
.It gss_inquire_mechs_for_name
List mechanisms that support the specified name-type
.It gss_canonicalize_name
Convert an internal name to an MN
.It gss_export_name
Convert an MN to export form
.It gss_duplicate_name
Create a copy of an internal name
.El
.Pp
GSS-API Miscellaneous Routines
.Bl -tag -width "gss_inquire_cred_by_mech"
.It gss_add_oid_set_member
Add an object identifier to a set
.It gss_display_status
Convert a GSS-API status code to text
.It gss_indicate_mechs
Determine available underlying authentication mechanisms
.It gss_release_buffer
Discard a buffer
.It gss_release_oid_set
Discard a set of object identifiers
.It gss_create_empty_oid_set
Create a set containing no object identifiers
.It gss_test_oid_set_member
Determines whether an object identifier is a member of a set.
.El
.Pp
Individual GSS-API implementations may augment these routines by
providing additional mechanism-specific routines if required
functionality is not available from the generic forms.
Applications are encouraged to use the generic routines wherever
possible on portability grounds.
.Sh STANDARDS
.Bl -tag
.It RFC 2743
Generic Security Service Application Program Interface Version 2, Update 1
.It RFC 2744
Generic Security Service API Version 2 : C-bindings
.El
.Sh HISTORY
The
.Nm
library first appeared in
.Fx 7.0 .
.Sh AUTHORS
John Wray, Iris Associates
.Sh COPYRIGHT
Copyright (C) The Internet Society (2000).  All Rights Reserved.
.Pp
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works.  However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
.Pp
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
.Pp
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.