RFC 2744
Generic Security Service API Version 2 : C-bindings
4. Additional Controls
This section discusses the optional services that a context initiator may request of the GSS-API at context establishment. Each of these services is requested by setting a flag in the req_flags input parameter to gss_init_sec_context. The optional services currently defined are: Delegation - The (usually temporary) transfer of rights from initiator to acceptor, enabling the acceptor to authenticate itself as an agent of the initiator. Mutual Authentication - In addition to the initiator authenticating its identity to the context acceptor, the context acceptor should also authenticate itself to the initiator. Replay detection - In addition to providing message integrity services, gss_get_mic and gss_wrap should include message numbering information to enable gss_verify_mic and gss_unwrap to detect if a message has been duplicated. Out-of-sequence detection - In addition to providing message integrity services, gss_get_mic and gss_wrap should include message sequencing information to enable gss_verify_mic and gss_unwrap to detect if a message has been received out of sequence.
Anonymous authentication - The establishment of the security context
should not reveal the initiator's identity to the context
acceptor.
Any currently undefined bits within such flag arguments should be
ignored by GSS-API implementations when presented by an application,
and should be set to zero when returned to the application by the
GSS-API implementation.
Some mechanisms may not support all optional services, and some
mechanisms may only support some services in conjunction with others.
Both gss_init_sec_context and gss_accept_sec_context inform the
applications which services will be available from the context when
the establishment phase is complete, via the ret_flags output
parameter. In general, if the security mechanism is capable of
providing a requested service, it should do so, even if additional
services must be enabled in order to provide the requested service.
If the mechanism is incapable of providing a requested service, it
should proceed without the service, leaving the application to abort
the context establishment process if it considers the requested
service to be mandatory.
Some mechanisms may specify that support for some services is
optional, and that implementors of the mechanism need not provide it.
This is most commonly true of the confidentiality service, often
because of legal restrictions on the use of data-encryption, but may
apply to any of the services. Such mechanisms are required to send
at least one token from acceptor to initiator during context
establishment when the initiator indicates a desire to use such a
service, so that the initiating GSS-API can correctly indicate
whether the service is supported by the acceptor's GSS-API.
4.1. Delegation
The GSS-API allows delegation to be controlled by the initiating
application via a boolean parameter to gss_init_sec_context(), the
routine that establishes a security context. Some mechanisms do not
support delegation, and for such mechanisms attempts by an
application to enable delegation are ignored.
The acceptor of a security context for which the initiator enabled
delegation will receive (via the delegated_cred_handle parameter of
gss_accept_sec_context) a credential handle that contains the
delegated identity, and this credential handle may be used to
initiate subsequent GSS-API security contexts as an agent or delegate
of the initiator. If the original initiator's identity is "A" and
the delegate's identity is "B", then, depending on the underlying
mechanism, the identity embodied by the delegated credential may be
either "A" or "B acting for A". For many mechanisms that support delegation, a simple boolean does not provide enough control. Examples of additional aspects of delegation control that a mechanism might provide to an application are duration of delegation, network addresses from which delegation is valid, and constraints on the tasks that may be performed by a delegate. Such controls are presently outside the scope of the GSS- API. GSS-API implementations supporting mechanisms offering additional controls should provide extension routines that allow these controls to be exercised (perhaps by modifying the initiator's GSS-API credential prior to its use in establishing a context). However, the simple delegation control provided by GSS-API should always be able to over-ride other mechanism-specific delegation controls - If the application instructs gss_init_sec_context() that delegation is not desired, then the implementation must not permit delegation to occur. This is an exception to the general rule that a mechanism may enable services even if they are not requested - delegation may only be provided at the explicit request of the application.4.2. Mutual authentication
Usually, a context acceptor will require that a context initiator authenticate itself so that the acceptor may make an access-control decision prior to performing a service for the initiator. In some cases, the initiator may also request that the acceptor authenticate itself. GSS-API allows the initiating application to request this mutual authentication service by setting a flag when calling gss_init_sec_context. The initiating application is informed as to whether or not the context acceptor has authenticated itself. Note that some mechanisms may not support mutual authentication, and other mechanisms may always perform mutual authentication, whether or not the initiating application requests it. In particular, mutual authentication my be required by some mechanisms in order to support replay or out-of- sequence message detection, and for such mechanisms a request for either of these services will automatically enable mutual authentication.
4.3. Replay and out-of-sequence detection
The GSS-API may provide detection of mis-ordered message once a security context has been established. Protection may be applied to messages by either application, by calling either gss_get_mic or gss_wrap, and verified by the peer application by calling gss_verify_mic or gss_unwrap. gss_get_mic calculates a cryptographic MIC over an application message, and returns that MIC in a token. The application should pass both the token and the message to the peer application, which presents them to gss_verify_mic. gss_wrap calculates a cryptographic MIC of an application message, and places both the MIC and the message inside a single token. The Application should pass the token to the peer application, which presents it to gss_unwrap to extract the message and verify the MIC. Either pair of routines may be capable of detecting out-of-sequence message delivery, or duplication of messages. Details of such mis- ordered messages are indicated through supplementary status bits in the major status code returned by gss_verify_mic or gss_unwrap. The relevant supplementary bits are: GSS_S_DUPLICATE_TOKEN - The token is a duplicate of one that has already been received and processed. Only contexts that claim to provide replay detection may set this bit. GSS_S_OLD_TOKEN - The token is too old to determine whether or not it is a duplicate. Contexts supporting out-of-sequence detection but not replay detection should always set this bit if GSS_S_UNSEQ_TOKEN is set; contexts that support replay detection should only set this bit if the token is so old that it cannot be checked for duplication. GSS_S_UNSEQ_TOKEN - A later token has already been processed. GSS_S_GAP_TOKEN - An earlier token has not yet been received. A mechanism need not maintain a list of all tokens that have been processed in order to support these status codes. A typical mechanism might retain information about only the most recent "N" tokens processed, allowing it to distinguish duplicates and missing tokens within the most recent "N" messages; the receipt of a token older than the most recent "N" would result in a GSS_S_OLD_TOKEN status.
4.4. Anonymous Authentication
In certain situations, an application may wish to initiate the authentication process to authenticate a peer, without revealing its own identity. As an example, consider an application providing access to a database containing medical information, and offering unrestricted access to the service. A client of such a service might wish to authenticate the service (in order to establish trust in any information retrieved from it), but might not wish the service to be able to obtain the client's identity (perhaps due to privacy concerns about the specific inquiries, or perhaps simply to avoid being placed on mailing-lists). In normal use of the GSS-API, the initiator's identity is made available to the acceptor as a result of the context establishment process. However, context initiators may request that their identity not be revealed to the context acceptor. Many mechanisms do not support anonymous authentication, and for such mechanisms the request will not be honored. An authentication token will be still be generated, but the application is always informed if a requested service is unavailable, and has the option to abort context establishment if anonymity is valued above the other security services that would require a context to be established. In addition to informing the application that a context is established anonymously (via the ret_flags outputs from gss_init_sec_context and gss_accept_sec_context), the optional src_name output from gss_accept_sec_context and gss_inquire_context will, for such contexts, return a reserved internal-form name, defined by the implementation. When presented to gss_display_name, this reserved internal-form name will result in a printable name that is syntactically distinguishable from any valid principal name supported by the implementation, associated with a name-type object identifier with the value GSS_C_NT_ANONYMOUS, whose value us given in Appendix A. The printable form of an anonymous name should be chosen such that it implies anonymity, since this name may appear in, for example, audit logs. For example, the string "<anonymous>" might be a good choice, if no valid printable names supported by the implementation can begin with "<" and end with ">".4.5. Confidentiality
If a context supports the confidentiality service, gss_wrap may be used to encrypt application messages. Messages are selectively encrypted, under the control of the conf_req_flag input parameter to gss_wrap.
4.6. Inter-process context transfer
GSS-API V2 provides routines (gss_export_sec_context and gss_import_sec_context) which allow a security context to be transferred between processes on a single machine. The most common use for such a feature is a client-server design where the server is implemented as a single process that accepts incoming security contexts, which then launches child processes to deal with the data on these contexts. In such a design, the child processes must have access to the security context data structure created within the parent by its call to gss_accept_sec_context so that they can use per-message protection services and delete the security context when the communication session ends. Since the security context data structure is expected to contain sequencing information, it is impractical in general to share a context between processes. Thus GSS-API provides a call (gss_export_sec_context) that the process which currently owns the context can call to declare that it has no intention to use the context subsequently, and to create an inter-process token containing information needed by the adopting process to successfully import the context. After successful completion of gss_export_sec_context, the original security context is made inaccessible to the calling process by GSS-API, and any context handles referring to this context are no longer valid. The originating process transfers the inter-process token to the adopting process, which passes it to gss_import_sec_context, and a fresh gss_ctx_id_t is created such that it is functionally identical to the original context. The inter-process token may contain sensitive data from the original security context (including cryptographic keys). Applications using inter-process tokens to transfer security contexts must take appropriate steps to protect these tokens in transit. Implementations are not required to support the inter-process transfer of security contexts. The ability to transfer a security context is indicated when the context is created, by gss_init_sec_context or gss_accept_sec_context setting the GSS_C_TRANS_FLAG bit in their ret_flags parameter.4.7. The use of incomplete contexts
Some mechanisms may allow the per-message services to be used before the context establishment process is complete. For example, a mechanism may include sufficient information in its initial context- level token for the context acceptor to immediately decode messages protected with gss_wrap or gss_get_mic. For such a mechanism, the initiating application need not wait until subsequent context-level
tokens have been sent and received before invoking the per-message protection services. The ability of a context to provide per-message services in advance of complete context establishment is indicated by the setting of the GSS_C_PROT_READY_FLAG bit in the ret_flags parameter from gss_init_sec_context and gss_accept_sec_context. Applications wishing to use per-message protection services on partially-established contexts should check this flag before attempting to invoke gss_wrap or gss_get_mic.5. GSS-API Routine Descriptions
In addition to the explicit major status codes documented here, the code GSS_S_FAILURE may be returned by any routine, indicating an implementation-specific or mechanism-specific error condition, further details of which are reported via the minor_status parameter.5.1. gss_accept_sec_context
OM_uint32 gss_accept_sec_context ( OM_uint32 *minor_status, gss_ctx_id_t *context_handle, const gss_cred_id_t acceptor_cred_handle, const gss_buffer_t input_token_buffer, const gss_channel_bindings_t input_chan_bindings, const gss_name_t *src_name, gss_OID *mech_type, gss_buffer_t output_token, OM_uint32 *ret_flags, OM_uint32 *time_rec, gss_cred_id_t *delegated_cred_handle) Purpose: Allows a remotely initiated security context between the application and a remote peer to be established. The routine may return a output_token which should be transferred to the peer application, where the peer application will present it to gss_init_sec_context. If no token need be sent, gss_accept_sec_context will indicate this by setting the length field of the output_token argument to zero. To complete the context establishment, one or more reply tokens may be required from the peer application; if so, gss_accept_sec_context will return a status flag of GSS_S_CONTINUE_NEEDED, in which case it should be called again when the reply token is received from the peer application, passing the token to gss_accept_sec_context via the input_token parameters.
Portable applications should be constructed to use the token length
and return status to determine whether a token needs to be sent or
waited for. Thus a typical portable caller should always invoke
gss_accept_sec_context within a loop:
gss_ctx_id_t context_hdl = GSS_C_NO_CONTEXT;
do {
receive_token_from_peer(input_token);
maj_stat = gss_accept_sec_context(&min_stat,
&context_hdl,
cred_hdl,
input_token,
input_bindings,
&client_name,
&mech_type,
output_token,
&ret_flags,
&time_rec,
&deleg_cred);
if (GSS_ERROR(maj_stat)) {
report_error(maj_stat, min_stat);
};
if (output_token->length != 0) {
send_token_to_peer(output_token);
gss_release_buffer(&min_stat, output_token);
};
if (GSS_ERROR(maj_stat)) {
if (context_hdl != GSS_C_NO_CONTEXT)
gss_delete_sec_context(&min_stat,
&context_hdl,
GSS_C_NO_BUFFER);
break;
};
} while (maj_stat & GSS_S_CONTINUE_NEEDED);
Whenever the routine returns a major status that includes the value
GSS_S_CONTINUE_NEEDED, the context is not fully established and the
following restrictions apply to the output parameters:
The value returned via the time_rec parameter is undefined Unless the
accompanying ret_flags parameter contains the bit
GSS_C_PROT_READY_FLAG, indicating that per-message services may be
applied in advance of a successful completion status, the value
returned via the mech_type parameter may be undefined until the
routine returns a major status value of GSS_S_COMPLETE.
The values of the GSS_C_DELEG_FLAG, GSS_C_MUTUAL_FLAG,GSS_C_REPLAY_FLAG, GSS_C_SEQUENCE_FLAG, GSS_C_CONF_FLAG,GSS_C_INTEG_FLAG and GSS_C_ANON_FLAG bits returned via the ret_flags parameter should contain the values that the implementation expects would be valid if context establishment were to succeed. The values of the GSS_C_PROT_READY_FLAG and GSS_C_TRANS_FLAG bits within ret_flags should indicate the actual state at the time gss_accept_sec_context returns, whether or not the context is fully established. Although this requires that GSS-API implementations set the GSS_C_PROT_READY_FLAG in the final ret_flags returned to a caller (i.e. when accompanied by a GSS_S_COMPLETE status code), applications should not rely on this behavior as the flag was not defined in Version 1 of the GSS-API. Instead, applications should be prepared to use per-message services after a successful context establishment, according to the GSS_C_INTEG_FLAG and GSS_C_CONF_FLAG values. All other bits within the ret_flags argument should be set to zero. While the routine returns GSS_S_CONTINUE_NEEDED, the values returned via the ret_flags argument indicate the services that the implementation expects to be available from the established context. If the initial call of gss_accept_sec_context() fails, the implementation should not create a context object, and should leave the value of the context_handle parameter set to GSS_C_NO_CONTEXT to indicate this. In the event of a failure on a subsequent call, the implementation is permitted to delete the "half-built" security context (in which case it should set the context_handle parameter to GSS_C_NO_CONTEXT), but the preferred behavior is to leave the security context (and the context_handle parameter) untouched for the application to delete (using gss_delete_sec_context). During context establishment, the informational status bits GSS_S_OLD_TOKEN and GSS_S_DUPLICATE_TOKEN indicate fatal errors, and GSS-API mechanisms should always return them in association with a routine error of GSS_S_FAILURE. This requirement for pairing did not exist in version 1 of the GSS-API specification, so applications that wish to run over version 1 implementations must special-case these codes.
Parameters:
context_handle gss_ctx_id_t, read/modify context handle for new
context. Supply GSS_C_NO_CONTEXT for first
call; use value returned in subsequent calls.
Once gss_accept_sec_context() has returned a
value via this parameter, resources have been
assigned to the corresponding context, and must
be freed by the application after use with a
call to gss_delete_sec_context().
acceptor_cred_handle gss_cred_id_t, read Credential handle claimed
by context acceptor. Specify
GSS_C_NO_CREDENTIAL to accept the context as a
default principal. If GSS_C_NO_CREDENTIAL is
specified, but no default acceptor principal is
defined, GSS_S_NO_CRED will be returned.
input_token_buffer buffer, opaque, read token obtained from remote
application.
input_chan_bindings channel bindings, read, optional Application-
specified bindings. Allows application to
securely bind channel identification information
to the security context. If channel bindings
are not used, specify GSS_C_NO_CHANNEL_BINDINGS.
src_name gss_name_t, modify, optional Authenticated name
of context initiator. After use, this name
should be deallocated by passing it to
gss_release_name(). If not required, specify
NULL.
mech_type Object ID, modify, optional Security mechanism
used. The returned OID value will be a pointer
into static storage, and should be treated as
read-only by the caller (in particular, it does
not need to be freed). If not required, specify
NULL.
output_token buffer, opaque, modify Token to be passed to
peer application. If the length field of the
returned token buffer is 0, then no token need
be passed to the peer application. If a non-
zero length field is returned, the associated
storage must be freed after use by the
application with a call to gss_release_buffer().
ret_flags bit-mask, modify, optional Contains various
independent flags, each of which indicates that
the context supports a specific service option.
If not needed, specify NULL. Symbolic names are
provided for each flag, and the symbolic names
corresponding to the required flags should be
logically-ANDed with the ret_flags value to test
whether a given option is supported by the
context. The flags are:
GSS_C_DELEG_FLAG
True - Delegated credentials are available
via the delegated_cred_handle
parameter
False - No credentials were delegated
GSS_C_MUTUAL_FLAG
True - Remote peer asked for mutual
authentication
False - Remote peer did not ask for mutual
authentication
GSS_C_REPLAY_FLAG
True - replay of protected messages
will be detected
False - replayed messages will not be
detected
GSS_C_SEQUENCE_FLAG
True - out-of-sequence protected
messages will be detected
False - out-of-sequence messages will not
be detected
GSS_C_CONF_FLAG
True - Confidentiality service may be
invoked by calling the gss_wrap
routine
False - No confidentiality service (via
gss_wrap) available. gss_wrap will
provide message encapsulation,
data-origin authentication and
integrity services only.
GSS_C_INTEG_FLAG
True - Integrity service may be invoked by
calling either gss_get_mic or
gss_wrap routines.
False - Per-message integrity service
unavailable.
GSS_C_ANON_FLAG
True - The initiator does not wish to
be authenticated; the src_name
parameter (if requested) contains
an anonymous internal name.
False - The initiator has been
authenticated normally.
GSS_C_PROT_READY_FLAG
True - Protection services (as specified
by the states of the GSS_C_CONF_FLAG
and GSS_C_INTEG_FLAG) are available
if the accompanying major status
return value is either GSS_S_COMPLETE
or GSS_S_CONTINUE_NEEDED.
False - Protection services (as specified
by the states of the GSS_C_CONF_FLAG
and GSS_C_INTEG_FLAG) are available
only if the accompanying major status
return value is GSS_S_COMPLETE.
GSS_C_TRANS_FLAG
True - The resultant security context may
be transferred to other processes via
a call to gss_export_sec_context().
False - The security context is not
transferable.
All other bits should be set to zero.
time_rec Integer, modify, optional
number of seconds for which the context will
remain valid. Specify NULL if not required.
delegated_cred_handle
gss_cred_id_t, modify, optional credential
handle for credentials received from context
initiator. Only valid if deleg_flag in
ret_flags is true, in which case an explicit
credential handle (i.e. not GSS_C_NO_CREDENTIAL)
will be returned; if deleg_flag is false,
gss_accept_context() will set this parameter to
GSS_C_NO_CREDENTIAL. If a credential handle is
returned, the associated resources must be
released by the application after use with a
call to gss_release_cred(). Specify NULL if not
required.
minor_status Integer, modify
Mechanism specific status code.
GSS_S_CONTINUE_NEEDED Indicates that a token from the peer
application is required to complete the
context, and that gss_accept_sec_context must
be called again with that token.
GSS_S_DEFECTIVE_TOKEN Indicates that consistency checks performed on
the input_token failed.
GSS_S_DEFECTIVE_CREDENTIAL Indicates that consistency checks
performed on the credential failed.
GSS_S_NO_CRED The supplied credentials were not valid for context
acceptance, or the credential handle did not
reference any credentials.
GSS_S_CREDENTIALS_EXPIRED The referenced credentials have expired.
GSS_S_BAD_BINDINGS The input_token contains different channel
bindings to those specified via the
input_chan_bindings parameter.
GSS_S_NO_CONTEXT Indicates that the supplied context handle did not
refer to a valid context.
GSS_S_BAD_SIG The input_token contains an invalid MIC.
GSS_S_OLD_TOKEN The input_token was too old. This is a fatal error
during context establishment.
GSS_S_DUPLICATE_TOKEN The input_token is valid, but is a duplicate of
a token already processed. This is a fatal
error during context establishment.
GSS_S_BAD_MECH The received token specified a mechanism that is
not supported by the implementation or the
provided credential.
5.2. gss_acquire_cred
OM_uint32 gss_acquire_cred (
OM_uint32 *minor_status,
const gss_name_t desired_name,
OM_uint32 time_req,
const gss_OID_set desired_mechs,
gss_cred_usage_t cred_usage,
gss_cred_id_t *output_cred_handle,
gss_OID_set *actual_mechs,
OM_uint32 *time_rec)
Purpose: Allows an application to acquire a handle for a pre-existing credential by name. GSS-API implementations must impose a local access-control policy on callers of this routine to prevent unauthorized callers from acquiring credentials to which they are not entitled. This routine is not intended to provide a "login to the network" function, as such a function would involve the creation of new credentials rather than merely acquiring a handle to existing credentials. Such functions, if required, should be defined in implementation-specific extensions to the API. If desired_name is GSS_C_NO_NAME, the call is interpreted as a request for a credential handle that will invoke default behavior when passed to gss_init_sec_context() (if cred_usage is GSS_C_INITIATE or GSS_C_BOTH) or gss_accept_sec_context() (if cred_usage is GSS_C_ACCEPT or GSS_C_BOTH). Mechanisms should honor the desired_mechs parameter, and return a credential that is suitable to use only with the requested mechanisms. An exception to this is the case where one underlying credential element can be shared by multiple mechanisms; in this case it is permissible for an implementation to indicate all mechanisms with which the credential element may be used. If desired_mechs is an empty set, behavior is undefined. This routine is expected to be used primarily by context acceptors, since implementations are likely to provide mechanism-specific ways of obtaining GSS-API initiator credentials from the system login process. Some implementations may therefore not support the acquisition of GSS_C_INITIATE or GSS_C_BOTH credentials via gss_acquire_cred for any name other than GSS_C_NO_NAME, or a name produced by applying either gss_inquire_cred to a valid credential, or gss_inquire_context to an active context. If credential acquisition is time-consuming for a mechanism, the mechanism may choose to delay the actual acquisition until the credential is required (e.g. by gss_init_sec_context or gss_accept_sec_context). Such mechanism-specific implementation decisions should be invisible to the calling application; thus a call of gss_inquire_cred immediately following the call of gss_acquire_cred must return valid credential data, and may therefore incur the overhead of a deferred credential acquisition.
Parameters:
desired_name gss_name_t, read
Name of principal whose credential
should be acquired
time_req Integer, read, optional
number of seconds that credentials
should remain valid. Specify GSS_C_INDEFINITE
to request that the credentials have the maximum
permitted lifetime.
desired_mechs Set of Object IDs, read, optional
set of underlying security mechanisms that
may be used. GSS_C_NO_OID_SET may be used
to obtain an implementation-specific default.
cred_usage gss_cred_usage_t, read
GSS_C_BOTH - Credentials may be used
either to initiate or accept
security contexts.
GSS_C_INITIATE - Credentials will only be
used to initiate security contexts.
GSS_C_ACCEPT - Credentials will only be used to
accept security contexts.
output_cred_handle gss_cred_id_t, modify
The returned credential handle. Resources
associated with this credential handle must
be released by the application after use
with a call to gss_release_cred().
actual_mechs Set of Object IDs, modify, optional
The set of mechanisms for which the
credential is valid. Storage associated
with the returned OID-set must be released by
the application after use with a call to
gss_release_oid_set(). Specify NULL if not
required.
time_rec Integer, modify, optional
Actual number of seconds for which the
returned credentials will remain valid. If the
implementation does not support expiration of
credentials, the value GSS_C_INDEFINITE will
be returned. Specify NULL if not required
minor_status Integer, modify
Mechanism specific status code.
Function value: GSS status code
GSS_S_COMPLETE Successful completion
GSS_S_BAD_MECH Unavailable mechanism requested
GSS_S_BAD_NAMETYPE Type contained within desired_name parameter
is not supported
GSS_S_BAD_NAME Value supplied for desired_name parameter is ill
formed.
GSS_S_CREDENTIALS_EXPIRED The credentials could not be acquired
Because they have expired.
GSS_S_NO_CRED No credentials were found for the specified name.
5.3. gss_add_cred
OM_uint32 gss_add_cred (
OM_uint32 *minor_status,
const gss_cred_id_t input_cred_handle,
const gss_name_t desired_name,
const gss_OID desired_mech,
gss_cred_usage_t cred_usage,
OM_uint32 initiator_time_req,
OM_uint32 acceptor_time_req,
gss_cred_id_t *output_cred_handle,
gss_OID_set *actual_mechs,
OM_uint32 *initiator_time_rec,
OM_uint32 *acceptor_time_rec)
Purpose:
Adds a credential-element to a credential. The credential-element is
identified by the name of the principal to which it refers. GSS-API
implementations must impose a local access-control policy on callers
of this routine to prevent unauthorized callers from acquiring
credential-elements to which they are not entitled. This routine is
not intended to provide a "login to the network" function, as such a
function would involve the creation of new mechanism-specific
authentication data, rather than merely acquiring a GSS-API handle to
existing data. Such functions, if required, should be defined in
implementation-specific extensions to the API.
If desired_name is GSS_C_NO_NAME, the call is interpreted as a request to add a credential element that will invoke default behavior when passed to gss_init_sec_context() (if cred_usage is GSS_C_INITIATE or GSS_C_BOTH) or gss_accept_sec_context() (if cred_usage is GSS_C_ACCEPT or GSS_C_BOTH). This routine is expected to be used primarily by context acceptors, since implementations are likely to provide mechanism-specific ways of obtaining GSS-API initiator credentials from the system login process. Some implementations may therefore not support the acquisition of GSS_C_INITIATE or GSS_C_BOTH credentials via gss_acquire_cred for any name other than GSS_C_NO_NAME, or a name produced by applying either gss_inquire_cred to a valid credential, or gss_inquire_context to an active context. If credential acquisition is time-consuming for a mechanism, the mechanism may choose to delay the actual acquisition until the credential is required (e.g. by gss_init_sec_context or gss_accept_sec_context). Such mechanism-specific implementation decisions should be invisible to the calling application; thus a call of gss_inquire_cred immediately following the call of gss_add_cred must return valid credential data, and may therefore incur the overhead of a deferred credential acquisition. This routine can be used to either compose a new credential containing all credential-elements of the original in addition to the newly-acquire credential-element, or to add the new credential- element to an existing credential. If NULL is specified for the output_cred_handle parameter argument, the new credential-element will be added to the credential identified by input_cred_handle; if a valid pointer is specified for the output_cred_handle parameter, a new credential handle will be created. If GSS_C_NO_CREDENTIAL is specified as the input_cred_handle, gss_add_cred will compose a credential (and set the output_cred_handle parameter accordingly) based on default behavior. That is, the call will have the same effect as if the application had first made a call to gss_acquire_cred(), specifying the same usage and passing GSS_C_NO_NAME as the desired_name parameter to obtain an explicit credential handle embodying default behavior, passed this credential handle to gss_add_cred(), and finally called gss_release_cred() on the first credential handle. If GSS_C_NO_CREDENTIAL is specified as the input_cred_handle parameter, a non-NULL output_cred_handle must be supplied.
Parameters:
minor_status Integer, modify
Mechanism specific status code.
input_cred_handle gss_cred_id_t, read, optional
The credential to which a credential-element
will be added. If GSS_C_NO_CREDENTIAL is
specified, the routine will compose the new
credential based on default behavior (see
description above). Note that, while the
credential-handle is not modified by
gss_add_cred(), the underlying credential
will be modified if output_credential_handle
is NULL.
desired_name gss_name_t, read.
Name of principal whose credential
should be acquired.
desired_mech Object ID, read
Underlying security mechanism with which the
credential may be used.
cred_usage gss_cred_usage_t, read
GSS_C_BOTH - Credential may be used
either to initiate or accept
security contexts.
GSS_C_INITIATE - Credential will only be
used to initiate security
contexts.
GSS_C_ACCEPT - Credential will only be used to
accept security contexts.
initiator_time_req Integer, read, optional
number of seconds that the credential
should remain valid for initiating security
contexts. This argument is ignored if the
composed credentials are of type GSS_C_ACCEPT.
Specify GSS_C_INDEFINITE to request that the
credentials have the maximum permitted
initiator lifetime.
acceptor_time_req Integer, read, optional
number of seconds that the credential
should remain valid for accepting security
contexts. This argument is ignored if the
composed credentials are of type GSS_C_INITIATE.
Specify GSS_C_INDEFINITE to request that the
credentials have the maximum permitted initiator
lifetime.
output_cred_handle gss_cred_id_t, modify, optional
The returned credential handle, containing
the new credential-element and all the
credential-elements from input_cred_handle.
If a valid pointer to a gss_cred_id_t is
supplied for this parameter, gss_add_cred
creates a new credential handle containing all
credential-elements from the input_cred_handle
and the newly acquired credential-element; if
NULL is specified for this parameter, the newly
acquired credential-element will be added
to the credential identified by input_cred_handle.
The resources associated with any credential
handle returned via this parameter must be
released by the application after use with a
call to gss_release_cred().
actual_mechs Set of Object IDs, modify, optional
The complete set of mechanisms for which
the new credential is valid. Storage for
the returned OID-set must be freed by the
application after use with a call to
gss_release_oid_set(). Specify NULL if
not required.
initiator_time_rec Integer, modify, optional
Actual number of seconds for which the
returned credentials will remain valid for
initiating contexts using the specified
mechanism. If the implementation or mechanism
does not support expiration of credentials, the
value GSS_C_INDEFINITE will be returned. Specify
NULL if not required
acceptor_time_rec Integer, modify, optional
Actual number of seconds for which the
returned credentials will remain valid for
accepting security contexts using the specified
mechanism. If the implementation or mechanism
does not support expiration of credentials, the
value GSS_C_INDEFINITE will be returned. Specify
NULL if not required
Function value: GSS status code
GSS_S_COMPLETE Successful completion
GSS_S_BAD_MECH Unavailable mechanism requested
GSS_S_BAD_NAMETYPE Type contained within desired_name parameter
is not supported
GSS_S_BAD_NAME Value supplied for desired_name parameter is
ill-formed.
GSS_S_DUPLICATE_ELEMENT The credential already contains an element
for the requested mechanism with overlapping
usage and validity period.
GSS_S_CREDENTIALS_EXPIRED The required credentials could not be
added because they have expired.
GSS_S_NO_CRED No credentials were found for the specified name.
5.4. gss_add_oid_set_member
OM_uint32 gss_add_oid_set_member (
OM_uint32 *minor_status,
const gss_OID member_oid,
gss_OID_set *oid_set)
Purpose:
Add 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.
The oid_set parameter must refer to an OID-set that was created by
GSS-API (e.g. a set returned by gss_create_empty_oid_set()). GSS-API
creates a copy of the member_oid and inserts this copy into the set,
expanding the storage allocated to the OID-set's elements array if
necessary. The routine may add the new member OID anywhere within
the elements array, and implementations should verify that the new
member_oid is not already contained within the elements array; if the
member_oid is already present, the oid_set should remain unchanged.
Parameters:
minor_status Integer, modify
Mechanism specific status code
member_oid Object ID, read
The object identifier to copied into
the set.
oid_set Set of Object ID, modify
The set in which the object identifier
should be inserted.
Function value: GSS status code
GSS_S_COMPLETE Successful completion
5.5. gss_canonicalize_name
OM_uint32 gss_canonicalize_name (
OM_uint32 *minor_status,
const gss_name_t input_name,
const gss_OID mech_type,
gss_name_t *output_name)
Purpose:
Generate a canonical mechanism name (MN) from an arbitrary internal
name. The mechanism name is the name that would be returned to a
context acceptor on successful authentication of a context where the
initiator used the input_name in a successful call to
gss_acquire_cred, specifying an OID set containing <mech_type> as its
only member, followed by a call to gss_init_sec_context, specifying
<mech_type> as the authentication mechanism.
Parameters:
minor_status Integer, modify
Mechanism specific status code
input_name gss_name_t, read
The name for which a canonical form is
desired
mech_type Object ID, read
The authentication mechanism for which the
canonical form of the name is desired. The
desired mechanism must be specified explicitly;
no default is provided.
output_name gss_name_t, modify
The resultant canonical name. Storage
associated with this name must be freed by
the application after use with a call to
gss_release_name().
Function value: GSS status code
GSS_S_COMPLETE Successful completion.
GSS_S_BAD_MECH The identified mechanism is not supported.
GSS_S_BAD_NAMETYPE The provided internal name contains no elements
that could be processed by the specified
mechanism.
GSS_S_BAD_NAME The provided internal name was ill-formed.
5.6. gss_compare_name
OM_uint32 gss_compare_name (
OM_uint32 *minor_status,
const gss_name_t name1,
const gss_name_t name2,
int *name_equal)
Purpose:
Allows an application to compare two internal-form names to determine
whether they refer to the same entity.
If either name presented to gss_compare_name denotes an anonymous
principal, the routines should indicate that the two names do not
refer to the same identity.
Parameters:
minor_status Integer, modify
Mechanism specific status code.
name1 gss_name_t, read
internal-form name
name2 gss_name_t, read
internal-form name
name_equal boolean, modify
non-zero - names refer to same entity
zero - names refer to different entities
(strictly, the names are not known
to refer to the same identity).
Function value: GSS status code
GSS_S_COMPLETE Successful completion
GSS_S_BAD_NAMETYPE The two names were of incomparable types.
GSS_S_BAD_NAME One or both of name1 or name2 was ill-formed.
5.7. gss_context_time
OM_uint32 gss_context_time (
OM_uint32 *minor_status,
const gss_ctx_id_t context_handle,
OM_uint32 *time_rec)
Purpose:
Determines the number of seconds for which the specified context will
remain valid.
Parameters:
minor_status Integer, modify
Implementation specific status code.
context_handle gss_ctx_id_t, read
Identifies the context to be interrogated.
time_rec Integer, modify
Number of seconds that the context will remain
valid. If the context has already expired,
zero will be returned.
Function value: GSS status code
GSS_S_COMPLETE Successful completion
GSS_S_CONTEXT_EXPIRED The context has already expired
GSS_S_NO_CONTEXT The context_handle parameter did not identify
a valid context
5.8. gss_create_empty_oid_set
OM_uint32 gss_create_empty_oid_set ( OM_uint32 *minor_status, gss_OID_set *oid_set) Purpose: Create 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. Parameters: minor_status Integer, modify Mechanism specific status code oid_set Set of Object IDs, modify The empty object identifier set. The routine will allocate the gss_OID_set_desc object, which the application must free after use with a call to gss_release_oid_set(). Function value: GSS status code GSS_S_COMPLETE Successful completion5.9. gss_delete_sec_context
OM_uint32 gss_delete_sec_context ( OM_uint32 *minor_status, gss_ctx_id_t *context_handle, gss_buffer_t output_token) Purpose: Delete a security context. gss_delete_sec_context will delete the local data structures associated with the specified security context, and may generate an output_token, which when passed to the peer gss_process_context_token will instruct it to do likewise. If no token is required by the mechanism, the GSS-API should set the length field of the output_token (if provided) to zero. No further security services may be obtained using the context specified by context_handle.
In addition to deleting established security contexts,
gss_delete_sec_context must also be able to delete "half-built"
security contexts resulting from an incomplete sequence of
gss_init_sec_context()/gss_accept_sec_context() calls.
The output_token parameter is retained for compatibility with version
1 of the GSS-API. It is recommended that both peer applications
invoke gss_delete_sec_context passing the value GSS_C_NO_BUFFER for
the output_token parameter, indicating that no token is required, and
that gss_delete_sec_context should simply delete local context data
structures. If the application does pass a valid buffer to
gss_delete_sec_context, mechanisms are encouraged to return a zero-
length token, indicating that no peer action is necessary, and that
no token should be transferred by the application.
Parameters:
minor_status Integer, modify
Mechanism specific status code.
context_handle gss_ctx_id_t, modify
context handle identifying context to delete.
After deleting the context, the GSS-API will set
this context handle to GSS_C_NO_CONTEXT.
output_token buffer, opaque, modify, optional
token to be sent to remote application to
instruct it to also delete the context. It
is recommended that applications specify
GSS_C_NO_BUFFER for this parameter, requesting
local deletion only. If a buffer parameter is
provided by the application, the mechanism may
return a token in it; mechanisms that implement
only local deletion should set the length field of
this token to zero to indicate to the application
that no token is to be sent to the peer.
Function value: GSS status code
GSS_S_COMPLETE Successful completion
GSS_S_NO_CONTEXT No valid context was supplied
5.10. gss_display_name
OM_uint32 gss_display_name ( OM_uint32 *minor_status, const gss_name_t input_name, gss_buffer_t output_name_buffer, gss_OID *output_name_type) Purpose: Allows an application to obtain a textual representation of an opaque internal-form name for display purposes. The syntax of a printable name is defined by the GSS-API implementation. If input_name denotes an anonymous principal, the implementation should return the gss_OID value GSS_C_NT_ANONYMOUS as the output_name_type, and a textual name that is syntactically distinct from all valid supported printable names in output_name_buffer. If input_name was created by a call to gss_import_name, specifying GSS_C_NO_OID as the name-type, implementations that employ lazy conversion between name types may return GSS_C_NO_OID via the output_name_type parameter. Parameters: minor_status Integer, modify Mechanism specific status code. input_name gss_name_t, read name to be displayed output_name_buffer buffer, character-string, modify buffer to receive textual name string. The application must free storage associated with this name after use with a call to gss_release_buffer(). output_name_type Object ID, modify, optional The type of the returned name. The returned gss_OID will be a pointer into static storage, and should be treated as read-only by the caller (in particular, the application should not attempt to free it). Specify NULL if not required.
Function value: GSS status code GSS_S_COMPLETE Successful completion GSS_S_BAD_NAME input_name was ill-formed5.11. gss_display_status
OM_uint32 gss_display_status ( OM_uint32 *minor_status, OM_uint32 status_value, int status_type, const gss_OID mech_type, OM_uint32 *message_context, gss_buffer_t status_string) Purpose: Allows an application to obtain a textual representation of a GSS-API status code, for display to the user or for logging purposes. Since some status values may indicate multiple conditions, applications may need to call gss_display_status multiple times, each call generating a single text string. The message_context parameter is used by gss_display_status to store state information about which error messages have already been extracted from a given status_value; message_context must be initialized to 0 by the application prior to the first call, and gss_display_status will return a non-zero value in this parameter if there are further messages to extract. The message_context parameter contains all state information required by gss_display_status in order to extract further messages from the status_value; even when a non-zero value is returned in this parameter, the application is not required to call gss_display_status again unless subsequent messages are desired. The following code extracts all messages from a given status code and prints them to stderr: OM_uint32 message_context; OM_uint32 status_code; OM_uint32 maj_status; OM_uint32 min_status; gss_buffer_desc status_string; ... message_context = 0; do {
maj_status = gss_display_status (
&min_status,
status_code,
GSS_C_GSS_CODE,
GSS_C_NO_OID,
&message_context,
&status_string)
fprintf(stderr,
"%.*s\n",
(int)status_string.length,
(char *)status_string.value);
gss_release_buffer(&min_status, &status_string);
} while (message_context != 0);
Parameters:
minor_status Integer, modify
Mechanism specific status code.
status_value Integer, read
Status value to be converted
status_type Integer, read
GSS_C_GSS_CODE - status_value is a GSS status
code
GSS_C_MECH_CODE - status_value is a mechanism
status code
mech_type Object ID, read, optional
Underlying mechanism (used to interpret a
minor status value) Supply GSS_C_NO_OID to
obtain the system default.
message_context Integer, read/modify
Should be initialized to zero by the
application prior to the first call.
On return from gss_display_status(),
a non-zero status_value parameter indicates
that additional messages may be extracted
from the status code via subsequent calls
to gss_display_status(), passing the same
status_value, status_type, mech_type, and
message_context parameters.
status_string buffer, character string, modify
textual interpretation of the status_value.
Storage associated with this parameter must
be freed by the application after use with
a call to gss_release_buffer().
Function value: GSS status code
GSS_S_COMPLETE Successful completion
GSS_S_BAD_MECH Indicates that translation in accordance with
an unsupported mechanism type was requested
GSS_S_BAD_STATUS The status value was not recognized, or the
status type was neither GSS_C_GSS_CODE nor
GSS_C_MECH_CODE.
5.12. gss_duplicate_name
OM_uint32 gss_duplicate_name (
OM_uint32 *minor_status,
const gss_name_t src_name,
gss_name_t *dest_name)
Purpose:
Create an exact duplicate of the existing internal name src_name.
The new dest_name will be independent of src_name (i.e. src_name and
dest_name must both be released, and the release of one shall not
affect the validity of the other).
Parameters:
minor_status Integer, modify
Mechanism specific status code.
src_name gss_name_t, read
internal name to be duplicated.
dest_name gss_name_t, modify
The resultant copy of <src_name>.
Storage associated with this name must
be freed by the application after use
with a call to gss_release_name().
Function value: GSS status code GSS_S_COMPLETE Successful completion GSS_S_BAD_NAME The src_name parameter was ill-formed.5.13. gss_export_name
OM_uint32 gss_export_name ( OM_uint32 *minor_status, const gss_name_t input_name, gss_buffer_t exported_name) Purpose: To produce a canonical contiguous string representation of a mechanism name (MN), suitable for direct comparison (e.g. with memcmp) for use in authorization functions (e.g. matching entries in an access-control list). The <input_name> parameter must specify a valid MN (i.e. an internal name generated by gss_accept_sec_context or by gss_canonicalize_name). Parameters: minor_status Integer, modify Mechanism specific status code input_name gss_name_t, read The MN to be exported exported_name gss_buffer_t, octet-string, modify The canonical contiguous string form of <input_name>. Storage associated with this string must freed by the application after use with gss_release_buffer(). Function value: GSS status code GSS_S_COMPLETE Successful completion GSS_S_NAME_NOT_MN The provided internal name was not a mechanism name. GSS_S_BAD_NAME The provided internal name was ill-formed. GSS_S_BAD_NAMETYPE The internal name was of a type not supported by the GSS-API implementation.
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