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3.6 Context-Level Routines

   GSS-API Context-Level Routines

   Routine                         Function
   -------                         --------
   gss_init_sec_context            Initiate a security context with
                                   a peer application.
   gss_accept_sec_context          Accept a security context
                                   initiated by a peer application.
   gss_delete_sec_context          Discard a security context.
   gss_process_context_token       Process a token on a security
                                   context from a peer application.
   gss_context_time                Determine for how long a context
                                   will remain valid.
   gss_inquire_context             Obtain information about a
                                   security context.
   gss_wrap_size_limit             Determine token-size limit for
                                   gss_wrap on a context.
   gss_export_sec_context          Transfer a security context to
                                   another process.
   gss_import_sec_context          Import a transferred context.

gss_init_sec_context

— Function: OM_uint32 gss_init_sec_context (OM_uint32 * minor_status, const gss_cred_id_t initiator_cred_handle, gss_ctx_id_t * context_handle, const gss_name_t target_name, const gss_OID mech_type, OM_uint32 req_flags, OM_uint32 time_req, const gss_channel_bindings_t input_chan_bindings, const gss_buffer_t input_token, gss_OID * actual_mech_type, gss_buffer_t output_token, OM_uint32 * ret_flags, OM_uint32 * time_rec)

minor_status: (integer, modify) Mechanism specific status code.

initiator_cred_handle: (gss_cred_id_t, read, optional) Handle for credentials claimed. Supply GSS_C_NO_CREDENTIAL to act as a default initiator principal. If no default initiator is defined, the function will return GSS_S_NO_CRED.

context_handle: (gss_ctx_id_t, read/modify) Context handle for new context. Supply GSS_C_NO_CONTEXT for first call; use value returned by first call in continuation calls. Resources associated with this context-handle must be released by the application after use with a call to gss_delete_sec_context().

target_name: (gss_name_t, read) Name of target.

mech_type: (OID, read, optional) Object ID of desired mechanism. Supply GSS_C_NO_OID to obtain an implementation specific default.

req_flags: (bit-mask, read) Contains various independent flags, each of which requests that the context support a specific service option. Symbolic names are provided for each flag, and the symbolic names corresponding to the required flags should be logically-ORed together to form the bit-mask value. See below for the flags.

time_req: (Integer, read, optional) Desired number of seconds for which context should remain valid. Supply 0 to request a default validity period.

input_chan_bindings: (channel bindings, read, optional) Application-specified bindings. Allows application to securely bind channel identification information to the security context. Specify GSS_C_NO_CHANNEL_BINDINGS if channel bindings are not used.

input_token: (buffer, opaque, read, optional) Token received from peer application. Supply GSS_C_NO_BUFFER, or a pointer to a buffer containing the value GSS_C_EMPTY_BUFFER on initial call.

actual_mech_type: (OID, modify, optional) Actual mechanism used. The OID returned via this parameter will be a pointer to static storage that should be treated as read-only; In particular the application should not attempt to free it. Specify NULL if not required.

output_token: (buffer, opaque, modify) Token to be sent to peer application. If the length field of the returned buffer is zero, no token need be sent to the peer application. Storage associated with this buffer must be freed by the application after use 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. Specify NULL if not required. 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. See below for the flags.

time_rec: (Integer, modify, optional) Number of seconds for which the context will remain valid. If the implementation does not support context expiration, the value GSS_C_INDEFINITE will be returned. Specify NULL if not required.

Initiates the establishment of a security context between the application and a remote peer. Initially, the input_token parameter should be specified either as GSS_C_NO_BUFFER, or as a pointer to a gss_buffer_desc object whose length field contains the value zero. The routine may return a output_token which should be transferred to the peer application, where the peer application will present it to gss_accept_sec_context. If no token need be sent, gss_init_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_init_sec_context will return a status containing the supplementary information bit GSS_S_CONTINUE_NEEDED. In this case, gss_init_sec_context should be called again when the reply token is received from the peer application, passing the reply token to gss_init_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_init_sec_context within a loop:

          int context_established = 0;
          gss_ctx_id_t context_hdl = GSS_C_NO_CONTEXT;
                 ...
          input_token->length = 0;
          
          while (!context_established) {
            maj_stat = gss_init_sec_context(&min_stat,
                                            cred_hdl,
                                            &context_hdl,
                                            target_name,
                                            desired_mech,
                                            desired_services,
                                            desired_time,
                                            input_bindings,
                                            input_token,
                                            &actual_mech,
                                            output_token,
                                            &actual_services,
                                            &actual_time);
            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;
            };
          
            if (maj_stat & GSS_S_CONTINUE_NEEDED) {
              receive_token_from_peer(input_token);
            } else {
              context_established = 1;
            };
          };

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:

If the initial call of gss_init_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 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.

The req_flags values:

GSS_C_DELEG_FLAG
  • True - Delegate credentials to remote peer.
  • False - Don't delegate.

GSS_C_MUTUAL_FLAG
  • True - Request that remote peer authenticate itself.
  • False - Authenticate self to remote peer only.

GSS_C_REPLAY_FLAG
  • True - Enable replay detection for messages protected with gss_wrap or gss_get_mic.
  • False - Don't attempt to detect replayed messages.

GSS_C_SEQUENCE_FLAG
  • True - Enable detection of out-of-sequence protected messages.
  • False - Don't attempt to detect out-of-sequence messages.

GSS_C_CONF_FLAG
  • True - Request that confidentiality service be made available (via gss_wrap).
  • False - No per-message confidentiality service is required.

GSS_C_INTEG_FLAG
  • True - Request that integrity service be made available (via gss_wrap or gss_get_mic).
  • False - No per-message integrity service is required.

GSS_C_ANON_FLAG
  • True - Do not reveal the initiator's identity to the acceptor.
  • False - Authenticate normally.

The ret_flags values:

GSS_C_DELEG_FLAG
  • True - Credentials were delegated to the remote peer.
  • False - No credentials were delegated.

GSS_C_MUTUAL_FLAG
  • True - The remote peer has authenticated itself.
  • False - Remote peer has not authenticated itself.

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 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's identity has not been revealed, and will not be revealed if any emitted token is passed to the acceptor.
  • False - The initiator's identity has been or will be 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 for use 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.

Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_CONTINUE_NEEDED: Indicates that a token from the peer application is required to complete the context, and that gss_init_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 initiation, 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_BAD_SIG: The input_token contains an invalid MIC, or a MIC that could not be verified.

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_NO_CONTEXT: Indicates that the supplied context handle did not refer to a valid context.

GSS_S_BAD_NAMETYPE: The provided target_name parameter contained an invalid or unsupported type of name.

GSS_S_BAD_NAME: The provided target_name parameter was ill-formed.

GSS_S_BAD_MECH: The specified mechanism is not supported by the provided credential, or is unrecognized by the implementation.

gss_accept_sec_context

— Function: 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, 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)

minor_status: (Integer, modify) Mechanism specific status code.

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. See below for the flags.

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_sec_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.

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.

The ret_flags values:

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.

Return value:

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.

gss_delete_sec_context

— Function: OM_uint32 gss_delete_sec_context (OM_uint32 * minor_status, gss_ctx_id_t * context_handle, gss_buffer_t output_token)

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.

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.

Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_NO_CONTEXT: No valid context was supplied.

gss_process_context_token

— Function: OM_uint32 gss_process_context_token (OM_uint32 * minor_status, const gss_ctx_id_t context_handle, const gss_buffer_t token_buffer)

minor_status: (Integer, modify) Implementation specific status code.

context_handle: (gss_ctx_id_t, read) Context handle of context on which token is to be processed

token_buffer: (buffer, opaque, read) Token to process.

Provides a way to pass an asynchronous token to the security service. Most context-level tokens are emitted and processed synchronously by gss_init_sec_context and gss_accept_sec_context, and the application is informed as to whether further tokens are expected by the GSS_C_CONTINUE_NEEDED major status bit. Occasionally, a mechanism may need to emit a context-level token at a point when the peer entity is not expecting a token. For example, the initiator's final call to gss_init_sec_context may emit a token and return a status of GSS_S_COMPLETE, but the acceptor's call to gss_accept_sec_context may fail. The acceptor's mechanism may wish to send a token containing an error indication to the initiator, but the initiator is not expecting a token at this point, believing that the context is fully established. Gss_process_context_token provides a way to pass such a token to the mechanism at any time.

Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_DEFECTIVE_TOKEN: Indicates that consistency checks performed on the token failed.

GSS_S_NO_CONTEXT: The context_handle did not refer to a valid context.

gss_context_time

— Function: OM_uint32 gss_context_time (OM_uint32 * minor_status, const gss_ctx_id_t context_handle, OM_uint32 * time_rec)

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.

Determines the number of seconds for which the specified context will remain valid.

Return value:

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

gss_inquire_context

— Function: OM_uint32 gss_inquire_context (OM_uint32 * minor_status, const gss_ctx_id_t context_handle, gss_name_t * src_name, gss_name_t * targ_name, OM_uint32 * lifetime_rec, gss_OID * mech_type, OM_uint32 * ctx_flags, int * locally_initiated, int * open)

minor_status: (Integer, modify) Mechanism specific status code.

context_handle: (gss_ctx_id_t, read) A handle that refers to the security context.

src_name: (gss_name_t, modify, optional) The name of the context initiator. If the context was established using anonymous authentication, and if the application invoking gss_inquire_context is the context acceptor, an anonymous name will be returned. Storage associated with this name must be freed by the application after use with a call to gss_release_name(). Specify NULL if not required.

targ_name: (gss_name_t, modify, optional) The name of the context acceptor. Storage associated with this name must be freed by the application after use with a call to gss_release_name(). If the context acceptor did not authenticate itself, and if the initiator did not specify a target name in its call to gss_init_sec_context(), the value GSS_C_NO_NAME will be returned. Specify NULL if not required.

lifetime_rec: (Integer, modify, optional) The number of seconds for which the context will remain valid. If the context has expired, this parameter will be set to zero. If the implementation does not support context expiration, the value GSS_C_INDEFINITE will be returned. Specify NULL if not required.

mech_type: (gss_OID, modify, optional) The security mechanism providing the context. The returned OID will be a pointer to static storage that should be treated as read-only by the application; in particular the application should not attempt to free it. Specify NULL if not required.

ctx_flags: (bit-mask, modify, optional) Contains various independent flags, each of which indicates that the context supports (or is expected to support, if ctx_open is false) 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. See below for the flags.

locally_initiated: (Boolean, modify) Non-zero if the invoking application is the context initiator. Specify NULL if not required.

open: (Boolean, modify) Non-zero if the context is fully established; Zero if a context-establishment token is expected from the peer application. Specify NULL if not required.

Obtains information about a security context. The caller must already have obtained a handle that refers to the context, although the context need not be fully established.

The ctx_flags values:

GSS_C_DELEG_FLAG
  • True - Credentials were delegated from the initiator to the acceptor.
  • False - No credentials were delegated.

GSS_C_MUTUAL_FLAG
  • True - The acceptor was authenticated to the initiator.
  • False - The acceptor did not authenticate itself.

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 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's identity will not be revealed to the acceptor. 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 for use.
  • False - Protection services (as specified by the states of the GSS_C_CONF_FLAG and GSS_C_INTEG_FLAG) are available only if the context is fully established (i.e. if the open parameter is non-zero).

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.
Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_NO_CONTEXT: The referenced context could not be accessed.

gss_wrap_size_limit

— Function: OM_uint32 gss_wrap_size_limit (OM_uint32 * minor_status, const gss_ctx_id_t context_handle, int conf_req_flag, gss_qop_t qop_req, OM_uint32 req_output_size, OM_uint32 * max_input_size)

minor_status: (Integer, modify) Mechanism specific status code.

context_handle: (gss_ctx_id_t, read) A handle that refers to the security over which the messages will be sent.

conf_req_flag: (Boolean, read) Indicates whether gss_wrap will be asked to apply confidentiality protection in addition to integrity protection. See the routine description for gss_wrap for more details.

qop_req: (gss_qop_t, read) Indicates the level of protection that gss_wrap will be asked to provide. See the routine description for gss_wrap for more details.

req_output_size: (Integer, read) The desired maximum size for tokens emitted by gss_wrap.

max_input_size: (Integer, modify) The maximum input message size that may be presented to gss_wrap in order to guarantee that the emitted token shall be no larger than req_output_size bytes.

Allows an application to determine the maximum message size that, if presented to gss_wrap with the same conf_req_flag and qop_req parameters, will result in an output token containing no more than req_output_size bytes.

This call is intended for use by applications that communicate over protocols that impose a maximum message size. It enables the application to fragment messages prior to applying protection.

GSS-API implementations are recommended but not required to detect invalid QOP values when gss_wrap_size_limit() is called. This routine guarantees only a maximum message size, not the availability of specific QOP values for message protection.

Successful completion of this call does not guarantee that gss_wrap will be able to protect a message of length max_input_size bytes, since this ability may depend on the availability of system resources at the time that gss_wrap is called. However, if the implementation itself imposes an upper limit on the length of messages that may be processed by gss_wrap, the implementation should not return a value via max_input_bytes that is greater than this length.

Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_NO_CONTEXT: The referenced context could not be accessed.

GSS_S_CONTEXT_EXPIRED: The context has expired.

GSS_S_BAD_QOP: The specified QOP is not supported by the mechanism.

gss_export_sec_context

— Function: OM_uint32 gss_export_sec_context (OM_uint32 * minor_status, gss_ctx_id_t * context_handle, gss_buffer_t interprocess_token)

minor_status: (Integer, modify) Mechanism specific status code.

context_handle: (gss_ctx_id_t, modify) Context handle identifying the context to transfer.

interprocess_token: (buffer, opaque, modify) Token to be transferred to target process. Storage associated with this token must be freed by the application after use with a call to gss_release_buffer().

Provided to support the sharing of work between multiple processes. This routine will typically be used by the context-acceptor, in an application where a single process receives incoming connection requests and accepts security contexts over them, then passes the established context to one or more other processes for message exchange. gss_export_sec_context() deactivates the security context for the calling process and creates an interprocess token which, when passed to gss_import_sec_context in another process, will re-activate the context in the second process. Only a single instantiation of a given context may be active at any one time; a subsequent attempt by a context exporter to access the exported security context will fail.

The implementation may constrain the set of processes by which the interprocess token may be imported, either as a function of local security policy, or as a result of implementation decisions. For example, some implementations may constrain contexts to be passed only between processes that run under the same account, or which are part of the same process group.

The interprocess token may contain security-sensitive information (for example cryptographic keys). While mechanisms are encouraged to either avoid placing such sensitive information within interprocess tokens, or to encrypt the token before returning it to the application, in a typical object-library GSS-API implementation this may not be possible. Thus the application must take care to protect the interprocess token, and ensure that any process to which the token is transferred is trustworthy.

If creation of the interprocess token is successful, the implementation shall deallocate all process-wide resources associated with the security context, and set the context_handle to GSS_C_NO_CONTEXT. In the event of an error that makes it impossible to complete the export of the security context, the implementation must not return an interprocess token, and should strive to leave the security context referenced by the context_handle parameter untouched. If this is impossible, it is permissible for the implementation to delete the security context, providing it also sets the context_handle parameter to GSS_C_NO_CONTEXT.

Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_CONTEXT_EXPIRED: The context has expired.

GSS_S_NO_CONTEXT: The context was invalid.

GSS_S_UNAVAILABLE: The operation is not supported.

gss_import_sec_context

— Function: OM_uint32 gss_import_sec_context (OM_uint32 * minor_status, const gss_buffer_t interprocess_token, gss_ctx_id_t * context_handle)

minor_status: (Integer, modify) Mechanism specific status code.

interprocess_token: (buffer, opaque, modify) Token received from exporting process

context_handle: (gss_ctx_id_t, modify) Context handle of newly reactivated context. Resources associated with this context handle must be released by the application after use with a call to gss_delete_sec_context().

Allows a process to import a security context established by another process. A given interprocess token may be imported only once. See gss_export_sec_context.

Return value:

GSS_S_COMPLETE: Successful completion.

GSS_S_NO_CONTEXT: The token did not contain a valid context reference.

GSS_S_DEFECTIVE_TOKEN: The token was invalid.

GSS_S_UNAVAILABLE: The operation is unavailable.

GSS_S_UNAUTHORIZED: Local policy prevents the import of this context by the current process.