NAME

SYNOPSIS

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);

DESCRIPTION

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:

• 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 actual_mech_type parameter is 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. In particular, if the application has requested a service such as delegation or anonymous authentication via the req_flags argument, and such a service is unavailable from the underlying mechanism, gss_init_sec_context() should generate a token that will not provide the service, and indicate via the ret_flags argument that the service will not be supported. The application may choose to abort the context establishment by calling gss_delete_sec_context(3) (if it cannot continue in the absence of the service), or it may choose to transmit the token and continue context establishment (if the service was merely desired but not mandatory).
• 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_init_sec_context() returns, whether or not the context is fully established.
• GSS-API implementations that support per-message protection are encouraged to 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). However, applications should not rely on this behavior as the flag was not defined in Version 1 of the GSS-API. Instead, applications should determine what per-message services are available 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.

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(3) ).

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

minor_status

Mechanism specific status code.

initiator_cred_handle

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

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

Name of target

mech_type

Object ID of desired mechanism. Supply GSS_C_NO_OID to obtain an implementation specific default

req_flags

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. The flags are:

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(3) or gss_get_mic(3)

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(3))

False

No per-message confidentiality service is required.

GSS_C_INTEG_FLAG

True

Request that integrity service be made available (via gss_wrap(3) or gss_get_mic(3))

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.

time_req

Desired number of seconds for which context should remain valid. Supply 0 to request a default validity period.

input_chan_bindings

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

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

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

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(3).

ret_flags

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. The flags are:

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(3) routine

False

No confidentiality service (via gss_wrap(3)) available. gss_wrap(3) 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(3) or gss_wrap(3) 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.

time_rec

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.

RETURN VALUES

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.

SEE ALSO

STANDARDS

RFC 2743

Generic Security Service Application Program Interface Version 2, Update 1

RFC 2744

Generic Security Service API Version 2 : C-bindings

HISTORY

AUTHORS

COPYRIGHT

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