gss_init_sec_context — Establish a security context

C Prototype

OM_uint32 gss_init_sec_context(
        OM_uint32               * minor_status,
        gss_cred_id_t             claimant_cred_handle,
        gss_ctx_id_t            * context_handle,
        gss_name_t                target_name,
        gss_OID                   mech_type,
        OM_uint32                 req_flags,
        OM_uint32                 time_req,
        gss_channel_bindings_t    input_chan_bindings,
        gss_buffer_t              input_token,
        gss_OID                 * actual_mech_type,
        gss_buffer_t              output_token,
        OM_uint32               * ret_flags,
        OM_uint32               * time_rec );

Arguments

minor_status (output)		An implementation-specific status code.
claimant_cred_handle (input)		A handle for credentials claimed. Supply GSS_C_NO_CREDENTIAL to act as a default initiator principal. If no default initiator is defined, the routine will return GSS_S_NO_CRED.
context_handle (input/output)		The context handle for the new context. Supply GSS_C_NO_CONTEXT for the first call; use the value returned by the 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 (input)		The name of the target.
mech_type (input)		The object ID of the desired mechanism. Supply GSS_C_NOOID to obtain A mechanism-specific default.
req_flags (input)		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. Valid values are: GSS_C_DELEG_FLAG TRUE — Delegate credentials to the remote peer. FALSE — Do not delegate. GSS_C_MUTUAL_FLAG TRUE — Request that the remote peer authenticate itself.FALSE — Authenticate self to the remote peer only. GSS_C_REPLAY_FLAG TRUE — Enable replay detection for messages protected with `gss_wrap` or `gss_get_mic`.FALSE — Do not attempt to detect replayed messages. GSS_C_SEQUENCE_FLAG TRUE — Enable detection of out-of-sequence protected messages.FALSE — Do not attempt to detect out-of-sequence messages. GSS_C_CONF_FLAG TRUE — Request that confidentiality service be made available (by calling `gss_wrap`).FALSE — No per-message confidentiality service is required. GSS_C_INTEG_FLAG TRUE — Request that integrity service be made available (by calling either `gss_get_mic` or `gss_wrap`).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 (input)		The desired number of seconds for which the context should remain valid. Supply zero to request a default validity period.
input_chan_bindings (input)		Application-specified bindings. Allows the 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 (input)		The token received from the peer application. Supply GSS_C_NO_BUFFER, or a pointer to a buffer containing the value GSS_C_EMPTY_BUFFER on the initial call.
actual_mech_type (output)		The actual mechanism used. The OID returned via this argument 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 (output)		The token to be sent to the 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 (output)		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 — The 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 the `gss_wrap` routine.FALSE — No confidentiality service (via `gss_wrap`) is available. The `gss_wrap` routine 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 is 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 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_S_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 (output)		The number of seconds for which the context will remain valid. If the implementation does not support credential expiration, the value GSS_C_INDEFINITE will be returned. Specify NULL if not required.

Description

This routine indicates the establishment of a security context between the application and a remote peer. Initially, the input_token argument 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 an output_token that 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 token to gss_init_sec_context via the input_token arguments.

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 status that indicates the value GSS_S_CONTINUE_NEEDED, the context is not fully established and the following restrictions apply to the output arguments:

The value returned via the time_rec argument is undefined unless the accompanying ret_flags argument 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 argument is undefined until the routine returns a 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_GLAG, GSS_C_INTEG_FLAG and GSS_C_ANON_FLAG bits returned via the ret_flags argument 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 generates a token that will not provide the service, and indicates 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 (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 indicate the actual state at the time gss_init_sec_context returns, whether or not the context is fully established.
GSSAPI 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 (that is, 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 GSSAPI. 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.

If the initial call of gss_init_sec_context fails, a context object is not created, and the value of the context_handle argument is set to GSS_C_NO_CONTEXT to indicate this.

During context establishment, the informational status bits GSS_OLD_TOKEN and GSS_S_DUPLICATE_TOKEN indicate fatal errors, and GSSAPI mechanisms return them in association with a routine error of GSS_S_FAILURE. This requirement for pairing did not exist in Version 1 of the GSSAPI specification, so applications that wish to run over Version 1 implementations must special-case these codes.

Return Values

This routine returns one of the following GSS status codes:

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` argument.
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` argument contained an invalid or unsupported type of name.
GSS_S_BAD_NAME	The provided `target_name` argument was ill formed.
GSS_S_BAD_MECH	The specified mechanism is not supported by the provided credential, or is unrecognized by the implementation.

gss_init_sec_context — Establish a security context

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C Prototype

Arguments

Description

Return Values