- verify a message with attached cryptographic message
cc [ flag... ] file... -lgss [ library... ] #include <gssapi/gssapi.h> OM_uint32 gss_unwrap(OM_uint32 *minor_status, const gss_ctx_id_t context_handle, const gss_buffer_t input_message_buffer, gss_buffer_t output_message_buffer, int *conf_state, gss_qop_t *qop_state);
The gss_unwrap() function converts a message previously protected by gss_wrap(3GSS) back to a usable form, verifying the embedded MIC. The conf_state parameter indicates whether the message was encrypted; the qop_state parameter indicates the strength of protection that was used to provide the confidentiality and integrity services.
Since some application-level protocols may wish to use tokens emitted by gss_wrap(3GSS) to provide secure framing, the GSS-API supports the wrapping and unwrapping of zero-length messages.
The parameter descriptions for gss_unwrap() follow:
The status code returned by the underlying mechanism.
Identifies the context on which the message arrived.
The message to be protected.
The buffer to receive the unwrapped message. Storage associated with this buffer must be freed by the application after use with a call to gss_release_buffer(3GSS).
If the value of conf_state is non-zero, then confidentiality and integrity protection were used. If the value is zero, only integrity service was used. Specify NULL if this parameter is not required.
Specifies the quality of protection provided. Specify NULL if this parameter is not required.
gss_unwrap() may return the following status codes:
The token failed consistency checks.
The MIC was incorrect.
The token was valid, and contained a correct MIC for the message, but it had already been processed.
The token was valid, and contained a correct MIC for the message, but it is too old to check for duplication.
The token was valid, and contained a correct MIC for the message, but has been verified out of sequence; a later token has already been received.
The token was valid, and contained a correct MIC for the message, but has been verified out of sequence; an earlier expected token has not yet been received.
The context has already expired.
The context_handle parameter did not identify a valid context.
The underlying mechanism detected an error for which no specific GSS status code is defined. The mechanism-specific status code reported by means of the minor_status parameter details the error condition.
See attributes(5) for descriptions of the following attributes: