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:

minor_status

The status code returned by the underlying mechanism.

context_handle

Identifies the context on which the message arrived.

input_message_buffer

The message to be protected.

output_message_buffer

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).

conf_state

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.

qop_state

Specifies the quality of protection provided. Specify NULL if this parameter is not required.

gss_unwrap() may return the following status codes:

GSS_S_COMPLETE

Successful completion.

GSS_S_DEFECTIVE_TOKEN

The token failed consistency checks.

GSS_S_BAD_SIG

The MIC was incorrect.

GSS_S_DUPLICATE_TOKEN

The token was valid, and contained a correct MIC for the message, but it had already been processed.

GSS_S_OLD_TOKEN

The token was valid, and contained a correct MIC for the message, but it is too old to check for duplication.

GSS_S_UNSEQ_TOKEN

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.

GSS_S_GAP_TOKEN

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.

GSS_S_CONTEXT_EXPIRED

The context has already expired.

GSS_S_NO_CONTEXT

The context_handle parameter did not identify a valid context.

GSS_S_FAILURE

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:

gss_release_buffer(3GSS), gss_wrap(3GSS), attributes(5)

GSS-API Programming Guide