Using Shared Memory Labels

This example creates an identifier for a shared memory region at Confidential and gets the CMW label on the same shared memory region. The program is running at Top Secret.

 #include <sys/ipc.h>
 #include <sys/types.h>
 #include <tsol/label.h>
 #include <sys/shm.h>

 main()
 {
 	int          id, retval, error, pid;
 	bclabel_t    cmwlabel;
 	bslabel_t    senslabel;
 	char        *string = (char *)0;

 	retval = stobsl("CONFIDENTIAL", &senslabel, NEW_LABEL, &error);

 /* Create shared memory region at Confidential */
 /* Turn ipc_mac_write on in the effective set */
 	id = shmgetl(IPC_PRIVATE, 256, IPC_CREAT|0666, &senslabel);
 /* Turn off ipc_mac_write */

 /* Get CMW label of shared memory region */
 /* Turn ipc_mac_read on in the effective set */
 	retval = getshmcmwlabel(id, &cmwlabel);
 /* Turn off ipc_mac_read */

 /* Print CMW label */
 	bcltos(&cmwlabel, &string, 0, LONG_WORDS);
 	printf("CMW label = %s\n", string);
 }

The printf(1) statement prints the following:

CMW label = UNCLASSIFIED[C]