Using Path Names with Adornments

UNIX system calls that accept a path name such as open(2) and creat(2) go to the SLD at the same sensitivity label as the process unless the fully adorned path name is passed instead of a regular path name. The fully adorned path name includes the MLD adornment and the SLD directory name as shown in the code example. Note that a process cannot create files or directories in either an MLD or SLD with the mkdir(1) system call.

The mandatory access and discretionary access controls described in "Security Policy" apply.

Open a File

In this example, the process is running at Confidential with a clearance of Top Secret. The Confidential process needs the file_mac_search privilege in its effective set to access the SLD at Top Secret. Because the file is opened for writing and a write-up is allowed by the security policy, no other privileges are needed assuming the operation passes all discretionary access checks.

#include <tsol/label.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

main()
{
	int filedes;

/* Open a file in the SLD at which the process is running */
	filedes = open("/export/home/zelda/afile", O_WRONLY);
	printf("File descriptor for regular path = %d\n", filedes);

/* Open a file in the Top Secret SLD */
/* Turn file_mac_search on in the effective set */
	filedes = open("/export/home/.MLD.zelda/.SLD.3/afile", O_WRONLY);
/* Turn file_mac_search off */

	printf("File descriptor for adorned path = %d\n", filedes);
}

The printf statements print the following.

File descriptor for regular path = 3
File descriptor for adorned path = 4

Create a file

In this example, the process is running at Confidential with a clearance of Top Secret. The Confidential process needs the file_mac_search privilege in its effective set to access the SLD at Top Secret. If afile does not already exist in the Top Secret SLD, the process needs the file_mac_write privilege because the process sensitivity label does not equal the SLD sensitivity label. If afile already exists, the file_mac_write privilege is not needed.

#include <tsol/label.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

main()
{	
	int filedes;

/* Create a file in the SLD at which the process is running */
	filedes = creat("/export/home/zelda/afile", 660);

	printf("File descriptor for regular path = %d\n", filedes);

/* Create a file in the Top Secret SLD */
/* Turn file_mac_search on in the effective set */
	filedes = creat("/export/home/.MLD.zelda/.SLD.3/afile", 660);
/* Turn file_mac_search off */

	printf("File descriptor for adorned path = %d\n", filedes);
}

The printf statements print the following.

File descriptor for regular path = 3
File descriptor for adorned path = 4