AA_CHANGE_PROFILE(2)						     AppArmor						      AA_CHANGE_PROFILE(2)

NAME

       aa_change_profile, aa_change_onexec - change a tasks profile

SYNOPSIS

       #include <sys/apparmor.h>

       int aa_change_profile(const char *profile);

       int aa_change_onexec(const char *profile);

       Link with -lapparmor when compiling.

DESCRIPTION

       An AppArmor profile applies to an executable program; if a portion of the program needs different access permissions than other portions,
       the program can "change profile" to a different profile. To change into a new profile, it can use the aa_change_profile() function to do
       so. It passes in a pointer to the profile to transition to. Transitioning to another profile via aa_change_profile() is permanent and the
       process is not permitted to transition back to the original profile. Confined programs wanting to use aa_change_profile() need to have
       rules permitting changing to the named profile. See apparmor.d(8) for details.

       If a program wants to return out of the current profile to the original profile, it should use aa_change_hat(2) instead.

       Open file descriptors are not remediated after a call to aa_change_profile() so the calling program must close(2) open file descriptors to
       ensure they are not available after calling aa_change_profile(). As aa_change_profile() is typically used just before execve(2), you may
       want to use open(2) or fcntl(2) with close-on-exec.

       The aa_change_onexec() function is like the aa_change_profile() function except it specifies that the profile transition should take place
       on the next exec instead of immediately.  The delayed profile change takes precedence over any exec transition rules within the confining
       profile.  Delaying the profile boundary has a couple of advantages, it removes the need for stub transition profiles and the exec boundary
       is a natural security layer where potentially sensitive memory is unmapped.

RETURN VALUE

       On success zero is returned. On error, -1 is returned, and errno(3) is set appropriately.

ERRORS

       EINVAL
	   The apparmor kernel module is not loaded or the communication via the /proc/*/attr/current file did not conform to protocol.

       ENOMEM
	   Insufficient kernel memory was available.

       EPERM
	   The calling application is not confined by apparmor.

       EACCES
	   The task does not have sufficient permissions to change its domain.

EXAMPLE

       The following example shows a simple, if contrived, use of aa_change_profile(); a typical use of aa_change_profile() will
       aa_change_profile() just before an execve(2) so that the new child process is permanently confined.

	#include <stdlib.h>
	#include <string.h>
	#include <sys/apparmor.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <fcntl.h>
	#include <stdio.h>
	#include <unistd.h>

	int main(int argc, char * argv[])
	{
		int fd;
		char buf[10];
		char *execve_args[4];

		printf("Before aa_change_profile():
");
		if ((fd=open("/etc/passwd", O_RDONLY)) < 0) {
		       perror("Failure opening /etc/passwd");
		       return 1;
		}

		/* Confirm for ourselves that we can really read /etc/passwd */
		memset(&buf, 0, 10);
		if (read(fd, &buf, 10) == -1) {
			perror("Failure reading /etc/passwd");
			return 1;
		}
		buf[9] = '';
		printf("/etc/passwd: %s
", buf);
		close(fd);

		printf("After aa_change_profile():
");

		/* change profile to the "i_cant_be_trusted_anymore" profile, which
		 * should not have read access to /etc/passwd. */
		if (aa_change_profile("i_cant_be_trusted_anymore") < 0) {
		    perror("Failure changing profile -- aborting");
		    _exit(1);
		}

		/* confirm that we cannot read /etc/passwd */
		execve_args[0] = "/usr/bin/head";
		execve_args[1] = "-1";
		execve_args[2] = "/etc/passwd";
		execve_args[3] = NULL;
		execve("/usr/bin/head", execve_args, NULL);
		perror("execve");
		_exit(1);
	}

       This code example requires a profile similar to the following to be loaded with apparmor_parser(8):

	profile i_cant_be_trusted_anymore {
	    /etc/ld.so.cache	  mr,
	    /lib/ld-*.so*	  mrix,
	    /lib/libc*.so*	  mr,

	    /usr/bin/head ix,
	}

       The output when run:

	$ /tmp/change_p
	Before aa_change_profile():
	/etc/passwd: root:x:0:
	After aa_change_profile():
	/usr/bin/head: cannot open `/etc/passwd' for reading: Permission denied
	$

       If /tmp/change_p is to be confined as well, then the following profile can be used (in addition to the one for 'i_cant_be_trusted_anymore',
       above):

	# Confine change_p to be able to read /etc/passwd and aa_change_profile()
	# to the 'i_cant_be_trusted_anymore' profile.
	/tmp/change_p {
	    /etc/ld.so.cache	      mr,
	    /lib/ld-*.so*	      mrix,
	    /lib/libc*.so*	      mr,

	    /etc/passwd 	      r,

	    # Needed for aa_change_profile()
	    /usr/lib/libapparmor*.so* mr,
	    /proc/[0-9]*/attr/current w,
	    change_profile -> i_cant_be_trusted_anymore,
	}

BUGS

       None known. If you find any, please report them at <http://https://bugs.launchpad.net/apparmor/+filebug>. Note that using
       aa_change_profile(2) without execve(2) provides no memory barriers between different areas of a program; if address space separation is
       required, then separate processes should be used.

SEE ALSO

       apparmor(7), apparmor.d(5), apparmor_parser(8), aa_change_hat(2) and <http://wiki.apparmor.net>.

AppArmor 2.7.103						    2012-06-28						      AA_CHANGE_PROFILE(2)