Provided by: libapparmor1_2.7.0~beta1+bzr1774-1ubuntu2_i386 bug

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.

       ECHILD
           The application's profile has no hats defined for it.

       EACCES
           The specified profile does not exist in this profile or the process
           tried to change another process's 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():\n");
                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] = '\0';
                printf("/etc/passwd: %s\n", buf);
                close(fd);

                printf("After aa_change_profile():\n");

                /* 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>.