add apparmor support

[giampaolo]

From ar...@maven.pl on February 21, 2014 12:24:36

Hi.
Please add apparmor (http://apparmor.wiki.kernel.org/) status reading support 
(at least):

# cat /proc/29752/attr/current 
/usr/sbin/httpd.prefork//HAT_owner_22753 (enforce)

which means that this process is using apparmor profile 
"/usr/sbin/httpd.prefork" and hat "HAT_owner_22753" in enforce mode.

Other possibilities of current are for example:
"unconfined" - so no policy loaded for the process

"/usr/sbin/httpd.prefork (enforce)" - only profile used, without apparmor 
activated (process can change its hats while running)

That info can be read from /proc or using libapparmor library: 
https://launchpad.net/apparmor/2.8/2.8.3/+download/apparmor-2.8.3.tar.gz

Original issue: http://code.google.com/p/psutil/issues/detail?id=483

[giampaolo]

From g.rodola on February 21, 2014 03:34:31

Mmm... I didn't know about this. 
My first impression is that this is too specific to belong into psutil.
Anyway, what API do you think this should have?
According to your example it seems this should return a (file, user) tuple or something.

[giampaolo]

From ar...@maven.pl on February 21, 2014 04:04:37

http://manpages.ubuntu.com/manpages/saucy/man2/aa_getcon.2.html and 
aa_gettaskcon is what interests us.

Such code:

#include <stdio.h>
#include <sys/apparmor.h>

int main() {
        char *b1, *b2;
        pid_t i;

        for (i=0; i<100000; i++) {
                if (aa_gettaskcon(i, &b1, &b2) != -1)
                        printf("[%s] [%s]\n", b1, b2);
        }
}

gets us:

[/usr/sbin/pure-ftpd] [enforce]
[unconfined] [(null)]
[unconfined] [(null)]
[unconfined] [(null)]
[/usr/sbin/httpd.prefork] [enforce]
[/usr/sbin/httpd.prefork//HANDLING_UNTRUSTED_INPUT] [enforce]

so API for this could be tuple (context, mode)
(terms from man page, it's not file, not profile according to man page, it's 
context and mode)

Note, on linux with apparmor disabled (# CONFIG_SECURITY_APPARMOR is not set) 
you can't access that file:

$ LC_ALL=C cat /proc/4393/attr/current 
cat: /proc/4393/attr/current: Invalid argument

apparmor is part of upstream linux kernel, so well... worth considering 
supporting it. Same for SELinux tags.