How to Protect Your Server Against the Shellshock Bash Vulnerability

if you have some old / EOL release, this code may help you.

it requires you to have a compiler, patch & make, as such you may need to install these packages

for Ubuntu you can do

for CentOS/variants

(you may uninstall them afterwards if you no longer need)

after that, you can install bash from scratch, follow these commands (taken from the internet somewhere)

can first “cd /tmp” or start in any directory of your choice; must be executed as root [updated 2014-09-27 0900 EST [GMT-0500] now 26 patches instead of 25] [updated 2014-09-28 0900 EST [GMT-0500] now 27] [updated 2014-10-01 1400 EST [GMT-0500] now 28] [updated 2014-10-02 2300 EST [GMT-0500] now 29]

mkdir src
cd src
wget http://ftp.gnu.org/gnu/bash/bash-4.3.tar.gz
#download all patches
for i in $(seq -f "%03g" 0 30); do wget     http://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-$i; done
tar zxvf bash-4.3.tar.gz 
cd bash-4.3
#apply all patches
for i in $(seq -f "%03g" 0 30);do patch -p0 < ../bash43-$i; done
#build and install
./configure && make && make install
cd .. 
cd ..
rm -r src

after this you should have the newest bash installed on your system

run the test again to check yourself

env VAR='() { :;}; echo Bash is vulnerable!' bash -c "echo Bash Test"

you should be good to go now!

Here’s Puppet code to patch it on CentOS:

exec { 'patch_shellshock_security_hole':
  command => "/usr/bin/yes | /usr/bin/yum update bash; touch /root/shellshock_bug_has_been_patched",
  creates => '/root/shellshock_bug_has_been_patched',
}

I have just tested this code and it worked fine on CentOS 6.4.

Ross

Not so fast! Give it a try, still vulnerable!

env -i X=' () { }; echo hello' bash -c 'date'

https://shellshocker.net/

Thanks Mitchel

I will have to tell the admin to be careful and follow what the monitoring tool Anturis says and alerts. By the way, are ny monitoring tool at help here?

All people running Linux systems whether on local machines or servers were put in panic when a security flaw was discoverd in Bash, the Bash Remote Exploit was nick named as Shellshock.

The vulnerability was exposed in HTTP/CHI scripts and in OpenSSH. It effected nearly all versions of Linux, thankfully there was an update available to secure yourself.

Cloudways was among the first to fix the entire infrastructure and provide extra security to its clients - Here: Bash Remote Exploits

FYI - I’ve a droplet from a DO supplied application “WordPress on Ubuntu12.10” . The Control Panel Kernel screen says “Orginal Kernel (Ubuntu 12.10 x64 vmlinuz-3.5.0-17-generic(25))” uname –ri lists - 3.5.0-17-generic x86_64 (only one option)

I tried the suggestion in this article, and they didn’t work. I tried a whole bunch of other suggestions that other people have put out there using mirrors supplied by DO - and they didn’t work I tried a Kernel Upgrade - and it turns out that for my DO supplied Ubuntu12.10 distribution it is some strange version (created as a DO application) and it isn’t supported in the Kernel Upgrade - despite there being a lot of options visually available in the Control Panel - Kernel Upgrade. I’ve opened a ticket on the upgrade question, and I’m not getting any reasonable suggestions - it seems DO support is talking Apple Pie - “you need to upgrade” but no reasonable working ways to do it, “Changing the kernel in the control panel does not upgrade the kernel on the droplet.” - with no workable method for what can work.

I’m getting DO advice that aren’t working solutions.

I’ve found such tool for vulneratility test: http://www.host-tracker.com/Blog/Shellshock

after i installed the bash update, my php shell_exec command to run pdftk does not work anymre - any ideas what to do?

thanks

Thanks for the tutorial, I’m not a regular sysadmin and only fine tune DO droplets when the need arises and then its usually a steep learning curve. I did a backup - the node is 198.199.94.20 Way back I launched a defined DO package for wordpress - my console settings Kernel says “Original Kernel (Ubuntu 12.10 x64 Server vmlinuz-3.5.0.17-generic(25))" I’ve tried to swap the kernel out for one of the options “Ubuntu 13.10 x64 vmlinuz-3.11.0-26-generic” to then do an upgrade but after rebooting it is still at 12.10? I’m wondering why this failed?

I’ve tried using the “do-release-upgrade” - but it comes back with

Your Ubuntu release is not supported anymore. Err Upgrade tool signature 404 Not Found [IP: 91.189.91.14 80] Err Upgrade tool 404 Not Found [IP: 91.189.91.14 80] Fetched 0 B in 0s (0 B/s) WARNING:root:file ‘raring.tar.gz.gpg’ missing Failed to fetch Fetching the upgrade failed. There may be a network problem.

I’ve tried https://www.digitalocean.com/community/questions/update-on-ubuntu-12-10-server-failing-not-found but it aborted and restored back to 12.10

I hear “@manicas” advice that its not recommended to let a server be at 12.10 - but I do have a DO supplied configuration that is at 12.10, and I wonder is there a tutorial for dummies to say how to upgrade it. I have spent a couple of hours trying to stitch together an upgrade. Many thanks.