Skip to main content

ShellShock Basics - Updated Oct 1st

By
Update 2 - October 1st: As expected still lots going on;

As the mainstream media attempts to make sense of all the hype surrounding the latest security vulnerability, IT support staff are left to try to make sense of it all and determine what if anything needs to be done.

Background: Bash (aka Bourne-again Shell) is used as an interactive shell on most Unix-like operating systems.  It comes by default on many popular distributions such as Ubuntu, OSX, and other Linux platforms.

The bug:  One feature of the shell is to allow a user to set environment variables, unfortunately the bash shell does a poor job of interpreting these values and if the right sequence of characters is used, extra commands can be executed.
Exploitation:  By simply injecting extra code that will get passed to bash it will get executed in the context of the process reading it.  This happens as soon as the environment variables are read by bash.
Am I vulnerable:  Any software that you use that reads environment variables from untrusted, unauthenticated inputs should be examined.  Example if a CGI script parses HTTP headers.  It is prudent to review all of your public interfaces for potential exposure.  Use the Cert list to see if your vendors are listed and get a link to the specific advisory.
  • CERT List of Vendors Affected - http://www.kb.cert.org/vuls/byvendor?searchview&Query=FIELD+Reference=252743&SearchOrder=4
  • Nmap tests
  • Masscan tests
Is it patched yet:  There are numerous vendors affected.  Many of the major vendors were informed about the bug prior to release to prepare patches, some have patches that work, others do not.  Basic patches have been released.
What else should I do:  Monitor requests (in the past if you have the capability) this will tell you if people are attempting to exploit you.  Look for signatures that have been released by Sourcefire, BroIDS and other IDS vendors.  If you can look at past traffic captures then you might be able to determine if you had been a target prior to the bug's disclosure.
Monitor the situation closely, it is likely that there will be details of the specific applications and software affected as well as other mitigations that can be taken until robust patches are released.


Labels:

Comments

Post a Comment

Popular posts from this blog

Anti-virus Statistics - Motivations

By
In a study completed and published by Avira ( http://www.avira.com/en/company_news/recognition_performance_virus_protection.html ) The results of the survey showed that for 34 percent (3,207 respondents) a long-established, trustworthy brand was key. Almost as many users, 33 percent (3,077 respondents), based their decision on the virus detection rates achieved in independent tests. Detection rates - lets call this effectiveness of the control - as this is the key metric used to measure effectiveness. This is a skewed metric as for the large majority of evaluations (ICSALabs, VB100, etc) use the "in-the-wild" or ITW list of viruses to perform the evaluations. There is no evaluation of these product's ability to respond or even detect newly released virus and malware. In all honesty really what we are dealing with here is preventative vulnerability management not virus detection and correction, and in my opinion there are four types of preventative protections required f
Post a Comment
Read more

Local Classified Penny Auction Scam

By
While there are a lot of new posts regarding the new ways to exploit people using novel techniques and 0day exploits, there continues to be a rash of tried and true methods of coercion.  I want to just walk through a simple example and reflect on how effective these methods continue to be. Many people turn toward online classified sites to buy and sell items online.  This example starts with kijiji.ca which even I've used on occasion to find used electronics and other items.  Doing a search on the site for a " Samsung Galaxy Note 2 " returns a posting from today with someone selling one for an unreasonably priced unit. $125 for a $500 phone?, but what if it's for real?  No harm in just asking some simple questions.  Email sent with some obvious questions regarding the condition and location. About an hour passes before I get a response from what appears to be a legit seller. Notice no answer to the questions I asked, but a friendly pointer at where th
14 comments
Read more

OpenSolaris, ZFS, iSCSI and OSX - Creative Storage - Part II

By
In part I of this post, I looked at the simple steps required to setup a relatively simple storage solution using OpenSolaris, ZFS, iSCSI and OSX. This was about a month ago, and I've made some significant changes on how this is used for me. At the end of the last post I left off on the part dealing with configuration of the iSCSI initiator side of the solution. I stopped here because there were some issues related to the installation and use of the software. The iSCSI initiator that I was using was Studio Network Solutions GlobalSAN initiator (version 3.3.0.43) which is used to allow for connections to their products. This software will also allow for connections to ANY iSCSI target! After the configuration of the iSCSI target on the ZFS pool, and installation of the client it was trivial to get the connection established with the storage pool, and it showed up in OSX as a raw disk which had not been formatted. I proceeded to format the disk as HFS+ and it then mounted as a lo
1 comment
Read more