Thursday, 18 July 2013

Research on Azure WebSite security: Process Execution (cmd.exe, git.exe, node.exe, xyz.exe) and Folder Browsing (outside azure root)

Following the presentation I did a couple weeks ago at the UK Azure user-group event (http://ukwaug.net/events/security-compliance/), here are my rough notes on my research (for a couple hours/days before the event)

Using  DotNet_ANSA (see end of post for more info about this tool) I was able to show a number of security issues that exist with Azure Websites

BUT (Important disclaimer):
  • I was not able to see data from other Azure websites hosted on the same server (since I was limited by the IIS user account used)
  • This happens because of running .NET code under Full Trust (which is the default in most ASP.NET apps, since partial trust is dead now)
  • Although this is nothing new, I was surprised by the number of ASP.NET Azure specialists that were not aware that it was possible to (for example) browse files/folders outside the allocated folder and start new processes on the azure server
  • These are ‘Security Issues’ and ‘Areas of concern’ for Azure (and other) deployed websites.
  • These are not ‘Security Vulnerabilities’ since they happen by ‘design’
  • The key is to make sure that all parties understand that this is possible (namely remove process execution on cloud/hosted services)
  • I didn’t upload any exploits or metasploit-like tools (since that would be pushing my Azure testing a bit too far), but as far as I can see, they should work 
  • I didn't spent a lot of time on this, and there are a number of other research areas that should be pursued


So what can be done in an Azure website using DotNet_ANSA and a couple custom O2 Platform REPL scripts?

Here are a couple examples:

View folder: D:\

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View folder: D:\windows\panther

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View folder: D:\windows\System32

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View file: …\Framework\v4.0.30319\config\web.config

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View file: Sysprep's unattend.xml  (note that the admin pwd was removed)

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Execute via WinExe API: route print

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Execute via cmd.exe: dir c:\

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Execute via cmd.exe: ipconfig (access denied)

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Execute via cmd.exe: ping (help contents)

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Execute via cmd.exe: ping (execution fails)

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Execute via .NET Process.Start: Notepad (process will start and asp.net thread will hang while notepad is still open (on the server))

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Execute via c# REPL: get process list (where we see the notepad process started above)

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Execute via uploaded exe : hostname.exe

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Execute via .NET Process.Start: Node.exe --help (Node JS)

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Execute via .NET Process.Startgit.exe --help

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Executed via C# REPL Script (visualised locally): List Environment Variables:

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Executed via C# REPL Script (visualised locally): List special folders:

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Executed via C# REPL Script (visualised locally):  Environment values (via Reflection)

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Executed via C# REPL Script: Environment.CommandLine

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Executed via C# REPL Script: folders (value returned as JSON object)

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Note: WMI is disabled which dramatically reduces the attack surface:

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OWASP ANSA:

To create the screenshots shown above I used the OWASP ANSA webapp which I just pushed to the OWASP GitHub repo https://github.com/OWASP/DotNet_ANSA.

This is a very rough web app which is based on the original ASP and ASP.NET security research that I did years ago (2008 to be exact) with large parts of the code still written in VB and for .Net 1.1:
Also included is a variation of the O2’s web-based C# REPL:
In fact you can see by the evolution of the screenshots how I was fixing the code and styles during my research :)
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