Thursday, March 13, 2014

Daily Blog #263: Decrypting images with a little help from Arsenal Image Mounter

Hello Reader,
       Looks like I need some more time before I finish up my work with Hal's mlocator and mlocate-time scripts, so instead of finishing that series I thought I would post about something cool that I found with a client. Hello client who is not being named directly! It was good seeing you this week.

So, let's say you have an image of a  full disk encrypted drive and you want to get a tool that doesn't support transparently decrypting the disk (something tools like FTK and Encase can do) to work with the image. Now what we are about to talk about here assumes that you have the password/recovery key/private key whatever it is you need to decrypt the disk, so don't think this is some magic backdoor mechanism for encrypted disks.

Step 1. The first thing you'll need to do is get your disk image into raw/dd format. If you have it in another format you can convert most formats to raw using FTK Imager. If this sounds confusing I'll post another blog showing how to do this. If you made a raw image then your ready to go!

Step 2. You need to decide if you want to keep a copy of the encrypted disk image, and thus have two images one encrypted and decrypted. I would recommend this for criminal cases as they have a higher burden of proof but not for civil cases.

Step 3. Take the raw image and use Arsenal Image Mounter to mount it as a physical volume. The trick here again lies in that AIM is going to get Windows to recognize the disk as a physical volume via iSCSI.

Step 4. You will choose the option to modify the original image rather than make it read only or have an overlay file.

Step 5. Your encrypted physical disk image is now present on your computer and will interact as any other physical disk. You should now load up whatever encryption software was used to encrypt the disk in the first place and enter the passcode/recovery key to unlock the drive. For Bitlocker drives (what we tested this week) the dialog will just pop up and say Hey Buddy! This is a bitlocker drive, got the recovery key?

Step 6. Remove the drive encryption, in Bitlocker you just have to go to the control panel->bitlocker and turn off bitlocker on the mounted image.

Step 7. Wait for the decryption to finish and unmount the image.

There you go, you're done! The image you mounted has now been modified and contains a  full decrypted disk image and ready to work with any tool you have that supports raw disk images.

This method isn't perfect but it does solve some issues and if you keep a copy of the encrypted image you'll always be able to go back and either repeat the procedure or load it a tool that supports the encryption suite directly.

I'll make another post like this specifically for  Bitlocker next week when I have time to make some test data.