How to rescue data from windows

Posted on March 13, 2021 by Adrian Wyssmann ‐ 3 min read

My son has a Surface Go Tablet which suddenly stopped booting. Even after trying to uninstall patches etc. I could not bring it back, so I decided to help him to get the data from the tablet, so he can use it.

How to Rescue Data From Windows
How to Rescue Data From Windows

What do we need?

So in order to rescue data you create a bootable usb-disk with a linux os and boot your Windows computer/tablet from it. However one has to be aware of two things:

  1. Bitlocker: Modern Windows devices are increasingly protected with BitLocker Device Encryption out of the box
  2. UEFI: Secure Boot prevents the OS from booting unless they’re signed by a key loaded into UEFI - so per-default means only software signed by Microsoft

For the 1. issue, your Linux distribution of choice shall contain a tool to decrypt Bitlocker disks - for example dislocker. As distribution I recommend System-Rescue as it contains a nice set of default tools incl. dislocker. To decrypt the Bitlocker disks you also need the recovery key provided by Microsoft which looks something like XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX.

The 2. issue is a bit more challenging - or not, you have some options here

  • Choose a Linux Distribution That Supports Secure Boot
  • Disable Secure Boot
  • Add a Signing Key to the UEFI Firmware

Disabling secure boot will remove the security benefits, but as I try to recover data, it really does not matter and guess is the easiest way to be able to boot the usb-disk.

Steps to recover the data

  1. First you have to download the iso and then create a bootable usb-disk
  2. On the Computer/Tablet enter the BIOS
    • disable Secure Boot
    • change the boot order so that the usb drive is before the internal disk
  3. Put the bootable usb-stick in the USB port and boot up your Linux distro

From there check which is the Bitlocker disk - I use Gparted, but you may also use fdisk or whatever you have at hand:

Check the disk partitions
Check the disk partitions to see which one is the Bitlocker partition

Once you have identified the disk you can go on and use [dislocker] to decrypt the disk. Ensure you have a mount point:

[root@sysrescue ~]# mkdir /mnt/disk
[root@sysrescue ~]# dislocker /dev/nvme0n1p3 -vvv -pXXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX-XXXXXX -- /mnt/disk/
Sat Mar 13 10:14:41 2021 [INFO] dislocker by Romain Coltel, v0.7.2 (compiled for Linux/x86_64)
Sat Mar 13 10:14:41 2021 [INFO] Compiled version: master:820c0f5
Sat Mar 13 10:14:41 2021 [INFO] Volume GUID (INFORMATION OFFSET) supported
Sat Mar 13 10:14:41 2021 [INFO] BitLocker metadata found and parsed.
Sat Mar 13 10:14:41 2021 [INFO] Stretching the recovery password, it could take some time...
Sat Mar 13 10:14:43 2021 [INFO] Stretching of the recovery password is now ok!
Sat Mar 13 10:14:43 2021 [INFO] Used recovery password decryption method
Sat Mar 13 10:14:43 2021 [INFO] Found volume's size: 0x1d77300000 (126553686016) bytes
Sat Mar 13 10:14:43 2021 [INFO] Running FUSE with these arguments: 
Sat Mar 13 10:14:43 2021 [INFO]   `--> 'dislocker'
Sat Mar 13 10:14:43 2021 [INFO]   `--> '/mnt/disk/'

So let’s see what we have under /mnt/disk

[root@sysrescue ~]# ls /mnt/disk
[root@sysrescue ~]# dislocker-file

Not what I expected - I thought the /mnt/disk/ contains the decrypted content mounted but instead it contains a dislocker-file. According to dislocker, it’s a flat file which can be mounted as NTFS partition. So, let’s mount it:

[root@sysrescue ~]# mkdir /mnt/bitlocker
[root@sysrescue ~]# mount /mnt/disk/dislocker-file /mnt/bitlocker/`

Finally I have access to the data, so from there we can copy the data.

Decrypted Bitlocker disk
If you finally decrypted your Bitlocker disk you have access to the data on the disk