Recovering Files from Encrypted VM Disks

TL;DR

Yes, files can usually be retrieved from a VM instance state even if the disk was initially encrypted. The process depends on how it was encrypted and what access you have to keys or recovery mechanisms. This guide covers common scenarios.

Recovering Files: A Step-by-Step Guide

1. Identify Encryption Method
• Cloud Provider Managed Keys: (e.g., AWS KMS, Azure Key Vault, Google Cloud KMS). This is the most common setup. You’ll need access to the key management service.
• Customer-Supplied Keys: You hold the encryption keys directly. You must have these keys to decrypt. Losing them means permanent data loss.
• Disk Encryption Software: (e.g., LUKS, BitLocker). Requires specific tools and passwords/keyfiles.
2. Access the VM Instance State
• Stopped VM: If the VM is stopped but not deleted, you can typically attach the disk to another running VM for recovery.
• Deleted VM (Disk Still Exists): Most cloud providers allow retaining disks after deleting a VM. Attach it as above.
• Snapshot: Snapshots are point-in-time copies of the disk. You can create a new VM from a snapshot.
3. Attach the Disk to a Recovery VM

This is where you’ll actually access the data. The process varies by cloud provider:

• AWS: Use the EC2 console to detach the encrypted EBS volume from the original instance and attach it to a new, running EC2 instance with appropriate IAM permissions for KMS decryption.
• Azure: In the Azure portal, stop the VM (if running), detach the disk, and then attach it to a recovery VM. Ensure the recovery VM has access to the Key Vault containing the encryption key.
• Google Cloud: Stop the VM, detach the persistent disk, and attach it to a new instance. The new instance needs appropriate service account permissions for Google Cloud KMS decryption.
4. Decrypt the Disk (if necessary)
• Cloud Provider Managed Keys: The cloud provider usually handles decryption automatically when you attach the disk to a VM with correct permissions. You may need to mount the filesystem after attachment.
• Customer-Supplied Keys: You’ll likely need to use command-line tools or specific software to decrypt the disk before mounting it. For example, if using LUKS:

  sudo cryptsetup luksOpen /dev/sdX mydiskkeyfile

• Disk Encryption Software: Use the appropriate tool (e.g., BitLocker in Windows) to unlock and decrypt the disk, providing the password or keyfile.
5. Mount the Filesystem

Once decrypted (if needed), mount the filesystem to access the files.

• Identify the partition type (e.g., ext4, NTFS).
• Create a mount point:

  sudo mkdir /mnt/recovery

• Mount the filesystem:

  sudo mount /dev/sdX1 /mnt/recovery 

6. Copy Files

Copy the necessary files from the mounted filesystem to a safe location.

7. Unmount and Detach
• Unmount the filesystem:

  sudo umount /mnt/recovery

• Detach the disk from the recovery VM.

Important Considerations

• Permissions: Ensure your recovery VM has the correct permissions to access encryption keys and mount the filesystem.
• Key Management: Securely store and manage encryption keys. Losing them renders data inaccessible.
• Backup Strategy: Implement a robust backup strategy to prevent data loss in the first place.
• cyber security: Be aware of potential cyber security risks when handling sensitive data during recovery. Use secure transfer methods and protect access to your recovery VM.