Decrypting Full Disk Encryption with Dissect

Author: Guus Beckers Back in 2022 Fox-IT decided to open source its proprietary incident response tooling known as Dissect. Since then it has been adopted by many different companies in their regular workflow. For those of you who are not yet familiar with Dissect, it is an incident response framework built with incident response engagements of any … Continue reading Decrypting Full Disk Encryption with Dissect →

Decrypting Full Disk Encryption with Dissect

Fox-SRT

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December 11, 2024December 5, 2024

7 Minutes

Author: Guus Beckers

Back in 2022 Fox-IT decided to open source its proprietary incident response tooling known as Dissect. Since then it has been adopted by many different companies in their regular workflow. For those of you who are not yet familiar with Dissect, it is an incident response framework built with incident response engagements of any scale in mind. It allows you to extract artifacts from a variety of data formats and export them to a format of your choosing. Ever since Dissect has been open sourced a large number of individuals and institutions have contributed to the Dissect framework, culminating in the first Dissect partner day earlier in 2024.

One of the most popular requests has been the capability to use Dissect in combination with common disk encryption methods like Microsoft’s BitLocker or its Linux equivalent LUKS. Internally at Fox-IT we were able to already use these capabilities. With the release of Dissect version 3.17 these capabilities are now also available to the community at large.

Of course, a blog post is not complete without a demo. In this scenario a data acquisition has been performed against a disk protected with BitLocker. We are interested in a specific file located on the user’s desktop. During this scenario, a virtual machine was created with VMware Fusion which uses the .vmwarevm file format. Dissect can parse this format thanks to its associated loader.

First, we use Dissect to examine the disk properties:

$ target-info "Windows 11 x64.vmwarevm" -v
2024-11-27T11:57:18.474060Z [error    ] Failed to open an encrypted volume <Volume name='Basic data partition' size=67921509888 fs=None> with volume manager bitlocker: Failed to unlock BDE volume [dissect.target.volume]
2024-11-27T11:57:18.634092Z [warning  ] <Target Windows 11 x64.vmwarevm>: Can't identify filesystem: <Volume name='Microsoft reserved partition' size=16776704 fs=None> [dissect.target.target]
2024-11-27T11:57:19.416120Z [warning  ] <Target Windows 11 x64.vmwarevm>: Failed to find OS plugin, falling back to default [dissect.target.target]
<Target Windows 11 x64.vmwarevm>

Disks
- <Disk type="VmdkContainer" size="68719476736">

Volumes
- <Volume name="Basic data partition" size="104857088" fs="FatFilesystem">
- <Volume name="Microsoft reserved partition" size="16776704" fs="NoneType">
- <Volume name="Basic data partition" size="67921509888" fs="NoneType">
- <Volume name="part_fd7c00000" size="673185280" fs="NtfsFilesystem">

Hostname       : None
Domain         : None
Ips            :
Os family      : default
Os version     : None
Architecture   : None
Language       :
Timezone       : None
Install date   : 1970-01-01T00:00:00.000000+00:00
Last activity  : None

It seems the disk is encrypted, now we can use the latest version of BitLocker to decrypt the information.  Dissect supports three different types of decryption capabilities. An analyst can either use the user’s passphrase, the recovery key or can use a BitLocker file. Please check the updated documentation on the Dissect Docs page for more information.  For now we have created a keychain CSV file with the following information:

$ cat keychain.csv
bitlocker,recovery_key,,395791-328042-677721-279895-554466-214599-232023-709148

We can use Dissect’s commands like target-info to check if the keychain works:

$ target-info "Windows 11 x64.vmwarevm" -K keychain.csv
2024-11-27T10:18:01.698079Z [warning  ] <Target Windows 11 x64.vmwarevm>: Can't identify filesystem: <Volume name='Microsoft reserved partition' size=16776704 fs=None> [dissect.target.target]
2024-11-27T10:18:02.731474Z [warning  ] <Target Windows 11 x64.vmwarevm>: Empty hive: sysvol/windows/SECURITY [dissect.target.target]
2024-11-27T10:18:02.737980Z [warning  ] <Target Windows 11 x64.vmwarevm>: Empty hive: sysvol/windows/SYSTEM [dissect.target.target]
<Target Windows 11 x64.vmwarevm>

Disks
- <Disk type="VmdkContainer" size="68719476736">

Volumes
- <Volume name="Basic data partition" size="104857088" fs="FatFilesystem">
- <Volume name="Microsoft reserved partition" size="16776704" fs="NoneType">
- <Volume name="Basic data partition" size="67921509888" fs="NoneType">
- <Volume name="part_fd7c00000" size="673185280" fs="NtfsFilesystem">
- <Volume name="Basic data partition" size="67921509888" fs="NtfsFilesystem">

Hostname       : SECRETDATAVM
Domain         : None
Ips            : 192.168.212.129
Os family      : windows
Os version     : Windows 11 Pro (NT 10.0) 26100.2314
Architecture   : amd64-win64
Language       : en_GB, en_NL, en_US
Timezone       : Europe/Berlin
Install date   : 2024-11-27T17:34:07.000000+00:00
Last activity  : 2024-11-27T17:33:31.670376+00:00

Alternatively, we can pass the recovery key value directly like this:

$ target-info "Windows 11 x64.vmwarevm" -Kv 395791-328042-677721-279895-554466-214599-232023-709148 -v

Now we can browse through the decrypted filesystem and view the file on the user’s desktop:

$ target-shell "Windows 11 x64.vmwarevm" -Kv 395791-328042-677721-279895-554466-214599-232023-709148 -q

SECRETDATAVM:/$ cat c:/Users/Staff/Desktop/SuperSecretFile.txt
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

As you can imagine this also works with Linux in the exact same manner.  This time we use a LUKS passphrase in conjunction with Dissect:

$ target-info "Ubuntu 64-bit 24.04.1.vmwarevm" -Kv glad-design-paper-airplane
2024-11-27T11:48:07.224355Z [warning  ] Failed to decode raw key as hex, ignoring: glad-design-paper-airplane [dissect.target.helpers.keychain]
2024-11-27T11:48:08.910029Z [warning  ] <Target Ubuntu 64-bit 24.04.1.vmwarevm>: Can't identify filesystem: <Volume name='part_00100000' size=1048064 fs=None> [dissect.target.target]
2024-11-27T11:48:09.826056Z [warning  ] <Target Ubuntu 64-bit 24.04.1.vmwarevm>: Unsupported mount device: /dev/disk/by-id/dm-uuid-LVM-YZiSLhoYFljS62k2vIjl3IcTwSkd0QguADKOf0a8t9am1jNdm9J1zerrDU7SWWFd / [dissect.target.target]
<Target Ubuntu 64-bit 24.04.1.vmwarevm>
2024-11-27T11:48:13.916382Z [warning  ] No timestamp found in one of the lines in /var/log/syslog! [dissect.target.helpers.utils]
2024-11-27T11:48:13.925913Z [warning  ] Timestamp '27 2024 12:40:57' does not match format '%b %d %H:%M:%S', skipping line. [dissect.target.helpers.utils]
2024-11-27T11:48:13.936096Z [warning  ] Timestamp 'Nov 2024 11:40:35' does not match format '%b %d %H:%M:%S', skipping line. [dissect.target.helpers.utils]
2024-11-27T11:48:13.936416Z [warning  ] Timestamp 'Nov 2024 11:40:35' does not match format '%b %d %H:%M:%S', skipping line. [dissect.target.helpers.utils]
2024-11-27T11:48:13.944841Z [warning  ] Timestamp 'Nov 2024 11:40:15' does not match format '%b %d %H:%M:%S', skipping line. [dissect.target.helpers.utils]
2024-11-27T11:48:13.950083Z [warning  ] Timestamp 'Nov 2024 11:40:11' does not match format '%b %d %H:%M:%S', skipping line. [dissect.target.helpers.utils]
2024-11-27T11:48:13.985809Z [warning  ] Timestamp 'Nov 2024 11:40:04' does not match format '%b %d %H:%M:%S', skipping line. [dissect.target.helpers.utils]
2024-11-27T11:48:14.037897Z [warning  ] <Target Ubuntu 64-bit 24.04.1.vmwarevm>: Could not match cloud-init log line in file: /var/log/cloud-init.log [dissect.target.target]

[...]

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*[Original source](https://blog.fox-it.com/2024/12/11/decrypting-full-disk-encryption-with-dissect/)*