-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi,
I've worked on this mostly out of stubbornness :), but maybe it is useful for someone here. README.md pasted below. https://github.com/rustybird/qubes-split-dm-crypt Rusty # _Split dm-crypt_ for Qubes R3.2-rc3 and later **Isolates device-mapper based secondary storage encryption (i.e. not the root filesystem) and LUKS header processing to DisposableVMs.** Instead of directly attaching an encrypted LUKS partition from a source VM such as sys-usb to a destination VM and decrypting it there, it works like this: 1. The encrypted partition is attached from the source VM to a (long-lived) offline _device DisposableVM_ configured not to parse its content in any way: The kernel partition scanners, udev probes, and UDisks handling are disabled. 2. From there, the LUKS header is sent to a (short-lived) offline _header DisposableVM_ prompting for the password, and the encryption key is sent back to the device DisposableVM, which validates that it received an AES-XTS key and creates the dm-crypt mapping. 3. Finally, the decrypted partition is attached from the device DisposableVM to the destination VM. **If the destination VM is compromised, it does not know the password or encryption key. It also cannot easily exfiltrate decrypted data to the disk in a form that would allow an attacker who seizes the disk contents later to read it.** (But see below for caveats.) ## Usage The `qvm-block-split` attach/detach commands accept a subset of the familiar `qvm-block` syntax, and some other commands are included: - - Fully overwrite a device with random data - - Overwrite just the LUKS header with random data - - Format a new LUKS device with modern crypto parameters: AES-XTS with 256+256 (instead of 128+128) bit keys, SHA512 (instead of SHA1) PBKDF2 key derivation with 5 (instead of 0.1) seconds iteration time When attaching, the destination VM argument can be omitted, in which case the decrypted disk will be attached to yet another offline DisposableVM. ``` qvm-block-split --attach|-a [--ro] [<dst-vm>] <src-vm>:<device> --detach|-d <src-vm>:<device> --overwrite-everything=random <src-vm>:<device> --overwrite-header=random <src-vm>:<device> --overwrite-header=format <src-vm>:<device> --overwrite-header=shell <src-vm>:<device> --modify-header=shell <src-vm>:<device> ``` ## Remaining attacks - - After detaching, the password and/or key will linger in more RAM locations than without _Split dm-crypt_. Until there is a way to wipe the DisposableVMs' memory, and `qvm-block-split` is modified not to pass the key through dom0's memory, **power off your computer when memory forensics is a concern.** - - If both the destination VM and the source VM/disk are compromised, they could establish a covert channel using e.g. read and write access patterns, slowly saving some amount of decrypted data to the disk. - - If the source VM/disk is compromised and successfully exploits the header DisposableVM using a malicious LUKS header, a known AES-XTS key could be sent to the device DisposableVM and used to present malicious device content to the destination VM to potentially exploit it as well. **Be suspicious if you do not see the expected filesystem data in the destination VM. Or simply use a DisposableVM as the destination VM.** - - **Don't forget to overwrite your disk with random data before creating a LUKS volume on it.** Otherwise, a compromised destination VM could trivially save decrypted data to the disk in its free space, by encoding each bit as an unmodified (still empty or in some other way nonrandom-looking) or modified (random-looking) 128 bit AES block. ## Installation 1. Copy `vm/` to the DisposableVM template, inspect the code, and `sudo make install` there; also install the `pv` (Pipe Viewer) package to be able to run the `--overwrite-everything=random` command. Shut down the template when finished. 2. Copy `dom0/bin/qvm-block-split` to dom0, e.g. into `~/bin/`, inspect the code extra carefully, and `chmod +x` the script. ## Safety warning The code's error handling is strict, and I haven't experienced any data loss during development. Nevertheless, this is an early release. Please **ensure you have a backup of all drives that are connected to your computer.** -----BEGIN PGP SIGNATURE----- iQJ8BAEBCgBmBQJX0anuXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQ4NEI1OUJDRkM2MkIxMjlGRTFCMDZEMDQ0 NjlENzhGNDdBQUYyQURGAAoJEEadePR6ryrfRkkQAI0BIUItYTgf+BNbgAyaykr1 3P+47IUZi0VaLgR0B6+7rRx/9KFkil1dUViz46PvkgD79S71Gl/ThIDSDayBCYmF Jpk0dwiscKXDZq6EfWVD3Bg0rYdXlmTeSEJn7jnNA35Vm4W9eS+tTdxNnsWhDpVb 97LD/muCgQHYqV8LcSLFcf4wxHMHC8zTh/ytC4ZCkgB+jNHJeJI6xMN8BnGemrMf 3sms1aj72pvg1rcRwlowWo9ib0Yl8Clav0s4308VuaOo2cPFknoDxIpnNloFMd15 RkXVPktoExSICFZKpuIdruEtcGswlxGlcqt3vGiUl1AkhCuJa8OARbfPlquupU+5 iDAWV3AcsAKR8xYL2eHSxIO1HsTU1PapsgsUSEEtviPe6x9wdWBijFk697Z+tabL aEwVYLPL58L2V3HHVeddc39k352Bmw7hvYAjuqWzoV3+9PS5Jz2fm64ziqC4S2XZ eGII4wPTH9+n3oYelXh98kx9YZUl0DBVcz9QgMSpgrzevd6h9GI3vVIeyosidj4z VPy5KKKBwq3R1B7jCg2JVjSRu+uk6nqt9p7Z/XU+jKsYZjhoC+NgjcNr2djD22Tr ruaza4DWhqUcoOjPdxu3bIvBy5fW6ZIIfe3RtRjI7bsK1Tc08SvIZ4Hlg+H1ifhF c0o1hc3WoO42zSZO7oaW =3QM0 -----END PGP SIGNATURE----- -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To post to this group, send email to qubes-users@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/fa3af217-9dcd-793e-e1bc-09be8d3d238c%40openmailbox.org. For more options, visit https://groups.google.com/d/optout.
