[Image description:
Screenshot of terminal output:
~ ❯ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sda 8:0 1 62.5M 0 disk
└─topLuks 254:2 0 60.5M 0 crypt
└─bottomLuks 254:3 0 44.5M 0 crypt
/end image description]
I had no idea!
If anyone else is curious, it’s pretty much what you would expect:
cryptsetup -y -v luksFormat /dev/sda
cryptsetup open /dev/sda topLuks
cryptsetup -y -v luksFormat /dev/mapper/topLuks
cryptsetup open /dev/mapper/topLuks bottomLuks
lsblk
Then you can make a filesystem and mount it:
mkfs.ext4 /dev/mapper/bottomLuks
mount /dev/mapper/bottomLuks ~/mnt/embeddedLuksTest
I’ve tested putting files on it and then unmounting & re-encrypting it, and the files are indeed still there upon decrypting and re-mounting.
Again, sorry if this is not news to anyone else, but I didn’t realise this was possible before, and thought it was very cool when I found it out. Sharing in case other people didn’t know and also find it cool :)
we really ain’t making any jokes on the name of the drives? okay…
Well considdering it was posted by a user with the username “communism” i will assume bottomLuks
Communism doesn’t have hierarchy tho
That’s very true.
But Marxist-Leninism (Lemmy.ml), the attempt to make communism practical and achievable and bumbling into fascism, does have a hierarchy.
Actually the bottomLuks generates most of the power.
Speed has everything to do with it.
Yes, perhaps I should have named them
outerLuksandinnerLuks… oh well lol
Yeah, LUKS and most block level overlays just don’t care. That’s what good abstraction layers do for you!
You can LUKS on a disk image mounted over SSHFS that itself resides on a Ceph cluster and mounted over iSCSI for all it cares. Is it a block device? Yes? Good to go.
You can even LUKS a floppy if you want. Or a CD.
You wouldn’t LUKS a floppy?
I absolutely will, if I can find one
And a suitable reader that my computer knows how to talk to.
Connections to the reader need to be encrypted or I don’t want it
I remember years ago investigating alternatives to VMware vSAN and doing hyperconverged storage clusters in Red Hat with glusterFS in top of a couple of other layers. Feels rickety as heck putting it all together but it works well. Hard sell for “normal” people who expect to hit a Next button and get some pretty graphical chart though.
Never apologize for enjoying the discovery of new things. That’s awesome, enjoy it.
Now recursively create more layers until you have barely any free space left on the disk, then do some performance benchmarks. ;)
top / bottom
( ͡° ͜ʖ ͡°)
Great! Although I think that security actually goes down that way. Something something about statistics. A crypto expert could probably explain that properly and we could pretend to understand it.
You can, sure, but you probably shouldn’t. Encrypting and decrypting consume additional cpu time, and you won’t gain much in terms of security.
not really if you have a hardware chip that does the encrypt/decrypting
AES has been accelerated on all Intel CPUs since Broadwell, was common as far back as Sandy Bridge, and has been available since Westmere.
AMD has had AES acceleration since Bulldozer.
But the commenter is right that adding a second layer of encryption is useless in everything except very specific circumstances.
I’ve also found about this recently when moving my root from drive to drive which was after I upgraded to 13th gen intel (from various older i5s) and the best cipher changed (
cryptsetup benchmark).What circumstances would that be? I can’t see the use case doe this, but I’m open to see how and when that would be needed.
There’s a Wikipedia article on multiple encryption that talks about this, but the arguments are not that compelling to me.
The main thing is mostly about protecting your data from flawed implementations. Like, AES has not been broken theoretically, but a particular implementation may be broken. By stacking implementations from multiple vendors, you reduce the chance of being exposed by a vulnerability in one of them.
That’s way overkill for most businesses. That’s like nation state level paranoia.
Yes, but as I’ve found recently AES-NI is only as good as your software support for it. Had a team using an ancient version of winscp and they kept complaining about download speeds on our 10Gb circuit. Couldn’t replicate it on any other machine with the newest version of winscp so I installed their exact version. AES-NI support wasn’t added until like 2020 and it gave them 5x better download speed after upgrading.
agreed that it is useless for most cases but I could see it being useful if you need multiple people to agree on decrypting a file.
multiple people to agree on decrypting a file
For that, you would use Shamir’s Secret Sharing algorithm rather than multiple encryption.
that’s another way, I guess… if you want to split the file, that is
No, you don’t split the file. You split the master decryption key.
Each user just needs to remember their own password, and SSS can reconstruct the master key when enough users enter their passwords.
That’s pretty nitty although you can always just partition a long key and distribute the partitions to the different people
there’s always more than one way to skin a rat
Does cryptsetup/luks do that? I thought that was only software encryption.
It does if the CPU supports it. Otherwise i/o would be stupidly slow, AES is expensive
it depends if your hardware supports the algos that cryptsetup/luks use I guess…
It would be good if you wanted to have a system that two people need to be present to unlock. Like those nuke launch locks that need two keys.
You can also just split the password for a single LUKS into two parts and give one each to the two people :D
Yeah, you’re right. That’s better.
But then you know both parts of the password and so must be killed to keep the machine secure
Tbf this would enforce the order in which the two people decrypt it, which may not be good if you expect these two people to “arrive” asyncrhonously and you don’t want them to have to wait for the other before entering their password/key. But maybe that’s too specific of a use case.
You’re a programmer, aren’t you? Always thinking about those race conditions and edge cases.
Definitely not professionally lol. I think I’d only want a programming job if I could somehow develop FOSS for a living, which is hard to get a full-time job in. And only to a limited extent as a hobby, though I do enjoy programming and am trying to teach myself more whenever I have the time :)
Didn’t account for the 2 sticky notes cleverly hidden under they keyboard.
That’s cool and I hope I never see that in the wild
Why not?
Seems like it would be fairly inefficient having to encrypt and decrypt data twice.
Not only twice but two streams sequentially on the same hardware
I guess your…Luks not running out.
Take my angry upvote, you heathen.
If you think about, it makes sense, but I didn’t know this! Really cool indeed - do you have any use case for that or you were just poking around?
I have an SSD and an HDD—I was considering on my next distro hop to put the root partition on the SSD and home partition on the HDD, decrypt the SSD and top level of the HDD upon boot, then decrypt the bottom level of the HDD upon user login. I’m sure many will think that’s overkill or silly, but hey, if you have full disk encryption you’ll have to enter two passwords to get into your computer anyway, just means your personal files get protected with two passwords. I would agree it’s mostly gimmicky but I still want to try it out lol
Amazing! How do you setup the decryption on login? systemd-home or something like that?
Fancy! TIL about pam_mount. Thanks, comrade!
Is it possible to… boot into a LUKS in a LUKS?
Have fun with the initramfs.
Where’s the ZFS love…
deleted by creator
Why not? Even my physical door have top-locks and bottom-locks… get your mind out of the gutter! :)
