this post was submitted on 26 Aug 2025

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Debian, encrypted boot, how to increase password attempts? (slrpnk.net)

submitted 1 year ago by boredsquirrel@slrpnk.net to c/linux@lemmy.ml

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Since Debian 13 (Trixie), when using the default FDE which uses grub to decrypt the luks partition, I have a single attempt

When the password is mistyped there is a long pause (over 10 seconds) and then the error appears.

I already tried increasing the max tries, which seems to be set to 1 when a keyfile is used.

The config/script seems to be in /usr/share/initramfs-tools/scripts/local-top/cryptroot.

I copied that to /etc/initramfs-tools/scripts/local-top/cryptroot and replaced the value CRYPTTAB_OPTION_tries=1 with 10 using find/replace (ansible stuff).

I think this has no effect though and doing so (might be a different issue) breaks boot entirely 💀

More info:

by default when legacy boot (BIOS) is available, Debian will install grub to the MBR. This is where it happens
when forcing or prioritizing legacy boot and using GPT, debian somehow boots from a 300MB efi partition, the same happens though, one attempt

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[+] bacon_pdp@lemmy.world 4 points 1 year ago (4 children)

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[–] Blue_Morpho@lemmy.world 3 points 1 year ago (3 children)

I think he's referring to the 10 second pause between attempts. It's security theatre because you can replace the bootloader with one that doesn't pause.

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[–] derpgon@programming.dev 1 point 1 year ago (2 children)

Is it? I always though the password is hashed via Bcrypt (or similar) with very high difficulty so it takes some time to check

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[–] Blue_Morpho@lemmy.world 2 points 1 year ago (1 child)

Disk encryption is Luks not bcrypt and Luks timeouts are configurable.

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[–] derpgon@programming.dev 2 points 1 year ago

So, it is purely a software timeout and not hardware due to key derivation algorithm? That's partly understandable and partly a security hole if it can be disabled so easily.

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