2019-10-23 16:13:23 +02:00
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# luksrku
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luksrku is a tool that allows you to remotely unlock LUKS disks during bootup
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from within your initrd. The intention is to have full-disk-encryption with
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LUKS-rootfs running headlessly. You should be able to remotely unlock their
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LUKS cryptographic file systems when you know they have been (legitimately)
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rebooted.
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This works as follows: The luksrku client (which needs unlocking) and luksrku
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server (which holds all the LUKS keys) share a secret. The client either knows
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the address of the server or it can issue a broadcast in the network to find
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the correct one. With the help of the shared secret, a TLS connection is
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established betweem the client and a legitimate server (who also knows the same
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secret). The server then tells the client all the LUKS passphrases, which
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performs luksOpen on all volumes.
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## Security
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luksrku uses TLSv1.3-PSK with forward-secrecy key shares (i.e., ECDHE). The
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curves that are used are X448 and X25519 for key agreement and
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TLS_CHACHA20_POLY1305_SHA256 or TLS_AES_256_GCM_SHA384 as cipher suites. PSKs
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are 256 bit long and randomly generated (/dev/urandom). Likewise, the LUKS
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passphrases are based on 256 bit long secrets and are converted to Base64 for
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easier handling (when setting up everything initially).
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The binary protocol that runs between both is intentionally extremely simple to
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allow for easy code review.
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The key database is encrypted itself, using AES256-GCM, a 128 bit randomized
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initialization vector and authenticated with a 128 bit authentication tag. Key
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derivation is done using scrypt with N = 131072 = 2^18, r = 8, p = 1.
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## Dependencies
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OpenSSL v1.1 is required for luksrku.
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## Example
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TODO
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