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51 lines
2.5 KiB
51 lines
2.5 KiB
10 years ago
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# Directions for changing a system from password-based gpg keyfile
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# to smartcard-based gpg keyfile
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# Be sure that you meet the following requirements:
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# 1. GnuPG >= 2.1 installed with
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# * Smartcard support enabled (scdaemon must be built)
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# * Direct CCID access built into scdaemon
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# 2. A password-based gpg keyfile ${KEYFILE} (e.g. "keyfile.gpg"):
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# That is, a file containing the slot key for LUKS, which
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# has been encrypted symmetrically with GnuPG using
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# a password.
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# 3. Your public OpenPGP identity ${RECIPIENT} (e.g. "3A696356")
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# 4. An OpenPGP smartcard holding the decryption key associated
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# with your public identity
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# 5. A CCID smartcard reader
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# Notes: Requirement 4. and 5. can of course be one device, e.g.
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# a USB token with an integrated OpenPGP smartcard
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# Make a backup of your keyfile (assuming it lies on the boot partition)
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$ cp /boot/${KEYFILE} /safe/place/keyfile.bak.gpg
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# Change your keyfile from purely password-based to both
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# password-based and key-based (you can then decrypt the keyfile
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# with either method). As an example aes256 is chosen, the cipher
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# is not important to this guide, but do note that your kernel
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# must support it at boot time (be it built into the kernel image
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# or loaded as a module from the initramfs).
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$ cat /safe/place/keyfile.bak.gpg | gpg -d | gpg --encrypt --recipient ${RECIPIENT} --cipher-algo aes256 --armor -c > /safe/place/keyfile_sc.gpg
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# Verify that you can decrypt your new keyfile both with the password
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# and your smartcard.
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# (with smartcard inserted, you should be prompted for your PIN, unless
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# you already did so and have not yet timed out)
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$ gpg -d /safe/place/keyfile_sc.gpg
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# (with smartcard disconnected, you should be prompted for your password)
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$ gpg -d /safe/place/keyfile_sc.gpg
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# After verification, replace your old keyfile with your new one
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$ su -c 'cp /safe/place/keyfile_sc.gpg /boot/${KEYFILE}'
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# Export your public key to where crypt-gpg can find it
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$ gpg --armor --export-options export-minimal --export ${RECIPIENT} > /safe/place/crypt-public-key.gpg
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$ su -c 'cp /safe/place/crypt-public-key.gpg /etc/dracut.conf.d/crypt-public-key.gpg'
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# Rebuild your initramfs as usual
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# When booting with any of the requirements not met, crypt-gpg will default to password-based keyfile unlocking.
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# If all requirements are met and smartcard support is not disabled by setting the kernel option "rd.luks.smartcard=0"
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# crypt-gpg will try find and use a connected OpenPGP smartcard by prompting you for the PIN and then
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# unlocking the gpg keyfile with the smartcard.
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