From 2cb7e0aaedad73b076ea18c6900b0e86c5760d79 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 15:00:47 +0200 Subject: Adding upstream version 247.3. Signed-off-by: Daniel Baumann --- man/yubikey-crypttab.sh | 50 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 man/yubikey-crypttab.sh (limited to 'man/yubikey-crypttab.sh') diff --git a/man/yubikey-crypttab.sh b/man/yubikey-crypttab.sh new file mode 100644 index 0000000..651246d --- /dev/null +++ b/man/yubikey-crypttab.sh @@ -0,0 +1,50 @@ +# Make sure no one can read the files we generate but us +umask 077 + +# Destroy any old key on the Yubikey (careful!) +ykman piv reset + +# Generate a new private/public key pair on the device, store the public key in 'pubkey.pem'. +ykman piv generate-key -a RSA2048 9d pubkey.pem + +# Create a self-signed certificate from this public key, and store it on the +# device. The "subject" should be an arbitrary string to identify the token in +# the p11tool output below. +ykman piv generate-certificate --subject "Knobelei" 9d pubkey.pem + +# Check if the newly create key on the Yubikey shows up as token in PKCS#11. Have a look at the output, and +# copy the resulting token URI to the clipboard. +p11tool --list-tokens + +# Generate a (secret) random key to use as LUKS decryption key. +dd if=/dev/urandom of=plaintext.bin bs=128 count=1 + +# Encode the secret key also as base64 text (with all whitespace removed) +base64 < plaintext.bin | tr -d '\n\r\t ' > plaintext.base64 + +# Encrypt this newly generated (binary) LUKS decryption key using the public key whose private key is on the +# Yubikey, store the result in /etc/cryptsetup-keys.d/mytest.key, where we'll look for it during boot. +mkdir -p /etc/cryptsetup-keys.d +sudo openssl rsautl -encrypt -pubin -inkey pubkey.pem -in plaintext.bin -out /etc/cryptsetup-keys.d/mytest.key + +# Configure the LUKS decryption key on the LUKS device. We use very low pbkdf settings since the key already +# has quite a high quality (it comes directly from /dev/urandom after all), and thus we don't need to do much +# key derivation. Replace /dev/sdXn by the partition to use (e.g. sda1) +sudo cryptsetup luksAddKey /dev/sdXn plaintext.base64 --pbkdf=pbkdf2 --pbkdf-force-iterations=1000 + +# Now securely delete the plain text LUKS key, we don't need it anymore, and since it contains secret key +# material it should be removed from disk thoroughly. +shred -u plaintext.bin plaintext.base64 + +# We don't need the public key anymore either, let's remove it too. Since this one is not security +# sensitive we just do a regular "rm" here. +rm pubkey.pem + +# Test: Let's run systemd-cryptsetup to test if this all worked. The option string should contain the full +# PKCS#11 URI we have in the clipboard; it tells the tool how to decipher the encrypted LUKS key. Note that +# systemd-cryptsetup automatically searches for the encrypted key in /etc/cryptsetup-keys.d/, hence we do +# not need to specify the key file path explicitly here. +sudo systemd-cryptsetup attach mytest /dev/sdXn - 'pkcs11-uri=pkcs11:…' + +# If that worked, let's now add the same line persistently to /etc/crypttab, for the future. +sudo bash -c 'echo "mytest /dev/sdXn - \'pkcs11-uri=pkcs11:…\'" >> /etc/crypttab' -- cgit v1.2.3