path: root/modules/luksroot.nix

{ config, lib, pkgs, ... }:

with lib;

let
  luks = config.boot.initrd.luks;
  kernelPackages = config.boot.kernelPackages;

  commonFunctions = ''
    die() {
        echo "$@" >&2
        exit 1
    }

    dev_exist() {
        local target="$1"
        if [ -e $target ]; then
            return 0
        else
            local uuid=$(echo -n $target | sed -e 's,UUID=\(.*\),\1,g')
            blkid --uuid $uuid >/dev/null
            return $?
        fi
    }

    wait_target() {
        local name="$1"
        local target="$2"
        local secs="''${3:-10}"
        local desc="''${4:-$name $target to appear}"

        if ! dev_exist $target; then
            echo -n "Waiting $secs seconds for $desc..."
            local success=false;
            for try in $(seq $secs); do
                echo -n "."
                sleep 1
                if dev_exist $target; then
                    success=true
                    break
                fi
            done
            if [ $success == true ]; then
                echo " - success";
                return 0
            else
                echo " - failure";
                return 1
            fi
        fi
        return 0
    }

    wait_yubikey() {
        local secs="''${1:-10}"

        ykinfo -v 1>/dev/null 2>&1
        if [ $? != 0 ]; then
            echo -n "Waiting $secs seconds for YubiKey to appear..."
            local success=false
            for try in $(seq $secs); do
                echo -n .
                sleep 1
                ykinfo -v 1>/dev/null 2>&1
                if [ $? == 0 ]; then
                    success=true
                    break
                fi
            done
            if [ $success == true ]; then
                echo " - success";
                return 0
            else
                echo " - failure";
                return 1
            fi
        fi
        return 0
    }

    wait_gpgcard() {
        local secs="''${1:-10}"

        gpg --card-status > /dev/null 2> /dev/null
        if [ $? != 0 ]; then
            echo -n "Waiting $secs seconds for GPG Card to appear"
            local success=false
            for try in $(seq $secs); do
                echo -n .
                sleep 1
                gpg --card-status > /dev/null 2> /dev/null
                if [ $? == 0 ]; then
                    success=true
                    break
                fi
            done
            if [ $success == true ]; then
                echo " - success";
                return 0
            else
                echo " - failure";
                return 1
            fi
        fi
        return 0
    }
  '';

  preCommands = ''
    # A place to store crypto things

    # A ramfs is used here to ensure that the file used to update
    # the key slot with cryptsetup will never get swapped out.
    # Warning: Do NOT replace with tmpfs!
    mkdir -p /crypt-ramfs
    mount -t ramfs none /crypt-ramfs

    # Cryptsetup locking directory
    mkdir -p /run/cryptsetup

    # For YubiKey salt storage
    mkdir -p /crypt-storage

    ${optionalString luks.gpgSupport ''
    export GPG_TTY=$(tty)
    export GNUPGHOME=/crypt-ramfs/.gnupg

    gpg-agent --daemon --scdaemon-program $out/bin/scdaemon > /dev/null 2> /dev/null
    ''}

    # Disable all input echo for the whole stage. We could use read -s
    # instead but that would ocasionally leak characters between read
    # invocations.
    stty -echo
  '';

  postCommands = ''
    stty echo
    umount /crypt-storage 2>/dev/null
    umount /crypt-ramfs 2>/dev/null
  '';

  openCommand = name': { name, device, header, keyFile, keyFileSize, keyFileOffset, allowDiscards, bypassWorkqueues, yubikey, gpgCard, fido2, clevis, dmi, fallbackToPassword, preOpenCommands, postOpenCommands, ... }: assert name' == name;
  let
    csopen   = "cryptsetup luksOpen ${device} ${name}"
             + optionalString allowDiscards " --allow-discards"
             + optionalString bypassWorkqueues " --perf-no_read_workqueue --perf-no_write_workqueue"
             + optionalString (header != null) " --header=${header}";
    cschange = "cryptsetup luksChangeKey ${device} ${optionalString (header != null) "--header=${header}"}";
  in ''
    # Wait for luksRoot (and optionally keyFile and/or header) to appear, e.g.
    # if on a USB drive.
    wait_target "device" ${device} || die "${device} is unavailable"

    ${optionalString (header != null) ''
      wait_target "header" ${header} || die "${header} is unavailable"
    ''}

    do_open_passphrase() {
        local passphrase

        while true; do
            echo -n "Passphrase for ${device}: "
            passphrase=
            while true; do
                if [ -e /crypt-ramfs/passphrase ]; then
                    echo "reused"
                    passphrase=$(cat /crypt-ramfs/passphrase)
                    break
                else
                    # ask cryptsetup-askpass
                    echo -n "${device}" > /crypt-ramfs/device

                    # and try reading it from /dev/console with a timeout
                    IFS= read -t 1 -r passphrase
                    if [ -n "$passphrase" ]; then
                       ${if luks.reusePassphrases then ''
                         # remember it for the next device
                         echo -n "$passphrase" > /crypt-ramfs/passphrase
                       '' else ''
                         # Don't save it to ramfs. We are very paranoid
                       ''}
                       echo
                       break
                    fi
                fi
            done
            echo -n "Verifying passphrase for ${device}..."
            echo -n "$passphrase" | ${csopen} --key-file=-
            if [ $? == 0 ]; then
                echo " - success"
                ${if luks.reusePassphrases then ''
                  # we don't rm here because we might reuse it for the next device
                '' else ''
                  rm -f /crypt-ramfs/passphrase
                ''}
                break
            else
                echo " - failure"
                # ask for a different one
                rm -f /crypt-ramfs/passphrase
            fi
        done
    }

    # LUKS
    open_normally() {
        ${if (keyFile != null) then ''
        if wait_target "key file" ${keyFile}; then
            ${csopen} --key-file=${keyFile} \
              ${optionalString (keyFileSize != null) "--keyfile-size=${toString keyFileSize}"} \
              ${optionalString (keyFileOffset != null) "--keyfile-offset=${toString keyFileOffset}"}
        else
            ${if fallbackToPassword then "echo" else "die"} "${keyFile} is unavailable"
            echo " - failing back to interactive password prompt"
            do_open_passphrase
        fi
        '' else ''
        do_open_passphrase
        ''}
    }

    ${optionalString (luks.yubikeySupport && (yubikey != null)) ''
    # YubiKey
    rbtohex() {
        ( od -An -vtx1 | tr -d ' \n' )
    }

    hextorb() {
        ( tr '[:lower:]' '[:upper:]' | sed -e 's/\([0-9A-F]\{2\}\)/\\\\\\x\1/gI' | xargs printf )
    }

    do_open_yubikey() {
        # Make all of these local to this function
        # to prevent their values being leaked
        local salt
        local iterations
        local k_user
        local challenge
        local response
        local k_luks
        local opened
        local new_salt
        local new_iterations
        local new_challenge
        local new_response
        local new_k_luks

        mount -t ${yubikey.storage.fsType} ${yubikey.storage.device} /crypt-storage || \
          die "Failed to mount YubiKey salt storage device"

        salt="$(cat /crypt-storage${yubikey.storage.path} | sed -n 1p | tr -d '\n')"
        iterations="$(cat /crypt-storage${yubikey.storage.path} | sed -n 2p | tr -d '\n')"
        challenge="$(echo -n $salt | openssl-wrap dgst -binary -sha512 | rbtohex)"
        response="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"

        for try in $(seq 3); do
            ${optionalString yubikey.twoFactor ''
            echo -n "Enter two-factor passphrase: "
            k_user=
            while true; do
                if [ -e /crypt-ramfs/passphrase ]; then
                    echo "reused"
                    k_user=$(cat /crypt-ramfs/passphrase)
                    break
                else
                    # Try reading it from /dev/console with a timeout
                    IFS= read -t 1 -r k_user
                    if [ -n "$k_user" ]; then
                       ${if luks.reusePassphrases then ''
                         # Remember it for the next device
                         echo -n "$k_user" > /crypt-ramfs/passphrase
                       '' else ''
                         # Don't save it to ramfs. We are very paranoid
                       ''}
                       echo
                       break
                    fi
                fi
            done
            ''}

            if [ ! -z "$k_user" ]; then
                k_luks="$(echo -n $k_user | pbkdf2-sha512 ${toString yubikey.keyLength} $iterations $response | rbtohex)"
            else
                k_luks="$(echo | pbkdf2-sha512 ${toString yubikey.keyLength} $iterations $response | rbtohex)"
            fi

            echo -n "$k_luks" | hextorb | ${csopen} --key-file=-

            if [ $? == 0 ]; then
                opened=true
                ${if luks.reusePassphrases then ''
                  # We don't rm here because we might reuse it for the next device
                '' else ''
                  rm -f /crypt-ramfs/passphrase
                ''}
                break
            else
                opened=false
                echo "Authentication failed!"
            fi
        done

        [ "$opened" == false ] && die "Maximum authentication errors reached"

        echo -n "Gathering entropy for new salt (please enter random keys to generate entropy if this blocks for long)..."
        for i in $(seq ${toString yubikey.saltLength}); do
            byte="$(dd if=/dev/random bs=1 count=1 2>/dev/null | rbtohex)";
            new_salt="$new_salt$byte";
            echo -n .
        done;
        echo "ok"

        new_iterations="$iterations"
        ${optionalString (yubikey.iterationStep > 0) ''
        new_iterations="$(($new_iterations + ${toString yubikey.iterationStep}))"
        ''}

        new_challenge="$(echo -n $new_salt | openssl-wrap dgst -binary -sha512 | rbtohex)"

        new_response="$(ykchalresp -${toString yubikey.slot} -x $new_challenge 2>/dev/null)"

        if [ ! -z "$k_user" ]; then
            new_k_luks="$(echo -n $k_user | pbkdf2-sha512 ${toString yubikey.keyLength} $new_iterations $new_response | rbtohex)"
        else
            new_k_luks="$(echo | pbkdf2-sha512 ${toString yubikey.keyLength} $new_iterations $new_response | rbtohex)"
        fi

        echo -n "$new_k_luks" | hextorb > /crypt-ramfs/new_key
        echo -n "$k_luks" | hextorb | ${cschange} --key-file=- /crypt-ramfs/new_key

        if [ $? == 0 ]; then
            echo -ne "$new_salt\n$new_iterations" > /crypt-storage${yubikey.storage.path}
        else
            echo "Warning: Could not update LUKS key, current challenge persists!"
        fi

        rm -f /crypt-ramfs/new_key
        umount /crypt-storage
    }

    open_with_hardware() {
        if wait_yubikey ${toString yubikey.gracePeriod}; then
            do_open_yubikey
        else
            echo "No YubiKey found, falling back to non-YubiKey open procedure"
            open_normally
        fi
    }
    ''}

    ${optionalString (luks.gpgSupport && (gpgCard != null)) ''

    do_open_gpg_card() {
        # Make all of these local to this function
        # to prevent their values being leaked
        local pin
        local opened

        gpg --import /gpg-keys/${device}/pubkey.asc > /dev/null 2> /dev/null

        gpg --card-status > /dev/null 2> /dev/null

        for try in $(seq 3); do
            echo -n "PIN for GPG Card associated with device ${device}: "
            pin=
            while true; do
                if [ -e /crypt-ramfs/passphrase ]; then
                    echo "reused"
                    pin=$(cat /crypt-ramfs/passphrase)
                    break
                else
                    # and try reading it from /dev/console with a timeout
                    IFS= read -t 1 -r pin
                    if [ -n "$pin" ]; then
                       ${if luks.reusePassphrases then ''
                         # remember it for the next device
                         echo -n "$pin" > /crypt-ramfs/passphrase
                       '' else ''
                         # Don't save it to ramfs. We are very paranoid
                       ''}
                       echo
                       break
                    fi
                fi
            done
            echo -n "Verifying passphrase for ${device}..."
            echo -n "$pin" | gpg -q --batch --passphrase-fd 0 --pinentry-mode loopback -d /gpg-keys/${device}/cryptkey.gpg 2> /dev/null | ${csopen} --key-file=- > /dev/null 2> /dev/null
            if [ $? == 0 ]; then
                echo " - success"
                ${if luks.reusePassphrases then ''
                  # we don't rm here because we might reuse it for the next device
                '' else ''
                  rm -f /crypt-ramfs/passphrase
                ''}
                break
            else
                echo " - failure"
                # ask for a different one
                rm -f /crypt-ramfs/passphrase
            fi
        done

        [ "$opened" == false ] && die "Maximum authentication errors reached"
    }

    open_with_hardware() {
        if wait_gpgcard ${toString gpgCard.gracePeriod}; then
            do_open_gpg_card
        else
            echo "No GPG Card found, falling back to normal open procedure"
            open_normally
        fi
    }
    ''}

    ${optionalString (luks.fido2Support && (fido2.credential != null)) ''

    open_with_hardware() {
      local passsphrase

        ${if fido2.passwordLess then ''
          export passphrase=""
        '' else ''
          read -rsp "FIDO2 salt for ${device}: " passphrase
          echo
        ''}
        ${optionalString (lib.versionOlder kernelPackages.kernel.version "5.4") ''
          echo "On systems with Linux Kernel < 5.4, it might take a while to initialize the CRNG, you might want to use linuxPackages_latest."
          echo "Please move your mouse to create needed randomness."
        ''}
          echo "Waiting for your FIDO2 device..."
          fido2luks open ${device} ${name} ${fido2.credential} --await-dev ${toString fido2.gracePeriod} --salt string:$passphrase
        if [ $? -ne 0 ]; then
          echo "No FIDO2 key found, falling back to normal open procedure"
          open_normally
        fi
    }
    ''}

    ${optionalString (luks.clevisSupport && clevis) ''

    open_with_hardware() {
      mkdir -p /crypt-ramfs/clevis

      TMPDIR=/crypt-ramfs/clevis clevis luks unlock -d ${device} -n ${name}

      if [ $? -ne 0 ]; then
        echo "Unlocking with clevis failed, falling back to normal open procedure"
        open_normally
      fi
    }

    ''}

    ${optionalString (luks.dmiSupport && dmi) ''

    open_with_hardware() {
      dmidecode -s system-uuid > /crypt-ramfs/passphrase

      ${csopen} --key-file=- < /crypt-ramfs/passphrase > /dev/null 2> /dev/null

      if [ $? -ne 0 ]; then
        echo "Unlocking with system-uuid failed, falling back to normal open procedure"
        rm -f /crypt-ramfs/passphrase
        open_normally
      ${optionalString (!luks.reusePassphrases) ''
        else
          rm -f /crypt-ramfs/passphrase
      ''}
      fi
    }

    ''}

    # commands to run right before we mount our device
    ${preOpenCommands}

    ${if (luks.yubikeySupport && (yubikey != null)) || (luks.gpgSupport && (gpgCard != null)) || (luks.fido2Support && (fido2.credential != null)) || (luks.clevisSupport && clevis) || (luks.dmiSupport && dmi) then ''
    open_with_hardware
    '' else ''
    open_normally
    ''}

    # commands to run right after we mounted our device
    ${postOpenCommands}
  '';

  askPass = pkgs.writeScriptBin "cryptsetup-askpass" ''
    #!/bin/sh

    ${commonFunctions}

    while true; do
        wait_target "luks" /crypt-ramfs/device 10 "LUKS to request a passphrase" || die "Passphrase is not requested now"
        device=$(cat /crypt-ramfs/device)

        echo -n "Passphrase for $device: "
        IFS= read -rs passphrase
        echo

        rm /crypt-ramfs/device
        echo -n "$passphrase" > /crypt-ramfs/passphrase
    done
  '';

  preLVM = filterAttrs (n: v: v.preLVM) luks.devices;
  postLVM = filterAttrs (n: v: !v.preLVM) luks.devices;

in
{
  disabledModules = [ "system/boot/luksroot.nix" ];
  
  imports = [
    (mkRemovedOptionModule [ "boot" "initrd" "luks" "enable" ] "")
  ];

  options = {

    boot.initrd.luks.mitigateDMAAttacks = mkOption {
      type = types.bool;
      default = true;
      description = ''
        Unless enabled, encryption keys can be easily recovered by an attacker with physical
        access to any machine with PCMCIA, ExpressCard, ThunderBolt or FireWire port.
        More information is available at <link xlink:href="http://en.wikipedia.org/wiki/DMA_attack"/>.

        This option blacklists FireWire drivers, but doesn't remove them. You can manually
        load the drivers if you need to use a FireWire device, but don't forget to unload them!
      '';
    };

    boot.initrd.luks.cryptoModules = mkOption {
      type = types.listOf types.str;
      default =
        [ "aes" "aes_generic" "blowfish" "twofish"
          "serpent" "cbc" "xts" "lrw" "sha1" "sha256" "sha512"
          "af_alg" "algif_skcipher"
        ];
      description = ''
        A list of cryptographic kernel modules needed to decrypt the root device(s).
        The default includes all common modules.
      '';
    };

    boot.initrd.luks.forceLuksSupportInInitrd = mkOption {
      type = types.bool;
      default = false;
      internal = true;
      description = ''
        Whether to configure luks support in the initrd, when no luks
        devices are configured.
      '';
    };

    boot.initrd.luks.reusePassphrases = mkOption {
      type = types.bool;
      default = true;
      description = ''
        When opening a new LUKS device try reusing last successful
        passphrase.

        Useful for mounting a number of devices that use the same
        passphrase without retyping it several times.

        Such setup can be useful if you use <command>cryptsetup
        luksSuspend</command>. Different LUKS devices will still have
        different master keys even when using the same passphrase.
      '';
    };

    boot.initrd.luks.devices = mkOption {
      default = { };
      example = { luksroot.device = "/dev/disk/by-uuid/430e9eff-d852-4f68-aa3b-2fa3599ebe08"; };
      description = ''
        The encrypted disk that should be opened before the root
        filesystem is mounted. Both LVM-over-LUKS and LUKS-over-LVM
        setups are supported. The unencrypted devices can be accessed as
        <filename>/dev/mapper/<replaceable>name</replaceable></filename>.
      '';

      type = with types; attrsOf (submodule (
        { name, ... }: { options = {

          name = mkOption {
            visible = false;
            default = name;
            example = "luksroot";
            type = types.str;
            description = "Name of the unencrypted device in <filename>/dev/mapper</filename>.";
          };

          device = mkOption {
            example = "/dev/disk/by-uuid/430e9eff-d852-4f68-aa3b-2fa3599ebe08";
            type = types.str;
            description = "Path of the underlying encrypted block device.";
          };

          header = mkOption {
            default = null;
            example = "/root/header.img";
            type = types.nullOr types.str;
            description = ''
              The name of the file or block device that
              should be used as header for the encrypted device.
            '';
          };

          keyFile = mkOption {
            default = null;
            example = "/dev/sdb1";
            type = types.nullOr types.str;
            description = ''
              The name of the file (can be a raw device or a partition) that
              should be used as the decryption key for the encrypted device. If
              not specified, you will be prompted for a passphrase instead.
            '';
          };

          keyFileSize = mkOption {
            default = null;
            example = 4096;
            type = types.nullOr types.int;
            description = ''
              The size of the key file. Use this if only the beginning of the
              key file should be used as a key (often the case if a raw device
              or partition is used as key file). If not specified, the whole
              <literal>keyFile</literal> will be used decryption, instead of just
              the first <literal>keyFileSize</literal> bytes.
            '';
          };

          keyFileOffset = mkOption {
            default = null;
            example = 4096;
            type = types.nullOr types.int;
            description = ''
              The offset of the key file. Use this in combination with
              <literal>keyFileSize</literal> to use part of a file as key file
              (often the case if a raw device or partition is used as a key file).
              If not specified, the key begins at the first byte of
              <literal>keyFile</literal>.
            '';
          };

          # FIXME: get rid of this option.
          preLVM = mkOption {
            default = true;
            type = types.bool;
            description = "Whether the luksOpen will be attempted before LVM scan or after it.";
          };

          allowDiscards = mkOption {
            default = false;
            type = types.bool;
            description = ''
              Whether to allow TRIM requests to the underlying device. This option
              has security implications; please read the LUKS documentation before
              activating it.
            '';
          };

          bypassWorkqueues = mkOption {
            default = false;
            type = types.bool;
            description = ''
              Whether to bypass dm-crypt's internal read and write workqueues.
              Enabling this should improve performance on SSDs; see
              <link xlink:href="https://wiki.archlinux.org/index.php/Dm-crypt/Specialties#Disable_workqueue_for_increased_solid_state_drive_(SSD)_performance">here</link>
              for more information. Needs Linux 5.9 or later.
            '';
          };

          fallbackToPassword = mkOption {
            default = false;
            type = types.bool;
            description = ''
              Whether to fallback to interactive passphrase prompt if the keyfile
              cannot be found. This will prevent unattended boot should the keyfile
              go missing.
            '';
          };

          gpgCard = mkOption {
            default = null;
            description = ''
              The option to use this LUKS device with a GPG encrypted luks password by the GPG Smartcard.
              If null (the default), GPG-Smartcard will be disabled for this device.
            '';

            type = with types; nullOr (submodule {
              options = {
                gracePeriod = mkOption {
                  default = 10;
                  type = types.int;
                  description = "Time in seconds to wait for the GPG Smartcard.";
                };

                encryptedPass = mkOption {
                  default = "";
                  type = types.path;
                  description = "Path to the GPG encrypted passphrase.";
                };

                publicKey = mkOption {
                  default = "";
                  type = types.path;
                  description = "Path to the Public Key.";
                };
              };
            });
          };

          fido2 = {
            credential = mkOption {
              default = null;
              example = "f1d00200d8dc783f7fb1e10ace8da27f8312d72692abfca2f7e4960a73f48e82e1f7571f6ebfcee9fb434f9886ccc8fcc52a6614d8d2";
              type = types.nullOr types.str;
              description = "The FIDO2 credential ID.";
            };

            gracePeriod = mkOption {
              default = 10;
              type = types.int;
              description = "Time in seconds to wait for the FIDO2 key.";
            };

            passwordLess = mkOption {
              default = false;
              type = types.bool;
              description = ''
                Defines whatever to use an empty string as a default salt.

                Enable only when your device is PIN protected, such as <link xlink:href="https://trezor.io/">Trezor</link>.
              '';
            };
          };

          yubikey = mkOption {
            default = null;
            description = ''
              The options to use for this LUKS device in YubiKey-PBA.
              If null (the default), YubiKey-PBA will be disabled for this device.
            '';

            type = with types; nullOr (submodule {
              options = {
                twoFactor = mkOption {
                  default = true;
                  type = types.bool;
                  description = "Whether to use a passphrase and a YubiKey (true), or only a YubiKey (false).";
                };

                slot = mkOption {
                  default = 2;
                  type = types.int;
                  description = "Which slot on the YubiKey to challenge.";
                };

                saltLength = mkOption {
                  default = 16;
                  type = types.int;
                  description = "Length of the new salt in byte (64 is the effective maximum).";
                };

                keyLength = mkOption {
                  default = 64;
                  type = types.int;
                  description = "Length of the LUKS slot key derived with PBKDF2 in byte.";
                };

                iterationStep = mkOption {
                  default = 0;
                  type = types.int;
                  description = "How much the iteration count for PBKDF2 is increased at each successful authentication.";
                };

                gracePeriod = mkOption {
                  default = 10;
                  type = types.int;
                  description = "Time in seconds to wait for the YubiKey.";
                };

                /* TODO: Add to the documentation of the current module:

                   Options related to the storing the salt.
                */
                storage = {
                  device = mkOption {
                    default = "/dev/sda1";
                    type = types.path;
                    description = ''
                      An unencrypted device that will temporarily be mounted in stage-1.
                      Must contain the current salt to create the challenge for this LUKS device.
                    '';
                  };

                  fsType = mkOption {
                    default = "vfat";
                    type = types.str;
                    description = "The filesystem of the unencrypted device.";
                  };

                  path = mkOption {
                    default = "/crypt-storage/default";
                    type = types.str;
                    description = ''
                      Absolute path of the salt on the unencrypted device with
                      that device's root directory as "/".
                    '';
                  };
                };
              };
            });
          };

          clevis = mkOption {
            type = types.bool;
            default = false;
            description = ''
              Unlock device via clevis (e.g. with a tpm)
            '';
          };

          dmi = mkOption {
            type = types.bool;
            default = false;
            description = ''
              Unlock device via system-uuid (via dmidecode)
            '';
          };

          preOpenCommands = mkOption {
            type = types.lines;
            default = "";
            example = ''
              mkdir -p /tmp/persistent
              mount -t zfs rpool/safe/persistent /tmp/persistent
            '';
            description = ''
              Commands that should be run right before we try to mount our LUKS device.
              This can be useful, if the keys needed to open the drive is on another partion.
            '';
          };

          postOpenCommands = mkOption {
            type = types.lines;
            default = "";
            example = ''
              umount /tmp/persistent
            '';
            description = ''
              Commands that should be run right after we have mounted our LUKS device.
            '';
          };
        };
      }));
    };

    boot.initrd.luks.gpgSupport = mkOption {
      default = false;
      type = types.bool;
      description = ''
        Enables support for authenticating with a GPG encrypted password.
      '';
    };

    boot.initrd.luks.yubikeySupport = mkOption {
      default = false;
      type = types.bool;
      description = ''
            Enables support for authenticating with a YubiKey on LUKS devices.
            See the NixOS wiki for information on how to properly setup a LUKS device
            and a YubiKey to work with this feature.
          '';
    };

    boot.initrd.luks.fido2Support = mkOption {
      default = false;
      type = types.bool;
      description = ''
        Enables support for authenticating with FIDO2 devices.
      '';
    };

    boot.initrd.luks.clevisSupport = mkOption {
      default = false;
      type = types.bool;
      description = ''
        Enables support for unlocking luks volumes via clevis (e.g. with a tpm)
      '';
    };
    
    boot.initrd.luks.dmiSupport = mkOption {
      default = false;
      type = types.bool;
      description = ''
        Enables support for unlocking luks volumes via system-uuid (via dmidecode)
      '';
    };

  };

  config = mkIf (luks.devices != {} || luks.forceLuksSupportInInitrd) {

    assertions =
      [ { assertion = !(luks.gpgSupport && luks.yubikeySupport);
          message = "YubiKey and GPG Card may not be used at the same time.";
        }

        { assertion = !(luks.gpgSupport && luks.fido2Support);
          message = "FIDO2 and GPG Card may not be used at the same time.";
        }

        { assertion = !(luks.gpgSupport && luks.clevisSupport);
          message = "Clevis and GPG Card may not be used at the same time.";
        }
        
        { assertion = !(luks.gpgSupport && luks.dmiSupport);
          message = "DMI and GPG Card may not be used at the same time.";
        }

        { assertion = !(luks.fido2Support && luks.yubikeySupport);
          message = "FIDO2 and YubiKey may not be used at the same time.";
        }

        { assertion = !(luks.fido2Support && luks.clevisSupport);
          message = "FIDO2 and Clevis may not be used at the same time.";
        }

        { assertion = !(luks.fido2Support && luks.dmiSupport);
          message = "FIDO2 and DMI may not be used at the same time.";
        }

        { assertion = !(luks.yubikeySupport && luks.clevisSupport);
          message = "Clevis and YubiKey may not be used at the same time.";
        }

        { assertion = !(luks.yubikeySupport && luks.dmiSupport);
          message = "DMI and YubiKey may not be used at the same time.";
        }

      ];

    # actually, sbp2 driver is the one enabling the DMA attack, but this needs to be tested
    boot.blacklistedKernelModules = optionals luks.mitigateDMAAttacks
      ["firewire_ohci" "firewire_core" "firewire_sbp2"];

    # Some modules that may be needed for mounting anything ciphered
    boot.initrd.availableKernelModules = [ "dm_mod" "dm_crypt" "cryptd" "input_leds" ]
      ++ luks.cryptoModules
      # workaround until https://marc.info/?l=linux-crypto-vger&m=148783562211457&w=4 is merged
      # remove once 'modprobe --show-depends xts' shows ecb as a dependency
      ++ (if builtins.elem "xts" luks.cryptoModules then ["ecb"] else []);

    # copy the cryptsetup binary and it's dependencies
    boot.initrd.extraUtilsCommands =
      let
        extraUtils = config.system.build.extraUtils;

        ipkgs = pkgs.appendOverlays [
          (final: prev: {
            tpm2-tss = prev.tpm2-tss.overrideAttrs (oldAttrs: {
              doCheck = false;
              patches = [];
              postPatch = ''
                patchShebangs script
              '';
              configureFlags = [];
            });
          })
        ];
      in ''
           copy_bin_and_libs ${pkgs.cryptsetup}/bin/cryptsetup
           copy_bin_and_libs ${askPass}/bin/cryptsetup-askpass
           sed -i s,/bin/sh,$out/bin/sh, $out/bin/cryptsetup-askpass

           ${optionalString luks.yubikeySupport ''
             copy_bin_and_libs ${pkgs.yubikey-personalization}/bin/ykchalresp
             copy_bin_and_libs ${pkgs.yubikey-personalization}/bin/ykinfo
             copy_bin_and_libs ${pkgs.openssl.bin}/bin/openssl

             cc -O3 -I${pkgs.openssl.dev}/include -L${pkgs.openssl.out}/lib ${./pbkdf2-sha512.c} -o pbkdf2-sha512 -lcrypto
             strip -s pbkdf2-sha512
             copy_bin_and_libs pbkdf2-sha512

             mkdir -p $out/etc/ssl
             cp -pdv ${pkgs.openssl.out}/etc/ssl/openssl.cnf $out/etc/ssl

             cat > $out/bin/openssl-wrap <<EOF
             #!$out/bin/sh
             export OPENSSL_CONF=$out/etc/ssl/openssl.cnf
             $out/bin/openssl "\$@"
             EOF
             chmod +x $out/bin/openssl-wrap
           ''}

           ${optionalString luks.fido2Support ''
             copy_bin_and_libs ${pkgs.fido2luks}/bin/fido2luks
           ''}


           ${optionalString luks.gpgSupport ''
             copy_bin_and_libs ${pkgs.gnupg}/bin/gpg
             copy_bin_and_libs ${pkgs.gnupg}/bin/gpg-agent
             copy_bin_and_libs ${pkgs.gnupg}/libexec/scdaemon

             ${concatMapStringsSep "\n" (x:
               if x.gpgCard != null then
                 ''
                   mkdir -p $out/secrets/gpg-keys/${x.device}
                   cp -a ${x.gpgCard.encryptedPass} $out/secrets/gpg-keys/${x.device}/cryptkey.gpg
                   cp -a ${x.gpgCard.publicKey} $out/secrets/gpg-keys/${x.device}/pubkey.asc
                 ''
               else ""
               ) (attrValues luks.devices)
             }
           ''}

           ${optionalString luks.clevisSupport ''
             for bin in ${ipkgs.tpm2-tools}/bin/* ${ipkgs.jose}/bin/* ${ipkgs.libpwquality}/bin/*; do
               if [ -L $bin ]; then
                 cp -v $bin $out/bin
               else
                 copy_bin_and_libs $bin
               fi
             done

             copy_bin_and_libs ${ipkgs.bash}/bin/bash
             for bin in ${ipkgs.clevis}/bin/* ${ipkgs.clevis}/bin/.*; do
               [ -f $bin -o -L $bin ] || continue

               substitute $bin $out/bin/$(basename $bin) \
                 --replace ${ipkgs.bash}/bin $out/bin \
                 --replace ${ipkgs.clevis}/bin $out/bin \
                 --replace ${ipkgs.tpm2-tools}/bin $out/bin \
                 --replace ${ipkgs.jose}/bin $out/bin \
                 --replace ${ipkgs.libpwquality}/bin $out/bin \
                 --replace ${ipkgs.coreutils}/bin $out/bin

               [ -x $bin ] && chmod +x $out/bin/$(basename $bin)
             done

             for lib in ${ipkgs.tpm2-tss}/lib/*.so*; do
               if [ -f $lib ]; then
                 patchelf --output $out/lib/$(basename $lib) $lib \
                   --set-rpath $out/lib
               else
                 cp -pdv $lib $out/lib
               fi
             done
           ''}

           ${optionalString luks.dmiSupport ''
             copy_bin_and_libs ${pkgs.dmidecode}/bin/dmidecode
           ''}
    '';

    boot.initrd.extraUtilsCommandsTest = ''
      $out/bin/cryptsetup --version
      ${optionalString luks.yubikeySupport ''
        $out/bin/ykchalresp -V
        $out/bin/ykinfo -V
        $out/bin/openssl-wrap version
      ''}
      ${optionalString luks.gpgSupport ''
        $out/bin/gpg --version
        $out/bin/gpg-agent --version
        $out/bin/scdaemon --version
      ''}
      ${optionalString luks.fido2Support ''
        $out/bin/fido2luks --version
      ''}
      ${optionalString luks.clevisSupport ''
        $out/bin/jose alg
      ''}
      ${optionalString luks.dmiSupport ''
        $out/bin/dmidecode --version
      ''}
    '';

    boot.initrd.preFailCommands = postCommands;
    boot.initrd.preLVMCommands = commonFunctions + preCommands + concatStrings (mapAttrsToList openCommand preLVM) + postCommands;
    boot.initrd.postDeviceCommands = commonFunctions + preCommands + concatStrings (mapAttrsToList openCommand postLVM) + postCommands;

    environment.systemPackages = [ pkgs.cryptsetup ];
  };
}