{ 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, yubikey, gpgCard, fido2, fallbackToPassword, preOpenCommands, postOpenCommands,... }: assert name' == name; let csopen = "cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} ${optionalString (header != null) "--header=${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 ${optionalString yubikey.twoFactor '' echo -n "Enter two-factor passphrase: " read -r k_user echo ''} if [ ! -z "$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 [ $? == 0 ]; then opened=true break else opened=false echo "Authentication failed!" fi done [ "$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 -i 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 } ''} # commands to run right before we mount our device ${preOpenCommands} ${if (luks.yubikeySupport && (yubikey != null)) || (luks.gpgSupport && (gpgCard != null)) || (luks.fido2Support && (fido2.credential != null)) 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 { 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 . 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 cryptsetup luksSuspend. 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 /dev/mapper/name. ''; type = with types; loaOf (submodule ( { name, ... }: { options = { name = mkOption { visible = false; default = name; example = "luksroot"; type = types.str; description = "Name of the unencrypted device in /dev/mapper."; }; 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 keyFile will be used decryption, instead of just the first keyFileSize bytes. ''; }; keyFileOffset = mkOption { default = null; example = 4096; type = types.nullOr types.int; description = '' The offset of the key file. Use this in combination with keyFileSize 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 keyFile. ''; }; # 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. ''; }; 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 Trezor. ''; }; }; 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 "/". ''; }; }; }; }); }; 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. ''; }; }; 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.fido2Support && luks.yubikeySupport); message = "FIDO2 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 = '' 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 <