{ config, lib, pkgs, ... }:
with lib;
let
luks = config.boot.initrd.luks;
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, fallbackToPassword, ... }: 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
}
''}
${if (luks.yubikeySupport && (yubikey != null)) || (luks.gpgSupport && (gpgCard != null)) then ''
open_with_hardware
'' else ''
open_normally
''}
'';
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
{
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"
(if pkgs.stdenv.hostPlatform.system == "x86_64-linux" then "aes_x86_64" else "aes_i586")
];
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; loaOf (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.
'';
};
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.";
};
};
});
};
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 "/".
'';
};
};
};
});
};
};
}));
};
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.
'';
};
};
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.";
}
];
# 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 > $out/bin/openssl-wrap <<EOF
#!$out/bin/sh
export OPENSSL_CONF=$out/etc/ssl/openssl.cnf
$out/bin/openssl "\$@"
EOF
chmod +x $out/bin/openssl-wrap
''}
${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)
}
''}
'';
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
''}
'';
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 ];
};
}