Implement authentication for a LUKS device with a yubikey (HMAC-SHA1); supports simple challenge-response and two-factor authentication

This commit is contained in:
Moritz Maxeiner 2014-01-25 03:27:12 +01:00
parent 8f9300fb0e
commit 333f5caaf9

View file

@ -5,7 +5,7 @@ with pkgs.lib;
let
luks = config.boot.initrd.luks;
openCommand = { name, device, keyFile, keyFileSize, allowDiscards, ... }: ''
openCommand = { name, device, keyFile, keyFileSize, allowDiscards, yubikey, ... }: ''
# Wait for luksRoot to appear, e.g. if on a usb drive.
# XXX: copied and adapted from stage-1-init.sh - should be
# available as a function.
@ -31,9 +31,141 @@ let
fi
''}
${optionalString (luks.yubikeySupport && (yubikey != null)) ''
mkdir -p ${yubikey.challenge.mountPoint}
mount -t ${yubikey.challenge.fsType} ${toString yubikey.challenge.device} ${yubikey.challenge.mountPoint}
response="$(ykchalresp -${toString yubikey.yubikeySlot} "`cat ${yubikey.challenge.mountPoint}${yubikey.challenge.file}`" 2>/dev/null || true)"
if [ -z "$response" ]; then
echo -n "waiting 10 seconds for yubikey to appear..."
for try in $(seq 10); do
sleep 1
response="$(ykchalresp -${toString yubikey.yubikeySlot} "`cat ${yubikey.challenge.mountPoint}${yubikey.challenge.file}`" 2>/dev/null || true)"
if [ ! -z "$response" ]; then break; fi
echo -n .
done
echo "ok"
fi
${optionalString yubikey.twoFactor ''
if [ ! -z "$response" ]; then
echo -n "Enter two-factor passphrase: "
read -s passphrase
current_key="$passphrase$response"
fi
''}
${optionalString (!yubikey.twoFactor) ''
if [ ! -z "$response" ]; then
current_key="$response"
fi
''}
''}
# open luksRoot and scan for logical volumes
${optionalString ((!luks.yubikeySupport) || (yubikey == null)) ''
cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} \
${optionalString (keyFile != null) "--key-file=${keyFile} ${optionalString (keyFileSize != null) "--keyfile-size=${toString keyFileSize}"}"}
''}
${optionalString (luks.yubikeySupport && (yubikey != null)) ''
if [ -z "$response" ]; then
cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} \
${optionalString (keyFile != null) "--key-file=${keyFile} ${optionalString (keyFileSize != null) "--keyfile-size=${toString keyFileSize}"}"}
else
echo $current_key | cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} --key-file=-
if [ $? != "0" ]; then
for try in $(seq 3); do
${optionalString (!yubikey.twoFactor) ''
sleep 1
''}
${optionalString yubikey.twoFactor ''
echo -n "Enter two-factor passphrase: "
read -s passphrase
current_key="$passphrase$response"
''}
echo $current_key | cryptsetup luksOpen ${device} ${name} ${optionalString allowDiscards "--allow-discards"} --key-file=-
if [ $? == "0" ]; then break; fi
echo -n .
done
fi
mkdir -p ${yubikey.ramfsMountPoint}
# 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!
mount -t ramfs none ${yubikey.ramfsMountPoint}
update_failed=false
old_challenge=$(cat ${yubikey.challenge.mountPoint}${yubikey.challenge.file})
new_challenge=$(uuidgen)
if [ $? != "0" ]; then
for try in $(seq 10); do
sleep 1
new_challenge=$(uuidgen)
if [ $? == "0" ]; then break; fi
if [ $try -eq 10 ]; then update_failed=true; fi
done
fi
if [ "$update_failed" == false ]; then
echo $new_challenge > ${yubikey.challenge.mountPoint}${yubikey.challenge.file}
response="$(ykchalresp -${toString yubikey.yubikeySlot} "`cat ${yubikey.challenge.mountPoint}${yubikey.challenge.file}`" 2>/dev/null || true)"
if [ -z "$response" ]; then
echo -n "waiting 10 seconds for yubikey to appear..."
for try in $(seq 10); do
sleep 1
response="$(ykchalresp -${toString yubikey.yubikeySlot} "`cat ${yubikey.challenge.mountPoint}${yubikey.challenge.file}`" 2>/dev/null || true)"
if [ ! -z "$response" ]; then break; fi
echo -n .
done
echo "ok";
fi
if [ ! -z "$response" ]; then
${optionalString yubikey.twoFactor ''
new_key="$passphrase$response"
''}
${optionalString (!yubikey.twoFactor) ''
new_key="$response"
''}
echo $new_key > ${yubikey.ramfsMountPoint}/new_key
echo $current_key | cryptsetup luksChangeKey ${device} --key-file=- --key-slot ${toString yubikey.luksKeySlot} ${yubikey.ramfsMountPoint}/new_key
if [ $? != "0" ]; then
for try in $(seq 10); do
sleep 1
echo $current_key | cryptsetup luksChangeKey ${device} --key-file=- --key-slot ${toString yubikey.luksKeySlot} ${yubikey.ramfsMountPoint}/new_key
if [ $? == "0" ]; then break; fi
if [ $try -eq 10 ]; then update_failed=true; fi
done
fi
rm -f ${yubikey.ramfsMountPoint}/new_key
if [ "$update_failed" == true ]; then
echo $old_challenge > ${yubikey.challenge.mountPoint}${yubikey.challenge.file}
echo "Warning: Could not update luks header with new key for ${device}, old challenge restored!"
fi
else
echo $old_challenge > ${yubikey.challenge.mountPoint}${yubikey.challenge.file}
echo "Warning: No yubikey present to challenge for ${device}, old challenge restored!"
fi
else
echo "Warning: New challenge could not be obtained for ${device}, old challenge persists!"
fi
umount ${yubikey.ramfsMountPoint}
umount ${yubikey.challenge.mountPoint}
fi
''}
'';
isPreLVM = f: f.preLVM;
@ -139,10 +271,77 @@ in
'';
};
};
yubikey = mkOption {
default = null;
type = types.nullOr types.optionSet;
description = "TODO";
options = {
twoFactor = mkOption {
default = false;
type = types.bool;
description = "TODO";
};
yubikeySlot = mkOption {
default = 2;
type = types.int;
description = "TODO";
};
luksKeySlot = mkOption {
default = 1;
type = types.int;
description = "TODO";
};
challenge = mkOption {
type = types.optionSet;
description = "TODO";
options = {
device = mkOption {
default = /dev/sda1;
type = types.path;
description = "TODO";
};
fsType = mkOption {
default = "vfat";
type = types.string;
description = "TODO";
};
mountPoint = mkOption {
default = "/crypt-challenge";
type = types.string;
description = "TODO";
};
file = mkOption {
default = "/crypt-challenge";
type = types.string;
description = "TODO";
};
};
};
ramfsMountPoint = mkOption {
default = "/crypt-update";
type = types.string;
description = "TODO";
};
};
};
};
};
boot.initrd.luks.yubikeySupport = mkOption {
default = false;
type = types.bool;
description = "TODO";
};
};
config = mkIf (luks.devices != []) {
@ -162,10 +361,27 @@ in
cp -pdvn $lib $out/lib
cp -pvn $(readlink -f $lib) $out/lib
done
${optionalString luks.yubikeySupport ''
cp -pdv ${pkgs.utillinux}/bin/uuidgen $out/bin
for lib in $(ldd $out/bin/uuidgen |grep '=>' |grep /nix/store/ |cut -d' ' -f3); do
cp -pdvn $lib $out/lib
cp -pvn $(readlink -f $lib) $out/lib
done
cp -pdv ${pkgs.ykpers}/bin/ykchalresp $out/bin
for lib in $(ldd $out/bin/ykchalresp |grep '=>' |grep /nix/store/ |cut -d' ' -f3); do
cp -pdvn $lib $out/lib
cp -pvn $(readlink -f $lib) $out/lib
done
''}
'';
boot.initrd.extraUtilsCommandsTest = ''
$out/bin/cryptsetup --version
${optionalString luks.yubikeySupport ''
$out/bin/uuidgen --version
$out/bin/ykchalresp -V
''}
'';
boot.initrd.preLVMCommands = concatMapStrings openCommand preLVM;