nixpkgs/nixos/modules/tasks/encrypted-devices.nix

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{ config, lib, ... }:
with lib;
let
fileSystems = config.system.build.fileSystems ++ config.swapDevices;
encDevs = filter (dev: dev.encrypted.enable) fileSystems;
# With scripted initrd, devices with a keyFile have to be opened
# late, after file systems are mounted, because that could be where
# the keyFile is located. With systemd initrd, each individual
# systemd-cryptsetup@ unit has RequiresMountsFor= to delay until all
# the mount units for the key file are done; i.e. no special
# treatment is needed.
lateEncDevs =
if config.boot.initrd.systemd.enable
then { }
else filter (dev: dev.encrypted.keyFile != null) encDevs;
earlyEncDevs =
if config.boot.initrd.systemd.enable
then encDevs
else filter (dev: dev.encrypted.keyFile == null) encDevs;
anyEncrypted =
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foldr (j: v: v || j.encrypted.enable) false encDevs;
encryptedFSOptions = {
options.encrypted = {
enable = mkOption {
default = false;
type = types.bool;
description = "The block device is backed by an encrypted one, adds this device as a initrd luks entry.";
};
blkDev = mkOption {
default = null;
example = "/dev/sda1";
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type = types.nullOr types.str;
description = "Location of the backing encrypted device.";
};
label = mkOption {
default = null;
example = "rootfs";
type = types.nullOr types.str;
description = "Label of the unlocked encrypted device. Set `fileSystems.<name?>.device` to `/dev/mapper/<label>` to mount the unlocked device.";
};
keyFile = mkOption {
default = null;
example = "/mnt-root/root/.swapkey";
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type = types.nullOr types.str;
description = ''
Path to a keyfile used to unlock the backing encrypted
device. When systemd stage 1 is not enabled, at the time
this keyfile is accessed, the `neededForBoot` filesystems
(see `utils.fsNeededForBoot`) will have been mounted under
`/mnt-root`, so the keyfile path should usually start with
"/mnt-root/". When systemd stage 1 is enabled,
`fsNeededForBoot` file systems will be mounted as needed
under `/sysroot`, and the keyfile will not be accessed until
its requisite mounts are done.
'';
};
};
};
in
{
options = {
fileSystems = mkOption {
type = with lib.types; attrsOf (submodule encryptedFSOptions);
};
swapDevices = mkOption {
type = with lib.types; listOf (submodule encryptedFSOptions);
};
};
config = mkIf anyEncrypted {
assertions = concatMap (dev: [
{
assertion = dev.encrypted.label != null;
message = ''
The filesystem for ${dev.mountPoint} has encrypted.enable set to true, but no encrypted.label set
'';
}
{
assertion =
config.boot.initrd.systemd.enable -> (
dev.encrypted.keyFile == null
|| !lib.any (x: lib.hasPrefix x dev.encrypted.keyFile) ["/mnt-root" "$targetRoot"]
);
message = ''
Bad use of '/mnt-root' or '$targetRoot` in 'keyFile'.
When 'boot.initrd.systemd.enable' is enabled, file systems
are mounted at '/sysroot' instead of '/mnt-root'.
'';
}
]) encDevs;
boot.initrd = {
luks = {
devices =
builtins.listToAttrs (map (dev: {
name = dev.encrypted.label;
value = { device = dev.encrypted.blkDev; inherit (dev.encrypted) keyFile; };
}) earlyEncDevs);
forceLuksSupportInInitrd = true;
};
# TODO: systemd stage 1
postMountCommands = lib.mkIf (!config.boot.initrd.systemd.enable)
(concatMapStrings (dev:
"cryptsetup luksOpen --key-file ${dev.encrypted.keyFile} ${dev.encrypted.blkDev} ${dev.encrypted.label};\n"
) lateEncDevs);
};
};
}