colin
7c38c1dbe9
note that /etc/machine-id now contains a different value than before, meaning `journalctl` will not show logs from before the time of this change.
95 lines
4.6 KiB
Nix
95 lines
4.6 KiB
Nix
# borrows from:
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# https://xeiaso.net/blog/paranoid-nixos-2021-07-18
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# https://elis.nu/blog/2020/05/nixos-tmpfs-as-root/
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# https://github.com/nix-community/impermanence
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{ lib, config, impermanence, ... }:
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with lib;
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let
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cfg = config.sane.impermanence;
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# taken from sops-nix code: checks if any secrets are needed to create /etc/shadow
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secretsForUsers = (lib.filterAttrs (_: v: v.neededForUsers) config.sops.secrets) != {};
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in
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{
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options = {
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sane.impermanence.enable = mkOption {
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default = false;
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type = types.bool;
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};
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sane.impermanence.home-dirs = mkOption {
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default = [];
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type = types.listOf (types.either types.str (types.attrsOf types.str));
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};
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sane.impermanence.service-dirs = mkOption {
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default = [];
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type = types.listOf (types.either types.str (types.attrsOf types.str));
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};
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};
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config = let
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map-dir = defaults: dir: if isString dir then
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map-dir defaults { directory = "${defaults.directory}${dir}"; }
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else
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defaults // dir
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;
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map-dirs = defaults: dirs: builtins.map (map-dir defaults) dirs;
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map-home-dirs = map-dirs { user = "colin"; group = "users"; mode = "0755"; directory = "/home/colin/"; };
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map-sys-dirs = map-dirs { user = "root"; group = "root"; mode = "0755"; directory = ""; };
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in mkIf cfg.enable {
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sane.image.extraDirectories = [ "/nix/persist/var/log" ];
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environment.persistence."/nix/persist" = {
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directories = (map-home-dirs cfg.home-dirs) ++ (map-sys-dirs [
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# NB: this `0700` here clobbers the perms for /persist/etc, breaking boot on freshly-deployed devices
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# { mode = "0700"; directory = "/etc/NetworkManager/system-connections"; }
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# "/etc/nixos"
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# "/etc/ssh" # persist only the specific files we want, instead
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"/var/log"
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"/var/backup" # for e.g. postgres dumps
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# "/var/lib/AccountsService" # not sure what this is, but it's empty
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"/var/lib/alsa" # preserve output levels, default devices
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# "/var/lib/blueman" # files aren't human readable
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"/var/lib/bluetooth" # preserve bluetooth handshakes
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"/var/lib/colord" # preserve color calibrations (?)
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# "/var/lib/dhclient" # empty on lappy; dunno about desko
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# "/var/lib/fwupd" # not sure why this would need persistent state
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# "/var/lib/geoclue" # empty on lappy
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# "/var/lib/lockdown" # empty on desko; might store secrets after iOS handshake?
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# "/var/lib/logrotate.status" # seems redundant with what's in /var/log?
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"/var/lib/machines" # maybe not needed, but would be painful to add a VM and forget.
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# "/var/lib/misc" # empty on lappy
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# "/var/lib/NetworkManager" # looks to be mostly impermanent state?
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# "/var/lib/NetworkManager-fortisslvpn" # empty on lappy
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# "/var/lib/nixos" # has some uid/gid maps, but we enforce these to be deterministic.
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# "/var/lib/PackageKit" # wtf is this?
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# "/var/lib/power-profiles-daemon" # redundant with nixos declarations
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# "/var/lib/private" # empty on lappy
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# "/var/lib/systemd" # nothing obviously necessary
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# "/var/lib/udisks2" # empty on lappy
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# "/var/lib/upower" # historic charge data. unnecessary, but maybe used somewhere?
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#
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# servo additions:
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] ++ cfg.service-dirs);
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# /etc/machine-id is a globally unique identifier used for:
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# - systemd-networkd: DHCP lease renewal (instead of keying by the MAC address)
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# - systemd-journald: to filter logs by host
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# - chromium (potentially to track re-installations)
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# - gdbus; system services that might upgrade to AF_LOCAL if both services can confirm they're on the same machine
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# of these, systemd-networkd is the only legitimate case to persist the machine-id.
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# depersisting it should be "safe"; edge-cases like systemd-networkd can be directed to use some other ID if necessary.
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# nixos-impermanence shows binding the host ssh priv key to this; i could probably hash the host key into /etc/machine-id if necessary.
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# files = [ "/etc/machine-id" ];
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};
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# secret decoding depends on /etc/ssh keys, which may be persisted
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system.activationScripts.setupSecrets.deps = [ "persist-ssh-host-keys" ];
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system.activationScripts.setupSecretsForUsers = lib.mkIf secretsForUsers {
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deps = [ "persist-ssh-host-keys" ];
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};
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# populated by ssh.nix, which persists /etc/ssh/host_keys
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system.activationScripts.persist-ssh-host-keys.text = lib.mkDefault "";
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};
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}
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