fix: do not allow edits to the bootloader

Reviewed-on: #90

INSTALLATION.md

@@ -102,8 +102,79 @@ nixos-install
 
 ## how to deploy the initial config
 - Don't forget to install the bootloader, if you changed it since `nixos-install`
+- The fresh install has no flakes and no git yet, a temporary shell is enough
+- If the installer iso is older than the flake's nixpkgs, `--no-reexec` keeps
+  `nixos-rebuild` from re-executing a newer version of itself, which can fail
+  against the older systemd of the fresh install (only needed once)
+- Set a password for the user before rebooting, `users.nix` doesn't set one
 ```bash
-$ sudo nixos-rebuild --install-bootloader switch --flake .#host_name
+$ export NIX_CONFIG="experimental-features = nix-command flakes"
+$ nix-shell -p git
+$ sudo nixos-rebuild --install-bootloader boot --flake .#host_name --no-reexec
+$ sudo passwd aaron
+```
+
+## how to enable secure boot
+Secure Boot uses lanzaboote with our own keys, see `modules/nixos/lanzaboote.nix`.
+Do this after the initial config is deployed and boots.
+
+1. create the keys, before the first rebuild with the lanzaboote module
+```bash
+# the keys end up in /var/lib/sbctl, they never leave the host
+$ sudo nix run nixpkgs#sbctl -- create-keys
+```
+
+2. import `modules/nixos/lanzaboote.nix` in the host's `configuration.nix`, rebuild and check the signatures
+```bash
+$ sudo nixos-rebuild switch --flake .#host_name
+# EFI/Linux/*.efi and the bootloader must be signed, kernels in EFI/nixos
+# are not, lanzaboote checks them by hash
+$ sudo sbctl verify
+```
+
+3. reboot once with Secure Boot still disabled, to make sure the new entries boot
+
+4. in the firmware (F2), erase all Secure Boot keys, then boot nixos again
+```bash
+# "Setup Mode: ✗ Enabled", the ✗ only means the state is insecure
+$ sudo sbctl status
+```
+
+5. enroll the keys
+```bash
+# only our own keys, no microsoft keys
+$ sudo sbctl enroll-keys
+```
+- sbctl refuses if the TPM eventlog shows option ROMs (e.g. a dedicated gpu).
+  Don't force it, either trust exactly those with `--tpm-eventlog` or
+  microsoft's keys with `--microsoft`. Without either, the firmware may not
+  start the device, in the worst case the machine doesn't boot at all.
+
+6. enable Secure Boot in the firmware and set a firmware password, then check
+```bash
+$ bootctl status | grep "Secure Boot"   # enabled (user)
+$ sudo sbctl status                     # Secure Boot: ✓ Enabled
+```
+- If it doesn't boot anymore, disabling Secure Boot in the firmware boots as before
+- Losing the keys isn't fatal: erase the keys in the firmware and start over at step 1
+
+## how to unlock the disk with the tpm (laptops)
+Needs Secure Boot first. The TPM releases the key only with the PIN and while
+the Secure Boot state (PCR 7) is unchanged. The passphrase stays as fallback.
+
+1. enroll the TPM with a PIN as an additional key slot
+```bash
+# asks for the current passphrase, then the new PIN
+$ sudo systemd-cryptenroll --tpm2-device=auto --tpm2-pcrs=7 --tpm2-with-pin=yes /dev/disk/by-label/nixcrypt
+```
+
+2. import `modules/nixos/tpm-unlock.nix` in the host's `configuration.nix`, rebuild and reboot
+
+- If the passphrase is suddenly asked for instead of the PIN, the Secure Boot
+  state changed. After a firmware update that's expected, otherwise investigate
+  before typing the passphrase. To re-enroll:
+```bash
+$ sudo systemd-cryptenroll --wipe-slot=tpm2 --tpm2-device=auto --tpm2-pcrs=7 --tpm2-with-pin=yes /dev/disk/by-label/nixcrypt
 ```
 
 ## how to upgrade the system

README.md

@@ -10,7 +10,7 @@ My personal NixOS configurations.
 ├── hosts
 │   ├── argon # desktop
 │   ├── neon # laptop
-│   └── default # test vm
+│   └── krypton # second laptop
 │       ├── configuration.nix # host-specific settings and module imports
 │       ├── hardware-configuration.nix # generated by nixos-generate-config
 │       └── niri.nix # host-specific niri settings (outputs, input)

flake.lock

@@ -1,5 +1,36 @@
 {
   "nodes": {
+    "crane": {
+      "locked": {
+        "lastModified": 1789760033,
+        "narHash": "sha256-jtT4yxZpR8seYnlCMMWSSPlFN92zO6ICuZ8pJrmi86k=",
+        "owner": "ipetkov",
+        "repo": "crane",
+        "rev": "73b980519cefc727a5f6cc8e5c0947a2f9be6edd",
+        "type": "github"
+      },
+      "original": {
+        "owner": "ipetkov",
+        "repo": "crane",
+        "type": "github"
+      }
+    },
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1767039857,
+        "narHash": "sha256-vNpUSpF5Nuw8xvDLj2KCwwksIbjua2LZCqhV1LNRDns=",
+        "owner": "NixOS",
+        "repo": "flake-compat",
+        "rev": "5edf11c44bc78a0d334f6334cdaf7d60d732daab",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "flake-parts": {
       "inputs": {
         "nixpkgs-lib": [
@@ -41,6 +72,30 @@
         "type": "github"
       }
     },
+    "lanzaboote": {
+      "inputs": {
+        "crane": "crane",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "pre-commit": "pre-commit",
+        "rust-overlay": "rust-overlay"
+      },
+      "locked": {
+        "lastModified": 1790423250,
+        "narHash": "sha256-sr4Kfp6yaXUeyKL6n0Y8/ElcR3momIRC20HFc+LF22s=",
+        "owner": "nix-community",
+        "repo": "lanzaboote",
+        "rev": "c1c5edd31802d181c8aa2c71588995d93425d650",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "ref": "v1.2.0",
+        "repo": "lanzaboote",
+        "type": "github"
+      }
+    },
     "nixos-hardware": {
       "inputs": {
         "nixpkgs": [
@@ -119,15 +174,59 @@
         "type": "github"
       }
     },
+    "pre-commit": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nixpkgs": [
+          "lanzaboote",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1789514889,
+        "narHash": "sha256-PFD1nxptCXJyJoiYO1gf/5Vv43yqGpHtMC6LUhl9/pQ=",
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "rev": "59f4ca0d063a1a3ec722c88b51a33004862e5379",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "home-manager": "home-manager",
+        "lanzaboote": "lanzaboote",
         "nixos-hardware": "nixos-hardware",
         "nixpkgs": "nixpkgs",
         "nixvim": "nixvim",
         "noctalia": "noctalia"
       }
     },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "lanzaboote",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1789889921,
+        "narHash": "sha256-aL/ogiN7qZCGeNovS1f9hX73jwYIKb4Pcq6AZm57WtY=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "1fb104a12a8667045559b2575d6d448ae2fbd99b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    },
     "systems": {
       "flake": false,
       "locked": {

flake.nix

@@ -11,6 +11,10 @@
       url = "github:noctalia-dev/noctalia-shell";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    lanzaboote = {
+      url = "github:nix-community/lanzaboote/v1.2.0";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
     nixos-hardware = {
       url = "github:NixOS/nixos-hardware";
       inputs.nixpkgs.follows = "nixpkgs";
@@ -53,7 +57,6 @@
     in
     {
       nixosConfigurations = {
-        default = mkHost "default";
         neon = mkHost "neon";
         argon = mkHost "argon";
         krypton = mkHost "krypton";

hosts/default/configuration.nix

@@ -1,139 +0,0 @@
-# 0x29a nixos config
-
-{ pkgs, ... }:
-
-{
-  # use flakes
-  nix.settings.experimental-features = [
-    "nix-command"
-    "flakes"
-  ];
-
-  # configure bootloader
-  boot.loader.systemd-boot.enable = false;
-  boot.loader.grub = {
-    enable = true;
-    device = "nodev";
-    efiSupport = true;
-  };
-  boot.loader.efi.canTouchEfiVariables = true;
-  boot.kernelParams = [
-    "quiet"
-    "console.ttyS0,115200n8" # allow terminals on serial console
-  ];
-  # plymouth boot eye candy
-  boot.initrd.systemd.enable = true;
-  boot.plymouth.enable = true;
-  boot.plymouth.theme = "spinner";
-  # use latest kernel
-  boot.kernelPackages = pkgs.linuxPackages_latest;
-
-  # guest agent for proxmox
-  services.qemuGuest.enable = true;
-
-  # networking
-  networking.hostName = "nixos";
-  networking.networkmanager.enable = true;
-
-  # time zone.
-  time.timeZone = "Europe/Amsterdam";
-  # select internationalisation properties
-  i18n.defaultLocale = "en_US.UTF-8";
-  i18n.extraLocaleSettings = {
-    LC_ADDRESS = "en_US.UTF-8";
-    LC_IDENTIFICATION = "en_US.UTF-8";
-    LC_MEASUREMENT = "en_US.UTF-8";
-    LC_MONETARY = "en_US.UTF-8";
-    LC_NAME = "en_US.UTF-8";
-    LC_NUMERIC = "en_US.UTF-8";
-    LC_PAPER = "en_US.UTF-8";
-    LC_TELEPHONE = "en_US.UTF-8";
-    LC_TIME = "en_US.UTF-8";
-  };
-  console = {
-    font = "Lat2-Terminus16";
-    keyMap = "de_CH-latin1";
-  };
-
-  # window manager configs
-  services.xserver = {
-    enable = true;
-    xkb.layout = "ch";
-    xkb.options = "eurosign:e,caps:escape";
-
-    windowManager.qtile = {
-      enable = true;
-      extraPackages =
-        python3Packages: with python3Packages; [
-          qtile-extras
-        ];
-    };
-  };
-
-  environment.pathsToLink = [ "/libexec" ];
-  environment.variables.EDITOR = "vim";
-
-  # enable sound
-  services.pipewire = {
-    enable = true;
-    pulse.enable = true;
-  };
-
-  # define a user account
-  users.users.aaron = {
-    isNormalUser = true;
-    group = "users";
-    extraGroups = [ "wheel" ];
-    shell = pkgs.zsh;
-    packages = with pkgs; [
-      tree
-      fastfetch
-    ];
-  };
-
-  # browser
-  programs.firefox.enable = true;
-
-  # zsh config
-  programs.zsh = {
-    enable = true;
-    enableCompletion = true;
-    autosuggestions.enable = true;
-    ohMyZsh = {
-      enable = true;
-      plugins = [
-        "git"
-        "sudo"
-      ];
-      theme = "agnoster";
-    };
-  };
-
-  # system packages
-  environment.systemPackages = with pkgs; [
-    vim
-    neovim
-    git
-    ghostty
-    kitty
-    wget
-    gnupg
-  ];
-
-  # Some programs need SUID wrappers
-  programs.mtr.enable = true;
-  programs.gnupg.agent = {
-    enable = true;
-    enableSSHSupport = true;
-  };
-
-  # enable the OpenSSH daemon
-  services.openssh.enable = true;
-
-  # firewall configs
-  networking.firewall.allowedTCPPorts = [ 22 ];
-  # networking.firewall.allowedUDPPorts = [ ... ];
-
-  # install state version
-  system.stateVersion = "25.05"; # Don't change
-}

hosts/default/hardware-configuration.nix

@@ -1,60 +0,0 @@
-# 0x29a nixos hardware configuration
-
-{
-  config,
-  lib,
-  pkgs,
-  modulesPath,
-  ...
-}:
-
-{
-  imports = [
-    (modulesPath + "/profiles/qemu-guest.nix")
-  ];
-
-  # boot and initrd configs
-  boot.initrd.availableKernelModules = [
-    "uhci_hcd"
-    "ehci_pci"
-    "ahci"
-    "virtio_pci"
-    "virtio_scsi"
-    "sd_mod"
-    "sr_mod"
-  ];
-  boot.initrd.kernelModules = [
-    "dm-snapshot"
-    "cryptd"
-  ];
-  boot.kernelModules = [ ];
-  boot.extraModulePackages = [ ];
-  boot.initrd.luks.devices."cryptroot".device = "/dev/disk/by-label/nixcrypt";
-
-  # file systems
-  fileSystems."/" = {
-    device = "/dev/disk/by-label/nixroot";
-    fsType = "ext4";
-  };
-  fileSystems."/boot" = {
-    device = "/dev/disk/by-label/nixboot";
-    fsType = "vfat";
-    options = [
-      "fmask=0077"
-      "dmask=0077"
-    ];
-  };
-  fileSystems."/home" = {
-    device = "/dev/disk/by-label/nixhome";
-    fsType = "ext4";
-  };
-  swapDevices = [
-    { device = "/dev/disk/by-label/nixswap"; }
-  ];
-
-  # enable dhcp on all interfaces
-  networking.useDHCP = lib.mkDefault true;
-
-  # set host arch
-  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
-}

hosts/default/home.nix

@@ -1,79 +0,0 @@
-{ pkgs, ... }:
-
-{
-  # user config
-  home.username = "aaron";
-  home.homeDirectory = "/home/aaron";
-
-  # packages
-  home.packages = with pkgs; [
-    fastfetch
-    zip
-    xz
-    unzip
-    p7zip
-    jq
-    mtr
-    iperf3
-    dnsutils
-    ldns
-    socat
-    nmap
-    cowsay
-    file
-    which
-    tree
-    zstd
-    gnupg
-    btop
-    iotop
-    iftop
-    strace
-    lsof
-    sysstat
-    lm_sensors
-    ethtool
-    pciutils
-    usbutils
-  ];
-
-  # configure git
-  programs.git.settings = {
-    enable = true;
-    userName = "aaron";
-    userEmail = "aaron@0x29a.ch";
-  };
-
-  programs.zsh = {
-    enable = true;
-    autosuggestion.enable = true;
-    syntaxHighlighting.enable = true;
-    oh-my-zsh = {
-      enable = true;
-      plugins = [
-        "git"
-        "sudo"
-        "python"
-        "ansible"
-      ];
-      theme = "agnoster";
-    };
-  };
-
-  ## deploy qtile config
-  #home.file."qtile-config" = {
-  #  target = ".config/qtile/config.py";
-  #  source = "${inputs.qtile-config}/qtile_config/config.py";
-  #  force = true;
-  #};
-
-  home.sessionVariables = {
-    EDITOR = "vim";
-  };
-
-  # enable home manager
-  programs.home-manager.enable = true;
-
-  # don't change
-  home.stateVersion = "25.05";
-}

hosts/krypton/configuration.nix

@@ -12,6 +12,7 @@
     ../../modules/nixos/certificates.nix
     ../../modules/nixos/docker.nix
     ../../modules/nixos/gnupg.nix
+    ../../modules/nixos/lanzaboote.nix
     ../../modules/nixos/locales.nix
     ../../modules/nixos/networking.nix
     ../../modules/nixos/niri.nix
@@ -23,6 +24,7 @@
     ../../modules/nixos/services.nix
     ../../modules/nixos/settings.nix
     ../../modules/nixos/steam.nix
+    ../../modules/nixos/tpm-unlock.nix
     ../../modules/nixos/users.nix
     ../../modules/nixos/vial.nix
   ];
@@ -30,6 +32,13 @@
   # host-specific niri config (input devices, laptop binds)
   home-manager.users.aaron.imports = [ ./niri.nix ];
 
+  # hidpi panel (2880x1920): the sddm greeter runs in weston, which doesn't scale
+  services.displayManager.sddm.settings.General.GreeterEnvironment = "QT_SCALE_FACTOR=2";
+
+  # bigger boot menu font, mode found with "r" in the menu; mode 6 is beyond
+  # what boot.loader.systemd-boot.consoleMode accepts, so set via lanzaboote
+  boot.lanzaboote.settings.console-mode = "6";
+
   networking.hostName = "krypton";
   system.stateVersion = "26.05"; # don't change
 }

modules/nixos/bootloader.nix

@@ -4,6 +4,8 @@
   # set bootloader to systemd
   boot.loader = {
     systemd-boot.enable = true;
+    # no kernel command line editing at the boot menu (e.g. init=/bin/sh)
+    systemd-boot.editor = false;
     efi.canTouchEfiVariables = true;
   };
 

modules/nixos/lanzaboote.nix

@@ -0,0 +1,25 @@
+# Secure Boot with lanzaboote. systemd-boot stays the bootloader, but lanzaboote
+# installs it signed and writes signed boot entries instead of the nixos module.
+# The keys are created once per host with `sudo sbctl create-keys` before the
+# first rebuild, and enrolled into the firmware with `sbctl enroll-keys`.
+
+{
+  inputs,
+  lib,
+  pkgs,
+  ...
+}:
+
+{
+  imports = [ inputs.lanzaboote.nixosModules.lanzaboote ];
+
+  boot.loader.systemd-boot.enable = lib.mkForce false;
+
+  boot.lanzaboote = {
+    enable = true;
+    pkiBundle = "/var/lib/sbctl";
+  };
+
+  # key management and verification
+  environment.systemPackages = [ pkgs.sbctl ];
+}

modules/nixos/tpm-unlock.nix

@@ -0,0 +1,8 @@
+# Unlock cryptroot with the TPM and a PIN, the passphrase stays as fallback.
+# The TPM only releases the key while PCR 7 (the Secure Boot state) matches,
+# so this needs lanzaboote.nix. Enrolled once per host with
+# `systemd-cryptenroll`, see INSTALLATION.md.
+
+{
+  boot.initrd.luks.devices."cryptroot".crypttabExtraOpts = [ "tpm2-device=auto" ];
+}