From b9067e7f1315d7f61c74c1578a1f8398b7e40a94 Mon Sep 17 00:00:00 2001
From: niten <niten@fudo.org>
Date: Sun, 17 Oct 2021 22:10:26 -0700
Subject: [PATCH] Add initial support for encrypted filesystems.

---
 lib/default.nix               |  1 +
 lib/fudo/host-filesystems.nix | 69 +++++++++++++++++++++++++++++++++++
 lib/fudo/secrets.nix          | 15 ++++++++
 lib/types/host.nix            | 59 ++++++++++++++++++++++++++++++
 4 files changed, 144 insertions(+)
 create mode 100644 lib/fudo/host-filesystems.nix

diff --git a/lib/default.nix b/lib/default.nix
index a54d000..7bd9165 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -20,6 +20,7 @@ with lib; {
     ./fudo/global.nix
     ./fudo/grafana.nix
     ./fudo/hosts.nix
+    ./fudo/host-filesystems.nix
     ./fudo/initrd-network.nix
     ./fudo/ipfs.nix
     ./fudo/kdc.nix
diff --git a/lib/fudo/host-filesystems.nix b/lib/fudo/host-filesystems.nix
new file mode 100644
index 0000000..897ec40
--- /dev/null
+++ b/lib/fudo/host-filesystems.nix
@@ -0,0 +1,69 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+let
+  hostname = config.instance.hostname;
+  host-filesystems = config.fudo.hosts.${hostname}.encrypted-filesystems;
+in {
+  config = {
+    fileSystems = mapAttrs' (filesystem-name: opts:
+      nameValuePair opts.target-path
+        {
+          device = "/dev/mapper/${filesystem-name}";
+          fsType = opts.filesystem-type;
+          options = opts.filesystem-options;
+        })
+      host-filesystems;
+
+    systemd = {
+      mounts = let
+        filesystems = mapAttrstoList
+          (fs: opts: { filesystem = fs; opts = opts; })
+          host-filesystems;
+
+        mounts = concatMap
+          (fs: mapAttrsToList
+            (mp: mp-opts:
+              nameValuePair "${fs.filesystem}-${mp}-mount" {
+                what = "/dev/mapper/${fs.filesystem}";
+                type = fs.opts.filesystem-type;
+                where = mp;
+                options = concatStringsSep "," (fs.opts.options ++ mp-opts.options);
+                wantedBy = [ "default.target" ];
+                description = "${fs.opts.filesystem-type} filesystem on ${filesystem} mounted to ${mp}";
+                requires = [ "${fs.filesystem}-decrypt.service" ];
+              })
+            fs.opts.mountpoints)
+          filesystems;
+      in mounts;
+
+      services = mapAttrs' (filesystem-name: opts:
+        nameValuePair "${filesystem-name}-decrypt"
+          {
+            wantedBy = [ "default.target" ];
+            description = "Decrypt the ${filesystem-name} filesystem when the key is available at ${opts.key-path}";
+            path = with pkgs; [ cryptsetup ];
+            serviceConfig = {
+              ExecStart = pkgs.writeShellScript "decrypt-${filesystem-name}.sh" ''
+                cryptsetup open --type luks --key-file ${opts.key-path} ${opts.device} ${filesystem-name}
+              '';
+              ExecStop = pkgs.writeShellScript "close-${filesystem-name}.sh" ''
+                cryptsetup close /dev/mapper/${filesystem-name}
+              '';
+            };
+          })
+        host-filesystems;
+
+      paths = mapAttrs' (filesystem-name: opts:
+        nameValuePair "${filesystem-name}-decrypt"
+          {
+            wantedBy = [ "default.target" ];
+            description = "Watch for decryption key, then decrypt the target filesystem.";
+            pathConfig = {
+              PathExists = opts.key-path;
+              Service = "${filesystem-name}-decrypt.service";
+            };
+          }) host-filesystems;
+    };
+  };
+}
diff --git a/lib/fudo/secrets.nix b/lib/fudo/secrets.nix
index 35c80bb..0ca12a9 100644
--- a/lib/fudo/secrets.nix
+++ b/lib/fudo/secrets.nix
@@ -102,6 +102,21 @@ in {
       default = { };
     };
 
+    host-deep-secrets = mkOption {
+      type = attrsOf (attrsOf (submodule secretOpts));
+      description = ''
+        Secrets that are only passed during deployment.
+
+        These secrets will be passed as nixops deployment secrets,
+        _unlike_ regular secrets that are passed to hosts as part of
+        the nixops store, but encrypted with the host SSH key. Regular
+        secrets are kept secret from normal users. These secrets will
+        be kept secret from _everybody_. However, they won't be
+        available on the host at boot until a new deployment occurs.
+      '';
+      default = { };
+    };
+
     secret-users = mkOption {
       type = listOf str;
       description = "List of users with read-access to secrets.";
diff --git a/lib/types/host.nix b/lib/types/host.nix
index cc3f0cf..f9fd7c7 100644
--- a/lib/types/host.nix
+++ b/lib/types/host.nix
@@ -2,6 +2,55 @@
 
 with lib;
 rec {
+  encryptedFilesystemOpts = { ... }: let
+    mountpoint = { mp, ... }: {
+      options = with types; {
+        mountpoint = mkOption {
+          type = str;
+          description = "Path at which to mount the filesystem.";
+          default = mp;
+        };
+
+        options = mkOption {
+          type = listOf str;
+          description = "List of filesystem options specific to this mountpoint (eg: subvol).";
+        };
+      };
+    };
+  in {
+    options = with types; {
+      device = mkOption {
+        type = str;
+        description = "Path to the encrypted device.";
+      };
+
+      key-path = mkOption {
+        type = str;
+        description = ''
+          Path at which to locate the key file.
+
+          The filesystem will be decrypted and mounted once available.";
+        '';
+      };
+
+      filesystem-type = mkOption {
+        type = str;
+        description = "Filesystem type of the decrypted filesystem.";
+      };
+
+      options = mkOption {
+        type = str;
+        description = "List of filesystem options with which to mount.";
+      };
+
+      mountpoints = mkOption {
+        type = attrsOf (submodule mountpoint);
+        description = "A map of mountpoints for this filesystem to fs options. Multiple to support btrfs.";
+        default = {};
+      };
+    };
+  };
+
   masterKeyOpts = { ... }: {
     options = with types; {
       key-path = mkOption {
@@ -177,6 +226,12 @@ rec {
 
       android-dev = mkEnableOption "Enable ADB on the host.";
 
+      encrypted-filesystems = mkOption {
+        type = attrsOf (submodule encrypteFSOpts);
+        description = "List of encrypted filesystems to mount on the local host when the key is available.";
+        default = { };
+      };
+
       initrd-network = let
         keypair-type = { ... }: {
           options = {
@@ -202,6 +257,10 @@ rec {
               type = (submodule keypair-type);
               description = "SSH host key pair to use for initrd.";
             };
+            interface = mkOption {
+              type = str;
+              description = "Name of interface on which to listen for connections.";
+            };
           };
         };