add verifier service

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

flake.nix

@@ -5,7 +5,7 @@
     substituters = [
       "https://cache.nixos.org/?priority=1&want-mass-query=true"
       "https://nix-community.cachix.org/?priority=10&want-mass-query=true"
-      # "https://attic.nayeonie.com/nix-cache"
+      "https://attic.nayeonie.com/nix-cache"
     ];
     trusted-substituters = [
       "https://cache.nixos.org"

modules/update.nix

@@ -16,4 +16,19 @@
     persistent = true;
     flake = "git+ssh://nayeonie.com/ahuston-0/nix-dotfiles.git";
   };
+
+  services.nix-verify = {
+    daily = {
+      enable = true;
+      verify-contents = false;
+      verify-trust = false;
+    };
+    weekly = {
+      enable = true;
+      verify-contents = true;
+      verify-trust = false;
+      frequency = "1week";
+      randomized-delay-sec = "6hour";
+    };
+  };
 }

modules/verify.nix

@@ -0,0 +1,108 @@
+{
+  config,
+  lib,
+  ...
+}:
+
+let
+  cfg = config.services.nix-verify;
+
+  verify-type =
+    with lib.types;
+    attrsOf (
+      submodule (
+        { name, ... }:
+        {
+          options = {
+            enable = lib.mkEnableOption "verify status of nix store";
+
+            service-name = lib.mkOption {
+              type = lib.types.str;
+              description = "the name of the systemd service. ${name} by default";
+              default = name;
+            };
+
+            verify-contents = lib.mkEnableOption "verify contents of nix store";
+
+            verify-trust = lib.mkEnableOption "verify if each path is trusted";
+
+            signatures-needed = lib.mkOption {
+              type = lib.types.int;
+              description = "number of signatures needed when verifying trust. Not needed if verify-trust is disabled or not set.";
+              default = -1;
+            };
+
+            frequency = lib.mkOption {
+              type = lib.types.str;
+              description = "systemd-timer compatible time between pulls";
+              default = "1day";
+            };
+
+            randomized-delay-sec = lib.mkOption {
+              type = lib.types.str;
+              description = "systemd-timer compatible time randomized delay";
+              default = "0";
+            };
+          };
+        }
+      )
+    );
+in
+{
+  options = {
+    services.nix-verify = lib.mkOption {
+      type = verify-type;
+      default = { };
+    };
+  };
+
+  config =
+    let
+      verifiers = lib.filterAttrs (_: { enable, ... }: enable) cfg;
+    in
+    {
+      systemd.services = lib.mapAttrs' (
+        _:
+        {
+          service-name,
+          verify-contents,
+          verify-trust,
+          signatures-needed,
+          ...
+        }:
+        lib.nameValuePair "nix-verifiers@${service-name}" {
+          requires = [ "multi-user.target" ];
+          after = [ "multi-user.target" ];
+          description = "Verify nix store (verify-contents: ${verify-contents}, verify-trust: ${verify-trust}, signatures-needed: ${signatures-needed})";
+          serviceConfig = {
+            Type = "oneshot";
+            User = "root";
+            ExecStart =
+              "${config.nix.package}/bin/nix store verify --all "
+              + lib.optionalString (!verify-contents) "--no-contents "
+              + lib.optionalString (!verify-trust) "--no-trust "
+              + lib.optionalString (signatures-needed >= 0) "--sigs-needed ${signatures-needed}";
+          };
+        }
+      ) verifiers;
+
+      systemd.timers = lib.mapAttrs' (
+        _:
+        {
+          service-name,
+          frequency,
+          randomized-delay-sec,
+          ...
+        }:
+        lib.nameValuePair "nix-verifiers@${service-name}" {
+          wantedBy = [ "timers.target" ];
+          timerConfig = {
+            OnBootSec = frequency;
+            OnUnitActiveSec = frequency;
+            RandomizedDelaySec = randomized-delay-sec;
+            Unit = "nix-verifiers@${service-name}.service";
+          };
+        }
+      ) verifiers;
+    };
+}