diff --git a/modules/features/mtls.nix b/modules/features/mtls.nix
index 7eb2437..054cabc 100644
--- a/modules/features/mtls.nix
+++ b/modules/features/mtls.nix
@@ -66,9 +66,9 @@ let
         default = "root";
       };
       group = lib.mkOption {
-        description = "Group to run the mTLS renewal service as. Defaults to the configured renewal user when null.";
+        description = "Group to run the mTLS renewal service as. Defaults to the configured renewal user.";
         type = lib.types.nullOr lib.types.str;
-        default = null;
+        default = cfg.user;
       };
       reloadUnits = lib.mkOption {
         description = "systemd units to try-reload-or-restart after a successful certificate renewal.";
@@ -92,8 +92,14 @@ let
     keyFile,
     bundleFile,
     lifetime,
+    user,
+    group,
   }:
   let
+    catCmd = lib.getExe' pkgs.coreutils "cat";
+    echoCmd = lib.getExe' pkgs.coreutils "echo";
+    chownCmd = lib.getExe' pkgs.coreutils "chown";
+    chmodCmd = lib.getExe' pkgs.coreutils "chmod";
     stepCmd = lib.getExe pkgs.step-cli;
     sanArgs = lib.concatMapStringsSep " " (s: "--san \"${s}\"") san;
   in
@@ -105,7 +111,9 @@ let
         --provisioner ${provisioner} \
         ${sanArgs} \
         "$@"
-      cat ${certFile} ${keyFile} > ${bundleFile}
+      (umask 077; ${catCmd} ${certFile} ${keyFile} > ${bundleFile})
+      ${chownCmd} ${user}:${group} ${certFile} ${keyFile} ${bundleFile}
+      ${chmodCmd} 640 ${certFile} ${keyFile} ${bundleFile}
     '';
   
   mkMtlsCheckScript = { pkgs, bundleFile }: pkgs.writeShellScriptBin "mtls-check" ''
@@ -120,12 +128,17 @@ let
     certFile,
     keyFile,
     bundleFile,
+    user,
+    group,
     reloadUnits ? [ ],
     postCommands ? [ ],
     systemctlArgs ? [ ],
   }:
   let
+    catCmd = lib.getExe' pkgs.coreutils "cat";
     echoCmd = lib.getExe' pkgs.coreutils "echo";
+    chownCmd = lib.getExe' pkgs.coreutils "chown";
+    chmodCmd = lib.getExe' pkgs.coreutils "chmod";
     systemctl = lib.getExe' pkgs.systemd "systemctl";
     escapedArgs = lib.escapeShellArgs systemctlArgs;
     systemctlCommand = "${systemctl} ${escapedArgs}";
@@ -147,9 +160,9 @@ let
       fi
 
       ${lib.getExe pkgs.step-cli} ca renew --force "${certFile}" "${keyFile}"
-
-      umask 077
-      ${lib.getExe' pkgs.coreutils "cat"} "${certFile}" "${keyFile}" > "${bundleFile}"
+      (umask 077; ${catCmd} "${certFile}" "${keyFile}" > "${bundleFile}")
+      ${chownCmd} ${user}:${group} ${certFile} ${keyFile} ${bundleFile}
+      ${chmodCmd} 640 ${certFile} ${keyFile} ${bundleFile}
 
       ${echoCmd} "Reloading units:"
       ${renewReloadScript}
@@ -171,7 +184,7 @@ let
   let
     serviceGroup = if group == null then user else group;
     renewScript = mkMtlsRenewScript {
-      inherit pkgs certFile keyFile bundleFile reloadUnits postCommands;
+      inherit pkgs certFile keyFile bundleFile reloadUnits postCommands user group;
     };
   in
   {
@@ -271,13 +284,18 @@ in
           (mkMtlsGenerateScript {
             inherit pkgs;
             inherit (cfg) subject provisioner san certFile keyFile bundleFile lifetime;
+            inherit (cfg.renew) user group;
           })
           (mkMtlsCheckScript { inherit pkgs; inherit (cfg) bundleFile; })
-          (mkMtlsRenewScript { inherit pkgs; inherit (cfg) certFile keyFile bundleFile; })
+          (mkMtlsRenewScript {
+            inherit pkgs;
+            inherit (cfg) certFile keyFile bundleFile;
+            inherit (cfg.renew) user group;
+          })
         ];
 
         systemd.tmpfiles.rules = [
-          "d ${cfg.certDir} 0750 ${cfg.renew.user} ${if cfg.renew.group == null then cfg.renew.user else cfg.renew.group} -"
+          "d ${cfg.certDir} 0750 ${cfg.renew.user} ${cfg.renew.group} -"
         ];
 
         systemd.services.mtls-renew = lib.mkIf cfg.renew.enable (mkNixosMtlsRenewService {
@@ -314,10 +332,11 @@ in
           # step-cli
           (mkMtlsGenerateScript {
             inherit (cfg) subject provisioner san lifetime;
+            inherit (cfg.renew) user group;
             inherit pkgs certFile keyFile bundleFile;
           })
           (mkMtlsCheckScript { inherit pkgs bundleFile; })
-          (mkMtlsRenewScript { inherit pkgs certFile keyFile bundleFile; })
+          (mkMtlsRenewScript { inherit pkgs certFile keyFile bundleFile; inherit (cfg.renew) user group; })
         ];
 
         systemd.user.tmpfiles.rules = lib.mkIf cfg.enable [