added ssh host cert renewal

modules/programs/step-client.nix

@@ -65,6 +65,52 @@ in
         '')
         (writeShellScriptBin "ssh-host-cert-check" "${lib.getExe' pkgs.openssh "ssh-keygen"} -Lf ${sshCertPath}")
       ];
+
+      systemd.services.step-ssh-host-renew = {
+        description = "Renew Step SSH host certificate if needed";
+        wantedBy = [ ];
+        after = [ "network-online.target" ];
+        wants = [ "network-online.target" ];
+        path = [ pkgs.step-cli pkgs.openssh pkgs.coreutils pkgs.systemd ];
+        serviceConfig = {
+          Type = "oneshot";
+          User = "root";
+          Group = "root";
+        };
+        script = ''
+          set -euo pipefail
+          if ${stepBin} ssh needs-renewal "${sshCertPath}" --expires-in "4h"; then
+            echo "Renewing SSH host certificate"
+          else
+            rc=$?
+            if [ "$rc" -eq 1 ]; then
+              echo "SSH host cert does not need renewal"
+              exit 0
+            fi
+
+            if [ "$rc" -eq 2 ]; then
+              echo "SSH host cert missing: ${sshCertPath}" >&2
+              exit 1
+            fi
+
+            echo "step ssh needs-renewal failed with rc=$rc" >&2
+            exit "$rc"
+          fi
+        '';
+      };
+
+      systemd.timers.step-ssh-host-renew = {
+        description = "Periodic Step SSH host certificate renewal";
+        wantedBy = [ "timers.target" ];
+
+        timerConfig = {
+          OnBootSec = "5m";
+          OnUnitActiveSec = "4h";
+          RandomizedDelaySec = "15m";
+          Persistent = true;
+          Unit = "step-ssh-host-renew.service";
+        };
+      };
     };
   };