nixos/acme: Run postRun script as root

nixos/modules/security/acme.nix

@@ -168,7 +168,7 @@ let
     selfsignService = {
       description = "Generate self-signed certificate for ${cert}";
       after = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
-      wants = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
+      requires = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
 
       path = with pkgs; [ minica ];
 
@@ -232,6 +232,15 @@ let
 
         # Only try loading the credentialsFile if the dns challenge is enabled
         EnvironmentFile = mkIf useDns data.credentialsFile;
+
+        # Run as root (Prefixed with +)
+        ExecStartPost = "+" + (pkgs.writeShellScript "acme-postrun" ''
+          cd /var/lib/acme/${escapeShellArg cert}
+          if [ -e renewed ]; then
+            rm renewed
+            ${data.postRun}
+          fi
+        '');
       };
 
       # Working directory will be /tmp
@@ -255,9 +264,8 @@ let
 
         # Copy all certs to the "real" certs directory
         CERT='certificates/${keyName}.crt'
-        CERT_CHANGED=no
         if [ -e "$CERT" ] && ! cmp -s "$CERT" out/fullchain.pem; then
-          CERT_CHANGED=yes
+          touch out/renewed
           echo Installing new certificate
           cp -vp 'certificates/${keyName}.crt' out/fullchain.pem
           cp -vp 'certificates/${keyName}.key' out/key.pem
@@ -265,12 +273,6 @@ let
           ln -sf fullchain.pem out/cert.pem
           cat out/key.pem out/fullchain.pem > out/full.pem
         fi
-
-        if [ "$CERT_CHANGED" = "yes" ]; then
-          cd out
-          set +euo pipefail
-          ${data.postRun}
-        fi
       '';
     };
   };
@@ -344,7 +346,7 @@ let
         example = "cp full.pem backup.pem";
         description = ''
           Commands to run after new certificates go live. Note that
-          these commands run as the acme user and configured group.
+          these commands run as the root user.
 
           Executed in the same directory with the new certificate.
         '';
@@ -648,7 +650,7 @@ in {
       # Create some targets which can be depended on to be "active" after cert renewals
       systemd.targets = mapAttrs' (cert: conf: nameValuePair "acme-finished-${cert}" {
         wantedBy = [ "default.target" ];
-        wants = [ "acme-${cert}.service" "acme-selfsigned-${cert}.service" ];
+        requires = [ "acme-${cert}.service" "acme-selfsigned-${cert}.service" ];
         after = [ "acme-${cert}.service" "acme-selfsigned-${cert}.service" ];
       }) certConfigs;
     })

nixos/tests/acme.nix

@@ -79,8 +79,15 @@ in import ./make-test-python.nix ({ lib, ... }: {
 
       # Cert config changes will not cause the nginx configuration to change.
       # This tests that the reload service is correctly triggered.
+      # It also tests that postRun is exec'd as root
       specialisation.cert-change.configuration = { pkgs, ... }: {
         security.acme.certs."a.example.test".keyType = "ec384";
+        security.acme.certs."a.example.test".postRun = ''
+          set -euo pipefail
+          touch test
+          chown root:root test
+          echo testing > test
+        '';
       };
 
       # Now adding an alias to ensure that the certs are updated
@@ -283,6 +290,7 @@ in import ./make-test-python.nix ({ lib, ... }: {
           switch_to(webserver, "cert-change")
           webserver.wait_for_unit("acme-finished-a.example.test.target")
           check_connection_key_bits(client, "a.example.test", "384")
+          webserver.succeed("grep testing /var/lib/acme/a.example.test/test")
 
       with subtest("Can request certificate with HTTPS-01 when nginx startup is delayed"):
           switch_to(webserver, "slow-startup")