acme: Add csr option

nixos/modules/security/acme/default.nix

@@ -227,12 +227,11 @@ let
     commonOpts = [
       "--accept-tos" # Checking the option is covered by the assertions
       "--path" "."
-      "-d" data.domain
       "--email" data.email
-      "--key-type" data.keyType
     ] ++ protocolOpts
       ++ lib.optionals (acmeServer != null) [ "--server" acmeServer ]
-      ++ lib.concatMap (name: [ "-d" name ]) extraDomains
+      ++ lib.optionals (data.csr != null) [ "--csr" data.csr ]
+      ++ lib.optionals (data.csr == null) [ "--key-type" data.keyType "-d" data.domain ] ++ lib.concatMap (name: [ "-d" name ]) extraDomains
       ++ data.extraLegoFlags;
 
     # Although --must-staple is common to both modes, it is not declared as a
@@ -258,6 +257,8 @@ let
             (builtins.map
             (certAttrs: certAttrs.webroot)
             (lib.attrValues config.security.acme.certs)));
+
+    certificateKey = if data.csrKey != null then "${data.csrKey}" else "certificates/${keyName}.key";
   in {
     inherit accountHash cert selfsignedDeps;
 
@@ -440,7 +441,7 @@ let
         # Check if we can renew.
         # We can only renew if the list of domains has not changed.
         # We also need an account key. Avoids #190493
-        if cmp -s domainhash.txt certificates/domainhash.txt && [ -e 'certificates/${keyName}.key' ] && [ -e 'certificates/${keyName}.crt' ] && [ -n "$(find accounts -name '${data.email}.key')" ]; then
+        if cmp -s domainhash.txt certificates/domainhash.txt && [ -e ${certificateKey} ] && [ -e 'certificates/${keyName}.crt' ] && [ -n "$(find accounts -name '${data.email}.key')" ]; then
 
           # Even if a cert is not expired, it may be revoked by the CA.
           # Try to renew, and silently fail if the cert is not expired.
@@ -475,7 +476,7 @@ let
           touch out/renewed
           echo Installing new certificate
           cp -vp 'certificates/${keyName}.crt' out/fullchain.pem
-          cp -vp 'certificates/${keyName}.key' out/key.pem
+          cp -vp ${certificateKey} out/key.pem
           cp -vp 'certificates/${keyName}.issuer.crt' out/chain.pem
           ln -sf fullchain.pem out/cert.pem
           cat out/key.pem out/fullchain.pem > out/full.pem
@@ -732,6 +733,18 @@ let
         description = "Domain to fetch certificate for (defaults to the entry name).";
       };
 
+      csr = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        description = "Path to a Certificate Signing Request to use for fetching the certificate.";
+      };
+
+      csrKey = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        description = "Path to a the Key of the matching Certificate Signing Request.";
+      };
+
       extraDomainNames = lib.mkOption {
         type = lib.types.listOf lib.types.str;
         default = [];
@@ -963,6 +976,12 @@ in {
             used for variables suffixed by "_FILE".
           '';
         }
+        {
+          assertion = lib.all (certOpts: (certOpts.csr == null && certOpts.csrKey == null) || (certOpts.csr != null && certOpts.csrKey != null) ) certs;
+          message = ''
+            Either both `security.acme.certs.${cert}.csr` and `security.acme.certs.${cert}.csrKey` need to be specified, or none.
+          '';
+        }
       ]) cfg.certs));
 
       users.users.acme = {