nixos/nginx: make redirect status code configurable

Add an option to configure which code globalRedirect and forceSSL use.
It previously was always 301 with no easy way to override.

nixos/doc/manual/release-notes/rl-2405.section.md

@@ -47,6 +47,10 @@ The pre-existing [services.ankisyncd](#opt-services.ankisyncd.enable) has been m
   existing process, but will need to start that process from gdb (so it is a
   child). Or you can set `boot.kernel.sysctl."kernel.yama.ptrace_scope"` to 0.
 
+- [Nginx virtual hosts](#opt-services.nginx.virtualHosts) using `forceSSL` or
+  `globalRedirect` can now have redirect codes other than 301 through
+  `redirectCode`.
+
 - Gitea 1.21 upgrade has several breaking changes, including:
   - Custom themes and other assets that were previously stored in `custom/public/*` now belong in `custom/public/assets/*`
   - New instances of Gitea using MySQL now ignore the `[database].CHARSET` config option and always use the `utf8mb4` charset, existing instances should migrate via the `gitea doctor convert` CLI command.

nixos/modules/services/web-servers/nginx/default.nix

@@ -377,7 +377,7 @@ let
             server_name ${vhost.serverName} ${concatStringsSep " " vhost.serverAliases};
             ${acmeLocation}
             location / {
-              return 301 https://$host$request_uri;
+              return ${toString vhost.redirectCode} https://$host$request_uri;
             }
           }
         ''}
@@ -396,7 +396,7 @@ let
           ${optionalString (vhost.root != null) "root ${vhost.root};"}
           ${optionalString (vhost.globalRedirect != null) ''
             location / {
-              return 301 http${optionalString hasSSL "s"}://${vhost.globalRedirect}$request_uri;
+              return ${toString vhost.redirectCode} http${optionalString hasSSL "s"}://${vhost.globalRedirect}$request_uri;
             }
           ''}
           ${optionalString hasSSL ''

nixos/modules/services/web-servers/nginx/vhost-options.nix

@@ -162,10 +162,11 @@ with lib;
       type = types.bool;
       default = false;
       description = lib.mdDoc ''
-        Whether to add a separate nginx server block that permanently redirects (301)
-        all plain HTTP traffic to HTTPS. This will set defaults for
-        `listen` to listen on all interfaces on the respective default
-        ports (80, 443), where the non-SSL listens are used for the redirect vhosts.
+        Whether to add a separate nginx server block that redirects (defaults
+        to 301, configurable with `redirectCode`) all plain HTTP traffic to
+        HTTPS. This will set defaults for `listen` to listen on all interfaces
+        on the respective default ports (80, 443), where the non-SSL listens
+        are used for the redirect vhosts.
       '';
     };
 
@@ -307,8 +308,20 @@ with lib;
       default = null;
       example = "newserver.example.org";
       description = lib.mdDoc ''
-        If set, all requests for this host are redirected permanently to
-        the given hostname.
+        If set, all requests for this host are redirected (defaults to 301,
+        configurable with `redirectCode`) to the given hostname.
+      '';
+    };
+
+    redirectCode = mkOption {
+      type = types.ints.between 300 399;
+      default = 301;
+      example = 308;
+      description = lib.mdDoc ''
+        HTTP status used by `globalRedirect` and `forceSSL`. Possible usecases
+        include temporary (302, 307) redirects, keeping the request method and
+        body (307, 308), or explicitly resetting the method to GET (303).
+        See <https://developer.mozilla.org/en-US/docs/Web/HTTP/Redirections>.
       '';
     };
 

nixos/tests/all-tests.nix

@@ -583,6 +583,7 @@ in {
   nginx-njs = handleTest ./nginx-njs.nix {};
   nginx-proxyprotocol = handleTest ./nginx-proxyprotocol {};
   nginx-pubhtml = handleTest ./nginx-pubhtml.nix {};
+  nginx-redirectcode = handleTest ./nginx-redirectcode.nix {};
   nginx-sso = handleTest ./nginx-sso.nix {};
   nginx-status-page = handleTest ./nginx-status-page.nix {};
   nginx-tmpdir = handleTest ./nginx-tmpdir.nix {};

nixos/tests/nginx-redirectcode.nix

@@ -0,0 +1,25 @@
+import ./make-test-python.nix ({ pkgs, lib, ... }: {
+  name = "nginx-redirectcode";
+  meta.maintainers = with lib.maintainers; [ misterio77 ];
+
+  nodes = {
+    webserver = { pkgs, lib, ... }: {
+      services.nginx = {
+        enable = true;
+        virtualHosts.localhost = {
+          globalRedirect = "example.com/foo";
+          # With 308 (and 307), the method and body are to be kept when following it
+          redirectCode = 308;
+        };
+      };
+    };
+  };
+
+  testScript = ''
+    webserver.wait_for_unit("nginx")
+    webserver.wait_for_open_port(80)
+
+    # Check the status code
+    webserver.succeed("curl -si http://localhost | grep '^HTTP/[0-9.]\+ 308 Permanent Redirect'")
+  '';
+})