From 178ec8974ff70ef0acffa4cc8f47f3234898ff3d Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Sat, 2 Jan 2021 08:55:12 +0000
Subject: [PATCH] nixos/nginx: allow overriding fastcgi params

By default in Nginx, if you want to override a single fastcgi_param,
you have to override all of them.  This is less of a big deal if
you're editing the Nginx configuration directly, but when you're
generating the Nginx configuration with Nix it can be very annoying to
bloat your configuration repeating the default values of FastCGI
parameters every time.

This patch adds a fastcgiParams option to Nginx locations.  If any
parameters are set through this, all the default values will be
included as well, so only the ones that are changing need to be
supplied.  There's no way to use fastcgiParams to actually override
all parameters if that's what you want, but I think that's a niche use
case and it's still possible using extraConfig, which up until now was
the only option

Nginx allows the fastcgi_param directive in http and server scopes as
well as location, but here I only support location.  It would be
possible to support the others, but I don't think it's worth it.  It
would be a possible future enhancement if somebody has a need for it.
---
 .../services/web-servers/nginx/default.nix    | 31 +++++++++++++++++++
 .../web-servers/nginx/location-options.nix    | 10 ++++++
 2 files changed, 41 insertions(+)

diff --git a/nixos/modules/services/web-servers/nginx/default.nix b/nixos/modules/services/web-servers/nginx/default.nix
index 62671e9d7484..7fcd61880ea8 100644
--- a/nixos/modules/services/web-servers/nginx/default.nix
+++ b/nixos/modules/services/web-servers/nginx/default.nix
@@ -27,6 +27,33 @@ let
   ) cfg.virtualHosts;
   enableIPv6 = config.networking.enableIPv6;
 
+  defaultFastcgiParams = {
+    SCRIPT_FILENAME   = "$document_root$fastcgi_script_name";
+    QUERY_STRING      = "$query_string";
+    REQUEST_METHOD    = "$request_method";
+    CONTENT_TYPE      = "$content_type";
+    CONTENT_LENGTH    = "$content_length";
+
+    SCRIPT_NAME       = "$fastcgi_script_name";
+    REQUEST_URI       = "$request_uri";
+    DOCUMENT_URI      = "$document_uri";
+    DOCUMENT_ROOT     = "$document_root";
+    SERVER_PROTOCOL   = "$server_protocol";
+    REQUEST_SCHEME    = "$scheme";
+    HTTPS             = "$https if_not_empty";
+
+    GATEWAY_INTERFACE = "CGI/1.1";
+    SERVER_SOFTWARE   = "nginx/$nginx_version";
+
+    REMOTE_ADDR       = "$remote_addr";
+    REMOTE_PORT       = "$remote_port";
+    SERVER_ADDR       = "$server_addr";
+    SERVER_PORT       = "$server_port";
+    SERVER_NAME       = "$server_name";
+
+    REDIRECT_STATUS   = "200";
+  };
+
   recommendedProxyConfig = pkgs.writeText "nginx-recommended-proxy-headers.conf" ''
     proxy_set_header        Host $host;
     proxy_set_header        X-Real-IP $remote_addr;
@@ -283,6 +310,10 @@ let
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection $connection_upgrade;
       ''}
+      ${concatStringsSep "\n"
+        (mapAttrsToList (n: v: ''fastcgi_param ${n} "${v}";'')
+          (optionalAttrs (config.fastcgiParams != {})
+            (defaultFastcgiParams // config.fastcgiParams)))}
       ${optionalString (config.index != null) "index ${config.index};"}
       ${optionalString (config.tryFiles != null) "try_files ${config.tryFiles};"}
       ${optionalString (config.root != null) "root ${config.root};"}
diff --git a/nixos/modules/services/web-servers/nginx/location-options.nix b/nixos/modules/services/web-servers/nginx/location-options.nix
index f2fc07255725..5a7f5188b6cf 100644
--- a/nixos/modules/services/web-servers/nginx/location-options.nix
+++ b/nixos/modules/services/web-servers/nginx/location-options.nix
@@ -101,6 +101,16 @@ with lib;
       '';
     };
 
+    fastcgiParams = mkOption {
+      type = types.attrsOf types.str;
+      default = {};
+      description = ''
+        FastCGI parameters to override.  Unlike in the Nginx
+        configuration file, overriding only some default parameters
+        won't unset the default values for other parameters.
+      '';
+    };
+
     extraConfig = mkOption {
       type = types.lines;
       default = "";