Set X-Private header for private derivations

flake.nix

@@ -83,6 +83,10 @@
       rec {
         packages = {
           inherit nix-serve-ng lix-serve-ng;
+          private = pkgs.runCommand "private" { } ''
+            mkdir -p $out/nix-support
+            touch $out/nix-support/private
+          '';
           default = nix-serve-ng;
         };
 

nix-serve-ng.cabal

@@ -48,6 +48,7 @@ executable nix-serve
                     , base32
                     , bytestring
                     , charset
+                    , directory
                     , http-types
                     , managed
                     , megaparsec

src/Main.hs

@@ -6,6 +6,8 @@
 
 module Main where
 
+import Debug.Trace
+
 import Control.Monad.IO.Class (liftIO)
 import Data.ByteString (ByteString)
 import Data.CharSet.ByteSet (ByteSet(..))
@@ -35,6 +37,7 @@ import qualified Network.Wai.Middleware.RequestLogger as RequestLogger
 import qualified Nix
 import qualified Options
 import qualified Options.Applicative                  as Options
+import qualified System.Directory                     as Directory
 import qualified System.Environment                   as Environment
 
 data ApplicationOptions = ApplicationOptions
@@ -250,6 +253,11 @@ makeApplication ApplicationOptions{..} request respond = do
 
                     done response
 
+                let privateFilePath = ByteString.Char8.unpack storePath ++ "/nix-support/private"
+                isPrivate <- liftIO $ Directory.doesPathExist privateFilePath
+
+                traceM $ show (privateFilePath, isPrivate)
+
                 let streamingBody write flush = do
                        result <- Nix.dumpPath hashPart callback
 
@@ -261,7 +269,7 @@ makeApplication ApplicationOptions{..} request respond = do
                             () <- write builder
                             flush
 
-                let headers = [ ("Content-Type", "text/plain") ]
+                let headers = [ ("Content-Type", "text/plain") ] <> [("X-Private", "true") | isPrivate]
 
                 let response =
                         Wai.responseStream Types.status200 headers streamingBody