Add test for setuid seccomp filter

release.nix

@@ -219,6 +219,11 @@ let
       nix = build.x86_64-linux; system = "x86_64-linux";
     });
 
+    tests.setuid = pkgs.lib.genAttrs (pkgs.lib.filter (pkgs.lib.hasSuffix "-linux") systems) (system:
+      import ./tests/setuid.nix rec {
+        nix = build.${system}; inherit system;
+      });
+
     tests.binaryTarball =
       with import <nixpkgs> { system = "x86_64-linux"; };
       vmTools.runInLinuxImage (runCommand "nix-binary-tarball-test"

tests/setuid.nix

@@ -0,0 +1,108 @@
+# Verify that Linux builds cannot create setuid or setgid binaries.
+
+{ system, nix }:
+
+with import <nixpkgs/nixos/lib/testing.nix> { inherit system; };
+
+makeTest {
+
+  machine =
+    { config, lib, pkgs, ... }:
+    { virtualisation.writableStore = true;
+      nix.package = nix;
+      nix.binaryCaches = [ ];
+      nix.nixPath = [ "nixpkgs=${lib.cleanSource pkgs.path}" ];
+      virtualisation.pathsInNixDB = [ pkgs.stdenv pkgs.pkgsi686Linux.stdenv ];
+    };
+
+  testScript = { nodes }:
+    ''
+      startAll;
+
+      # Copying to /tmp should succeed.
+      $machine->succeed('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" {} "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      # Creating a setuid binary should fail.
+      $machine->fail('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" {} "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        chmod 4755 /tmp/id
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      # Creating a setgid binary should fail.
+      $machine->fail('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" {} "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        chmod 2755 /tmp/id
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      # The checks should also work on 32-bit binaries.
+      $machine->fail('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> { system = "i686-linux"; }; runCommand "foo" {} "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        chmod 2755 /tmp/id
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      # The tests above use fchmodat(). Test chmod() as well.
+      $machine->succeed('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        perl -e \"chmod 0666, qw(/tmp/id) or die\"
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 666 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      $machine->fail('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        perl -e \"chmod 04755, qw(/tmp/id) or die\"
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      # And test fchmod().
+      $machine->succeed('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        perl -e \"my \\\$x; open \\\$x, qw(/tmp/id); chmod 01750, \\\$x or die\"
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 1750 ]]');
+
+      $machine->succeed("rm /tmp/id");
+
+      $machine->fail('nix-build --option build-use-sandbox false -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+        mkdir -p $out
+        cp ${pkgs.coreutils}/bin/id /tmp/id
+        perl -e \"my \\\$x; open \\\$x, qw(/tmp/id); chmod 04777, \\\$x or die\"
+      ")\' ');
+
+      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+
+      $machine->succeed("rm /tmp/id");
+    '';
+
+}