setuid.nix

# Verify that Linux builds cannot create setuid or setgid binaries.

{ lib, config, nixpkgs, ... }:

let
  pkgs = config.nodes.machine.nixpkgs.pkgs;

in
{
  name = "setuid";

  nodes.machine =
    { config, lib, pkgs, ... }:
    { virtualisation.writableStore = true;
      nix.settings.substituters = lib.mkForce [ ];
      nix.nixPath = [ "nixpkgs=${lib.cleanSource pkgs.path}" ];
      virtualisation.additionalPaths = [ pkgs.stdenvNoCC pkgs.pkgsi686Linux.stdenvNoCC ];
    };

  testScript = { nodes }: ''
    # fmt: off
    start_all()

    # Copying to /tmp should succeed.
    machine.succeed(r"""
    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" {} "
      mkdir -p $out
      cp ${pkgs.coreutils}/bin/id /tmp/id
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')

    machine.succeed("rm /tmp/id")

    # Creating a setuid binary should fail.
    machine.fail(r"""
    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" {} "
      mkdir -p $out
      cp ${pkgs.coreutils}/bin/id /tmp/id
      chmod 4755 /tmp/id
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')

    machine.succeed("rm /tmp/id")

    # Creating a setgid binary should fail.
    machine.fail(r"""
    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" {} "
      mkdir -p $out
      cp ${pkgs.coreutils}/bin/id /tmp/id
      chmod 2755 /tmp/id
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')

    machine.succeed("rm /tmp/id")

    # The checks should also work on 32-bit binaries.
    machine.fail(r"""
    nix-build --no-sandbox -E '(with import <nixpkgs> { system = "i686-linux"; }; runCommand "foo" {} "
      mkdir -p $out
      cp ${pkgs.coreutils}/bin/id /tmp/id
      chmod 2755 /tmp/id
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')

    machine.succeed("rm /tmp/id")

    # The tests above use fchmodat(). Test chmod() as well.
    machine.succeed(r"""
    nix-build --no-sandbox -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\"
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 666 ]]')

    machine.succeed("rm /tmp/id")

    machine.fail(r"""
    nix-build --no-sandbox -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\"
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')

    machine.succeed("rm /tmp/id")

    # And test fchmod().
    machine.succeed(r"""
    nix-build --no-sandbox -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\"
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 1750 ]]')

    machine.succeed("rm /tmp/id")

    machine.fail(r"""
    nix-build --no-sandbox -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\"
    ")'
    """.strip())

    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')

    machine.succeed("rm /tmp/id")
  '';
}