nixpkgs/nixos/tests/systemd-confinement.nix

import ./make-test.nix {
  name = "systemd-confinement";

  machine = { pkgs, lib, ... }: let
    testServer = pkgs.writeScript "testserver.sh" ''
      #!${pkgs.stdenv.shell}
      export PATH=${lib.escapeShellArg "${pkgs.coreutils}/bin"}
      ${lib.escapeShellArg pkgs.stdenv.shell} 2>&1
      echo "exit-status:$?"
    '';

    testClient = pkgs.writeScriptBin "chroot-exec" ''
      #!${pkgs.stdenv.shell} -e
      output="$(echo "$@" | nc -NU "/run/test$(< /teststep).sock")"
      ret="$(echo "$output" | sed -nre '$s/^exit-status:([0-9]+)$/\1/p')"
      echo "$output" | head -n -1
      exit "''${ret:-1}"
    '';

    mkTestStep = num: { description, config ? {}, testScript }: {
      systemd.sockets."test${toString num}" = {
        description = "Socket for Test Service ${toString num}";
        wantedBy = [ "sockets.target" ];
        socketConfig.ListenStream = "/run/test${toString num}.sock";
        socketConfig.Accept = true;
      };

      systemd.services."test${toString num}@" = {
        description = "Confined Test Service ${toString num}";
        confinement = (config.confinement or {}) // { enable = true; };
        serviceConfig = (config.serviceConfig or {}) // {
          ExecStart = testServer;
          StandardInput = "socket";
        };
      } // removeAttrs config [ "confinement" "serviceConfig" ];

      __testSteps = lib.mkOrder num ''
        subtest '${lib.escape ["\\" "'"] description}', sub {
          $machine->succeed('echo ${toString num} > /teststep');
          ${testScript}
        };
      '';
    };

  in {
    imports = lib.imap1 mkTestStep [
      { description = "chroot-only confinement";
        config.confinement.mode = "chroot-only";
        testScript = ''
          $machine->succeed(
            'test "$(chroot-exec ls -1 / | paste -sd,)" = bin,nix',
            'test "$(chroot-exec id -u)" = 0',
            'chroot-exec chown 65534 /bin',
          );
        '';
      }
      { description = "full confinement with APIVFS";
        testScript = ''
          $machine->fail(
            'chroot-exec ls -l /etc',
            'chroot-exec ls -l /run',
            'chroot-exec chown 65534 /bin',
          );
          $machine->succeed(
            'test "$(chroot-exec id -u)" = 0',
            'chroot-exec chown 0 /bin',
          );
        '';
      }
      { description = "check existence of bind-mounted /etc";
        config.serviceConfig.BindReadOnlyPaths = [ "/etc" ];
        testScript = ''
          $machine->succeed('test -n "$(chroot-exec cat /etc/passwd)"');
        '';
      }
      { description = "check if User/Group really runs as non-root";
        config.serviceConfig.User = "chroot-testuser";
        config.serviceConfig.Group = "chroot-testgroup";
        testScript = ''
          $machine->succeed('chroot-exec ls -l /dev');
          $machine->succeed('test "$(chroot-exec id -u)" != 0');
          $machine->fail('chroot-exec touch /bin/test');
        '';
      }
      (let
        symlink = pkgs.runCommand "symlink" {
          target = pkgs.writeText "symlink-target" "got me\n";
        } "ln -s \"$target\" \"$out\"";
      in {
        description = "check if symlinks are properly bind-mounted";
        config.confinement.packages = lib.singleton symlink;
        testScript = ''
          $machine->fail('chroot-exec test -e /etc');
          $machine->succeed('chroot-exec cat ${symlink} >&2');
          $machine->succeed('test "$(chroot-exec cat ${symlink})" = "got me"');
        '';
      })
      { description = "check if StateDirectory works";
        config.serviceConfig.User = "chroot-testuser";
        config.serviceConfig.Group = "chroot-testgroup";
        config.serviceConfig.StateDirectory = "testme";
        testScript = ''
          $machine->succeed('chroot-exec touch /tmp/canary');
          $machine->succeed('chroot-exec "echo works > /var/lib/testme/foo"');
          $machine->succeed('test "$(< /var/lib/testme/foo)" = works');
          $machine->succeed('test ! -e /tmp/canary');
        '';
      }
    ];

    options.__testSteps = lib.mkOption {
      type = lib.types.lines;
      description = "All of the test steps combined as a single script.";
    };

    config.environment.systemPackages = lib.singleton testClient;

    config.users.groups.chroot-testgroup = {};
    config.users.users.chroot-testuser = {
      description = "Chroot Test User";
      group = "chroot-testgroup";
    };
  };

  testScript = { nodes, ... }: ''
    $machine->waitForUnit('multi-user.target');
    ${nodes.machine.config.__testSteps}
  '';
}