home/modules/darwin/security/pam-reattach.nix

{ config
, lib
, pkgs
, ...
}:
with lib; let
  cfg = config.security.pam;

  mkPamReattachScript = isEnabled:
    let
      file = "/etc/pam.d/sudo";
      option = "security.pam.reattach";
      sed = "${pkgs.gnused}/bin/sed";
    in
    ''
      ${
        if isEnabled
        then ''
          # If enable and in file, remove and re-add in case the store path has
          # changed
          if grep '${option}' ${file} > /dev/null; then
            ${sed} -i '/${option}/d' ${file}
          fi

          ${sed} -i '2i\
          auth       optional       ${pkgs.pam-reattach}/lib/pam/pam_reattach.so ignore_ssh # nix-darwin: ${option}
          ' ${file}
        ''
        else ''
          # Disable pam_reattach, if added by nix-darwin
          if grep '${option}' ${file} > /dev/null; then
            ${sed} -i '/${option}/d' ${file}
          fi
        ''
      }
    '';
in
{
  options = {
    security.pam.enablePamReattach =
      mkEnableOption ""
      // {
        description = lib.mdDoc ''
          Enable pam_reattach sudo authentication with Touch ID in tmux/screen.

          When enabled, this option adds the following line to
          {file}`/etc/pam.d/sudo`:

          ```
          auth       optional     pam_reattach.so ignore_ssh
          ```

          ::: {.note}
          macOS resets this file when doing a system update. As such,
          pam_reattach won't work after a system update
          until the nix-darwin configuration is reapplied.
          :::
        '';
      };
  };

  config = {
    environment.systemPackages = mkIf cfg.enablePamReattach [ pkgs.pam-reattach ];

    system.activationScripts.pam.text = ''
      # PAM settings
      echo >&2 "setting up pam..."
      ${mkPamReattachScript cfg.enablePamReattach}
    '';
  };
}