core/pkgs/build-support/build-fhsenv-bubblewrap/default.nix

{ lib, stdenv, callPackage, runCommandLocal, writeShellScript, glibc
, pkgsi686Linux, coreutils, bubblewrap }:

{ runScript ? "bash", extraInstallCommands ? "", meta ? { }, passthru ? { }
, extraPreBwrapCmds ? "", extraBwrapArgs ? [ ], unshareUser ? false
, unshareIpc ? false, unsharePid ? false, unshareNet ? false, unshareUts ? false
, unshareCgroup ? false, privateTmp ? false, dieWithParent ? true, ... }@args:

assert (!args ? pname || !args ? version) -> (args
  ? name); # You must provide name if pname or version (preferred) is missing.

let
  inherit (lib)
    concatLines concatStringsSep escapeShellArgs filter optionalString
    splitString;

  inherit (lib.attrsets) removeAttrs;

  name = args.name or "${args.pname}-${args.version}";
  executableName = args.pname or args.name;
  # we don't know which have been supplied, and want to avoid defaulting missing attrs to null. Passed into runCommandLocal
  nameAttrs =
    lib.filterAttrs (key: value: builtins.elem key [ "name" "pname" "version" ])
    args;

  buildFHSEnv = callPackage ./buildFHSEnv.nix { };

  fhsenv = buildFHSEnv (removeAttrs args [
    "runScript"
    "extraInstallCommands"
    "meta"
    "passthru"
    "extraPreBwrapCmds"
    "extraBwrapArgs"
    "dieWithParent"
    "unshareUser"
    "unshareCgroup"
    "unshareUts"
    "unshareNet"
    "unsharePid"
    "unshareIpc"
    "privateTmp"
  ]);

  etcBindEntries = let
    files = [
      # NixOS Compatibility
      "static"
      "nix" # mainly for nixUnstable users, but also for access to nix/netrc
      # Shells
      "shells"
      "bashrc"
      "zshenv"
      "zshrc"
      "zinputrc"
      "zprofile"
      # Users, Groups, NSS
      "passwd"
      "group"
      "shadow"
      "hosts"
      "resolv.conf"
      "nsswitch.conf"
      # User profiles
      "profiles"
      # Sudo & Su
      "login.defs"
      "sudoers"
      "sudoers.d"
      # Time
      "localtime"
      "zoneinfo"
      # Other Core Stuff
      "machine-id"
      "os-release"
      # PAM
      "pam.d"
      # Fonts
      "fonts"
      # ALSA
      "alsa"
      "asound.conf"
      # SSL
      "ssl/certs"
      "ca-certificates"
      "pki"
    ];
  in map (path: "/etc/${path}") files;

  # Create this on the fly instead of linking from /nix
  # The container might have to modify it and re-run ldconfig if there are
  # issues running some binary with LD_LIBRARY_PATH
  createLdConfCache = ''
    cat > /etc/ld.so.conf <<EOF
    /lib
    /lib/x86_64-linux-gnu
    /lib64
    /usr/lib
    /usr/lib/x86_64-linux-gnu
    /usr/lib64
    /lib/i386-linux-gnu
    /lib32
    /usr/lib/i386-linux-gnu
    /usr/lib32
    /run/opengl-driver/lib
    /run/opengl-driver-32/lib
    EOF
    ldconfig &> /dev/null
  '';
  init = run:
    writeShellScript "${name}-init" ''
      source /etc/profile
      ${createLdConfCache}
      exec ${run} "$@"
    '';

  indentLines = str:
    concatLines
    (map (s: "  " + s) (filter (s: s != "") (splitString "\n" str)));
  bwrapCmd = { initArgs ? "" }:
    ''
      ${extraPreBwrapCmds}
      ignored=(/nix /dev /proc /etc ${optionalString privateTmp "/tmp"})
      ro_mounts=()
      symlinks=()
      etc_ignored=()

      # loop through all entries of root in the fhs environment, except its /etc.
      for i in ${fhsenv}/*; do
        path="/''${i##*/}"
        if [[ $path == '/etc' ]]; then
          :
        elif [[ -L $i ]]; then
          symlinks+=(--symlink "$(${coreutils}/bin/readlink "$i")" "$path")
          ignored+=("$path")
        else
          ro_mounts+=(--ro-bind "$i" "$path")
          ignored+=("$path")
        fi
      done

      # loop through the entries of /etc in the fhs environment.
      if [[ -d ${fhsenv}/etc ]]; then
        for i in ${fhsenv}/etc/*; do
          path="/''${i##*/}"
          # NOTE: we're binding /etc/fonts and /etc/ssl/certs from the host so we
          # don't want to override it with a path from the FHS environment.
          if [[ $path == '/fonts' || $path == '/ssl' ]]; then
            continue
          fi
          if [[ -L $i ]]; then
            symlinks+=(--symlink "$i" "/etc$path")
          else
            ro_mounts+=(--ro-bind "$i" "/etc$path")
          fi
          etc_ignored+=("/etc$path")
        done
      fi

      # propagate /etc from the actual host if nested
      if [[ -e /.host-etc ]]; then
        ro_mounts+=(--ro-bind /.host-etc /.host-etc)
      else
        ro_mounts+=(--ro-bind /etc /.host-etc)
      fi

      # link selected etc entries from the actual root
      for i in ${escapeShellArgs etcBindEntries}; do
        if [[ "''${etc_ignored[@]}" =~ "$i" ]]; then
          continue
        fi
        if [[ -e $i ]]; then
          symlinks+=(--symlink "/.host-etc/''${i#/etc/}" "$i")
        fi
      done

      declare -a auto_mounts
      # loop through all directories in the root
      for dir in /*; do
        # if it is a directory and it is not ignored
        if [[ -d "$dir" ]] && [[ ! "''${ignored[@]}" =~ "$dir" ]]; then
          # add it to the mount list
          auto_mounts+=(--bind "$dir" "$dir")
        fi
      done

      declare -a x11_args
      # Always mount a tmpfs on /tmp/.X11-unix
      # Rationale: https://github.com/flatpak/flatpak/blob/be2de97e862e5ca223da40a895e54e7bf24dbfb9/common/flatpak-run.c#L277
      x11_args+=(--tmpfs /tmp/.X11-unix)

      # Try to guess X socket path. This doesn't cover _everything_, but it covers some things.
      if [[ "$DISPLAY" == :* ]]; then
        display_nr=''${DISPLAY#?}
        local_socket=/tmp/.X11-unix/X$display_nr
        x11_args+=(--ro-bind-try "$local_socket" "$local_socket")
      fi

      ${optionalString privateTmp ''
        # sddm places XAUTHORITY in /tmp
        if [[ "$XAUTHORITY" == /tmp/* ]]; then
          x11_args+=(--ro-bind-try "$XAUTHORITY" "$XAUTHORITY")
        fi

        # dbus-run-session puts the socket in /tmp
        IFS=";" read -ra addrs <<<"$DBUS_SESSION_BUS_ADDRESS"
        for addr in "''${addrs[@]}"; do
          [[ "$addr" == unix:* ]] || continue
          IFS="," read -ra parts <<<"''${addr#unix:}"
          for part in "''${parts[@]}"; do
            printf -v part '%s' "''${part//\\/\\\\}"
            printf -v part '%b' "''${part//%/\\x}"
            [[ "$part" == path=/tmp/* ]] || continue
            x11_args+=(--ro-bind-try "''${part#path=}" "''${part#path=}")
          done
        done
      ''}

      cmd=(
        ${bubblewrap}/bin/bwrap
        --dev-bind /dev /dev
        --proc /proc
        --chdir "$(pwd)"
        ${optionalString unshareUser "--unshare-user"}
        ${optionalString unshareIpc "--unshare-ipc"}
        ${optionalString unsharePid "--unshare-pid"}
        ${optionalString unshareNet "--unshare-net"}
        ${optionalString unshareUts "--unshare-uts"}
        ${optionalString unshareCgroup "--unshare-cgroup"}
        ${optionalString dieWithParent "--die-with-parent"}
        --ro-bind /nix /nix
        ${optionalString privateTmp "--tmpfs /tmp"}
        # Our glibc will look for the cache in its own path in `/nix/store`.
        # As such, we need a cache to exist there, because pressure-vessel
        # depends on the existence of an ld cache. However, adding one
        # globally proved to be a bad idea (see #100655), the solution we
        # settled on being mounting one via bwrap.
        # Also, the cache needs to go to both 32 and 64 bit glibcs, for games
        # of both architectures to work.
        --tmpfs ${glibc}/etc \
        --tmpfs /etc \
        --symlink /etc/ld.so.conf ${glibc}/etc/ld.so.conf \
        --symlink /etc/ld.so.cache ${glibc}/etc/ld.so.cache \
        --ro-bind ${glibc}/etc/rpc ${glibc}/etc/rpc \
        --remount-ro ${glibc}/etc \
    '' + optionalString fhsenv.isMultiBuild (indentLines ''
      --tmpfs ${pkgsi686Linux.glibc}/etc \
      --symlink /etc/ld.so.conf ${pkgsi686Linux.glibc}/etc/ld.so.conf \
      --symlink /etc/ld.so.cache ${pkgsi686Linux.glibc}/etc/ld.so.cache \
      --ro-bind ${pkgsi686Linux.glibc}/etc/rpc ${pkgsi686Linux.glibc}/etc/rpc \
      --remount-ro ${pkgsi686Linux.glibc}/etc \
    '') + ''
        "''${ro_mounts[@]}"
        "''${symlinks[@]}"
        "''${auto_mounts[@]}"
        "''${x11_args[@]}"
        ${concatStringsSep "\n  " extraBwrapArgs}
        ${init runScript} ${initArgs}
      )
      exec "''${cmd[@]}"
    '';

  bin = writeShellScript "${name}-bwrap" (bwrapCmd { initArgs = ''"$@"''; });
in runCommandLocal name (nameAttrs // {
  inherit meta;

  passthru = passthru // {
    env = runCommandLocal "${name}-shell-env" { shellHook = bwrapCmd { }; } ''
      echo >&2 ""
      echo >&2 "*** User chroot 'env' attributes are intended for interactive nix-shell sessions, not for building! ***"
      echo >&2 ""
      exit 1
    '';
    inherit args fhsenv;
  };
}) ''
  mkdir -p $out/bin
  ln -s ${bin} $out/bin/${executableName}

  ${extraInstallCommands}
''