brew/Library/Homebrew/unpack_strategy/dmg.rb

require "tempfile"

module UnpackStrategy
  class Dmg
    include UnpackStrategy

    def self.can_extract?(path:, magic_number:)
      imageinfo = system_command("/usr/bin/hdiutil",
                                 # realpath is a failsafe against unusual filenames
                                 args: ["imageinfo", path.realpath],
                                 print_stderr: false).stdout

      !imageinfo.empty?
    end

    def extract_to_dir(unpack_dir, basename:, verbose:)
      mount(verbose: verbose) do |mounts|
        begin
          raise "No mounts found in '#{path}'; perhaps it is a bad disk image?" if mounts.empty?
          mounts.each do |mount|
            extract_mount(mount, to: unpack_dir)
          end
        ensure
          mounts.each(&method(:eject))
        end
      end
    end
    private :extract_to_dir

    def mount(verbose: false)
      # realpath is a failsafe against unusual filenames
      realpath = path.realpath
      path = realpath

      Dir.mktmpdir do |unpack_dir|
        without_eula = system_command("/usr/bin/hdiutil",
                                      args: ["attach", "-plist", "-nobrowse", "-readonly", "-noidme", "-mountrandom", unpack_dir, path],
                                      input: "qn\n",
                                      print_stderr: false)

        # If mounting without agreeing to EULA succeeded, there is none.
        plist = if without_eula.success?
          without_eula.plist
        else
          cdr_path = Pathname.new(unpack_dir).join("#{path.basename(".dmg")}.cdr")

          system_command!("/usr/bin/hdiutil", args: ["convert", "-quiet", "-format", "UDTO", "-o", cdr_path, path])

          with_eula = system_command!(
            "/usr/bin/hdiutil",
            args: ["attach", "-plist", "-nobrowse", "-readonly", "-noidme", "-mountrandom", unpack_dir, cdr_path],
          )

          if verbose && !(eula_text = without_eula.stdout).empty?
            ohai "Software License Agreement for '#{path}':"
            puts eula_text
          end

          with_eula.plist
        end

        yield mounts_from_plist(plist)
      end
    end

    def eject(mount)
      # realpath is a failsafe against unusual filenames
      mountpath = Pathname.new(mount).realpath

      begin
        tries ||= 3

        return unless mountpath.exist?

        if tries > 1
          system_command! "/usr/sbin/diskutil",
                          args: ["eject", mountpath],
                          print_stderr: false
        else
          system_command! "/usr/sbin/diskutil",
                          args: ["unmount", "force", mountpath],
                          print_stderr: false
        end
      rescue ErrorDuringExecution => e
        raise e if (tries -= 1).zero?
        sleep 1
        retry
      end
    end

    private

    def extract_mount(mount, to:)
      Tempfile.open(["", ".bom"]) do |bomfile|
        bomfile.close

        Tempfile.open(["", ".list"]) do |filelist|
          filelist.puts(bom_filelist_from_path(mount))
          filelist.close

          system_command! "/usr/bin/mkbom", args: ["-s", "-i", filelist.path, "--", bomfile.path]
          system_command! "/usr/bin/ditto", args: ["--bom", bomfile.path, "--", mount, to]
        end
      end
    end

    def bom_filelist_from_path(mount)
      # We need to use `find` here instead of Ruby in order to properly handle
      # file names containing special characters, such as “e” + “´” vs. “é”.
      system_command("/usr/bin/find", args: [".", "-print0"], chdir: mount, print_stderr: false)
        .stdout
        .split("\0")
        .reject { |path| skip_path?(mount, path) }
        .join("\n")
    end

    def skip_path?(mount, path)
      path = Pathname(path.sub(%r{\A\./}, ""))
      dmg_metadata?(path) || system_dir_symlink?(mount, path)
    end

    # unnecessary DMG metadata
    DMG_METADATA_FILES = Set.new %w[
      .background
      .com.apple.timemachine.donotpresent
      .com.apple.timemachine.supported
      .DocumentRevisions-V100
      .DS_Store
      .fseventsd
      .MobileBackups
      .Spotlight-V100
      .TemporaryItems
      .Trashes
      .VolumeIcon.icns
    ].freeze

    def dmg_metadata?(path)
      relative_root = path.sub(%r{/.*}, "")
      DMG_METADATA_FILES.include?(relative_root.basename.to_s)
    end

    def system_dir_symlink?(mount, path)
      full_path = Pathname(mount).join(path)
      # symlinks to system directories (commonly to /Applications)
      full_path.symlink? && MacOS.system_dir?(full_path.readlink)
    end

    def mounts_from_plist(plist)
      return [] unless plist.respond_to?(:fetch)
      plist.fetch("system-entities", []).map { |e| e["mount-point"] }.compact
    end
  end
end