FTP File Server

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

class MetasploitModule < Msf::Auxiliary
  include Msf::Exploit::Remote::FtpServer
  include Msf::Auxiliary::Report

  def initialize
    super(
      'Name'        => 'FTP File Server',
      'Description'    => %q{
        This module provides a FTP service
      },
      'Author'      => ['hdm'],
      'License'     => MSF_LICENSE,
      'Actions'     =>
        [
          [ 'Service', 'Description' => 'Serve files via FTP' ]
        ],
      'PassiveActions' =>
        [
          'Service'
        ],
      'DefaultAction'  => 'Service'
    )

    register_options(
      [
        OptString.new('FTPROOT',    [ true,  "The FTP root directory to serve files from", '/tmp/ftproot' ]),
        OptString.new('FTPUSER',    [ false, "Configure a specific username that should be allowed access"], fallbacks: ['USERNAME']),
        OptString.new('FTPPASS',    [ false, "Configure a specific password that should be allowed access"], fallbacks: ['PASSWORD']),
      ])
  end

  def run
    exploit()
  end

  def on_client_command_user(c,arg)
    @state[c][:user] = arg
    if(not datastore['FTPUSER'] or (arg == datastore['FTPUSER']))
      c.put "331 User name okay, need password...\r\n"
    else
      c.put "500 User name invalid\r\n"
    end
    return
  end

  def on_client_command_pass(c,arg)
    @state[c][:pass] = arg
    if(not datastore['FTPPASS'] or (arg == datastore['FTPPASS']))
      c.put "230 Login OK\r\n"
      @state[c][:auth] = true
    else
      c.put "500 Password invalid\r\n"
      @state[c][:auth] = false
    end
    return
  end

  def on_client_command_retr(c,arg)
    print_status("#{@state[c][:name]} FTP download request for #{arg}")

    if(not @state[c][:auth])
      c.put "500 Access denied\r\n"
      return
    end

    path = ::File.join(datastore['FTPROOT'], Rex::FileUtils.clean_path(arg))
    if(not ::File.exist?(path))
      c.put "550 File does not exist\r\n"
      return
    end

    conn = establish_data_connection(c)
    if(not conn)
      c.put("425 Can't build data connection\r\n")
      return
    end

    c.put("150 Opening BINARY mode data connection for #{arg}\r\n")
    conn.put(::File.read(path, ::File.size(path), mode: 'rb'))
    c.put("226 Transfer complete.\r\n")
    conn.close
  end

  def on_client_command_list(c,arg)

    if(not @state[c][:auth])
      c.put "500 Access denied\r\n"
      return
    end

    conn = establish_data_connection(c)
    if(not conn)
      c.put("425 Can't build data connection\r\n")
      return
    end

    pwd = ::File.join(datastore['FTPROOT'], @state[c][:cwd])
    buf = ''

    begin
      Dir.new(pwd).entries.each do |ent|
        path = ::File.join(datastore['FTPROOT'], ent)
        if(::File.directory?(path))
          buf << "drwxr-xr-x   2 0      0       512 Jan  1  2000 #{ent}\r\n"
        end
        if(::File.file?(path))
          buf << "-rw-r--r--   1 0      0       #{::File.size(path)} Jan  1  2000 #{ent}\r\n"
        end
      end
    rescue ::Exception
    end

    c.put("150 Opening ASCII mode data connection for /bin/ls\r\n")
    conn.put("total #{buf.length}\r\n" + buf)
    c.put("226 Transfer complete.\r\n")
    conn.close
  end

  def on_client_command_size(c,arg)

    if(not @state[c][:auth])
      c.put "500 Access denied\r\n"
      return
    end

    path = ::File.join(datastore['FTPROOT'], Rex::FileUtils.clean_path(arg))
    if(not ::File.exist?(path))
      c.put "550 File does not exist\r\n"
      return
    end

    c.put("213 #{::File.size(path)}\r\n")
  end


  def on_client_command_cwd(c,arg)

    if(not @state[c][:auth])
      c.put "500 Access denied\r\n"
      return
    end

    upath = ::File.expand_path(datastore['FTPROOT'])
    npath = ::File.expand_path(::File.join(datastore['FTPROOT'], @state[c][:cwd], arg))
    bpath = npath[upath.length, npath.length - upath.length]

    # Check for traversal above the root directory
    if not (npath[0, upath.length] == upath or bpath == '')
      bpath = '/'
    end

    npath = ::File.expand_path(::File.join(datastore['FTPROOT'], bpath))
    if not (::File.exist?(npath) and ::File.directory?(npath))
      c.put "550 Directory does not exist\r\n"
      return
    end

    bpath = '/' if bpath == ''
    @state[c][:cwd] = bpath

    c.put "250 CWD command successful.\r\n"
  end
end