Metasploit Frameworkのモジュールを練習がてら書いたもの。~/.msf4/modules/auxiliary/scanner/http/simple_http_version.rbあたりに置くと良いと思います

simple_http_version.rb

#!/usr/bin/env ruby
# encoding : utf-8

require 'msf/core'
class Metasploit3 < Msf::Auxiliary
  include Msf::Exploit::Remote::Tcp
  include Msf::Auxiliary::Scanner
  def initialize
    super(
      'Name'           => 'Simple HTTP server detector',
      'Description'    => %q{
        This module detects HTTP server name and version on target host,
        from Server: field's value in response header.
      },
        'Author'         => 'tasuten',
        'License'        => MSF_LICENSE
    )
    register_options(
      [
        Opt::RPORT(80)
      ], self.class)
  end

  def run_host(ip)
    connect()
    # including \r\n, so use ", not '
    sock.puts("GET / HTTP/1.1\r\n")
    sock.puts("Host: #{ip}\r\n") # required in HTTP/1.1
    sock.puts("\r\n")


    server_version = get_server_version(sock)
    if server_version
      print_good("#{server_version} on #{ip}")
    else
      print_error("Can't find server version...")
    end
    disconnect()
  end

  def get_server_version(sock)
    sock.each_line do |line|
      if line =~ /^Server:/i # HTTP headers are case-insensitive
        return line.gsub(/^Server:/i, '').strip
      elsif line.strip == '' # empty line in response header's tail
        return false
      else
        # nop
      end
    end
      return false
  end
end