A quick HTTP proxy server in Ruby.

proxy.rb

#!/usr/bin/env ruby
# A quick and dirty implementation of an HTTP proxy server in Ruby
# because I did not want to install anything.
# 
# Copyright (C) 2009-2014 Torsten Becker <[email protected]>
# 
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

require 'socket'
require 'uri'


class Proxy  
  def run port
    begin
      # Start our server to handle connections (will raise things on errors)
      @socket = TCPServer.new port
      
      # Handle every request in another thread
      loop do
        s = @socket.accept
        Thread.new s, &method(:handle_request)
      end
      
    # CTRL-C
    rescue Interrupt
      puts 'Got Interrupt..'
    # Ensure that we release the socket on errors
    ensure
      if @socket
        @socket.close
        puts 'Socked closed..'
      end
      puts 'Quitting.'
    end
  end
  
  def handle_request to_client
    request_line = to_client.readline
    
    verb    = request_line[/^\w+/]
    url     = request_line[/^\w+\s+(\S+)/, 1]
    version = request_line[/HTTP\/(1\.\d)\s*$/, 1]
    uri     = URI::parse url
    
    # Show what got requested
    puts((" %4s "%verb) + url)
    
    to_server = TCPSocket.new(uri.host, (uri.port.nil? ? 80 : uri.port))
    to_server.write("#{verb} #{uri.path}?#{uri.query} HTTP/#{version}\r\n")
    
    content_len = 0
    
    loop do      
      line = to_client.readline
      
      if line =~ /^Content-Length:\s+(\d+)\s*$/
        content_len = $1.to_i
      end
      
      # Strip proxy headers
      if line =~ /^proxy/i
        next
      elsif line.strip.empty?
        to_server.write("Connection: close\r\n\r\n")
        
        if content_len >= 0
          to_server.write(to_client.read(content_len))
        end
        
        break
      else
        to_server.write(line)
      end
    end
    
    buff = ""
    loop do
      to_server.read(4048, buff)
      to_client.write(buff)
      break if buff.size < 4048
    end
    
    # Close the sockets
    to_client.close
    to_server.close
  end
  
end


# Get parameters and start the server
if ARGV.empty?
  port = 8008
elsif ARGV.size == 1
  port = ARGV[0].to_i
else
  puts 'Usage: proxy.rb [port]'
  exit 1
end

Proxy.new.run port

Would love to see a license as well. :-)

@randomcamel @dg-vrnetze I added MIT license, I hope that works for you guys!

Perfect. Thanks a lot.

Hi, I have a question on Line 82. I tried to comment out this line and found the server stop proxy. Why should we send an Connection: Close line to the server while neglecting the client's origin Connection field? I don't understand it, can you explain?

Newbie in network, not native English speaker :)

i tried to fire it up and put it as my nexus7 proxy but every time i try to load a website in browser it shows a white screen, when i logged all data in console it showed the pages are received but apparently it isn't sent to the machine or send in the wrong way.

it works really well... just one problem, huge for me, cannot use it for ssl content (https)

A http (and https) proxy server comes bundled with Ruby
ruby -r webrick/httpproxy -e 'WEBrick::HTTPProxyServer.new(Port: 8080).start'

API reference:
http://ruby-doc.org/stdlib-2.5.0/libdoc/webrick/rdoc/WEBrick/HTTPProxyServer.html

Hope this helps,

The loop at line 95 should check for a nil return value from #read, otherwise it may not work correctly for chunked responses.

while to_server.read(4048, buff)
  to_client.write(buff)
end

"If length is a positive integer, read tries to read length bytes without any conversion (binary mode). It returns nil if an EOF is encountered before anything can be read."

https://ruby-doc.org/core-2.7.1/IO.html#method-i-read