Question

I want to make a simple Sinatra app that when I navigate to “/proxy/:someurl” I will see the exact contents of navigating directly to :someurl, AKA a simple web proxy, sort of like a full-page iframe.

What is the best way to do this?

Answer 1

require 'sinatra'
require 'open-uri'

get '/proxy' do
  url = params[:url]
  raise "GTFO" if (url[0] == '/' || url[0] == '.')
  open(url) do |content|
    content.read.to_s.gsub(/(href|src)=("|')\//, '\1=\2' + url + '/')
  end
end

This script gets a page’s content, thanks to OpenURI, fixes scripts, stylesheets and images links, then displays the result.

I used a /proxy?url=http://url.com/ route instead of a /proxy/url one. Sinatra doesn’t like the slashes and special chars that are usually in URLs.