Friday, August 5, 2016

realurl

The inability of browsers to deal with shortened URLs led to the writing of a quick one-liner for verifying the final destination of a URL.

Add this line to ~/.bashrc :

alias realurl='ruby -r net/http -e "ARGV.map{ |s| while(r=Net::HTTP.get_response(URI(s)) and r.code[0] == \"3\"); s=r[\"location\"];end;puts s}"'

Then use the realurl alias to look up URLs:

bash# realurl http://goo.gl/KjdQYT
https://www.blackhat.com/us-16/briefings.html#weaponizing-data-science-for-social-engineering-automated-e2e-spear-phishing-on-twitter?Wolfesp18

The expanded Ruby code is as follows:

#!/usr/bin/env ruby
# expand a shortened URL by following all redirects
require 'net/http'

def expand_url(str)
  while(hdr=Net::HTTP.get_response(URI(str)) and hdr.code[0] == '3')
    str = hdr['location']
  end
  puts str
end

if __FILE__ == $0
  ARGV.each do |arg|
    puts expand_url arg
  end
end 

Sure, it would be nice to print the page Title attribute as well, but that means loading up Nokogiri and ends up being a bit of overkill.