title: how to login to yahoo website programatically
body: <p>Right off the bat - please do not suggest I use the Yahoo API. I am doing this purely as a learning experience and using the API would defeat the purpose.</p>
  
  <p>I am using Fiddler to look at the HTTP traffic when I log into Yahoo mail (mail.yahoo.com) or Flickr. I see that the browser posts data to <a href="https://login.yahoo.com/config/login" rel="nofollow">https://login.yahoo.com/config/login</a>. Sample post data is:</p>
  
  <blockquote>
    <p>.tries=1&amp;.src=flickrsignin&amp;.md5=&amp;.hash=&amp;.js=&amp;.last=&amp;promo=&amp;.intl=us&amp;.lang=en-US&amp;.bypass=&amp;.partner=&amp;.u=811cdp17imj21&amp;.v=0&amp;.challenge=iwQ4dJLk0KhUP8Xlpyji_8ftQ.fe&amp;.yplus=&amp;.emailCode=&amp;pkg=&amp;stepid=&amp;.ev=&amp;hasMsgr=1&amp;.chkP=Y&amp;.done=https%3A%2F%2Flogin.yahoo.com%2Fconfig%2Fvalidate%3F.src%3Dflickrsignin%26.pc%3D8190%26.scrumb%3D0%26.pd%3Dc%253DJvVF95K62e6PzdPu7MBv2V8-%26.intl%3Dus%26.done%3Dhttp%253A%252F%252Fwww.flickr.com%252Fsignin%252Fyahoo%252F%253Fredir%253D%25252Fphotos%25252Ffriends%25252F&amp;.pd=flickrsignin_ver%3D0%26c%3DJvVF95K62e6PzdPu7MBv2V8-%26ivt%3D%26sg%3D&amp;.ws=1&amp;.cp=0&amp;pad=15&amp;aad=15&amp;popup=1&amp;login=nkisnksd&amp;passwd=noasno&amp;.save=&amp;passwd_raw=</p>
  </blockquote>
  
  <p>As you see, there are lots of values in there, such as the challenge string, which I don't know how the browser comes up with it. How can I figure out the steps the browser is taking to come up with the challenge response? I assume it's an algorithm using the cookies stored when I GET the page, but just not sure how the browser automatically knows the algorithm?</p>
  
  <p>Thanks!</p>