title: Custom STS & Azure ACS error ACS50008: Invalid SAML token
body: <p>I have a custom STS implementation. Currently it is configured as an additional identity provider on Azure ACS. I have a relying party website that is authenticating successfully via ACS (Windows Live, Google, etc). However, whenever I try to login using my custom STS I always get the Error 401. </p>
  
  <ul>
  <li><strong>Error Code ACS20001: An error occurred while processing a WS-Federation sign-in response.</strong></li>
  <li><strong>Error Code ACS50008: SAML token is invalid.</strong></li>
  </ul>
  
  <p>I have searched through the forums but in my case I dont get any more detail on the error and do not know how to proceed and fix this. </p>
  
  <p>My STS is currently on beta and can be reached here: <a href="https://login.xo.gr/FederationMetadata/2007-06/FederationMetadata.xml" rel="nofollow">metadata</a> . </p>
  
  <p>If anyone has any suggestions or wants to give it a try please contact me via email and I will open a demo login on my custom provider.</p>
  
  <p><em><strong>note:</strong> The case is different than similar question found <a href="http://social.msdn.microsoft.com/Forums/en-US/windowsazuresecurity/thread/8fac10c8-b30b-4244-8459-2ec842584e8d" rel="nofollow">here</a> since my inner exception details do not suggest any reason.</em></p>
  
  <p><strong>UPDATE:</strong> check the discussion in this <a href="http://social.msdn.microsoft.com/Forums/en-US/windowsazuresecurity/thread/113f17f6-d918-4019-8475-a7432ed12962/" rel="nofollow">thread</a> for some additional informaton and the payloads I extracted from fiddler.</p>
  
  <p>Thanks in advance,</p>
  
  <p>Constantinos</p>