title: Design of Multi-tenant authentication
body: <p>I am starting to design Multi-tenant system and already read the article:<br>
  <a href="http://msdn.microsoft.com/en-us/library/aa479086.aspx" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/aa479086.aspx</a></p>
  
  <p>Any case, I have couple of question related to authentication.
  For example, we need to support a customer that requires Separate Databases.
  More precisely, the customer uses Separate LDAPs (LDAP per tenant).
  The problem I can not solve that the authentication framework need to know a tenant before the authentication to authenticate against the appropriate LDAP.
  How a user selects tenant during the authentication?</p>
  
  <p><em>The form authentication:</em></p>
  
  <p>Should we develop a special form login with 3 input fields: user name, password, and tenant?<br>
  Should we show to a user the list of all tenants? 
  This is information disclosure, a user can see the list of all tenants in the deployment.
  Should it be free text filed? In this case it is error prone.</p>
  
  <p><em>Other types of the authentications:</em></p>
  
  <p>How tenant information can be send if we use Basic Authentication? Digest Authentication? Client Certificate Authentication?</p>
  
  <p>Any point to already existing(free) frameworks will be appreciated. </p>