SSO SP connection doesn't send unauthenticated users to /c/portal/login

Issue

• Once we setup a SAML SP connection, the SAML adapter doesn't recognize unauthenticated users and redirect them to /c/portal/login

Environment

• DXP 7.4

Resolution

• This is intended behavior with the “Prompt Enabled” flag unchecked (unchecked by default). 
  To change this behavior, please enable “Prompt Enabled” on the SP site by doing the following:
   
  
  1. Go to SP site as the admin user
  2. Go to Configuration > Site Settings > Login
  3. Check the “Prompt Enabled” box.
  
  It’s very important to note the description of this feature:
  

  Set this to true to prompt a guest user to login when attempting to access a protected page resource in the portal. By setting this value to false, the portal will inform all users that a requested resource is not found if they have no entitlements to view the resource. The portal will not prompt for login even if the user is a guest user. This behavior complies with OWASP best practices.

  The last sentence is most important; although you can enable the prompt, you should do so with caution, as it will allow outside users to determine private pages. Basically, if there is a valid private page, the user will be redirected, so malicious users can determine private page names.
  

Additional Information

• SAML Admin