routes.php - Route::get('login', 'SamlController@login');

[VickG]

Shouldn't this route be a post route? Isn't this route where saml will be posting to?

Route::get('login', 'SamlController@login');

[tmountjr]

Actually, the POST goes to whatever you've specified in the SimpleSAMLphp (SSP) configuration. You hit the GET portion of this route to initiate the saml process; control is ultimately handed off to SSP, including the POST response from the outside SP, which only knows about the URL you told it to respond to in your metadata.