For one of the Drupal site, on integrating Drupal as a service provider using the simplesamlauth will show the error "Error in simplesamlphp_auth. module: no valid unique id attribute set".

Before configuring the simplesaml_auth need to check and verify the simplesamlphp library added and configured properly as a service provider. We have configured the simplesamlphp and on checking the admin interface its showing it's configured properly. Use the url for configuring the simplesamlphp library for making Drupal as a service provider.

url path: https://simplesamlphp.org/docs/1.5/simplesamlphp-sp

On debugging the issue we found that issue is with the configuration with the simplesaml_auth module. 

Use the path to go to the configuration page: admin/config/people/simplesamlphp_auth

There we can find the option "User Info and Syncing". In this two of the fields are mandatory we need to configure this properly.

1. Which attribute from simpleSAMLphp should be used as user's name *

2. Which attribute from simpleSAMLphp should be used as a unique identifier for the user *

3. Which attribute from simpleSAMLphp should be used as user mail address 

The first two are mandatory and the third one depends upon the need, if we want to create a user with name, unique identifier and email use all the three.

Before doing the configuration first to simplesaml page [admin interface of simplesamlphp] and find the response value from the corresponding idp. The response value from each idp will change.

Pass the correct values we gets as the response from the idp inside the simplesaml_auth configuration page to resolve the error.

Hope with the above few stpes you solved the error.

If you have any doubts regarding the above, please feel free to get in touch with us.