middleware.py

from django.contrib import auth

from django.core.exceptions import ImproperlyConfigured, PermissionDenied

from timer import Timer

import logging
logger = logging.getLogger(__name__)


class LTIAuthMiddleware(object):
    """
    Middleware for authenticating users via an LTI launch URL.

    If the request is an LTI launch request, then this middleware attempts to
    authenticate the username and signature passed in the POST data.
    If authentication is successful, the user is automatically logged in to
    persist the user in the session.

    If the request is not an LTI launch request, do nothing.
    """

    def process_request(self, request):
        logger.debug('inside process_request %s' % request.path)
        # AuthenticationMiddleware is required so that request.user exists.
        if not hasattr(request, 'user'):
            logger.debug('improperly configured: requeset has no user attr')
            raise ImproperlyConfigured(
                "The Django LTI auth middleware requires the"
                " authentication middleware to be installed.  Edit your"
                " MIDDLEWARE_CLASSES setting to insert"
                " 'django.contrib.auth.middleware.AuthenticationMiddleware'"
                " before the PINAuthMiddleware class.")

        if request.method == 'POST' and request.POST.get('lti_message_type') == 'basic-lti-launch-request':

            logger.debug('received a basic-lti-launch-request - authenticating the user')

            # authenticate and log the user in
            with Timer() as t:
                user = auth.authenticate(request=request)
            logger.debug('authenticate() took %s s' % t.secs)

            if user is not None:
                # User is valid.  Set request.user and persist user in the session
                # by logging the user in.

                logger.debug('user was successfully authenticated; now log them in')
                request.user = user
                with Timer() as t:
                    auth.login(request, user)
    
                logger.debug('login() took %s s' % t.secs)

                lti_launch = {
                    'custom_canvas_account_id': request.POST.get('custom_canvas_account_id', None),
                    'lis_outcome_service_url': request.POST.get('lis_outcome_service_url', None),
                    'lti_message_type': request.POST.get('lti_message_type', None),
                    'resource_link_id': request.POST.get('resource_link_id', None),
                    'user_image': request.POST.get('user_image', None),
                    'lis_outcome_service_url': request.POST.get('lis_outcome_service_url', None),
                    'lis_course_offering_sourcedid': request.POST.get('lis_course_offering_sourcedid', None),
                    'selection_directive': request.POST.get('selection_directive', None),
                    'resource_link_title': request.POST.get('resource_link_title', None),
                    'resource_link_description': request.POST.get('resource_link_description', None),
                    'context_id': request.POST.get('context_id', None),
                    'context_type': request.POST.get('context_type', None),
                    'context_title': request.POST.get('context_title', None),
                    'context_label': request.POST.get('context_label', None),
                    'launch_presentation_locale': request.POST.get('launch_presentation_locale', None),
                    'launch_presentation_css_url': request.POST.get('launch_presentation_css_url', None),
                    'launch_presentation_width': request.POST.get('launch_presentation_width', None),
                    'launch_presentation_height': request.POST.get('launch_presentation_height', None),
                    'launch_presentation_return_url': request.POST.get('launch_presentation_return_url', None),
                    'launch_presentation_document_target': request.POST.get('launch_presentation_document_target', None),
                    'tool_consumer_info_product_family_code': request.POST.get('tool_consumer_info_product_family_code', None),
                    'tool_consumer_info_version': request.POST.get('tool_consumer_info_version', None),
                    'tool_consumer_instance_guid': request.POST.get('tool_consumer_instance_guid', None),
                    'tool_consumer_instance_name': request.POST.get('tool_consumer_instance_name', None),
                    'tool_consumer_instance_description': request.POST.get('tool_consumer_instance_description', None),
                    'tool_consumer_instance_url': request.POST.get('tool_consumer_instance_url', None),
                    'tool_consumer_instance_contact_email': request.POST.get('tool_consumer_instance_contact_email', None),
                    'lis_person_name_given': request.POST.get('lis_person_name_given', None),
                    'lis_person_name_family': request.POST.get('lis_person_name_family', None),
                    'lis_person_contact_email_primary': request.POST.get('lis_person_contact_email_primary', None),
                    'lis_person_name_full': request.POST.get('lis_person_name_full', None),
                    'user_id': request.POST.get('user_id', None),
                    'custom_canvas_user_id': request.POST.get('custom_canvas_user_id', None),
                    'custom_canvas_api_domain': request.POST.get('custom_canvas_api_domain', None),
                    'custom_canvas_enrollment_state': request.POST.get('custom_canvas_enrollment_state', None),
                    'custom_canvas_course_id': request.POST.get('custom_canvas_course_id', None),
                    'custom_canvas_user_login_id': request.POST.get('custom_canvas_user_login_id', None),
                    'roles': request.POST.get('roles', '').split(','),
                }

                request.session['LTI_LAUNCH'] = lti_launch

            else:
                # User could not be authenticated!
                logger.warning('user could not be authenticated via LTI params; let the request continue in case another auth plugin is configured')

    def clean_username(self, username, request):
        """
        Allows the backend to clean the username, if the backend defines a
        clean_username method.
        """
        backend_str = request.session[auth.BACKEND_SESSION_KEY]
        backend = auth.load_backend(backend_str)
        try:
            logger.debug('calling the backend %s clean_username with %s' % (backend, username))
            username = backend.clean_username(username)
            logger.debug('cleaned username is %s' % username)
        except AttributeError:  # Backend has no clean_username method.
            pass
        return username