SSO using Nextcloud

This works well with the plugin for embedding external sites: https://apps.nextcloud.com/apps/external

Take care: this app changes your Nextcloud cookie path to /.

Configure nginx

This assumes nextcloud is installed under url prefix /owncloud/

	# ...
        location @error401 {
                return 302 /owncloud/login;
        }

	# Internal authentication endpoint for users jack, joe and jenny
	location = /poorsso {
		internal;
		# configure owncloud instance on same server and allowed usernames here
                proxy_pass https://www.example.com/owncloud/index.php/apps/poorsso/testlogin/jack,joe,jenny;
		# do not pass request headers to auth endpoint
		proxy_pass_request_headers off;
		# but pass just the 'Cookie' header still
		proxy_set_header Cookie $http_cookie;
		# do not pass request body to auth endpoint
		proxy_pass_request_body off;
        }

	# Other SSO protected app
	location /app {
                auth_request /poorsso;
		error_page 401 = @error401;
                proxy_pass http://192.168.1.100/app;
        }
	# ...