nil dereference in `api/v1/authorisations#create` when a named permission doesn't exist

[sengi]

Repro: send a POST request to /api/v1/api-users/14149/authorisations (any valid api-user id will do; this one is valid in integration) with the body {"application_id":44,"permissions":["nonexistent_permission"]} (any valid application_id will do). You'll need a valid token to put in the Authorization: bearer ... header.

Expected behaviour: error response saying that the nonexistent_permission permission doesn't exist on application 44 (or preferably whatever the human-friendly name is for that app).

Observed behaviour: 500 response with an HTML body, and a stack trace in the log.

{
  "exception_class": "NoMethodError",
  "exception_message": "undefined method `id' for nil:NilClass",
  "stacktrace": [
    "app/models/user.rb:148:in `grant_permission'",
    "app/models/user.rb:143:in `block in grant_application_permissions'",
    "app/models/user.rb:141:in `map'",
    "app/models/user.rb:141:in `grant_application_permissions'",
    "app/controllers/api/v1/authorisations_controller.rb:54:in `grant_app_permissions!'",
    "app/controllers/api/v1/authorisations_controller.rb:14:in `block in create'",
    "app/controllers/api/v1/authorisations_controller.rb:12:in `create'",
    "lib/same_site_security/middleware.rb:9:in `call'"
  ]
}

Full stack trace:

NoMethodError
undefined method `id' for nil:NilClass
/app/app/models/user.rb:148:in `grant_permission'
/app/app/models/user.rb:143:in `block in grant_application_permissions'
/app/app/models/user.rb:141:in `map'
/app/app/models/user.rb:141:in `grant_application_permissions'
/app/app/controllers/api/v1/authorisations_controller.rb:54:in `grant_app_permissions!'
/app/app/controllers/api/v1/authorisations_controller.rb:14:in `block in create'
/app/vendor/bundle/ruby/2.7.0/gems/activerecord-6.1.5/lib/active_record/connection_adapters/abstract/database_statements.rb:320:in `block in transaction'
/app/vendor/bundle/ruby/2.7.0/gems/activerecord-6.1.5/lib/active_record/connection_adapters/abstract/transaction.rb:319:in `block in within_new_transaction'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/concurrency/load_interlock_aware_monitor.rb:26:in `block (2 levels) in synchronize'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/concurrency/load_interlock_aware_monitor.rb:25:in `handle_interrupt'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/concurrency/load_interlock_aware_monitor.rb:25:in `block in synchronize'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/concurrency/load_interlock_aware_monitor.rb:21:in `handle_interrupt'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/concurrency/load_interlock_aware_monitor.rb:21:in `synchronize'
/app/vendor/bundle/ruby/2.7.0/gems/activerecord-6.1.5/lib/active_record/connection_adapters/abstract/transaction.rb:317:in `within_new_transaction'
/app/vendor/bundle/ruby/2.7.0/gems/activerecord-6.1.5/lib/active_record/connection_adapters/abstract/database_statements.rb:320:in `transaction'
/app/vendor/bundle/ruby/2.7.0/gems/activerecord-6.1.5/lib/active_record/transactions.rb:209:in `transaction'
/app/app/controllers/api/v1/authorisations_controller.rb:12:in `create'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/abstract_controller/base.rb:228:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_controller/metal/rendering.rb:30:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/abstract_controller/callbacks.rb:42:in `block in process_action'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/callbacks.rb:106:in `run_callbacks'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/abstract_controller/callbacks.rb:41:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_controller/metal/rescue.rb:22:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/logstasher-2.1.5/lib/logstasher/rails_ext/action_controller/metal/instrumentation.rb:40:in `block in process_action'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/notifications.rb:203:in `block in instrument'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/notifications/instrumenter.rb:24:in `instrument'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/notifications.rb:203:in `instrument'
/app/vendor/bundle/ruby/2.7.0/gems/logstasher-2.1.5/lib/logstasher/rails_ext/action_controller/metal/instrumentation.rb:27:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_controller/metal/params_wrapper.rb:249:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/activerecord-6.1.5/lib/active_record/railties/controller_runtime.rb:27:in `process_action'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/abstract_controller/base.rb:165:in `process'
/app/vendor/bundle/ruby/2.7.0/gems/actionview-6.1.5/lib/action_view/rendering.rb:39:in `process'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_controller/metal.rb:190:in `dispatch'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_controller/metal.rb:254:in `dispatch'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/routing/route_set.rb:50:in `dispatch'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/routing/route_set.rb:33:in `serve'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/journey/router.rb:50:in `block in serve'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/journey/router.rb:32:in `each'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/journey/router.rb:32:in `serve'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/routing/route_set.rb:842:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/sentry-rails-4.5.2/lib/sentry/rails/rescued_exception_interceptor.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/gds-api-adapters-79.1.0/lib/gds_api/middleware/govuk_header_sniffer.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/gds-api-adapters-79.1.0/lib/gds_api/middleware/govuk_header_sniffer.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/gds-api-adapters-79.1.0/lib/gds_api/middleware/govuk_header_sniffer.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/gds-api-adapters-79.1.0/lib/gds_api/middleware/govuk_header_sniffer.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/gds-api-adapters-79.1.0/lib/gds_api/middleware/govuk_header_sniffer.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-attack-6.5.0/lib/rack/attack.rb:113:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/warden-1.2.9/lib/warden/manager.rb:36:in `block in call'
/app/vendor/bundle/ruby/2.7.0/gems/warden-1.2.9/lib/warden/manager.rb:34:in `catch'
/app/vendor/bundle/ruby/2.7.0/gems/warden-1.2.9/lib/warden/manager.rb:34:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/tempfile_reaper.rb:15:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/etag.rb:27:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/conditional_get.rb:40:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/head.rb:12:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/http/permissions_policy.rb:22:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/http/content_security_policy.rb:19:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/session/abstract/id.rb:266:in `context'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/session/abstract/id.rb:260:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/cookies.rb:689:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/callbacks.rb:27:in `block in call'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/callbacks.rb:98:in `run_callbacks'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/callbacks.rb:26:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/actionable_exceptions.rb:18:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/debug_exceptions.rb:29:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/show_exceptions.rb:33:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/logstasher-2.1.5/lib/logstasher/rails_ext/rack/logger.rb:16:in `call_app'
/app/vendor/bundle/ruby/2.7.0/gems/railties-6.1.5/lib/rails/rack/logger.rb:26:in `block in call'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/tagged_logging.rb:99:in `block in tagged'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/tagged_logging.rb:37:in `tagged'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/tagged_logging.rb:99:in `tagged'
/app/vendor/bundle/ruby/2.7.0/gems/railties-6.1.5/lib/rails/rack/logger.rb:26:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/remote_ip.rb:81:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/request_store-1.5.1/lib/request_store/middleware.rb:19:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/request_id.rb:26:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/method_override.rb:24:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/runtime.rb:22:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/activesupport-6.1.5/lib/active_support/cache/strategy/local_cache_middleware.rb:29:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/sentry-ruby-core-4.5.2/lib/sentry/rack/capture_exceptions.rb:23:in `block in call'
/app/vendor/bundle/ruby/2.7.0/gems/sentry-ruby-core-4.5.2/lib/sentry/hub.rb:56:in `with_scope'
/app/vendor/bundle/ruby/2.7.0/gems/sentry-ruby-core-4.5.2/lib/sentry-ruby.rb:168:in `with_scope'
/app/vendor/bundle/ruby/2.7.0/gems/sentry-ruby-core-4.5.2/lib/sentry/rack/capture_exceptions.rb:14:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/executor.rb:14:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/rack-2.2.3/lib/rack/sendfile.rb:110:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/actionpack-6.1.5/lib/action_dispatch/middleware/host_authorization.rb:142:in `call'
/app/lib/same_site_security/middleware.rb:9:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/railties-6.1.5/lib/rails/engine.rb:539:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/railties-6.1.5/lib/rails/railtie.rb:207:in `public_send'
/app/vendor/bundle/ruby/2.7.0/gems/railties-6.1.5/lib/rails/railtie.rb:207:in `method_missing'
/app/vendor/bundle/ruby/2.7.0/gems/puma-5.6.2/lib/puma/configuration.rb:252:in `call'
/app/vendor/bundle/ruby/2.7.0/gems/puma-5.6.2/lib/puma/request.rb:77:in `block in handle_request'
/app/vendor/bundle/ruby/2.7.0/gems/puma-5.6.2/lib/puma/thread_pool.rb:340:in `with_force_shutdown'
/app/vendor/bundle/ruby/2.7.0/gems/puma-5.6.2/lib/puma/request.rb:76:in `handle_request'
/app/vendor/bundle/ruby/2.7.0/gems/puma-5.6.2/lib/puma/server.rb:441:in `process_client'
/app/vendor/bundle/ruby/2.7.0/gems/puma-5.6.2/lib/puma/thread_pool.rb:147:in `block in spawn_thread'

[floehopper]

I've just validated that this is still an issue by adding a test like this one, but adding a permission name that's not in this list. I saw exactly the same exception, although the stack trace has changed slightly since this issue was reported - the exception is now raised on this line.