Implemeting Permissions for Speakers API in Open Event API Server

In my previous blogpost I talked about what the permissions enlisted in developer handbook means and which part of the codebase defines what part of the permissions clauses. The permission manager provides the permissions framework to implement the permissions and proper access controls based on the dev handbook.

In this blogpost, the actual implementation of the permissions is described. (Speakers API is under consideration here). The following table is the permissions in the developer handbook.

List

View

Create

Update

Delete

Superadmin/admin

Event organizer

✓ [1]

✓ [1]

✓ [1]

✓ [1]

✓ [1]

Registered User

✓ [3]

✓ [3]

✓ [4]

✓ [3]

✓ [3]

Everyone else

✓ [2][4]

✓ [2][4]

  1. Only self-owned events
  2. Only of sessions with state approved or accepted
  3. Only of self-submitted sessions
  4. Only to events with state published.

Super admin and admin should be able to access all the methods – list, view, create, update and delete. All the permissions are implemented through functions derived from permissions manager.Since all the functions have first check for super admin and admin, these are automatically taken care of.

Only of self-submitted sessions
This means that a registered user can list, view, edit or delete speakers of a session which he himself submitted. This requires adding a ‘creator’ attribute to session object which will help us determine if the session was created by the user. So before making a post for sessions, the current user identity is included as part of the payload.

def before_post(self, args, kwargs, data):
   data['creator_id'] = current_identity.id


Now that we have added creator id to a session, a method is used to check if session was created by the same user.

def is_session_self_submitted(view, view_args, view_kwargs, *args, **kwargs):
    user = current_identity


Firstly the current identity is set as user which will later be used to check id. Sequentially, admin, superadmin, organizer and co-organizers are checked. After this a session is fetched using 
kwargs[session_id]. Then if the current user id is same as the creator id of the session fetched, access is granted, else Forbidden Error is returned.

if session.creator_id == user.id:
   return view(*view_args, **view_kwargs)


In the before_post method of speakers class, the session ids received in the data are passed to this function in 
kwargs as session_id. The permissions are then checked there using current user. If the session id are not those of self submitted sessions, ‘Session Not Found’ is returned.

 if not has_access('is_session_self_submitted', session_id=session_id):
                    raise ObjectNotFound({'parameter': 'session_id'},
                                         "Session: {} not found".format(session_id))


Only of sessions with state approved or accepted
This check is required for user who has not submitted the session himself, so he can only see speaker profiles of accepted sessions. First, if the user is not authenticated, permissions are not checked. If co-organizer access is available, then the user can see all the speakers, so for this case filtering is not done. If not, then ‘is_session_self_submitted’ is checked. If yes, then then again no filtering, but if not then the following query filters accepted sessions.

if not has_access('is_session_self_submitted', session_id=session.id):
    query_ = query_.filter(Session.state == "approved" or Session.state == "accepted")

Similarly all the permissions first generate a list of all objects and then filtering is done based on the access level, instead of getting the list based on permissions.

Only to events with state published
It is necessary that users except the organizers and co-organizers can not see the events which are in draft state. The same thing follows for speaker profiles – a user cannot submit or view a speaker profile to an unpublished event. Hence, this constraint. So before POST of speakers, if event is not published, an event not found error is returned.

if event.state == "draft":
    raise ObjectNotFound({'parameter': 'event_id'},
                        "Event: {} not found".format(data['event_id'])


For GET, the  implementation of this is similar to the previous permission. A basic query is generated as such:

query_ = query_.join(Event).filter(Event.id == event.id)


Now if the user does not have at least 
co-organizer access, draft events must be filtered out.

if not has_access('is_coorganizer', event_id=event.id):
    query_ = query_.filter(Event.state == "published")


Some of the finer details have been skipped here, which can be found in the 
code.

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Understanding Permissions for Various APIs in Open Event API Server

Since the Open Event Server has various elements, a proper permissions system is essential. This huge list of permissions is well compiled in the developer handbook which can be found here. In this blogpost, permissions listed in the developer handbook are discussed. Let’s start with what we wish to achieve, that is, how to make sense of these permissions and where does each clause fit in the API Server’s codebase.

For example, Sponsors API has the following permissions.

List

View

Create

Update

Delete

Superadmin/admin

Event organizer

✓ [1]

✓ [1]

✓ [1]

✓ [1]

✓ [1]

Registered User

✓ [3]

✓ [3]

✓ [4]

✓ [3]

✓ [3]

Everyone else

✓ [2][4]

✓ [2][4]

  1. Only self-owned events
  2. Only sessions with state approved or accepted
  3. Only self-submitted sessions
  4. Only to events with state published.

Based on flask-rest-jsonapi resource manager, we get list create under ResourceList through ResourceList’s GET and POST methods, whereas View, Update, Delete work on single objects and hence are provided by ResourceDetail’s GET, PATCH and DELETE respectively. Each function of the permission manager has a jwt_required decorator.

@jwt_required
def is_super_admin(view, view_args, view_kwargs, *args, **kwargs):

@jwt_required
def is_session_self_submitted(view, view_args, view_kwargs, *args, **kwargs):


This
 ensures that whenever a check for access control is made to the permission manager, the user is signed in to Open Event. Additionally, the permissions are written in a hierarchical way such that for every permission, first the useris checked for admin or super admin, then for other accesses. Similar hierarchy is kept for organizer accesses like track organizer, registrar, staff or organizer and coorganizer.

Some APIs resources require no authentication for List. To do this we need to add a check for Authentication token in the headers. Since each of the functions of permission manager have jwt_required as decorator, it is important to checkfor the presence of JWT token in request headers, because we can proceed to check for specific permissions in that case only.

if 'Authorizationin request.headers:
 _jwt_required(current_app.config['JWT_DEFAULT_REALM'])


Since the resources are created by endpoints of the form : 
‘/v1/<resource>/` , this is derived from the separate ResourceListPost class. This class is POST only and has a before_create object method where the required relationships and permissions are checked before inserting the data in the tables. In the before_create method, let’s say that event is a required relationship, which will be defined by the ResourceRelationRequired , then we use our custom method

def require_relationship(resource_list, data):
    for resource in resource_list:
        if resource not in data:
            raise UnprocessableEntity({'pointer': '/data/relationships/{}'.format(resource)},
                                      "A valid relationship with {} resource is required".format(resource))


to check if the required relationships are present in the data. The event_id here can also be used to check for organizer or co-organizer access in the permissions manager for a particular event.

Here’s another permissions structure for a different API – Settings.

List

View

Create

Update

Delete

Superadmin/admin

Everyone else

✓ [1]

  1. Only app_nametaglineanalytics_keystripe_publishable_keygoogle_urlgithub_urltwitter_urlsupport_urlfacebook_urlyoutube_urlandroid_app_urlweb_app_url fields .

This API does not allow access to the complete object, but to only some fields which are listed above. The complete details can be checked here.

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