Boundaries & Access Control #
Boundaries is Bonfire's flexible framework for full per-user/per-object/per-action access control. It makes it easy to ensure that users may only see or do what they are supposed to.
Users and Circles #
Ignoring any future bot support, boundaries ultimately apply to users.
Circles are a way of categorising users. Each user has their own set of circles that they can add to and categorise other users in as they please.
Circles allow a user to categorise work colleagues differently from friends, for example. They can choose to allow different interactions from users in the two circles or limit which content each sees on a per-item basis.
Verbs #
Verbs represent actions that the user could perform, such as reading a post or replying to a message.
Each verb has a unique ID, like the table IDs from pointers
, which must be known to the system through configuration.
Permissions #
Permissions can take one of three values:
true
false
nil
(or null
to postgresql).
true
and false
are easy enough to understand as yes and no, but what is nil
?
nil
represents no answer
- in isolation, it is the same as false
.
Because a user could be in more than one circle and each circle may have a different permission, we need a way of combining permissions to produce a final result permission. nil
is treated differently here:
left |
right |
result |
nil |
nil |
nil |
nil |
true |
true |
nil |
false |
false |
true |
nil |
true |
true |
true |
true |
true |
false |
false |
false |
nil |
false |
false |
true |
false |
false |
false |
false |
To be considered granted, the result of combining the permissions must be true
(nil
is as good as false
again here).
nil
can thus be seen as a sort of weak false
, being easily overridden by a true, but also not by itself granting anything.
At first glance, this may seem a little odd, but it gives us a little additional flexibility which is useful for implementing features such as blocks (where false
is really useful!). With a little practice, it feels quite natural to use.
ACLs and Grants #
An ACL
is "just" a collection of Grant
s.
Grants combine the ID of the ACL they exist in with a verb id, a user or circle id and a permission, thus providing a decision about whether a particular action is permitted for a particular user (or all users in a particular circle).
Conceptually, an ACL contains a grant for every user-or-circle/verb combination, but most of the permissions are nil
. We do not record grants with nil
permissions in the database, saving substantially on storage space and compute requirements.
Controlled - Applying boundaries to an object #
An object is linked to one or more ACL
s by the Controlled
multimixin, which pairs an object ID with an ACL ID. Because it is a multimixin, a given object can have multiple ACLs applied. In the case of overlap, permissions are combined in the manner described earlier.
See also https://doc.bonfirenetworks.org/extension-bonfire_data_access_control.html for more docs (TODO: merge/deduplicate)