cubicweb-localperms 1.1.0

allow definition of local permissions

Summary

This cube allows definition of local permissions using a generic CWPermission entity type which you should use in your schema definition.

A CWPermission entity type:

• has a name and a label

• means groups linked to it through the ‘require_group’ relation have the <name> permission on entities linked through the ‘require_permission’ object relation.

To speed-up things, a ‘has_group_permission’ relation is automatically maintained, so ‘P require_group G, U in_group G’ is equivalent to ‘U has_group_permission P’.

Client cubes should explicitly add ‘X granted_permission CWPermission’ and ‘X require_permission CWPermission’ for each type that should have local permission, the first one being explicitly granted and the other automatically propagated. Hence possible subjects of granted_permission should be a subset of require_permission possible subjects.

You should then use require_permission in your schema security definition, since this is the one which is automatically propagated.

Example of configuration

class granted_permission(RelationDefinition):
    subject = 'Project'
    object = 'CWPermission'

class require_permission(RelationDefinition):
    subject = ('Project', 'Version')
    object = 'CWPermission'

class Project(EntityType):
    """a project, only visible to managers and users having the 'view' local permission
    """
    __permissions__ = {
       'read':   ('managers', ERQLExpression('X require_permission P, P name "view", '
                                             'U has_group_permission P'),),
       'update': ('managers', 'owners',),
       'delete': ('managers', ),
       'add':    ('managers', 'users',),)
       }

class Version(EntityType):
    """a version defines the content of a particular project's release"""
    __permissions__ = {
       'read':   ('managers', ERQLExpression('X require_permission P, P name "view", '
                                             'U has_group_permission P'),),
       'update': ('managers', 'owners',),
       'delete': ('managers', ),
       'add':    ('managers', 'users',),)
       }

class version_of(RelationDefinition):
    """link a version to its project. A version is necessarily linked to one and
    only one project.
    """
    __permissions__ = {
       'read':   ('managers', 'users',),
       'delete': ('managers', ),
       'add':    ('managers', RRQLExpression('O require_permission P, P name "manage",'
                                             'U has_group_permission P'),)
                   }
    subject = 'Version'
    object = 'Project'
    cardinality = '1*'

This configuration indicates that we’ve two distinct permissions (forthcoming CWPermission entities):

• one named ‘view’, which allows some users to view a particular project and its versions

• another named “manage” which provides rights to create new versions on a project

Note

Notice that we granted ‘add’ permission of Version to the ‘users’ group. The idea is that it’s hard for the web ui to get ‘add’ permission until the entity doesn’t exist yet. So we let the ‘version_of’ relation carry the security (easier to check, since we usually know the project on which we may want to add a version). And as we know that this relation is mandatory for Version, we also ensure users can only add versions on project where they have the “manage” permission.

Also, we let the ‘read’ permission on ‘version_of’ not only because rql expression aren’t supported there, but because in this case we know one won’t be able to see a relation between two entities he can’t see…

Now the idea is that managers will grant permission on projects, and those will then be propagated as configured. You will want to use sets in cubicweb_localperms.hooks to configure how permissions should be propagated when desired. In our example, put in your cube’s hooks.py something like:

from cubicweb_localperms import hooks
# relations where the "main" entity is the object. We could also
# have modified hooks.S_RELS for relations where the "main" entity
# is the subject
hooks.O_RELS.add('version_of')

The permission given to a project will be automatically added/removed as version are created / deleted.

Last but not least, when defining the entity class for Project, defines __permissions__ as below:

class Project(AnyEntity):
    __permissions__ = ('view', 'manage',)

So that when going on the ‘security’ view for a project (in ‘more actions’ sub-menu by default), you should be proposed an interface to configurate local permissions with a combo-box prefilled with proper permission names instead of a free text input, which greatly reduces the risk of error.

Also, you’ll find in cubicweb_localperms some functions to ease building of rql expression in your schema definition. Those written in above example could be written as below using those functions:

from cubicweb_localperms import xexpr, oexpr

class Project(EntityType):
    __permissions__ = {'read':   ('managers', xexpr('view'),),
                       'update': ('managers', 'owners',),
                       'delete': ('managers', ),
                       'add':    ('managers', 'users',),)
                       }

class Version(EntityType):
    __permissions__ = {'read':   ('managers', xexpr('view'),),
                       'update': ('managers', 'owners',),
                       'delete': ('managers', ),
                       'add':    ('managers', 'users',),)
                       }

class version_of(RelationDefinition):
    __permissions__ = {'read':   ('managers', 'users',),
                       'update': ('managers', 'owners',),
                       'delete': ('managers', ),
                       'add':    ('managers', oexpr('manage'),)
                      }