Source code for pyramid.authorization

from zope.interface import implementer

from pyramid.interfaces import IAuthorizationPolicy

from pyramid.location import lineage

from pyramid.compat import is_nonstr_iter

from import (

[docs]class ACLAuthorizationPolicy(object): """ An :term:`authorization policy` which consults an :term:`ACL` object attached to a :term:`context` to determine authorization information about a :term:`principal` or multiple principals. If the context is part of a :term:`lineage`, the context's parents are consulted for ACL information too. The following is true about this security policy. - When checking whether the 'current' user is permitted (via the ``permits`` method), the security policy consults the ``context`` for an ACL first. If no ACL exists on the context, or one does exist but the ACL does not explicitly allow or deny access for any of the effective principals, consult the context's parent ACL, and so on, until the lineage is exhausted or we determine that the policy permits or denies. During this processing, if any :data:`` ACE is found matching any principal in ``principals``, stop processing by returning an :class:`` instance (equals ``False``) immediately. If any :data:`` ACE is found matching any principal, stop processing by returning an :class:`` instance (equals ``True``) immediately. If we exhaust the context's :term:`lineage`, and no ACE has explicitly permitted or denied access, return an instance of :class:`` (equals ``False``). - When computing principals allowed by a permission via the :func:`` method, we compute the set of principals that are explicitly granted the ``permission`` in the provided ``context``. We do this by walking 'up' the object graph *from the root* to the context. During this walking process, if we find an explicit :data:`` ACE for a principal that matches the ``permission``, the principal is included in the allow list. However, if later in the walking process that principal is mentioned in any :data:`` ACE for the permission, the principal is removed from the allow list. If a :data:`` to the principal :data:`` is encountered during the walking process that matches the ``permission``, the allow list is cleared for all principals encountered in previous ACLs. The walking process ends after we've processed the any ACL directly attached to ``context``; a set of principals is returned. Objects of this class implement the :class:`pyramid.interfaces.IAuthorizationPolicy` interface. """ def permits(self, context, principals, permission): """ Return an instance of :class:`` instance if the policy permits access, return an instance of :class:`` if not.""" acl = '<No ACL found on any object in resource lineage>' for location in lineage(context): try: acl = location.__acl__ except AttributeError: continue for ace in acl: ace_action, ace_principal, ace_permissions = ace if ace_principal in principals: if not is_nonstr_iter(ace_permissions): ace_permissions = [ace_permissions] if permission in ace_permissions: if ace_action == Allow: return ACLAllowed(ace, acl, permission, principals, location) else: return ACLDenied(ace, acl, permission, principals, location) # default deny (if no ACL in lineage at all, or if none of the # principals were mentioned in any ACE we found) return ACLDenied( '<default deny>', acl, permission, principals, context) def principals_allowed_by_permission(self, context, permission): """ Return the set of principals explicitly granted the permission named ``permission`` according to the ACL directly attached to the ``context`` as well as inherited ACLs based on the :term:`lineage`.""" allowed = set() for location in reversed(list(lineage(context))): # NB: we're walking *up* the object graph from the root try: acl = location.__acl__ except AttributeError: continue allowed_here = set() denied_here = set() for ace_action, ace_principal, ace_permissions in acl: if not is_nonstr_iter(ace_permissions): ace_permissions = [ace_permissions] if (ace_action == Allow) and (permission in ace_permissions): if not ace_principal in denied_here: allowed_here.add(ace_principal) if (ace_action == Deny) and (permission in ace_permissions): denied_here.add(ace_principal) if ace_principal == Everyone: # clear the entire allowed set, as we've hit a # deny of Everyone ala (Deny, Everyone, ALL) allowed = set() break elif ace_principal in allowed: allowed.remove(ace_principal) allowed.update(allowed_here) return allowed