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Default security policy for Zope3

Project Description

zope.securitypolicy

This package provides an useful security policy for Zope3. It’s the default security policy used in “zope3 the application” and many other zope-based projects.

Classic Zope Security Policy

This package implements a role-based security policy similar to the policy found in Zope 2. The security policy is responsible for deciding whether an interaction has a permission on an object. This security policy does this using grant and denial information. Managers can grant or deny:

  • roles to principals,
  • permissions to principals, and
  • permissions to roles

Grants and denials are stored as annotations on objects. To store grants and denials, objects must be annotatable:

>>> import zope.interface
>>> from zope.annotation.interfaces import IAttributeAnnotatable
>>> @zope.interface.implementer(IAttributeAnnotatable)
... class Ob:
...     pass
>>> ob = Ob()

We use objects to represent principals. These objects implement an interface named IPrincipal, but the security policy only uses the id and groups attributes:

>>> class Principal:
...     def __init__(self, id):
...         self.id = id
...         self.groups = []
>>> principal = Principal('bob')

Roles and permissions are also represented by objects, however, for the purposes of the security policy, only string ids are used.

The security policy provides a factory for creating interactions:

>>> import zope.securitypolicy.zopepolicy
>>> interaction = zope.securitypolicy.zopepolicy.ZopeSecurityPolicy()

An interaction represents a specific interaction between some principals (normally users) and the system. Normally, we are only concerned with the interaction of one principal with the system, although we can have interactions of multiple principals. Multiple-principal interactions normally occur when untrusted users store code on a system for later execution. When untrusted code is executing, the authors of the code participate in the interaction. An interaction has a permission on an object only if all of the principals participating in the interaction have access to the object.

The checkPermission method on interactions is used to test whether an interaction has a permission for an object. An interaction without participants always has every permission:

>>> interaction.checkPermission('P1', ob)
True

In this example, ‘P1’ is a permission id.

Normally, interactions have participants:

>>> class Participation:
...     interaction = None
>>> participation = Participation()
>>> participation.principal = principal
>>> interaction.add(participation)

If we have participants, then we don’t have a permission unless there are grants:

>>> interaction.checkPermission('P1', ob)
False

Note, however, that we always have the CheckerPublic permission:

>>> from zope.security.checker import CheckerPublic
>>> interaction.checkPermission(CheckerPublic, ob)
True

We make grants and denials on objects by adapting them to various granting interfaces. The objects returned from the adaptation are object-specific manager objects:

>>> from zope.securitypolicy import interfaces
>>> roleper  = interfaces.IRolePermissionManager(ob)
>>> prinrole = interfaces.IPrincipalRoleManager(ob)
>>> prinper  = interfaces.IPrincipalPermissionManager(ob)

The computations involved in checking permissions can be significant. To reduce the computational cost, caching is used extensively. We could invalidate the cache as we make grants, but the adapters for making grants will automatically invalidate the cache of the current interaction. They use the security-management apis to do this. To take advantage of the cache invalidation, we’ll need to let the security-management system manage our interactions. First, we’ll set our security policy as the default:

>>> import zope.security.management
>>> oldpolicy = zope.security.management.setSecurityPolicy(
...      zope.securitypolicy.zopepolicy.ZopeSecurityPolicy)

and then we’ll create a new interaction:

>>> participation = Participation()
>>> participation.principal = principal
>>> zope.security.management.newInteraction(participation)
>>> interaction = zope.security.management.getInteraction()

We normally provide access by granting permissions to roles for an object:

>>> roleper.grantPermissionToRole('P1', 'R1')

and then granting roles to principals for an object (local roles):

>>> prinrole.assignRoleToPrincipal('R1', 'bob')

The combination of these grants, which we call a role-based grant, provides the permission:

>>> interaction.checkPermission('P1', ob)
True

We can also provide a permission directly:

>>> prinper.grantPermissionToPrincipal('P2', 'bob')
>>> interaction.checkPermission('P2', ob)
True

Permission grants or denials override role-based grant or denials. So if we deny P1:

>>> prinper.denyPermissionToPrincipal('P1', 'bob')

we cause the interaction to lack the permission, despite the role grants:

>>> interaction.checkPermission('P1', ob)
False

Similarly, even if we have a role-based denial of P2:

>>> roleper.denyPermissionToRole('P2', 'R1')

we still have access, because of the permission-based grant:

>>> interaction.checkPermission('P2', ob)
True

A role-based denial doesn’t actually deny a permission; rather it prevents the granting of a permission. So, if we have both grants and denials based on roles, we have access:

>>> roleper.grantPermissionToRole('P3', 'R1')
>>> roleper.grantPermissionToRole('P3', 'R2')
>>> roleper.denyPermissionToRole('P3', 'R3')
>>> prinrole.removeRoleFromPrincipal('R2', 'bob')
>>> prinrole.assignRoleToPrincipal('R3', 'bob')
>>> interaction.checkPermission('P3', ob)
True

Global grants

Grants made to an object are said to be “local”. We can also make global grants:

>>> from zope.securitypolicy.rolepermission import \
...     rolePermissionManager as roleperG
>>> from zope.securitypolicy.principalpermission import \
...     principalPermissionManager as prinperG
>>> from zope.securitypolicy.principalrole import \
...     principalRoleManager as prinroleG

And the same rules apply to global grants and denials.

>>> roleperG.grantPermissionToRole('P1G', 'R1G', False)

In these tests, we aren’t bothering to define any roles, permissions, or principals, so we pass an extra argument that tells the granting routines not to check the validity of the values.

>>> prinroleG.assignRoleToPrincipal('R1G', 'bob', False)
>>> interaction.checkPermission('P1G', ob)
True
>>> prinperG.grantPermissionToPrincipal('P2G', 'bob', False)
>>> interaction.checkPermission('P2G', ob)
True
>>> prinperG.denyPermissionToPrincipal('P1G', 'bob', False)
>>> interaction.checkPermission('P1G', ob)
False
>>> roleperG.denyPermissionToRole('P2G', 'R1G', False)
>>> interaction.checkPermission('P2G', ob)
True
>>> roleperG.grantPermissionToRole('P3G', 'R1G', False)
>>> roleperG.grantPermissionToRole('P3G', 'R2G', False)
>>> roleperG.denyPermissionToRole('P3G', 'R3G', False)
>>> prinroleG.removeRoleFromPrincipal('R2G', 'bob', False)
>>> prinroleG.assignRoleToPrincipal('R3G', 'bob', False)
>>> interaction.checkPermission('P3G', ob)
True

Local versus global grants

We, of course, acquire global grants by default:

>>> interaction.checkPermission('P1G', ob)
False
>>> interaction.checkPermission('P2G', ob)
True
>>> interaction.checkPermission('P3G', ob)
True

Local role-based grants do not override global principal-specific denials:

>>> roleper.grantPermissionToRole('P1G', 'R1G')
>>> prinrole.assignRoleToPrincipal('R1G', 'bob')
>>> interaction.checkPermission('P1G', ob)
False

And local role-based denials don’t override global principal-grants:

>>> roleper.denyPermissionToRole('P2G', 'R1G')
>>> interaction.checkPermission('P2G', ob)
True

A local role-based deny can cancel a global role-based grant:

>>> roleper.denyPermissionToRole('P3G', 'R1G')
>>> interaction.checkPermission('P3G', ob)
False

and a local role-based grant can override a global role-based denial:

>>> roleperG.denyPermissionToRole('P4G', 'R1G', False)
>>> prinroleG.assignRoleToPrincipal('R1G', "bob", False)
>>> interaction.checkPermission('P4G', ob)
False
>>> roleper.grantPermissionToRole('P4G', 'R1G')
>>> interaction.checkPermission('P4G', ob)
True
>>> prinroleG.removeRoleFromPrincipal('R1G', "bob", False)
>>> interaction.checkPermission('P4G', ob)
True

Of course, a local permission-based grant or denial overrides any global setting and overrides local role-based grants or denials:

>>> prinper.grantPermissionToPrincipal('P3G', 'bob')
>>> interaction.checkPermission('P3G', ob)
True
>>> prinper.denyPermissionToPrincipal('P2G', 'bob')
>>> interaction.checkPermission('P2G', ob)
False

Sublocations

We can have sub-locations. A sublocation of a location is an object whose __parent__ attribute is the location:

>>> ob2 = Ob()
>>> ob2.__parent__ = ob

By default, sublocations acquire grants from higher locations:

>>> interaction.checkPermission('P1', ob2)
False
>>> interaction.checkPermission('P2', ob2)
True
>>> interaction.checkPermission('P3', ob2)
True
>>> interaction.checkPermission('P1G', ob2)
False
>>> interaction.checkPermission('P2G', ob2)
False
>>> interaction.checkPermission('P3G', ob2)
True
>>> interaction.checkPermission('P4G', ob2)
True

Sublocation role-based grants do not override their parent principal-specific denials:

>>> roleper2  = interfaces.IRolePermissionManager(ob2)
>>> prinrole2 = interfaces.IPrincipalRoleManager(ob2)
>>> prinper2  = interfaces.IPrincipalPermissionManager(ob2)
>>> roleper2.grantPermissionToRole('P1', 'R1')
>>> prinrole2.assignRoleToPrincipal('R1', 'bob')
>>> interaction.checkPermission('P1', ob2)
False

And local role-based denials don’t override their parents principal-grant:

>>> roleper2.denyPermissionToRole('P2', 'R1')
>>> interaction.checkPermission('P2', ob2)
True

A local role-based deny can cancel a parent role-based grant:

>>> roleper2.denyPermissionToRole('P3', 'R1')
>>> interaction.checkPermission('P3', ob2)
False

and a local role-based grant can override a parent role-based denial:

>>> roleper.denyPermissionToRole('P4', 'R1')
>>> prinrole.assignRoleToPrincipal('R1', 'bob')
>>> interaction.checkPermission('P4', ob2)
False
>>> roleper2.grantPermissionToRole('P4', 'R1')
>>> interaction.checkPermission('P4', ob2)
True
>>> prinrole.removeRoleFromPrincipal('R1', 'bob')
>>> interaction.checkPermission('P4', ob2)
True

Of course, a local permission-based grant or denial overrides any global setting and overrides local role-based grants or denials:

>>> prinper.grantPermissionToPrincipal('P3', 'bob')
>>> interaction.checkPermission('P3', ob2)
True
>>> prinper.denyPermissionToPrincipal('P2', 'bob')
>>> interaction.checkPermission('P2', ob2)
False

If an object is not annotatable, but does have a parent, it will get its grants from its parent:

>>> class C:
...     pass
>>> ob3 = C()
>>> ob3.__parent__ = ob
>>> interaction.checkPermission('P1', ob3)
False
>>> interaction.checkPermission('P2', ob3)
False
>>> interaction.checkPermission('P3', ob3)
True
>>> interaction.checkPermission('P1G', ob3)
False
>>> interaction.checkPermission('P2G', ob3)
False
>>> interaction.checkPermission('P3G', ob3)
True
>>> interaction.checkPermission('P4G', ob3)
True

The same results will be had if there are multiple non-annotatable objects:

>>> ob3.__parent__ = C()
>>> ob3.__parent__.__parent__ = ob
>>> interaction.checkPermission('P1', ob3)
False
>>> interaction.checkPermission('P2', ob3)
False
>>> interaction.checkPermission('P3', ob3)
True
>>> interaction.checkPermission('P1G', ob3)
False
>>> interaction.checkPermission('P2G', ob3)
False
>>> interaction.checkPermission('P3G', ob3)
True
>>> interaction.checkPermission('P4G', ob3)
True

and if an object doesn’t have a parent:

>>> ob4 = C()

it will have whatever grants were made globally:

>>> interaction.checkPermission('P1', ob4)
False
>>> interaction.checkPermission('P2', ob4)
False
>>> interaction.checkPermission('P3', ob4)
False
>>> interaction.checkPermission('P1G', ob4)
False
>>> interaction.checkPermission('P2G', ob4)
True
>>> interaction.checkPermission('P3G', ob4)
False
>>> interaction.checkPermission('P4G', ob4)
False
>>> prinroleG.assignRoleToPrincipal('R1G', "bob", False)
>>> interaction.checkPermission('P3G', ob4)
True

We’ll get the same result if we have a non-annotatable parent without a parent:

>>> ob3.__parent__ = C()
>>> interaction.checkPermission('P1', ob3)
False
>>> interaction.checkPermission('P2', ob3)
False
>>> interaction.checkPermission('P3', ob3)
False
>>> interaction.checkPermission('P1G', ob3)
False
>>> interaction.checkPermission('P2G', ob3)
True
>>> interaction.checkPermission('P3G', ob3)
True
>>> interaction.checkPermission('P4G', ob3)
False

The Anonymous role

The security policy defines a special role named “zope.Anonymous”. All principals have this role and the role cannot be taken away.

>>> roleperG.grantPermissionToRole('P5', 'zope.Anonymous', False)
>>> interaction.checkPermission('P5', ob2)
True

Proxies

Objects may be proxied:

>>> from zope.security.checker import ProxyFactory
>>> ob = ProxyFactory(ob)
>>> interaction.checkPermission('P1', ob)
False
>>> interaction.checkPermission('P2', ob)
False
>>> interaction.checkPermission('P3', ob)
True
>>> interaction.checkPermission('P1G', ob)
False
>>> interaction.checkPermission('P2G', ob)
False
>>> interaction.checkPermission('P3G', ob)
True
>>> interaction.checkPermission('P4G', ob)
True

as may their parents:

>>> ob3 = C()
>>> ob3.__parent__ = ob
>>> interaction.checkPermission('P1', ob3)
False
>>> interaction.checkPermission('P2', ob3)
False
>>> interaction.checkPermission('P3', ob3)
True
>>> interaction.checkPermission('P1G', ob3)
False
>>> interaction.checkPermission('P2G', ob3)
False
>>> interaction.checkPermission('P3G', ob3)
True
>>> interaction.checkPermission('P4G', ob3)
True

Groups

Principals may have groups. Groups are also principals (and, thus, may have groups).

If a principal has groups, the groups are available as group ids in the principal’s groups attribute. The interaction has to convert these group ids to group objects, so that it can tell whether the groups have groups. It does this by calling the getPrincipal method on the principal authentication service, which is responsible for, among other things, converting a principal id to a principal. For our examples here, we’ll create and register a stub principal authentication service:

>>> from zope.authentication.interfaces import IAuthentication
>>> @zope.interface.implementer(IAuthentication)
... class FauxPrincipals(object):
...     def __init__(self):
...         self.data = {}
...     def __setitem__(self, key, value):
...         self.data[key] = value
...     def __getitem__(self, key):
...         return self.data[key]
...     def getPrincipal(self, id):
...         return self.data[id]
>>> auth = FauxPrincipals()
>>> from zope.component import provideUtility
>>> provideUtility(auth, IAuthentication)

Let’s define a group:

>>> auth['g1'] = Principal('g1')

Let’s put the principal in our group. We do that by adding the group id to the new principals groups:

>>> principal.groups.append('g1')

Of course, the principal doesn’t have permissions not granted:

>>> interaction.checkPermission('gP1', ob)
False

Now, if we grant a permission to the group:

>>> prinper.grantPermissionToPrincipal('gP1', 'g1')

We see that our principal has the permission:

>>> interaction.checkPermission('gP1', ob)
True

This works even if the group grant is global:

>>> interaction.checkPermission('gP1G', ob)
False
>>> prinperG.grantPermissionToPrincipal('gP1G', 'g1', True)
>>> interaction.checkPermission('gP1G', ob)
True

Grants are, of course, acquired:

>>> interaction.checkPermission('gP1', ob2)
True
>>> interaction.checkPermission('gP1G', ob2)
True

Inner grants can override outer grants:

>>> prinper2.denyPermissionToPrincipal('gP1', 'g1')
>>> interaction.checkPermission('gP1', ob2)
False

But principal grants always trump group grants:

>>> prinper2.grantPermissionToPrincipal('gP1', 'bob')
>>> interaction.checkPermission('gP1', ob2)
True

Groups can have groups too:

>>> auth['g2'] = Principal('g2')
>>> auth['g1'].groups.append('g2')

If we grant to the new group:

>>> prinper.grantPermissionToPrincipal('gP2', 'g2')

Then we, of course have that permission too:

>>> interaction.checkPermission('gP2', ob2)
True

Just as principal grants override group grants, group grants can override other group grants:

>>> prinper.denyPermissionToPrincipal('gP2', 'g1')
>>> interaction.checkPermission('gP2', ob2)
False

Principals can be in more than one group. Let’s define a new group:

>>> auth['g3'] = Principal('g3')
>>> principal.groups.append('g3')
>>> prinper.grantPermissionToPrincipal('gP2', 'g3')

Now, the principal has two groups. In one group, the permission ‘gP2’ is denied, but in the other, it is allowed. In a case like this, the permission is allowed:

>>> interaction.checkPermission('gP2', ob2)
True

In a case where a principal has two or more groups, the group denies prevent allows from their parents. They don’t prevent the principal from getting an allow from another principal.

Grants can be inherited from ancestor groups through multiple paths. Let’s grant a permission to g2 and deny it to g1:

>>> prinper.grantPermissionToPrincipal('gP3', 'g2')
>>> prinper.denyPermissionToPrincipal('gP3', 'g1')

Now, as before, the deny in g1 blocks the grant in g2:

>>> interaction.checkPermission('gP3', ob2)
False

Let’s make g2 a group of g3:

>>> auth['g3'].groups.append('g2')

Now, we get g2’s grant through g3, and access is allowed:

>>> interaction.invalidate_cache()
>>> interaction.checkPermission('gP3', ob2)
True

We can assign roles to groups:

>>> prinrole.assignRoleToPrincipal('gR1', 'g2')

and get permissions through the roles:

>>> roleper.grantPermissionToRole('gP4', 'gR1')
>>> interaction.checkPermission('gP4', ob2)
True

we can override role assignments to groups through subgroups:

>>> prinrole.removeRoleFromPrincipal('gR1', 'g1')
>>> prinrole.removeRoleFromPrincipal('gR1', 'g3')
>>> interaction.checkPermission('gP4', ob2)
False

and through principals:

>>> prinrole.assignRoleToPrincipal('gR1', 'bob')
>>> interaction.checkPermission('gP4', ob2)
True

We clean up the changes we made in these examples:

>>> zope.security.management.endInteraction()
>>> ignore = zope.security.management.setSecurityPolicy(oldpolicy)

Changes

4.2.0 (2017-08-24)

  • Add <zope:deny> directive, which is a mirror of the <zope:grant> directive.
  • Add support for Python 3.6.

4.1.0 (2016-11-05)

  • Add support for Python 3.5.

  • Drop support for Python 2.6.

  • Add support to grant multiple permissions with one ZCML statement. Example:

    <grant
      role="my-role"
      permissions="zope.foo
                   zope.bar" />
    

4.0.0 (2014-12-24)

4.0.0a1 (2013-02-22)

  • Add support for Python 3.3.
  • Replace deprecated zope.interface.classProvides usage with equivalent zope.interface.provider decorator.
  • Replace deprecated zope.interface.implements usage with equivalent zope.interface.implementer decorator.
  • Drop support for Python 2.4 and 2.5.

3.7.0 (2010-09-25)

  • LP #131115: Clean up inconsistency in getSetting interface definitions and actual usage for the various security maps.
  • LP #564525: fix permission moved from zope.app.dublincore namespace to zope.dublincore.
  • Remove unused imports and pep8 cleanup.
  • Use doctest module instead of the deprecated zope.testing.doctest.
  • AnnotationGrantInfo implements IGrantInfo.
  • Add test extra to declare test dependency on zope.component [test].
  • Add an extra named dublincore to express optional dependency on zope.dublincore >= 3.7.
  • Add tests for ZCML files making sure they include everything they need.

3.6.1 (2009-07-24)

  • Make tests work when the default and Zope vocabulary registry compete in the cleanup.

3.6.0 (2009-03-14)

  • Change zope.app.security dependency to the new zope.authentication package, dropping a big number of unused dependencies.
  • Get rid of zope.app.testing and other testing dependencices.
  • Add ZODB3 to install dependencies, because we use Persistent class. We didn’t fail before, because it was installed implicitly.

3.5.1 (2009-03-10)

  • Don’t depend on the hook extra of zope.component, as we don’t need it explicitly.
  • Import security settings (Allow, Deny, Unset) in the interfaces module from the zope.securitypolicy.settings, added in previous release instead of old zope.app.security.settings. The zope.app.security will be adapted to import them from zope.securitypolicy.interfaces.
  • Use _z_instances instead of __instances__ for storing instances for zope.securitypolicy.settings.PermissionSetting singleton implementation, because __*__ name pattern is reserved for special names in python.
  • Add security protections for the PermissionSetting.
  • Improve documentation formatting, add it to the package’s long description.
  • Remove unneeded dependencies.
  • Remove old zpkg-related files and zcml slugs.

3.5.0 (2009-01-31)

  • Include settings that were previously imported from zope.app.security.

3.4.2 (2009-01-28)

  • Change mailing list address to zope-dev at zope.org. Fix package homepage to the pypi page.
  • Fix test in buildout which still depended on zope.app.securitypolicy by mistake.
  • Remove explicit dependency on zope.app.form from setup.py; nothing in the code directly depends on this.

3.4.1 (2008-06-02)

  • Fix reference to deprecated security policy from ZCML.

3.4.0 (2007-09-25)

  • Initial documented release
Release History

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