path: root/repoze/bfg/security.py

from zope.interface import providedBy

from zope.deprecation import deprecated

from repoze.bfg.interfaces import IAuthenticationPolicy
from repoze.bfg.interfaces import IAuthorizationPolicy
from repoze.bfg.interfaces import ISecuredView
from repoze.bfg.interfaces import IViewClassifier

from repoze.bfg.exceptions import Forbidden as Unauthorized # b/c import
from repoze.bfg.threadlocal import get_current_registry

Unauthorized # prevent PyFlakes from complaining

deprecated('Unauthorized',
    "('from repoze.bfg.security import Unauthorized' was  "
    "deprecated as of repoze.bfg 1.1; instead use 'from "
    "repoze.bfg.exceptions import Forbidden')",
    )

Everyone = 'system.Everyone'
Authenticated = 'system.Authenticated'
Allow = 'Allow'
Deny = 'Deny'

class AllPermissionsList(object):
    """ Stand in 'permission list' to represent all permissions """
    def __iter__(self):
        return ()
    def __contains__(self, other):
        return True
    def __eq__(self, other):
        return isinstance(other, self.__class__)

ALL_PERMISSIONS = AllPermissionsList()
DENY_ALL = (Deny, Everyone, ALL_PERMISSIONS)

def has_permission(permission, context, request):
    """ Provided a permission (a string or unicode object), a context
    (a :term:`model` instance) and a request object, return an
    instance of :data:`repoze.bfg.security.Allowed` if the permission
    is granted in this context to the user implied by the
    request. Return an instance of :mod:`repoze.bfg.security.Denied`
    if this permission is not granted in this context to this user.
    This function delegates to the current authentication and
    authorization policies.  Return
    :data:`repoze.bfg.security.Allowed` unconditionally if no
    authentication policy has been configured in this application."""
    try:
        reg = request.registry
    except AttributeError:
        reg = get_current_registry() # b/c
    authn_policy = reg.queryUtility(IAuthenticationPolicy)
    if authn_policy is None:
        return Allowed('No authentication policy in use.')

    authz_policy = reg.queryUtility(IAuthorizationPolicy)
    if authz_policy is None:
        raise ValueError('Authentication policy registered without '
                         'authorization policy') # should never happen
    principals = authn_policy.effective_principals(request)
    return authz_policy.permits(context, principals, permission)

def authenticated_userid(request):
    """ Return the userid of the currently authenticated user or
    ``None`` if there is no :term:`authentication policy` in effect or
    there is no currently authenticated user."""
    try:
        reg = request.registry
    except AttributeError:
        reg = get_current_registry() # b/c

    policy = reg.queryUtility(IAuthenticationPolicy)
    if policy is None:
        return None
    return policy.authenticated_userid(request)

def effective_principals(request):
    """ Return the list of 'effective' :term:`principal` identifiers
    for the ``request``.  This will include the userid of the
    currently authenticated user if a user is currently
    authenticated. If no :term:`authentication policy` is in effect,
    this will return an empty sequence."""
    try:
        reg = request.registry
    except AttributeError:
        reg = get_current_registry() # b/c

    policy = reg.queryUtility(IAuthenticationPolicy)
    if policy is None:
        return []
    return policy.effective_principals(request)

def principals_allowed_by_permission(context, permission):
    """ Provided a ``context`` (a model object), and a ``permission``
    (a string or unicode object), if a :term:`authorization policy` is
    in effect, return a sequence of :term:`principal` ids that possess
    the permission in the ``context``.  If no authorization policy is
    in effect, this will return a sequence with the single value
    :mod:`repoze.bfg.security.Everyone` (the special principal
    identifier representing all principals).

    .. note:: even if an :term:`authorization policy` is in effect,
       some (exotic) authorization policies may not implement the
       required machinery for this function; those will cause a
       :exc:`NotImplementedError` exception to be raised when this
       function is invoked.
    """
    reg = get_current_registry()
    policy = reg.queryUtility(IAuthorizationPolicy)
    if policy is None:
        return [Everyone]
    return policy.principals_allowed_by_permission(context, permission)

def view_execution_permitted(context, request, name=''):
    """ If the view specified by ``context`` and ``name`` is protected
    by a :term:`permission`, check the permission associated with the
    view using the effective authentication/authorization policies and
    the ``request``.  Return a boolean result.  If no
    :term:`authorization policy` is in effect, or if the view is not
    protected by a permission, return ``True``."""
    try:
        reg = request.registry
    except AttributeError:
        reg = get_current_registry() # b/c
    provides = [IViewClassifier] + map(providedBy, (request, context))
    view = reg.adapters.lookup(provides, ISecuredView, name=name)
    if view is None:
        return Allowed(
            'Allowed: view name %r in context %r (no permission defined)' %
            (name, context))
    return view.__permitted__(context, request)

def remember(request, principal, **kw):
    """ Return a sequence of header tuples (e.g. ``[('Set-Cookie',
    'foo=abc')]``) suitable for 'remembering' a set of credentials
    implied by the data passed as ``principal`` and ``*kw`` using the
    current :term:`authentication policy`.  Common usage might look
    like so within the body of a view function (``response`` is
    assumed to be an :term:`WebOb` -style :term:`response` object
    computed previously by the view code)::

      from repoze.bfg.security import remember
      headers = remember(request, 'chrism', password='123', max_age='86400')
      response.headerlist.extend(headers)
      return response

    If no :term:`authentication policy` is in use, this function will
    always return an empty sequence.  If used, the composition and
    meaning of ``**kw`` must be agreed upon by the calling code and
    the effective authentication policy."""
    try:
        reg = request.registry
    except AttributeError:
        reg = get_current_registry() # b/c
    policy = reg.queryUtility(IAuthenticationPolicy)
    if policy is None:
        return []
    else:
        return policy.remember(request, principal, **kw)

def forget(request):
    """ Return a sequence of header tuples (e.g. ``[('Set-Cookie',
    'foo=abc')]``) suitable for 'forgetting' the set of credentials
    possessed by the currently authenticated user.  A common usage
    might look like so within the body of a view function
    (``response`` is assumed to be an :term:`WebOb` -style
    :term:`response` object computed previously by the view code)::

      from repoze.bfg.security import forget
      headers = forget(request)
      response.headerlist.extend(headers)
      return response

    If no :term:`authentication policy` is in use, this function will
    always return an empty sequence."""
    try:
        reg = request.registry
    except AttributeError:
        reg = get_current_registry() # b/c
    policy = reg.queryUtility(IAuthenticationPolicy)
    if policy is None:
        return []
    else:
        return policy.forget(request)
    
class PermitsResult(int):
    def __new__(cls, s, *args):
        inst = int.__new__(cls, cls.boolval)
        inst.s = s
        inst.args = args
        return inst
        
    @property
    def msg(self):
        return self.s % self.args

    def __str__(self):
        return self.msg

    def __repr__(self):
        return '<%s instance at %s with msg %r>' % (self.__class__.__name__,
                                                    id(self),
                                                    self.msg)

class Denied(PermitsResult):
    """ An instance of ``Denied`` is returned when a security-related
    API or other :mod:`repoze.bfg` code denies an action unrelated to
    an ACL check.  It evaluates equal to all boolean false types.  It
    has an attribute named ``msg`` describing the circumstances for
    the deny."""
    boolval = 0

class Allowed(PermitsResult):
    """ An instance of ``Allowed`` is returned when a security-related
    API or other :mod:`repoze.bfg` code allows an action unrelated to
    an ACL check.  It evaluates equal to all boolean true types.  It
    has an attribute named ``msg`` describing the circumstances for
    the allow."""
    boolval = 1

class ACLPermitsResult(int):
    def __new__(cls, ace, acl, permission, principals, context):
        inst = int.__new__(cls, cls.boolval)
        inst.permission = permission
        inst.ace = ace
        inst.acl = acl
        inst.principals = principals
        inst.context = context
        return inst

    @property
    def msg(self):
        s = ('%s permission %r via ACE %r in ACL %r on context %r for '
             'principals %r')
        return s % (self.__class__.__name__,
                    self.permission,
                    self.ace,
                    self.acl,
                    self.context,
                    self.principals)

    def __str__(self):
        return self.msg

    def __repr__(self):
        return '<%s instance at %s with msg %r>' % (self.__class__.__name__,
                                                    id(self),
                                                    self.msg)

class ACLDenied(ACLPermitsResult):
    """ An instance of ``ACLDenied`` represents that a security check
    made explicitly against ACL was denied.  It evaluates equal to all
    boolean false types.  It also has attributes which indicate which
    acl, ace, permission, principals, and context were involved in the
    request.  Its __str__ method prints a summary of these attributes
    for debugging purposes.  The same summary is available as the
    ``msg`` attribute."""
    boolval = 0

class ACLAllowed(ACLPermitsResult):
    """ An instance of ``ACLAllowed`` represents that a security check
    made explicitly against ACL was allowed.  It evaluates equal to
    all boolean true types.  It also has attributes which indicate
    which acl, ace, permission, principals, and context were involved
    in the request.  Its __str__ method prints a summary of these
    attributes for debugging purposes.  The same summary is available
    as the ``msg`` attribute."""
    boolval = 1