Add security.

1 files changed, 150 insertions, 0 deletions

diff --git a/repoze/bfg/security.py b/repoze/bfg/security.py
new file mode 100644
index 000000000..6f2c858e3
--- /dev/null
+++ b/repoze/bfg/security.py
@@ -0,0 +1,150 @@
+from zope.interface import implements
+from zope.location.location import LocationIterator
+
+from repoze.bfg.interfaces import ISecurityPolicy
+from repoze.bfg.interfaces import IViewPermission
+from repoze.bfg.interfaces import IViewPermissionFactory
+from repoze.bfg.interfaces import NoAuthorizationInformation
+
+Everyone = 'system.Everyone'
+Authenticated = 'system.Authenticated'
+Allow = 'Allow'
+Deny = 'Deny'
+
+class ACLAuthorizer(object):
+
+    def __init__(self, context, logger=None):
+        self.context = context
+        self.logger = logger
+
+    def get_acl(self, default=None):
+        return getattr(self.context, '__acl__', default)
+
+    def permits(self, permission, *principals):
+        acl = self.get_acl()
+        if acl is None:
+            raise NoAuthorizationInformation('%s item has no __acl__' % acl)
+
+        for ace in acl:
+            ace_action, ace_principal, ace_permissions = ace
+            for principal in flatten(principals):
+                if ace_principal == principal:
+                    permissions = flatten(ace_permissions)
+                    if permission in permissions:
+                        action = ace_action
+                        if action == Allow:
+                            result = Allowed(ace, acl, permission, principals,
+                                             self.context)
+                            self.logger and self.logger.debug(str(result))
+                            return result
+                        result = Denied(ace, acl, permission, principals,
+                                        self.context)
+                        self.logger and self.logger.debug(str(result))
+                        return result
+        result = Denied(None, acl, permission, principals, self.context)
+        self.logger and self.logger.debug(str(result))
+        return result
+        
+
+class RemoteUserACLSecurityPolicy(object):
+    implements(ISecurityPolicy)
+    authorizer_factory = ACLAuthorizer
+    
+    def __init__(self, logger=None):
+        self.logger = logger
+
+    def permits(self, context, request, permission):
+        userid = request.environ.get('REMOTE_USER', None)
+        effective_principals = [Everyone]
+
+        if userid is not None:
+            effective_principals.append(Authenticated)
+            effective_principals.append(userid)
+
+        for location in LocationIterator(context):
+            authorizer = self.authorizer_factory(context, self.logger)
+            try:
+                return authorizer.permits(permission, *effective_principals)
+            except NoAuthorizationInformation:
+                continue
+
+        return False
+
+class PermitsResult:
+    def __init__(self, ace, acl, permission, principals, context):
+        self.acl = acl
+        self.ace = ace
+        self.permission = permission
+        self.principals = principals
+        self.context_repr = repr(context)
+
+    def __str__(self):
+        msg = '%s: %r via ace %r in acl %s or principals %r in context %s'
+        msg = msg % (self.__class__.__name__,
+                     self.permission, self.ace, self.acl, self.principals,
+                     self.context_repr)
+        return msg
+
+class Denied(PermitsResult):
+    def __nonzero__(self):
+        return False
+
+    def __eq__(self, other):
+        if bool(other) is False:
+            return True
+
+class Allowed(PermitsResult):
+    def __nonzero__(self):
+        return True
+
+    def __eq__(self, other):
+        if bool(other) is True:
+            return True
+
+def flatten(x):
+    """flatten(sequence) -> list
+
+    Returns a single, flat list which contains all elements retrieved
+    from the sequence and all recursively contained sub-sequences
+    (iterables).
+
+    Examples:
+    >>> [1, 2, [3,4], (5,6)]
+    [1, 2, [3, 4], (5, 6)]
+    >>> flatten([[[1,2,3], (42,None)], [4,5], [6], 7, MyVector(8,9,10)])
+    [1, 2, 3, 42, None, 4, 5, 6, 7, 8, 9, 10]"""
+    if isinstance(x, basestring):
+        return [x]
+    result = []
+    for el in x:
+        if hasattr(el, "__iter__") and not isinstance(el, basestring):
+            result.extend(flatten(el))
+        else:
+            result.append(el)
+    return result
+
+class ViewPermission(object):
+    implements(IViewPermission)
+    def __init__(self, context, request, permission_name):
+        self.context = context
+        self.request = request
+        self.permission_name = permission_name
+    
+    def __call__(self, security_policy):
+        return security_policy.permits(self.context, self.request,
+                                       self.permission_name)
+
+    def __repr__(self):
+        return '<Permission at %s named %r for %r>' % (id(self),
+                                                       self.permission_name,
+                                                       self.request.view_name)
+        
+class ViewPermissionFactory(object):
+    implements(IViewPermissionFactory)
+    def __init__(self, permission_name):
+        self.permission_name = permission_name
+
+    def __call__(self, context, request):
+        return ViewPermission(context, request, self.permission_name)
+
+