/usr/share/pyshared/zope/pagetemplate/engine.py is in python-zope.pagetemplate 4.0.1-0ubuntu1.
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#
# Copyright (c) 2002-2009 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################
"""Expression engine configuration and registration.
Each expression engine can have its own expression types and base names.
"""
__docformat__ = 'restructuredtext'
import sys
from zope import component
from zope.interface import implementer
from zope.component.interfaces import ComponentLookupError
from zope.traversing.interfaces import IPathAdapter, ITraversable
from zope.traversing.interfaces import TraversalError
from zope.traversing.adapters import traversePathElement
from zope.security.untrustedpython import rcompile
from zope.security.proxy import ProxyFactory, removeSecurityProxy
from zope.security.untrustedpython.builtins import SafeBuiltins
from zope.i18n import translate
from zope.tales.expressions import PathExpr, StringExpr, NotExpr, DeferExpr
from zope.tales.expressions import SimpleModuleImporter
from zope.tales.pythonexpr import PythonExpr
from zope.tales.tales import ExpressionEngine, Context
from zope.pagetemplate.i18n import ZopeMessageFactory as _
class InlineCodeError(Exception):
pass
class ZopeTraverser(object):
def __init__(self, proxify=None):
if proxify is None:
self.proxify = lambda x: x
else:
self.proxify = proxify
def __call__(self, object, path_items, econtext):
"""Traverses a sequence of names, first trying attributes then items.
"""
request = getattr(econtext, 'request', None)
path_items = list(path_items)
path_items.reverse()
while path_items:
name = path_items.pop()
# special-case dicts for performance reasons
if getattr(object, '__class__', None) == dict:
object = object[name]
else:
object = traversePathElement(object, name, path_items,
request=request)
object = self.proxify(object)
return object
zopeTraverser = ZopeTraverser(ProxyFactory)
class ZopePathExpr(PathExpr):
def __init__(self, name, expr, engine):
super(ZopePathExpr, self).__init__(name, expr, engine, zopeTraverser)
trustedZopeTraverser = ZopeTraverser()
class TrustedZopePathExpr(PathExpr):
def __init__(self, name, expr, engine):
super(TrustedZopePathExpr, self).__init__(name, expr, engine,
trustedZopeTraverser)
# Create a version of the restricted built-ins that uses a safe
# version of getattr() that wraps values in security proxies where
# appropriate:
class ZopePythonExpr(PythonExpr):
def __call__(self, econtext):
__traceback_info__ = self.text
vars = self._bind_used_names(econtext, SafeBuiltins)
return eval(self._code, vars)
def _compile(self, text, filename):
return rcompile.compile(text, filename, 'eval')
class ZopeContextBase(Context):
"""Base class for both trusted and untrusted evaluation contexts."""
def translate(self, msgid, domain=None, mapping=None, default=None):
return translate(msgid, domain, mapping,
context=self.request, default=default)
evaluateInlineCode = False
def evaluateCode(self, lang, code):
if not self.evaluateInlineCode:
raise InlineCodeError(
_('Inline Code Evaluation is deactivated, which means that '
'you cannot have inline code snippets in your Page '
'Template. Activate Inline Code Evaluation and try again.'))
# TODO This is only needed when self.evaluateInlineCode is true,
# so should only be needed for zope.app.pythonpage.
from zope.app.interpreter.interfaces import IInterpreter
interpreter = component.queryUtility(IInterpreter, lang)
if interpreter is None:
error = _('No interpreter named "${lang_name}" was found.',
mapping={'lang_name': lang})
raise InlineCodeError(error)
globals = self.vars.copy()
result = interpreter.evaluateRawCode(code, globals)
# Add possibly new global variables.
old_names = self.vars.keys()
for name, value in globals.items():
if name not in old_names:
self.setGlobal(name, value)
return result
class ZopeContext(ZopeContextBase):
"""Evaluation context for untrusted programs."""
def evaluateMacro(self, expr):
"""evaluateMacro gets security-proxied macro programs when this
is run with the zopeTraverser, and in other untrusted
situations. This will cause evaluation to fail in
zope.tal.talinterpreter, which knows nothing of security proxies.
Therefore, this method removes any proxy from the evaluated
expression.
>>> output = [('version', 'xxx'), ('mode', 'html'), ('other', 'things')]
>>> def expression(context):
... return ProxyFactory(output)
...
>>> zc = ZopeContext(ExpressionEngine, {})
>>> out = zc.evaluateMacro(expression)
>>> type(out)
<type 'list'>
The method does some trivial checking to make sure we are getting
back a macro like we expect: it must be a sequence of sequences, in
which the first sequence must start with 'version', and the second
must start with 'mode'.
>>> del output[0]
>>> zc.evaluateMacro(expression) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
ValueError: ('unexpected result from macro evaluation.', ...)
>>> del output[:]
>>> zc.evaluateMacro(expression) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
ValueError: ('unexpected result from macro evaluation.', ...)
>>> output = None
>>> zc.evaluateMacro(expression) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
ValueError: ('unexpected result from macro evaluation.', ...)
"""
macro = removeSecurityProxy(Context.evaluateMacro(self, expr))
# we'll do some basic checks that it is the sort of thing we expect
problem = False
try:
problem = macro[0][0] != 'version' or macro[1][0] != 'mode'
except (TypeError, IndexError):
problem = True
if problem:
raise ValueError('unexpected result from macro evaluation.', macro)
return macro
def setContext(self, name, value):
# Hook to allow subclasses to do things like adding security proxies
Context.setContext(self, name, ProxyFactory(value))
class TrustedZopeContext(ZopeContextBase):
"""Evaluation context for trusted programs."""
class AdapterNamespaces(object):
"""Simulate tales function namespaces with adapter lookup.
When we are asked for a namespace, we return an object that
actually computes an adapter when called:
To demonstrate this, we need to register an adapter:
>>> from zope.component.testing import setUp, tearDown
>>> setUp()
>>> from zope.component import provideAdapter
>>> def adapter1(ob):
... return 1
>>> adapter1.__component_adapts__ = (None,)
>>> provideAdapter(adapter1, None, IPathAdapter, 'a1')
Now, with this adapter in place, we can try out the namespaces:
>>> ob = object()
>>> namespaces = AdapterNamespaces()
>>> namespace = namespaces['a1']
>>> namespace(ob)
1
>>> namespace = namespaces['a2']
>>> namespace(ob)
Traceback (most recent call last):
...
KeyError: 'a2'
Cleanup:
>>> tearDown()
"""
def __init__(self):
self.namespaces = {}
def __getitem__(self, name):
namespace = self.namespaces.get(name)
if namespace is None:
def namespace(object):
try:
return component.getAdapter(object, IPathAdapter, name)
except ComponentLookupError:
raise KeyError(name)
self.namespaces[name] = namespace
return namespace
class ZopeBaseEngine(ExpressionEngine):
_create_context = ZopeContext
def __init__(self):
ExpressionEngine.__init__(self)
self.namespaces = AdapterNamespaces()
def getContext(self, __namespace=None, **namespace):
if __namespace:
if namespace:
namespace.update(__namespace)
else:
namespace = __namespace
context = self._create_context(self, namespace)
# Put request into context so path traversal can find it
if 'request' in namespace:
context.request = namespace['request']
# Put context into context so path traversal can find it
if 'context' in namespace:
context.context = namespace['context']
return context
class ZopeEngine(ZopeBaseEngine):
"""Untrusted expression engine.
This engine does not allow modules to be imported; only modules
already available may be accessed::
>>> modname = 'zope.pagetemplate.tests.trusted'
>>> engine = _Engine()
>>> context = engine.getContext(engine.getBaseNames())
>>> modname in sys.modules
False
>>> context.evaluate('modules/' + modname)
Traceback (most recent call last):
...
KeyError: 'zope.pagetemplate.tests.trusted'
(The use of ``KeyError`` is an unfortunate implementation detail; I
think this should be a ``TraversalError``.)
Modules which have already been imported by trusted code are
available, wrapped in security proxies::
>>> m = context.evaluate('modules/sys')
>>> m.__name__
'sys'
>>> m._getframe
Traceback (most recent call last):
...
ForbiddenAttribute: ('_getframe', <module 'sys' (built-in)>)
The results of Python expressions evaluated by this engine are
wrapped in security proxies::
>>> r = context.evaluate('python: {12: object()}.values')
>>> type(r)
<type 'zope.security._proxy._Proxy'>
>>> r = context.evaluate('python: {12: object()}.values()[0].__class__')
>>> type(r)
<type 'zope.security._proxy._Proxy'>
General path expressions provide objects that are wrapped in
security proxies as well::
>>> from zope.component.testing import setUp, tearDown
>>> from zope.security.checker import NamesChecker, defineChecker
>>> @implementer(ITraversable)
... class Container(dict):
... def traverse(self, name, further_path):
... return self[name]
>>> setUp()
>>> defineChecker(Container, NamesChecker(['traverse']))
>>> d = engine.getBaseNames()
>>> foo = Container()
>>> foo.__name__ = 'foo'
>>> d['foo'] = ProxyFactory(foo)
>>> foo['bar'] = bar = Container()
>>> bar.__name__ = 'bar'
>>> bar.__parent__ = foo
>>> bar['baz'] = baz = Container()
>>> baz.__name__ = 'baz'
>>> baz.__parent__ = bar
>>> context = engine.getContext(d)
>>> o1 = context.evaluate('foo/bar')
>>> o1.__name__
'bar'
>>> type(o1)
<type 'zope.security._proxy._Proxy'>
>>> o2 = context.evaluate('foo/bar/baz')
>>> o2.__name__
'baz'
>>> type(o2)
<type 'zope.security._proxy._Proxy'>
>>> o3 = o2.__parent__
>>> type(o3)
<type 'zope.security._proxy._Proxy'>
>>> o1 == o3
True
>>> o1 is o2
False
Note that this engine special-cases dicts during path traversal:
it traverses only to their items, but not to their attributes
(e.g. methods on dicts), because of performance reasons:
>>> d = engine.getBaseNames()
>>> d['adict'] = {'items': 123}
>>> d['anotherdict'] = {}
>>> context = engine.getContext(d)
>>> context.evaluate('adict/items')
123
>>> context.evaluate('anotherdict/keys')
Traceback (most recent call last):
...
KeyError: 'keys'
>>> tearDown()
"""
def getFunctionNamespace(self, namespacename):
""" Returns the function namespace """
return ProxyFactory(
super(ZopeEngine, self).getFunctionNamespace(namespacename))
class TrustedZopeEngine(ZopeBaseEngine):
"""Trusted expression engine.
This engine allows modules to be imported::
>>> modname = 'zope.pagetemplate.tests.trusted'
>>> engine = _TrustedEngine()
>>> context = engine.getContext(engine.getBaseNames())
>>> modname in sys.modules
False
>>> m = context.evaluate('modules/' + modname)
>>> m.__name__ == modname
True
>>> modname in sys.modules
True
Since this is trusted code, we can look at whatever is in the
module, not just __name__ or what's declared in a security
assertion::
>>> m.x
42
Clean up after ourselves::
>>> del sys.modules[modname]
"""
_create_context = TrustedZopeContext
@implementer(ITraversable)
class TraversableModuleImporter(SimpleModuleImporter):
def traverse(self, name, further_path):
try:
return self[name]
except KeyError:
raise TraversalError(self, name)
def _Engine(engine=None):
if engine is None:
engine = ZopeEngine()
engine = _create_base_engine(engine, ZopePathExpr)
engine.registerType('python', ZopePythonExpr)
# Using a proxy around sys.modules allows page templates to use
# modules for which security declarations have been made, but
# disallows execution of any import-time code for modules, which
# should not be allowed to happen during rendering.
engine.registerBaseName('modules', ProxyFactory(sys.modules))
return engine
def _TrustedEngine(engine=None):
if engine is None:
engine = TrustedZopeEngine()
engine = _create_base_engine(engine, TrustedZopePathExpr)
engine.registerType('python', PythonExpr)
engine.registerBaseName('modules', TraversableModuleImporter())
return engine
def _create_base_engine(engine, pathtype):
for pt in pathtype._default_type_names:
engine.registerType(pt, pathtype)
engine.registerType('string', StringExpr)
engine.registerType('not', NotExpr)
engine.registerType('defer', DeferExpr)
return engine
Engine = _Engine()
TrustedEngine = _TrustedEngine()
class AppPT(object):
def pt_getEngine(self):
return Engine
class TrustedAppPT(object):
def pt_getEngine(self):
return TrustedEngine
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