This file is indexed.

/usr/share/pyshared/zope/security/checker.py is in python-zope.security 3.8.3-2ubuntu1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
##############################################################################
#
# Copyright (c) 2003 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.
#
##############################################################################
"""Security Checkers

You can set the environment variable ZOPE_WATCH_CHECKERS to get additional
security checker debugging output on the standard error.

Setting ZOPE_WATCH_CHECKERS to 1 will display messages about unauthorized or
forbidden attribute access.  Setting it to a larger number will also display
messages about granted attribute access.

Note that the ZOPE_WATCH_CHECKERS mechanism will eventually be
replaced with a more general security auditing mechanism.
"""
import os
import sys
import types
import datetime
import decimal
import weakref

import zope.interface.interface
import zope.interface.interfaces
import zope.interface.declarations
from zope.i18nmessageid import Message
from zope.interface import directlyProvides, Interface, implements
from zope.interface.interfaces import IInterface, IDeclaration

from zope.security.interfaces import IChecker, INameBasedChecker
from zope.security.interfaces import ISecurityProxyFactory
from zope.security.interfaces import Unauthorized, ForbiddenAttribute
from zope.security._definitions import thread_local
from zope.security._proxy import _Proxy as Proxy, getChecker

try:
    from zope.exceptions import DuplicationError
except ImportError:
    class DuplicationError(Exception):
        """A duplicate registration was attempted"""

if os.environ.get('ZOPE_WATCH_CHECKERS'):
    try:
        WATCH_CHECKERS = int(os.environ.get('ZOPE_WATCH_CHECKERS'))
    except ValueError:
        WATCH_CHECKERS = 1
else:
    WATCH_CHECKERS = 0


def ProxyFactory(object, checker=None):
    """Factory function that creates a proxy for an object

    The proxy checker is looked up if not provided.
    """
    if type(object) is Proxy:
        if checker is None or checker is getChecker(object):
            return object
        else:
            # We have a proxy, but someone asked us to change its checker.
            # Let's raise an exception.
            #
            # Other reasonable actions would be to either keep the existing
            # proxy, or to create a new one with the given checker.
            # The latter might be a security hole though, if untrusted code
            # can call ProxyFactory.
            raise TypeError("Tried to use ProxyFactory to change a Proxy's"
                            " checker.")
    if checker is None:
        checker = getattr(object, '__Security_checker__', None)

        if checker is None:
            checker = selectChecker(object)
            if checker is None:
                return object

    return Proxy(object, checker)

directlyProvides(ProxyFactory, ISecurityProxyFactory)

def canWrite(obj, name):
    """Check whether the interaction may write an attribute named name on obj.

    Convenience method.  Rather than using checkPermission in high level code,
    use canWrite and canAccess to avoid binding code to permissions.
    """
    obj = ProxyFactory(obj)
    checker = getChecker(obj)
    try:
        checker.check_setattr(obj, name)
    except Unauthorized:
        return False
    except ForbiddenAttribute:
        # we are going to be a bit DWIM-y here: see
        # http://www.zope.org/Collectors/Zope3-dev/506

        # generally, if the check is ForbiddenAttribute we want it to be
        # raised: it probably indicates a programming or configuration error.
        # However, we special case a write ForbiddenAttribute when one can
        # actually read the attribute: this represents a reasonable
        # configuration of a readonly attribute, and returning False (meaning
        # "no, you can't write it") is arguably more useful than raising the
        # exception.
        try:
            checker.check_getattr(obj, name)
            # we'll let *this* ForbiddenAttribute fall through, if any.  It
            # means that both read and write are forbidden.
        except Unauthorized:
            pass
        return False
    # all other exceptions, other than Unauthorized and ForbiddenAttribute,
    # should be passed through uncaught, as they indicate programmer error
    return True

def canAccess(obj, name):
    """Check whether the interaction may access an attribute named name on obj.

    Convenience method.  Rather than using checkPermission in high level code,
    use canWrite and canAccess to avoid binding code to permissions.
    """
    # access attributes and methods, including, in the current checker
    # implementation, special names like __getitem__
    obj = ProxyFactory(obj)
    checker = getChecker(obj)
    try:
        checker.check_getattr(obj, name)
    except Unauthorized:
        return False
    # if it is Forbidden (or anything else), let it be raised: it probably
    # indicates a programming or configuration error
    return True

class Checker(object):
    implements(INameBasedChecker)

    def __init__(self, get_permissions, set_permissions=None):
        """Create a checker

        A dictionary must be provided for computing permissions for
        names. The dictionary get will be called with attribute names
        and must return a permission id, None, or the special marker,
        CheckerPublic. If None is returned, then access to the name is
        forbidden. If CheckerPublic is returned, then access will be
        granted without checking a permission.

        An optional setattr dictionary may be provided for checking
        set attribute access.

        """
        assert isinstance(get_permissions, dict)
        self.get_permissions = get_permissions
        if set_permissions is not None:
            assert isinstance(set_permissions, dict)
        self.set_permissions = set_permissions

    def permission_id(self, name):
        'See INameBasedChecker'
        return self.get_permissions.get(name)

    def setattr_permission_id(self, name):
        'See INameBasedChecker'
        if self.set_permissions:
            return self.set_permissions.get(name)

    def check_getattr(self, object, name):
        'See IChecker'
        self.check(object, name)

    def check_setattr(self, object, name):
        'See IChecker'
        if self.set_permissions:
            permission = self.set_permissions.get(name)
        else:
            permission = None

        if permission is not None:
            if permission is CheckerPublic:
                return # Public
            if thread_local.interaction.checkPermission(permission, object):
                return # allowed
            else:
                __traceback_supplement__ = (TracebackSupplement, object)
                raise Unauthorized(object, name, permission)

        __traceback_supplement__ = (TracebackSupplement, object)
        raise ForbiddenAttribute(name, object)

    def check(self, object, name):
        'See IChecker'
        permission = self.get_permissions.get(name)
        if permission is not None:
            if permission is CheckerPublic:
                return # Public
            if thread_local.interaction.checkPermission(permission, object):
                return
            else:
                __traceback_supplement__ = (TracebackSupplement, object)
                raise Unauthorized(object, name, permission)
        elif name in _available_by_default:
            return

        if name != '__iter__' or hasattr(object, name):
            __traceback_supplement__ = (TracebackSupplement, object)
            raise ForbiddenAttribute(name, object)

    def proxy(self, value):
        'See IChecker'
        if type(value) is Proxy:
            return value
        checker = getattr(value, '__Security_checker__', None)
        if checker is None:
            checker = selectChecker(value)
            if checker is None:
                return value

        return Proxy(value, checker)



# Helper class for __traceback_supplement__
class TracebackSupplement(object):

    def __init__(self, obj):
        self.obj = obj

    def getInfo(self):
        result = []
        try:
            cls = self.obj.__class__
            if hasattr(cls, "__module__"):
                s = "%s.%s" % (cls.__module__, cls.__name__)
            else:
                s = str(cls.__name__)
            result.append("   - class: " + s)
        except:
            pass
        try:
            cls = type(self.obj)
            if hasattr(cls, "__module__"):
                s = "%s.%s" % (cls.__module__, cls.__name__)
            else:
                s = str(cls.__name__)
            result.append("   - type: " + s)
        except:
            pass
        return "\n".join(result)


class Global(object):
    """A global object that behaves like a string.

    We want this to behave as a global, meaning it's pickled
    by name, rather than value. We need to arrange that it has a suitable
    __reduce__.
    """

    def __init__(self, name, module=None):
        if module is None:
            module = sys._getframe(1).f_locals['__name__']

        self.__name__ = name
        self.__module__ = module

    def __reduce__(self):
        return self.__name__

    def __repr__(self):
        return "%s(%s,%s)" % (self.__class__.__name__,
                              self.__name__, self.__module__)

# Marker for public attributes
CheckerPublic = Global('CheckerPublic')

# Now we wrap it in a security proxy so that it retains it's
# identity when it needs to be security proxied.
d={}
CheckerPublic = Proxy(CheckerPublic, Checker(d))
d['__reduce__'] = CheckerPublic
del d

# TODO: It's a bit scary above that we can pickle a proxy if access is
# granted to __reduce__. We might want to bother to prevent this in
# general and only allow it in this specific case.

def NamesChecker(names=(), permission_id=CheckerPublic, **__kw__):
    """Return a checker that grants access to a set of names.

    A sequence of names is given as the first argument. If a second
    argument, permission_id, is given, it is the permission required
    to access the names.  Additional names and permission ids can be
    supplied as keyword arguments.
    """

    data = {}
    data.update(__kw__)
    for name in names:
        if data.get(name, permission_id) is not permission_id:
            raise DuplicationError(name)
        data[name] = permission_id

    return Checker(data)

def InterfaceChecker(interface, permission_id=CheckerPublic, **__kw__):
    return NamesChecker(interface.names(all=True), permission_id, **__kw__)

def MultiChecker(specs):
    """Create a checker from a sequence of specifications

    A specification is:

    - A two-tuple with:

      o a sequence of names or an interface

      o a permission id

      All the names in the sequence of names or the interface are
      protected by the permission.

    - A dictionoid (having an items method), with items that are
      name/permission-id pairs.
    """
    data = {}

    for spec in specs:
        if type(spec) is tuple:
            names, permission_id = spec
            if IInterface.providedBy(names):
                names = names.names(all=True)
            for name in names:
                if data.get(name, permission_id) is not permission_id:
                    raise DuplicationError(name)
                data[name] = permission_id
        else:
            for name, permission_id in spec.items():
                if data.get(name, permission_id) is not permission_id:
                    raise DuplicationError(name)
                data[name] = permission_id

    return Checker(data)

def selectChecker(object):
    """Get a checker for the given object

    The appropriate checker is returned or None is returned. If the
    return value is None, then object should not be wrapped in a proxy.
    """

    # We need to be careful here. We might have a proxy, in which case
    # we can't use the type.  OTOH, we might not be able to use the
    # __class__ either, since not everything has one.

    # TODO: we really need formal proxy introspection

    #if type(object) is Proxy:
    #    # Is this already a security proxy?
    #    return None

    checker = _getChecker(type(object), _defaultChecker)

    #checker = _getChecker(getattr(object, '__class__', type(object)),
    #                      _defaultChecker)

    if checker is NoProxy:
        return None

    while not isinstance(checker, Checker):
        checker = checker(object)
        if checker is NoProxy or checker is None:
            return None

    return checker

def getCheckerForInstancesOf(class_):
    return _checkers.get(class_)

def defineChecker(type_, checker):
    """Define a checker for a given type of object

    The checker can be a Checker, or a function that, when called with
    an object, returns a Checker.
    """
    if not isinstance(type_, (type, types.ClassType, types.ModuleType)):
        raise TypeError(
                'type_ must be a type, class or module, not a %s' % type_)
    if type_ in _checkers:
        raise DuplicationError(type_)
    _checkers[type_] = checker

def undefineChecker(type_):
    del _checkers[type_]

NoProxy = object()

# _checkers is a mapping.
#
#  - Keys are types
#
#  - Values are
#
#    o None => rock
#    o a Checker
#    o a function returning None or a Checker
#
_checkers = {}

_defaultChecker = Checker({})
_available_by_default = []

# Get optimized versions
try:
    import zope.security._zope_security_checker
except ImportError:
    pass
else:
    from zope.security._zope_security_checker import _checkers, selectChecker
    from zope.security._zope_security_checker import NoProxy, Checker
    from zope.security._zope_security_checker import _defaultChecker
    from zope.security._zope_security_checker import _available_by_default
    zope.interface.classImplements(Checker, INameBasedChecker)


_getChecker = _checkers.get

class CombinedChecker(Checker):
    """A checker that combines two other checkers in a logical-or fashion.

    The following table describes the result of a combined checker in detail.

    checker1           checker2           CombinedChecker(checker1, checker2)
    ------------------ ------------------ -----------------------------------
    ok                 anything           ok (checker2 is never called)
    Unauthorized       ok                 ok
    Unauthorized       Unauthorized       Unauthorized
    Unauthorized       ForbiddenAttribute Unauthorized
    ForbiddenAttribute ok                 ok
    ForbiddenAttribute Unauthorized       Unauthorized
    ForbiddenAttribute ForbiddenAttribute ForbiddenAttribute
    ------------------ ------------------ -----------------------------------
    """
    implements(IChecker)

    def __init__(self, checker1, checker2):
        """Create a combined checker."""
        Checker.__init__(self,
                         checker1.get_permissions,
                         checker1.set_permissions)
        self._checker2 = checker2

    def check(self, object, name):
        'See IChecker'
        try:
            Checker.check(self, object, name)
        except ForbiddenAttribute:
            self._checker2.check(object, name)
        except Unauthorized, unauthorized_exception:
            try: self._checker2.check(object, name)
            except ForbiddenAttribute:
                raise unauthorized_exception

    check_getattr = __setitem__ = check

    def check_setattr(self, object, name):
        'See IChecker'
        try:
            Checker.check_setattr(self, object, name)
        except ForbiddenAttribute:
            self._checker2.check_setattr(object, name)
        except Unauthorized, unauthorized_exception:
            try: self._checker2.check_setattr(object, name)
            except ForbiddenAttribute:
                raise unauthorized_exception

class CheckerLoggingMixin(object):
    """Debugging mixin for checkers.

    Prints verbose debugging information about every performed check to
    sys.stderr.

    If verbosity is set to 1, only displays Unauthorized and Forbidden messages.
    If verbosity is set to a larger number, displays all messages.
    """

    verbosity = 1

    def check(self, object, name):
        try:
            super(CheckerLoggingMixin, self).check(object, name)
            if self.verbosity > 1:
                if name in _available_by_default:
                    print >> sys.stderr, (
                        '[CHK] + Always available: %s on %r' % (name, object))
                else:
                    print >> sys.stderr, (
                        '[CHK] + Granted: %s on %r' % (name, object))
        except Unauthorized:
            print >> sys.stderr, (
                '[CHK] - Unauthorized: %s on %r' % (name, object))
            raise
        except ForbiddenAttribute:
            print >> sys.stderr, (
                '[CHK] - Forbidden: %s on %r' % (name, object))
            raise

    def check_getattr(self, object, name):
        try:
            super(CheckerLoggingMixin, self).check(object, name)
            if self.verbosity > 1:
                if name in _available_by_default:
                    print >> sys.stderr, (
                        '[CHK] + Always available getattr: %s on %r'
                        % (name, object))
                else:
                    print >> sys.stderr, (
                        '[CHK] + Granted getattr: %s on %r'
                        % (name, object))
        except Unauthorized:
            print >> sys.stderr, (
                '[CHK] - Unauthorized getattr: %s on %r' % (name, object))
            raise
        except ForbiddenAttribute:
            print >> sys.stderr, (
                '[CHK] - Forbidden getattr: %s on %r' % (name, object))
            raise

    def check_setattr(self, object, name):
        try:
            super(CheckerLoggingMixin, self).check_setattr(object, name)
            if self.verbosity > 1:
                print >> sys.stderr, (
                    '[CHK] + Granted setattr: %s on %r' % (name, object))
        except Unauthorized:
            print >> sys.stderr, (
                '[CHK] - Unauthorized setattr: %s on %r' % (name, object))
            raise
        except ForbiddenAttribute:
            print >> sys.stderr, (
                '[CHK] - Forbidden setattr: %s on %r' % (name, object))
            raise


if WATCH_CHECKERS:
    class Checker(CheckerLoggingMixin, Checker):
        verbosity = WATCH_CHECKERS
    class CombinedChecker(CheckerLoggingMixin, CombinedChecker):
        verbosity = WATCH_CHECKERS

def _instanceChecker(inst):
    return _checkers.get(inst.__class__, _defaultChecker)

def moduleChecker(module):
    return _checkers.get(module)


_available_by_default[:] = ['__lt__', '__le__', '__eq__',
                            '__gt__', '__ge__', '__ne__',
                            '__hash__', '__nonzero__',
                            '__class__', '__providedBy__', '__implements__',
                            '__repr__', '__conform__',
                            '__name__', '__parent__',
                            ]

_callableChecker = NamesChecker(['__str__', '__name__', '__call__'])
_typeChecker = NamesChecker(
    ['__str__', '__name__', '__module__', '__bases__', '__mro__',
     '__implemented__'])
_namedChecker = NamesChecker(['__name__'])

_iteratorChecker = NamesChecker(['next', '__iter__'])

_setChecker = NamesChecker(['__iter__', '__len__', '__str__', '__contains__',
                            'copy', 'difference', 'intersection', 'issubset',
                            'issuperset', 'symmetric_difference', 'union',
                            '__and__', '__or__', '__sub__', '__xor__',
                            '__rand__', '__ror__', '__rsub__', '__rxor__',
                            '__eq__', '__ne__', '__lt__', '__gt__',
                            '__le__', '__ge__'])

class BasicTypes(dict):
    """Basic Types Dictionary

    Make sure that checkers are really updated, when a new type is added.
    """
    def __setitem__(self, name, value):
        super(BasicTypes.__class__, self).__setitem__(name, value)
        _checkers[name] = value

    def __delitem__(self, name):
        super(BasicTypes.__class__, self).__delitem__(name)
        del _checkers[name]

    def clear(self):
        # Make sure you cannot clear the values
        raise NotImplementedError

    def update(self, d):
        super(BasicTypes.__class__, self).update(d)
        _checkers.update(d)

_basic_types = {
    object: NoProxy,
    int: NoProxy,
    float: NoProxy,
    long: NoProxy,
    complex: NoProxy,
    types.NoneType: NoProxy,
    str: NoProxy,
    unicode: NoProxy,
    Message: NoProxy, # Messages are immutable, so it's okay
    bool: NoProxy,
    datetime.timedelta: NoProxy,
    datetime.datetime: NoProxy,
    datetime.date: NoProxy,
    datetime.time: NoProxy,
    datetime.tzinfo: NoProxy,
}
try:
    import pytz
except ImportError:
    pass
else:
    _basic_types[type(pytz.UTC)] = NoProxy

BasicTypes = BasicTypes(_basic_types)
del _basic_types

# Available for tests. Located here so it can be kept in sync with BasicTypes.
BasicTypes_examples = {
    object: object(),
    int: 65536,
    float: -1.4142,
    long: 65536l,
    complex: -1.4142j,
    types.NoneType: None,
    str: 'abc',
    unicode: u'uabc',
    bool: True,
    datetime.timedelta: datetime.timedelta(3),
    datetime.datetime: datetime.datetime(2003, 1, 1),
    datetime.date: datetime.date(2003, 1, 1),
    datetime.time: datetime.time(23, 58),
    Message: Message('message', domain='hello')
}


class _Sequence(object):
    def __len__(self): return 0
    def __getitem__(self, i): raise IndexError

_Declaration_checker = InterfaceChecker(
    IDeclaration,
    _implied=CheckerPublic,
    subscribe=CheckerPublic,
    unsubscribe=CheckerPublic,
    __call__=CheckerPublic,
    )

def f():
    yield f


_default_checkers = {
    dict: NamesChecker(['__getitem__', '__len__', '__iter__',
                        'get', 'has_key', 'copy', '__str__', 'keys',
                        'values', 'items', 'iterkeys', 'iteritems',
                        'itervalues', '__contains__']),
    list: NamesChecker(['__getitem__', '__getslice__', '__len__', '__iter__',
                        '__contains__', 'index', 'count', '__str__',
                        '__add__', '__radd__', ]),
    set: _setChecker,
    frozenset: _setChecker,
    decimal.Decimal: NamesChecker(['__nonzero__', '__cmp__', '__eq__',
                                   '__ne__', 'compare', '__hash__',
                                   'as_tuple', '__str__', 'to_eng_string',
                                   '__neg__', '__pos__', '__abs__',
                                   '__add__', '__radd__', '__sub__',
                                   '__rsub__', '__mul__', '__rmul__',
                                   '__div__', '__rdiv__', '__rtruediv__',
                                   '__divmod__', '__rdivmod__', '__mod__',
                                   '__rmod__', 'remainder_near',
                                   '__floordiv__', '__rfloordiv__',
                                   '__float__', '__int__', '__long__',
                                   '__pow__', '__rpow__', 'normalize',
                                   'quantize', 'same_quantum', 'to_integral',
                                   'sqrt', 'max', 'min', 'adjusted']),

    # YAGNI: () a rock
    tuple: NamesChecker(['__getitem__', '__getslice__', '__add__', '__radd__',
                         '__contains__', '__len__', '__iter__',
                         '__str__']),
    types.InstanceType: _instanceChecker,
    Proxy: NoProxy,
    type(weakref.ref(_Sequence())): NamesChecker(['__call__']),
    types.ClassType: _typeChecker,
    types.FunctionType: _callableChecker,
    types.MethodType: _callableChecker,
    types.BuiltinFunctionType: _callableChecker,
    types.BuiltinMethodType: _callableChecker,
    type(().__getslice__): _callableChecker, # slot description
    type: _typeChecker,
    types.ModuleType: lambda module: _checkers.get(module, _namedChecker),
    type(iter([])): _iteratorChecker, # Same types in Python 2.2.1,
    type(iter(())): _iteratorChecker, # different in Python 2.3.
    type(iter({})): _iteratorChecker,
    type(iter(set())): _iteratorChecker,
    type({}.iteritems()): _iteratorChecker,
    type({}.iterkeys()): _iteratorChecker,
    type({}.itervalues()): _iteratorChecker,
    type(iter(_Sequence())): _iteratorChecker,
    type(f()): _iteratorChecker,
    type(Interface): InterfaceChecker(
        IInterface,
        __str__=CheckerPublic, _implied=CheckerPublic, subscribe=CheckerPublic,
        ),
    zope.interface.interface.Method: InterfaceChecker(
                                        zope.interface.interfaces.IMethod),
    zope.interface.declarations.ProvidesClass: _Declaration_checker,
    zope.interface.declarations.ClassProvides: _Declaration_checker,
    zope.interface.declarations.Implements: _Declaration_checker,
    zope.interface.declarations.Declaration: _Declaration_checker,
}

if sys.version_info < (2, 6):
    import sets
    _default_checkers[sets.Set] = _setChecker
    _default_checkers[sets.ImmutableSet] = _setChecker

if sys.version_info >= (2, 6):
    import abc
    _default_checkers[abc.ABCMeta] = _typeChecker


def _clear():
    _checkers.clear()
    _checkers.update(_default_checkers)
    _checkers.update(BasicTypes)

_clear()

try:
    from zope.testing.cleanup import addCleanUp
except ImportError:
    pass
else:
    addCleanUp(_clear)