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
|
=========================
zope.security.decorator
=========================
.. automodule:: zope.security.decorator
API Examples
============
.. currentmodule:: zope.security.decorator
.. testsetup::
from zope.component.testing import setUp
setUp()
To illustrate, we'll create a class that will be proxied:
.. doctest::
>>> class Foo(object):
... a = 'a'
and a class to proxy it that uses a decorated security checker:
.. doctest::
>>> from zope.security.decorator import DecoratedSecurityCheckerDescriptor
>>> from zope.proxy import ProxyBase
>>> class Wrapper(ProxyBase):
... b = 'b'
... __Security_checker__ = DecoratedSecurityCheckerDescriptor()
Next we'll create and register a checker for ``Foo``:
.. doctest::
>>> from zope.security.checker import NamesChecker, defineChecker
>>> fooChecker = NamesChecker(['a'])
>>> defineChecker(Foo, fooChecker)
along with a checker for ``Wrapper``:
.. doctest::
>>> wrapperChecker = NamesChecker(['b'])
>>> defineChecker(Wrapper, wrapperChecker)
Using :func:`zope.security.checker.selectChecker`, we can confirm that
a ``Foo`` object uses ``fooChecker``:
.. doctest::
>>> from zope.security.checker import selectChecker
>>> from zope.security.interfaces import ForbiddenAttribute
>>> foo = Foo()
>>> selectChecker(foo) is fooChecker
True
>>> fooChecker.check(foo, 'a')
>>> try:
... fooChecker.check(foo, 'b') # doctest: +ELLIPSIS
... except ForbiddenAttribute as e:
... e
ForbiddenAttribute('b', <...Foo object ...>)
and that a ``Wrapper`` object uses ``wrappeChecker``:
.. doctest::
>>> wrapper = Wrapper(foo)
>>> selectChecker(wrapper) is wrapperChecker
True
>>> wrapperChecker.check(wrapper, 'b')
>>> try:
... wrapperChecker.check(wrapper, 'a') # doctest: +ELLIPSIS
... except ForbiddenAttribute as e:
... e
ForbiddenAttribute('a', <...Foo object ...>)
(Note that the object description says `Foo` because the object is a
proxy and generally looks and acts like the object it's proxying.)
When we access wrapper's ``__Security_checker__`` attribute, we invoke
the decorated security checker descriptor. The decorator's job is to make
sure checkers from both objects are used when available. In this case,
because both objects have checkers, we get a combined checker:
.. doctest::
>>> from zope.security.checker import CombinedChecker
>>> checker = wrapper.__Security_checker__
>>> type(checker)
<class 'zope.security.checker.CombinedChecker'>
>>> checker.check(wrapper, 'a')
>>> checker.check(wrapper, 'b')
The decorator checker will work even with security proxied objects. To
illustrate, we'll proxify ``foo``:
.. doctest::
>>> from zope.security.proxy import ProxyFactory
>>> secure_foo = ProxyFactory(foo)
>>> secure_foo.a
'a'
>>> try:
... secure_foo.b # doctest: +ELLIPSIS
... except ForbiddenAttribute as e:
... e
ForbiddenAttribute('b', <...Foo object ...>)
when we wrap the secured ``foo``:
.. doctest::
>>> wrapper = Wrapper(secure_foo)
we still get a combined checker:
.. doctest::
>>> checker = wrapper.__Security_checker__
>>> type(checker)
<class 'zope.security.checker.CombinedChecker'>
>>> checker.check(wrapper, 'a')
>>> checker.check(wrapper, 'b')
The decorator checker has three other scenarios:
- the wrapper has a checker but the proxied object doesn't
- the proxied object has a checker but the wrapper doesn't
- neither the wrapper nor the proxied object have checkers
When the wrapper has a checker but the proxied object doesn't:
.. doctest::
>>> from zope.security.checker import NoProxy, _checkers
>>> del _checkers[Foo]
>>> defineChecker(Foo, NoProxy)
>>> selectChecker(foo) is None
True
>>> selectChecker(wrapper) is wrapperChecker
True
the decorator uses only the wrapper checker:
.. doctest::
>>> wrapper = Wrapper(foo)
>>> wrapper.__Security_checker__ is wrapperChecker
True
When the proxied object has a checker but the wrapper doesn't:
.. doctest::
>>> del _checkers[Wrapper]
>>> defineChecker(Wrapper, NoProxy)
>>> selectChecker(wrapper) is None
True
>>> del _checkers[Foo]
>>> defineChecker(Foo, fooChecker)
>>> selectChecker(foo) is fooChecker
True
the decorator uses only the proxied object checker:
.. doctest::
>>> wrapper.__Security_checker__ is fooChecker
True
Finally, if neither the wrapper not the proxied have checkers:
.. doctest::
>>> del _checkers[Foo]
>>> defineChecker(Foo, NoProxy)
>>> selectChecker(foo) is None
True
>>> selectChecker(wrapper) is None
True
the decorator doesn't have a checker:
.. doctest::
>>> wrapper.__Security_checker__
Traceback (most recent call last):
...
AttributeError: 'Foo' has no attribute '__Security_checker__'
``__Security_checker__`` cannot be None, otherwise Checker.proxy blows
up:
>>> checker.proxy(wrapper) is wrapper
True
.. testcleanup::
from zope.component.testing import tearDown
tearDown()
|
