# -*- coding: utf-8 -*-
"""
jinja2.sandbox
~~~~~~~~~~~~~~
Adds a sandbox layer to Jinja as it was the default behavior in the old
Jinja 1 releases. This sandbox is slightly different from Jinja 1 as the
default behavior is easier to use.
The behavior can be changed by subclassing the environment.
:copyright: (c) 2010 by the Jinja Team.
:license: BSD.
"""
import types
import operator
from jinja2.environment import Environment
from jinja2.exceptions import SecurityError
from jinja2._compat import string_types, PY2
#: maximum number of items a range may produce
MAX_RANGE = 100000
#: attributes of function objects that are considered unsafe.
if PY2:
UNSAFE_FUNCTION_ATTRIBUTES = set(['func_closure', 'func_code', 'func_dict',
'func_defaults', 'func_globals'])
else:
# On versions > python 2 the special attributes on functions are gone,
# but they remain on methods and generators for whatever reason.
UNSAFE_FUNCTION_ATTRIBUTES = set()
#: unsafe method attributes. function attributes are unsafe for methods too
UNSAFE_METHOD_ATTRIBUTES = set(['im_class', 'im_func', 'im_self'])
#: unsafe generator attirbutes.
UNSAFE_GENERATOR_ATTRIBUTES = set(['gi_frame', 'gi_code'])
import warnings
# make sure we don't warn in python 2.6 about stuff we don't care about
warnings.filterwarnings('ignore', 'the sets module', DeprecationWarning,
module='jinja2.sandbox')
from collections import deque
_mutable_set_types = (set,)
_mutable_mapping_types = (dict,)
_mutable_sequence_types = (list,)
# on python 2.x we can register the user collection types
try:
from UserDict import UserDict, DictMixin
from UserList import UserList
_mutable_mapping_types += (UserDict, DictMixin)
_mutable_set_types += (UserList,)
except ImportError:
pass
# if sets is still available, register the mutable set from there as well
try:
from sets import Set
_mutable_set_types += (Set,)
except ImportError:
pass
#: register Python 2.6 abstract base classes
try:
from collections import MutableSet, MutableMapping, MutableSequence
_mutable_set_types += (MutableSet,)
_mutable_mapping_types += (MutableMapping,)
_mutable_sequence_types += (MutableSequence,)
except ImportError:
pass
_mutable_spec = (
(_mutable_set_types, frozenset([
'add', 'clear', 'difference_update', 'discard', 'pop', 'remove',
'symmetric_difference_update', 'update'
])),
(_mutable_mapping_types, frozenset([
'clear', 'pop', 'popitem', 'setdefault', 'update'
])),
(_mutable_sequence_types, frozenset([
'append', 'reverse', 'insert', 'sort', 'extend', 'remove'
])),
(deque, frozenset([
'append', 'appendleft', 'clear', 'extend', 'extendleft', 'pop',
'popleft', 'remove', 'rotate'
]))
)
[docs]def safe_range(*args):
"""A range that can't generate ranges with a length of more than
MAX_RANGE items.
"""
rng = range(*args)
if len(rng) > MAX_RANGE:
raise OverflowError('range too big, maximum size for range is %d' %
MAX_RANGE)
return rng
[docs]def unsafe(f):
"""Marks a function or method as unsafe.
::
@unsafe
def delete(self):
pass
"""
f.unsafe_callable = True
return f
[docs]def is_internal_attribute(obj, attr):
"""Test if the attribute given is an internal python attribute. For
example this function returns `True` for the `func_code` attribute of
python objects. This is useful if the environment method
:meth:`~SandboxedEnvironment.is_safe_attribute` is overridden.
>>> from jinja2.sandbox import is_internal_attribute
>>> is_internal_attribute(str, "mro")
True
>>> is_internal_attribute(str, "upper")
False
"""
if isinstance(obj, types.FunctionType):
if attr in UNSAFE_FUNCTION_ATTRIBUTES:
return True
elif isinstance(obj, types.MethodType):
if attr in UNSAFE_FUNCTION_ATTRIBUTES or \
attr in UNSAFE_METHOD_ATTRIBUTES:
return True
elif isinstance(obj, type):
if attr == 'mro':
return True
elif isinstance(obj, (types.CodeType, types.TracebackType, types.FrameType)):
return True
elif isinstance(obj, types.GeneratorType):
if attr in UNSAFE_GENERATOR_ATTRIBUTES:
return True
return attr.startswith('__')
[docs]def modifies_known_mutable(obj, attr):
"""This function checks if an attribute on a builtin mutable object
(list, dict, set or deque) would modify it if called. It also supports
the "user"-versions of the objects (`sets.Set`, `UserDict.*` etc.) and
with Python 2.6 onwards the abstract base classes `MutableSet`,
`MutableMapping`, and `MutableSequence`.
>>> modifies_known_mutable({}, "clear")
True
>>> modifies_known_mutable({}, "keys")
False
>>> modifies_known_mutable([], "append")
True
>>> modifies_known_mutable([], "index")
False
If called with an unsupported object (such as unicode) `False` is
returned.
>>> modifies_known_mutable("foo", "upper")
False
"""
for typespec, unsafe in _mutable_spec:
if isinstance(obj, typespec):
return attr in unsafe
return False
[docs]class SandboxedEnvironment(Environment):
"""The sandboxed environment. It works like the regular environment but
tells the compiler to generate sandboxed code. Additionally subclasses of
this environment may override the methods that tell the runtime what
attributes or functions are safe to access.
If the template tries to access insecure code a :exc:`SecurityError` is
raised. However also other exceptions may occour during the rendering so
the caller has to ensure that all exceptions are catched.
"""
sandboxed = True
#: default callback table for the binary operators. A copy of this is
#: available on each instance of a sandboxed environment as
#: :attr:`binop_table`
default_binop_table = {
'+': operator.add,
'-': operator.sub,
'*': operator.mul,
'/': operator.truediv,
'//': operator.floordiv,
'**': operator.pow,
'%': operator.mod
}
#: default callback table for the unary operators. A copy of this is
#: available on each instance of a sandboxed environment as
#: :attr:`unop_table`
default_unop_table = {
'+': operator.pos,
'-': operator.neg
}
#: a set of binary operators that should be intercepted. Each operator
#: that is added to this set (empty by default) is delegated to the
#: :meth:`call_binop` method that will perform the operator. The default
#: operator callback is specified by :attr:`binop_table`.
#:
#: The following binary operators are interceptable:
#: ``//``, ``%``, ``+``, ``*``, ``-``, ``/``, and ``**``
#:
#: The default operation form the operator table corresponds to the
#: builtin function. Intercepted calls are always slower than the native
#: operator call, so make sure only to intercept the ones you are
#: interested in.
#:
#: .. versionadded:: 2.6
intercepted_binops = frozenset()
#: a set of unary operators that should be intercepted. Each operator
#: that is added to this set (empty by default) is delegated to the
#: :meth:`call_unop` method that will perform the operator. The default
#: operator callback is specified by :attr:`unop_table`.
#:
#: The following unary operators are interceptable: ``+``, ``-``
#:
#: The default operation form the operator table corresponds to the
#: builtin function. Intercepted calls are always slower than the native
#: operator call, so make sure only to intercept the ones you are
#: interested in.
#:
#: .. versionadded:: 2.6
intercepted_unops = frozenset()
[docs] def intercept_unop(self, operator):
"""Called during template compilation with the name of a unary
operator to check if it should be intercepted at runtime. If this
method returns `True`, :meth:`call_unop` is excuted for this unary
operator. The default implementation of :meth:`call_unop` will use
the :attr:`unop_table` dictionary to perform the operator with the
same logic as the builtin one.
The following unary operators are interceptable: ``+`` and ``-``
Intercepted calls are always slower than the native operator call,
so make sure only to intercept the ones you are interested in.
.. versionadded:: 2.6
"""
return False
[docs] def __init__(self, *args, **kwargs):
Environment.__init__(self, *args, **kwargs)
self.globals['range'] = safe_range
self.binop_table = self.default_binop_table.copy()
self.unop_table = self.default_unop_table.copy()
[docs] def is_safe_attribute(self, obj, attr, value):
"""The sandboxed environment will call this method to check if the
attribute of an object is safe to access. Per default all attributes
starting with an underscore are considered private as well as the
special attributes of internal python objects as returned by the
:func:`is_internal_attribute` function.
"""
return not (attr.startswith('_') or is_internal_attribute(obj, attr))
[docs] def is_safe_callable(self, obj):
"""Check if an object is safely callable. Per default a function is
considered safe unless the `unsafe_callable` attribute exists and is
True. Override this method to alter the behavior, but this won't
affect the `unsafe` decorator from this module.
"""
return not (getattr(obj, 'unsafe_callable', False) or
getattr(obj, 'alters_data', False))
[docs] def call_binop(self, context, operator, left, right):
"""For intercepted binary operator calls (:meth:`intercepted_binops`)
this function is executed instead of the builtin operator. This can
be used to fine tune the behavior of certain operators.
.. versionadded:: 2.6
"""
return self.binop_table[operator](left, right)
[docs] def call_unop(self, context, operator, arg):
"""For intercepted unary operator calls (:meth:`intercepted_unops`)
this function is executed instead of the builtin operator. This can
be used to fine tune the behavior of certain operators.
.. versionadded:: 2.6
"""
return self.unop_table[operator](arg)
[docs] def getitem(self, obj, argument):
"""Subscribe an object from sandboxed code."""
try:
return obj[argument]
except (TypeError, LookupError):
if isinstance(argument, string_types):
try:
attr = str(argument)
except Exception:
pass
else:
try:
value = getattr(obj, attr)
except AttributeError:
pass
else:
if self.is_safe_attribute(obj, argument, value):
return value
return self.unsafe_undefined(obj, argument)
return self.undefined(obj=obj, name=argument)
[docs] def getattr(self, obj, attribute):
"""Subscribe an object from sandboxed code and prefer the
attribute. The attribute passed *must* be a bytestring.
"""
try:
value = getattr(obj, attribute)
except AttributeError:
try:
return obj[attribute]
except (TypeError, LookupError):
pass
else:
if self.is_safe_attribute(obj, attribute, value):
return value
return self.unsafe_undefined(obj, attribute)
return self.undefined(obj=obj, name=attribute)
[docs] def unsafe_undefined(self, obj, attribute):
"""Return an undefined object for unsafe attributes."""
return self.undefined('access to attribute %r of %r '
'object is unsafe.' % (
attribute,
obj.__class__.__name__
), name=attribute, obj=obj, exc=SecurityError)
[docs] def call(__self, __context, __obj, *args, **kwargs):
"""Call an object from sandboxed code."""
# the double prefixes are to avoid double keyword argument
# errors when proxying the call.
if not __self.is_safe_callable(__obj):
raise SecurityError('%r is not safely callable' % (__obj,))
return __context.call(__obj, *args, **kwargs)
[docs]class ImmutableSandboxedEnvironment(SandboxedEnvironment):
"""Works exactly like the regular `SandboxedEnvironment` but does not
permit modifications on the builtin mutable objects `list`, `set`, and
`dict` by using the :func:`modifies_known_mutable` function.
"""
[docs] def is_safe_attribute(self, obj, attr, value):
if not SandboxedEnvironment.is_safe_attribute(self, obj, attr, value):
return False
return not modifies_known_mutable(obj, attr)