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476 lines
16 KiB
476 lines
16 KiB
# -*- coding: utf-8 -*-
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"""
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jinja2.sandbox
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~~~~~~~~~~~~~~
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Adds a sandbox layer to Jinja as it was the default behavior in the old
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Jinja 1 releases. This sandbox is slightly different from Jinja 1 as the
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default behavior is easier to use.
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The behavior can be changed by subclassing the environment.
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:copyright: (c) 2017 by the Jinja Team.
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:license: BSD.
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"""
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import types
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import operator
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from collections import Mapping
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from jinja2.environment import Environment
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from jinja2.exceptions import SecurityError
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from jinja2._compat import string_types, PY2
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from jinja2.utils import Markup
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from markupsafe import EscapeFormatter
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from string import Formatter
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#: maximum number of items a range may produce
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MAX_RANGE = 100000
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#: attributes of function objects that are considered unsafe.
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if PY2:
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UNSAFE_FUNCTION_ATTRIBUTES = set(['func_closure', 'func_code', 'func_dict',
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'func_defaults', 'func_globals'])
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else:
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# On versions > python 2 the special attributes on functions are gone,
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# but they remain on methods and generators for whatever reason.
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UNSAFE_FUNCTION_ATTRIBUTES = set()
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#: unsafe method attributes. function attributes are unsafe for methods too
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UNSAFE_METHOD_ATTRIBUTES = set(['im_class', 'im_func', 'im_self'])
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#: unsafe generator attirbutes.
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UNSAFE_GENERATOR_ATTRIBUTES = set(['gi_frame', 'gi_code'])
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#: unsafe attributes on coroutines
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UNSAFE_COROUTINE_ATTRIBUTES = set(['cr_frame', 'cr_code'])
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#: unsafe attributes on async generators
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UNSAFE_ASYNC_GENERATOR_ATTRIBUTES = set(['ag_code', 'ag_frame'])
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import warnings
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# make sure we don't warn in python 2.6 about stuff we don't care about
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warnings.filterwarnings('ignore', 'the sets module', DeprecationWarning,
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module='jinja2.sandbox')
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from collections import deque
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_mutable_set_types = (set,)
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_mutable_mapping_types = (dict,)
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_mutable_sequence_types = (list,)
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# on python 2.x we can register the user collection types
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try:
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from UserDict import UserDict, DictMixin
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from UserList import UserList
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_mutable_mapping_types += (UserDict, DictMixin)
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_mutable_set_types += (UserList,)
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except ImportError:
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pass
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# if sets is still available, register the mutable set from there as well
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try:
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from sets import Set
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_mutable_set_types += (Set,)
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except ImportError:
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pass
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#: register Python 2.6 abstract base classes
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from collections import MutableSet, MutableMapping, MutableSequence
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_mutable_set_types += (MutableSet,)
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_mutable_mapping_types += (MutableMapping,)
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_mutable_sequence_types += (MutableSequence,)
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_mutable_spec = (
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(_mutable_set_types, frozenset([
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'add', 'clear', 'difference_update', 'discard', 'pop', 'remove',
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'symmetric_difference_update', 'update'
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])),
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(_mutable_mapping_types, frozenset([
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'clear', 'pop', 'popitem', 'setdefault', 'update'
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])),
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(_mutable_sequence_types, frozenset([
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'append', 'reverse', 'insert', 'sort', 'extend', 'remove'
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])),
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(deque, frozenset([
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'append', 'appendleft', 'clear', 'extend', 'extendleft', 'pop',
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'popleft', 'remove', 'rotate'
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]))
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)
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class _MagicFormatMapping(Mapping):
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"""This class implements a dummy wrapper to fix a bug in the Python
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standard library for string formatting.
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See https://bugs.python.org/issue13598 for information about why
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this is necessary.
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"""
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def __init__(self, args, kwargs):
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self._args = args
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self._kwargs = kwargs
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self._last_index = 0
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def __getitem__(self, key):
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if key == '':
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idx = self._last_index
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self._last_index += 1
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try:
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return self._args[idx]
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except LookupError:
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pass
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key = str(idx)
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return self._kwargs[key]
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def __iter__(self):
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return iter(self._kwargs)
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def __len__(self):
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return len(self._kwargs)
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def inspect_format_method(callable):
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if not isinstance(callable, (types.MethodType,
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types.BuiltinMethodType)) or \
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callable.__name__ != 'format':
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return None
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obj = callable.__self__
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if isinstance(obj, string_types):
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return obj
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def safe_range(*args):
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"""A range that can't generate ranges with a length of more than
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MAX_RANGE items.
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"""
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rng = range(*args)
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if len(rng) > MAX_RANGE:
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raise OverflowError('range too big, maximum size for range is %d' %
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MAX_RANGE)
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return rng
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def unsafe(f):
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"""Marks a function or method as unsafe.
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::
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@unsafe
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def delete(self):
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pass
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"""
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f.unsafe_callable = True
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return f
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def is_internal_attribute(obj, attr):
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"""Test if the attribute given is an internal python attribute. For
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example this function returns `True` for the `func_code` attribute of
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python objects. This is useful if the environment method
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:meth:`~SandboxedEnvironment.is_safe_attribute` is overridden.
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>>> from jinja2.sandbox import is_internal_attribute
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>>> is_internal_attribute(str, "mro")
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True
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>>> is_internal_attribute(str, "upper")
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False
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"""
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if isinstance(obj, types.FunctionType):
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if attr in UNSAFE_FUNCTION_ATTRIBUTES:
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return True
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elif isinstance(obj, types.MethodType):
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if attr in UNSAFE_FUNCTION_ATTRIBUTES or \
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attr in UNSAFE_METHOD_ATTRIBUTES:
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return True
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elif isinstance(obj, type):
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if attr == 'mro':
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return True
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elif isinstance(obj, (types.CodeType, types.TracebackType, types.FrameType)):
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return True
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elif isinstance(obj, types.GeneratorType):
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if attr in UNSAFE_GENERATOR_ATTRIBUTES:
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return True
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elif hasattr(types, 'CoroutineType') and isinstance(obj, types.CoroutineType):
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if attr in UNSAFE_COROUTINE_ATTRIBUTES:
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return True
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elif hasattr(types, 'AsyncGeneratorType') and isinstance(obj, types.AsyncGeneratorType):
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if attr in UNSAFE_ASYNC_GENERATOR_ATTRIBUTES:
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return True
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return attr.startswith('__')
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def modifies_known_mutable(obj, attr):
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"""This function checks if an attribute on a builtin mutable object
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(list, dict, set or deque) would modify it if called. It also supports
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the "user"-versions of the objects (`sets.Set`, `UserDict.*` etc.) and
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with Python 2.6 onwards the abstract base classes `MutableSet`,
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`MutableMapping`, and `MutableSequence`.
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>>> modifies_known_mutable({}, "clear")
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True
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>>> modifies_known_mutable({}, "keys")
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False
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>>> modifies_known_mutable([], "append")
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True
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>>> modifies_known_mutable([], "index")
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False
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If called with an unsupported object (such as unicode) `False` is
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returned.
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>>> modifies_known_mutable("foo", "upper")
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False
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"""
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for typespec, unsafe in _mutable_spec:
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if isinstance(obj, typespec):
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return attr in unsafe
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return False
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class SandboxedEnvironment(Environment):
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"""The sandboxed environment. It works like the regular environment but
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tells the compiler to generate sandboxed code. Additionally subclasses of
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this environment may override the methods that tell the runtime what
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attributes or functions are safe to access.
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If the template tries to access insecure code a :exc:`SecurityError` is
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raised. However also other exceptions may occur during the rendering so
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the caller has to ensure that all exceptions are caught.
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"""
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sandboxed = True
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#: default callback table for the binary operators. A copy of this is
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#: available on each instance of a sandboxed environment as
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#: :attr:`binop_table`
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default_binop_table = {
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'+': operator.add,
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'-': operator.sub,
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'*': operator.mul,
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'/': operator.truediv,
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'//': operator.floordiv,
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'**': operator.pow,
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'%': operator.mod
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}
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#: default callback table for the unary operators. A copy of this is
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#: available on each instance of a sandboxed environment as
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#: :attr:`unop_table`
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default_unop_table = {
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'+': operator.pos,
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'-': operator.neg
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}
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#: a set of binary operators that should be intercepted. Each operator
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#: that is added to this set (empty by default) is delegated to the
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#: :meth:`call_binop` method that will perform the operator. The default
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#: operator callback is specified by :attr:`binop_table`.
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#:
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#: The following binary operators are interceptable:
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#: ``//``, ``%``, ``+``, ``*``, ``-``, ``/``, and ``**``
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#:
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#: The default operation form the operator table corresponds to the
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#: builtin function. Intercepted calls are always slower than the native
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#: operator call, so make sure only to intercept the ones you are
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#: interested in.
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#:
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#: .. versionadded:: 2.6
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intercepted_binops = frozenset()
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#: a set of unary operators that should be intercepted. Each operator
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#: that is added to this set (empty by default) is delegated to the
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#: :meth:`call_unop` method that will perform the operator. The default
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#: operator callback is specified by :attr:`unop_table`.
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#:
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#: The following unary operators are interceptable: ``+``, ``-``
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#:
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#: The default operation form the operator table corresponds to the
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#: builtin function. Intercepted calls are always slower than the native
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#: operator call, so make sure only to intercept the ones you are
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#: interested in.
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#:
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#: .. versionadded:: 2.6
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intercepted_unops = frozenset()
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def intercept_unop(self, operator):
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"""Called during template compilation with the name of a unary
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operator to check if it should be intercepted at runtime. If this
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method returns `True`, :meth:`call_unop` is excuted for this unary
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operator. The default implementation of :meth:`call_unop` will use
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the :attr:`unop_table` dictionary to perform the operator with the
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same logic as the builtin one.
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The following unary operators are interceptable: ``+`` and ``-``
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Intercepted calls are always slower than the native operator call,
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so make sure only to intercept the ones you are interested in.
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.. versionadded:: 2.6
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"""
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return False
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def __init__(self, *args, **kwargs):
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Environment.__init__(self, *args, **kwargs)
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self.globals['range'] = safe_range
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self.binop_table = self.default_binop_table.copy()
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self.unop_table = self.default_unop_table.copy()
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def is_safe_attribute(self, obj, attr, value):
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"""The sandboxed environment will call this method to check if the
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attribute of an object is safe to access. Per default all attributes
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starting with an underscore are considered private as well as the
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special attributes of internal python objects as returned by the
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:func:`is_internal_attribute` function.
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"""
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return not (attr.startswith('_') or is_internal_attribute(obj, attr))
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def is_safe_callable(self, obj):
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"""Check if an object is safely callable. Per default a function is
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considered safe unless the `unsafe_callable` attribute exists and is
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True. Override this method to alter the behavior, but this won't
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affect the `unsafe` decorator from this module.
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"""
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return not (getattr(obj, 'unsafe_callable', False) or
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getattr(obj, 'alters_data', False))
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def call_binop(self, context, operator, left, right):
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"""For intercepted binary operator calls (:meth:`intercepted_binops`)
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this function is executed instead of the builtin operator. This can
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be used to fine tune the behavior of certain operators.
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.. versionadded:: 2.6
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"""
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return self.binop_table[operator](left, right)
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def call_unop(self, context, operator, arg):
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"""For intercepted unary operator calls (:meth:`intercepted_unops`)
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this function is executed instead of the builtin operator. This can
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be used to fine tune the behavior of certain operators.
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.. versionadded:: 2.6
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"""
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return self.unop_table[operator](arg)
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def getitem(self, obj, argument):
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"""Subscribe an object from sandboxed code."""
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try:
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return obj[argument]
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except (TypeError, LookupError):
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if isinstance(argument, string_types):
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try:
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attr = str(argument)
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except Exception:
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pass
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else:
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try:
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value = getattr(obj, attr)
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except AttributeError:
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pass
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else:
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if self.is_safe_attribute(obj, argument, value):
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return value
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return self.unsafe_undefined(obj, argument)
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return self.undefined(obj=obj, name=argument)
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def getattr(self, obj, attribute):
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"""Subscribe an object from sandboxed code and prefer the
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attribute. The attribute passed *must* be a bytestring.
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"""
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try:
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value = getattr(obj, attribute)
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except AttributeError:
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try:
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return obj[attribute]
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except (TypeError, LookupError):
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pass
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else:
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if self.is_safe_attribute(obj, attribute, value):
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return value
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return self.unsafe_undefined(obj, attribute)
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return self.undefined(obj=obj, name=attribute)
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def unsafe_undefined(self, obj, attribute):
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"""Return an undefined object for unsafe attributes."""
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return self.undefined('access to attribute %r of %r '
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'object is unsafe.' % (
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attribute,
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obj.__class__.__name__
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), name=attribute, obj=obj, exc=SecurityError)
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def format_string(self, s, args, kwargs):
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"""If a format call is detected, then this is routed through this
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method so that our safety sandbox can be used for it.
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"""
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if isinstance(s, Markup):
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formatter = SandboxedEscapeFormatter(self, s.escape)
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else:
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formatter = SandboxedFormatter(self)
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kwargs = _MagicFormatMapping(args, kwargs)
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rv = formatter.vformat(s, args, kwargs)
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return type(s)(rv)
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def call(__self, __context, __obj, *args, **kwargs):
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"""Call an object from sandboxed code."""
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fmt = inspect_format_method(__obj)
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if fmt is not None:
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return __self.format_string(fmt, args, kwargs)
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# the double prefixes are to avoid double keyword argument
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# errors when proxying the call.
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if not __self.is_safe_callable(__obj):
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raise SecurityError('%r is not safely callable' % (__obj,))
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return __context.call(__obj, *args, **kwargs)
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class ImmutableSandboxedEnvironment(SandboxedEnvironment):
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"""Works exactly like the regular `SandboxedEnvironment` but does not
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permit modifications on the builtin mutable objects `list`, `set`, and
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`dict` by using the :func:`modifies_known_mutable` function.
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"""
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def is_safe_attribute(self, obj, attr, value):
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if not SandboxedEnvironment.is_safe_attribute(self, obj, attr, value):
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return False
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return not modifies_known_mutable(obj, attr)
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# This really is not a public API apparenlty.
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try:
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from _string import formatter_field_name_split
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except ImportError:
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def formatter_field_name_split(field_name):
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return field_name._formatter_field_name_split()
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class SandboxedFormatterMixin(object):
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def __init__(self, env):
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self._env = env
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def get_field(self, field_name, args, kwargs):
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first, rest = formatter_field_name_split(field_name)
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obj = self.get_value(first, args, kwargs)
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for is_attr, i in rest:
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if is_attr:
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obj = self._env.getattr(obj, i)
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else:
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obj = self._env.getitem(obj, i)
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return obj, first
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class SandboxedFormatter(SandboxedFormatterMixin, Formatter):
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def __init__(self, env):
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SandboxedFormatterMixin.__init__(self, env)
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Formatter.__init__(self)
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class SandboxedEscapeFormatter(SandboxedFormatterMixin, EscapeFormatter):
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def __init__(self, env, escape):
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SandboxedFormatterMixin.__init__(self, env)
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EscapeFormatter.__init__(self, escape)
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