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# -- 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) 2017 by the Jinja Team. :license: BSD. """ import types import operator from collections import Mapping from jinja2.environment import Environment from jinja2.exceptions import SecurityError from jinja2._compat import string_types, PY2 from jinja2.utils import Markup from markupsafe import EscapeFormatter from string import Formatter #: 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']) #: unsafe attributes on coroutines UNSAFE_COROUTINE_ATTRIBUTES = set(['cr_frame', 'cr_code']) #: unsafe attributes on async generators UNSAFE_ASYNC_GENERATOR_ATTRIBUTES = set(['ag_code', 'ag_frame']) 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 from collections import MutableSet, MutableMapping, MutableSequence _mutable_set_types += (MutableSet,) _mutable_mapping_types += (MutableMapping,) _mutable_sequence_types += (MutableSequence,) _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' ])) ) class _MagicFormatMapping(Mapping): """This class implements a dummy wrapper to fix a bug in the Python standard library for string formatting. See https://bugs.python.org/issue13598 for information about why this is necessary. """ def __init__(self, args, kwargs): self._args = args self._kwargs = kwargs self._last_index = 0 def __getitem__(self, key): if key == '': idx = self._last_index self._last_index += 1 try: return self._args[idx] except LookupError: pass key = str(idx) return self._kwargs[key] def __iter__(self): return iter(self._kwargs) def __len__(self): return len(self._kwargs) def inspect_format_method(callable): if not isinstance(callable, (types.MethodType, types.BuiltinMethodType)) or \ callable.__name__ not in ('format', 'format_map'): return None obj = callable.__self__ if isinstance(obj, string_types): return obj 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 def unsafe(f): """Marks a function or method as unsafe. :: @unsafe def delete(self): pass """ f.unsafe_callable = True return f 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 elif hasattr(types, 'CoroutineType') and isinstance(obj, types.CoroutineType): if attr in UNSAFE_COROUTINE_ATTRIBUTES: return True elif hasattr(types, 'AsyncGeneratorType') and isinstance(obj, types.AsyncGeneratorType): if attr in UNSAFE_ASYNC_GENERATOR_ATTRIBUTES: return True return attr.startswith('__') 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 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 occur during the rendering so the caller has to ensure that all exceptions are caught. """ 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() 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 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() 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)) 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)) 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) 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) 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) 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) 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) def format_string(self, s, args, kwargs, format_func=None): """If a format call is detected, then this is routed through this method so that our safety sandbox can be used for it. """ if isinstance(s, Markup): formatter = SandboxedEscapeFormatter(self, s.escape) else: formatter = SandboxedFormatter(self) if format_func is not None and format_func.__name__ == 'format_map': if len(args) != 1 or kwargs: raise TypeError( 'format_map() takes exactly one argument %d given' % (len(args) + (kwargs is not None)) ) kwargs = args[0] args = None kwargs = _MagicFormatMapping(args, kwargs) rv = formatter.vformat(s, args, kwargs) return type(s)(rv) def call(__self, __context, __obj, args, kwargs): """Call an object from sandboxed code.""" fmt = inspect_format_method(__obj) if fmt is not None: return __self.format_string(fmt, args, kwargs, __obj) # 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) 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. """ 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) # This really is not a public API apparenlty. try: from _string import formatter_field_name_split except ImportError: def formatter_field_name_split(field_name): return field_name._formatter_field_name_split() class SandboxedFormatterMixin(object): def __init__(self, env): self._env = env def get_field(self, field_name, args, kwargs): first, rest = formatter_field_name_split(field_name) obj = self.get_value(first, args, kwargs) for is_attr, i in rest: if is_attr: obj = self._env.getattr(obj, i) else: obj = self._env.getitem(obj, i) return obj, first class SandboxedFormatter(SandboxedFormatterMixin, Formatter): def __init__(self, env): SandboxedFormatterMixin.__init__(self, env) Formatter.__init__(self) class SandboxedEscapeFormatter(SandboxedFormatterMixin, EscapeFormatter): def __init__(self, env, escape): SandboxedFormatterMixin.__init__(self, env) EscapeFormatter.__init__(self, escape)

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