| # -*- 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' |
| ])) |
| ) |
| |
| |
| 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 |
| 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 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() |
| |
| 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 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) |
| |
| |
| 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) |
