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Diffstat (limited to 'src/jinja2/sandbox.py')
| -rw-r--r-- | src/jinja2/sandbox.py | 419 |
1 files changed, 0 insertions, 419 deletions
diff --git a/src/jinja2/sandbox.py b/src/jinja2/sandbox.py deleted file mode 100644 index 5c6d0946..00000000 --- a/src/jinja2/sandbox.py +++ /dev/null @@ -1,419 +0,0 @@ -"""A sandbox layer that ensures unsafe operations cannot be performed. -Useful when the template itself comes from an untrusted source. -""" -import operator -import types -from _string import formatter_field_name_split -from collections import abc -from collections import deque -from string import Formatter - -from markupsafe import EscapeFormatter -from markupsafe import Markup - -from .environment import Environment -from .exceptions import SecurityError - -#: maximum number of items a range may produce -MAX_RANGE = 100000 - -#: Unsafe function attributes. -UNSAFE_FUNCTION_ATTRIBUTES = set() - -#: Unsafe method attributes. Function attributes are unsafe for methods too. -UNSAFE_METHOD_ATTRIBUTES = set() - -#: unsafe generator attributes. -UNSAFE_GENERATOR_ATTRIBUTES = {"gi_frame", "gi_code"} - -#: unsafe attributes on coroutines -UNSAFE_COROUTINE_ATTRIBUTES = {"cr_frame", "cr_code"} - -#: unsafe attributes on async generators -UNSAFE_ASYNC_GENERATOR_ATTRIBUTES = {"ag_code", "ag_frame"} - -_mutable_spec = ( - ( - abc.MutableSet, - frozenset( - [ - "add", - "clear", - "difference_update", - "discard", - "pop", - "remove", - "symmetric_difference_update", - "update", - ] - ), - ), - ( - abc.MutableMapping, - frozenset(["clear", "pop", "popitem", "setdefault", "update"]), - ), - ( - abc.MutableSequence, - frozenset(["append", "reverse", "insert", "sort", "extend", "remove"]), - ), - ( - deque, - frozenset( - [ - "append", - "appendleft", - "clear", - "extend", - "extendleft", - "pop", - "popleft", - "remove", - "rotate", - ] - ), - ), -) - - -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, str): - 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. The sandbox blocks ranges larger than" - f" MAX_RANGE ({MAX_RANGE})." - ) - - return rng - - -def unsafe(f): - """Marks a function or method as unsafe. - - .. code-block: python - - @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) or the corresponding ABCs would modify it - if called. - - >>> 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, ``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 executed 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, str): - 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( - f"access to attribute {attribute!r} of" - f" {obj.__class__.__name__!r} object is unsafe.", - 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" - f" {len(args) + (kwargs is not None)} given" - ) - - kwargs = args[0] - args = None - - rv = formatter.vformat(s, args, kwargs) - return type(s)(rv) - - def call(__self, __context, __obj, *args, **kwargs): # noqa: B902 - """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(f"{__obj!r} is not safely callable") - 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) - - -class SandboxedFormatterMixin: - 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) |