# -*- coding: utf-8 -*-
"""A sandbox layer that ensures unsafe operations cannot be performed.
Useful when the template itself comes from an untrusted source.
"""
import operator
import types
import warnings
from collections import deque
from string import Formatter

from markupsafe import EscapeFormatter
from markupsafe import Markup

from ._compat import abc
from ._compat import PY2
from ._compat import range_type
from ._compat import string_types
from .environment import Environment
from .exceptions import SecurityError

#: maximum number of items a range may produce
MAX_RANGE = 100000

#: attributes of function objects that are considered unsafe.
if PY2:
 UNSAFE_FUNCTION_ATTRIBUTES = {
 "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 = {"im_class", "im_func", "im_self"}

#: 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"}

# 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=__name__
)

_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
_mutable_set_types += (abc.MutableSet,)
_mutable_mapping_types += (abc.MutableMapping,)
_mutable_sequence_types += (abc.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(abc.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_type(*args)

 if len(rng) > MAX_RANGE:
 raise OverflowError(
 "Range too big. The sandbox blocks ranges larger than"
 " MAX_RANGE (%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 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, 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): # 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("%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 apparently.
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)