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##############################################################################
#
# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################
"""Compiles restricted code using the compiler module from the
Python standard library.
"""
__version__='$Revision: 1.6 $'[11:-2]
from compiler import ast, parse, misc, syntax, pycodegen
from compiler.pycodegen import AbstractCompileMode, Expression, \
Interactive, Module, ModuleCodeGenerator, FunctionCodeGenerator, findOp
import MutatingWalker
from RestrictionMutator import RestrictionMutator
def niceParse(source, filename, mode):
try:
return parse(source, mode)
except:
# Try to make a clean error message using
# the builtin Python compiler.
try:
compile(source, filename, mode)
except SyntaxError:
raise
# Some other error occurred.
raise
class RestrictedCompileMode(AbstractCompileMode):
"""Abstract base class for hooking up custom CodeGenerator."""
# See concrete subclasses below.
def __init__(self, source, filename):
self.rm = RestrictionMutator()
AbstractCompileMode.__init__(self, source, filename)
def parse(self):
return niceParse(self.source, self.filename, self.mode)
def _get_tree(self):
tree = self.parse()
MutatingWalker.walk(tree, self.rm)
if self.rm.errors:
raise SyntaxError(self.rm.errors[0])
misc.set_filename(self.filename, tree)
syntax.check(tree)
return tree
def compile(self):
tree = self._get_tree()
gen = self.CodeGeneratorClass(tree)
self.code = gen.getCode()
def compileAndTuplize(gen):
try:
gen.compile()
except SyntaxError as v:
return None, (str(v),), gen.rm.warnings, gen.rm.used_names
return gen.getCode(), (), gen.rm.warnings, gen.rm.used_names
def compile_restricted_function(p, body, name, filename, globalize=None):
"""Compiles a restricted code object for a function.
The function can be reconstituted using the 'new' module:
new.function(<code>, <globals>)
The globalize argument, if specified, is a list of variable names to be
treated as globals (code is generated as if each name in the list
appeared in a global statement at the top of the function).
"""
gen = RFunction(p, body, name, filename, globalize)
return compileAndTuplize(gen)
def compile_restricted_exec(s, filename='<string>'):
"""Compiles a restricted code suite."""
gen = RModule(s, filename)
return compileAndTuplize(gen)
def compile_restricted_eval(s, filename='<string>'):
"""Compiles a restricted expression."""
gen = RExpression(s, filename)
return compileAndTuplize(gen)
def compile_restricted(source, filename, mode):
"""Replacement for the builtin compile() function."""
if mode == "single":
gen = RInteractive(source, filename)
elif mode == "exec":
gen = RModule(source, filename)
elif mode == "eval":
gen = RExpression(source, filename)
else:
raise ValueError("compile_restricted() 3rd arg must be 'exec' or "
"'eval' or 'single'")
gen.compile()
return gen.getCode()
class RestrictedCodeGenerator:
"""Mixin for CodeGenerator to replace UNPACK_SEQUENCE bytecodes.
The UNPACK_SEQUENCE opcode is not safe because it extracts
elements from a sequence without using a safe iterator or
making __getitem__ checks.
This code generator replaces use of UNPACK_SEQUENCE with calls to
a function that unpacks the sequence, performes the appropriate
security checks, and returns a simple list.
"""
# Replace the standard code generator for assignments to tuples
# and lists.
def _gen_safe_unpack_sequence(self, num):
# We're at a place where UNPACK_SEQUENCE should be generated, to
# unpack num items. That's a security hole, since it exposes
# individual items from an arbitrary iterable. We don't remove
# the UNPACK_SEQUENCE, but instead insert a call to our _getiter_()
# wrapper first. That applies security checks to each item as
# it's delivered. codegen is (just) a bit messy because the
# iterable is already on the stack, so we have to do a stack swap
# to get things in the right order.
self.emit('LOAD_GLOBAL', '_getiter_')
self.emit('ROT_TWO')
self.emit('CALL_FUNCTION', 1)
self.emit('UNPACK_SEQUENCE', num)
def _visitAssSequence(self, node):
if findOp(node) != 'OP_DELETE':
self._gen_safe_unpack_sequence(len(node.nodes))
for child in node.nodes:
self.visit(child)
visitAssTuple = _visitAssSequence
visitAssList = _visitAssSequence
# Call to generate code for unpacking nested tuple arguments
# in function calls.
def unpackSequence(self, tup):
self._gen_safe_unpack_sequence(len(tup))
for elt in tup:
if isinstance(elt, tuple):
self.unpackSequence(elt)
else:
self._nameOp('STORE', elt)
# A collection of code generators that adds the restricted mixin to
# handle unpacking for all the different compilation modes. They
# are defined here (at the end) so that can refer to RestrictedCodeGenerator.
class RestrictedFunctionCodeGenerator(RestrictedCodeGenerator,
pycodegen.FunctionCodeGenerator):
pass
class RestrictedExpressionCodeGenerator(RestrictedCodeGenerator,
pycodegen.ExpressionCodeGenerator):
pass
class RestrictedInteractiveCodeGenerator(RestrictedCodeGenerator,
pycodegen.InteractiveCodeGenerator):
pass
class RestrictedModuleCodeGenerator(RestrictedCodeGenerator,
pycodegen.ModuleCodeGenerator):
def initClass(self):
ModuleCodeGenerator.initClass(self)
self.__class__.FunctionGen = RestrictedFunctionCodeGenerator
# These subclasses work around the definition of stub compile and mode
# attributes in the common base class AbstractCompileMode. If it
# didn't define new attributes, then the stub code inherited via
# RestrictedCompileMode would override the real definitions in
# Expression.
class RExpression(RestrictedCompileMode, Expression):
mode = "eval"
CodeGeneratorClass = RestrictedExpressionCodeGenerator
class RInteractive(RestrictedCompileMode, Interactive):
mode = "single"
CodeGeneratorClass = RestrictedInteractiveCodeGenerator
class RModule(RestrictedCompileMode, Module):
mode = "exec"
CodeGeneratorClass = RestrictedModuleCodeGenerator
class RFunction(RModule):
"""A restricted Python function built from parts."""
CodeGeneratorClass = RestrictedModuleCodeGenerator
def __init__(self, p, body, name, filename, globals):
self.params = p
self.body = body
self.name = name
self.globals = globals or []
RModule.__init__(self, None, filename)
def parse(self):
# Parse the parameters and body, then combine them.
firstline = 'def f(%s): pass' % self.params
tree = niceParse(firstline, '<function parameters>', 'exec')
f = tree.node.nodes[0]
body_code = niceParse(self.body, self.filename, 'exec')
# Stitch the body code into the function.
f.code.nodes = body_code.node.nodes
f.name = self.name
# Look for a docstring.
stmt1 = f.code.nodes[0]
if (isinstance(stmt1, ast.Discard) and
isinstance(stmt1.expr, ast.Const) and
isinstance(stmt1.expr.value, str)):
f.doc = stmt1.expr.value
# The caller may specify that certain variables are globals
# so that they can be referenced before a local assignment.
# The only known example is the variables context, container,
# script, traverse_subpath in PythonScripts.
if self.globals:
f.code.nodes.insert(0, ast.Global(self.globals))
return tree
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