387 lines
12 KiB
Python
387 lines
12 KiB
Python
"""Restricted execution facilities.
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The class RExec exports methods r_exec(), r_eval(), r_execfile(), and
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r_import(), which correspond roughly to the built-in operations
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exec, eval(), execfile() and import, but executing the code in an
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environment that only exposes those built-in operations that are
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deemed safe. To this end, a modest collection of 'fake' modules is
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created which mimics the standard modules by the same names. It is a
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policy decision which built-in modules and operations are made
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available; this module provides a reasonable default, but derived
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classes can change the policies e.g. by overriding or extending class
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variables like ok_builtin_modules or methods like make_sys().
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XXX To do:
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- r_open should allow writing tmp dir
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- r_exec etc. with explicit globals/locals? (Use rexec("exec ... in ...")?)
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"""
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import sys
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import __builtin__
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import os
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import ihooks
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class FileBase:
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ok_file_methods = ('fileno', 'flush', 'isatty', 'read', 'readline',
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'readlines', 'seek', 'tell', 'write', 'writelines')
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class FileWrapper(FileBase):
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# XXX This is just like a Bastion -- should use that!
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def __init__(self, f):
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self.f = f
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for m in self.ok_file_methods:
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if not hasattr(self, m) and hasattr(f, m):
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setattr(self, m, getattr(f, m))
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def close(self):
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self.flush()
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TEMPLATE = """
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def %s(self, *args):
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return apply(getattr(self.mod, self.name).%s, args)
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"""
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class FileDelegate(FileBase):
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def __init__(self, mod, name):
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self.mod = mod
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self.name = name
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for m in FileBase.ok_file_methods + ('close',):
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exec TEMPLATE % (m, m)
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class RHooks(ihooks.Hooks):
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def __init__(self, *args):
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# Hacks to support both old and new interfaces:
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# old interface was RHooks(rexec[, verbose])
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# new interface is RHooks([verbose])
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verbose = 0
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rexec = None
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if args and type(args[-1]) == type(0):
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verbose = args[-1]
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args = args[:-1]
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if args and hasattr(args[0], '__class__'):
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rexec = args[0]
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args = args[1:]
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if args:
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raise TypeError, "too many arguments"
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ihooks.Hooks.__init__(self, verbose)
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self.rexec = rexec
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def set_rexec(self, rexec):
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# Called by RExec instance to complete initialization
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self.rexec = rexec
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def is_builtin(self, name):
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return self.rexec.is_builtin(name)
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def init_builtin(self, name):
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m = __import__(name)
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return self.rexec.copy_except(m, ())
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def init_frozen(self, name): raise SystemError, "don't use this"
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def load_source(self, *args): raise SystemError, "don't use this"
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def load_compiled(self, *args): raise SystemError, "don't use this"
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def load_package(self, *args): raise SystemError, "don't use this"
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def load_dynamic(self, name, filename, file):
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return self.rexec.load_dynamic(name, filename, file)
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def add_module(self, name):
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return self.rexec.add_module(name)
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def modules_dict(self):
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return self.rexec.modules
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def default_path(self):
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return self.rexec.modules['sys'].path
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class RModuleLoader(ihooks.FancyModuleLoader):
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def load_module(self, name, stuff):
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file, filename, info = stuff
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m = ihooks.FancyModuleLoader.load_module(self, name, stuff)
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m.__filename__ = filename
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return m
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class RModuleImporter(ihooks.ModuleImporter):
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def reload(self, module, path=None):
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if path is None and hasattr(module, '__filename__'):
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head, tail = os.path.split(module.__filename__)
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path = [os.path.join(head, '')]
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return ihooks.ModuleImporter.reload(self, module, path)
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class RExec(ihooks._Verbose):
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"""Restricted Execution environment."""
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ok_path = tuple(sys.path) # That's a policy decision
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ok_builtin_modules = ('audioop', 'array', 'binascii',
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'cmath', 'errno', 'imageop',
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'marshal', 'math', 'md5', 'operator',
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'parser', 'regex', 'pcre', 'rotor', 'select',
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'strop', 'struct', 'time')
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ok_posix_names = ('error', 'fstat', 'listdir', 'lstat', 'readlink',
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'stat', 'times', 'uname', 'getpid', 'getppid',
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'getcwd', 'getuid', 'getgid', 'geteuid', 'getegid')
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ok_sys_names = ('ps1', 'ps2', 'copyright', 'version',
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'platform', 'exit', 'maxint')
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nok_builtin_names = ('open', 'reload', '__import__')
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def __init__(self, hooks = None, verbose = 0):
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ihooks._Verbose.__init__(self, verbose)
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# XXX There's a circular reference here:
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self.hooks = hooks or RHooks(verbose)
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self.hooks.set_rexec(self)
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self.modules = {}
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self.ok_dynamic_modules = self.ok_builtin_modules
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list = []
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for mname in self.ok_builtin_modules:
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if mname in sys.builtin_module_names:
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list.append(mname)
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self.ok_builtin_modules = tuple(list)
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self.set_trusted_path()
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self.make_builtin()
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self.make_initial_modules()
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# make_sys must be last because it adds the already created
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# modules to its builtin_module_names
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self.make_sys()
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self.loader = RModuleLoader(self.hooks, verbose)
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self.importer = RModuleImporter(self.loader, verbose)
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def set_trusted_path(self):
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# Set the path from which dynamic modules may be loaded.
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# Those dynamic modules must also occur in ok_builtin_modules
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self.trusted_path = filter(os.path.isabs, sys.path)
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def load_dynamic(self, name, filename, file):
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if name not in self.ok_dynamic_modules:
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raise ImportError, "untrusted dynamic module: %s" % name
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if sys.modules.has_key(name):
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src = sys.modules[name]
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else:
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import imp
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src = imp.load_dynamic(name, filename, file)
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dst = self.copy_except(src, [])
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return dst
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def make_initial_modules(self):
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self.make_main()
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self.make_osname()
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# Helpers for RHooks
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def is_builtin(self, mname):
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return mname in self.ok_builtin_modules
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# The make_* methods create specific built-in modules
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def make_builtin(self):
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m = self.copy_except(__builtin__, self.nok_builtin_names)
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m.__import__ = self.r_import
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m.reload = self.r_reload
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m.open = self.r_open
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def make_main(self):
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m = self.add_module('__main__')
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def make_osname(self):
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osname = os.name
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src = __import__(osname)
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dst = self.copy_only(src, self.ok_posix_names)
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dst.environ = e = {}
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for key, value in os.environ.items():
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e[key] = value
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def make_sys(self):
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m = self.copy_only(sys, self.ok_sys_names)
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m.modules = self.modules
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m.argv = ['RESTRICTED']
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m.path = map(None, self.ok_path)
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m = self.modules['sys']
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l = self.modules.keys() + list(self.ok_builtin_modules)
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l.sort()
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m.builtin_module_names = tuple(l)
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# The copy_* methods copy existing modules with some changes
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def copy_except(self, src, exceptions):
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dst = self.copy_none(src)
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for name in dir(src):
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setattr(dst, name, getattr(src, name))
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for name in exceptions:
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try:
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delattr(dst, name)
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except AttributeError:
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pass
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return dst
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def copy_only(self, src, names):
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dst = self.copy_none(src)
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for name in names:
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try:
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value = getattr(src, name)
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except AttributeError:
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continue
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setattr(dst, name, value)
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return dst
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def copy_none(self, src):
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m = self.add_module(src.__name__)
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m.__doc__ = src.__doc__
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return m
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# Add a module -- return an existing module or create one
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def add_module(self, mname):
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if self.modules.has_key(mname):
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return self.modules[mname]
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self.modules[mname] = m = self.hooks.new_module(mname)
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m.__builtins__ = self.modules['__builtin__']
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return m
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# The r* methods are public interfaces
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def r_exec(self, code):
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m = self.add_module('__main__')
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exec code in m.__dict__
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def r_eval(self, code):
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m = self.add_module('__main__')
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return eval(code, m.__dict__)
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def r_execfile(self, file):
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m = self.add_module('__main__')
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return execfile(file, m.__dict__)
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def r_import(self, mname, globals={}, locals={}, fromlist=[]):
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return self.importer.import_module(mname, globals, locals, fromlist)
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def r_reload(self, m):
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return self.importer.reload(m)
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def r_unload(self, m):
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return self.importer.unload(m)
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# The s_* methods are similar but also swap std{in,out,err}
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def make_delegate_files(self):
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s = self.modules['sys']
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self.delegate_stdin = FileDelegate(s, 'stdin')
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self.delegate_stdout = FileDelegate(s, 'stdout')
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self.delegate_stderr = FileDelegate(s, 'stderr')
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self.restricted_stdin = FileWrapper(sys.stdin)
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self.restricted_stdout = FileWrapper(sys.stdout)
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self.restricted_stderr = FileWrapper(sys.stderr)
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def set_files(self):
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if not hasattr(self, 'save_stdin'):
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self.save_files()
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if not hasattr(self, 'delegate_stdin'):
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self.make_delegate_files()
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s = self.modules['sys']
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s.stdin = self.restricted_stdin
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s.stdout = self.restricted_stdout
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s.stderr = self.restricted_stderr
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sys.stdin = self.delegate_stdin
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sys.stdout = self.delegate_stdout
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sys.stderr = self.delegate_stderr
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def reset_files(self):
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self.restore_files()
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s = self.modules['sys']
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self.restricted_stdin = s.stdin
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self.restricted_stdout = s.stdout
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self.restricted_stderr = s.stderr
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def save_files(self):
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self.save_stdin = sys.stdin
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self.save_stdout = sys.stdout
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self.save_stderr = sys.stderr
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def restore_files(self):
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sys.stdin = self.save_stdin
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sys.stdout = self.save_stdout
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sys.stderr = self.save_stderr
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def s_apply(self, func, args=(), kw=None):
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self.save_files()
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try:
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self.set_files()
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if kw:
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r = apply(func, args, kw)
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else:
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r = apply(func, args)
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finally:
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self.restore_files()
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def s_exec(self, *args):
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self.s_apply(self.r_exec, args)
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def s_eval(self, *args):
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self.s_apply(self.r_eval, args)
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def s_execfile(self, *args):
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self.s_apply(self.r_execfile, args)
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def s_import(self, *args):
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self.s_apply(self.r_import, args)
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def s_reload(self, *args):
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self.s_apply(self.r_reload, args)
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def s_unload(self, *args):
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self.s_apply(self.r_unload, args)
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# Restricted open(...)
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def r_open(self, file, mode='r', buf=-1):
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if mode not in ('r', 'rb'):
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raise IOError, "can't open files for writing in restricted mode"
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return open(file, mode, buf)
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def test():
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import traceback
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r = RExec(verbose=('-v' in sys.argv[1:]))
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print "*** RESTRICTED *** Python", sys.version
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print sys.copyright
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while 1:
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try:
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try:
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s = raw_input('>>> ')
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except EOFError:
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print
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break
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if s and s[0] != '#':
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s = s + '\n'
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c = compile(s, '<stdin>', 'single')
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r.r_exec(c)
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except SystemExit, n:
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sys.exit(n)
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except:
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traceback.print_exc()
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if __name__ == '__main__':
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test()
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