"""Restricted execution facilities. The class RExec exports methods r_exec(), r_eval(), r_execfile(), andr_import(), which correspond roughly to the built-in operationsexec, eval(), execfile() and import, but executing the code in anenvironment that only exposes those built-in operations that aredeemed safe.  To this end, a modest collection of 'fake' modules iscreated which mimics the standard modules by the same names.  It is apolicy decision which built-in modules and operations are madeavailable; this module provides a reasonable default, but derivedclasses can change the policies e.g. by overriding or extending classvariables like ok_builtin_modules or methods like make_sys(). XXX To do:- r_open should allow writing tmp dir- r_exec etc. with explicit globals/locals? (Use rexec("exec ... in ...")?) """  import sysimport __builtin__import osimport ihooksimport imp __all__ = ["RExec"] class FileBase:     ok_file_methods = ('fileno', 'flush', 'isatty', 'read', 'readline',            'readlines', 'seek', 'tell', 'write', 'writelines', 'xreadlines',            '__iter__')  class FileWrapper(FileBase):     # XXX This is just like a Bastion -- should use that!     def __init__(self, f):        for m in self.ok_file_methods:            if not hasattr(self, m) and hasattr(f, m):                setattr(self, m, getattr(f, m))     def close(self):        self.flush()  TEMPLATE = """def %s(self, *args):        return getattr(self.mod, self.name).%s(*args)""" class FileDelegate(FileBase):     def __init__(self, mod, name):        self.mod = mod        self.name = name     for m in FileBase.ok_file_methods + ('close',):        exec TEMPLATE % (m, m)  class RHooks(ihooks.Hooks):     def __init__(self, *args):        # Hacks to support both old and new interfaces:        # old interface was RHooks(rexec[, verbose])        # new interface is RHooks([verbose])        verbose = 0        rexec = None        if args and type(args[-1]) == type(0):            verbose = args[-1]            args = args[:-1]        if args and hasattr(args[0], '__class__'):            rexec = args[0]            args = args[1:]        if args:            raise TypeError, "too many arguments"        ihooks.Hooks.__init__(self, verbose)        self.rexec = rexec     def set_rexec(self, rexec):        # Called by RExec instance to complete initialization        self.rexec = rexec     def get_suffixes(self):        return self.rexec.get_suffixes()     def is_builtin(self, name):        return self.rexec.is_builtin(name)     def init_builtin(self, name):        m = __import__(name)        return self.rexec.copy_except(m, ())     def init_frozen(self, name): raise SystemError, "don't use this"    def load_source(self, *args): raise SystemError, "don't use this"    def load_compiled(self, *args): raise SystemError, "don't use this"    def load_package(self, *args): raise SystemError, "don't use this"     def load_dynamic(self, name, filename, file):        return self.rexec.load_dynamic(name, filename, file)     def add_module(self, name):        return self.rexec.add_module(name)     def modules_dict(self):        return self.rexec.modules     def default_path(self):        return self.rexec.modules['sys'].path  # XXX Backwards compatibilityRModuleLoader = ihooks.FancyModuleLoaderRModuleImporter = ihooks.ModuleImporter  class RExec(ihooks._Verbose):    """Basic restricted execution framework.     Code executed in this restricted environment will only have access to    modules and functions that are deemed safe; you can subclass RExec to    add or remove capabilities as desired.     The RExec class can prevent code from performing unsafe operations like    reading or writing disk files, or using TCP/IP sockets.  However, it does    not protect against code using extremely large amounts of memory or    processor time.     """     ok_path = tuple(sys.path)           # That's a policy decision     ok_builtin_modules = ('audioop', 'array', 'binascii',                          'cmath', 'errno', 'imageop',                          'marshal', 'math', 'md5', 'operator',                          'parser', 'select',                          'sha', '_sre', 'strop', 'struct', 'time',                          '_weakref')     ok_posix_names = ('error', 'fstat', 'listdir', 'lstat', 'readlink',                      'stat', 'times', 'uname', 'getpid', 'getppid',                      'getcwd', 'getuid', 'getgid', 'geteuid', 'getegid')     ok_sys_names = ('byteorder', 'copyright', 'exit', 'getdefaultencoding',                    'getrefcount', 'hexversion', 'maxint', 'maxunicode',                    'platform', 'ps1', 'ps2', 'version', 'version_info')     nok_builtin_names = ('open', 'file', 'reload', '__import__')     ok_file_types = (imp.C_EXTENSION, imp.PY_SOURCE)     def __init__(self, hooks = None, verbose = 0):        """Returns an instance of the RExec class.         The hooks parameter is an instance of the RHooks class or a subclass        of it.  If it is omitted or None, the default RHooks class is        instantiated.         Whenever the RExec module searches for a module (even a built-in one)        or reads a module's code, it doesn't actually go out to the file        system itself.  Rather, it calls methods of an RHooks instance that        was passed to or created by its constructor.  (Actually, the RExec        object doesn't make these calls --- they are made by a module loader        object that's part of the RExec object.  This allows another level of        flexibility, which can be useful when changing the mechanics of        import within the restricted environment.)         By providing an alternate RHooks object, we can control the file        system accesses made to import a module, without changing the        actual algorithm that controls the order in which those accesses are        made.  For instance, we could substitute an RHooks object that        passes all filesystem requests to a file server elsewhere, via some        RPC mechanism such as ILU.  Grail's applet loader uses this to support        importing applets from a URL for a directory.         If the verbose parameter is true, additional debugging output may be        sent to standard output.         """         raise RuntimeError, "This code is not secure in Python 2.2 and 2.3"         ihooks._Verbose.__init__(self, verbose)        # XXX There's a circular reference here:        self.hooks = hooks or RHooks(verbose)        self.hooks.set_rexec(self)        self.modules = {}        self.ok_dynamic_modules = self.ok_builtin_modules        list = []        for mname in self.ok_builtin_modules:            if mname in sys.builtin_module_names:                list.append(mname)        self.ok_builtin_modules = tuple(list)        self.set_trusted_path()        self.make_builtin()        self.make_initial_modules()        # make_sys must be last because it adds the already created        # modules to its builtin_module_names        self.make_sys()        self.loader = RModuleLoader(self.hooks, verbose)        self.importer = RModuleImporter(self.loader, verbose)     def set_trusted_path(self):        # Set the path from which dynamic modules may be loaded.        # Those dynamic modules must also occur in ok_builtin_modules        self.trusted_path = filter(os.path.isabs, sys.path)     def load_dynamic(self, name, filename, file):        if name not in self.ok_dynamic_modules:            raise ImportError, "untrusted dynamic module: %s" % name        if name in sys.modules:            src = sys.modules[name]        else:            src = imp.load_dynamic(name, filename, file)        dst = self.copy_except(src, [])        return dst     def make_initial_modules(self):        self.make_main()        self.make_osname()     # Helpers for RHooks     def get_suffixes(self):        return [item   # (suff, mode, type)                for item in imp.get_suffixes()                if item[2] in self.ok_file_types]     def is_builtin(self, mname):        return mname in self.ok_builtin_modules     # The make_* methods create specific built-in modules     def make_builtin(self):        m = self.copy_except(__builtin__, self.nok_builtin_names)        m.__import__ = self.r_import        m.reload = self.r_reload        m.open = m.file = self.r_open     def make_main(self):        m = self.add_module('__main__')     def make_osname(self):        osname = os.name        src = __import__(osname)        dst = self.copy_only(src, self.ok_posix_names)        dst.environ = e = {}        for key, value in os.environ.items():            e[key] = value     def make_sys(self):        m = self.copy_only(sys, self.ok_sys_names)        m.modules = self.modules        m.argv = ['RESTRICTED']        m.path = map(None, self.ok_path)        m.exc_info = self.r_exc_info        m = self.modules['sys']        l = self.modules.keys() + list(self.ok_builtin_modules)        l.sort()        m.builtin_module_names = tuple(l)     # The copy_* methods copy existing modules with some changes     def copy_except(self, src, exceptions):        dst = self.copy_none(src)        for name in dir(src):            setattr(dst, name, getattr(src, name))        for name in exceptions:            try:                delattr(dst, name)            except AttributeError:                pass        return dst     def copy_only(self, src, names):        dst = self.copy_none(src)        for name in names:            try:                value = getattr(src, name)            except AttributeError:                continue            setattr(dst, name, value)        return dst     def copy_none(self, src):        m = self.add_module(src.__name__)        m.__doc__ = src.__doc__        return m     # Add a module -- return an existing module or create one     def add_module(self, mname):        m = self.modules.get(mname)        if m is None:            self.modules[mname] = m = self.hooks.new_module(mname)        m.__builtins__ = self.modules['__builtin__']        return m     # The r* methods are public interfaces     def r_exec(self, code):        """Execute code within a restricted environment.         The code parameter must either be a string containing one or more        lines of Python code, or a compiled code object, which will be        executed in the restricted environment's __main__ module.         """        m = self.add_module('__main__')        exec code in m.__dict__     def r_eval(self, code):        """Evaluate code within a restricted environment.         The code parameter must either be a string containing a Python        expression, or a compiled code object, which will be evaluated in        the restricted environment's __main__ module.  The value of the        expression or code object will be returned.         """        m = self.add_module('__main__')        return eval(code, m.__dict__)     def r_execfile(self, file):        """Execute the Python code in the file in the restricted        environment's __main__ module.         """        m = self.add_module('__main__')        execfile(file, m.__dict__)     def r_import(self, mname, globals={}, locals={}, fromlist=[]):        """Import a module, raising an ImportError exception if the module        is considered unsafe.         This method is implicitly called by code executing in the        restricted environment.  Overriding this method in a subclass is        used to change the policies enforced by a restricted environment.         """        return self.importer.import_module(mname, globals, locals, fromlist)     def r_reload(self, m):        """Reload the module object, re-parsing and re-initializing it.         This method is implicitly called by code executing in the        restricted environment.  Overriding this method in a subclass is        used to change the policies enforced by a restricted environment.         """        return self.importer.reload(m)     def r_unload(self, m):        """Unload the module.         Removes it from the restricted environment's sys.modules dictionary.         This method is implicitly called by code executing in the        restricted environment.  Overriding this method in a subclass is        used to change the policies enforced by a restricted environment.         """        return self.importer.unload(m)     # The s_* methods are similar but also swap std{in,out,err}     def make_delegate_files(self):        s = self.modules['sys']        self.delegate_stdin = FileDelegate(s, 'stdin')        self.delegate_stdout = FileDelegate(s, 'stdout')        self.delegate_stderr = FileDelegate(s, 'stderr')        self.restricted_stdin = FileWrapper(sys.stdin)        self.restricted_stdout = FileWrapper(sys.stdout)        self.restricted_stderr = FileWrapper(sys.stderr)     def set_files(self):        if not hasattr(self, 'save_stdin'):            self.save_files()        if not hasattr(self, 'delegate_stdin'):            self.make_delegate_files()        s = self.modules['sys']        s.stdin = self.restricted_stdin        s.stdout = self.restricted_stdout        s.stderr = self.restricted_stderr        sys.stdin = self.delegate_stdin        sys.stdout = self.delegate_stdout        sys.stderr = self.delegate_stderr     def reset_files(self):        self.restore_files()        s = self.modules['sys']        self.restricted_stdin = s.stdin        self.restricted_stdout = s.stdout        self.restricted_stderr = s.stderr      def save_files(self):        self.save_stdin = sys.stdin        self.save_stdout = sys.stdout        self.save_stderr = sys.stderr     def restore_files(self):        sys.stdin = self.save_stdin        sys.stdout = self.save_stdout        sys.stderr = self.save_stderr     def s_apply(self, func, args=(), kw={}):        self.save_files()        try:            self.set_files()            r = func(*args, **kw)        finally:            self.restore_files()        return r     def s_exec(self, *args):        """Execute code within a restricted environment.         Similar to the r_exec() method, but the code will be granted access        to restricted versions of the standard I/O streams sys.stdin,        sys.stderr, and sys.stdout.         The code parameter must either be a string containing one or more        lines of Python code, or a compiled code object, which will be        executed in the restricted environment's __main__ module.         """        return self.s_apply(self.r_exec, args)     def s_eval(self, *args):        """Evaluate code within a restricted environment.         Similar to the r_eval() method, but the code will be granted access        to restricted versions of the standard I/O streams sys.stdin,        sys.stderr, and sys.stdout.         The code parameter must either be a string containing a Python        expression, or a compiled code object, which will be evaluated in        the restricted environment's __main__ module.  The value of the        expression or code object will be returned.         """        return self.s_apply(self.r_eval, args)     def s_execfile(self, *args):        """Execute the Python code in the file in the restricted        environment's __main__ module.         Similar to the r_execfile() method, but the code will be granted        access to restricted versions of the standard I/O streams sys.stdin,        sys.stderr, and sys.stdout.         """        return self.s_apply(self.r_execfile, args)     def s_import(self, *args):        """Import a module, raising an ImportError exception if the module        is considered unsafe.         This method is implicitly called by code executing in the        restricted environment.  Overriding this method in a subclass is        used to change the policies enforced by a restricted environment.         Similar to the r_import() method, but has access to restricted        versions of the standard I/O streams sys.stdin, sys.stderr, and        sys.stdout.         """        return self.s_apply(self.r_import, args)     def s_reload(self, *args):        """Reload the module object, re-parsing and re-initializing it.         This method is implicitly called by code executing in the        restricted environment.  Overriding this method in a subclass is        used to change the policies enforced by a restricted environment.         Similar to the r_reload() method, but has access to restricted        versions of the standard I/O streams sys.stdin, sys.stderr, and        sys.stdout.         """        return self.s_apply(self.r_reload, args)     def s_unload(self, *args):        """Unload the module.         Removes it from the restricted environment's sys.modules dictionary.         This method is implicitly called by code executing in the        restricted environment.  Overriding this method in a subclass is        used to change the policies enforced by a restricted environment.         Similar to the r_unload() method, but has access to restricted        versions of the standard I/O streams sys.stdin, sys.stderr, and        sys.stdout. 

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