16.1.2 Defining restricted environments

The RExec class has the following class attributes, which are used by the __init__() method. Changing them on an existing instance won't have any effect; instead, create a subclass of RExec and assign them new values in the class definition. Instances of the new class will then use those new values. All these attributes are tuples of strings.

nok_builtin_names: Contains the names of built-in functions which will not be available to programs running in the restricted environment. The value for RExec is ('open', 'reload', '__import__'). (This gives the exceptions, because by far the majority of built-in functions are harmless. A subclass that wants to override this variable should probably start with the value from the base class and concatenate additional forbidden functions -- when new dangerous built-in functions are added to Python, they will also be added to this module.)

ok_builtin_modules: Contains the names of built-in modules which can be safely imported. The value for RExec is ('audioop', 'array', 'binascii', 'cmath', 'errno', 'imageop', 'marshal', 'math', 'md5', 'operator', 'parser', 'regex', 'rotor', 'select', 'strop', 'struct', 'time'). A similar remark about overriding this variable applies -- use the value from the base class as a starting point.

ok_path: Contains the directories which will be searched when an import is performed in the restricted environment. The value for RExec is the same as sys.path (at the time the module is loaded) for unrestricted code.

ok_posix_names: Contains the names of the functions in the os module which will be available to programs running in the restricted environment. The value for RExec is ('error', 'fstat', 'listdir', 'lstat', 'readlink', 'stat', 'times', 'uname', 'getpid', 'getppid', 'getcwd', 'getuid', 'getgid', 'geteuid', 'getegid').

ok_sys_names: Contains the names of the functions and variables in the sys module which will be available to programs running in the restricted environment. The value for RExec is ('ps1', 'ps2', 'copyright', 'version', 'platform', 'exit', 'maxint').

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