| """Restricted execution facilities. |
| |
| The class RExec exports methods r_exec(), r_eval(), r_execfile(), and |
| r_import(), which correspond roughly to the built-in operations |
| exec, eval(), execfile() and import, but executing the code in an |
| environment that only exposes those built-in operations that are |
| deemed safe. To this end, a modest collection of 'fake' modules is |
| created which mimics the standard modules by the same names. It is a |
| policy decision which built-in modules and operations are made |
| available; this module provides a reasonable default, but derived |
| classes can change the policies e.g. by overriding or extending class |
| variables 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 sys |
| import __builtin__ |
| import os |
| import ihooks |
| import imp |
| |
| __all__ = ["RExec"] |
| |
| class FileBase: |
| |
| ok_file_methods = ('fileno', 'flush', 'isatty', 'read', 'readline', |
| 'readlines', 'seek', 'tell', 'write', 'writelines') |
| |
| |
| class FileWrapper(FileBase): |
| |
| # XXX This is just like a Bastion -- should use that! |
| |
| def __init__(self, f): |
| self.f = 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 apply(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 compatibility |
| RModuleLoader = ihooks.FancyModuleLoader |
| RModuleImporter = 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', 'regex', 'pcre', 'rotor', 'select', |
| 'sha', '_sre', 'strop', 'struct', 'time') |
| |
| ok_posix_names = ('error', 'fstat', 'listdir', 'lstat', 'readlink', |
| 'stat', 'times', 'uname', 'getpid', 'getppid', |
| 'getcwd', 'getuid', 'getgid', 'geteuid', 'getegid') |
| |
| ok_sys_names = ('ps1', 'ps2', 'copyright', 'version', |
| 'platform', 'exit', 'maxint') |
| |
| 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. |
| |
| """ |
| 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): |
| if mname in self.modules: |
| return self.modules[mname] |
| 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=None): |
| self.save_files() |
| try: |
| self.set_files() |
| if kw: |
| r = apply(func, args, kw) |
| else: |
| r = apply(func, args) |
| 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. |
| |
| """ |
| return self.s_apply(self.r_unload, args) |
| |
| # Restricted open(...) |
| |
| def r_open(self, file, mode='r', buf=-1): |
| """Method called when open() is called in the restricted environment. |
| |
| The arguments are identical to those of the open() function, and a |
| file object (or a class instance compatible with file objects) |
| should be returned. RExec's default behaviour is allow opening |
| any file for reading, but forbidding any attempt to write a file. |
| |
| 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. |
| |
| """ |
| if mode not in ('r', 'rb'): |
| raise IOError, "can't open files for writing in restricted mode" |
| return open(file, mode, buf) |
| |
| # Restricted version of sys.exc_info() |
| |
| def r_exc_info(self): |
| ty, va, tr = sys.exc_info() |
| tr = None |
| return ty, va, tr |
| |
| |
| def test(): |
| import getopt, traceback |
| opts, args = getopt.getopt(sys.argv[1:], 'vt:') |
| verbose = 0 |
| trusted = [] |
| for o, a in opts: |
| if o == '-v': |
| verbose = verbose+1 |
| if o == '-t': |
| trusted.append(a) |
| r = RExec(verbose=verbose) |
| if trusted: |
| r.ok_builtin_modules = r.ok_builtin_modules + tuple(trusted) |
| if args: |
| r.modules['sys'].argv = args |
| r.modules['sys'].path.insert(0, os.path.dirname(args[0])) |
| else: |
| r.modules['sys'].path.insert(0, "") |
| fp = sys.stdin |
| if args and args[0] != '-': |
| try: |
| fp = open(args[0]) |
| except IOError, msg: |
| print "%s: can't open file %s" % (sys.argv[0], `args[0]`) |
| return 1 |
| if fp.isatty(): |
| import code |
| try: |
| code.interact( |
| "*** RESTRICTED *** Python %s on %s\n" |
| 'Type "help", "copyright", "credits" or "license" ' |
| "for more information." % (sys.version, sys.platform), |
| local=r.modules['__main__'].__dict__) |
| except SystemExit, n: |
| return n |
| else: |
| text = fp.read() |
| fp.close() |
| c = compile(text, fp.name, 'exec') |
| try: |
| r.s_exec(c) |
| except SystemExit, n: |
| return n |
| except: |
| traceback.print_exc() |
| return 1 |
| |
| |
| if __name__ == '__main__': |
| sys.exit(test()) |