"""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().
- r_open should allow writing tmp dir
- r_exec etc. with explicit globals/locals? (Use rexec("exec ... in ...")?)
from warnings import warnpy3k
warnpy3k("the rexec module has been removed in Python 3.0", stacklevel=2)
ok_file_methods = ('fileno', 'flush', 'isatty', 'read', 'readline',
'readlines', 'seek', 'tell', 'write', 'writelines', 'xreadlines',
class FileWrapper(FileBase):
# XXX This is just like a Bastion -- should use that!
for m in self.ok_file_methods:
if not hasattr(self, m) and hasattr(f, m):
setattr(self, m, getattr(f, m))
return getattr(self.mod, self.name).%s(*args)
class FileDelegate(FileBase):
def __init__(self, mod, name):
for m in FileBase.ok_file_methods + ('close',):
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])
if args and type(args[-1]) == type(0):
if args and hasattr(args[0], '__class__'):
raise TypeError, "too many arguments"
ihooks.Hooks.__init__(self, verbose)
def set_rexec(self, rexec):
# Called by RExec instance to complete initialization
return self.rexec.get_suffixes()
def is_builtin(self, name):
return self.rexec.is_builtin(name)
def init_builtin(self, 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)
return self.rexec.modules
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
ok_path = tuple(sys.path) # That's a policy decision
ok_builtin_modules = ('audioop', 'array', 'binascii',
'cmath', 'errno', 'imageop',
'marshal', 'math', 'md5', 'operator',
'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 = ('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
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
raise RuntimeError, "This code is not secure in Python 2.2 and later"
ihooks._Verbose.__init__(self, verbose)
# XXX There's a circular reference here:
self.hooks = hooks or RHooks(verbose)
self.hooks.set_rexec(self)
self.ok_dynamic_modules = self.ok_builtin_modules
for mname in self.ok_builtin_modules:
if mname in sys.builtin_module_names:
self.ok_builtin_modules = tuple(list)
self.make_initial_modules()
# make_sys must be last because it adds the already created
# modules to its builtin_module_names
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
src = imp.load_dynamic(name, filename, file)
dst = self.copy_except(src, [])
def make_initial_modules(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
m = self.copy_except(__builtin__, self.nok_builtin_names)
m.__import__ = self.r_import
m.open = m.file = self.r_open
self.add_module('__main__')
dst = self.copy_only(src, self.ok_posix_names)
for key, value in os.environ.items():
m = self.copy_only(sys, self.ok_sys_names)
m.path = map(None, self.ok_path)
m.exc_info = self.r_exc_info
l = self.modules.keys() + list(self.ok_builtin_modules)
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)
setattr(dst, name, getattr(src, name))
def copy_only(self, src, names):
dst = self.copy_none(src)
value = getattr(src, name)
setattr(dst, name, value)
def copy_none(self, src):
m = self.add_module(src.__name__)
# Add a module -- return an existing module or create one
def add_module(self, mname):
m = self.modules.get(mname)
self.modules[mname] = m = self.hooks.new_module(mname)
m.__builtins__ = self.modules['__builtin__']
# The r* methods are public interfaces
"""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__')
"""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
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)
"""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)
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):
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)
if not hasattr(self, 'save_stdin'):
if not hasattr(self, 'delegate_stdin'):
self.make_delegate_files()
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
self.restricted_stdin = s.stdin
self.restricted_stdout = s.stdout
self.restricted_stderr = s.stderr
self.save_stdin = sys.stdin
self.save_stdout = sys.stdout
self.save_stderr = sys.stderr
sys.stdin = self.save_stdin
sys.stdout = self.save_stdout
sys.stderr = self.save_stderr
def s_apply(self, func, args=(), kw={}):
"""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)
"""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
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
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
return self.s_apply(self.r_reload, args)
def s_unload(self, *args):
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
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
