"""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
__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 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):
"""Restricted Execution environment."""
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',
'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', 'reload', '__import__')
def __init__(self, hooks = None, verbose = 0):
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)
# but since re isn't normally built-in, we can add it at the end;
# we need the imported to be set before this can be imported.
self.make_re()
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 sys.modules.has_key(name):
src = sys.modules[name]
else:
import imp
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 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 = 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_re(self):
dst = self.add_module("re")
src = self.r_import("pre")
for name in dir(src):
if name != "__name__":
setattr(dst, name, getattr(src, name))
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 self.modules.has_key(mname):
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):
m = self.add_module('__main__')
exec code in m.__dict__
def r_eval(self, code):
m = self.add_module('__main__')
return eval(code, m.__dict__)
def r_execfile(self, file):
m = self.add_module('__main__')
return execfile(file, m.__dict__)
def r_import(self, mname, globals={}, locals={}, fromlist=[]):
return self.importer.import_module(mname, globals, locals, fromlist)
def r_reload(self, m):
return self.importer.reload(m)
def r_unload(self, m):
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):
return self.s_apply(self.r_exec, args)
def s_eval(self, *args):
return self.s_apply(self.r_eval, args)
def s_execfile(self, *args):
return self.s_apply(self.r_execfile, args)
def s_import(self, *args):
return self.s_apply(self.r_import, args)
def s_reload(self, *args):
return self.s_apply(self.r_reload, args)
def s_unload(self, *args):
return self.s_apply(self.r_unload, args)
# Restricted open(...)
def r_open(self, file, mode='r', buf=-1):
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 sys, 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():
print "*** RESTRICTED *** Python", sys.version
print sys.copyright
while 1:
try:
try:
s = raw_input('>>> ')
except EOFError:
print
break
if s and s[0] != '#':
s = s + '\n'
c = compile(s, '<stdin>', 'single')
r.s_exec(c)
except SystemExit, n:
return n
except:
traceback.print_exc()
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())
|