/usr/lib/python2.7/rexec.py is in libpython2.7-stdlib 2.7.6-8ubuntu0.5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 | """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 ...")?)
"""
from warnings import warnpy3k
warnpy3k("the rexec module has been removed in Python 3.0", stacklevel=2)
del warnpy3k
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', '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 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', '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 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.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):
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.
"""
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.
"""
mode = str(mode)
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 %r" % (sys.argv[0], args[0])
return 1
if fp.isatty():
try:
import readline
except ImportError:
pass
import code
class RestrictedConsole(code.InteractiveConsole):
def runcode(self, co):
self.locals['__builtins__'] = r.modules['__builtin__']
r.s_apply(code.InteractiveConsole.runcode, (self, co))
try:
RestrictedConsole(r.modules['__main__'].__dict__).interact()
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())
|