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bpo-37228: Fix loop.create_datagram_endpoint()'s usage of SO_REUSEADDR (#17311)

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This commit is contained in:
Kyle Stanley 2019-12-09 09:21:10 -05:00 committed by Łukasz Langa
parent 82b4950b5e
commit ab513a38c9
4 changed files with 67 additions and 29 deletions
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24
Doc/library/asyncio-eventloop.rst
View File

@ -473,6 +473,21 @@ Opening network connections
reuse_address=None, reuse_port=None, \
allow_broadcast=None, sock=None)
.. note::
The parameter *reuse_address* is no longer supported, as using
:py:data:`~sockets.SO_REUSEADDR` poses a significant security concern for
UDP. Explicitly passing ``reuse_address=True`` will raise an exception.
When multiple processes with differing UIDs assign sockets to an
indentical UDP socket address with ``SO_REUSEADDR``, incoming packets can
become randomly distributed among the sockets.
For supported platforms, *reuse_port* can be used as a replacement for
similar functionality. With *reuse_port*,
:py:data:`~sockets.SO_REUSEPORT` is used instead, which specifically
prevents processes with differing UIDs from assigning sockets to the same
socket address.
Create a datagram connection.
The socket family can be either :py:data:`~socket.AF_INET`,
@ -501,11 +516,6 @@ Opening network connections
resolution. If given, these should all be integers from the
corresponding :mod:`socket` module constants.
* *reuse_address* tells the kernel to reuse a local socket in
``TIME_WAIT`` state, without waiting for its natural timeout to
expire. If not specified will automatically be set to ``True`` on
Unix.
* *reuse_port* tells the kernel to allow this endpoint to be bound to the
same port as other existing endpoints are bound to, so long as they all
set this flag when being created. This option is not supported on Windows
@ -527,6 +537,10 @@ Opening network connections
The *family*, *proto*, *flags*, *reuse_address*, *reuse_port,
*allow_broadcast*, and *sock* parameters were added.
.. versionchanged:: 3.8.1
The *reuse_address* parameter is no longer supported due to security
concerns.
.. versionchanged:: 3.8
Added support for Windows.

25
Lib/asyncio/base_events.py
View File

@ -66,6 +66,10 @@ _HAS_IPv6 = hasattr(socket, 'AF_INET6')
# Maximum timeout passed to select to avoid OS limitations
MAXIMUM_SELECT_TIMEOUT = 24 * 3600
# Used for deprecation and removal of `loop.create_datagram_endpoint()`'s
# *reuse_address* parameter
_unset = object()
def _format_handle(handle):
cb = handle._callback
@ -1230,7 +1234,7 @@ class BaseEventLoop(events.AbstractEventLoop):
async def create_datagram_endpoint(self, protocol_factory,
local_addr=None, remote_addr=None, *,
family=0, proto=0, flags=0,
reuse_address=None, reuse_port=None,
reuse_address=_unset, reuse_port=None,
allow_broadcast=None, sock=None):
"""Create datagram connection."""
if sock is not None:
@ -1239,7 +1243,7 @@ class BaseEventLoop(events.AbstractEventLoop):
f'A UDP Socket was expected, got {sock!r}')
if (local_addr or remote_addr or
family or proto or flags or
reuse_address or reuse_port or allow_broadcast):
reuse_port or allow_broadcast):
# show the problematic kwargs in exception msg
opts = dict(local_addr=local_addr, remote_addr=remote_addr,
family=family, proto=proto, flags=flags,
@ -1306,8 +1310,18 @@ class BaseEventLoop(events.AbstractEventLoop):
exceptions = []
if reuse_address is None:
reuse_address = os.name == 'posix' and sys.platform != 'cygwin'
# bpo-37228
if reuse_address is not _unset:
if reuse_address:
raise ValueError("Passing `reuse_address=True` is no "
"longer supported, as the usage of "
"SO_REUSEPORT in UDP poses a significant "
"security concern.")
else:
warnings.warn("The *reuse_address* parameter has been "
"deprecated as of 3.5.10 and is scheduled "
"for removal in 3.11.", DeprecationWarning,
stacklevel=2)
for ((family, proto),
(local_address, remote_address)) in addr_pairs_info:
@ -1316,9 +1330,6 @@ class BaseEventLoop(events.AbstractEventLoop):
try:
sock = socket.socket(
family=family, type=socket.SOCK_DGRAM, proto=proto)
if reuse_address:
sock.setsockopt(
socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
if reuse_port:
_set_reuseport(sock)
if allow_broadcast:

41
Lib/test/test_asyncio/test_base_events.py
View File

@ -1738,10 +1738,6 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
MyDatagramProto, flags=1, sock=FakeSock())
self.assertRaises(ValueError, self.loop.run_until_complete, fut)
fut = self.loop.create_datagram_endpoint(
MyDatagramProto, reuse_address=True, sock=FakeSock())
self.assertRaises(ValueError, self.loop.run_until_complete, fut)
fut = self.loop.create_datagram_endpoint(
MyDatagramProto, reuse_port=True, sock=FakeSock())
self.assertRaises(ValueError, self.loop.run_until_complete, fut)
@ -1752,7 +1748,6 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
def test_create_datagram_endpoint_sockopts(self):
# Socket options should not be applied unless asked for.
# SO_REUSEADDR defaults to on for UNIX.
# SO_REUSEPORT is not available on all platforms.
coro = self.loop.create_datagram_endpoint(
@ -1761,18 +1756,8 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
transport, protocol = self.loop.run_until_complete(coro)
sock = transport.get_extra_info('socket')
reuse_address_default_on = (
os.name == 'posix' and sys.platform != 'cygwin')
reuseport_supported = hasattr(socket, 'SO_REUSEPORT')
if reuse_address_default_on:
self.assertTrue(
sock.getsockopt(
socket.SOL_SOCKET, socket.SO_REUSEADDR))
else:
self.assertFalse(
sock.getsockopt(
socket.SOL_SOCKET, socket.SO_REUSEADDR))
if reuseport_supported:
self.assertFalse(
sock.getsockopt(
@ -1788,13 +1773,12 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
coro = self.loop.create_datagram_endpoint(
lambda: MyDatagramProto(create_future=True, loop=self.loop),
local_addr=('127.0.0.1', 0),
reuse_address=True,
reuse_port=reuseport_supported,
allow_broadcast=True)
transport, protocol = self.loop.run_until_complete(coro)
sock = transport.get_extra_info('socket')
self.assertTrue(
self.assertFalse(
sock.getsockopt(
socket.SOL_SOCKET, socket.SO_REUSEADDR))
if reuseport_supported:
@ -1809,6 +1793,29 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
self.loop.run_until_complete(protocol.done)
self.assertEqual('CLOSED', protocol.state)
def test_create_datagram_endpoint_reuse_address_error(self):
# bpo-37228: Ensure that explicit passing of `reuse_address=True`
# raises an error, as it is not safe to use SO_REUSEADDR when using UDP
coro = self.loop.create_datagram_endpoint(
lambda: MyDatagramProto(create_future=True, loop=self.loop),
local_addr=('127.0.0.1', 0),
reuse_address=True)
with self.assertRaises(ValueError):
self.loop.run_until_complete(coro)
def test_create_datagram_endpoint_reuse_address_warning(self):
# bpo-37228: Deprecate *reuse_address* parameter
coro = self.loop.create_datagram_endpoint(
lambda: MyDatagramProto(create_future=True, loop=self.loop),
local_addr=('127.0.0.1', 0),
reuse_address=False)
with self.assertWarns(DeprecationWarning):
self.loop.run_until_complete(coro)
@patch_socket
def test_create_datagram_endpoint_nosoreuseport(self, m_socket):
del m_socket.SO_REUSEPORT

6
Misc/NEWS.d/next/Security/2019-11-21-21-36-54.bpo-37228.yBZnFG.rst Normal file
View File

@ -0,0 +1,6 @@
Due to significant security concerns, the *reuse_address* parameter of
:meth:`asyncio.loop.create_datagram_endpoint` is no longer supported. This is
because of the behavior of ``SO_REUSEADDR`` in UDP. For more details, see the
documentation for ``loop.create_datagram_endpoint()``.
(Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
:issue:`37228`.)