From e0477d457e5427ecc895f60d7d7cad0f812c4eff Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>

Date: Tue, 22 Aug 2023 19:53:15 +0200

Subject: [PATCH 1/3] gh-108310: Fix CVE-2023-40217: Check for & avoid the ssl

 pre-close flaw (#108315)

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

Instances of `ssl.SSLSocket` were vulnerable to a bypass of the TLS handshake

and included protections (like certificate verification) and treating sent

unencrypted data as if it were post-handshake TLS encrypted data.

The vulnerability is caused when a socket is connected, data is sent by the

malicious peer and stored in a buffer, and then the malicious peer closes the

socket within a small timing window before the other peers’ TLS handshake can

begin. After this sequence of events the closed socket will not immediately

attempt a TLS handshake due to not being connected but will also allow the

buffered data to be read as if a successful TLS handshake had occurred.

Co-authored-by: Gregory P. Smith [Google LLC] <greg@krypto.org>

-----

Notable adjustments for Python 2.7:

Use alternative for self.getblocking(), which was added in Python 3.7

see: https://docs.python.org/3/library/socket.html#socket.socket.getblocking

Set self._sslobj early to avoid AttributeError

Use SSLError where necessary (it is not a subclass of OSError)

---

 Lib/ssl.py                                    |  32 +++

 Lib/test/test_ssl.py                          | 210 ++++++++++++++++++

 ...-08-22-17-39-12.gh-issue-108310.fVM3sg.rst |   7 +

 3 files changed, 249 insertions(+)

 create mode 100644 Misc/NEWS.d/next/Security/2023-08-22-17-39-12.gh-issue-108310.fVM3sg.rst

diff --git a/Lib/ssl.py b/Lib/ssl.py

index 5311321..9627a77 100644

--- a/Lib/ssl.py

+++ b/Lib/ssl.py

@@ -528,6 +528,7 @@ class SSLSocket(socket):

                  server_hostname=None,

                  _context=None):

+        self._sslobj = None

         self._makefile_refs = 0

         if _context:

             self._context = _context

@@ -583,6 +584,8 @@ class SSLSocket(socket):

         self.do_handshake_on_connect = do_handshake_on_connect

         self.suppress_ragged_eofs = suppress_ragged_eofs

+        sock_timeout = sock.gettimeout()

+

         # See if we are connected

         try:

             self.getpeername()

@@ -590,9 +593,38 @@ class SSLSocket(socket):

             if e.errno != errno.ENOTCONN:

                 raise

             connected = False

+            blocking = (sock.gettimeout() != 0)

+            self.setblocking(False)

+            try:

+                # We are not connected so this is not supposed to block, but

+                # testing revealed otherwise on macOS and Windows so we do

+                # the non-blocking dance regardless. Our raise when any data

+                # is found means consuming the data is harmless.

+                notconn_pre_handshake_data = self.recv(1)

+            except socket_error as e:

+                # EINVAL occurs for recv(1) on non-connected on unix sockets.

+                if e.errno not in (errno.ENOTCONN, errno.EINVAL):

+                    raise

+                notconn_pre_handshake_data = b''

+            self.setblocking(blocking)

+            if notconn_pre_handshake_data:

+                # This prevents pending data sent to the socket before it was

+                # closed from escaping to the caller who could otherwise

+                # presume it came through a successful TLS connection.

+                reason = "Closed before TLS handshake with data in recv buffer"

+                notconn_pre_handshake_data_error = SSLError(e.errno, reason)

+                # Add the SSLError attributes that _ssl.c always adds.

+                notconn_pre_handshake_data_error.reason = reason

+                notconn_pre_handshake_data_error.library = None

+                try:

+                    self.close()

+                except OSError:

+                    pass

+                raise notconn_pre_handshake_data_error

         else:

             connected = True

+        self.settimeout(sock_timeout)  # Must come after setblocking() calls.

         self._closed = False

         self._sslobj = None

         self._connected = connected

diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py

index f6b42a0..8288e0e 100644

--- a/Lib/test/test_ssl.py

+++ b/Lib/test/test_ssl.py

@@ -8,9 +8,11 @@ from test.script_helper import assert_python_ok

 import asyncore

 import socket

 import select

+import struct

 import time

 import datetime

 import gc

+import httplib

 import os

 import errno

 import pprint

@@ -2990,6 +2992,213 @@ else:

                 self.assertRaises(ValueError, s.read, 1024)

                 self.assertRaises(ValueError, s.write, b'hello')

+def set_socket_so_linger_on_with_zero_timeout(sock):

+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, struct.pack('ii', 1, 0))

+

+

+class TestPreHandshakeClose(unittest.TestCase):

+    """Verify behavior of close sockets with received data before to the handshake.

+    """

+

+    class SingleConnectionTestServerThread(threading.Thread):

+

+        def __init__(self,  name, call_after_accept):

+            self.call_after_accept = call_after_accept

+            self.received_data = b''  # set by .run()

+            self.wrap_error = None  # set by .run()

+            self.listener = None  # set by .start()

+            self.port = None  # set by .start()

+            threading.Thread.__init__(self, name=name)

+

+        def __enter__(self):

+            self.start()

+            return self

+

+        def __exit__(self, *args):

+            try:

+                if self.listener:

+                    self.listener.close()

+            except ssl.SSLError:

+                pass

+            self.join()

+            self.wrap_error = None  # avoid dangling references

+

+        def start(self):

+            self.ssl_ctx = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)

+            self.ssl_ctx.verify_mode = ssl.CERT_REQUIRED

+            self.ssl_ctx.load_verify_locations(cafile=ONLYCERT)

+            self.ssl_ctx.load_cert_chain(certfile=ONLYCERT, keyfile=ONLYKEY)

+            self.listener = socket.socket()

+            self.port = support.bind_port(self.listener)

+            self.listener.settimeout(2.0)

+            self.listener.listen(1)

+            threading.Thread.start(self)

+

+        def run(self):

+            conn, address = self.listener.accept()

+            self.listener.close()

+            with closing(conn):

+                if self.call_after_accept(conn):

+                    return

+                try:

+                    tls_socket = self.ssl_ctx.wrap_socket(conn, server_side=True)

+                except ssl.SSLError as err:

+                    self.wrap_error = err

+                else:

+                    try:

+                        self.received_data = tls_socket.recv(400)

+                    except OSError:

+                        pass  # closed, protocol error, etc.

+

+    def non_linux_skip_if_other_okay_error(self, err):

+        if sys.platform == "linux":

+            return  # Expect the full test setup to always work on Linux.

+        if (isinstance(err, ConnectionResetError) or

+            (isinstance(err, OSError) and err.errno == errno.EINVAL) or

+            re.search('wrong.version.number', getattr(err, "reason", ""), re.I)):

+            # On Windows the TCP RST leads to a ConnectionResetError

+            # (ECONNRESET) which Linux doesn't appear to surface to userspace.

+            # If wrap_socket() winds up on the "if connected:" path and doing

+            # the actual wrapping... we get an SSLError from OpenSSL. Typically

+            # WRONG_VERSION_NUMBER. While appropriate, neither is the scenario

+            # we're specifically trying to test. The way this test is written

+            # is known to work on Linux. We'll skip it anywhere else that it

+            # does not present as doing so.

+            self.skipTest("Could not recreate conditions on {}: \

+                          err={}".format(sys.platform,err))

+        # If maintaining this conditional winds up being a problem.

+        # just turn this into an unconditional skip anything but Linux.

+        # The important thing is that our CI has the logic covered.

+

+    def test_preauth_data_to_tls_server(self):

+        server_accept_called = threading.Event()

+        ready_for_server_wrap_socket = threading.Event()

+

+        def call_after_accept(unused):

+            server_accept_called.set()

+            if not ready_for_server_wrap_socket.wait(2.0):

+                raise RuntimeError("wrap_socket event never set, test may fail.")

+            return False  # Tell the server thread to continue.

+

+        server = self.SingleConnectionTestServerThread(

+                call_after_accept=call_after_accept,

+                name="preauth_data_to_tls_server")

+        server.__enter__()  # starts it

+        self.addCleanup(server.__exit__)  # ... & unittest.TestCase stops it.

+

+        with closing(socket.socket()) as client:

+            client.connect(server.listener.getsockname())

+            # This forces an immediate connection close via RST on .close().

+            set_socket_so_linger_on_with_zero_timeout(client)

+            client.setblocking(False)

+

+            server_accept_called.wait()

+            client.send(b"DELETE /data HTTP/1.0\r\n\r\n")

+            client.close()  # RST

+

+        ready_for_server_wrap_socket.set()

+        server.join()

+        wrap_error = server.wrap_error

+        self.assertEqual(b"", server.received_data)

+        self.assertIsInstance(wrap_error, ssl.SSLError)

+        self.assertIn("before TLS handshake with data", wrap_error.args[1])

+        self.assertIn("before TLS handshake with data", wrap_error.reason)

+        self.assertNotEqual(0, wrap_error.args[0])

+        self.assertIsNone(wrap_error.library, msg="attr must exist")

+

+    def test_preauth_data_to_tls_client(self):

+        client_can_continue_with_wrap_socket = threading.Event()

+

+        def call_after_accept(conn_to_client):

+            # This forces an immediate connection close via RST on .close().

+            set_socket_so_linger_on_with_zero_timeout(conn_to_client)

+            conn_to_client.send(

+                    b"HTTP/1.0 307 Temporary Redirect\r\n"

+                    b"Location: https://example.com/someone-elses-server\r\n"

+                    b"\r\n")

+            conn_to_client.close()  # RST

+            client_can_continue_with_wrap_socket.set()

+            return True  # Tell the server to stop.

+

+        server = self.SingleConnectionTestServerThread(

+                call_after_accept=call_after_accept,

+                name="preauth_data_to_tls_client")

+        server.__enter__()  # starts it

+        self.addCleanup(server.__exit__)  # ... & unittest.TestCase stops it.

+

+        # Redundant; call_after_accept sets SO_LINGER on the accepted conn.

+        set_socket_so_linger_on_with_zero_timeout(server.listener)

+

+        with closing(socket.socket()) as client:

+            client.connect(server.listener.getsockname())

+            if not client_can_continue_with_wrap_socket.wait(2.0):

+                self.fail("test server took too long.")

+            ssl_ctx = ssl.create_default_context()

+            try:

+                tls_client = ssl_ctx.wrap_socket(

+                        client, server_hostname="localhost")

+            except ssl.SSLError as err:

+                wrap_error = err

+                received_data = b""

+            else:

+                wrap_error = None

+                received_data = tls_client.recv(400)

+                tls_client.close()

+

+        server.join()

+        self.assertEqual(b"", received_data)

+        self.assertIsInstance(wrap_error, ssl.SSLError)

+        self.assertIn("before TLS handshake with data", wrap_error.args[1])

+        self.assertIn("before TLS handshake with data", wrap_error.reason)

+        self.assertNotEqual(0, wrap_error.args[0])

+        self.assertIsNone(wrap_error.library, msg="attr must exist")

+

+    def test_https_client_non_tls_response_ignored(self):

+

+        server_responding = threading.Event()

+

+        class SynchronizedHTTPSConnection(httplib.HTTPSConnection):

+            def connect(self):

+                httplib.HTTPConnection.connect(self)

+                # Wait for our fault injection server to have done its thing.

+                if not server_responding.wait(1.0) and support.verbose:

+                    sys.stdout.write("server_responding event never set.")

+                self.sock = self._context.wrap_socket(

+                        self.sock, server_hostname=self.host)

+

+        def call_after_accept(conn_to_client):

+            # This forces an immediate connection close via RST on .close().

+            set_socket_so_linger_on_with_zero_timeout(conn_to_client)

+            conn_to_client.send(

+                    b"HTTP/1.0 402 Payment Required\r\n"

+                    b"\r\n")

+            conn_to_client.close()  # RST

+            server_responding.set()

+            return True  # Tell the server to stop.

+

+        server = self.SingleConnectionTestServerThread(

+                call_after_accept=call_after_accept,

+                name="non_tls_http_RST_responder")

+        server.__enter__()  # starts it

+        self.addCleanup(server.__exit__)  # ... & unittest.TestCase stops it.

+        # Redundant; call_after_accept sets SO_LINGER on the accepted conn.

+        set_socket_so_linger_on_with_zero_timeout(server.listener)

+

+        connection = SynchronizedHTTPSConnection(

+                "localhost",

+                port=server.port,

+                context=ssl.create_default_context(),

+                timeout=2.0,

+        )

+        # There are lots of reasons this raises as desired, long before this

+        # test was added. Sending the request requires a successful TLS wrapped

+        # socket; that fails if the connection is broken. It may seem pointless

+        # to test this. It serves as an illustration of something that we never

+        # want to happen... properly not happening.

+        with self.assertRaises(ssl.SSLError) as err_ctx:

+            connection.request("HEAD", "/test", headers={"Host": "localhost"})

+            response = connection.getresponse()

+

 def test_main(verbose=False):

     if support.verbose:

@@ -3024,6 +3233,7 @@ def test_main(verbose=False):

             raise support.TestFailed("Can't read certificate file %r" % filename)

     tests = [ContextTests, BasicTests, BasicSocketTests, SSLErrorTests]

+    tests += [TestPreHandshakeClose]

     if support.is_resource_enabled('network'):

         tests.append(NetworkedTests)

diff --git a/Misc/NEWS.d/next/Security/2023-08-22-17-39-12.gh-issue-108310.fVM3sg.rst b/Misc/NEWS.d/next/Security/2023-08-22-17-39-12.gh-issue-108310.fVM3sg.rst

new file mode 100644

index 0000000..403c77a

--- /dev/null

+++ b/Misc/NEWS.d/next/Security/2023-08-22-17-39-12.gh-issue-108310.fVM3sg.rst

@@ -0,0 +1,7 @@

+Fixed an issue where instances of :class:`ssl.SSLSocket` were vulnerable to

+a bypass of the TLS handshake and included protections (like certificate

+verification) and treating sent unencrypted data as if it were

+post-handshake TLS encrypted data.  Security issue reported as

+`CVE-2023-40217

+<https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-40217>`_ by

+Aapo Oksman. Patch by Gregory P. Smith.

-- 

2.41.0

From 82032d4fb71fb3a6e7c364b6e93c2c33ff49b1a5 Mon Sep 17 00:00:00 2001

From: "Miss Islington (bot)"

 <31488909+miss-islington@users.noreply.github.com>

Date: Wed, 23 Aug 2023 03:10:56 -0700

Subject: [PATCH 2/3] gh-108342: Break ref cycle in SSLSocket._create() exc

 (GH-108344) (#108352)

Explicitly break a reference cycle when SSLSocket._create() raises an

exception. Clear the variable storing the exception, since the

exception traceback contains the variables and so creates a reference

cycle.

This test leak was introduced by the test added for the fix of GH-108310.

(cherry picked from commit 64f99350351bc46e016b2286f36ba7cd669b79e3)

Co-authored-by: Victor Stinner <vstinner@python.org>

---

 Lib/ssl.py | 6 +++++-

 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Lib/ssl.py b/Lib/ssl.py

index 9627a77..ee3806e 100644

--- a/Lib/ssl.py

+++ b/Lib/ssl.py

@@ -620,7 +620,11 @@ class SSLSocket(socket):

                     self.close()

                 except OSError:

                     pass

-                raise notconn_pre_handshake_data_error

+                try:

+                    raise notconn_pre_handshake_data_error

+                finally:

+                    # Explicitly break the reference cycle.

+                    notconn_pre_handshake_data_error = None

         else:

             connected = True

-- 

2.41.0

From 960d54566e3da48e9dde1e9c1bd74c89c277244b Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>

Date: Thu, 24 Aug 2023 12:09:30 +0200

Subject: [PATCH 3/3] gh-108342: Make ssl TestPreHandshakeClose more reliable

 (GH-108370) (#108408)

* In preauth tests of test_ssl, explicitly break reference cycles

  invoving SingleConnectionTestServerThread to make sure that the

  thread is deleted. Otherwise, the test marks the environment as

  altered because the threading module sees a "dangling thread"

  (SingleConnectionTestServerThread). This test leak was introduced

  by the test added for the fix of issue gh-108310.

* Use support.SHORT_TIMEOUT instead of hardcoded 1.0 or 2.0 seconds

  timeout.

* SingleConnectionTestServerThread.run() catchs TimeoutError

* Fix a race condition (missing synchronization) in

  test_preauth_data_to_tls_client(): the server now waits until the

  client connect() completed in call_after_accept().

* test_https_client_non_tls_response_ignored() calls server.join()

  explicitly.

* Replace "localhost" with server.listener.getsockname()[0].

(cherry picked from commit 592bacb6fc0833336c0453e818e9b95016e9fd47)

---

 Lib/test/test_ssl.py     | 105 ++++++++++++++++++++++-----------------

 Lib/test/test_support.py |   2 +

 2 files changed, 62 insertions(+), 45 deletions(-)

diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py

index 8288e0e..7795627 100644

--- a/Lib/test/test_ssl.py

+++ b/Lib/test/test_ssl.py

@@ -3002,12 +3002,16 @@ class TestPreHandshakeClose(unittest.TestCase):

     class SingleConnectionTestServerThread(threading.Thread):

-        def __init__(self,  name, call_after_accept):

+        def __init__(self,  name, call_after_accept, timeout=None):

             self.call_after_accept = call_after_accept

             self.received_data = b''  # set by .run()

             self.wrap_error = None  # set by .run()

             self.listener = None  # set by .start()

             self.port = None  # set by .start()

+            if timeout is None:

+                self.timeout = support.SHORT_TIMEOUT

+            else:

+                self.timeout = timeout

             threading.Thread.__init__(self, name=name)

         def __enter__(self):

@@ -3030,13 +3034,22 @@ class TestPreHandshakeClose(unittest.TestCase):

             self.ssl_ctx.load_cert_chain(certfile=ONLYCERT, keyfile=ONLYKEY)

             self.listener = socket.socket()

             self.port = support.bind_port(self.listener)

-            self.listener.settimeout(2.0)

+            self.listener.settimeout(self.timeout)

             self.listener.listen(1)

             threading.Thread.start(self)

         def run(self):

-            conn, address = self.listener.accept()

-            self.listener.close()

+            try:

+                conn, address = self.listener.accept()

+            except OSError as e:

+                if e.errno == errno.ETIMEDOUT:

+                    # on timeout, just close the listener

+                    return

+                else:

+                    raise

+            finally:

+                self.listener.close()

+

             with closing(conn):

                 if self.call_after_accept(conn):

                     return

@@ -3050,33 +3063,13 @@ class TestPreHandshakeClose(unittest.TestCase):

                     except OSError:

                         pass  # closed, protocol error, etc.

-    def non_linux_skip_if_other_okay_error(self, err):

-        if sys.platform == "linux":

-            return  # Expect the full test setup to always work on Linux.

-        if (isinstance(err, ConnectionResetError) or

-            (isinstance(err, OSError) and err.errno == errno.EINVAL) or

-            re.search('wrong.version.number', getattr(err, "reason", ""), re.I)):

-            # On Windows the TCP RST leads to a ConnectionResetError

-            # (ECONNRESET) which Linux doesn't appear to surface to userspace.

-            # If wrap_socket() winds up on the "if connected:" path and doing

-            # the actual wrapping... we get an SSLError from OpenSSL. Typically

-            # WRONG_VERSION_NUMBER. While appropriate, neither is the scenario

-            # we're specifically trying to test. The way this test is written

-            # is known to work on Linux. We'll skip it anywhere else that it

-            # does not present as doing so.

-            self.skipTest("Could not recreate conditions on {}: \

-                          err={}".format(sys.platform,err))

-        # If maintaining this conditional winds up being a problem.

-        # just turn this into an unconditional skip anything but Linux.

-        # The important thing is that our CI has the logic covered.

-

     def test_preauth_data_to_tls_server(self):

         server_accept_called = threading.Event()

         ready_for_server_wrap_socket = threading.Event()

         def call_after_accept(unused):

             server_accept_called.set()

-            if not ready_for_server_wrap_socket.wait(2.0):

+            if not ready_for_server_wrap_socket.wait(support.SHORT_TIMEOUT):

                 raise RuntimeError("wrap_socket event never set, test may fail.")

             return False  # Tell the server thread to continue.

@@ -3098,18 +3091,28 @@ class TestPreHandshakeClose(unittest.TestCase):

         ready_for_server_wrap_socket.set()

         server.join()

+

         wrap_error = server.wrap_error

-        self.assertEqual(b"", server.received_data)

-        self.assertIsInstance(wrap_error, ssl.SSLError)

-        self.assertIn("before TLS handshake with data", wrap_error.args[1])

-        self.assertIn("before TLS handshake with data", wrap_error.reason)

-        self.assertNotEqual(0, wrap_error.args[0])

-        self.assertIsNone(wrap_error.library, msg="attr must exist")

+        try:

+            self.assertEqual(b"", server.received_data)

+            self.assertIsInstance(wrap_error, ssl.SSLError)

+            self.assertIn("before TLS handshake with data", wrap_error.args[1])

+            self.assertIn("before TLS handshake with data", wrap_error.reason)

+            self.assertNotEqual(0, wrap_error.args[0])

+            self.assertIsNone(wrap_error.library, msg="attr must exist")

+        finally:

+            # gh-108342: Explicitly break the reference cycle

+            wrap_error = None

+            server = None

     def test_preauth_data_to_tls_client(self):

+        server_can_continue_with_wrap_socket = threading.Event()

         client_can_continue_with_wrap_socket = threading.Event()

         def call_after_accept(conn_to_client):

+            if not server_can_continue_with_wrap_socket.wait(support.SHORT_TIMEOUT):

+                print("ERROR: test client took too long")

+

             # This forces an immediate connection close via RST on .close().

             set_socket_so_linger_on_with_zero_timeout(conn_to_client)

             conn_to_client.send(

@@ -3131,8 +3134,10 @@ class TestPreHandshakeClose(unittest.TestCase):

         with closing(socket.socket()) as client:

             client.connect(server.listener.getsockname())

-            if not client_can_continue_with_wrap_socket.wait(2.0):

-                self.fail("test server took too long.")

+            server_can_continue_with_wrap_socket.set()

+

+            if not client_can_continue_with_wrap_socket.wait(support.SHORT_TIMEOUT):

+                self.fail("test server took too long")

             ssl_ctx = ssl.create_default_context()

             try:

                 tls_client = ssl_ctx.wrap_socket(

@@ -3146,22 +3151,29 @@ class TestPreHandshakeClose(unittest.TestCase):

                 tls_client.close()

         server.join()

-        self.assertEqual(b"", received_data)

-        self.assertIsInstance(wrap_error, ssl.SSLError)

-        self.assertIn("before TLS handshake with data", wrap_error.args[1])

-        self.assertIn("before TLS handshake with data", wrap_error.reason)

-        self.assertNotEqual(0, wrap_error.args[0])

-        self.assertIsNone(wrap_error.library, msg="attr must exist")

+        try:

+            self.assertEqual(b"", received_data)

+            self.assertIsInstance(wrap_error, ssl.SSLError)

+            self.assertIn("before TLS handshake with data", wrap_error.args[1])

+            self.assertIn("before TLS handshake with data", wrap_error.reason)

+            self.assertNotEqual(0, wrap_error.args[0])

+            self.assertIsNone(wrap_error.library, msg="attr must exist")

+        finally:

+            # gh-108342: Explicitly break the reference cycle

+            wrap_error = None

+            server = None

     def test_https_client_non_tls_response_ignored(self):

-

         server_responding = threading.Event()

         class SynchronizedHTTPSConnection(httplib.HTTPSConnection):

             def connect(self):

+                # Call clear text HTTP connect(), not the encrypted HTTPS (TLS)

+                # connect(): wrap_socket() is called manually below.

                 httplib.HTTPConnection.connect(self)

+

                 # Wait for our fault injection server to have done its thing.

-                if not server_responding.wait(1.0) and support.verbose:

+                if not server_responding.wait(support.SHORT_TIMEOUT) and support.verbose:

                     sys.stdout.write("server_responding event never set.")

                 self.sock = self._context.wrap_socket(

                         self.sock, server_hostname=self.host)

@@ -3176,29 +3188,32 @@ class TestPreHandshakeClose(unittest.TestCase):

             server_responding.set()

             return True  # Tell the server to stop.

+        timeout = 2.0

         server = self.SingleConnectionTestServerThread(

                 call_after_accept=call_after_accept,

-                name="non_tls_http_RST_responder")

+                name="non_tls_http_RST_responder",

+                timeout=timeout)

         server.__enter__()  # starts it

         self.addCleanup(server.__exit__)  # ... & unittest.TestCase stops it.

         # Redundant; call_after_accept sets SO_LINGER on the accepted conn.

         set_socket_so_linger_on_with_zero_timeout(server.listener)

         connection = SynchronizedHTTPSConnection(

-                "localhost",

+                server.listener.getsockname()[0],

                 port=server.port,

                 context=ssl.create_default_context(),

-                timeout=2.0,

+                timeout=timeout,

         )

         # There are lots of reasons this raises as desired, long before this

         # test was added. Sending the request requires a successful TLS wrapped

         # socket; that fails if the connection is broken. It may seem pointless

         # to test this. It serves as an illustration of something that we never

         # want to happen... properly not happening.

-        with self.assertRaises(ssl.SSLError) as err_ctx:

+        with self.assertRaises(ssl.SSLError):

             connection.request("HEAD", "/test", headers={"Host": "localhost"})

             response = connection.getresponse()

+        server.join()

 def test_main(verbose=False):

     if support.verbose:

diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py

index 98a9275..1536606 100644

--- a/Lib/test/test_support.py

+++ b/Lib/test/test_support.py

@@ -42,6 +42,8 @@ __all__ = ["Error", "TestFailed", "ResourceDenied", "import_module",

            "import_fresh_module", "threading_cleanup", "reap_children",

            "strip_python_stderr", "IPV6_ENABLED"]

+SHORT_TIMEOUT = 30.0  # Added to make backporting from 3.x easier

+

 class Error(Exception):

     """Base class for regression test exceptions."""

-- 

2.41.0