bpo-32947: OpenSSL 1.1.1-pre1 / TLS 1.3 fixes (#5663)

* bpo-32947: OpenSSL 1.1.1-pre1 / TLS 1.3 fixes

Misc fixes and workarounds for compatibility with OpenSSL 1.1.1-pre1 and
TLS 1.3 support. With OpenSSL 1.1.1, Python negotiates TLS 1.3 by
default. Some test cases only apply to TLS 1.2. Other tests currently
fail because the threaded or async test servers stop after failure.

I'm going to address these issues when OpenSSL 1.1.1 reaches beta.

OpenSSL 1.1.1 has added a new option OP_ENABLE_MIDDLEBOX_COMPAT for TLS
1.3. The feature is enabled by default for maximum compatibility with
broken middle boxes. Users should be able to disable the hack and CPython's test suite needs
it to verify default options.
Signed-off-by: Christian Heimes <christian@python.org>

Doc/library/ssl.rst

@@ -831,6 +831,15 @@ Constants
 
    .. versionadded:: 3.3
 
+.. data:: OP_ENABLE_MIDDLEBOX_COMPAT
+
+   Send dummy Change Cipher Spec (CCS) messages in TLS 1.3 handshake to make
+   a TLS 1.3 connection look more like a TLS 1.2 connection.
+
+   This option is only available with OpenSSL 1.1.1 and later.
+
+   .. versionadded:: 3.8
+
 .. data:: OP_NO_COMPRESSION
 
    Disable compression on the SSL channel.  This is useful if the application

Doc/whatsnew/3.7.rst

@@ -669,6 +669,9 @@ expected hostname in A-label form (``"xn--pythn-mua.org"``), rather
 than the U-label form (``"pythön.org"``). (Contributed by
 Nathaniel J. Smith and Christian Heimes in :issue:`28414`.)
 
+The ssl module has preliminary and experimental support for TLS 1.3 and
+OpenSSL 1.1.1. (Contributed by Christian Heimes in :issue:`32947`,
+:issue:`20995`, :issue:`29136`, and :issue:`30622`)
 
 string
 ------

Lib/test/test_asyncio/utils.py

@@ -74,6 +74,8 @@ def simple_server_sslcontext():
     server_context.load_cert_chain(ONLYCERT, ONLYKEY)
     server_context.check_hostname = False
     server_context.verify_mode = ssl.CERT_NONE
+    # TODO: fix TLSv1.3 support
+    server_context.options |= ssl.OP_NO_TLSv1_3
     return server_context
 
 

Lib/test/test_ftplib.py

@@ -312,6 +312,8 @@ if ssl is not None:
 
         def secure_connection(self):
             context = ssl.SSLContext()
+            # TODO: fix TLSv1.3 support
+            context.options |= ssl.OP_NO_TLSv1_3
             context.load_cert_chain(CERTFILE)
             socket = context.wrap_socket(self.socket,
                                          suppress_ragged_eofs=False,
@@ -908,6 +910,8 @@ class TestTLS_FTPClass(TestCase):
     def test_context(self):
         self.client.quit()
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        # TODO: fix TLSv1.3 support
+        ctx.options |= ssl.OP_NO_TLSv1_3
         ctx.check_hostname = False
         ctx.verify_mode = ssl.CERT_NONE
         self.assertRaises(ValueError, ftplib.FTP_TLS, keyfile=CERTFILE,
@@ -940,6 +944,8 @@ class TestTLS_FTPClass(TestCase):
     def test_check_hostname(self):
         self.client.quit()
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        # TODO: fix TLSv1.3 support
+        ctx.options |= ssl.OP_NO_TLSv1_3
         self.assertEqual(ctx.verify_mode, ssl.CERT_REQUIRED)
         self.assertEqual(ctx.check_hostname, True)
         ctx.load_verify_locations(CAFILE)

Lib/test/test_poplib.py

@@ -153,6 +153,8 @@ class DummyPOP3Handler(asynchat.async_chat):
             if self.tls_active is False:
                 self.push('+OK Begin TLS negotiation')
                 context = ssl.SSLContext()
+                # TODO: fix TLSv1.3 support
+                context.options |= ssl.OP_NO_TLSv1_3
                 context.load_cert_chain(CERTFILE)
                 tls_sock = context.wrap_socket(self.socket,
                                                server_side=True,
@@ -356,6 +358,8 @@ class TestPOP3Class(TestCase):
     def test_stls_context(self):
         expected = b'+OK Begin TLS negotiation'
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        # TODO: fix TLSv1.3 support
+        ctx.options |= ssl.OP_NO_TLSv1_3
         ctx.load_verify_locations(CAFILE)
         self.assertEqual(ctx.verify_mode, ssl.CERT_REQUIRED)
         self.assertEqual(ctx.check_hostname, True)
@@ -396,6 +400,8 @@ class TestPOP3_SSLClass(TestPOP3Class):
 
     def test_context(self):
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        # TODO: fix TLSv1.3 support
+        ctx.options |= ssl.OP_NO_TLSv1_3
         ctx.check_hostname = False
         ctx.verify_mode = ssl.CERT_NONE
         self.assertRaises(ValueError, poplib.POP3_SSL, self.server.host,

Lib/test/test_ssl.py

@@ -30,7 +30,8 @@ ssl = support.import_module("ssl")
 PROTOCOLS = sorted(ssl._PROTOCOL_NAMES)
 HOST = support.HOST
 IS_LIBRESSL = ssl.OPENSSL_VERSION.startswith('LibreSSL')
-IS_OPENSSL_1_1 = not IS_LIBRESSL and ssl.OPENSSL_VERSION_INFO >= (1, 1, 0)
+IS_OPENSSL_1_1_0 = not IS_LIBRESSL and ssl.OPENSSL_VERSION_INFO >= (1, 1, 0)
+IS_OPENSSL_1_1_1 = not IS_LIBRESSL and ssl.OPENSSL_VERSION_INFO >= (1, 1, 1)
 PY_SSL_DEFAULT_CIPHERS = sysconfig.get_config_var('PY_SSL_DEFAULT_CIPHERS')
 
 def data_file(*name):
@@ -54,6 +55,7 @@ CAPATH = data_file("capath")
 BYTES_CAPATH = os.fsencode(CAPATH)
 CAFILE_NEURONIO = data_file("capath", "4e1295a3.0")
 CAFILE_CACERT = data_file("capath", "5ed36f99.0")
+WRONG_CERT = data_file("wrongcert.pem")
 
 CERTFILE_INFO = {
     'issuer': ((('countryName', 'XY'),),
@@ -124,6 +126,7 @@ OP_NO_COMPRESSION = getattr(ssl, "OP_NO_COMPRESSION", 0)
 OP_SINGLE_DH_USE = getattr(ssl, "OP_SINGLE_DH_USE", 0)
 OP_SINGLE_ECDH_USE = getattr(ssl, "OP_SINGLE_ECDH_USE", 0)
 OP_CIPHER_SERVER_PREFERENCE = getattr(ssl, "OP_CIPHER_SERVER_PREFERENCE", 0)
+OP_ENABLE_MIDDLEBOX_COMPAT = getattr(ssl, "OP_ENABLE_MIDDLEBOX_COMPAT", 0)
 
 
 def handle_error(prefix):
@@ -232,6 +235,7 @@ def testing_context(server_cert=SIGNED_CERTFILE):
 
     server_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
     server_context.load_cert_chain(server_cert)
+    client_context.load_verify_locations(SIGNING_CA)
 
     return client_context, server_context, hostname
 
@@ -1016,7 +1020,8 @@ class ContextTests(unittest.TestCase):
         default = (ssl.OP_ALL | ssl.OP_NO_SSLv2 | ssl.OP_NO_SSLv3)
         # SSLContext also enables these by default
         default |= (OP_NO_COMPRESSION | OP_CIPHER_SERVER_PREFERENCE |
-                    OP_SINGLE_DH_USE | OP_SINGLE_ECDH_USE)
+                    OP_SINGLE_DH_USE | OP_SINGLE_ECDH_USE |
+                    OP_ENABLE_MIDDLEBOX_COMPAT)
         self.assertEqual(default, ctx.options)
         ctx.options |= ssl.OP_NO_TLSv1
         self.assertEqual(default | ssl.OP_NO_TLSv1, ctx.options)
@@ -1778,6 +1783,8 @@ class SimpleBackgroundTests(unittest.TestCase):
         der = ssl.PEM_cert_to_DER_cert(pem)
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS)
         ctx.verify_mode = ssl.CERT_REQUIRED
+        # TODO: fix TLSv1.3 support
+        ctx.options |= ssl.OP_NO_TLSv1_3
         ctx.load_verify_locations(cadata=pem)
         with ctx.wrap_socket(socket.socket(socket.AF_INET)) as s:
             s.connect(self.server_addr)
@@ -1787,6 +1794,8 @@ class SimpleBackgroundTests(unittest.TestCase):
         # same with DER
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS)
         ctx.verify_mode = ssl.CERT_REQUIRED
+        # TODO: fix TLSv1.3 support
+        ctx.options |= ssl.OP_NO_TLSv1_3
         ctx.load_verify_locations(cadata=der)
         with ctx.wrap_socket(socket.socket(socket.AF_INET)) as s:
             s.connect(self.server_addr)
@@ -2629,7 +2638,10 @@ class ThreadedTests(unittest.TestCase):
     def test_ecc_cert(self):
         client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
         client_context.load_verify_locations(SIGNING_CA)
-        client_context.set_ciphers('ECDHE:ECDSA:!NULL:!aRSA')
+        client_context.set_ciphers(
+            'TLS13-AES-128-GCM-SHA256:TLS13-CHACHA20-POLY1305-SHA256:'
+            'ECDHE:ECDSA:!NULL:!aRSA'
+        )
         hostname = SIGNED_CERTFILE_ECC_HOSTNAME
 
         server_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
@@ -2650,6 +2662,9 @@ class ThreadedTests(unittest.TestCase):
     def test_dual_rsa_ecc(self):
         client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
         client_context.load_verify_locations(SIGNING_CA)
+        # TODO: fix TLSv1.3 once SSLContext can restrict signature
+        #       algorithms.
+        client_context.options |= ssl.OP_NO_TLSv1_3
         # only ECDSA certs
         client_context.set_ciphers('ECDHE:ECDSA:!NULL:!aRSA')
         hostname = SIGNED_CERTFILE_ECC_HOSTNAME
@@ -2676,6 +2691,8 @@ class ThreadedTests(unittest.TestCase):
 
         server_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
         server_context.load_cert_chain(IDNSANSFILE)
+        # TODO: fix TLSv1.3 support
+        server_context.options |= ssl.OP_NO_TLSv1_3
 
         context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
         context.verify_mode = ssl.CERT_REQUIRED
@@ -2738,15 +2755,22 @@ class ThreadedTests(unittest.TestCase):
         Launch a server with CERT_REQUIRED, and check that trying to
         connect to it with a wrong client certificate fails.
         """
-        certfile = os.path.join(os.path.dirname(__file__) or os.curdir,
-                                   "wrongcert.pem")
-        server = ThreadedEchoServer(CERTFILE,
-                                    certreqs=ssl.CERT_REQUIRED,
-                                    cacerts=CERTFILE, chatty=False,
-                                    connectionchatty=False)
+        client_context, server_context, hostname = testing_context()
+        # load client cert
+        client_context.load_cert_chain(WRONG_CERT)
+        # require TLS client authentication
+        server_context.verify_mode = ssl.CERT_REQUIRED
+        # TODO: fix TLSv1.3 support
+        # With TLS 1.3, test fails with exception in server thread
+        server_context.options |= ssl.OP_NO_TLSv1_3
+
+        server = ThreadedEchoServer(
+            context=server_context, chatty=True, connectionchatty=True,
+        )
+
         with server, \
-                socket.socket() as sock, \
-                test_wrap_socket(sock, certfile=certfile) as s:
+                client_context.wrap_socket(socket.socket(),
+                                           server_hostname=hostname) as s:
             try:
                 # Expect either an SSL error about the server rejecting
                 # the connection, or a low-level connection reset (which
@@ -3400,7 +3424,9 @@ class ThreadedTests(unittest.TestCase):
                 self.assertIs(s.version(), None)
                 self.assertIs(s._sslobj, None)
                 s.connect((HOST, server.port))
-                if ssl.OPENSSL_VERSION_INFO >= (1, 0, 2):
+                if ssl.OPENSSL_VERSION_INFO >= (1, 1, 1):
+                    self.assertEqual(s.version(), 'TLSv1.3')
+                elif ssl.OPENSSL_VERSION_INFO >= (1, 0, 2):
                     self.assertEqual(s.version(), 'TLSv1.2')
                 else:  # 0.9.8 to 1.0.1
                     self.assertIn(s.version(), ('TLSv1', 'TLSv1.2'))
@@ -3412,18 +3438,18 @@ class ThreadedTests(unittest.TestCase):
     def test_tls1_3(self):
         context = ssl.SSLContext(ssl.PROTOCOL_TLS)
         context.load_cert_chain(CERTFILE)
-        # disable all but TLS 1.3
         context.options |= (
             ssl.OP_NO_TLSv1 | ssl.OP_NO_TLSv1_1 | ssl.OP_NO_TLSv1_2
         )
         with ThreadedEchoServer(context=context) as server:
             with context.wrap_socket(socket.socket()) as s:
                 s.connect((HOST, server.port))
-                self.assertIn(s.cipher()[0], [
+                self.assertIn(s.cipher()[0], {
                     'TLS13-AES-256-GCM-SHA384',
                     'TLS13-CHACHA20-POLY1305-SHA256',
                     'TLS13-AES-128-GCM-SHA256',
-                ])
+                })
+                self.assertEqual(s.version(), 'TLSv1.3')
 
     @unittest.skipUnless(ssl.HAS_ECDH, "test requires ECDH-enabled OpenSSL")
     def test_default_ecdh_curve(self):
@@ -3452,58 +3478,54 @@ class ThreadedTests(unittest.TestCase):
         if support.verbose:
             sys.stdout.write("\n")
 
-        server = ThreadedEchoServer(CERTFILE,
-                                    certreqs=ssl.CERT_NONE,
-                                    ssl_version=ssl.PROTOCOL_TLS_SERVER,
-                                    cacerts=CERTFILE,
+        client_context, server_context, hostname = testing_context()
+        # TODO: fix TLSv1.3 support
+        client_context.options |= ssl.OP_NO_TLSv1_3
+
+        server = ThreadedEchoServer(context=server_context,
                                     chatty=True,
                                     connectionchatty=False)
+
         with server:
-            s = test_wrap_socket(socket.socket(),
-                                server_side=False,
-                                certfile=CERTFILE,
-                                ca_certs=CERTFILE,
-                                cert_reqs=ssl.CERT_NONE,
-                                ssl_version=ssl.PROTOCOL_TLS_CLIENT)
-            s.connect((HOST, server.port))
-            # get the data
-            cb_data = s.get_channel_binding("tls-unique")
-            if support.verbose:
-                sys.stdout.write(" got channel binding data: {0!r}\n"
-                                 .format(cb_data))
-
-            # check if it is sane
-            self.assertIsNotNone(cb_data)
-            self.assertEqual(len(cb_data), 12) # True for TLSv1
-
-            # and compare with the peers version
-            s.write(b"CB tls-unique\n")
-            peer_data_repr = s.read().strip()
-            self.assertEqual(peer_data_repr,
-                             repr(cb_data).encode("us-ascii"))
-            s.close()
+            with client_context.wrap_socket(
+                    socket.socket(),
+                    server_hostname=hostname) as s:
+                s.connect((HOST, server.port))
+                # get the data
+                cb_data = s.get_channel_binding("tls-unique")
+                if support.verbose:
+                    sys.stdout.write(
+                        " got channel binding data: {0!r}\n".format(cb_data))
+
+                # check if it is sane
+                self.assertIsNotNone(cb_data)
+                self.assertEqual(len(cb_data), 12) # True for TLSv1
+
+                # and compare with the peers version
+                s.write(b"CB tls-unique\n")
+                peer_data_repr = s.read().strip()
+                self.assertEqual(peer_data_repr,
+                                 repr(cb_data).encode("us-ascii"))
 
             # now, again
-            s = test_wrap_socket(socket.socket(),
-                                server_side=False,
-                                certfile=CERTFILE,
-                                ca_certs=CERTFILE,
-                                cert_reqs=ssl.CERT_NONE,
-                                ssl_version=ssl.PROTOCOL_TLS_CLIENT)
-            s.connect((HOST, server.port))
-            new_cb_data = s.get_channel_binding("tls-unique")
-            if support.verbose:
-                sys.stdout.write(" got another channel binding data: {0!r}\n"
-                                 .format(new_cb_data))
-            # is it really unique
-            self.assertNotEqual(cb_data, new_cb_data)
-            self.assertIsNotNone(cb_data)
-            self.assertEqual(len(cb_data), 12) # True for TLSv1
-            s.write(b"CB tls-unique\n")
-            peer_data_repr = s.read().strip()
-            self.assertEqual(peer_data_repr,
-                             repr(new_cb_data).encode("us-ascii"))
-            s.close()
+            with client_context.wrap_socket(
+                    socket.socket(),
+                    server_hostname=hostname) as s:
+                s.connect((HOST, server.port))
+                new_cb_data = s.get_channel_binding("tls-unique")
+                if support.verbose:
+                    sys.stdout.write(
+                        "got another channel binding data: {0!r}\n".format(
+                            new_cb_data)
+                    )
+                # is it really unique
+                self.assertNotEqual(cb_data, new_cb_data)
+                self.assertIsNotNone(cb_data)
+                self.assertEqual(len(cb_data), 12) # True for TLSv1
+                s.write(b"CB tls-unique\n")
+                peer_data_repr = s.read().strip()
+                self.assertEqual(peer_data_repr,
+                                 repr(new_cb_data).encode("us-ascii"))
 
     def test_compression(self):
         client_context, server_context, hostname = testing_context()
@@ -3528,8 +3550,11 @@ class ThreadedTests(unittest.TestCase):
     def test_dh_params(self):
         # Check we can get a connection with ephemeral Diffie-Hellman
         client_context, server_context, hostname = testing_context()
+        # test scenario needs TLS <= 1.2
+        client_context.options |= ssl.OP_NO_TLSv1_3
         server_context.load_dh_params(DHFILE)
         server_context.set_ciphers("kEDH")
+        server_context.options |= ssl.OP_NO_TLSv1_3
         stats = server_params_test(client_context, server_context,
                                    chatty=True, connectionchatty=True,
                                    sni_name=hostname)
@@ -3539,9 +3564,11 @@ class ThreadedTests(unittest.TestCase):
             self.fail("Non-DH cipher: " + cipher[0])
 
     @unittest.skipUnless(HAVE_SECP_CURVES, "needs secp384r1 curve support")
+    @unittest.skipIf(IS_OPENSSL_1_1_1, "TODO: Test doesn't work on 1.1.1")
     def test_ecdh_curve(self):
         # server secp384r1, client auto
         client_context, server_context, hostname = testing_context()
+
         server_context.set_ecdh_curve("secp384r1")
         server_context.set_ciphers("ECDHE:!eNULL:!aNULL")
         server_context.options |= ssl.OP_NO_TLSv1 | ssl.OP_NO_TLSv1_1
@@ -3572,7 +3599,7 @@ class ThreadedTests(unittest.TestCase):
             pass
         else:
             # OpenSSL 1.0.2 does not fail although it should.
-            if IS_OPENSSL_1_1:
+            if IS_OPENSSL_1_1_0:
                 self.fail("mismatch curve did not fail")
 
     def test_selected_alpn_protocol(self):
@@ -3616,7 +3643,7 @@ class ThreadedTests(unittest.TestCase):
             except ssl.SSLError as e:
                 stats = e
 
-            if (expected is None and IS_OPENSSL_1_1
+            if (expected is None and IS_OPENSSL_1_1_0
                     and ssl.OPENSSL_VERSION_INFO < (1, 1, 0, 6)):
                 # OpenSSL 1.1.0 to 1.1.0e raises handshake error
                 self.assertIsInstance(stats, ssl.SSLError)
@@ -3823,6 +3850,8 @@ class ThreadedTests(unittest.TestCase):
 
     def test_session(self):
         client_context, server_context, hostname = testing_context()
+        # TODO: sessions aren't compatible with TLSv1.3 yet
+        client_context.options |= ssl.OP_NO_TLSv1_3
 
         # first connection without session
         stats = server_params_test(client_context, server_context,
@@ -3881,7 +3910,7 @@ class ThreadedTests(unittest.TestCase):
         client_context, server_context, hostname = testing_context()
         client_context2, _, _ = testing_context()
 
-        # TODO: session reuse does not work with TLS 1.3
+        # TODO: session reuse does not work with TLSv1.3
         client_context.options |= ssl.OP_NO_TLSv1_3
         client_context2.options |= ssl.OP_NO_TLSv1_3
 

Misc/NEWS.d/next/Library/2018-02-25-13-06-21.bpo-32947.mqStVW.rst

+Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future
+compatibility with OpenSSL 1.1.1.

Modules/_ssl.c

@@ -5681,6 +5681,10 @@ PyInit__ssl(void)
     PyModule_AddIntConstant(m, "OP_NO_COMPRESSION",
                             SSL_OP_NO_COMPRESSION);
 #endif
+#ifdef SSL_OP_ENABLE_MIDDLEBOX_COMPAT
+    PyModule_AddIntConstant(m, "OP_ENABLE_MIDDLEBOX_COMPAT",
+                            SSL_OP_ENABLE_MIDDLEBOX_COMPAT);
+#endif
 
 #ifdef X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT
     PyModule_AddIntConstant(m, "HOSTFLAG_ALWAYS_CHECK_SUBJECT",

Tools/ssl/multissltests.py

@@ -41,24 +41,20 @@ import tarfile
 log = logging.getLogger("multissl")
 
 OPENSSL_OLD_VERSIONS = [
-     # "0.9.8zh",
-     # "1.0.1u",
+    "1.0.2",
 ]
 
 OPENSSL_RECENT_VERSIONS = [
-     "1.0.2",
-     "1.0.2m",
-     "1.1.0g",
+    "1.0.2n",
+    "1.1.0g",
+    "1.1.1-pre1",
 ]
 
 LIBRESSL_OLD_VERSIONS = [
-    # "2.3.10",
-    # "2.4.5",
 ]
 
 LIBRESSL_RECENT_VERSIONS = [
-    "2.5.3",
-    "2.5.5",
+    # "2.6.5",
 ]
 
 # store files in ../multissl