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[2.7] bpo-33570: TLS 1.3 ciphers for OpenSSL 1.1.1 (GH-6976) (GH-8760) #8771

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[2.7] bpo-33570: TLS 1.3 ciphers for OpenSSL 1.1.1 (GH-6976) (GH-8760) #8771

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8 changes: 3 additions & 5 deletions Doc/library/ssl.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -294,11 +294,6 @@ purposes.

3DES was dropped from the default cipher string.

.. versionchanged:: 2.7.15

TLS 1.3 cipher suites TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384,
and TLS_CHACHA20_POLY1305_SHA256 were added to the default cipher string.

.. function:: _https_verify_certificates(enable=True)

Specifies whether or not server certificates are verified when creating
Expand Down Expand Up @@ -1179,6 +1174,9 @@ to speed up repeated connections from the same clients.
when connected, the :meth:`SSLSocket.cipher` method of SSL sockets will
give the currently selected cipher.

OpenSSL 1.1.1 has TLS 1.3 cipher suites enabled by default. The suites
cannot be disabled with :meth:`~SSLContext.set_ciphers`.

.. method:: SSLContext.set_alpn_protocols(protocols)

Specify which protocols the socket should advertise during the SSL/TLS
Expand Down
37 changes: 21 additions & 16 deletions Lib/test/test_ssl.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2772,19 +2772,24 @@ def test_do_handshake_enotconn(self):
sock.do_handshake()
self.assertEqual(cm.exception.errno, errno.ENOTCONN)

def test_default_ciphers(self):
context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
try:
# Force a set of weak ciphers on our client context
context.set_ciphers("DES")
except ssl.SSLError:
self.skipTest("no DES cipher available")
with ThreadedEchoServer(CERTFILE,
ssl_version=ssl.PROTOCOL_SSLv23,
chatty=False) as server:
with closing(context.wrap_socket(socket.socket())) as s:
with self.assertRaises(ssl.SSLError):
s.connect((HOST, server.port))
def test_no_shared_ciphers(self):
server_context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
server_context.load_cert_chain(SIGNED_CERTFILE)
client_context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
client_context.verify_mode = ssl.CERT_REQUIRED
client_context.check_hostname = True

# OpenSSL enables all TLS 1.3 ciphers, enforce TLS 1.2 for test
client_context.options |= ssl.OP_NO_TLSv1_3
# Force different suites on client and master
client_context.set_ciphers("AES128")
server_context.set_ciphers("AES256")
with ThreadedEchoServer(context=server_context) as server:
s = client_context.wrap_socket(
socket.socket(),
server_hostname="localhost")
with self.assertRaises(ssl.SSLError):
s.connect((HOST, server.port))
self.assertIn("no shared cipher", str(server.conn_errors[0]))

def test_version_basic(self):
Expand Down Expand Up @@ -2815,9 +2820,9 @@ def test_tls1_3(self):
with context.wrap_socket(socket.socket()) as s:
s.connect((HOST, server.port))
self.assertIn(s.cipher()[0], [
'TLS13-AES-256-GCM-SHA384',
'TLS13-CHACHA20-POLY1305-SHA256',
'TLS13-AES-128-GCM-SHA256',
'TLS_AES_256_GCM_SHA384',
'TLS_CHACHA20_POLY1305_SHA256',
'TLS_AES_128_GCM_SHA256',
])

@unittest.skipUnless(ssl.HAS_ECDH, "test requires ECDH-enabled OpenSSL")
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2018-05-18-21-50-47.bpo-33570.7CZy4t.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Change TLS 1.3 cipher suite settings for compatibility with OpenSSL
1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 cipers enabled by
default.