From cb5b68abdeb1b1d56c581d5b4d647018703d61e3 Mon Sep 17 00:00:00 2001 From: Christian Heimes Date: Thu, 7 Sep 2017 18:07:00 -0700 Subject: bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3 (#1363) * bpo-29136: Add TLS 1.3 support TLS 1.3 introduces a new, distinct set of cipher suites. The TLS 1.3 cipher suites don't overlap with cipher suites from TLS 1.2 and earlier. Since Python sets its own set of permitted ciphers, TLS 1.3 handshake will fail as soon as OpenSSL 1.1.1 is released. Let's enable the common AES-GCM and ChaCha20 suites. Additionally the flag OP_NO_TLSv1_3 is added. It defaults to 0 (no op) with OpenSSL prior to 1.1.1. This allows applications to opt-out from TLS 1.3 now. Signed-off-by: Christian Heimes --- Doc/library/ssl.rst | 28 +++++++++++++++++-- Lib/ssl.py | 8 +++++- Lib/test/test_ssl.py | 32 ++++++++++++++++++++++ .../2017-09-04-16-39-49.bpo-29136.vSn1oR.rst | 1 + Modules/_ssl.c | 13 +++++++++ 5 files changed, 79 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2017-09-04-16-39-49.bpo-29136.vSn1oR.rst diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst index 69bea1e..031c361 100644 --- a/Doc/library/ssl.rst +++ b/Doc/library/ssl.rst @@ -193,11 +193,11 @@ instead. .. table:: ======================== ============ ============ ============= ========= =========== =========== - *client* / **server** **SSLv2** **SSLv3** **TLS** **TLSv1** **TLSv1.1** **TLSv1.2** + *client* / **server** **SSLv2** **SSLv3** **TLS** [3]_ **TLSv1** **TLSv1.1** **TLSv1.2** ------------------------ ------------ ------------ ------------- --------- ----------- ----------- *SSLv2* yes no no [1]_ no no no *SSLv3* no yes no [2]_ no no no - *TLS* (*SSLv23*) no [1]_ no [2]_ yes yes yes yes + *TLS* (*SSLv23*) [3]_ no [1]_ no [2]_ yes yes yes yes *TLSv1* no no yes yes no no *TLSv1.1* no no yes no yes no *TLSv1.2* no no yes no no yes @@ -206,6 +206,9 @@ instead. .. rubric:: Footnotes .. [1] :class:`SSLContext` disables SSLv2 with :data:`OP_NO_SSLv2` by default. .. [2] :class:`SSLContext` disables SSLv3 with :data:`OP_NO_SSLv3` by default. + .. [3] TLS 1.3 protocol will be available with :data:`PROTOCOL_TLS` in + OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just + TLS 1.3. .. note:: @@ -294,6 +297,11 @@ purposes. 3DES was dropped from the default cipher string. + .. versionchanged:: 3.7 + + 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. + Random generation ^^^^^^^^^^^^^^^^^ @@ -764,6 +772,16 @@ Constants .. versionadded:: 3.4 +.. data:: OP_NO_TLSv1_3 + + Prevents a TLSv1.3 connection. This option is only applicable in conjunction + with :const:`PROTOCOL_TLS`. It prevents the peers from choosing TLSv1.3 as + the protocol version. TLS 1.3 is available with OpenSSL 1.1.1 or later. + When Python has been compiled against an older version of OpenSSL, the + flag defaults to *0*. + + .. versionadded:: 3.7 + .. data:: OP_CIPHER_SERVER_PREFERENCE Use the server's cipher ordering preference, rather than the client's. @@ -838,6 +856,12 @@ Constants .. versionadded:: 3.3 +.. data:: HAS_TLSv1_3 + + Whether the OpenSSL library has built-in support for the TLS 1.3 protocol. + + .. versionadded:: 3.7 + .. data:: CHANNEL_BINDING_TYPES List of supported TLS channel binding types. Strings in this list diff --git a/Lib/ssl.py b/Lib/ssl.py index 7a574dc..1f3a31a 100644 --- a/Lib/ssl.py +++ b/Lib/ssl.py @@ -115,7 +115,7 @@ except ImportError: pass -from _ssl import HAS_SNI, HAS_ECDH, HAS_NPN, HAS_ALPN +from _ssl import HAS_SNI, HAS_ECDH, HAS_NPN, HAS_ALPN, HAS_TLSv1_3 from _ssl import _OPENSSL_API_VERSION @@ -178,6 +178,7 @@ else: # (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL') # Enable a better set of ciphers by default # This list has been explicitly chosen to: +# * TLS 1.3 ChaCha20 and AES-GCM cipher suites # * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE) # * Prefer ECDHE over DHE for better performance # * Prefer AEAD over CBC for better performance and security @@ -189,6 +190,8 @@ else: # * Disable NULL authentication, NULL encryption, 3DES and MD5 MACs # for security reasons _DEFAULT_CIPHERS = ( + 'TLS13-AES-256-GCM-SHA384:TLS13-CHACHA20-POLY1305-SHA256:' + 'TLS13-AES-128-GCM-SHA256:' 'ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:' 'ECDH+AES128:DH+AES:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:' '!aNULL:!eNULL:!MD5:!3DES' @@ -196,6 +199,7 @@ _DEFAULT_CIPHERS = ( # Restricted and more secure ciphers for the server side # This list has been explicitly chosen to: +# * TLS 1.3 ChaCha20 and AES-GCM cipher suites # * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE) # * Prefer ECDHE over DHE for better performance # * Prefer AEAD over CBC for better performance and security @@ -206,6 +210,8 @@ _DEFAULT_CIPHERS = ( # * Disable NULL authentication, NULL encryption, MD5 MACs, DSS, RC4, and # 3DES for security reasons _RESTRICTED_SERVER_CIPHERS = ( + 'TLS13-AES-256-GCM-SHA384:TLS13-CHACHA20-POLY1305-SHA256:' + 'TLS13-AES-128-GCM-SHA256:' 'ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:' 'ECDH+AES128:DH+AES:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:' '!aNULL:!eNULL:!MD5:!DSS:!RC4:!3DES' diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py index 747661b..fe9f693 100644 --- a/Lib/test/test_ssl.py +++ b/Lib/test/test_ssl.py @@ -170,6 +170,13 @@ class BasicSocketTests(unittest.TestCase): ssl.OP_NO_COMPRESSION self.assertIn(ssl.HAS_SNI, {True, False}) self.assertIn(ssl.HAS_ECDH, {True, False}) + ssl.OP_NO_SSLv2 + ssl.OP_NO_SSLv3 + ssl.OP_NO_TLSv1 + ssl.OP_NO_TLSv1_3 + if ssl.OPENSSL_VERSION_INFO >= (1, 0, 1): + ssl.OP_NO_TLSv1_1 + ssl.OP_NO_TLSv1_2 def test_str_for_enums(self): # Make sure that the PROTOCOL_* constants have enum-like string @@ -3098,12 +3105,33 @@ class ThreadedTests(unittest.TestCase): self.assertEqual(s.version(), 'TLSv1') self.assertIs(s.version(), None) + @unittest.skipUnless(ssl.HAS_TLSv1_3, + "test requires TLSv1.3 enabled OpenSSL") + 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], [ + 'TLS13-AES-256-GCM-SHA384', + 'TLS13-CHACHA20-POLY1305-SHA256', + 'TLS13-AES-128-GCM-SHA256', + ]) + @unittest.skipUnless(ssl.HAS_ECDH, "test requires ECDH-enabled OpenSSL") def test_default_ecdh_curve(self): # Issue #21015: elliptic curve-based Diffie Hellman key exchange # should be enabled by default on SSL contexts. context = ssl.SSLContext(ssl.PROTOCOL_SSLv23) context.load_cert_chain(CERTFILE) + # TLSv1.3 defaults to PFS key agreement and no longer has KEA in + # cipher name. + context.options |= ssl.OP_NO_TLSv1_3 # Prior to OpenSSL 1.0.0, ECDH ciphers have to be enabled # explicitly using the 'ECCdraft' cipher alias. Otherwise, # our default cipher list should prefer ECDH-based ciphers @@ -3532,6 +3560,10 @@ class ThreadedTests(unittest.TestCase): context2.load_verify_locations(CERTFILE) context2.load_cert_chain(CERTFILE) + # TODO: session reuse does not work with TLS 1.3 + context.options |= ssl.OP_NO_TLSv1_3 + context2.options |= ssl.OP_NO_TLSv1_3 + server = ThreadedEchoServer(context=context, chatty=False) with server: with context.wrap_socket(socket.socket()) as s: diff --git a/Misc/NEWS.d/next/Library/2017-09-04-16-39-49.bpo-29136.vSn1oR.rst b/Misc/NEWS.d/next/Library/2017-09-04-16-39-49.bpo-29136.vSn1oR.rst new file mode 100644 index 0000000..e76997e --- /dev/null +++ b/Misc/NEWS.d/next/Library/2017-09-04-16-39-49.bpo-29136.vSn1oR.rst @@ -0,0 +1 @@ +Add TLS 1.3 cipher suites and OP_NO_TLSv1_3. diff --git a/Modules/_ssl.c b/Modules/_ssl.c index 5ea354a..f737925 100644 --- a/Modules/_ssl.c +++ b/Modules/_ssl.c @@ -5350,6 +5350,11 @@ PyInit__ssl(void) PyModule_AddIntConstant(m, "OP_NO_TLSv1_1", SSL_OP_NO_TLSv1_1); PyModule_AddIntConstant(m, "OP_NO_TLSv1_2", SSL_OP_NO_TLSv1_2); #endif +#ifdef SSL_OP_NO_TLSv1_3 + PyModule_AddIntConstant(m, "OP_NO_TLSv1_3", SSL_OP_NO_TLSv1_3); +#else + PyModule_AddIntConstant(m, "OP_NO_TLSv1_3", 0); +#endif PyModule_AddIntConstant(m, "OP_CIPHER_SERVER_PREFERENCE", SSL_OP_CIPHER_SERVER_PREFERENCE); PyModule_AddIntConstant(m, "OP_SINGLE_DH_USE", SSL_OP_SINGLE_DH_USE); @@ -5398,6 +5403,14 @@ PyInit__ssl(void) Py_INCREF(r); PyModule_AddObject(m, "HAS_ALPN", r); +#if defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3) + r = Py_True; +#else + r = Py_False; +#endif + Py_INCREF(r); + PyModule_AddObject(m, "HAS_TLSv1_3", r); + /* Mappings for error codes */ err_codes_to_names = PyDict_New(); err_names_to_codes = PyDict_New(); -- cgit v0.12