[Python-checkins] bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3 (#1363)

Thu Sep 7 21:07:02 EDT 2017

https://github.com/python/cpython/commit/cb5b68abdeb1b1d56c581d5b4d647018703d61e3
commit: cb5b68abdeb1b1d56c581d5b4d647018703d61e3
branch: master
author: Christian Heimes <christian at python.org>
committer: GitHub <noreply at github.com>
date: 2017年09月07日T18:07:00-07:00
summary:
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 <christian at python.org>
files:
A Misc/NEWS.d/next/Library/2017-09-04-16-39-49.bpo-29136.vSn1oR.rst
M Doc/library/ssl.rst
M Lib/ssl.py
M Lib/test/test_ssl.py
M Modules/_ssl.c

diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
index 69bea1ed4a0..031c3618bef 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 7a574dcb2b1..1f3a31a9b79 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -115,7 +115,7 @@
 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 @@
 # (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 @@
 # * 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 @@
 
 # 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 @@
 # * 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 747661bc6d0..fe9f6939d33 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -170,6 +170,13 @@ def test_constants(self):
 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 @@ def test_version_basic(self):
 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 @@ def test_session_handling(self):
 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 00000000000..e76997ef836
--- /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 5ea354a60aa..f7379257956 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();
