[2.7] bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3 (GH-1363) (#3446)

* 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@python.org>.
(cherry picked from commit cb5b68abdeb1b1d56c581d5b4d647018703d61e3)

diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
index 36beb1777cf036ac029ce97b6148ff61142cbc35..288b2914a25c1fd4e86a45b5d75c52673454c72a 100644 (file)
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -192,12 +192,17 @@ instead.
        ------------------------  ---------  ---------  ----------  ---------  -----------  -----------
         *SSLv2*                    yes        no         yes         no         no         no
         *SSLv3*                    no         yes        yes         no         no         no
-        *SSLv23*                   no         yes        yes         yes        yes        yes
+        *SSLv23* [1]_              no         yes        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
        ========================  =========  =========  ==========  =========  ===========  ===========
 
+   .. rubric:: Footnotes
+   .. [1] TLS 1.3 protocol will be available with :data:`PROTOCOL_SSLv23` in
+      OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just
+      TLS 1.3.
+
    .. note::
 
       Which connections succeed will vary depending on the version of
@@ -286,6 +291,11 @@ 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
@@ -701,6 +711,16 @@ Constants
 
    .. versionadded:: 2.7.9
 
+.. 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:: 2.7.15
+
 .. data:: OP_CIPHER_SERVER_PREFERENCE
 
    Use the server's cipher ordering preference, rather than the client's.
@@ -765,6 +785,12 @@ Constants
 
    .. versionadded:: 2.7.9
 
+.. data:: HAS_TLSv1_3
+
+   Whether the OpenSSL library has built-in support for the TLS 1.3 protocol.
+
+   .. versionadded:: 2.7.15
+
 .. 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 f28c863811fd9810988d107a9f24a3c8678aa284..22d478b56871b48fd5fdd17136bfb1faec1ebdec 100644 (file)
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -123,7 +123,7 @@ _import_symbols('SSL_ERROR_')
 _import_symbols('PROTOCOL_')
 _import_symbols('VERIFY_')
 
-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
 
@@ -157,6 +157,7 @@ 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
@@ -168,6 +169,8 @@ 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'
@@ -175,6 +178,7 @@ _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
@@ -185,6 +189,8 @@ _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 d9ef232580c1236ab4fb6a415719c780cf3e3d1b..cfc03e343c7d6b6d082f1708373a00afcfab440f 100644 (file)
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -168,6 +168,13 @@ 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_random(self):
         v = ssl.RAND_status()
@@ -2784,6 +2791,24 @@ else:
                     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

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 (file)
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 5b4cec203addf68df154c439376f7c06a7da23e9..f70af266731ad073ce534fe94a99071c15fc0a61 100644 (file)
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -4281,6 +4281,11 @@ init_ssl(void)
 #if HAVE_TLSv1_2
     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);
@@ -4333,6 +4338,14 @@ init_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();