remove support for deprecated version specific TLS in Python 3.6

patch by Brad Schoening; reviewed by Stefan Miklosovic and Brandon Williams for CASSANDRA-17365

CHANGES.txt

@@ -1,4 +1,5 @@
 4.1
+ * remove support for deprecated version specific TLS in Python 3.6 (CASSANDRA-17365)
  * Add support for IF EXISTS and IF NOT EXISTS in ALTER statements (CASSANDRA-16916)
  * resolve several pylint issues in cqlsh.py and pylib (CASSANDRA-17480)
  * Streaming sessions longer than 3 minutes fail with timeout (CASSANDRA-17510)

conf/cqlshrc.sample

@@ -112,7 +112,9 @@ port = 9042
 ;; To be provided when require_client_auth=true
 ;usercert = ~/cert.pem
 
-
+; this is effectively ignored from 4.1 included as TLS protocol is auto-negotiated and will
+; be removed in the next major version of Cassandra, possible values were TLSv1, TLSv1_1 or TLSv1_2
+;version =
 
 ;; Optional section, overrides default certfile in [ssl] section, if present
 ; [certfiles]

pylib/cqlshlib/sslhandling.py

@@ -49,15 +49,8 @@ def ssl_settings(host, config_file, env=os.environ):
             return None
 
     def get_best_tls_protocol(ssl_ver_str):
-        # newer python versions suggest to use PROTOCOL_TLS to negotiate the highest TLS version.
-        # older protocol versions have been deprecated:
-        # https://docs.python.org/2/library/ssl.html#ssl.PROTOCOL_TLS
-        # https://docs.python.org/3/library/ssl.html#ssl.PROTOCOL_TLS
         if ssl_ver_str:
-            return getattr(ssl, "PROTOCOL_%s" % ssl_ver_str, None)
-        for protocol in ['PROTOCOL_TLS', 'PROTOCOL_TLSv1_2', 'PROTOCOL_TLSv1_1', 'PROTOCOL_TLSv1']:
-            if hasattr(ssl, protocol):
-                return getattr(ssl, protocol)
+            print("Warning: Explicit SSL and TLS versions in the cqlshrc file or in SSL_VERSION environment property are ignored as the protocol is auto-negotiated.\n")
         return ssl.PROTOCOL_TLS
 
     ssl_validate = env.get('SSL_VALIDATE')
@@ -70,9 +63,6 @@ def ssl_settings(host, config_file, env=os.environ):
         ssl_version_str = get_option('ssl', 'version')
 
     ssl_version = get_best_tls_protocol(ssl_version_str)
-    if ssl_version is None:
-        sys.exit("%s is not a valid SSL protocol, please use one of "
-                 "TLS, TLSv1_2, TLSv1_1, or TLSv1" % (ssl_version_str,))
 
     ssl_certfile = env.get('SSL_CERTFILE')
     if ssl_certfile is None:

pylib/cqlshlib/test/config/sslhandling.config

@@ -1,2 +0,0 @@
-[ssl]
-version = TLSv1

pylib/cqlshlib/test/config/sslhandling_invalid.config

@@ -1,2 +0,0 @@
-[ssl]
-version = invalid_ssl

pylib/cqlshlib/test/test_sslhandling.py

@@ -1,75 +0,0 @@
-#  Licensed to the Apache Software Foundation (ASF) under one
-#  or more contributor license agreements.  See the NOTICE file
-#  distributed with this work for additional information
-#  regarding copyright ownership.  The ASF licenses this file
-#  to you under the Apache License, Version 2.0 (the
-#  "License"); you may not use this file except in compliance
-#  with the License.  You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-#  Unless required by applicable law or agreed to in writing, software
-#  distributed under the License is distributed on an "AS IS" BASIS,
-#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-#  See the License for the specific language governing permissions and
-#  limitations under the License.
-
-from cassandra.policies import SimpleConvictionPolicy
-from cassandra.pool import Host
-from cqlshlib.sslhandling import ssl_settings
-import pytest
-
-import unittest
-import os
-import ssl
-
-
-class SslSettingsTest(unittest.TestCase):
-
-    def setUp(self):
-        os.environ['SSL_VALIDATE'] = 'False'
-        self.config_file = 'test_config'
-        self.host = Host('10.0.0.1', SimpleConvictionPolicy, 9000)
-
-    def tearDown(self):
-        del os.environ['SSL_VALIDATE']
-        try:
-            del os.environ['SSL_VERSION']
-        except KeyError:
-            pass
-
-    def _test_ssl_version_from_env(self, version):
-        """
-        Getting SSL version string from env variable SSL_VERSION.
-        """
-        os.environ['SSL_VERSION'] = version
-        ssl_ret_val = ssl_settings(self.host, self.config_file)
-        assert ssl_ret_val is not None
-        assert ssl_ret_val.get('ssl_version') == getattr(ssl, 'PROTOCOL_%s' % version)
-
-    def test_ssl_versions_from_env(self):
-        versions = ['TLS', 'TLSv1_1', 'TLSv1_2', 'TLSv1']
-        for version in versions:
-            self._test_ssl_version_from_env(version)
-
-    def test_invalid_ssl_versions_from_env(self):
-        msg = "invalid_ssl is not a valid SSL protocol, please use one of TLSv1, TLSv1_1, or TLSv1_2"
-        with pytest.raises(SystemExit) as error:
-            self._test_ssl_version_from_env('invalid_ssl')
-            assert msg == error.args[0]
-
-    def test_default_ssl_version(self):
-        ssl_ret_val = ssl_settings(self.host, self.config_file)
-        assert ssl_ret_val is not None
-        assert ssl_ret_val.get('ssl_version') == getattr(ssl, 'PROTOCOL_TLS')
-
-    def test_ssl_version_config(self):
-        ssl_ret_val = ssl_settings(self.host, os.path.join('test', 'config', 'sslhandling.config'))
-        assert ssl_ret_val is not None
-        assert ssl_ret_val.get('ssl_version') == getattr(ssl, 'PROTOCOL_TLSv1')
-
-    def test_invalid_ssl_version_config(self):
-        msg = "invalid_ssl is not a valid SSL protocol, please use one of TLSv1, TLSv1_1, or TLSv1_2"
-        with pytest.raises(SystemExit) as error:
-            ssl_settings(self.host, os.path.join('test', 'config', 'sslhandling_invalid.config'))
-            assert msg in error.exception.message