CQL shell should prefer newer TLS version by default

patch by Kamlesh Ghoradkar; reviewed by Ekaterina Dimitrova, Adam Holmberg, David Capwell, Justin Chu and Brandon Williamms for CASSANDRA-16736

CHANGES.txt

@@ -1,4 +1,5 @@
 2.2.20
+ * CQL shell should prefer newer TLS version by default (CASSANDRA-16695)
  * Fix Debian init start/stop (CASSANDRA-15770)
  * Remove ant targets list-jvm-dtests and ant list-jvm-upgrade-dtests (CASSANDRA-16519)
  * Fix centos packaging for arm64, >=4.0 rpm's now require python3 (CASSANDRA-16477)

pylib/cqlshlib/sslhandling.py

@@ -47,6 +47,18 @@ def ssl_settings(host, config_file, env=os.environ):
         except ConfigParser.Error:
             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)
+        return None
+
     ssl_validate = env.get('SSL_VALIDATE')
     if ssl_validate is None:
         ssl_validate = get_option('ssl', 'validate')
@@ -55,13 +67,11 @@ def ssl_settings(host, config_file, env=os.environ):
     ssl_version_str = env.get('SSL_VERSION')
     if ssl_version_str is None:
         ssl_version_str = get_option('ssl', 'version')
-    if ssl_version_str is None:
-        ssl_version_str = "TLSv1"
 
-    ssl_version = getattr(ssl, "PROTOCOL_%s" % ssl_version_str, None)
+    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 SSLv23, "
-                 "TLSv1, TLSv1.1, or TLSv1.2" % (ssl_version_str,))
+        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

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

pylib/cqlshlib/test/config/sslhandling_invalid.config

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

pylib/cqlshlib/test/test_sslhandling.py

@@ -0,0 +1,75 @@
+#  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
+from nose.tools import assert_raises
+
+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 assert_raises(SystemExit) as error:
+            self._test_ssl_version_from_env('invalid_ssl')
+            assert msg == error.exception.message
+
+    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 assert_raises(SystemExit) as error:
+            ssl_settings(self.host, os.path.join('test', 'config', 'sslhandling_invalid.config'))
+            assert msg in error.exception.message
+