Adding custom TLS cipher suite config option

This change adds a server configuration option, tls_cipher_suites,
allowing the server admin to specify a list of cipher suites to be
used when establishing TLS connections with clients. The custom
list supports both cipher suite specification and OpenSSL suite
naming conventions. The list is filtered through a KMIP-approved
set of cipher suites, and then through a set of cipher suites
suitable for the configured authentication suite. Additional debug
logging has been added to the server to provide transparency on
this process.

kmip/services/server/session.py

@@ -158,6 +158,17 @@ class KmipSession(threading.Thread):
         max_size = self._max_response_size
 
         try:
+            shared_ciphers = self._connection.shared_ciphers()
+            self._logger.debug(
+                "Possible session ciphers: {0}".format(len(shared_ciphers))
+            )
+            for cipher in shared_ciphers:
+                self._logger.debug(cipher)
+            self._logger.debug(
+                "Session cipher selected: {0}".format(
+                    self._connection.cipher()
+                )
+            )
             client_identity = self._get_client_identity()
             request.read(request_data)
         except Exception as e: