Added support for SNI (#755)

feat(core): add support for SNI

Provide in `check_hostname` in the client too.

---------

Co-authored-by: Jeff Widman <jeff@jeffwidman.com>

kazoo/client.py

@@ -120,6 +120,7 @@ def __init__(
         ca=None,
         use_ssl=False,
         verify_certs=True,
+        check_hostname=False,
         **kwargs,
     ):
         """Create a :class:`KazooClient` instance. All time arguments
@@ -182,6 +183,8 @@ def __init__(
         :param use_ssl: argument to control whether SSL is used or not
         :param verify_certs: when using SSL, argument to bypass
             certs verification
+        :param check_hostname: when using SSL, check the hostname
+            against the hostname in the cert
 
         Basic Example:
 
@@ -237,6 +240,7 @@ def __init__(
 
         self.use_ssl = use_ssl
         self.verify_certs = verify_certs
+        self.check_hostname = check_hostname
         self.certfile = certfile
         self.keyfile = keyfile
         self.keyfile_password = keyfile_password
@@ -758,15 +762,18 @@ def command(self, cmd=b"ruok"):
             raise ConnectionLoss("No connection to server")
 
         peer = self._connection._socket.getpeername()[:2]
+        peer_host = self._connection._socket.getpeername()[1]
         sock = self.handler.create_connection(
             peer,
+            hostname=peer_host,
             timeout=self._session_timeout / 1000.0,
             use_ssl=self.use_ssl,
             ca=self.ca,
             certfile=self.certfile,
             keyfile=self.keyfile,
             keyfile_password=self.keyfile_password,
             verify_certs=self.verify_certs,
+            check_hostname=self.check_hostname,
         )
         sock.sendall(cmd)
         result = sock.recv(8192)

kazoo/handlers/utils.py

@@ -196,13 +196,15 @@ def create_tcp_socket(module):
 def create_tcp_connection(
     module,
     address,
+    hostname=None,
     timeout=None,
     use_ssl=False,
     ca=None,
     certfile=None,
     keyfile=None,
     keyfile_password=None,
     verify_certs=True,
+    check_hostname=False,
     options=None,
     ciphers=None,
 ):
@@ -237,11 +239,14 @@ def create_tcp_connection(
 
             # Load default CA certs
             context.load_default_certs(ssl.Purpose.SERVER_AUTH)
+            if check_hostname and not verify_certs:
+                raise ValueError(
+                    "verify_certs must be True when"
+                    + " check_hostname is True"
+                )
             # We must set check_hostname to False prior to setting
             # verify_mode to CERT_NONE.
-            # TODO: Make hostname verification configurable as some users may
-            # elect to use it.
-            context.check_hostname = False
+            context.check_hostname = check_hostname
             context.verify_mode = (
                 ssl.CERT_REQUIRED if verify_certs else ssl.CERT_NONE
             )
@@ -258,7 +263,9 @@ def create_tcp_connection(
                 addrs = socket.getaddrinfo(
                     address[0], address[1], 0, socket.SOCK_STREAM
                 )
-                conn = context.wrap_socket(module.socket(addrs[0][0]))
+                conn = context.wrap_socket(
+                    module.socket(addrs[0][0]), server_hostname=hostname
+                )
                 conn.settimeout(timeout_at)
                 conn.connect(address)
                 sock = conn

kazoo/protocol/connection.py

@@ -703,13 +703,15 @@ def _connect(self, host, hostip, port):
         with self._socket_error_handling():
             self._socket = self.handler.create_connection(
                 address=(hostip, port),
+                hostname=host,
                 timeout=client._session_timeout / 1000.0,
                 use_ssl=self.client.use_ssl,
                 keyfile=self.client.keyfile,
                 certfile=self.client.certfile,
                 ca=self.client.ca,
                 keyfile_password=self.client.keyfile_password,
                 verify_certs=self.client.verify_certs,
+                check_hostname=self.client.check_hostname,
             )
 
         self._socket.setblocking(0)

kazoo/tests/test_utils.py

@@ -30,6 +30,59 @@ def test_timeout_arg(self):
                     timeout = call_args[0][1]
                     assert timeout >= 0, "socket timeout must be nonnegative"
 
+    def test_ssl_server_hostname(self):
+        from kazoo.handlers import utils
+        from kazoo.handlers.utils import create_tcp_connection, socket, ssl
+
+        with patch.object(utils, "_set_default_tcpsock_options"):
+            with patch.object(ssl.SSLContext, "wrap_socket") as wrap_socket:
+                create_tcp_connection(
+                    socket,
+                    ("127.0.0.1", 2181),
+                    timeout=1.5,
+                    hostname="fakehostname",
+                    use_ssl=True,
+                )
+
+                for call_args in wrap_socket.call_args_list:
+                    server_hostname = call_args[1]["server_hostname"]
+                    assert server_hostname == "fakehostname"
+
+    def test_ssl_server_check_hostname(self):
+        from kazoo.handlers import utils
+        from kazoo.handlers.utils import create_tcp_connection, socket, ssl
+
+        with patch.object(utils, "_set_default_tcpsock_options"):
+            with patch.object(
+                ssl.SSLContext, "wrap_socket", autospec=True
+            ) as wrap_socket:
+                create_tcp_connection(
+                    socket,
+                    ("127.0.0.1", 2181),
+                    timeout=1.5,
+                    hostname="fakehostname",
+                    use_ssl=True,
+                    check_hostname=True,
+                )
+
+                for call_args in wrap_socket.call_args_list:
+                    ssl_context = call_args[0][0]
+                    assert ssl_context.check_hostname
+
+    def test_ssl_server_check_hostname_config_validation(self):
+        from kazoo.handlers.utils import create_tcp_connection, socket
+
+        with pytest.raises(ValueError):
+            create_tcp_connection(
+                socket,
+                ("127.0.0.1", 2181),
+                timeout=1.5,
+                hostname="fakehostname",
+                use_ssl=True,
+                verify_certs=False,
+                check_hostname=True,
+            )
+
     def test_timeout_arg_eventlet(self):
         if not EVENTLET_HANDLER_AVAILABLE:
             pytest.skip("eventlet handler not available.")