asyncio: Add server_hostname as create_connection() argument, with secure default.
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index 37d50aa..f18a556 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -275,8 +275,27 @@
@tasks.coroutine
def create_connection(self, protocol_factory, host=None, port=None, *,
ssl=None, family=0, proto=0, flags=0, sock=None,
- local_addr=None):
+ local_addr=None, server_hostname=None):
"""XXX"""
+ if server_hostname is not None and not ssl:
+ raise ValueError('server_hostname is only meaningful with ssl')
+
+ if server_hostname is None and ssl:
+ # Use host as default for server_hostname. It is an error
+ # if host is empty or not set, e.g. when an
+ # already-connected socket was passed or when only a port
+ # is given. To avoid this error, you can pass
+ # server_hostname='' -- this will bypass the hostname
+ # check. (This also means that if host is a numeric
+ # IP/IPv6 address, we will attempt to verify that exact
+ # address; this will probably fail, but it is possible to
+ # create a certificate for a specific IP address, so we
+ # don't judge it here.)
+ if not host:
+ raise ValueError('You must set server_hostname '
+ 'when using ssl without a host')
+ server_hostname = host
+
if host is not None or port is not None:
if sock is not None:
raise ValueError(
@@ -357,7 +376,7 @@
sslcontext = None if isinstance(ssl, bool) else ssl
transport = self._make_ssl_transport(
sock, protocol, sslcontext, waiter,
- server_side=False, server_hostname=host)
+ server_side=False, server_hostname=server_hostname)
else:
transport = self._make_socket_transport(sock, protocol, waiter)