[bpo-28414] Make all hostnames in SSL module IDN A-labels (GH-5128) (GH-5843)
Previously, the ssl module stored international domain names (IDNs)
as U-labels. This is problematic for a number of reasons -- for
example, it made it impossible for users to use a different version
of IDNA than the one built into Python.
After this change, we always convert to A-labels as soon as possible,
and use them for all internal processing. In particular, server_hostname
attribute is now an A-label, and on the server side there's a new
sni_callback that receives the SNI servername as an A-label rather than
a U-label.
(cherry picked from commit 11a1493bc4198f1def5e572049485779cf54dc57)
Co-authored-by: Christian Heimes <christian@python.org>
diff --git a/Lib/ssl.py b/Lib/ssl.py
index b6161d0..f253769 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -355,13 +355,20 @@
self = _SSLContext.__new__(cls, protocol)
return self
- def __init__(self, protocol=PROTOCOL_TLS):
- self.protocol = protocol
+ def _encode_hostname(self, hostname):
+ if hostname is None:
+ return None
+ elif isinstance(hostname, str):
+ return hostname.encode('idna').decode('ascii')
+ else:
+ return hostname.decode('ascii')
def wrap_socket(self, sock, server_side=False,
do_handshake_on_connect=True,
suppress_ragged_eofs=True,
server_hostname=None, session=None):
+ # SSLSocket class handles server_hostname encoding before it calls
+ # ctx._wrap_socket()
return self.sslsocket_class(
sock=sock,
server_side=server_side,
@@ -374,8 +381,12 @@
def wrap_bio(self, incoming, outgoing, server_side=False,
server_hostname=None, session=None):
- sslobj = self._wrap_bio(incoming, outgoing, server_side=server_side,
- server_hostname=server_hostname)
+ # Need to encode server_hostname here because _wrap_bio() can only
+ # handle ASCII str.
+ sslobj = self._wrap_bio(
+ incoming, outgoing, server_side=server_side,
+ server_hostname=self._encode_hostname(server_hostname)
+ )
return self.sslobject_class(sslobj, session=session)
def set_npn_protocols(self, npn_protocols):
@@ -389,6 +400,19 @@
self._set_npn_protocols(protos)
+ def set_servername_callback(self, server_name_callback):
+ if server_name_callback is None:
+ self.sni_callback = None
+ else:
+ if not callable(server_name_callback):
+ raise TypeError("not a callable object")
+
+ def shim_cb(sslobj, servername, sslctx):
+ servername = self._encode_hostname(servername)
+ return server_name_callback(sslobj, servername, sslctx)
+
+ self.sni_callback = shim_cb
+
def set_alpn_protocols(self, alpn_protocols):
protos = bytearray()
for protocol in alpn_protocols:
@@ -448,6 +472,10 @@
return True
@property
+ def protocol(self):
+ return _SSLMethod(super().protocol)
+
+ @property
def verify_flags(self):
return VerifyFlags(super().verify_flags)
@@ -749,7 +777,7 @@
raise ValueError("check_hostname requires server_hostname")
self._session = _session
self.server_side = server_side
- self.server_hostname = server_hostname
+ self.server_hostname = self._context._encode_hostname(server_hostname)
self.do_handshake_on_connect = do_handshake_on_connect
self.suppress_ragged_eofs = suppress_ragged_eofs
if sock is not None:
@@ -781,7 +809,7 @@
# create the SSL object
try:
sslobj = self._context._wrap_socket(self, server_side,
- server_hostname)
+ self.server_hostname)
self._sslobj = SSLObject(sslobj, owner=self,
session=self._session)
if do_handshake_on_connect: