Issue #13636: Weak ciphers are now disabled by default in the ssl module

(except when SSLv2 is explicitly asked for).

1 files changed, 10 insertions, 2 deletions

diff --git a/Lib/ssl.py b/Lib/ssl.py
index ce9ebdf30a..8137231711 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -86,8 +86,9 @@ _PROTOCOL_NAMES = {
 }
 try:
     from _ssl import PROTOCOL_SSLv2
+    _SSLv2_IF_EXISTS = PROTOCOL_SSLv2
 except ImportError:
-    pass
+    _SSLv2_IF_EXISTS = None
 else:
     _PROTOCOL_NAMES[PROTOCOL_SSLv2] = "SSLv2"
 
@@ -98,6 +99,10 @@ import base64        # for DER-to-PEM translation
 import traceback
 import errno
 
+# Disable weak or insecure ciphers by default
+# (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
+_DEFAULT_CIPHERS = 'DEFAULT:!aNULL:!eNULL:!LOW:!EXPORT:!SSLv2'
+
 
 class CertificateError(ValueError):
     pass
@@ -165,7 +170,10 @@ class SSLContext(_SSLContext):
     __slots__ = ('protocol',)
 
     def __new__(cls, protocol, *args, **kwargs):
-        return _SSLContext.__new__(cls, protocol)
+        self = _SSLContext.__new__(cls, protocol)
+        if protocol != _SSLv2_IF_EXISTS:
+            self.set_ciphers(_DEFAULT_CIPHERS)
+        return self
 
     def __init__(self, protocol):
         self.protocol = protocol