[Python-checkins] cpython (3.5): Issues #27850 and #27766: Remove 3DES from ssl default cipher list and add

Tue Sep 6 14:12:03 EDT 2016

https://hg.python.org/cpython/rev/d2111109fd77
changeset: 103124:d2111109fd77
branch: 3.5
parent: 103119:2c4359ff4d6d
user: Christian Heimes <christian at python.org>
date: Tue Sep 06 20:06:47 2016 +0200
summary:
 Issues #27850 and #27766: Remove 3DES from ssl default cipher list and add ChaCha20 Poly1305.
files:
 Doc/library/ssl.rst | 6 +++++
 Lib/ssl.py | 36 +++++++++++++++++++-------------
 Misc/NEWS | 6 +++++
 3 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -279,6 +279,12 @@
 
 RC4 was dropped from the default cipher string.
 
+ .. versionchanged:: 3.5.3
+
+ ChaCha20/Poly1305 was added to the default cipher string.
+
+ 3DES was dropped from the default cipher string.
+
 
 Random generation
 ^^^^^^^^^^^^^^^^^
diff --git a/Lib/ssl.py b/Lib/ssl.py
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -157,36 +157,42 @@
 else:
 CHANNEL_BINDING_TYPES = []
 
+
 # Disable weak or insecure ciphers by default
 # (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
 # Enable a better set of ciphers by default
 # This list has been explicitly chosen to:
 # * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE)
 # * Prefer ECDHE over DHE for better performance
-# * Prefer any AES-GCM over any AES-CBC for better performance and security
+# * Prefer AEAD over CBC for better performance and security
+# * Prefer AES-GCM over ChaCha20 because most platforms have AES-NI
+# (ChaCha20 needs OpenSSL 1.1.0 or patched 1.0.2)
+# * Prefer any AES-GCM and ChaCha20 over any AES-CBC for better
+# performance and security
 # * Then Use HIGH cipher suites as a fallback
-# * Then Use 3DES as fallback which is secure but slow
-# * Disable NULL authentication, NULL encryption, and MD5 MACs for security
-# reasons
+# * Disable NULL authentication, NULL encryption, 3DES and MD5 MACs
+# for security reasons
 _DEFAULT_CIPHERS = (
- 'ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+HIGH:'
- 'DH+HIGH:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+HIGH:RSA+3DES:!aNULL:'
- '!eNULL:!MD5'
-)
+ 'ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:'
+ 'ECDH+AES128:DH+AES:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:'
+ '!aNULL:!eNULL:!MD5:!3DES'
+ )
 
 # Restricted and more secure ciphers for the server side
 # This list has been explicitly chosen to:
 # * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE)
 # * Prefer ECDHE over DHE for better performance
-# * Prefer any AES-GCM over any AES-CBC for better performance and security
+# * Prefer AEAD over CBC for better performance and security
+# * Prefer AES-GCM over ChaCha20 because most platforms have AES-NI
+# * Prefer any AES-GCM and ChaCha20 over any AES-CBC for better
+# performance and security
 # * Then Use HIGH cipher suites as a fallback
-# * Then Use 3DES as fallback which is secure but slow
-# * Disable NULL authentication, NULL encryption, MD5 MACs, DSS, and RC4 for
-# security reasons
+# * Disable NULL authentication, NULL encryption, MD5 MACs, DSS, RC4, and
+# 3DES for security reasons
 _RESTRICTED_SERVER_CIPHERS = (
- 'ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+HIGH:'
- 'DH+HIGH:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+HIGH:RSA+3DES:!aNULL:'
- '!eNULL:!MD5:!DSS:!RC4'
+ 'ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:'
+ 'ECDH+AES128:DH+AES:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:'
+ '!aNULL:!eNULL:!MD5:!DSS:!RC4:!3DES'
 )
 
 
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -60,6 +60,12 @@
 Library
 -------
 
+- Issue #27850: Remove 3DES from ssl module's default cipher list to counter
+ measure sweet32 attack (CVE-2016-2183).
+
+- Issue #27766: Add ChaCha20 Poly1305 to ssl module's default ciper list.
+ (Required OpenSSL 1.1.0 or LibreSSL).
+
 - Issue #26470: Port ssl and hashlib module to OpenSSL 1.1.0.
 
 - Remove support for passing a file descriptor to os.access. It never worked but
-- 
Repository URL: https://hg.python.org/cpython
