8000 [3.4] Issues #27850 and #27766: Remove 3DES from ssl default cipher list an… by vstinner · Pull Request #224 · python/cpython · GitHub
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[3.4] Issues #27850 and #27766: Remove 3DES from ssl default cipher list an… #224

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Merged
merged 1 commit into from
Mar 10, 2017
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[3.4] Issues #27850 and #27766: Remove 3DES from ssl default cipher list an… #224

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6 changes: 6 additions & 0 deletions Doc/library/ssl.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,12 @@ purposes.

RC4 was dropped from the default cipher string.

.. versionchanged:: 3.4.7

ChaCha20/Poly1305 was added to the default cipher string.

3DES was dropped from the default cipher string.


Random generation
^^^^^^^^^^^^^^^^^
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36 changes: 21 additions & 15 deletions Lib/ssl.py
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Expand Up @@ -160,36 +160,42 @@ def _import_symbols(prefix):
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'
)


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2 changes: 2 additions & 0 deletions Misc/NEWS
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Expand Up @@ -13,6 +13,8 @@ Core and Builtins
Library
-------

- Issue #27850: Remove 3DES from ssl module's default cipher list to counter
measure sweet32 attack (CVE-2016-2183).

What's New in Python 3.4.6?
===========================
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0