diff options
author | Christian Heimes <cheimes@redhat.com> | 2016-01-21 16:09:10 +0100 |
---|---|---|
committer | Martin Basti <mbasti@redhat.com> | 2016-02-11 10:44:29 +0100 |
commit | 5ac3a3cee534a16db86c541b9beff4939f03410e (patch) | |
tree | d0aff8d1bb1d4976e99120b01976bf1ccf293beb /contrib | |
parent | 42d364427606e39486645e4064ca16940b2f8837 (diff) | |
download | freeipa-5ac3a3cee534a16db86c541b9beff4939f03410e.tar.gz freeipa-5ac3a3cee534a16db86c541b9beff4939f03410e.tar.xz freeipa-5ac3a3cee534a16db86c541b9beff4939f03410e.zip |
Modernize mod_nss's cipher suites
The list of supported TLS cipher suites in /etc/httpd/conf.d/nss.conf
has been modernized. Insecure or less secure algorithms such as RC4,
DES and 3DES are removed. Perfect forward secrecy suites with ephemeral
ECDH key exchange have been added. IE 8 on Windows XP is no longer
supported.
The list of enabled cipher suites has been generated with the script
contrib/nssciphersuite/nssciphersuite.py.
TLS_RSA_WITH_AES_128_CBC_SHA256
TLS_RSA_WITH_AES_256_CBC_SHA256
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
TLS_RSA_WITH_AES_128_GCM_SHA256
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_RSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_256_CBC_SHA
https://fedorahosted.org/freeipa/ticket/5589
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>
Diffstat (limited to 'contrib')
-rw-r--r-- | contrib/nssciphersuite/README.txt | 36 | ||||
-rwxr-xr-x | contrib/nssciphersuite/nssciphersuite.py | 147 |
2 files changed, 183 insertions, 0 deletions
diff --git a/contrib/nssciphersuite/README.txt b/contrib/nssciphersuite/README.txt new file mode 100644 index 000000000..c36594b9b --- /dev/null +++ b/contrib/nssciphersuite/README.txt @@ -0,0 +1,36 @@ +Cipher suite for mod_nss +------------------------ + +The nssciphersuite.py script parses mod_nss' nss_engine_cipher.c file and +creates a list of secure cipher suites for TLS. The script filters out +insecure, obsolete and slow ciphers according to some rules. + +As of January 2016 and mod_nss 1.0.12 the cipher suite list contains 14 +cipher suites for TLS 1.0, 1.1 and 1.2 for RSA and ECDSA certificates. The +cipher suite list also supports Perfect Forward Secrecy with ephemeral ECDH +key exchange. https://www.ssllabs.com/ gives a 'A' grade. + +Note: +No suite is compatible with IE 8 and earlier on Windows XP. If you need IE 8 +support, append "+rsa_3des_sha" to enable TLS_RSA_WITH_3DES_EDE_CBC_SHA. + +# disabled cipher attributes: SSL_3DES, SSL_CAMELLIA, SSL_CAMELLIA128, SSL_CAMELLIA256, SSL_DES, SSL_DSS, SSL_MD5, SSL_RC2, SSL_RC4, SSL_aDSS, SSL_aNULL, SSL_eNULL, SSL_kECDHe, SSL_kECDHr, kECDH +# weak strength: SSL_EXPORT40, SSL_EXPORT56, SSL_LOW, SSL_STRONG_NONE +# enabled cipher suites: +# TLS_RSA_WITH_AES_128_CBC_SHA256 +# TLS_RSA_WITH_AES_256_CBC_SHA256 +# TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 +# TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA +# TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 +# TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA +# TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 +# TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA +# TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 +# TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA +# TLS_RSA_WITH_AES_128_GCM_SHA256 +# TLS_RSA_WITH_AES_128_CBC_SHA +# TLS_RSA_WITH_AES_256_GCM_SHA384 +# TLS_RSA_WITH_AES_256_CBC_SHA +# + +NSSCipherSuite +aes_128_sha_256,+aes_256_sha_256,+ecdhe_ecdsa_aes_128_gcm_sha_256,+ecdhe_ecdsa_aes_128_sha,+ecdhe_ecdsa_aes_256_gcm_sha_384,+ecdhe_ecdsa_aes_256_sha,+ecdhe_rsa_aes_128_gcm_sha_256,+ecdhe_rsa_aes_128_sha,+ecdhe_rsa_aes_256_gcm_sha_384,+ecdhe_rsa_aes_256_sha,+rsa_aes_128_gcm_sha_256,+rsa_aes_128_sha,+rsa_aes_256_gcm_sha_384,+rsa_aes_256_sha diff --git a/contrib/nssciphersuite/nssciphersuite.py b/contrib/nssciphersuite/nssciphersuite.py new file mode 100755 index 000000000..dee05d470 --- /dev/null +++ b/contrib/nssciphersuite/nssciphersuite.py @@ -0,0 +1,147 @@ +#!/usr/bin/python3 +# +# Authors: +# Christian Heimes <cheimes@redhat.com> +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; version 2 of the License. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License along +# with this program; if not, write to the Free Software Foundation, Inc., +# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. +# +# Copyright (C) 2016 Red Hat, Inc. +# All rights reserved. +# +"""Generate safe NSSCipherSuite stanza for mod_nss +""" +from __future__ import print_function + +import operator +import re +from urllib.request import urlopen # pylint: disable=no-name-in-module + +SOURCE = "https://git.fedorahosted.org/cgit/mod_nss.git/plain/nss_engine_cipher.c" + +CIPHER_RE = re.compile( + r'\s*\{' + r'\"(?P<name>\w+)\",\s*' + r'(?P<num>(TLS|SSL)_\w+),\s*' + r'\"(?P<openssl_name>[\w-]+)\",\s*' + r'(?P<attr>[\w|]+),\s*' + r'(?P<version>\w+),\s*' + r'(?P<strength>\w+),\s*' + r'(?P<bits>\d+),\s*' + r'(?P<alg_bits>\d+)' +) + +DISABLED_CIPHERS = { + # ciphers without encryption or authentication + 'SSL_eNULL', 'SSL_aNULL', + # MD5 is broken + # SHA-1 is still required as PRF algorithm for TLSv1.0 + 'SSL_MD5', + # RC2 and RC4 stream ciphers are broken. + 'SSL_RC2', 'SSL_RC4', + # DES is broken and Triple DES is too weak. + 'SSL_DES', 'SSL_3DES', + # DSA is problematic. + 'SSL_DSS', 'SSL_aDSS', + # prefer AES over Camellia. + 'SSL_CAMELLIA128', 'SSL_CAMELLIA256', 'SSL_CAMELLIA', + # non-ephemeral EC Diffie-Hellmann with fixed parameters are not + # used by common browser and are therefore irrelevant for HTTPS. + 'kECDH', 'SSL_kECDHr', 'SSL_kECDHe' +} + +WEAK_STRENGTH = { + 'SSL_STRONG_NONE', + 'SSL_EXPORT40', + 'SSL_EXPORT56', + 'SSL_LOW' +} + + +def parse_nss_engine_cipher(lines, encoding='utf-8'): + """Parse nss_engine_cipher.c and get list of ciphers + + :param lines: iterable or list of lines + :param encoding: default encoding + :return: list of cipher dicts + """ + ciphers = [] + start = False + for line in lines: + if not isinstance(line, str): + line = line.decode(encoding) + + if line.startswith('cipher_properties'): + start = True + elif not start: + continue + elif line.startswith('};'): + break + + mo = CIPHER_RE.match(line) + if not mo: + continue + + match = mo.groupdict() + match['attr'] = set(match['attr'].split('|')) + match['bits'] = int(match['bits']) + match['alg_bits'] = int(match['alg_bits']) + + # some cipher elemets aren't flagged + for algo in ['SHA256', 'SHA384']: + if match['num'].endswith(algo): + match['attr'].add('SSL_{}'.format(algo)) + + # cipher block chaining isn't tracked + if '_CBC' in match['num']: + match['attr'].add('SSL_CBC') + + if match['attr'].intersection(DISABLED_CIPHERS): + match['enabled'] = False + elif match['strength'] in WEAK_STRENGTH: + match['enabled'] = False + else: + match['enabled'] = True + + # EECDH + AES-CBC and large hash functions is slow and not more secure + if (match['attr'].issuperset({'SSL_CBC', 'SSL_kEECDH'}) and + match['attr'].intersection({'SSL_SHA256', 'SSL_SHA384'})): + match['enabled'] = False + + ciphers.append(match) + + ciphers.sort(key=operator.itemgetter('name')) + return ciphers + + +def main(): + with urlopen(SOURCE) as r: + ciphers = parse_nss_engine_cipher(r) + # with open('nss_engine_cipher.c') as f: + # ciphers = parse_nss_engine_cipher(f) + + print("# disabled cipher attributes: {}".format( + ', '.join(sorted(DISABLED_CIPHERS)))) + print("# weak strength: {}".format(', '.join(sorted(WEAK_STRENGTH)))) + print("# enabled cipher suites:") + suite = [] + for cipher in ciphers: + if cipher['enabled']: + print("# {:36}".format(cipher['num'])) + suite.append('+{}'.format(cipher['name'])) + print() + print("NSSCipherSuite {}".format(','.join(suite))) + + +if __name__ == '__main__': + main() |