[Triumf-linux-managers] FYI - BEAST attack mitigation in SSL

[Andrew Daviel]

FYI

Per e.g. http://www.ekoparty.org/2011/juliano-rizzo.php, there is a 
vulnerability in block-chained ciphers in SSL.

Per http://www.phonefactor.com/blog/slaying-beast-mitigating-the-latest-ssltls-vulnerability.php
one can modify the Apache mod_ssl configuration (usually in 
/etc/httpd/conf.d/ssl.conf, or per-virtual-host) to mitigate this.

Suggested entries are:
SSLHonorCipherOrder on
SSLCipherSuite !aNULL:!eNULL:!EXPORT:!DSS:!DES:RC4-SHA:RC4-MD5:ALL
SSLProtocol all -SSLv2

Note that SSLHonorCipherOrder is not supported in Apache http prior to 
version 2.2 (so comment it out)

Older servers may support SSLv2 and export-grade ciphers. These are not 
required since 2000 when the US relaxed export regulations on commodity 
crypto software (except to "terrorist countries" like Cuba and Iran who I 
don't imagine have much trouble getting a recent Firefox).

FYI, there is an online tester at Qualys at https://www.ssllabs.com/ssldb/index.html
which will check server issues. I also have a Perl script which will 
check the server preferred order. The standard tool "sslscan" (from yum) 
will enumerate all supported ciphers and protocols and give details of 
the server certificate.

- I don't think this is a significant vulnerability for us. It's more a 
question of "optics" in view of the Qualys scanner that can be used by 
anyone to test other people's servers, and it's a quick fix to patch 
server configs.

- FYI, presentation at BlackHat conference on internet-wide SSL support:
http://blog.ivanristic.com/2010/07/internet-ssl-survey-2010-is-here.html


-- 
Andrew Daviel, TRIUMF, Canada
Tel. +1 (604) 222-7376  (Pacific Time)
Network Security Manager