During the summer rumours about a new attack against SSL started circulating (CVE-2011-3389).
As it turns out, the attack itself was conceived years ago, deemed impractical, but it was nevertheless fixed in TLS 1.1. The new attack technique introduced a few optimizations to make it practical.
In terms of mitigation, I expect this problem will be largely addressed on the client side, despite a potential compatibility problem that may cause some TLS sites to stop working.
With this config you can avoid that attack.
SSLProtocol all -SSLv2 SSLHonorCipherOrder On SSLCipherSuite ECDHE-RSA-AES256-SHA384:AES256-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH:!AESGCM:!SSLV2:!eNULL #NO Longer needed cause since IE 7 this works ;) #SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown
With OpenSSL 1.0.1 it must be
SSLCipherSuite ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH
Well I haven’t figured out how to use 256 bit again. This leaves only 128 bit.
The Problem is in the CBC mode of all Block Chiffres. So the fix is to prefer RC4-128-SHA (which is a stream chiffre). I dont see how AES256 would help.
BTW: PReferences for RC4 is a Google.com default for years. Not only because it is low cpu.
Bernd
Oh I actually found the answer, the AES256 are supposed to be TLSv1.2 ciphers (which is not supported by OpenSSL yet). with TLS 1.2 it is not vulnerable, of course.
With OpenSSL 1.0.
it must be
SSLCipherSuite ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH
what about this line?
SetEnvIf User-Agent “.*MSIE.*” nokeepalive ssl-unclean-shutdown
adding this in causes all IE browsers to not use keepalive resulting in slower load times for all requests (not just SSL ones) is there a solution to this issue? i’ve searched and tried wrapping it in IFmodule mod_ssl.c tags but that didnt work.
then i tried this instead, it works but not sure its proper
BrowserMatch “MSIE [1-4]” nokeepalive ssl-unclean-shutdown downgrade-1.0 force-response-1.0
BrowserMatch “MSIE [5-9]” ssl-unclean-shutdown
Thoughts?
John
That is not needed anymore. From IE 7 on IE supports keep Alive with
SSL and apache. So kick that out of the apache config.
awesome thanks!