cyrus-imap patching POODLE and another for adding perfect forward secrecy (PFS)

[Kristian Kræmmer Nielsen]

Hi Geoff,

I am basically not trying to take any stand on this. I just think it is  
time for the users to be able to disable the older protocols if they want  
to - as the old protocols are really no longer necessary for the wide  
majority of clients - and that is the main reasoning by my patches.

Notice that is also way I leave it false (changing nothing) by default in  
the patch.

For reference, you can see this for Ubuntu, they recommend total disabling  
SSLv3:
http://askubuntu.com/questions/537196/how-do-i-patch-workaround-sslv3-poodle-vulnerability-cve-2014-3566
"Conclusion: disable SSLv3 for HTTPS now, disable SSLv3 for other services  
in your next service window."

So, hope my patches get merged soon :)

/Kristian

On Thu, 16 Oct 2014 11:34:21 +0200, Geoff Winkless <cyrus at geoff.dj> wrote:

> Hi Kristian
>
> Firstly, many thanks for your work :)
>
> Can you share the source for those recommendations? While I fully agree  
> that using something that is shown to be >vulnerable is not ideal I'd be  
> interested to see how they think a similar attack to POODLE could be  
> implemented for >imap. As I posted to the info list, I've not seen  
> anything that would suggest that IMAPS/SSLv3 is any less secure than >it  
> was 10 years ago.
>
> Thanks
>
>
> On 16 October 2014 02:55, Kristian Kræmmer Nielsen <jkkn at jkkn.dk> wrote:
>> Hi,
>>
>> Two patches for merging....
>>
>> Thanks for the great work on cyrus imapd.
>>
>> I have just read various recommendations that we now should disable  
>> SSLv3 not just on HTTPS as POODLE-attack demonstrates but we should  
>> >>expect to see exploits on other services as well like IMAPS and POPS.
>>
>> I saw that disabling SSLv2 and SSLv3 in fact is already available in  
>> the tls-code but not made available to the user so therefore I have  
>> written the >>attached patch to do just that using a configuration  
>> variable named "tls_tlsonly". It is still by default false, so the  
>> patch should change nothing for >>users that still want to use the old  
>> protocols and may stay that way until an actual imaps-attack is proven.
>>
>> Also I am including a cleaned up version of Chris Panayis' old patch  
>> for adding tls_ec for Perfect Forward Secrecy:
>> https://lists.andrew.cmu.edu/pipermail/cyrus-devel/2013-January/002729.html
>>
>> Using PFS is also a security recommendation we should follow. The  
>> default is set to prime256v1 just as sendmail and apache does this.
>>
>> The patches are made against cyrus-imap-2.4.17 - but they also cleanly  
>> patch against the tip of the git repository of cyrus-imapd if skipping  
>> the >>patch of the man-page.
>>
>> PFS: https://scotthelme.co.uk/perfect-forward-secrecy/
>> POODLE:  
>> https://www.dfranke.us/posts/2014-10-14-how-poodle-happened.html and  
>> https://www.openssl.org/~bodo/ssl-poodle.pdf
>>
>> Regards
>> Kristian Kræmmer Nielsen,
>> Odense, Denmark
>> ----
>> Cyrus Home Page: http://www.cyrusimap.org/
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