Re: [exim] Exim + grsecurity + ssl = dos

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Author: Samuel
Date:  
To: exim-users
Subject: Re: [exim] Exim + grsecurity + ssl = dos

Le 01/06/2016 à 11:24, Jeremy Harris a écrit :
> On 31/05/16 18:44, Samuel wrote:
>> 2016-05-31 05:55:44 TLS error on connection from
>> researchscan258.eecs.XXXX.edu (eecs.XXXX.edu) [1XX.212.XXX.3]
>> (gnutls_handshake): Could not negotiate a supported cipher suite.
>> 2016-05-31 05:55:44 H=researchscan258.eecs.XXXX.edu (eecs.XXXX.edu)
>> [1XX.212.XXX.3] Warning: erreur : tls-failed
> OK, cipher-suite mismatch...
>
>> /var/log/syslog :
>>
>> May 31 05:55:44 anemone-mailin-01 kernel: [4547900.677897] traps:
>> exim4[23055] general protection ip:6664ddc0bad6 sp:7483826d3710 error:0
>> in libc-2.19.so[6664ddba2000+1a2000]
> Oops!
>
>> So if I understand well, A special craft ssl request can cause DOS on
>> Exim on Grsecurity kernel ?
> Not all that crafted; just a choice of ciphers.


Is this a problem from my side ? Do I have to do someting ?

>> What can I do to stop this ?
> Gather more information so that we can fix the bug where the crash is.
> A full stack trace of the crash point, with debuginfo. Generally this
> means enabling suid-process coredumps though, and this is a security
> issue (the coredump potentially contains sensitive info, so you
> don't want just anyone to be able to read the file).
>
> Also: any idea if this was STARTTLS or SSL-on-connect?


I can't see it for this connexion.
I just now enable logging in connect acl for that port :

warn
     log_message = $received_port


So if it happens again I will now the connect port.

> Cheers,
>    Jeremy


Thanks.
Samuel.