Bug in cyrus-sasl with GSSAPI, encoded packet size too big (4156 > 4096)

[Jakub Jelen]

On 02/08/2016 05:55 PM, Matt Hoyle via Cyrus-sasl wrote:
> Sorry, I completely forgot the link: 
> https://bugzilla.redhat.com/show_bug.cgi?id=1205878
>
> On 02/08/2016 11:45 AM, Quanah Gibson-Mount wrote:
>> --On Monday, February 08, 2016 10:22 AM -0500 Matt Hoyle via 
>> Cyrus-sasl <cyrus-sasl at lists.andrew.cmu.edu> wrote:
>>
>>> Please view my bug submitted to RedHat for more details on my setup and
>>> configuration. At this point they would like the cyrus-sasl devs to 
>>> take
>>> a look and see if they can help in any way.
>>
>> Then I would suggest you provide a link to the bug you filed with RH.
Hi all cyrus (sasl) fans,

I spent quite some time playing with this environment and I am able to 
reproduce the bug also in my environment. But frankly I ran out of ideas 
where to look and to debug the problem further.

We have workaround patch, which makes it working somehow (thanks Matt), 
but I would personally like to understand what is going on there. For 
somebody better versed in GSSAPI or SASL protocol, it might be obvious. 
On first sight it looks like somehow messed up message size, but it is 
fixed by setting "proper" sasldata/input_token/qop during connection 
initialization.

Basically connections using GSSAPI between server

     (cyrus-master)-lmtpd
and clients
     (postfix)-lmtp
     (cyrus-impad)-deliver

ends with the above message "encoded packet size too big (4156 > 4096)". 
Always with the same numbers.

See the above linked bugzilla for more details, debug information, 
configuration. I would be glad for every idea where else or how to look 
further. No complete solution required :)

Thanks for reading up to here.

Kind regards,

-- 
Jakub Jelen
Security Technologies
Red Hat