Maintained by: NLnet Labs

Unbound not always resolving immediately after start.

W.C.A. Wijngaards
Tue Sep 22 09:30:48 CEST 2015


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Hi Tomas,

On 15/09/15 09:55, Tomas Hozza via Unbound-users wrote:
> On 14.09.2015 14:15, Daisuke HIGASHI via Unbound-users wrote:
>> Hi,
>> 
>> SERVFAIL on tweakers.net seems to be from fix on CVE-2014-8500. 
>> This fix essentially limits number of query (to authoritative
>> servers) to resolve target qname. If a qname requires many query
>> to resolve it becomes SERVFAIL This situation often occurs when
>> cache is empty (e.g. just after starting unbound or cache flush)
>> 
>> bind-users have discussed same issue last year: 
>> https://lists.isc.org/pipermail/bind-users/2014-December/thread.html
>>
>>
>> 
Possible workarounds are to increase MAX_TARGET_COUNT
>> (iterator/iterator.h) to relax number of query limitation but it
>> may reduce robustness against CVE-2014-8500-related attack.
> 
> I think it is worth considering not having to recompile Unbound. It
> would be much nicer to have this configurable in unbound.conf. 
> Something similar like BIND allows by max-recursion-queries
> option.

What value should we use for MAX_TARGET_COUNT?   I'll increase the
compiled default to that value.  Easier than a configuration option
that the user can get wrong and then be vulnerable.

Best regards,
   Wouter

> 
> Tomas
> 
>> Regards, -- Daisuke HIIGASHI
>> 
>> 
>> 2015-09-11 18:39 GMT+09:00 Frank de Bot via Unbound-users 
>> <unbound-users at unbound.net>:
>>> Hi,
>>> 
>>> Under FreeBSD I'm setting up a resolv-only unbound server.
>>> While testing I've noticed some domain do not resolve (server
>>> returns SERVFAIL)
> 

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