On (23/08/19 15:56), Jakub Hrozek wrote:
>On Fri, Aug 23, 2019 at 03:46:54PM +0200, Heiko Wundram wrote:
>> Hello list,
>> 
>> for a deployment I'm administering, I'm using winbind and sssd in parallel,
>> both for different authentication sources (so it's not about their
>> interoperability, but rather about using them in parallel). It seems that
>> sssd has/had a bug which meant that winbind 4.8+ and sssd, if used together
>> as NSS sources, would, for unavailable accounts in both authentication
>> sources, lead to a DoS against winbind due to recursive calls of the NSS
>> infrastructure. I'm deploying winbind (for a Windows Domain) and sssd (for
>> an LDAP authentication source with client certificate authentication) on
>> Debian 10.
>> 
>> Samba tracked this as bug #13815
>> (https://bugzilla.samba.org/show_bug.cgi?id=13815), which contains a link to
>> a corresponding issue in the RedHat bugtracker
>> (https://bugzilla.redhat.com/show_bug.cgi?id=1666819), which supposedly
>> contains a patch for the behaviour; as the bug isn't open, I can neither see
>> what the patch actually is, nor can I prepare the patch for the Debian
>> packaging of sssd.
>> 
>> Can anybody shed some light on what the patch is (and/or link to the commit
>> in Pagure), specifically also which published version the patch is contained
>> in, so that I might either decide to deploy updated sssd packages for
>> Debian, or even try to backport the patch to the Debian built-in version? I
>> can't find a means to search commits in Pagure, that's why I'm asking here,
>> but even just that would be helpful.
>> 
>> Thanks in advance!
>
>the corresponding upstream tickets are:
>    https://pagure.io/SSSD/sssd/issue/3963
>and:
>    https://pagure.io/SSSD/sssd/issue/3964
>

If you do not want to backport so many patches
or upgrading to newer version is problem then the simplest change
will be to chage value of CONFDB_RESPONDER_LOCAL_NEG_TIMEOUT_DEFAULT
from 14400 -> 0

It was introduced in 1.16.2
https://pagure.io/SSSD/sssd/issue/3619


>I /think/ it might be possible to work around the bug by setting:
>    local_negative_timeout = 0
>in the [nss] section.

Yep, that's the workaround in sssd.conf.

LS
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