Re: Problem with name resolving on Centos 7

Peter Pentchev <[email protected]> Wed, 13 Feb 2019 15:54:31 +0200
Newsgroups	gmane.network.stunnel.user
Message-ID	<[email protected]>
On Wed, Feb 13, 2019 at 02:31:00PM +0100, Flo Rance wrote:
> 
> On Wed, Feb 13, 2019 at 1:23 PM Peter Pentchev <[email protected]> wrote:
> 
> > On Wed, Feb 13, 2019 at 01:12:54PM +0100, Flo Rance wrote:
> > > Regards,
> > > Flo
> > >
> > > On Wed, Feb 13, 2019 at 1:00 PM tom <[email protected]> wrote:
> > >
> > > > Hello,
> > > >
> > > > > Are you sure 'foobar.remote.site' should resolve?
> > > > > Does "ping foobar.remote.site" work?
> > > >
> > > > yes, the host is resolved on commandline and other services on this
> > > > system can reach this host.
> > > >
> > > >
> > > > > Do you have a /var/run/stunnel/etc/resolv.conf file?
> > > >
> > > > No at this time I dont have this file, but it doesnt change anything
> > > > if I copy the original from /etc to this lokation. But this brings me
> > > > to the point try to dissable chroot and in this case stunnel is
> > > > working as expected. So far so good - there is something wrong in the
> > > > chroot jail.
> > > >
> > > > I try to put it to /var/run/stunnel - no luck, but maybe there are
> > > > other files missing as well?
> > >
> > > If you want to resolv hostnames using resolv.conf file, you need the
> > > appropriate library libresolv which is part of libc.
> > > So you'll need to copy the libc librairies in your chroot environment.
> >
> > Mmm, I don't think that the resolver libraries are loaded dynamically;
> > they are usually loaded in the stunnel binary at startup.
>
> Ok, but in that case you should remove "delay = yes" and the hostname will
> be resolved at startup, before chroot

This would be true if the resolver libraries are loaded dynamically...
which seems to be true.  I just found a CentOS 7 system to test on, and
it seems that libnss loads its modules dynamically, grrrrr.

OK, so, tom, you should also find your libnss_* libraries - the easiest
way is through `ldconfig -p | fgrep -e libnss_files` - and copy all of
the libnss_*.so* (both the *.so ones and the *.so.something ones) into
the corresponding directories in your chroot.  I believe that the ones
in the /lib64 directory should be enough - e.g. I think that it might be
enough to do this:

  mkdir /var/run/stunnel/lib64
  cp -p /lib64/libnss_*.so* /var/run/stunnel/lib64/

...but if this doesn't work, you should also copy all others from all
the directories mentioned in the `ldconfig -p | fgrep -e libnss_files`
output.

Sorry for doubting the "dynamically loaded resolver modules" idea at
first :(

G'luck,
Peter

-- 
Peter Pentchev  roam@{ringlet.net,debian.org,FreeBSD.org} [email protected]
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