bind 9.11.3 BIND9_FLATFILE update-policy

[Sergey Urushkin]

Rowland Penny писал 2018-10-11 16:21:
> On Thu, 11 Oct 2018 16:10:25 +0300
> Sergey Urushkin <urushkin at telros.ru> wrote:
> 
>> Rowland Penny писал 2018-10-11 15:57:
>> > On Thu, 11 Oct 2018 15:40:25 +0300
>> > Sergey Urushkin <urushkin at telros.ru> wrote:
>> >
>> >> Rowland Penny писал 2018-10-11 12:38:
>> >> > On Thu, 11 Oct 2018 12:01:22 +0300
>> >> > Sergey Urushkin <urushkin at telros.ru> wrote:
>> >> >
>> >> >> Rowland Penny писал 2018-10-10 21:40:
>> >> >> > On Thu, 11 Oct 2018 07:23:37 +1300
>> >> >> > Andrew Bartlett <abartlet at samba.org> wrote:
>> >> >> >
>> >> >> >> On Wed, 2018-10-10 at 14:38 +0300, Sergey Urushkin wrote:
>> >> >> >> > ---
>> >> >> >> > Best regards,
>> >> >> >> > Sergey Urushkin
>> >> >> >> >
>> >> >> >> >
>> >> >> >> > Andrew Bartlett писал 2018-10-10 13:04:
>> >> >> >> > >
>> >> >> >> > > Sergey,
>> >> >> >> > >
>> >> >> >> > > Can you fill us in on your use case here?
>> >> >> >> >
>> >> >> >> > Actually, this is just history. When we were migrating from
>> >> >> >> > samba3 NT domain (that was 4.0 alfa-beta times) DLZ backend
>> >> >> >> > was buggy, didn't work with bind views, didn't support zone
>> >> >> >> > types mixing (plain+dlz), dhcp-dns updates (that's what
>> >> >> >> > left in my memory, I could be wrong). Every of these
>> >> >> >> > problems could be solved in some way, but this required
>> >> >> >> > additional configuring, migration and risks, so we decided
>> >> >> >> > to do this later. Now all that problems seems to be solved
>> >> >> >> > and dlz is really stable, so I don't see any reason for
>> >> >> >> > not using DLZ/INTERNAL for new installations. But since we
>> >> >> >> > still don't need features of DLZ, we are still PLAIN,
>> >> >> >> > that's why I'm voting for supporting this feature :).
>> >> >> >>
>> >> >> >> The only part of this that can't be supported is views, but
>> >> >> >> that could be done on another server (with a zone type of
>> >> >> >> forward pointing at Samba) and leave the Samba server with a
>> >> >> >> simple configuration.
>> >> >>
>> >> >> By view support I meant put dlz inside view (e.g. one view with
>> >> >> dlz, one without; or dlz in both but with different other
>> >> >> zones), what is possible now and, as I remember, was not
>> >> >> possible in the early versions, but I could be wrong.
>> >> >>
>> >> >> >>
>> >> >> >> > May be someone has a configured/patched bind version, so
>> >> >> >> > that dlz breaks it, but I haven't met such. If someone has
>> >> >> >> > plain backend he knows what he is doing (and can fix
>> >> >> >> > config files), so all we need to support this backend
>> >> >> >> > without auto-breaking it in the future - is removing
>> >> >> >> > dns_update.c code. And for new installations we could
>> >> >> >> > describe this backend as DEPRECATED in docs/tools.
>> >> >> >> >
>> >> >> >> > Fixed patch attached.
>> >> >> >>
>> >> >> >> OK, how about this for a plan:
>> >> >> >>
>> >> >> >> * This patch for master, then backported to 4.9 (also
>> >> >> >> removing the dns_update.c code).
>> >> >> >>
>> >> >> >> The rationale is also that we think that kicking bind with a
>> >> >> >> rndc reload can crash bind (sadly we can't reliably
>> >> >> >> reproduce), we can't do
>> >> >> >
>> >> >> > If you run 'bind9 reload' you get this:
>> >> >> >
>> >> >> > Oct 10 19:28:12 dc3 named[5261]: Loading 'AD DNS Zone' using
>> >> >> > driver dlopen
>> >> >> > Oct 10 19:28:12 dc3 named[5261]: samba_dlz: starting configure
>> >> >> > Oct 10 19:28:12 dc3 named[5261]: samba_dlz: Ignoring duplicate
>> >> >> > zone '0.168.192.in-addr.arpa' from
>> >> >> > 'DC=@,DC=0.168.192.in-addr.arpa,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com'
>> >> >> > Oct 10 19:28:12 dc3 named[5261]: samba_dlz: Ignoring duplicate
>> >> >> > zone 'samdom.example.com' from
>> >> >> > 'DC=@,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com'
>> >> >> > Oct 10 19:28:12 dc3 named[5261]: samba_dlz: Ignoring duplicate
>> >> >> > zone '_msdcs.samdom.example.com' from
>> >> >> > 'DC=@,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com'
>> >> >> > Oct 10 19:28:12 dc3 named[5261]: samba_dlz: shutting down
>> >> >> >
>> >> >> >> the version detection at runtime, can't tell if we are in
>> >> >> >> BIND9_FLATFILE and shouldn't be doing that on a timer tick
>> >> >> >> for 99% of installs.
>> >> >>
>> >> >> Agreed.
>> >> >>
>> >> >> >>
>> >> >> >> * Then mark as DEPRECATED and remove BIND9_FLATFILE from
>> >> >> >> provision in master for 4.10.
>> >> >> >>
>> >> >> >
>> >> >> > Good idea.
>> >> >>
>> >> >> BIND9_FLATFILE is the only method to use dns server on another
>> >> >> physical server
>> >> >
>> >> > Yes, but you shouldn't be running the dns server on another
>> >> > server, the dns info is stored in AD.
>> >>
>> >> This is just the simplest way. Actually I could use another server
>> >> which will be getting info from the AD via LDAP (I know it's crazy
>> >> but this will work).
>> >
>> > No the simplest (and the best) is to run Bind9 on the Samba AD DC.
>> 
>> Agreed, I mean exactly this, wrote wrong, sorry for my English.
>> 
>> >>
>> >> >
>> >> >> and/or mix usual bind update keys (e.g.isc-dhcp) with
>> >> >> gssapi update keys for one zone. While I can not tell why
>> >> >> someone would need this with current ready-to-use solutions,
>> >> >> this is possible and fully working configuration (for clients
>> >> >> it is absolutely the same; admins could write it's own update
>> >> >> rules, and use nsupdate instead of samba-tool - I can confirm).
>> >> >
>> >> > And I can confirm that you can use nsupdate with the dns info
>> >> > stored in AD, even with an isc-dhcp-server
>> >>
>> >> I know, I was the one who published such dhcp script in the
>> >> forefront :)
>> >
>> > No you were not, it was started by Michael Kuron, you just updated
>> > his script, just as I did.
>> 
>> I did not say I was the first.
>> 
>> >
>> >>
>> >> >
>> >> >> So why removing?
>> >> >
>> >> > Because it doesn't work as BIND9_DLZ does and how AD expects.
>> >>
>> >> As I know, AD (samba) just needs dns, it doesn't use ldap
>> >> dns-records directly (except for replication and administration
>> >> purposes (samba-tool)).
>> >>
>> >
>> > It needs dns and it creates the records in AD, so the easiest way
>> > is to use those records.
>> 
>> The easiest, not the only. It creates dns-records, not ldap (in
>> common case), that's what I'm talking about.
>> 
>> >
>> >> >
>> >> >> After modifying dns_update.c code, this option will
>> >> >> require minimal support,
>> >> >
>> >> > It will require even less support if it is removed, it was only
>> >> > used because some distro's didn't have a version of bind9 that
>> >> > supported dlz, these distro's are now EOL.
>> >> >
>> >> >
>> >> >> it will not break running installations, I
>> >> >> can imagine minimal config template modification if BIND
>> >> >> developers change something again (will it ever happen?).
>> >> >> I'm talking about DEPRECATED -> NOT RECOMMENDED and describing
>> >> >> this in the docs.
>> >> >>
>> >> >> Or if you really-really want to remove this, we could at least
>> >> >> write some info about possibility of using bind9 with the flat
>> >> >> files in the docs/mans/wiki.
>> >> >>
>> >> >
>> >> > Why would we want to tell people about using something that has
>> >> > been removed ?
>> >>
>> >> We are removing config generation, not an ability to use side dns
>> >> server.
>> >> Until we stop using nsupdate for records update, we may use another
>> >> server with tkey-gss support (or even without it).
>> >>
>> >> >
>> >> >> Also, I have tested the patch before sending - it works for me.
>> >> >
>> >> > Yes, it may work in the way you perceive to be correct, but it
>> >> > isn't a supported way and probably isn't working as AD requires.
>> >>
>> >> I really don't understand what "AD requires" means, except ACLs.
>> >> Incorrect ACLs in the update-policy could lead to security holes
>> >> ("administrator" is not dns/domain admin in LDAP) - and that is the
>> >> reason to not support PLAIN in the base installation (among other
>> >> reasons you mentioned). But even MS AD could be run with dns
>> >> security updates disabled (you may see that the first try of
>> >> updating dns-record from windows machine goes without auth).
>> >>
>> >> I will not be surprised if one of my installations is the only one
>> >> with the flat files :) So, if you think this should be removed, I
>> >> don't mind. But we might mention this possibility in docs (shortly,
>> >> even without examples):
>> >> "Samba AD could potentially be used with any dns-server that
>> >> supports tkey-gss updates (and even without such support), but
>> >> samba team doesn't recommend this and doesn't provide support.
>> >> This may bring security risks."
>> >> This schema is working, until we remove nsupdate support (actually
>> >> even after it - static records). And by this text, we will shield
>> >> users from wrong decisions, which they could make even without our
>> >> support in the provision script.
>> >>
>> >> Just MHO, thanks.
>> >>
>> >> >
>> >> > Rowland
>> >> >
>> >> >>
>> >> >> >
>> >> >> >> We can do this on a more accelerated schedule than normal
>> >> >> >> because existing installations, unchanged, won't notice
>> >> >> >> anything.
>> >> >> >>
>> >> >> >> What do you think?  Alternately it might be simpler to just:
>> >> >> >>
>> >> >> >> * Remove the provision and dns_update.c code from master for
>> >> >> >> 4.10, leave 4.9 alone.  Bypass our normal feature deprecation
>> >> >> >> rules because existing installs will continue to just work,
>> >> >> >> add a note to WHATSNEW.
>> >> >> >>
>> >> >> >
>> >> >> > No, I think we should stick to the deprecate, then remove
>> >> >> > method, just do it faster this time.
>> >> >> >
>> >> >> > Rowland
>> >> >>
>> >> >>
>> >> >> ---
>> >> >> Best regards,
>> >> >> Sergey Urushkin
>> >
>> > Have you ever heard of the term 'Flogging a dead horse' ???
>> 
>> Yes. And that's why I do not insist on saving this feature. But
>> someone may flog - and this suggested text in the documentation for
>> him.
> 
> Okay, I have added a warning using your text to the wikipage here:
> https://wiki.samba.org/index.php/Setting_up_a_BIND_DNS_Server


Thanks!

> 
> Rowland