[Freeipa-devel] [PATCH 0083] perform an unlimited search for reverse zones when adding DNS records
Petr Spacek
pspacek at redhat.com
Tue Oct 13 14:00:22 UTC 2015
On 13.10.2015 13:37, Martin Babinsky wrote:
> On 10/13/2015 09:36 AM, Petr Spacek wrote:
>> On 12.10.2015 16:35, Martin Babinsky wrote:
>>> https://fedorahosted.org/freeipa/ticket/5200
>>> ---
>>> ipalib/plugins/dns.py | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/ipalib/plugins/dns.py b/ipalib/plugins/dns.py
>>> index
>>> 84086f4c77d02922f237937d58031cc42d55410e..c36345faecfb9db7abced1c6bd72ddcf93473a74
>>> 100644
>>> --- a/ipalib/plugins/dns.py
>>> +++ b/ipalib/plugins/dns.py
>>> @@ -537,7 +537,8 @@ def get_reverse_zone(ipaddr, prefixlen=None):
>>> if prefixlen is None:
>>> revzone = None
>>>
>>> - result = api.Command['dnszone_find']()['result']
>>> + result = api.Command['dnszone_find'](sizelimit=0)['result']
>>> +
>>
>> NACK, this just increases the limit because LDAP server will enforce a
>> per-user limit.
>>
>>> for zone in result:
>>> zonename = zone['idnsname'][0]
>>> if (revdns.is_subdomain(zonename.make_absolute()) and
>>
>> Generic solution should use dns.resolver.zone_for_name() to find DNS zone
>> matching the reverse name. This should also implicitly cover CNAME/DNAME
>> redirections per RFC2317.
>>
>> Using DNS implicitly means that a zone will always be found (at least the root
>> zone :-). For this reason I would change final error message
>>> reason=_('DNS reverse zone for IP address %(addr)s not found')
>> to something like:
>> reason=_('DNS reverse zone %(zone)s for IP address %(addr)s is not managed
>> by this server')
>>
>>
>> These changes should fix it without adding other artificial limitation.
>>
>
> Thank you for clarification Petr.
>
> Attaching the reworked patch.
>
> --
> Martin^3 Babinsky
>
> freeipa-mbabinsk-0083.1-perform-more-robust-search-for-reverse-zones-when-ad.patch
>
>
> From 463903f4ea4f74efeb02dbb705ca0a54fab81366 Mon Sep 17 00:00:00 2001
> From: Martin Babinsky <mbabinsk at redhat.com>
> Date: Mon, 12 Oct 2015 16:24:50 +0200
> Subject: [PATCH 1/3] perform more robust search for reverse zones when adding
> DNS record
>
> Instead of searching for all zones to identify the correct reverse zone, we
> will first ask the resolver to return the name of zone that should contain the
> desired record and then see if IPA manages this zone.
>
> https://fedorahosted.org/freeipa/ticket/5200
> ---
> ipalib/plugins/dns.py | 21 +++++++++++++++++----
> 1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/ipalib/plugins/dns.py b/ipalib/plugins/dns.py
> index 84086f4c77d02922f237937d58031cc42d55410e..e3c6ce46168f8b6af607a61af1e3e431cfee32c8 100644
> --- a/ipalib/plugins/dns.py
> +++ b/ipalib/plugins/dns.py
> @@ -531,25 +531,35 @@ def add_forward_record(zone, name, str_address):
> pass # the entry already exists and matches
>
> def get_reverse_zone(ipaddr, prefixlen=None):
> + """
> + resolve the reverse zone for IP address and see if it is managed by IPA
> + server
> + :param ipaddr: host IP address
> + :param prefixlen: network prefix length
> + :return: tuple containing name of the reverse zone and the name of the
> + record
> + """
> ip = netaddr.IPAddress(str(ipaddr))
> revdns = DNSName(unicode(ip.reverse_dns))
> + resolved_zone = unicode(dns.resolver.zone_for_name(revdns))
>
> if prefixlen is None:
> revzone = None
> + result = api.Command['dnszone_find'](resolved_zone)['result']
>
> - result = api.Command['dnszone_find']()['result']
> for zone in result:
> zonename = zone['idnsname'][0]
> if (revdns.is_subdomain(zonename.make_absolute()) and
> (revzone is None or zonename.is_subdomain(revzone))):
> revzone = zonename
Oh, wait, this might blow up if there is a disabled DNS zone which is deeper
than the one returned from DNS query.
Damn, we have opened a Pandora box!
ipaserver/install/bindinstance.py has own implementation of get_reverse_zone()
+ additional menthods find_reverse_zone().
These are using get_reverse_zone_default() from ipalib/util.py which is
duplicating code in 'if prefixlen is not None' branch.
And of course, are not correct in light of this change.
My expectation would be that disabled zones should be ignored... So we should
get rid of this mess in the loop and use dnszone_show() which is called at the
end. And fix the other places, preferably by deleting duplicate implementations.
I would expect that you can store (converted) output of
dns.resolver.zone_for_name(revdns) into revzone and delete whole 'if prefixlen
is None' branch.
> else:
> + # if prefixlen is specified, determine the zone name for the network
> + # prefix
> if ip.version == 4:
> pos = 4 - prefixlen / 8
> elif ip.version == 6:
> pos = 32 - prefixlen / 4
> - items = ip.reverse_dns.split('.')
> - revzone = DNSName(items[pos:])
> + revzone = revdns[pos:]
Hmm, and this logic will breaks CNAME/DNAME (RFC2317) handling ... Damn, we
need different handling when we intend to create the zone and when we want to
manipulate a record in a reverse zone. Grrr.
When we want to manipulate a record in existing zone, the whole branch does
not make sense and the result of DNS query is what we want and need.
On the other hand, we need this when creating *a new zone* from IP address ...
Mastin^2, what about zone names with missing period at the end? Is it handled
by dnszone_show() internally?
We have to discuss all this...
> try:
> api.Command['dnszone_show'](revzone)
> @@ -558,7 +568,10 @@ def get_reverse_zone(ipaddr, prefixlen=None):
>
> if revzone is None:
> raise errors.NotFound(
> - reason=_('DNS reverse zone for IP address %(addr)s not found') % dict(addr=ipaddr)
> + reason=_(
> + 'DNS reverse zone %(resolved_zone)s for IP address '
> + '%(addr)s is not manager by this server') % dict(
typo s/manager/managed/
> + addr=ipaddr, resolved_zone=resolved_zone)
> )
>
> revname = revdns.relativize(revzone)
--
Petr^2 Spacek
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