DNS resolution for some hosts fails, but nslookup works
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@gertjan said in DNS resolution for some hosts fails, but nslookup works:
You saw I did this :
set debugI just tried it. Didn't know about that but it was very helpful. When I use nslookup as is with the internal server 127.0.0.1, I get the following answer (shortened).
AUTHORITY RECORDS: -> testa-de.net origin = ns1-eu.123ns.eu mail addr = hostmaster.123ns.eu serial = 2022062251 refresh = 86400 retry = 7200 expire = 3600000 minimum = 86400 ttl = 3420 ADDITIONAL RECORDS: ------------ ** server can't find "the problematic host"When I specify to use the central firewall, it works as expected.
Obviously the host can't be resolved by this public DNS server but why does the pfSense query it? I can verify via packet capture that it indeed queries our central firewall and gets a response. But why does it try to get a authoritative answer?
I can't post the other response, because it only has non public information. However all sections that you might expect are there (Question, Answers, Authority Records and Additional Records for the Authority Records).
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@klinger I didn't reread this thread, but if you are trying to do this on pfSense itself, there is an option under Settings/General Setup:
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@klinger said in DNS resolution for some hosts fails, but nslookup works:
Only within this government mpls network.
Ok - if that is the case unbound would not resolve something that returns a rfc1918 address because of rebind protection. You would either need to turn that off completely, or set this domain as private, so that some A record that returns rfc1918 would be allowed
https://docs.netgate.com/pfsense/en/latest/services/dns/rebinding.html
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@steveits Thanks for the reply. Didn't solve the problem unfortunately.
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@klinger if some NS no matter where it is local, public internet or on some private mpls network tries to return a rfc1918 address for some record that would be a rebind.
And you need to tell unbound this domain that record is in is private and rfc1918 is ok, or you have to turn off rebind protection completely.
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@johnpoz That sounds quite logical. I've tried disabling Rebind Check under System -> Advanced and restarted the resolver service. Didn't help. I also tried adding the domain as private domain in the custom options. But that didn't help either. For good measure I also disabled DNSSEC.
I think this might be the cause but I guess it must be triggered by something else.
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@klinger what exactly are you trying to resolve? This record? testa-de.net
What NS are you pointing to for this domain, how does this NS know your coming from the mpls network.. Do you have a domain overide setup to resolve this domain?
This is the name servers I show for that domain.
;; QUESTION SECTION: ;testa-de.net. IN NS ;; ANSWER SECTION: testa-de.net. 86400 IN NS ns2-eu.123ns.de. testa-de.net. 86400 IN NS ns1-eu.123ns.eu. testa-de.net. 86400 IN NS ns4-eu.123ns.de. testa-de.net. 86400 IN NS ns3-eu.123ns.eu.But those are just public internet NS..
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@johnpoz I'm trying to resolve several host names in a subdomain of testa-de.net. The only NS that is configured is our central firewall. There is no domain override configured for that domain. As mentioned there are quite a bunch of domains in that mpls network.
Today I rebooted the firewall to test if disabling dns rebind check is affected by that. It didn't. I also tested this on a different pfSense firewall in "our" mpls network. Disabling dns rebind check worked on that one and I could resolve the host (it also uses the central firewall as NS).
I conclude therefore that on the firewall where this problem originated, that something is causing the dns rebind check option to not work as expected. -
@klinger said in DNS resolution for some hosts fails, but nslookup works:
The only NS that is configured is our central firewall.
This is another pfsense box or something else?
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@johnpoz Our central firewall is a Sophos SG.
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Today I tested several settings and found the solution. As mentioned in the previous post, the solution:
@johnpoz said in DNS resolution for some hosts fails, but nslookup works:
Ok - if that is the case unbound would not resolve something that returns a rfc1918 address because of rebind protection. You would either need to turn that off completely, or set this domain as private, so that some A record that returns rfc1918 would be allowed
https://docs.netgate.com/pfsense/en/latest/services/dns/rebinding.htmlis correct. It didn't work for me however because in my DNS Resolver config (Services -> DNS Resolver -> General Settings) the "DNS Query Forwarding" option was unchecked. After enabling that the solution worked. I can't tell if thats intended or not because it's not mentioned in the Docs. But at least it works for now.
I tested with disabling rebind check completely and also tested if only setting a specified domain as private. Both options worked when query forwarding was enabled.
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@klinger said in DNS resolution for some hosts fails, but nslookup works:
the "DNS Query Forwarding" option was unchecked
I really don't know how you expected to resolve some secret rfc1918 address that only resolves via mpls network if you were not forwarding to this specific NS that had those records.
I mean it would be possible to setup public dns and have some view, that only if you were hitting it from a specific IP(s) would you get the view that had the rfc1918 address in them.
Glad you got it sorted.
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@johnpoz said in DNS resolution for some hosts fails, but nslookup works:
possible to setup public dns and have some view, that only if you were hitting it from a specific IP(s) would you get the view that had the rfc1918 address
For sake of discussion we have private IPs set up under a subdomain in use on our data center. Virtuozzo needed the hostnames but we wanted to use private IPs for that layer. Maybe we could have set it all up on pfSense, but in normal DNS we can resolve them from our office too. Meh, multiple solutions. :)
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@johnpoz Well it worked before... But I kinda misunderstood the option. I could also confirm that without forwarding mode, the pfSense firewall queried our central firewall for name resolution (via packet capture). So either way the "correct" name server was queried.
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@klinger said in DNS resolution for some hosts fails, but nslookup works:
the pfSense firewall queried our central firewall for name resolution (via packet capture).
Well then you were forwarding - or that NS is authoritative for the domain you were looking up. Out of the box pfsense is a resolver, it talks to the roots down to talk to the actual NS for whatever domain your looking for.
So no out of the box pfsense would not query some NS on your network.. Unless the roots and the gltd servers pointed you to them..
Out of the box pfsense is a resolver..
Hey roots, what is the NS for .com
Hey gltd servers what is the NS for domain.com
Hey NS for domain.com what is the IP address of www.domain.com
you can see this with a simple dig and a +trace, this is how a resolver works.. So why would it ask some upstream NS in your network?
[23.01-RELEASE][admin@sg4860.local.lan]/root: dig www.netgate.com +trace ; <<>> DiG 9.18.8 <<>> www.netgate.com +trace ;; global options: +cmd . 21987 IN NS d.root-servers.net. . 21987 IN NS e.root-servers.net. . 21987 IN NS f.root-servers.net. . 21987 IN NS g.root-servers.net. . 21987 IN NS h.root-servers.net. . 21987 IN NS i.root-servers.net. . 21987 IN NS j.root-servers.net. . 21987 IN NS k.root-servers.net. . 21987 IN NS l.root-servers.net. . 21987 IN NS m.root-servers.net. . 21987 IN NS a.root-servers.net. . 21987 IN NS b.root-servers.net. . 21987 IN NS c.root-servers.net. . 21987 IN RRSIG NS 8 0 518400 20230322050000 20230309040000 951 . TN/9VuM2Q8uI9vNqRDfX/si09GNyq8dHFQdBJPG7CE935u/HbanonU99 Z/mZRM2xIt9zJd8kuvWDi9t0TTLYdFaoJ4XMcQyOQZeeZM/XfLUNBkX0 YdJqjDZD3joFSHNUpKHRF/aIZhoKwRxuAqQsiK04HXrKt3SyaGnVsUy5 kXQU05Z5HEgP8ZK3ziqLD+0bRX9uYAegL+JgEEDx421apR1xN4FY6ngF VONOKheKbl6LhSp91jfkR5LhiEyAT3PMXwfQEntHAmCyBgfw05rbSZB6 vALXQDZBcWCs/pW9VEpPx4J1DpGYhgKAa7ojk8ZDgnY3kfl/H6LplGFi qme5AQ== ;; Received 525 bytes from 127.0.0.1#53(127.0.0.1) in 0 ms com. 172800 IN NS a.gtld-servers.net. com. 172800 IN NS b.gtld-servers.net. com. 172800 IN NS c.gtld-servers.net. com. 172800 IN NS d.gtld-servers.net. com. 172800 IN NS e.gtld-servers.net. com. 172800 IN NS f.gtld-servers.net. com. 172800 IN NS g.gtld-servers.net. com. 172800 IN NS h.gtld-servers.net. com. 172800 IN NS i.gtld-servers.net. com. 172800 IN NS j.gtld-servers.net. com. 172800 IN NS k.gtld-servers.net. com. 172800 IN NS l.gtld-servers.net. com. 172800 IN NS m.gtld-servers.net. com. 86400 IN DS 30909 8 2 E2D3C916F6DEEAC73294E8268FB5885044A833FC5459588F4A9184CF C41A5766 com. 86400 IN RRSIG DS 8 1 86400 20230323050000 20230310040000 951 . ENL8WPFbxOqXipIZr0gi73LXISv1Oc5VREINA+nwZ4SdXg72++HZvKPt q7Rlv/Zy/z8U0xsV8drSfktoc3L/vOT97I/xvBiqGBKfmcI9fZ+OI+rp aql8fl7ep0KxSsCW2snOapFvf3LeDcPop5OJtCOv0h0g6CYnLugbWdRR qiF6FDg38bx/QwpQZL0BKxD3E6/qjFOrBPuTbHkWk5P+B5SdEF9cWcsK pVy+N3wxKCvKALzxQzQ/zPja/P+8plxGzOYeiaZCFDN4wxa6433zkluG lLSTABiU6mnsmOl+0mVQWzsF0s6QgLemrtyQlGT9HJw/kZhsX8N7WnlJ sPBQ6w== ;; Received 1175 bytes from 198.97.190.53#53(h.root-servers.net) in 33 ms netgate.com. 172800 IN NS ns1.netgate.com. netgate.com. 172800 IN NS ns2.netgate.com. CK0POJMG874LJREF7EFN8430QVIT8BSM.com. 86400 IN NSEC3 1 1 0 - CK0Q2D6NI4I7EQH8NA30NS61O48UL8G5 NS SOA RRSIG DNSKEY NSEC3PARAM CK0POJMG874LJREF7EFN8430QVIT8BSM.com. 86400 IN RRSIG NSEC3 8 2 86400 20230315042256 20230308041256 36739 com. VHsDr23lP03/xPxRbNUFC+UkSrUZ/Qr3JYHjhz7DYNOLPnzixRL+Hjv/ +kjbNiKVHYy2iGqU38XGJ4sPbvyRx8qygeTX3E7NnS4SdjnN2PKkTMAQ 42Vjxkq928qpoKPOwyn4zgcGSCZffTlNbY5IKVZacivEishoJ1j3BnVJ 1p2/N0gsLcS2GjIob2YGe7j4Lz8Aa5Rrj0s+DwlyP+BlCQ== 2U53SUOKS8OJJV178M90A8BMNI9USDVJ.com. 86400 IN NSEC3 1 1 0 - 2U54DC5VA9HQSV9DBV1IK3JD7KR4L61T NS DS RRSIG 2U53SUOKS8OJJV178M90A8BMNI9USDVJ.com. 86400 IN RRSIG NSEC3 8 2 86400 20230316045937 20230309044937 36739 com. JLAYnUTWdSkzhgKse8Qoyz0cdweJTibB9d0fQmTG1iDubISe0e/HhhBK SAdDEjqsOyV6x6bwtCVi+7HfoawJpsUgDNfYXEcgQfaXRk6TEOofhKnO mK+fVRHYsGbrBkyAfogu6KbQUAgleU65xfCmjKNaeYCDLe1Tq4FBcBLQ GstvOhDuAH5by0b1UBv+5k40jxuut/dlWfd+fxiwaxEO9A== ;; Received 717 bytes from 2001:502:1ca1::30#53(e.gtld-servers.net) in 36 ms www.netgate.com. 60 IN CNAME 1826203.group3.sites.hubspot.net. ;; Received 124 bytes from 208.123.73.90#53(ns2.netgate.com) in 37 ms [23.01-RELEASE][admin@sg4860.local.lan]/root:
