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Re: [opensuse-security] A curious firewall message I don't understand.



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The Thursday 2008-01-17 at 22:24 +0100, agr.suzdal wrote:

i think that something on your computer is going down.

first:
128.9.0.107 = ns1.isi.edu

Yes.


and it's a root name server of DNS as you can see at http://en.wikipedia.org/wiki/Root_nameserver

I guessed so, but didn't know how to make sure.


;  formerly NS1.ISI.EDU
; . 3600000 NS B.ROOT-SERVERS.NET.
B.ROOT-SERVERS.NET.      3600000      A     128.9.0.107

second:
icmp type 3 code 0 = Host Unreachable

Ah!


third:
as you can see at logs, your ROUTER (SRC=192.168.1.1) is sending a packet to you (DST=192.168.1.12)

Right, so far I knew :-)

answering "with" Host Unreachable (PROTO=ICMP TYPE=3 CODE=0)

And that I did not know.

that a packet DNS from YOU (SRC) [SRC=192.168.1.12 DST=128.9.0.107 LEN=62 TOS=0x00 PREC=0x00 TTL=64 ID=61490 DF PROTO=UDP SPT=2529 DPT=53 LEN=42 ] can't reach destination.

Ah... ok.

Then the funny thing is why is the firewall blocking that "answer" :-?

Perhaps I should open the firewall to port 53, which currently is not, as I don't serve dns queries :-? No... the packet itself is not going to port 53, it is icmp protocol.

Then why is it blocked?


my recomendation, verify your set of DNS at /etc/resolv.conf, and if it's right, then something is bad onto your computer.


I think there must be something fishy in the hints file, which is the one that suse supplies:

 nimrodel:/var/lib/named # rpm -q -f /var/lib/named/root.hint
 bind-9.4.1.P1-12


But the version is too old:

;       last update:    Jan 29, 2004
;       related version of root zone:   2004012900


Ok, I got the new version from ftp://ftp.internic.net/domain/named.root, and there is no server at "128.9.0.107" (not in the suse version, not in the new version):


; formerly NS1.ISI.EDU
;
.                        3600000      NS    B.ROOT-SERVERS.NET.
B.ROOT-SERVERS.NET.      3600000      A     192.228.79.201


But that's the same data the suse version contains. The only difference is:

nimrodel:/var/lib/named # diff root.hint /home/cer/named.root
12,13c12,13
< ;       last update:    Jan 29, 2004
< ;       related version of root zone:   2004012900
- ---
;       last update:    Nov 01, 2007
;       related version of root zone:   2007110100
74c74
< L.ROOT-SERVERS.NET.      3600000      A     198.32.64.12
- ---
L.ROOT-SERVERS.NET.      3600000      A     199.7.83.42



If there is no longer a root server at NS1.ISI.EDU, why is my machine querying it?




At least, replacing the old hints file solves a problem I saw in the logs:


Jan  9 04:21:39 nimrodel named[4688]: checkhints: L.ROOT-SERVERS.NET/A (199.7.83.42) missing from hints
Jan  9 04:21:39 nimrodel named[4688]: checkhints: L.ROOT-SERVERS.NET/A (198.32.64.12) extra record in hints




But yet, I nothing related to that 128.9.0.107. I'll grep for it... bingo! I had an old 'root.cache' with that entry, not belonging to any rpm.

You are right, my whole config is fishy; I think I have it right now.



- -- Cheers,
       Carlos E. R.

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