Re: how to get rid of sshd needing DNS ?
From: Thomas Wolf (tw_at_wsf.at)
Date: 04/27/04
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Date: Tue, 27 Apr 2004 22:36:12 +0200
Darren Tucker wrote:
> In article <c6j69g$npk$1@at-vie-newsmaster01.nextra.at>,
> Thomas Wolf <tw@wsf.at> wrote:
>>This one is driving me crazy.
>>I dont want my sshd to lookup the client's IP.
>>Turned off VerifyReverseMapping, running sshd with -n0,
>
> -u0 is what you probably want.
Yes. -n0 was a typo, I did use -u0.
>
>>not using all the items listed in the manpage that
>>could cause a lookup but no luck. Any hints ?
>>BTW, this is on FreeBSD 4.9-RELEASE-p4.
>
> I don't know which version is in FreeBSD, but recent OpenSSH's also have
> a UseDNS sshd_config option.
Thanks for the hint. I could solve my main problem (too long
delay when DNS is enabled but not responding) by using
OpenSSH_3.8p1 instead of the version included in the FreeBSD
base-system(SSH-1.99-OpenSSH_3.5p1 FreeBSD-20030924)
However I am still confused about the DNS-stuff in sshd.
According to the man pages, 'UseDNS' is the new name
for 'VerifyReverseMapping' in older versions. In 3.5p1, the
client IP was looked up before the login prompt was issued
(regardless the setting of 'VerifyReverseMapping'). In 3.8p1,
the behaviour is different, depending on UseDNS:
UseDNS yes: lookup occurs before and after the login
UseDNS no: lookup occurs after the login.
In any case, the login succeeds, I tried the following
cases:
1) IP lookup fails
2) IP lookup succeeds, reverse fails
3) IP lookup succeeds, reverse succeeds but returns a different IP
My understanding was that there should be no login at least in case 3
and I dont know what the lookup after the login is for. Are there any
documents explaining all this ?
Thomas
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