scp warning

scp has taken to producing messages of the form

Address ... maps to ..., but this does not map back to the address -
POSSIBLE BREAK-IN ATTEMPT!

How can I suppress such messages?

On Fri, 24 Jun 2011 18:07:22 +0000 (UTC)
Bob Tennent <(E-Mail Removed)> wrote:

> scp has taken to producing messages of the form
>
> Address ... maps to ..., but this does not map back to the address -
> POSSIBLE BREAK-IN ATTEMPT!
>
> How can I suppress such messages?

By fixing the DNS.

Basically if you log in from 1.2.3.4, ssh does a reverse DNS lookup to find
the PTR record (ie, the domain name) associated to that address, and then
it does another forward lookup of the A address for that name, and check
that it corresponds to the IP address you are logging from (ie, 1.2.3.4 in
this example). If you fix the DNS to have those lookups match, the warning
will go away.

Alternatively, you could set

UseDNS no

in the sshd configuration file.

On Fri, 24 Jun 2011 20:19:34 +0200, pk wrote:
> On Fri, 24 Jun 2011 18:07:22 +0000 (UTC)
> Bob Tennent <(E-Mail Removed)> wrote:
>
>> scp has taken to producing messages of the form
>>
>> Address ... maps to ..., but this does not map back to the address -
>> POSSIBLE BREAK-IN ATTEMPT!
>>
>> How can I suppress such messages?
>
> By fixing the DNS.
>
> Basically if you log in from 1.2.3.4, ssh does a reverse DNS lookup to find
> the PTR record (ie, the domain name) associated to that address, and then
> it does another forward lookup of the A address for that name, and check
> that it corresponds to the IP address you are logging from (ie, 1.2.3.4 in
> this example). If you fix the DNS to have those lookups match, the warning
> will go away.
>

The complaints are about the IP address and domain of the remote site
which obtains a IP address by DHCP to which dyndns.org allows me to
associate a domain.

> Alternatively, you could set
>
> UseDNS no
>
> in the sshd configuration file.

Doesn't work (and, yes, I have re-started sshd).

Bob T.

On Fri, 24 Jun 2011 19:17:11 +0000 (UTC), Bob Tennent wrote:

> > Alternatively, you could set
> >
> > UseDNS no
> >
> > in the sshd configuration file.
>
> Doesn't work (and, yes, I have re-started sshd).

What does work in sshd_config is

GSSAPIAuthentication no