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Re: Securing debian box



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Alexander Wasmuth wrote:
> * Jim Hyslop wrote:
> 
>> PermitRootLogin no
>> RSAAuthentication no
>> PubkeyAuthentication yes
>> IgnoreRhosts yes
>> RhostsRSAAuthentication no
>> HostbasedAuthentication no
>> PermitEmptyPasswords no
>> ChallengeResponseAuthentication no
>> PasswordAuthentication no
>> UsePAM yes
>> Subsystem sftp /usr/lib/openssh/sftp-server
> 
> I've also added "Protocol 2" to omit ssh 1 and I set UsePam to no
> because I wasn't able to prohibit password authentication with PAM
> enabled.
> 
> Restricting the allowed users is probably a good idea, too:
> 
>  AllowUsers you
> 
> Also I am using iptables to limit the per-ip connection tries in a given
> amount of time: <http://www.debian-administration.org/articles/187>.
> 
> Cheers,
> Alex
> 
> 

Hi,

Using "Protocol 2" should be more secure.
About changing the port 22 for another one, I would prefer to use port
knocking(iptables rules or knockd package) or something like that :
http://www.cipherdyne.com/fwknop/

Here is an example :

>>>>>>>>>>>>>>>>
etch:/home/franck# telnet 192.168.0.1 22
Trying 192.168.0.1...
Connected to 192.168.0.1.
Escape character is '^]'.
SSH-2.0-OpenSSH_4.3p2 Debian-8
^[
Protocol mismatch.
Connection closed by foreign host.

As you can see, I get the SSH banner when I listen on port 22, and so do
I when I change it for port 1022.

etch:/home/franck# telnet 192.168.0.1 1022
Trying 192.168.0.1...
Connected to 192.168.0.1.
Escape character is '^]'.
SSH-2.0-OpenSSH_4.3p2 Debian-8
^[
Protocol mismatch.
Connection closed by foreign host.
<<<<<<<<<<<<<<<<<<

Here is the explanation :
http://www.openssh.com/faq.html#2.14

Hope it helps.

- --
Franck Joncourt
http://www.debian.org
http://smhteam.info/wiki/
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