Remember to document RSA host key in any place...

[rsantos88]

Error connecting by ssh to a new ubuntu distribution (or a new installation)

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
94:43:6d:2b:78:54:06:7b:e5:02:61:01:d1:4a:35:51.
Please contact your system administrator.
Add correct host key in /home/teo/.ssh/known_hosts to get rid of this message.
Offending RSA key in /home/teo/.ssh/known_hosts:1
  remove with: ssh-keygen -f "/home/teo/.ssh/known_hosts" -R manipulation
RSA host key for manipulation has changed and you have requested strict checking.
Host key verification failed.
teo@oliver:~$ ssh manipulation 
teo@manipulation's password: 
Welcome to Ubuntu 14.04.5 LTS (GNU/Linux 4.4.0-31-generic i686)

 * Documentation:  https://help.ubuntu.com/
New release '16.04.3 LTS' available.
Run 'do-release-upgrade' to upgrade to it.


The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

Remember to document steps to configure the ssh server (in case it was necessary) :

1. sudo apt-get install openssh-server
2. edit /etc/ssh/ssh_host_rsa_key (with sudo)
3. change the old key for a new

[jgvictores]

ssh-keygen -f "/home/teo/.ssh/known_hosts" -R manipulation

[PeterBowman]

(Private ssh keys are meant to be... private.)

[AlvaroMartinezR]

@PeterBowman is right

[rsantos88]

😑 😑 😑 😑 😑 😑
sorry for the error... where do you want to keep the key..? maybe in some private place for us...?

[David-Estevez]

I guess the best thing to do is to create a new one (and keep it private) 😉

[jgvictores]

Obviously it's good to keep good security practices, but since we are in a LAN, I think we don't have to be extremely paranoid. Based on this, and to be practical, I think it's okay to not consider a man-in-the-middle attack and simply erase the RSA key associated to manipulation (via ssh-keygen -f "/home/teo/.ssh/known_hosts" -R manipulation) each time we boot it on a different distro.

Please correct me guys if I'm saying something terribly misguided.

[rsantos88]

@jgvictores I am totally agree with you. I tried to change the default password assigned in Ubuntu for the one I had already registered in Debian 6 to avoid possible future problems. I know that to reveal a password in a public place like this is a mistake, but I thought that we are connected in a local network, free of dangerous hackers trying to get into Teo (or maybe yes..) and I am always trying to document all the steps or changes that are performed with the intention that another person can configure it in the future.
Anyways, I hope you have fun with this 😅

[rsantos88]

It has generated a new RSA key (reinstalling openssh-server) and now the solution is erase the RSA key associated to manipulation (via ssh-keygen -f "/home/teo/.ssh/known_hosts" -R manipulation) each time we boot it on a different distro (and the same with locomotion).
For example, doing ssh with locomotion:

teo@oliver:~$ ssh-keygen -f "/home/teo/.ssh/known_hosts" -R locomotion
# Host locomotion found: line 4 type RSA
/home/teo/.ssh/known_hosts updated.
Original contents retained as /home/teo/.ssh/known_hosts.old
teo@oliver:~$ ssh locomotion
The authenticity of host 'locomotion (2.2.2.52)' can't be established.
ECDSA key fingerprint is ??:??:??:??:??:??:??:??:??:??:??:??:??:??:??:??.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'locomotion' (ECDSA) to the list of known hosts.
Warning: the ECDSA host key for 'locomotion' differs from the key for the IP address '2.2.2.52'
Offending key for IP in /home/teo/.ssh/known_hosts:4
Are you sure you want to continue connecting (yes/no)? yes
teo@locomotion's password: 
Welcome to Ubuntu 14.04.5 LTS (GNU/Linux 4.4.0-31-generic i686)

 * Documentation:  https://help.ubuntu.com/

The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

teo@locomotion:~$ 

So, I'll close this issue