ssh does not give option to trust on changed keys

[Nicolas Valcarcel]

When we reinstall a machine we used to enter via ssh, or change the ip of a hostname ssh doesn't allow us to log into the machine saying the key has change, then we need to edit the .ssh/known_hosts files by hand and remove the entry of this host. Ssh should warn the user that the host key has changed and give the option to allow the connection and automatically edit that file.

[Colin Watson (cjwatson)]

I suspect that this is at least in part deliberate, and I at least am absolutely not comfortable with changing this. Offering a simple option to ignore the error makes it seem safe to do so - even if you warn, people will still say "yeah, whatever, just let me in". In fact, unless you have good knowledge that the machine's circumstances have changed, ssh's prompt means that the target machine *may have been DNS-compromised* and it may be *dangerous* to just blaze on through regardless.

I realise that for people who reinstall machines frequently this is an inconvenience (although see the advice Darren gave you on the upstream bug report), but given the fairly well-understood effects of providing "ignore this security warning" buttons, I don't think that outweighs safety.

[Ralph Janke (txwikinger)]

From the upstream report:

1) you can save and restore the keys when you reinstall (useful
particularly if you have many clients).

2) See CheckHostIP in ssh_config(5) for the case where the address
changes.

3) you can use "ssh-keygen -R hostname" to delete an entry from
known_hosts rather than hand-editing.

[Ralph Janke (txwikinger)]

Does the explanations from the upstream report solve the issue?

If yes, I would like to close this report.

If no, please explain what other solution you would like to see.

Thanks

[Nicolas Valcarcel (nvalcarcel)]

Well, the bug should't be marked as incomplete, because it isn't it should be marked as Invalid.