Re: [gentoo-user] Copying a file via ssh with no password, keeping the system safe

[Stroller]

On 7 Oct 2010, at 17:45, Momesso Andrea wrote:
> I need to set up a cron job to transfer a file every day from server A to server B.
>
> I'd like to do that via ssh and with no user assistance, completely automated.
>
> Setting up a public key, would do the job, but then, all the connections between the servers would be passwordless, so if server A gets compromised, also server B is screwed.
>
> Is there a way to allow only one single command from a single cronjob to operate passwordless, while keeping all the other connections secured by a password?

You could create a user on server B called backup, a user with very limited permissions and no shell (/bin/false). Thus server A can transfer files to serverb:~backup but if the key is compromised then little else can be done.

Not sure if the user could somehow be run in a chrooted ssh, for better security? I'm not sure what files a new user "backup" would have read-access to by default? If the key is obtained from server A then the attacker could copy files from server B (back to wherever they like), and it might be possible to obtain information about what services are run on that system or otherwise learn vulnerabilities from what could be read. 

Stroller.