Transferring file to local machine when SSHing into a foreign box

[Gert Doering]

Hi,

On Sun, May 13, 2012 at 01:41:31PM +0300, Dotan Cohen wrote:
> I counter that the proposed cp2Local is no more of a security risk
> than scp because it _also_ requires the user of a username/password or
> keypair to explicitly express intent (establishing the initial SSH
> connection). Assuming the worst-case scenario that this feature is
> enabled and the user SSHes into a compromised box, the user will be
> only downloading unwanted, malicious files to his local machine, he
> will not be executing them automatically. This is no different than
> visiting a webpage. In fact, this is safer: web browsers _can_ run
> arbitrary code in the form of Javascript.

"unwanted, malicious files" could be .ssh/authorized_keys, .shosts, 
.profile / .bashrc, etc. - which might not be executed right away, but
will give the attacker interesting options to attack the original client 
machine.

[..]
> In short, I recognise the problem of allowing the remote machine
> access to write to your local machine. However, this has been a
> problem with many other technologies (www, email, ftp, etc.) and it is
> a solved issue in the general sense. That is, best practices and
> damage-mitigation strategies have already been established.

Actually, none of these technologies allow downloading arbitrary files
to the client machine, using server-controlled file names, just by
logging into a malicious server.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de