Hacking Linux Exposed: SSH Bouncing–How to Get Through Firewalls Easily

“Have you ever been in the situation that you wanted to SSH
directly to a machine, but there has been some device in between
that prevents it? Say you have a Linux firewall that protects your
DMZ, and you have a boatload of machines behind it that you want to
manage. There are all sorts of methods that are used to do so, and
all have some level of annoyance.

“The first and most simple solution is to SSH to the machine in
the way, say the firewall. The firewall administrator can just set
up one or more non-privileged accounts for users who need access to
the machines behind it. This is a pain, of course–if you want to
upload a file, you need to upload it to the firewall via sftp/scp,
and then upload it to the target server. What a pain. And
security-wise, you now have all these random firewall accounts
running amok, probably not your favourite situation…”


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