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Redirect incoming traffic to SSH, from a port of your choosing

Terminal - Redirect incoming traffic to SSH, from a port of your choosing
iptables -t nat -A PREROUTING -p tcp --dport [port of your choosing] -j REDIRECT --to-ports 22
2009-06-18 17:38:59
User: brizznown
Functions: iptables
9
Redirect incoming traffic to SSH, from a port of your choosing

Stuck behind a restrictive firewall at work, but really jonesing to putty home to your linux box for some colossal cave? Goodness knows I was...but the firewall at work blocked all outbound connections except for ports 80 and 443. (Those were wide open for outbound connections.) So now I putty over port 443 and have my linux box redirect it to port 22 (the SSH port) before it routes it internally. So, my specific command would be:

iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 22

Note that I use -A to append this command to the end of the chain. You could replace that with -I to insert it at the beginning (or at a specific rulenum).

My linux box is running slackware, with a kernel from circa 2001. Hopefully the mechanics of iptables haven't changed since then. The command is untested under any other distros or less outdated kernels.

Of course, the command should be easy enough to adapt to whatever service on your linux box you're trying to reach by changing the numbers (and possibly changing tcp to udp, or whatever). Between putty and psftp, however, I'm good to go for hours of time-killing.

Alternatives

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Terminal - Alternatives

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What others think

Or get ssh to listen to extra ports, like this:

Add this to /etc/ssh/sshd_config

Port 443
Comment by flatcap 274 weeks and 1 day ago

Hm...the would have been much easier!

Ah well...on the up-side, at least now I know a bit about using iptables.

Comment by brizznown 274 weeks and 1 day ago

You can have many ports listening for sshd.

Like so:

Port 22 Port 443
Comment by DaveQB 274 weeks and 1 day ago

Your point of view

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