Difference between revisions of "Ssh"

Latest revision as of 10:39, 3 December 2008

Ssh is the secure version of telnet, where communication is encrypted. It's usual to login through ssh via port 22. But often, administrators choose another less-conventional port in order to evade attacks and malicious attempts of intrusions.

Clients

A good choice for windows would be putty. For linux systems, simply use ssh from the command-line.

Usage

> ssh username:pass@hostname.com -p 22

Tunnelling

Creating a tunnel between a port in a localhost (localhost:24321) and another port in a remote host(hostname:123) is quite simple:

> ssh -L:24321:hostname:123 username@hostname -p 22

Tunelling the proxy.ist.utl.pt

A good thing to do is to use the ist proxy service to get access to registered online libraries.

Here you get instructions.

Basically, from outside the IST, you'll need to configure your proxy settings in your browser with

proxy.ist.utl.pt:3128

Then simply provide your fenix istxxxxxx login.

If you don't own a fenix login, then you must make a tunnel to some machine at ist intranet.

somemachine> ssh -L:5544:proxy.ist.utl.pt:3128 user@somemachine.ist.utl.pt -p 22

Then configure your browser proxy settings to:

somemachine.ist.utl.pt:5544

Just make sure that the 5544 port at somemachine.ist.utl.pt is open. Otherwise, find another port.

"Reverse" tunnelling

Similar, but this allows for the remote computer(B:2048) to connect to the local computer (A:22) without actually passing through the local computer firewall.

A> ssh -R:2048:localhost:22 B

To use the tunnel, connect from the B to A using:

B> ssh localhost -p 2048

External Links

• Putty
• Imap tunnel