Is simply SSH used over the top of Telnet, or can other protocols use SSH?

Hi Guys,

I know what SSH is: it provides secure connections over unsecure networks by using asymetric and symetric crypto algorithms, along with varius HMAC cryptos for each packet's Message Authentication Code (MAC).

However, what exactly can it be used for? When I search for 'SSH Server' on google, I get varius sites that offer Telnet/SSH server applications. This gives me the impression that SSH is simply an extra layer of security that is placed over the top of a Telnet Server to provide more security.

However, I also see varius other applications like ftp clients that say they support SSH access... but surely that means that the ftp server on the other end would have to run on a telnet framework!?! Or would there be a seperate SSH server installed on the host, and it would act as a proxy between the client and the server? If so, wouldn't the client need to login with a username and password?

I'm really confused as to which protocols SSH can / is supposed to be used with

If SSH can be used with any protocol, then what's the difference between SSH and SSL?

Simply, SSH is used by SSH. SSH connections do offer the ability to tunnel other ports like ftp, vnc, http, whatever over a SSH connection.

You should set up a SSH server and SSH client on your network and try it out. SSH is pretty much the only connection I use from remote locations. Most linux distros include a SSH server and client, and for windows you can use cygwin (complicated) or a free SSH server, and PuTTy for a windows ssh client.

Once you get a connection established you can use SSH like a VPN.

So SSH does have a telnet-like interface then? Otherwise you wouldn't be using PuTTy.

So would I be correct in saying the following...
Once the encrypted channel is established, the client is presented with an interface that is directly similar to a telnet session. From there they can carry out normal telnet operations like browsing folders and deleting files etc. (Do the xterm and WILL WONT commands work on an SSH client?)

If the above is correct, then how do you use SSH to connect to an FTP server? Once connected to the SSH server, does the client send the hostname and port of the server that they want to connect to? If so, what is the command syntax for this? Is it something like:
CONNECT HOSTNAME PORT <CRLF>

???

Thanks Doug, its getting clearer to me now. I'm only asking because I'm writing a telnet server at the moment and I'm going to integrate SSH access into it. I just want to know how the client uses the SSH server for other things other than the telnet-interface (like connecting to things like FTP servers etc).

When I get around to it I will install an SSH server / client, then I'll attack them with a Packet Sniffer - its always the best way to learn how a protocol works

EDIT:
Ignore my last paragraph - for some reason I forgot that SSH actually runs on encrypted channels

Only if you're using a SSH client program that is telnet-like. You don't have to use any client, you can simply open a SSH connection with a couple ports forwarded. Using the linux ssh client you could simply

ssh -L 21:localhost:21 -N myuser@mysshserver.local to simply open a connection with no user prompt that forwards tcp port 21 from the client computer and spits any port 21 traffic out on the ssh server as coming from localhost.

I'm having problems fully understanding what you meant in your last post.

Do you mean that if you typed ssh -L 21:localhost:21 -N myuser@mysshserver.local into a linux box, then the ssh client would start listening on port 21 on the local machine, and forward any connections to the ssh server, then from there the server would establish the connection with the remote host? If so, then how does the client manage to forward all outbound connections from the local machine through its tunnel? Surely it would need to bind itself to varius system processes like firewalls do?!?

Also, what is the command that the SSH client sends to the SSH server to tell it to open these connections? Is it like I said in my last post...
CONNECT HOSTNAME PORT <CRLF>

or is it something different?

The ssh server is the remote host in this example. If you want to run a ftp client on the ssh server that's a totally different scenario.

This is wandering off the subject of security, perhaps you should look around devshed.com, there is a lot more info about linux/ssh over there.