Ssh – How to use compression option for ssh with the ProxyCommand

sshssh-tunnel

I want to establish a ssh tunnel for transferring data from my computer to a remote machine through a gateway machine.

I want to copy large amount of data, thus I use blowfish for encryption and enable the compression.

Which of the following commands is correctly setup the encryption and compression:

Define the compression and encryption within ProxyCommand:

ssh -L 5555:127.0.0.1:555 -o ProxyCommand="ssh -c blowfish -C user@gateway nc -q0 target 2222" user2@target -v
Define the compression and encryption within the main ssh command:

ssh -L 5555:127.0.0.1:555 -c blowfish -o ProxyCommand="ssh user@gateway nc -q0 target 2222" -C user2@target -v
Define the compression and encryption both in the ProxyCommand and ssh command:

ssh -L 5555:127.0.0.1:555 -c blowfish -o ProxyCommand="ssh -c blowfish -C user@gateway nc -q0 target 2222" -C user2@target -v

The debug message (-v) informs me that the compression is enabled.

Does the option 3 make ssh to compress the data two times?

Best Answer

Command 1 will compress data between the client and gateway, but not between the gateway and target. Option 2 will compress data between the client and target (at the expense of not compressing some protocol level data, which won't be significant). Option 3 will compress data between the client and target, and double compress data between the client and gateway (which you definitely don't want).

If the bandwidth between the gateway and target is high (e.g. LAN speed) then go with option 1. If not, go with option 2.

Related Solutions

Ssh – Why does logging out of an SSH session hang when using port-forwarding

As you expected, this happens because SSH won't exit if there are outstanding connections going through the tunnel.

If you exit your browser (and all other programs that are going through the port 9000 tunnel) then SSH should exit.

The ssh man page says:

 The session terminates when the command or shell on the remote machine exits and all X11 and TCP connections have been closed.

And I don't see any options to change that behavior, so I suspect there's nothing you can do.

Ssh – How to automate SSH login with password

Don't use a password. Generate a passphrase-less SSH key and push it to your VM.

If you already have an SSH key, you can skip this step… Just hit Enter for the key and both passphrases:

$ ssh-keygen -t rsa -b 2048
Generating public/private rsa key pair.
Enter file in which to save the key (/home/username/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/username/.ssh/id_rsa.
Your public key has been saved in /home/username/.ssh/id_rsa.pub.

Copy your keys to the target server:

$ ssh-copy-id id@server
id@server's password:

Now try logging into the machine, with ssh 'id@server', and check-in:

.ssh/authorized_keys

Note: If you don't have .ssh dir and authorized_keys file, you need to create it first

to make sure we haven’t added extra keys that you weren’t expecting.

Finally, check to log in…

$ ssh id@server

id@server:~$

You may also want to look into using ssh-agent if you want to try keeping your keys protected with a passphrase.

Best Answer

Related Solutions

Ssh – Why does logging out of an SSH session hang when using port-forwarding

Ssh – How to automate SSH login with password

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