SSH Tunnel

A secure shell (SSH) tunnel consists of an encrypted tunnel created through a SSH protocol connection. Users may set up SSH tunnels to transfer unencrypted traffic over a network through an encrypted channel.

autossh

Autossh is a program to start a copy of SSH and monitor it, restarting it as necessary should it die or stop passing traffic.

autossh -M 0 -L 8080:localhost:8080 example.com -g

Install:

• cd /tmp

• wget http://www.harding.motd.ca/autossh/autossh-1.4c.tgz

• tar xvzf autossh-1.4c.tgz
• cd autossh-1.4c
• ./configure
• make
• make install

Authentication with generated key pair:

• ssh_keygen -t dsa # with empty pass on machine running ssh client

• cat /root/.ssh/id_dsa.pub # paste it into the <destination user home folder>/.ssh/autorized_keys (running sshd server)

• autossh -i /root/.ssh/id_dsa -M 0 root@10.1.2.3 -R 1433:192.168.4.5:1433 -f -N # use generated key to authenticate on sshd server

Netbios SSH tunnel

Entities:

• SSH server: 10.1.1.123
• user on ssh server: root
• Netbios server (Samba): 192.168.3.4
• SSH client: 192.168.3.15
• Ports 139 and 445 on Netbios server
• Ports 139 and 445 must be free in the SSH server

The SSH server on the file /etc/ssh/ssh_config must have GatewayPorts yes.

The SSH client must be able to reach the SSH server and the netbios server.

On the ssh client, issue the following commands:

• ssh root@10.1.1.123 -R 139:192.168.3.4:139 sleep 99999

• ssh root@10.1.1.123 -R 445:192.168.3.4:445 sleep 99999

Now the Netbios server can be reached through ports 139 and 445 in the SSH server.

MS SQL Server tunnel

On the ssh client, issue the following commands:

• ssh root@10.1.1.123 -R 1433:192.168.3.113:1433 sleep 99999

Change passphrase with ssh-keygen

   1 $ cd ~/.ssh/
   2 #To change DSA passphrase, enter:
   3 $ ssh-keygen -f id_dsa -p
   4 #To change RSA passphrase, enter:
   5 $ ssh-keygen -f id_rsa -p