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

Script crontab establish connection

Crontab entry

0 0 * * * /root/autossh.sh

File to connect with autossh, /root/autossh.sh

   1 killall autossh
   2 /usr/local/bin/autossh -i /root/.ssh/id_dsa -M 0 root@sshdServer -R 2222:192.168.1.1:22 -f -N
   3 /usr/local/bin/autossh -i /root/.ssh/id_dsa -M 0 root@sshdServer -R 139:192.168.1.2:139 -f -N