Security in one of the most important demands in today's Internet
environment. One common approach to secure the personal or IT infrastructure is to use a
two wall barrier or firewall. The first wall protects the DMZ (Demilitarized Zone) from the
Internet, the second wall protects the HSZ (High Security Zone) from the DMZ and Internet.
A tighten security environment often results in a more complicated working area, where some
services like FTP or TELNET cannot be used anymore. SSH offers some possibilities to
facilitate the daily working, in this Tip we want to show how to access an Oracle Database
behind a two barrier firewall where only Port 22 for SSH is opened for authenticated access
Port 22 must be opened on external Firewall
Port 22 must be opened on internal Firewall
You can login to the SSH Server and the internal DB
1. Create the "external" SSH Tunnel from the localhost to
the SSH Server
2. Create the "internal" SSH Tunnel from the SSH Server to the DB Server
3. Connect your Client (e.g. SQLPLUS) to the DB-Server
Login to the SSH Server using MindTerm,
TeraTerm or any SSH Client with your personal Account, you will reach the Shell
Prompt of this machine.
Create an SSH Tunnel from Port 1521 on localhost to an
unprivileged Port 5429 on the SSH Server. This can be accomplished within the SSH
Client (Tunnels, Basic).
####### Settings for Host
# Specifies whether remote hosts are allowed
# to connect to local forwarded ports. The argument
# must be "yes" or "no". The default # is "no".
Login to the DB Server SSH Server using your current
Terminal Emulation with the following Command which opens the "internal" SSH
Tunnel from the unprivileged Port 5429 on the SSH Server to Port 1521 on the DB Server.
Usually Port 1521 is used for Oracle Net8 Connections, if you are not sure, ask your DB
Administrator for this Port.
$ ssh -L 5429:dbhost:1521 dbhost
Both Tunnels are now connected and ready to use
$ ssh dbhost
# Specifies that a TCP/IP port on the local machine
# be forwarded over the secure channel to given host:port
# from the remote machine. The first argument must be a
# port number, and the second must be host:port. Multiple
# forwardings may be specified, and additional forwardings
# can be given on the command line. Only the superuser can
# forward privileged ports.
LocalForward 5429 dbhost:1521
You have to setup your local TNSNAMES.ORA File for SQLPLUS with the
ORA1.world = (DESCRIPTION = (ADDRESS
= (COMMUNITY = tcp.world)
(PROTOCOL = TCP)
(Host = localhost) (Port = 1521))
(SID = ORA1) (GLOBAL_NAME = ORA1.world)
Test the connection with TNSPING and connect to the DB Server
ARKUM:zahn> tnsping ORA1
Attempting to contact (ADDRESS=(COMMUNITY=tcp.world)
(PROTOCOL=TCP)(Host=localhost)(Port=1523)) OK (310 msec)
ARKUM:zahn> sqlplus scott/tiger@ORA1
Oracle8i Enterprise Edition Release 126.96.36.199.0 - Production
With the Partitioning option
JServer Release 188.8.131.52.0 - Production
This example shows how to connect two SSH Tunnels, but you can connect
any number of SSH Tunnels, the only requirement is, that you can logon to all intermediated
and final servers over a secure connection like SSH.