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 from remote.
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 Server
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 dbhost
# 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 following entry:
ORA1.world = (DESCRIPTION = (ADDRESS = (COMMUNITY =
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 18.104.22.168.0 - Production
With the Partitioning option
JServer Release 22.214.171.124.0 - 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.