13,420
edits
Changes
no edit summary
# You will be working with the 2nd scenario of bypassing a firewall that blocks http traffic.
# In this investigation centos1 will be your http server and centos2 will be your client.
# On the HTTP server make sure the Apache web server is installed by typing the command:<br /><b><code><span style="color:#3366CC;font-size:1.2em;">rpm -q httpd</span></code></b>
# If it is installed check the configuration of the service to see if it is automatically started at any runlevels by using the <code>chkconfig h</code> command.
# If it has not been started automatically start the service using the '''service''' command.
# On '''centos2''' confirm that the httpd service is stopped so it cannot interfere with your observations.
# The next step is to establish a <u>tunnel</u>. When you establish a tunnel you make an ssh connection to a remote host and open a new port on the local host. That local host port is then connected to a port on the remote host through the established tunnel. When you send requests to the local port it is forwarded through the tunnel to the remote port.
# Establish a tunnel using a local port on centos2 of 20808, that connects to the remote port on '''centos1''' of 80, using the following command on '''centos2''':<br /><b><code><span style="color:#3366CC;font-size:1.2em;">ssh -L 20808:centos1:80 user@centos1</span></code></b><br><br> '''Note:'''<br>The '''-L''' option (which means Local port) takes one argument:<br><span style="courier"><local-port>:<connect-to-host>:<connect-to-port></span><br><br> The command basically connects your local port of 20808 to the remote port <br>of 80 on '''centos1'''. <br>This means all requests to 20808 on the <u>localhost</u> ('''centos2''') are actually tunnelled through your ssh connection to port 22 on '''centos1''' and then delivered to port 80 on '''centos1''', bypassing the firewall.<br><br>
# >Once the tunnel is established use '''netstat''' to verify the port 20808 is listening on '''centos2'''
# Now using the browser on '''centos2''' connect to http://localhost:20808