21-04-2010

OLEGS FIRMWARE SSH SERVER GUIDE

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This is a step for step guide for enabling the dropbear SSH server in your ASUS WLxxxx linux-based wireless product. Following the guide will not change the default features of your device, it will just add some nice functionality to it. The guide is made using a ASUS WL-500G Deluxe (or WL-500GX as it is sometimes called). It should however apply to all the ASUS wireless line of products that are Linux based. Theese products are to my knowledge :
ASUS WL-500b ASUS WL-500bv2 ASUS WL-500g ASUS WL-500g Deluxe (WL500-gx) ASUS WL-HDD If you are the lucky ow ner of any of the above devices, you have come to the right place. If you still dont have one of the above devices - dont hesitate, go buy one :-) After follow ing the steps in this guide, your ASUS WL device w ill have all its normal functionality, and also have a ssh server running, that is accessiable from both WAN and LAN

Guide Index

1. Prerequisites - What is needed to get started. 2. Configuring the ssh server 3. Enabling at startup, and opening the firew all to accept incom m ing ssh connections

Prerequisites

All you need is :
One of the above Asus Wireless devices Firm w are version 1.9.2.7-4 by Oleg (and maby other versions, but tested on this one!) The firmw are IS needed. You w ill NOT get the steps below w orking if you use the stock firmw are. The firmw are on your device can be upgraded using the w ebinterface, please consult your users manual for details. Note that this guide does NOT require external storage, like a IDE or USB drive! If you dont already ow n one of the ASUS devices above, but consider buying one in order to take advantage of the server-possibilities, you should probably go for the WL-500gx or the WL-HDD. The WL-500gx has USB2.0 and the WL-HDD uses a normal IDE interface, w hile the other devices uses the slow USB 1.1 interface.
Configuring the ssh server
The ASUS WL-series routers are all running on a Broadcom BCM947XX Mipsel CPU and a customized linux. They all run a telnet server on the LAN side, allow ing the users to access the routers console, using a telnet client like Putty 1) Log on to your router using telnet. As mentioned, putty w ould be a good choice of client. If you havent changed it, the router address is 192.168.1.1 and username / passw ord is the same as you use for the w ebinterface. (In my screenshot I use 192.168.0.1, since this is my router address!)
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2) To enable to ssh server, all you need is to generate a couple of keypairs for the ssl encryption:
mkdir -p /usr/local/etc/dropbear < enter > dropbearkey -t dss -f /usr/local/etc/dropbear/dropbear_dss_host_key < enter > dropbearkey -t rsa -f /usr/local/etc/dropbear/dropbear_rsa_host_key < enter >
Enabling at startup, and opening the firewall to accept incomming ssh connections
The Firm w are version 1.9.2.7-4 by Oleg has a nice feature that it runs certain files at boot time, if they exist. Create theese files :
mkdir mkdir touch touch chmod /usr/local < enter > /usr/local/sbin < enter > /usr/local/sbin/post-boot < enter > /usr/local/sbin/post-firewall < enter > +x /usr/local/sbin/* < enter >
Create the correct lines in the post-boot file :
echo "#!/bin/sh" >> /usr/local/sbin/post-boot < enter > echo "dropbear" >> /usr/local/sbin/post-boot < enter >
Now you need to open your firew all, to accept WAN (Internet) connections to your ssh server. (This services is running on port 22)
echo echo echo echo > echo "#!/bin/sh" >> /usr/local/sbin/post-firewall < enter > "iptables -D INPUT -j DROP" >> /usr/local/sbin/post-firewall < enter > "iptables -A INPUT -p tcp --dport 22 -j ACCEPT" >> /usr/local/sbin/post-firewall < enter > "iptables -t nat -A PREROUTING -i $1 -p tcp --dport 22 -j DNAT --to-destination $4:22 " >> /usr/local/sbin/post-firewall < enter "iptables -A INPUT -j DROP" >> /usr/local/sbin/post-firewall < enter >
The above w ill open the firew all for ssh connections. Only thing now , is to save the changes w e made. Since /usr/local/sbin is in the internal flash memory of the ASUS Device, w e need to save it to flash and tell the router to use the files by enabling flashfs :
flashfs save < enter > flashfs commit < enter > flashfs enable < enter >

That is basically it, reboot your ASUS WL device, and enjoy your ssh server:-)

reboot < enter >

I hope you found this guide useful. Comments are w elcome to m acsat@m acsat.com If you feel like it, donations are more than w elcome as w ell :-) Close Print