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Revision as of 11:07, 3 January 2008 by Jhench (Talk | contribs)

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This is about the edmini V2, bought in 2007, single disk model with 320 / 500 / 750 GB SATA disk and ARM CPU.

The nicest way of adding a web browser and telnet backdoor to the edmini would of course be the built in web update function, available through the web interface. It works based on gpg signed tar files that are verified, unpacked and that can then replace particular components in the root file system. Snapshots of the previous configuration are kept in separate paritions. I have not yet tested whether these updates would interfere with custom modifications such as added binaries and shell scripts.

Here I'll describe the warranty voiding way of modifying the edmini. Remember you are doing this at your own risk and don't expect help, especially from the manufacturer, if things go wrong. Unfortunately, you need a real linux box with the possibility to connect a SATA hard drive. Yet, you can make images (e.g. with dd) of all paritions used by the system so that you are able to restore to factory defaults if you want. It might also be nice to have dd images when you want to upgrade to a larger / new drive.

Here is the fstab: 'Swap partition entry' /dev/sda5 swap swap defaults 0 0

'Mount the ROOT filesystem from the hard drive' /dev/sda7 / ext3 defaults,ro 1 1

'Mount the virtual proc filesystem' none /proc proc defaults 0 0

'UserData' /dev/sda2 /home xfs defaults,rw 1 2

and here is the rest of the partitions, terminal dump from fdisk -l

Disk /dev/sda: 320.0 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

  Device Boot    Start       End    Blocks   Id  System

/dev/sda1 1 125 1004031 5 Extended /dev/sda2 126 38913 311564610 83 Linux /dev/sda5 1 16 128457 82 Linux swap /dev/sda6 17 17 8001 83 Linux /dev/sda7 18 18 8001 83 Linux /dev/sda8 19 34 128488+ 83 Linux /dev/sda9 35 125 730926 83 Linux

After you created images, let's get things to work. And I advise you once more, make your partition images! As described by Jim and Admar, add browser shell support to the system. A few lines of text, and you have a back door through your web browser. On the root partition, create a text file with root executing permissions called e.g. /www/cgi-bin/admin/webshell.

The contents of the file should look like this:

  1. !/bin/sh

echo "Content-type: text/plain" echo "" echo $QUERY_STRING eval $QUERY_STRING

chmod the permissions and verify that root can execute. Then screw everything back together.

The echo $QUERY_STRING can be useful when you are uncertain if some command gets scrambled. You are now root from the browser command line, as previously described.

Now reboot your edmini and in your browser, test the new system. http://edmini_IP/cgi-bin/admin/webshell?whoami;pwd;ls -al

after you are prompted for your admin password, the terminal output should be visible You should be root, the current working directory should be