Zsun SD111 Is Now “Officially” an Hackable Wireless Flash Drive

Zsun SD11x are Wi-Fi flash drives for 8 to 128 GB eMMC, alternative to Sandisk or Kingston. Yesterday, I soldered the UART pins to Zsun SD111 (8GB) flash drive to access the serial console, but I did not manage to enter the terminal as it was password-protected. I posted my results anyway, as I was convinced I would get some clever ideas from my readers, some of which appeared to be a little time consuming, but Zoobab offered a simple solution that consisted in changing the boot parameters, by replacing /sbin/init by /bin/sh.

The first step is to interrupt the boot by pressing space or another key, in order to access U-boot.
Now we can check the U-boot environment

ar7240> printenv
bootargs=console=ttyS0,115200 root=31:02 rootfstype=jffs2 rw init=/sbin/init mtdparts=ar7240-nor0:64k(u-boot),64k(u-boot-env),6720k(rootfs),1216k(uImage),64k(NVRAM),64k(ART)
bootcmd=bootm 0x9f6B0000
bootdelay=4
baudrate=115200
ethaddr=0x00:0xaa:0xbb:0xcc:0xdd:0xee
ipaddr=10.168.168.1
serverip=10.168.168.10
stdin=serial
stdout=serial
stderr=serial
ethact=eth0

Environment size: 361/65532 bytes

Let’s keep everything the same, except the init, which can be modified with the command below:

ar7240> setenv bootargs console=ttyS0,115200 root=31:02 rootfstype=jffs2 rw init=/sbin/sh mtdparts=ar7240-nor0:64k(u-boot),64k(u-boot-env),6720k(rootfs),1216k(uImage),64k(NVRAM),64k(ART)

Let’s start Linux:

It will end with:

Perfect! We’ve got access to the command line. Let’s have look at the users:

If we look at the shadow file only root and Admin have a password, so you could login with user ap71 without password for example, but that’s not too useful since you would not have root access. So I simply changed the root password with passwd command, but let’s me access the board via the UART console or telnet.

I’ve run some command to find out more about the system.

The linux kernel contains the string “LSDK-9.2.0” which appears to be an SDK for Atheros AR93XX, and can be downloaded here (I have not tried/verified the download). So the device is not running OpenWRT. Since telnet is not exactly secure, and want to access the device over the network, you should probably install dropbear, There’s only 796 KB left on the SPI flash, so what you can do is probably limited, although it might be possible to delete unused files to get extra space. Have fun!

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.

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