UDP between STM32-F4 Discovery boards


[The Backwoods Engineer] tested out a new accessory kit for the STM32-F4 Discovery board. The image above shows two boards communicating with the UDP protocol. Notice the extra PCB into which each Discovery board has been plugged. This is a third-party add-on which adds Ethernet, RS-232, SD card slot, and a connector for LCD or Camera. We’ve had one of these F4 Discovery boards on hand for a while and haven’t figured out a good way to connect external hardware to the huge dual pin-headers. This doesn’t solve the problem — the base board also includes dual headers to break-out all the pins — but having Ethernet, serial, and SD certainly reduces the need to add all that much more. The other drawback to the hardware is that the sample firmware is targeted at the IAR Embedded Workbench which is neither free, nor in the realm of affordable for hobbyists.

The NIC used on the baseboard has auto-crossover capabilities so the boards were connected using a regular Cat6 patch cable. This example has the boards constantly sending UDP packets with the module on the right reporting status information to a terminal via the serial connection.

Stepping beyond the Ethernet shield

We’ve said it time and again, the Arduino is a prototyping platform. In that spirit, [Doug Jackson] shows you how to conserve the expensive Arduino board and Ethernet shield by building your own Arduino Ethernet module. You may remember the ENC28j60 as a NIC for your microcontrollers. [Doug's] board makes use of that chip and adds an ATmega168 with a crystal, power regulator, breakout pins, and even a few DIP switches which can come in quite handy.

Black Hat 2008: NIC based rootkit

While Black Hat and Defcon have both concluded, we’re going to post a few more talks that we think deserve attention. [Sherri Sparks] and [Shawn Embleton] from Clear Hat presented Deeper Door, exploiting the NIC chipset. Windows machines use NDIS, the Network Driver Interface Specification, to communicate between the OS and the actual NIC. NDIS is an API that lets programmers talk to network hardware in a general fashion. Most firewalls and intrusion detection systems monitor packets at the NDIS level. The team took a novel approach to bypassing machine security by hooking directly to the network card, below the NDIS level.

The team targeted the Intel 8255x chipset because of its open documentation and availability of compatible cards like the Intel PRO/100B. They found that sending data was very easy: Write a UDP packet to a specific memory address, check to make sure the card is idle, and then tell it to send. The receive side was slightly more difficult, because you have to intercept all inbound traffic and filter out the replies you want from the legitimate packets. Even though they were writing low level chipset specific code, they said it was much easier to implement than writing an NDIS driver. While a certainly a clever way to implement a covert channel, it will only bypass an IDS or firewall on the same host and not one on the network.

[photo: Big Fat Rat]