GoodFUN: Integrating Hardware Protocol Scanning Support in GoodFET

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Presented at HITBMalaysia 2011 by

Don Bailey

The GoodFET, designed by Travis Goodspeed, is an open source JTAG adapter. Its primary job is to act as a programmer or debugger for embedded systems. It can also be used to attack embedded systems using several techniques, such as voltage glitching, to acquire application code from a secured chip. However, an attacker doesn’t always know which pins or test pads on a PCB correspond to JTAG and other protocols, such as USART or SPI. This is where GoodFUN comes in. GoodFUN is based on an Atmel microcontroller application designed by Don A. Bailey that scans a dynamically configurable set of pins for potential JTAG. The application is highly configurable. Additionally, GoodFUN is useful in detecting pins capable of other protocols, such as USART or SPI, that may negate the ability to automatically scan for JTAG. The GoodFUN presentation will describe the challenges faced in designing this application and the solutions. An Open Hardware implementation will be released so users can create their own GoodFET/GoodFUN solution without the typically requisite PCB. The GoodFUN source code will be released to the public to encourage other researchers and hobbyists to learn more about hardware hacking and security.