CSAW CTF 2014 - Wieners
by @brad_anton (Foundstone)
-----------------------------------------

Key: key{http://imgur.com/XYlLNrk}


Files:
	CreateSketch - Python script to create the sketch directives 
		to make the shit blink
	CSAW-CTF14_-_Reversing.cpp.hex - assembled bytecode of the image
	CSAW-CTF14_-_Reversing.ino - Intial Sketch
	logicparser - python script to parse out the logic data. 


The contestants are given a dump from a Logic Analyzer. Which
can be viewed using Saleae's Logic Tool:
	
	https://www.saleae.com/downloads
	
Once opened the contestants need to figure out which channel actually
matters. Although channel 4 might contain the data they're looking for,
really channel 6 is where its at. 

Next contestants need to apply the Async Serial Analyzer to the channel, 
select autobaud, and have it decode the data as hex. 

From there contestants can export to CSV for more analysis.

Within the data is the firmware image that will be written to the device. The
students will have to figure that out, then extract the firmware. An example
script to demonstrate this is in "logicparser"

Next, with the image extracted, it needs to be put in a format that 
will be supported by a disassembler. logicparser does this already, converting
it to Intel Hex, however contestants may choose whatevez

Finally, with the assembly ready, they can start reversing. IDA
or ReAVR can be used:

http://www.avrfreaks.net/projects/reavr?module=Freaks%20Academy&func=viewItem&item_id=56&item_type=project

Eventually the contestant may realize that its just a series of repeated calls that raise
and lower a pin on the board. Each raise/lower is separated with a lower. with the disassembly
from ReAVR, the contestant can parse out just the useful bits with this horrific mess:

grep -v ":" a | awk '/lds r24,D0100/{getline; print}' | cut -d ',' -f 2 | cut -c 3 | awk ' NR % 2 == 1 { print }' | tr -d "\n"

And finally... they'll get a big long binary string of:

01011001010011110101010100100000010001000100100101000100001000000100100101010100001000010010000001010111011000010111100100100000011101000110111100100000011001110110111100100000011010110110100101101100011011000110000101101000001000010010000001101011011001010111100101111011011010000111010001110100011100000011101000101111001011110110100101101101011001110111010101110010001011100110001101101111011011010010111101011000010110010110110001001100010011100111001001101011011111011

which translates to the key:

YOU DID IT! Way to go killah! key{http://imgur.com/XYlLNrk}

which is a plate of wieners