Describing Data Format Exploits Using Bitstream Segment Graphs

Exploits based on data processing bugs are delivered through crafted data that seems to follow a data format, yet is altered in some way to trigger a specific bug during processing, eg. in order to execute contained malicious code. Decomposing crafted data according to the purported data format and the function of its components that are not format-compliant is a step towards understanding the delivery mechanism of an exploit and fixing the vulnerable application. This paper demonstrates the use of bitstream segment graphs for describing the structure of exploits on the example of the TIFF Jailbreak exploit for the Apple iPhone and iPod Touch with firmware 1.1.1.