Problem - Kevin Tafuro

int main(int argc, char *argv[ ]) {
void (*ptr)(void);
ptr = GET_FN_PTR(my_func); /* get the real address of the function */
(*ptr)( ); /* make the function call */
return 0;
}
12.10 Restructuring Arrays
Problem
Arrays contain information in their structure. Knowing how many dimensions an
array has can help in understanding the underlying data. You need a way to hide
dimensional information about arrays.
Solution
Disguising the nature of arrays is different from obfuscating a variable. What is
important in this case is the order of elements in the array, not the elements themselves.
Array elements can be obfuscated using any standard variable obfuscation,
but arrays themselves should be restructured as well.
Arrays can be restructured in four ways:
• Splitting a one-dimensional array into multiple one-dimension arrays
• Folding a one-dimensional array into a multidimensional array
• Flattening a multidimensional array into a one-dimensional array
• Merging two one-dimensional arrays into a single one-dimensional array
In this recipe, an API will be developed for splitting, folding, flattening, and merging
arrays.
Discussion
Array obfuscation is a powerful way of disguising groupings of information
by adding or subtracting dimensions from an array. Note that
the array data is not obfuscated, merely the ordering of the data. This
is insignificant with one-dimensional arrays but can be very effective
with large multidimensional arrays.
The first step in developing the API for restructuring arrays is to define a new data
type that will represent an array, rather than using the normal C convention for
672 | Chapter 12: Anti-Tampering
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