Reverse engineering a simple C program part 1: Strings, ltrace, hexdump
Reverse engineering is something I find quite interesting, and a topic I am endeavoring to spend more time studying. There's nothing better than hands on practice, so lets take a look at a very simple 'license check' program written in C. Here's the code: This program will simply check for user input and then compare that input to a stored string. If the user input matches the string "ABCD-Z34K-42-OK" than the program will print "License confirmed" to the user. If the string does not match than the program will print "License incorrect" to the user. If no input is detected at all than the program simply prints "Usage: <key>" and exits. When this program is compiled none of the source code will be available. The process of compiling will result in the source code being translated (it can also be thought of as transforming) into the machine language that is read by computer hardware. Our challenge is to compile