PicoCTF Challenge: GDB Baby Step2

Challenge Overview:

• The following was the description for the challenge:
  • This one is a bit tense.

Deep dive:

• Looks like, the behavior of the program is still kinda the same.

• But it has been modified a little.
  

• Starting GDB:
  • We see that, we still have a main function.
• Looking through the main function
  • There is something to point here, our main function has multiple eax registers.
  • So the logic of the program, seems to be doing some computation, hence from the description we are told to look at the contents of the register eax at the end.
  • This is where i want to explain the breakpoint, using the breakpoint, pauses the execution. Notice the change of the values:
  • This tells us that after some computation the register eax has been modified.
  • Again, using info register, already provides us with the decimal value. so we do not have to.