Lab 2 - Defusing a binary bomb

You can check the final bomb stats to see how you and your classmates did.

Notes

• In order to read and copy the bomb in your individual bomb directory, you must have a CS Kerberos ticket. If you login to a fish machine you'll get this ticket automatically. If you want to copy your bomb while running on an Andrew machine, type "aklog cs.cmu.edu" to get your ticket, then do the copy. But be careful, rumor has it that the bombs explode immediately if they are not run on a fish machine.
• The jnl instruction is jump short if not less than. It is the same as jge.
• To single-step through you binary bomb in gdb, you will need to use the nexti and stepi commands (which step through binary instructions) rather than the next and step commands (which step through C instructions).
• Here is an updated version of the GDB CheatSheet (ps, pdf, txt) that includes the useful nexti command.
• Be extremely careful when working on your bomb. ANY explosion will cost you 1/4 point, even if you mistype a string by mistake or forget to set a breakpoint.
• Your bomb is only defused when all the inputs to the bomb are correct. So yes, you could use gdb to alter the contents of the registers and memory and then jump around the code to generate the phase defused messages. BUT you only get points for defusing a stage if the input you used is valid, so I wouldn't recommend doing this.