PicoCTF Walkthru [47] - flag_shop (Integer Overflow tutorial)

[@nataliaburda9467]

Useful explanation, would love if you can provide some links for further research. How did you know that we are looking for a 32 bit number limit?

[@mike_on_tech]

So... probably not the most satisfying answer, but experience and prior learning. 32 bit is a common size (64 bit as well). I would recommend reading about how #s are represented in a computer (two's complement notation)
A first principles approach to this problem might look like this: What actions can I take and what effect they might have on the state of the system?
a. I definitely can't buy the flag I want (too expensive and I don't know any trickery to get around that IF).
b. Checking my balance doesn't cause any state change.
So I'm left with:
c. Buying the cheap flag. What are the bounds on the # of flags I can buy? Can't do

[@just_nothing-0101]

@@mike_on_tech best resource to read about those things plssss

[@alexandrubutunoi8803]

That was the most comprehensive explanation I could found. Thank you.

[@mike_on_tech]

Glad it was helpful!

[@ryansanderson7023]

Thanks man. I was getting frustrated when doing this because I didn't even know integer overflow was a thing! So I learned something new today.

[@mike_on_tech]

Glad it helped!

[@tonychzewanny4810]

The tutorial is really useful!! Especially I just start learning pentest/ctf from scratch, have no foundation about it.

[@mike_on_tech]

Glad you like it!

[@notmyname1486]

I solved this one by accident just playing around with larger numbers, your explanation helped me to understand what was going on! THANK YOU!!

[@mike_on_tech]

No worries, glad to help

[@euler7586]

Great explanation, sir!

[@weijietan1178]

i have learnt so much again thank to you sir!

[@adithibhat7277]

So super helpful. Thank you...

[@mike_on_tech]

Glad it was helpful!

[@goodboi3455]

I tried increasing my bank account so that I could buy a 1337 flag , but it didn't work. Why so?