Black Flash

Walkthrough

Solution

The shop multiplies the requested quantity and the 65,536-credit price in a 32-bit unsigned integer. Ordering 65,536 tools satisfies the wholesale minimum, but the product is exactly 2^32 and wraps to zero. The zero total is below the 100-credit balance, so the approved-payment path prints the flag.

The reference solver only needs to submit 65536 at the quantity prompt.

Reference solver

The reference solver supplied with the writeup:

from pwn import *
p = process("./main")
p.sendlineafter(b"Quantity: ", b"65536")
print(p.recvall().decode())

Flag

SecurinetsENIT{bl4ck_fl4sh_s4l3_wr4pp3d_4r0und}