LOGIC

RANDOM

Predictable RNG

200

POINTS

DESCRIPTION

The program calls rand() without calling srand() first. In C, if srand() is never called, rand() uses the default seed of 1 - 100% predictable. Run the same rand() call locally in C (seed=1) to get the exact value the server will use. XOR it with 0xDEADBEEF to compute the required key, then provide it.

HOW TO CONNECT

SSH into the challenge server: Host: pwnable.kr Port: 2222 User: random Pass: guest Command: ssh [email protected] -p2222 Local solve script: #include <stdio.h> #include <stdlib.h> int main(){ unsigned int r = rand(); printf("%u\n", r ^ 0xDEADBEEF); return 0; } gcc solve.c -o solve && ./solve

ssh [email protected] -p2222

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