seccon22-noiseccon

Seccon 2022 Qualifier Challenge 'Noiseccon'
git clone https://git.sinitax.com/sinitax/seccon22-noiseccon
Log | Files | Refs | sfeed.txt

solve.py (1074B)

      1from pwn import *
      2from base64 import b64decode
      3import subprocess
      4
      5def extract_char(index):
      6    io = remote("localhost", 1337)
      7
      8    scalex = 1 << (64 + index * 8)
      9    scaley = "9" * 100
     10
     11    io.readuntil(b"Flag length: ")
     12    flaglen = int(io.readline())
     13
     14    io.readuntil(b"Image width: ")
     15    width = int(io.readline())
     16
     17    io.readuntil(b"Image height: ")
     18    height = int(io.readline())
     19
     20    print(flaglen, width, height)
     21
     22    io.readuntil(b"Scale x: ")
     23    io.sendline(str(scalex).encode())
     24
     25    io.readuntil(b"Scale y: ")
     26    io.sendline(str(scaley).encode())
     27
     28    data = b64decode(io.readline().strip())
     29    with open("tmp.webp", "wb+") as f:
     30        f.write(data)
     31    io.close()
     32
     33    output = subprocess.check_output(["node", "findoff.js"])
     34    indexlines = [l for l in output.split(b"\n") if l.startswith(b"IDX ")]
     35    indexes = set([int(l.split()[1]) for l in indexlines])
     36    print(len(indexes), indexes)
     37
     38    return chr(list(indexes)[0])
     39
     40flag = ""
     41for i in range(40):
     42    if flag.startswith("SECCON"):
     43        break
     44    flag = extract_char(i) + flag
     45print(flag)