Checklist

Checklist - Linux Privilege Escalation

Best tool to look for Linux local privilege escalation vectors: LinPEAS

System Information

• Get OS information

• Check the PATH, any writable folder?

• Check env variables, any sensitive detail?

• Search for kernel exploits using scripts (DirtyCow?)

• Check if the sudo version is vulnerable

• Dmesg signature verification failed

• More system enum (date, system stats, cpu info, printers)

• Enumerate more defenses

Drives

• List mounted drives

• Any unmounted drive?

• Any creds in fstab?

Installed Software

• Check for useful software installed

• Check for vulnerable software installed

Processes

• Is any unknown software running?

• Is any software running with more privileges than it should have?

• Search for exploits of running processes (especially the version running).

• Can you modify the binary of any running process?

• Monitor processes and check if any interesting process is running frequently.

• Can you read some interesting process memory (where passwords could be saved)?

Scheduled/Cron jobs?

• Is the PATH being modified by some cron and you can write in it?

• Any wildcard in a cron job?

• Some modifiable script is being executed or is inside modifiable folder?

• Have you detected that some script could be or are being executed very frequently? (every 1, 2 or 5 minutes)

Services

• Any writable .service file?

• Any writable binary executed by a service?

• Any writable folder in systemd PATH?

Timers

• Any writable timer?

Sockets

• Any writable .socket file?

• Can you communicate with any socket?

• HTTP sockets with interesting info?

D-Bus

• Can you communicate with any D-Bus?

Network

• Enumerate the network to know where you are

• Open ports you couldn't access before getting a shell inside the machine?

• Can you sniff traffic using tcpdump?

Users

• Generic users/groups enumeration

• Do you have a very big UID? Is the machine vulnerable?

• Can you escalate privileges thanks to a group you belong to?

• Clipboard data?

• Password Policy?

• Try to use every known password that you have discovered previously to login with each possible user. Try to login also without a password.

Writable PATH

• If you have write privileges over some folder in PATH you may be able to escalate privileges

SUDO and SUID commands

• Can you execute any command with sudo? Can you use it to READ, WRITE or EXECUTE anything as root? (GTFOBins)

• Is any exploitable SUID binary? (GTFOBins)

• Are sudo commands limited by path? can you bypass the restrictions?

• Sudo/SUID binary without path indicated?

• SUID binary specifying path? Bypass

• LD_PRELOAD vuln

• Lack of .so library in SUID binary from a writable folder?

• SUDO tokens available? Can you create a SUDO token?

• Can you read or modify sudoers files?

• Can you modify /etc/ld.so.conf.d/?

• OpenBSD DOAS command

• Find SUID Files

Capabilities

• Has any binary any unexpected capability?

ACLs

• Has any file any unexpected ACL?

Open Shell sessions

• screen

• tmux

SSH

• Debian OpenSSL Predictable PRNG - CVE-2008-0166

• SSH Interesting configuration values

Interesting Files

• Profile files - Read sensitive data? Write to privesc?

• passwd/shadow files - Read sensitive data? Write to privesc?

• Check commonly interesting folders for sensitive data

• Weird Location/Owned files, you may have access to or alter executable files

• Modified in last mins

• Sqlite DB files

• Hidden files

• Script/Binaries in PATH

• Web files (passwords?)

• Backups?

• Known files that contains passwords: Use Linpeas and LaZagne

• Generic search

Writable Files

• Modify python library to execute arbitrary commands?

• Can you modify log files? Logtotten exploit

• Can you modify /etc/sysconfig/network-scripts/? Centos/Redhat exploit

• Can you write in ini, int.d, systemd or rc.d files?

Other tricks

• Can you abuse NFS to escalate privileges?

• Do you need to escape from a restrictive shell?