Knowing How to Prevent and Fix Linux Privilege Escalation
To what extent is it possible to increase one’s privileges under Linux?
By assuming the identity of a different user, you can obtain access to increasingly restricted areas of a system, a practice known as “privilege escalation.” On Linux, for instance, any user can theoretically elevate their privileges to those of the root user. Using the su or sudo command makes this a legitimate option. Unauthorized access is possible, for instance when an attacker takes advantage of a security flaw. In order to properly protect our Linux systems, it is especially important to understand the third type of privilege escalations.
The best way to gain more authority.
Attackers sometimes use so-called exploits in an effort to elevate their privileges. Generally speaking, exploits are snippets of code designed to unleash a certain payload. The payload will exploit a hole in the system software or other components currently active on the system. Because of this, the program might crash or allow unintended access to memory. Forcibly elevating one’s privileges can be accomplished by erasing predetermined amounts of memory and replacing it with specially constructed (shell) code.
Typically, an attacker will do the following:
- Find a weak spot.
- Hack the associated vulnerability and create the exploit
- Run the exploit on a computer.
- Verify if the system has been effectively exploited.
- Acquire more rights
Is there a way to counteract the tendency for privilege to grow over time?
Linux privilege escalations are best combated by the tried-and-true “defense in depth” strategy. You employ a number of separate lines of defense, each aimed at protecting different parts of the building. It’s possible to keep your system secure even if a single line of defense is breached. That’s easier said than done, so let’s examine the steps that can be taken.
Limit the data that apps can accidentally share
These days, application banners are standard fare. A welcome message can provide information about the app, such as its name and version number. Although it may seem harmless, it’s best not to reveal any more than necessary. Version number leaks in particular need to be avoided.
WordPress security improvements that conceal the nginx version number and limit data leakage
To disable or limit access to compilers.
Most setups can function just fine without a compiler. Only in exceptional cases should a compiler be made available on production systems. Attackers frequently require the compiler in order to properly develop an exploit, therefore getting rid of it is a smart idea.
It’s time to update and patch your Linux installation.
Many security flaws in computer systems can be traced back to flawed pieces of computer code. There are several possible recommendations here. For starters, join relevant mailing lists to stay abreast of the latest security flaws. The following step is to routinely check for updates and install them so that your systems are always current. When possible, use an automated method to install security updates, such as unattended-upgrades for Debian and Ubuntu.
Start a file-monitoring program
Keeping a close eye on crucial system files is the best approach to discover a privilege escalation or breach. Having one of them shift without explanation could be a sign of a vulnerability. A file integrity monitoring (FIM) solution can be used for this kind of surveillance. Some of the most well-known programs include AIDE and the Linpeas Linux Audit Framework (auditd).
It’s time to audit the system.
Performing security audits on a constant basis is perhaps the best option. If you’re using Linux, you can scan for malware with rkhunter or ClamAV. To do a thorough system security check, use Lynis. Lynis is a defensive tool, but it can also uncover privilege escalation-related issues. Things like displaying software banners and writable cron jobs come to mind. That’s why Lynis is a staple in the toolkit of penetration testers. When auditing a system, it is possible to identify flaws that standard vulnerability scanners miss.
Limiters on the elevation of privileges
If you want to know if a privilege escalation is conceivable, there are certain tools that can help you. An understanding of how privileges are granted and revoked can be gained via this practice. They will also aid you in determining whether or not your Linux machines are susceptible to a specific privilege escalation and in taking appropriate action.
unix-privesc-check – Collect data and identify threats
LinEnum — Enumerate all available Linux privilege escalation mechanisms and exploit them
If you’re looking for a broader selection and more in-depth reviews of privilege escalation tools, Linux Security Expert is a great place to start.
Conclusion
One or more of Linux’s security layers may be compromised, allowing for the elevation of privileges. In order to launch an attack, an adversary must first do enumeration and then analyze the generated data. When new data becomes available, he or she will keep testing. This process will continue until one of the safeguards is compromised.
The first line of defense against these assaults is to implement effective security measures. If all safeguards are in place, including restricting the amount of information shared, installing patches, and keeping an eye on the systems, they become significantly more effective.
