linux

650 Articles

Hacking A Brother Label Maker: Is Your CUPS Half Empty Or Half Full?

July 7, 2024 by 8 Comments

On the one hand, we were impressed that a tiny Brother label maker actually uses CUPS to support printing. Like [Sdomi], we were less than impressed at how old a copy it was using – – 1.6.1. Of course, [Sdomi] managed to gain access to the OS and set things up the right way, and we get an over-the-shoulder view.

It wasn’t just the old copy of CUPS, either. The setup page was very dated and while that’s just cosmetic, it still strikes a nerve. The Linux kernel in use was also super old. Luckily, the URLs looked like good candidates for command injection.

Continue reading “Hacking A Brother Label Maker: Is Your CUPS Half Empty Or Half Full?” →

Google Drive Now Bootable

July 2, 2024 by 22 Comments

USB drives are incredibly useful, both storing files for transport between different computers and for creating bootable drives that let us use or install other operating systems on our computers. While online file storage systems like Dropbox and Google Drive have taken over a large percentage of the former task from USB drives, they have not been able to act as bootable media, ensuring that each of us have a few jump drives lying around. That might not be the case anymore, though, as this guide is the first we know of to be able to use Google Drive to boot to a Linux system.

Unlike the tried-and-true jump drive methods, however, this process is not straightforward at all. It relies on two keys, the first of which is FUSE which allows a filesystem to be created in userspace. The second is exploiting a step in boot process of Linux systems where the kernel unpacks a temporary filesystem, called initramfs, in order to load the real filesystem. Normally a user doesn’t interact much with this step, but that doesn’t mean it’s impossible. A tool called dracut allows using an existing Linux installation to build a custom initramfs and in this case, the custom initramfs is built to include the proper support for both networking and FUSE.

The proof of concept in this demonstration originally ran in a container, using an existing project called google-drive-ocamlfuse to interact with Google Drive itself. From there, after sorting out some issues with root access, networking, malfunctioning symlinks, and various timeouts on the (perhaps predictably) slow system, the whole contraption was moved over to a laptop so it could be tested on real hardware. Everything runs, and although the original creator of this behemoth admits it is a bit “silly” they note that there may be some real-world use cases for something like this. We still won’t expect everyone to throw out their jump drives anytime soon, though. If you’re not feeling like your Linux skills are up to the challenge of something like this, we’d recommend you start with our own [Al Williams]’s Linux Fu series.

Linux Fu: Kernel Modules Have Privileges

June 19, 2024 by 13 Comments

I did something recently I haven’t done in a long time: I recompiled the Linux kernel. There was a time when this was a common occurrence. You might want a feature that the default kernel didn’t support, or you might have an odd piece of hardware. But these days, in almost all the cases where you need something like this, you’ll use loadable kernel modules (LKM) instead. These are modules that the kernel can load and unload at run time, which means you can add that new device or strange file system without having to rebuild or even restart the kernel.

Normally, when you write programs for Linux, they don’t have any special permissions. You typically can’t do direct port I/O, for example, or arbitrarily access memory. The kernel, however, including modules, has no such restriction. That can make debugging modules tricky because you can easily bring the system to its knees. If possible, you might think about developing on a virtual machine until you have what you want. That way, an errant module just brings down your virtual machine. Continue reading “Linux Fu: Kernel Modules Have Privileges” →

Lindroid Promises True Linux On Android

June 18, 2024 by 16 Comments

Since Android uses Linux, you’d think it would be easier to run Linux apps on your Android phone or tablet. There are some solutions out there, but the experience is usually less than stellar. A new player, Lindroid, claims to provide real Linux distributions with hardware-accelerated Wayland on phones. How capable is it? The suggested window manager is KDE’s KWIN. That software is fairly difficult to run on anything but a full-blown system with dbus, hardware accelerations, and similar features.

There are, however, a few problems. First, you need a rooted phone, which isn’t totally surprising. Second, there are no clear instructions yet about how to install the software. The bulk of the information available is on an X thread. You can go about 4 hours into the very long video below to see a slide presentation about Lindroid.

Continue reading “Lindroid Promises True Linux On Android” →

Raspberry Pi Saves Printer From Junk Pile

June 13, 2024 by 55 Comments

Around here, printers have a life expectancy of about two years if we are lucky. But [techtipsy] has a family member who has milked a long life from an old Canon PIXMA printer. That is, until Microsoft or Canon decided it was too old to print anymore. With Windows 10, it took some hacking to get it to work, but Windows 11 was the death knell. Well, it would have been if not for [techtipsy’s] ingenuity with a Raspberry Pi.

The Pi uses Linux, and, of course, Linux will happily continue to print without difficulty. If you are Linux savvy, you can probably see where this is going.

Continue reading “Raspberry Pi Saves Printer From Junk Pile” →

Linux Fu: The Root Cause

May 21, 2024 by 22 Comments

There was a time when real system administrators just logged into Unix systems as root. But as we all know — with great power comes great responsibility. It’s too easy to do terrible things when you are really just trying to do normal work, and, on top of that, malicious software or scripts can do naughty things without you noticing. So common practice quickly changed to where an administrator had a personal account but then had a way to run certain programs “as root” which means you had to deliberately decide to wield your power.

Before long, people realized you don’t even need a root login account. That way, an attacker can’t try to log into root at all. Sure, they could still compromise your account, but a random hacker knows you might have a root user, but it is harder to guess that your login ID is JTKirkJr or whatever.

There are other ways to control what users can do, but many Linux and Unix installations still use this model. The root can do everything but login, and specific users get the privilege to do certain things.

Continue reading “Linux Fu: The Root Cause” →