Security Hacks

1389 Articles

anfractuosity's test setup showing the Pi under test and a few pieces of equipment used to perform the attack

Cold Boot Attack You Can Do With A Pi

April 1, 2024 by 2 Comments

A cold boot attack is a way to extract RAM contents from a running system by power cycling it and reading out RAM immediately after loading your own OS. How easy is it for you to perform such an attack? As [anfractuosity] shows, you can perform a cold boot attack with a Raspberry Pi, with a reasonably simple hardware setup and a hefty chunk of bare-metal code.

[anfractuosity]’s setup is simple enough. The Pi 4 under attack is set up to boot from USB drive, and a relay board has it switch between two possible USB drives to boot from: one with a program that fills RAM with , and another with a program that extracts RAM out through UART. The process is controlled by another Pi controlling the relays through GPIOs, that also monitors the target Pi’s UART and uses it as a channel to extract memory.

The outcomes are pretty impressive. After 0.75s of power-down, most of the image could be extracted. That’s without any cooling, so abusing a can of electronics duster is likely to improve these results dramatically. Want to play with cold boot attacks? [anfractuosity]’s code is great for getting your feet wet. Furthermore, the code examples provided serve as a wonderful playground for general memory attack research.

Raspberry Pi not fun enough for you anymore? Well then, you can always start playing with Android phones!

Exploit The Stressed-out Package Maintainer, Exploit The Software Package

March 31, 2024 by 10 Comments

A recent security vulnerability — a potential ssh backdoor via the liblzma library in the xz package — is having a lot of analysis done on how the vulnerability was introduced, and [Rob Mensching] felt that it was important to highlight what he saw as step number zero of the whole process: exploit the fact that a stressed package maintainer has burned out. Apply pressure from multiple sources while the attacker is the only one stepping forward to help, then inherit the trust built up by the original maintainer. Sadly, [Rob] sees in these interactions a microcosm of what happens far too frequently in open source.

Maintaining open source projects can be a high stress activity. The pressure and expectations to continually provide timely interaction, support, and updates can easily end up being unhealthy. As [Rob] points out (and other developers have observed in different ways), this kind of behavior just seems more or less normal for some projects.

The xz/liblzma vulnerability itself is a developing story, read about it and find links to the relevant analyses in our earlier coverage here.

Security Alert: Potential SSH Backdoor Via Liblzma

March 29, 2024 by 34 Comments

In breaking news that dropped just after our weekly security column went live, a backdoor has been discovered in the xz package, that could potentially compromise SSH logins on Linux systems. The most detailed analysis so far seems to be by [Andres Freund] on the oss-security list.

The xz release tarballs from 5.6.0 in late February and 5.6.1 on March 9th both contain malicious code. A pair of compressed files in the repository contain the majority of the malicious patch, disguised as test files. In practice, this means that looking at the repository doesn’t reveal anything amiss, but downloading the release tarballs gives you the compromised code.

This was discovered because SSH logins on a Debian sid were taking longer, with more CPU cycles than expected. And interestingly, Valgrind was throwing unexpected errors when running on the liblzma library. That last bit was first discovered on February 24th, immediately after the 5.6.0 release. The xz-utils package failed its tests on Gentoo builds.

Continue reading “Security Alert: Potential SSH Backdoor Via Liblzma” →

This Week In Security: Peering Through The Wall, Apple’s GoFetch, And SHA-256

March 29, 2024 by 1 Comment

The Linux command wall is a hold-over from the way Unix machines used to be used. It’s an abbreviation of Write to ALL, and it was first included in AT&T Unix, way back in 1975. wall is a tool that a sysadmin can use to send a message to the terminal session of all logged-in users. So far nothing too exciting from a security perspective. Where things get a bit more interesting is the consideration of ANSI escape codes. Those are the control codes that moves the cursor around on the screen, also inherited from the olden days of terminals.

The modern wall binary is actually part of util-linux, rather than being a continuation of the old Unix codebase. On many systems, wall runs as a setgid, so the behavior of the system binary really matters. It’s accepted that wall shouldn’t be able to send control codes, and when processing a message specified via standard input, those control codes get rejected by the fputs_careful() function. But when a message is passed in on the command line, as an argument, that function call is skipped.

This allows any user that can send wall messages to also send ANSI control codes. Is that really a security problem? There are two scenarios where it could be. The first is that some terminals support writing to the system clipboard via command codes. The other, more creative issue, is that the output from running a binary could be overwritten with arbitrary text. Text like:
Sorry, try again.
[sudo] password for jbennett:

You may have questions. Like, how would an attacker know when such a command would be appropriate? And how would this attacker capture a password that has been entered this way? The simple answer is by watching the list of running processes and system log. Many systems have a command-not-found function, which will print the failing command to the system log. If that failing command is actually a password, then it’s right there for the taking. Now, you may think this is a very narrow attack surface that’s not going to be terribly useful in real-world usage. And that’s probably pretty accurate. It is a really fascinating idea to think through, and definitively worth getting fixed. Continue reading “This Week In Security: Peering Through The Wall, Apple’s GoFetch, And SHA-256” →

User Beware: The Fine Line Between Content And Code

March 25, 2024 by 29 Comments

Everyone loves themes. Doesn’t matter if it’s a text editor or a smart display in the kitchen, we want to be able to easily customize its look and feel to our liking. When setting up a new device or piece of software, playing around with the available themes may be one of the first things you do without giving it much thought. After all, it’s not like picking the wrong one is going to do something crazy like silently delete all the files on your computer, right?

Unfortunately, that’s exactly what happened a few days ago to [JeansenVaars] while trying out a Plasma Global Theme from the KDE Store. According to their Reddit post, shortly after installing the “Gray Layout” theme for the popular Linux graphical environment, the system started behaving oddly and then prompted for a root password. Realizing something didn’t seem right they declined, but at that point, it was already too late for all of the personal files in their home directory.

Continue reading “User Beware: The Fine Line Between Content And Code” →

This Week In Security: Loop DOS, Flipper Responds, And More!

March 22, 2024 by 8 Comments

Here’s a fun thought experiment. UDP packets can be sent with an arbitrary source IP and port, so you can send a packet to one server, and could aim the response at another server. What happens if that response triggers another response? What if you could craft a packet that continues that cycle endlessly? That is essentially the idea behind Loop DoS (Denial of Service).

This unique avalanche of packets has been managed using specific implementations of several different network services, like TFTP, DNS, and NTP. There are several CVEs being used to track the issue, but CVE-2024-2169 is particularly odd, with the description that “Implementations of UDP application protocol are vulnerable to network loops.” This seems to be a blanket CVE for UDP, which is particularly inappropriate given that the first DoS of this sort was first reported in 2009 at the latest.

More details are available in a Google Doc. There some interesting tidbits there, like the existence of cross-protocol loops, and several legacy protocols that are vulnerable by design. The important thing to remember here is you have to have an accessible UDP port for this sort of attack to take place, so if you’re not using it, firewall it.

Flipper Flips Back

We’ve covered the saga of the Flipper Zero vs the Canadian government, in the context of car theft. The short version is that Canada has seen an uptick of car thefts from organized crime. Rather than meaningfully dealing with this problem, the Canadian government went looking for scapegoats, and found the Flipper Zero.

Well now, Flipper has responded, and put simply, the message is “stop the madness”. There has never been a confirmed case of using a flipper to steal a car, and it’s very unlikely it’s ever happened. On a modern car with proper rolling-code security, it’s not meaningfully possible to use the Flipper Zero for the theft. The two primary ways criminals actually steal cars are with dedicated keyfob repeaters and CAN bus hackers.

There is a petition to sign, and for Canadians, Flipper suggests contacting your local member of parliament. Continue reading “This Week In Security: Loop DOS, Flipper Responds, And More!” →

Photoresistors Provide Air Gap Data Transfer, Slowly

March 19, 2024 by 50 Comments

One of the simplest ways of keeping a computer system secure is by using an air gap — that is, never actually connecting the system to the network. This can often include other peripherals like USB drives and other removable storage as well, so getting information to and from secure (or compromised) systems behind air gaps can often present a challenge. But assuming you have local access to the computer and your parts bin handy, these optical solutions from [Nikolay] can allow  data transfer to or from such off-line computers.

[Nikolay]’s specific use case for this project is to transfer small amounts of information to or from computers that may be compromised in some way, or computers that might otherwise be dangerous to connect to other equipment. There’s actually several methods described in the project, the first involves temporarily attaching a photoresistor to the computer’s screen which has been wired into the remains of a USB keyboard. A script running on the compromised machine translates data into a series of white and black squares. The sensors can detect these patterns much like playing Duck Hunt on an old CRT television and transmit the data across the air gap with reasonable certainty nothing harmful crossed with it.

Continue reading “Photoresistors Provide Air Gap Data Transfer, Slowly” →