Author: Jonathan Bennett

539 Articles

Meshtastic And Owntracks To Kick Your Google Habit

October 11, 2023 by 20 Comments

I have an admission to make. I have a Google addiction. Not the normal addiction — I have a problem with Google Maps, and the timeline feature. I know, I’m giving my location data to Google, who does who-knows-what-all with it. But it’s convenient to have an easy way to share location with my wife, and very useful to track my business related travel for each month. What we could really use is a self-hosted, open source system to track locations and display location history. And for bonus points, let’s include some extra features, like the ability to track vehicles, kids, and pets that aren’t carrying a dedicated Internet connection.

You can read the title — you know where we’re going with this. We’re setting up an Owntracks service, and then tying it to Meshtastic for off-Internet usability. The backbone that makes this work is MQTT, a network message bus that has really found its niche in the Home Assistant project among others. It’s a simple protocol, where clients send brief messages labeled by topic, and can also subscribe to specific topics. For this little endeavor we’ll use the Mosquito MQTT broker.

One of the nice things about MQTT is that the messages are all text strings, and often take the form of JSON. When trying to get two applications to talking using a shared MQTT server, there may need to be a bit of translation. One application may label a field latitude, and the other shortens it to lat. The glue code to put these together is often known as an MQTT translator, or sometimes an MQTT bridge. This is a program that listens to a given topic, ingests each message, and sends it back to the MQTT server in a different format and topic name.

The last piece is Owntracks, which has a recorder project, which pulls locations from the MQTT server, and stores it locally. Then there’s Owntracks Frontend, which is a much nicer user interface, with some nice features like viewing movement a day at a time. Continue reading “Meshtastic And Owntracks To Kick Your Google Habit” →

This Week In Security: Looney Tunables, Not A 0-day*, And Curl Warning

October 6, 2023 by 8 Comments

This week starts out with a nifty vulnerability in the glibc dynamic loader. This is an important step in running a binary executable on Linux, as it pulls the list of required shared libraries, and loads those libraries into memory. Glibc also includes a feature to adjust some runtime settings, via the GLIBC_TUNABLES environment variable. That’s where the vulnerability resides, and researchers from Qualsys obviously had a bit of fun in taking inspiration to pick the vulnerability name, “Looney Tunables”.

The problem is memory handling in the sanitizing parser. This function iterates through the environment variable, looking for strings of tunable1=aa, separated by colons. These strings get copied to the sanitized buffer, but the parsing logic goes awry when handling the malformed tunable1=tunable2=AAA. The first equals sign is taken at face value, copying the rest of the string into the buffer. But then the second equals sign is also processed as another key=value pair, leading to a buffer overflow.

The reason this particular overflow is interesting is that if the binary to be run is a Set-User-ID (SUID) root application, the dynamic loader runs as root, too. If the overflow can achieve code execution, then it’s a straightforward privilege escalation. And since we’re talking about it, you know there’s a way to execute code. It turns out, it’s possible to overwrite the pointer to the library search path, which determines where the dynamic loader will look for libraries. Tell it to look first in an attacker-controlled location, and you can easily load a malicious libc.so for instant code execution.

This vulnerability affects many Linux distros, and there’s already a Proof of Concept (PoC) published. So, it’s time to go check for updates for cve-2023-4911. Continue reading “This Week In Security: Looney Tunables, Not A 0-day*, And Curl Warning” →

This Week In Security: Magic Packets, GPU.zip, And Enter The Sandman

September 29, 2023 by 4 Comments

Leading out the news this week is a report of “BlackTech”, an Advanced Persistent Threat (APT) group that appears to be based out of China, that has been installing malicious firmware on routers around the world. This firmware has been found primarily on Cisco devices, and Cisco has released a statement clarifying their complete innocence and lack of liability in the matter.

It seems that this attack only works on older Cisco routers, and the pattern is to log in with stolen or guessed credentials, revert the firmware to a yet older version, and then replace it with a malicious boot image. But the real fun here is the “magic packets”, a TCP or UDP packet filled with random data that triggers an action, like enabling that SSH backdoor service. That idea sounds remarkable similar to Fwknop, a project I worked on many years ago. It would be sort of surreal to find some of my code show up in an APT.

Don’t Look Now, But Is Your GPU Leaking Pixels

There’s a bit debate on who’s fault this one is, as well as how practical of an attack it is, but the idea is certainly interesting. Compression has some interesting system side effects, and it’s possible for a program with access to some system analytics to work out the state of that compression. The first quirk being leveraged here is that GPU accelerated applications like a web browser use compression to stream the screen view from the CPU to the GPU. But normally, that’s way too many pixels and colors to try to sort out just by watching the CPU and ram power usage.

And that brings us to the second quirk, that in Chrome, one web page can load a second in an iframe, and then render CSS filters on top of the iframe. This filter ability is then used to convert the page to black and white tiles, and then transform the white tiles into a hard-to-compress pattern, while leaving the black ones alone. With that in place, it’s possible for the outer web page to slowly recreate the graphical view of the iframe, leaking information that is displayed on the page.

And this explains why this isn’t the most practical of attacks, as it not only requires opening a malicious page to host the attack, it also makes some very obvious graphical changes to the screen. Not to mention taking at least 30 minutes of data leaking to recreate a username displayed on the Wikipedia page. What it lacks in practicality, this approach makes up for in cleverness and creativity, though. The attack goes by the GPU.zip moniker, and the full PDF is available. Continue reading “This Week In Security: Magic Packets, GPU.zip, And Enter The Sandman” →

This Week In Security: WebP, Cavium, Gitlab, And Asahi Lina

September 22, 2023 by 15 Comments

Last week we covered the latest 0-day from NSO group, BLASTPASS. There’s more details about exactly how that works, and a bit of a worrying revelation for Android users. One of the vulnerabilities used was CVE-2023-41064, a buffer overflow in the ImageIO library. The details have not been confirmed, but the timing suggests that this is the same bug as CVE-2023-4863, a Webp 0-day flaw in Chrome that is known to be exploited in the wild.

The problem seems to be an Out Of Bounds write in the BuildHuffmanTable() function of libwebp. And to understand that, we have to understand libwebp does, and what a Huffman Table has to do with it. The first is easy. Webp is Google’s pet image format, potentially replacing JPEG, PNG, and GIF. It supports lossy and lossless compression, and the compression format for lossless images uses Huffman coding among other techniques. And hence, we have a Huffman table, a building block in the image compression and decompression.

What’s particularly fun about this compression technique is that the image includes not just Huffman compressed data, but also a table of statistical data needed for decompression. The table is rather large, so it gets Huffman compressed too. It turns out, there can be multiple layers of this compression format, which makes the vulnerability particularly challenging to reverse-engineer. The vulnerability is when the pre-allocated buffer isn’t big enough to hold one of these decompressed Huffman tables, and it turns out that the way to do that is to make maximum-size tables for the outer layers, and then malform the last one. In this configuration, it can write out of bounds before the final consistency check.

An interesting note is that as one of Google’s C libraries, this is an extensively fuzzed codebase. While fuzzing and code coverage are both great, neither is guaranteed to find vulnerabilities, particularly well hidden ones like this one. And on that note, this vulnerability is present in Android, and the fix is likely going to wait til the October security update. And who knows where else this bug is lurking. Continue reading “This Week In Security: WebP, Cavium, Gitlab, And Asahi Lina” →

This Week In Security: Blastpass, MGM Heist, And Killer Themes

September 15, 2023 by 7 Comments

There’s yet another 0-day exploit chain discovered as part of NSO Group’s Pegasus malware suite. This one is known as BLASTPASS, and it’s a nasty one. There’s no user interaction required, just receiving an iMessage containing a malicious PassKit attachment.

We have two CVEs issued so far. CVE-2023-41064 is a classic buffer overflow in ImageIO, the Apple framework for universal file format read and write. Then CVE-2023-41061 is a problem in the iOS Wallet implementation. Release 16.6.1 of the mobile OS addresses these issues, and updates have rolled out for macOS 11, 12, and 13.

It’s worth noting that Apple’s Lockdown mode does seem to block this particular exploit chain. Citizen Lab suggests that high-risk users of Apple hardware enable Lockdown Mode for that extra measure of security. Continue reading “This Week In Security: Blastpass, MGM Heist, And Killer Themes” →

This Week In Security: LastPass Shoe Drops, Keys Lost, And Train Whistles Attack

September 8, 2023 by 8 Comments

There has been a rash of cryptocurrency thefts targeting some unexpected victims. Over $35 million has been drained from just over 150 individuals, and the list reads like a who’s-who of the least likely to fall for the normal crypto scams. There is a pattern that has been noticed, that almost all of them had a seed phrase stored in LastPass this past November when the entire LastPass database was breached.

The bulletproof security of the LastPass system depends in part on the rate limiting of authenticating with the LastPass web service. Additionally, accounts created before security improvements in 2018 may have had master passwords shorter than 12 characters, and the hash iterations on those accounts may have been set distressingly low. Since attackers have had unrestricted access to the database, they’ve been able to run offline attacks against accounts with very low iterations, and apparently that approach has been successful.

Microsoft’s Signing Key

You may remember a story from a couple months ago, where Microsoft found the Chinese threat group, Storm-0558, forging authentication tokens using a stolen signing key. There was a big open question at that point, as to how exactly an outside group managed to access such a signing key.

This week we finally get the answer. A crash log from 2021 unintentionally included the key, and Microsoft’s automated redaction system didn’t catch it. That crash dump was brought into development systems, and an engineer’s account was later accessed by Storm-0558. That key should not have worked for enterprise accounts, but a bug in a Microsoft key validation allowed the consumer systems key to work for enterprise accounts. Those issues have been fixed, but after quite a wild ride. Continue reading “This Week In Security: LastPass Shoe Drops, Keys Lost, And Train Whistles Attack” →

This Week In Security: Not A Vulnerability, BGP Bug Propogation, And Press Enter To Hack

September 1, 2023 by 6 Comments

Curl was recently notified of a CVE, CVE-2020-19909, rated at a hair-raising 9.8 on the CVSS scale. And PostgreSQL has CVE-2020-21469, clocking in with a 7.5 severity. You may notice something odd about those two vulnerabilities, but I promise the 2020 date is only the tip of the iceberg here.

Let’s start with PostgreSQL. That vulnerability was only present in version 12.2, which released in February of 2020, and was fixed with the 12.3 release in May of that same year. The problem is a stack buffer overflow, which doesn’t seem to enable code execution, but does cause a denial of service situation. To trigger the bug? Repeatedly send the PostgreSQL daemon the SIGHUP signal.

If you’re familiar with Linux signals, that might sound odd. See, the SIGHUP signal technically indicates the end of a user session, but most daemons use it to indicate a restart or reload request. And to send this signal, a user has to have elevated privileges — elevated enough to simply stop the daemon altogether. Put simply, it’s not a security vulnerability, just a minor bug.

And now on to curl — This one is just bizarre. The issue is a integer overflow in the --retry-delay argument, which specifies in seconds how often curl should retry a failing download. The value is multiplied by 1000 to convert to milliseconds, resulting in an overflow for very large values. The result of that overflow? A smaller value for the retry delay.

[Daniel Stenberg] makes the point that this tale is a wonderful demonstration of the brokenness of the CVE system and NVD’s handling of it. And in this case, it’s hard not to see this as negligence. We have to work really hard to construct a theoretical scenario where this bug could actually be exploited. The best I’ve been able to come up with is an online download tool, where the user can specify part of the target name and a timeout. If that tool had a check to ensure that the timeout was large enough to avoid excess traffic, this bug could bypass that check. Should we be assigning CVEs for that sort of convoluted, theoretical attack?

But here’s the thing, that attack scenario should rate something like a CVSS of 4.8 at absolute worst. NVD assigned this a 9.8. There’s no way you can squint at this bug hard enough to legitimately rank it that severe. At the time of writing, the NVD lists this as “UNDERGOING REANALYSIS”.
Continue reading “This Week In Security: Not A Vulnerability, BGP Bug Propogation, And Press Enter To Hack” →