Hackaday editor Elliot Williams and contributor Jonathan Bennett discuss the past week of Hackaday. Freeman Dyson, who wanted to send us to space on the back of nuclear explosions, passed away. Only slightly less dangerous, we looked at self-balancing vehicles, 3D printed press brakes, and making rubies in the home lab. All the usual suspects make cameo appearances: robots, FPGAs, and open-source software.
Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!
Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!
A staple of today’s remote-controlled flight is the so-called FPV transmitter, allowing the pilot of a multirotor or other craft to see the world from onboard, as a pilot might do. It’s accessible enough that it can be found on toy multirotors starting at not much more than pocket money prices, and reliable enough that in its better incarnations it can send back high definition video at surprisingly long range.
In case you think of FPV flight as a recent innovation, the video below the break from [Larry Mitschke] should come as a revelation. In 1986 he was a bona-fide rockstar playing in a band, whose radio-controlled flight hobby led him into creating an FPV system for his planes and soaring above the Texas countryside at significant distance from his base while flying it watching a CRT screen.
The video is quite long but extremely watchable, all period footage with his narration here in 2020. We see his earliest experiments with a monochrome security camera and a video sender, and a whole host of upgrades until finally he can fly three miles from base with good quality video. 70 cm amateur TV makes an appearance with a steerable tracking antenna, he even makes a talking compass for when he loses himself. It’s an epic tale of hacking with what seems rudimentary equipment by our standards but was in fact the cutting edge of available video technology at a time when the state of the video art was moving rather fast. This is the work that laid the path for today’s $30 FPV toys, and for flying FPV from space.
Ready for more speculative execution news? Hope so, because both Intel and AMD are in the news this week.
The first story is Load Value Injection, a different approach to reading arbitrary memory. Rather than try to read protected memory, LVI turns that on its head by injecting data into a target’s data. The processor speculatively executes based on that bad data, eventually discovers the fault, and unwinds the execution. As per other similar attacks, the execution still changes the under-the-hood state of the processor in ways that an attacker can detect.
What’s the actual attack vector where LVI could be a problem? Imagine a scenario where a single server hosts multiple virtual machines, and uses Intel’s Secure Guard eXentensions enclave to keep the VMs secure. The low-level nature of the attack means that not even SGX is safe.
The upside here is that the attack is quite difficult to pull off, and isn’t considered much of a threat to home users. On the other hand, the performance penalty of the suggested fixes can be pretty severe. It’s still early in the lifetime of this particular vulnerability, so keep an eye out for further updates.
AMD’s Takeaway Bug
AMD also found itself on the receiving end of a speculative execution attack (PDF original paper here). Collide+Probe and Load+Reload are the two specific attacks discovered by an international team of academics. The attacks are based around the reverse-engineering of a hash function used to speed up cache access. While this doesn’t leak protected data quite like Spectre and Meltdown, it still reveals internal data from the CPU. Time will tell where exactly this technique will lead in the future.
To really understand what’s going on here, we have to start with the concept of a hash table. This idea is a useful code paradigm that shows up all over the place. Python dictionaries? Hash tables under the hood.
Imagine you have a set of a thousand values, and need to check whether a specific value is part of that set. Iterating over that entire set of values is a computationally expensive proposition. The alternative is to build a hash table. Create an array of a fixed length, let’s say 256. The trick is to use a hash function to sort the values into this array, using the first eight bits of the hash output to determine which array location each value is stored in.
When you need to check whether a value is present in your set, simply run that value through the hash function, and then check the array cell that corresponds to the hash output. You may be ahead of me on the math — yes, that works out to about four different values per array cell. These hash collisions are entirely normal for a hash table. The lookup function simply checks all the values held in the appropriate cell. It’s still far faster than searching the whole table.
AMD processors use a hash table function to check whether memory requests are present in L1 cache. The Takeaway researchers figured out that hash function, and can use hash collisions to leak information. When the hash values collide, the L1 cache has two separate chunks of memory that need to occupy the same cache line. It handles this by simply discarding the older data when loading the colliding memory. An attacker can abuse this by measuring the latency of memory lookups.checking
If an attacker knows the memory location of the target data, he can allocate memory in a different location that will be stored in the same cache line. Then by repeatedly loading his allocated memory, he knows whether the target location has been accessed since his last check. What real world attack does that enable? One of the interesting ones is mapping out the memory layout of ASLR/KASLR memory. It was also suggested that Takeaway could be combined with the Spectre attack.
There are two interesting wrinkles to this story. First, some have pointed out the presence of a thank-you to Intel in the paper’s acknowledgements. “Additional funding was provided by generous gifts from Intel.” This makes it sound like Intel has been funding security research into AMD processors, though it’s not clear what exactly this refers to.
Lastly, AMD’s response has been underwhelming. At the time of writing, their official statement is that “AMD believes these are not new speculation-based attacks.” Now that the paper has been publicly released, that statement will quickly be proven to be either accurate or misinformed.
Closed Source Privacy?
The Google play store and iOS app store is full of apps that offer privacy, whether it be a VPN, adblocker, or some other amazing sounding application. The vast majority of those apps, however, are closed source, meaning that you have little more than trust in the app publisher to ensure that your privacy is really being helped. In the case of Sensor Tower, it seems that faith is woefully misplaced.
A typical shell game is played, with paper companies appearing to provide apps like Luna VPN and Adblock Focus. While technically providing the services they claim to provide, the real aim of both apps is to send data back to Sensor Tower. When it’s possible, open source is the way to go, but even an open source app can’t protect you against a malicious VPN provider.
Does the word “#backdoor” seem frightening? That’s because it’s often used incorrectly – sometimes to deliberately create fear. Watch to learn the truth about backdoors and other types of network access. #cybersecuritypic.twitter.com/NEUXbZbcqw
[Robert Graham] thought the whole story was fishy, and decided to write about it. He makes two important points. First, the Wall Street Journal article cites anonymous US officials. In his opinion, this is a huge red flag, and means that the information is either entirely false, or an intentional spin, and is being fed to journalists in order to shape the news. His second point is that Huawei’s redefinition of government-mandated backdoors as “front doors” takes the line of the FBI, and the Chinese Communist Party, that governments should be able to listen in on your communications at their discretion.
Graham shares a story from a few years back, when his company was working on Huawei brand mobile telephony equipment in a given country. While they were working, there was an unspecified international incident, and Graham watched the logs as a Huawei service tech remoted into the cell tower nearest the site of the incident. After the information was gathered, the logs were scrubbed, and the tech logged out as if nothing had happened.
Did this tech also work for the Chinese government? The NSA? The world will never know, but the fact is that a government-mandated “front door” is still a back door from the users’ perspective: they are potentially being snooped on without their knowledge or consent. The capability for abuse is built-in, whether it’s mandated by law or done in secret. “Front doors” are back doors. Huawei’s gear may not be dirtier than anyone else’s in this respect, but that’s different from saying it’s clean.
Abusing Regex to Fool Google
[xdavidhu] was poking at Google’s Gmail API, and found a widget that caught him by surprise. A button embedded on the page automatically generated an API key. Diving into the Javascript running on that page, as well as an iframe that gets loaded, he arrived at an ugly regex string that was key to keeping the entire process secure. He gives us a tip, www.debuggex.com, a regex visualizer, which he uses to find a bug in Google’s JS code. The essence of the bug is that part of the URL location is interpreted as being the domain name. “www.example.com\.corp.google.com” is considered to be a valid URL, pointing at example.com, but Google’s JS code sees the whole string as a domain, and thinks it must be a Google domain.
For his work, [xdavidhu] was awarded $6,000 because this bit of ugly regex is actually used in quite a few places throughout Google’s infrastructure.
SMBv3 Wormable Flaw
Microsoft’s SMBv3 implementation in Windows 10 and Server 2019 has a vulnerability in how it handles on-the-fly compression, CVE-2020-0796. A malicious packet using compression is enough to trigger a buffer overflow and remote code execution. It’s important to note that this vulnerability doesn’t required an authenticated user. Any unpatched, Internet-accessible server can be compromised. The flaw exists in both server and client code, so an unpatched Windows 10 client can be compromised by connecting to a malicious server.
There seems to have been a planned coordinated announcement of this bug, corresponding with Microsoft’s normal Patch Tuesday, as both Fortinet and Cisco briefly had pages discussing it on their sites. Apparently the patch was planned for that day, and was pulled from the release at the last moment. Two days later, on Thursday the 12th, a fix was pushed via Windows update. If you have Windows 10 machines or a Server 2019 install you’re responsible for, go make sure it has this update, as proof-of-concept code is already being developed.
If you work on old radios, electronics is only one of the skills you need. The other is wood or metal working to restore the cabinets and chassis. However, more recent electronics have plastic and old plastic tends to turn yellow. [Odd Experiments] shows how to whiten plastic using a UV light source, aluminum foil, and hydrogen peroxide. Generally, ABS is the plastic at fault, especially those mixed with bromine as a fire retardant. You can see the results in the video below.
Note the peroxide in use was 12% — much stronger than what’s probably in your medicine cabinet. That’s usually only 3% solution, although you can get different strengths including some over 30% if you shop. However, if you search you’ll find that people have used 12%, 6%, and even 3% successfully, although we’d imagine it takes more time with 3%.
In the days of carburetors and leaf spring suspensions, odometer fraud was pretty simple to do just by disconnecting the cable or even winding the odometer backwards. With the OBD standard and the prevalence of electronics in cars, promises were made by marketing teams that this risk had all but been eliminated. In reality, however, the manipulation of CAN bus makes odometer fraud just as easy, and [Andras] is here to show us exactly how easy with a teardown of a few cheap CAN bus adapters.
We featured another project that was a hardware teardown of one of these devices, but [Andras] takes this a step further by probing into the code running on the microcontroller. One would imagine that basic measures would have been taken by the attackers to obscure code or at least disable debugging modes, but on this one no such effort was made. [Andras] was able to dump the firmware from both of his test devices and start analyzing them.
Analyzing the codes showed identical firmware running on both devices, which made his job half as hard. It looked like the code was executing a type of man-in-the-middle attack on the CAN bus which allowed it to insert the bogus mileage reading. There’s a lot of interesting information in [Andras]’s writeup though, so if you’re interested in CAN bus or attacks like this, it’s definitely worth a read.
