LibreView online reporting service

You may remember I complained about cloud-based solutions before. I have had harsh words about what are to me irresponsible self-hosting suggestions, and I’m not particularly impressed by how every other glucometer manufacturer appears to want their tools to be used, uploading to their cloud solutions what I would expect is a trove of real-world blood sugar reports from diabetics.

But as it happens, since I’m using the FreeStyle LibreLink app on my phone, I get the data uploaded to Abbott’s LibreView anyway. The LibreView service is geo-restricted, so it might not be available in all the countries where FreeStyle Libre is present, which probably is why the standalone Windows app still exists, and why the Libre 2 does not appear to be supported by it.

I haven’t used the service at all until this past month, when I visited the diabetic nurse at the local hospital (I had some blood sugar control issues), and she asked me to connect with their clinic. Turns out that (with the correct authorization), the staff at the clinic can access the real-time monitoring that I get from the phone. Given that this is useful to me, I find this neat, rather than creepy. Also it seems to require authorization on both sides, and it includes an email notification, so possibly they didn’t do that bad of a job with it.

The site is also a good replacement for the desktop app, when using the app with the phone, rather than the reader. It provides the same level of details in the reports, including the “pattern insights”, and a full view of the day-to-day aligned on weeks. Generally, those reports are very useful. And they are available on the site even for yourself, not just for the clinics, which is nice.

Also it turns out that the app tracks how many phones you’ve been using to scan the sensor — in my case, six. Although it’s over 1⅓ years since I have used a different one. I couldn’t see a way to remove the old phones, but at the same time, they are not reporting anything in and they don’t seem to have a limit on how many you can have.

Overall it’s effectively just a web app version of the information that was already available on the phone (but hard to extract and share) or on the reader (if you are still using that). I like the interface and it seems fairly friendly.

Also, you may remember (or notice, if you read the links above) that I had taken an aside pointing out how Diabetes Ireland misunderstood the graphs shown in the report when the Libre reached Ireland. I guess they were not alone, because in this version of the report Abbott explicitly labels the 10th-90th percentile highlight, the 25th-75th percentile highlight, and the median line. Of course this assumes that whoever is reading the graph is aware of “percentile” and “median” stand for — but that’s at least a huge step in the right direction.

FreeStyle Libre 2: Notes From The Deep Dive

As I wrote last week, I’ve started playing with Ghidra to dive into the FreeStyle Libre 2 software, to try and figure out how to speak the encrypted protocol, which is in the way to access the Libre 2 device as we already access the Libre 1.

I’m not an expert when it comes to binary reverse engineering — most of the work I’ve done around reverse engineering has been on protocols that are not otherwise encrypted. But as I said in the previous post, the binary still included a lot of debug logs. In particular, the logs included the name of the class, and the name of the method, which made it fairly easy to track down quite a bit of information on how the software works, as well as the way the protocols work.

I also got lucky to find a second implementation of their software protocol. At least a partial one. You see, there’s two software that can communicate with the old Libre system: the desktop software that appears to be available in Germany, Australia, and a few other countries, and the “driver” for LibreView, a service that allows GPs, consultants, and hospitals to remotely access the blood sugar readings of their patients. (I should write about it later.) While the main app is a single, mostly statically linked Qt graphical app, the “driver” is composed of a number of DLL modules, which makes it much easier to read.

Unfortunately it does not appear to support the Libre 2 and its encryption, but it does help to figure out other details around the rest of the transport protocol, since it’s much better logged, and provides clearer view of the function structure — it seems like the two packages actually come from the same codebase, as a number of classes share the same name between the two implementations.

The interesting part is trying to figure out what the various codenames mean. I found the names Orpheus and Apollo in the desktop app, and I assumed the former was the Libre and the latter the Libre 2, because the encryption is implemented only on the Apollo branch of the hierarchy, in particular in a class called ApolloCryptoLib. But then again, in the “driver” I found the codenames Apollo and Athena — and since the software says it supports the “Libre Pro” (which as far as I know is the US-only version that was released a few years ago), I’m wholly confused on what’s what now.

But as I said, the software does have parallel C++ class hierarchies, implementing lower-level and higher-level access controls for the two codenames. And because the logs include the class name it looks like most functions are instantiated twice (which is why I found it easier to figure out the flow for the non-crypto part from the “driver” module.) A lot of the work I’m doing appears to be manual vtable decoding, since there’s a lot of virtual methods all around.

What also became very apparent is that my hunch was right: the Libre 2 system uses basically the same higher level protocol as the Libre 1. Indeed, I can confirm not only that the text commands sent are the same (and the expected responses are the same, as well), but also that the binary protocol is parsed in the same way. So the only obstacle between glucometerutils and the Libre 2 is the encryption. Indeed, it seems like all three devices use the same protocol, which is either called Shazam, AAP or ATP — it’s not quite clear given the different set of naming conventions in the code, but it’s still pretty obvious that they share the same protocol, not just the HID transport, but also for defining higher level commands.

Now about the encryption, what I found from looking at the software is that there are two sets of keys that are used. The first is used in the “authentication” phase, which is effectively a challenge-response between the device and the software, based on the serial number of the device, and the other is used in the encrypted communication. This was fairly easy to spot, because one of the classes in the code is named ApolloCryptoLib, and it included functions with names like Encrypt, Decrypt, and GenerateKeys.

Also one note that important: the patch (sensor) serial number is not used for the encryption of the reader’s access. This is something that comes up time and time again. Indeed at least a few people have been telling me on Twitter that the Libre 2 sensors (or patches, as Abbott calls them) are also encrypted and that clearly they use the same protocol for the reader. But that’s not the case at all. Indeed, the same encryption happens when no patch was ever initialized, and the information on the patches is fetched from the reader as the last part of the initialization.

Another important piece of information that I found in the code is that the encryption uses separate keys for encryption and MAC. This means that there’s an actual encryption transport layer, similar to TLS, but not similar enough to worry me so much regarding the key material present.

With the code at hand, I also managed to confirm my original basic assumptions about the initialization using sub-commands, where the same message type is sent with a follow-up bytes including information on the command. The confirmation came from a log message calling the first byte in the command… subcmd. The following diagram is my current best understanding of the initialization flow:

Initialization sequence for the FreeStyle Libre 2 encryption protocol.

Unfortunately, most of the functions that I have found related to the encryption (and to the binary protocol, at least in the standalone app) ended up being quite complicated to read. At first I thought this was a side effect of some obfuscation system, but I’m no longer sure. It might be an effect of the compile/decompile cycle, but at least on Ghidra these appear as huge switch blocks, with what is effectively a state machine jumping around, even for the most simple of the methods.

Preview(opens in a new tab)

I took a function that is (hopefully) the least likely to get Abbott upset for me reposting it. It’s a simple function: it takes an integer and returns an integer. I called it int titfortat(int) because it took me a while to figure out what it was meant to do. It turns out to normalize the input to either 0, 1 or -1 — the latter being an error condition. It has an invocation of INT3 (a debugger trap), and it has the whole state machine construct I’ve seen in most of the other functions. What I found about this function is that it’s used to set a variable based on whether the generated keys are used for authentication or session.

The main blocker for me right now to figure out how the encryption is working, is that it looks like there’s an array of 21 different objects, each of which comes with what looks like a vtable, and only partially implemented. It does not conform to the way Visual C++ is building objects, so maybe it’s a static encryption library linked inside, or something different altogether. The functions I can reach from those objects are clearly cryptography-related: they include tables for SHA1 and SHA2 at least.

The way the objects are used is also a bit confusing: an initialization function appears to assign to each pointer in the array the value returned by a different function — but each of the functions appear to only return the value of a (different) global. Whenever the vtable-like is not fully implemented, it appears to be pointing at code that simply return an error constant. And when the code is calling those objects, if an error is returned it skips the object and go to the next.

On the other hand, this exercise is giving me a lot of insights about the insight of the overall HID transport as well as the protocol inside of it. For example, I finally found the answer to which checksum the binary messages include! It’s a modified CRC32, except that it’s calculated over 4-bit at a time instead of the usual 8, and thus requires a shortened lookup table (16 entries instead of 256) — and if you think that this is completely pointless, I tend to agree with you. I also found that some of the sub-commands for the ATP protocol include an extra byte before the actual sub-command identifier. I’m not sure how those are interpreted yet, and it does not seem to be a checksum, as they are identical for different payloads.

Anyway, this is clearly not enough information yet to proceed with implementing a driver, but it might be just enough information to start improving the support for the binary protocol (ATP) if the Libre 2 turns out not to understand the normal text commands. Which I find very unlikely, but you we’ll have to see.

IPv6 in 2020 — Nope, still dreamland

It’s that time of the year: lots of my friends and acquaintances went to FOSDEM, which is great, and at least one complained about something not working over IPv6, which prompted me to share once again my rant over the newcomer-unfriendly default network of a a conference that is otherwise very friendly to new people. Which then prompted the knee-jerk reaction of people who expect systems to work in isolation, calling me a hater and insulting me. Not everybody, mind you — on Twitter I did have a valid and polite conversation with two people, and while it’s clear we disagree on this point, insults were not thrown. Less polite people got blocked because I have no time to argue with those who can’t see anyone else’s viewpoint.

So, why am I insisting that IPv6 is still not ready in 2020? Well, let’s see. A couple of years ago, I pointed out how nearly all of the websites that people would use, except for the big social networks, are missing IPv6. As far as I could tell, nothing has changed whatsoever for those websites in the intervening two years. Even the number of websites that are hosted by CDNs like Akamai (which does support IPv6!), or service providers like Heroku are not served over IPv6. So once again, if you’re a random home user, you don’t really care about IPv6, except maybe for Netflix.

Should the Internet providers be worried, what with IPv4 exhaustion getting worse and worse? I’d expect them to be, because as Thomas said on Twitter, the pain is only going to increase. But it clearly has not reached the point where any of the ISPs, except a few “niche” ones like Andrews & Arnold, provide their own website over IPv6 — the exception appears to be Free, who if I understood it correctly, is one of the biggest providers in France, and does publish AAAA records for their website. They are clearly in the minority right now.

Even mobile phone providers, who everyone and their dog appear to always use as the example of consumer IPv6-only networks, don’t seem to care — at least in Europe. It looks like AT&T and T-Mobile US do serve their websites over IPv6.

But the consumer side is not the only reason why I insist that in 2020, IPv6 is still fantasy. Hosting providers don’t seem to have understood IPv6 either. Let’s put aside for a moment that Automattic does not have an IPv6 network (not even outbound), and let’s look at one of the providers I’ve been using for the past few years: Scaleway. Scaleway (owned by Iliad, same group as Online.net) charges you extra for IPv4. It does, though, provide you with free IPv6. It does not, as far as I understand, provide you with multiple IPv6 per server, though, which is annoying but workable.

But here’s a quote from a maintenance email they sent a few weeks ago:

During this maintenance, your server will be powered off, then powered on on another physical server. This operation will cause a downtime of a few minutes to an hour, depending on the size of your local storage. The public IPv4 will not change at migration, but the private IPv4 and the IPv6 will be modified due to technical limitations.

Scaleway email, 2020-01-28. Emphasis theirs.

So not only the only stable address the servers could keep is the IPv4 (which, as I said, is a paid extra), but they cannot even tell you beforehand which IPv6 address your server will get. Indeed, I decided at that point that the right thing to do was to just stop publishing AAAA records for my websites, as clearly I can’t rely on Scaleway to persist them over time. A shame, I would say, but that’s my problem: nobody is taking IPv6 seriously right now but a few network geeks.

But network geeks also appear to like UniFi. And honestly I do, too. It worked fairly well for me, most of the time (except for the woes of updating Mongodb), and it does mostly support IPv6. I have a full IPv6 setup at home with UniFi and Hyperoptic. But at the same time, the dashboard is only focused on IPv4, everywhere. A few weeks ago it looked like my IPv6 network had a sad (I only noticed because I was trying to reach one of my local machines with its AAAA hostname), and I had no way to confirm it was the case: I eventually just rebooted the gateway, and then it worked fine (and since I have a public IPv4, Hyperoptic gives me a stable IPv6 prefix, so I didn’t have to worry about that), but even then I couldn’t figure out if the gateway got any IPv6 network connection from its UIs.

I’m told OpenWRT got better about this. You’re no longer required to reverse engineer the source to figure out how to configure a relay. But at the same time, I’m fairly sure they are again niche products. Virgin Media Ireland’s default router supported IPv6 — to a point. But I have yet to see any Italian ISP providing even the most basic of DS-Lite by default.

Again, I’m not hating on the protocol, or denying the need to move onto the new network in short term. But I am saying that network folks need to start looking outside of their bubble, and try to find the reasons for why nothing appears to be moving, year after year. You can’t blame it on the users not caring: they don’t want to geek out on which version of the Internet Protocol they are using, they want to have a working connection. And you can’t really expect them to understand the limits of CGNs — 64k connections might sound ludicrously few to a network person, but for your average user it sounds too much: they only are looking at one website at a time! (Try explaining to someone who has no idea how HTTP works that you get possibly thousands of connections per tab.)

Leveling up my reverse engineering: time for Ghidra

In my quest to figure out how to download data from the Abbott FreeStyle Libre 2, I decided that figuring it out just by looking at the captures was a dead end. While my first few captures had me convinced the reader would keep sending the same challenge, and so I could at least replay that, it turned out to be wrong, and that excluded most of the simplest/silliest of encryption schemes.

As Pierre suggested me on Twitter, the easiest way to find the answer would be to analyze the binary itself. This sounded like a hugely daunting task for myself, as I don’t speak fluent Intel assembly, and particularly I don’t speak fluent Windows interfaces. The closest I got to this in the past has been the reverse engineering of the Verio, in which I ran the software on top of WinDbg and discovered, to my relief, that they not just kept some of the logging on, but also a whole lot of debug logs that made it actually fairly easy to reverse the whole protocol.

But when the options are learning enough about cryptography and cryptanalysis to break the encoding, or spend time learning how to reverse engineer a Windows binary — yeah I thought the latter would suit me better. It’s not like I have not dabbled in reversing my own binaries, or built my own (terrible) 8086 simulator in high school, because I wanted to be able to see how the registers would be affected, and didn’t want to wait for my turn to use the clunky EEPROM system we used in the lab (this whole thing is probably a story for another day).

Also, since the last time I considered reversing a binary (when I was looking at my laptop’s keyboard), there’s a huge development: the NSA released Ghidra. For those who have not heard, Ghidra is a tool to reverse engineer binaries that includes a decompiler, and a full blown UI. And it’s open source. Given that the previous best option for this was IDA Pro, with thousands of dollars of licenses expected, this opened a huge amount of doors.

So I spent a weekend in which I had some spare time to try my best on reversing the actual code coming from the official app for the Libre 2 — I’ll provide more detail of that once I understand it better, and I know which parts are critical to share, and which one would probably get me in trouble. In general, I did manage to find out quite a bit more about the software, the devices, and the protocol — if nothing else, because Abbott left a bunch of debug logging disabled, but built in (and no, this time the WinDbg trick didn’t work because they seems to have added an explicit anti-debugger exception (although, I guess I could learn to defeat that, while I’m at it).

Because I was at first a bit skeptical about my ability to do anything at all with this, I also have been running it in an Ubuntu VM, but honestly I’m considering switching back to my normal desktop because something on the Ubuntu default shell appears to mess with Java, and I can’t even run the VM at the right screen size. I have also considered running this in a Hyper-V virtual machine on my Gamestation, but the problem with that appears to be graphics acceleration: installing OpenSUSE onto it was very fast, but trying to use it was terribly sloppy. I guess the VM option is a bit nicer in the sense that I can just save it to power off the computer, as I did to add the second SSD to the NUC.

After spending the weekend on it, and making some kind of progress, and printing out some of the code to read it on paper in front of the TV with pen and marker, well… I think I’m liking the idea of this but it’ll take me quite a while, alone, to come up with enough of a description that it can be implemented cleanroom. I’ll share more details on that later. For the most part, I felt like I was for the first time cooking something that I’ve only seen made in the Great British Bake Off — because I kept reading the reports that other (much more experienced) people wrote and published, particularly reversing router firmwares.

I also, for once, found a good reason to use YouTube for tutorials. This video by MalwareTech (yes the guy who got arrested after shutting WannaCry down by chance) was a huge help to figure out features I didn’t even know I wanted, including the “Assume Register” option. Having someone who knows what he’s doing explore a tool I don’t know was very helpful, and indeed it felt like Adam Savage describing his workshop tools — a great way to learn about stuff you didn’t know you needed.

My hope is that by adding this tool to my toolbox – like Adam Savage indeed says in his Every Tool’s A Hammer (hugely recommended reading, by the way) – is that I’ll be able to use it not just to solve the mystery of the Libre 2’s encryption. But also that of the nebulous Libre 1 binary protocol, which I never figured out (there’s a few breadcrumbs I already found during my Ghidra weekend). And maybe even to figure out the protocol of one of the gaming mice I have at home, which I never completed either.

Of course all of this assumes I have a lot more free time than I have had for the past few years. But, you know, it’s something that I might have ideas about.

Also as a side note: while doing the work to figure out which address belongs to what, and particularly figure out the jumps through vtables and arrays of global objects (yeah that seems to be something they are doing), I found myself needing to do a lot of hexadecimal calculations. And while I can do conversions from decimal to binary in my head fairly easily, hex is a bit too much for me. I have been using the Python interactive interpreter for that, but that’s just too cumbersome. Instead, I decided to get myself a good old physical calculator — not least because the Android calculator is not able to do hex, and it seems like there’s a lack of “mid range” calculators: you get TI-80 emulators fairly easily, but most of the simplest calculators don’t have hex. Or they do, but they are terrible at it.

I looked up on Amazon for the cheapest scientific calculator that I could see the letters A-F on, and ordered a Casio fx-83GT X — that was a mistake. When it arrived, I realized that I didn’t pay attention to finding one with the hex key on it. The fx-83GT does indeed have the A-F inputs — but they are used for defining variables only, and the calculator does not appear to have any way to convert to hexadecimal nor to do hexadecimal-based operations. Oops.

Instead I ordered a Sharp WriteView EL-W531, which supports hex just fine. It has slightly smaller, but more satisfying, keys, but it’s yet another black gadget on my table (the Casio is light blue). I’ll probably end up looking out for a cute sticker to put on it to see it when I close it for storage.

And I decided to keep the Casio as well — not just because it’s handy to have a calculator at home when doing paperwork, even with all the computers around, but also because it might be interesting to see how much of the firmware is downloadable, and whether someone has tried flashing a different model’s firmware onto it, to expand its capabilities: I can’t believe the A-F keys are there just for the sake of variables, my guess is that they are there because the same board/case is used by a higher model that does support hex, and I’d expect that the only thing that makes it behave one way or the other is the firmware — or even just flags in it!

At any rate, expect more information about the Libre 2 later on this month or next. And if I decide to spend more time on the Casio as well, you’ll see the notes here on the blog. But for now I think I want to get at least some of my projects closer to completion.

More British cashback: Airtime Rewards

You could say that one of this blog’s “side hustles” is talking about cashback offers. I think it all started with the idea of describing how privacy compromises work, but more recently focused on just one fintech’s free money distribution. This time I have something to talk about that again touches on both points.

Airtime Rewards is a cashback program that was advertised to me by my mobile phone provider, and it is indeed a bit different from other programs I’ve seen, because the cashback can only be redeemed as credit to your (or someone else’s) mobile phone bill — thus the Airtime part of the name I guess.

The way it works is pretty much reminiscent of the US-only “Rewards Club Dining”: you sign up for an account, and you give them your payment cards’ details — PAN (the 16-digit number), CVV and expiration date. They don’t charge you, instead they set up a “trap” on those cards, so that they are notified when you spend on them.

And this is honestly borderline even for me, as a privacy invasion. I haven’t worked deep enough in payment systems to actually know how those traps are implemented, but it sounds like the companies like Airtime Rewards are getting pretty much a huge feed of your spend, not just related to the vendors they offer cashback for. But don’t quote me on that because I don’t actually know how they implemented it, it might be totally benign.

Now let’s preface this with one important bit of information: only Visa and MasterCard cards are usable for either of these two options. American Express is, once again, a walled garden — they are effectively the iPhone of payment cards, for good and bad (including costs). Just like they don’t allow vendors to scam people via DCC, they don’t seem to allow traps of cards for payment.

So how does this program fare, and why do I even bother talking about it? Well first of all, if you’re the type of person who don’t like leaving money on the table at any chance, it’s actually pretty good, as long as you visit the stores involved. I signed up for this just before Christmas shopping, because I knew we were going to spend a bit of money at Debenhams, and they had a nice 5% cashback, but even just the couple of orders from Waitrose, and the usual stock-up at Boots were enough to get back ~£30 in a couple of months. It’s not going to pay for the phone bill constantly, but it does pay for a few vanity domain names, at the end of the year.

The cashback offers from various retailers are there to make customers chose them over alternatives. This has worked a tiny little bit with Airtime Rewards, in the sense that I factored in the cashback offer when choosing between ordering from Morrisons, Waitrose or Ocado — because sometimes the cheaper is actually winning due to cashback offers, either Airtime Rewards, or Santander. For the most part, a number of our usual destinations are part of the program, so Boots, Pizza Express, Ryman, or (more recently) Uniqlo are nice to see. For a while, Morrisons was also part of the program, but that has not been the case for very long — it appears there’s some variability on which retailers sign up, that suggests there may be a middleman company handling the retailers connections.

Speaking of Santander cashback, because Airtime Rewards attaches to the card number itself, it is possible to combine the two offers, making it closer to (sometimes) 10% cashback than 5%. The same is true with Curve, although note that you can’t stack Curve and banks’ offers, as the latter only see the charge coming directly from Curve.

One very annoying thing with the way Airtime Rewards work, compared to offers by banks, Curve, and American Express, is that they only hand you the cashback credit after a “confirmation period” by the retailer — namely it seems to be matching the various retailers’ return policies. Which means it’s taking 90 days to confirm a Morrisons transaction, despite Morrisons not being in the program anymore. It feels very strange for restaurants (like Pizza Express) needing 35 days to confirm a transaction though — I don’t think I would be able to return my lunch there.

One important thing to note is that the offers are also not quite uniform: while most of the offers are valid for both MasterCard and Visa, some are only available on one or the other circuit. It’s not a big deal for me, as I always preferred having one card on each, but it’s something to keep in mind. Not all the offers are available online, either – again the Morrisons offer I referred to above was only available in store, which excluded home delivery – and then there’s the catch with Google Pay and Apple Pay.

You see, when you pay with Google Pay or Apple Pay, you’re using a “virtual card” — the PAN of the card reported to the merchant does not match the one printed (or embedded) in the card that you connected. This has been described as a privacy-preserving feature by many, although I can’t find any obvious official documentation of this. The idea being, if you pay alternatively with your phone (or different phones) and your physical card, the merchants shouldn’t be able to tell you’re the same customer (but the bank, obviously, can). Turns out this is also not true, because indeed you can attach the PAN of a physical card to Airtime Rewards, and you get your cashback when you pay with Google Pay (connected to that particular card) at some of the retailers.

I say some, not just because Airtime Rewards explicitly only marks some offers as compatible with Google Pay, but also because experimentally I can tell you that even some of the offers that are marked as Google Pay compatible don’t actually work when paying with Google Pay. That was the case, for instance, of Carluccio’s: the only time the cashback got registered was the one time I paid explicitly with my physical card.

What this does mean, though, is that there’s a way for third parties (beside you, your bank, and Google/Apple) to connect payments by virtual cards with the corresponding physical card. And honestly, that’s the scariest part of this whole program.

So, at the end of the day, what if you’re interested in signing up for this? You can sign up here, and use code P7YR6TPE to get £1.5 bonus for you (and a matching one for me). Or maybe you can check with your mobile provider, that might have an even better sign-up offer, honestly.

Windows Backup Solutions: trying out Acronis True Image Backup 2020

One of my computers is my Gamestation, which to be honest has not ran a game in many months now, which runs Windows out of necessity, but also because honestly sometimes I just need something that works out of the box. The main usage of that computer nowadays is Lightroom and Photoshop for my photography hobby.

Because of the photography usage, backups are a huge concern to me (particularly after movers stole my previous gamestation), and so I have been using a Windows tool called FastGlacier to store a copy of most of the important stuff to Amazon Glacier service, in addition to letting Windows 10 do its FileHistory magic on an external hard drive. Not a cheap option, but (I thought) a safe and stable one. Unfortunately the software appears to not being developed anymore, and with one of the more recent Windows 10 updates it stopped working (and since I had set it up as a scheduled operation, it failed silently, which is the worst thing that can happen!)

My original plan for last week (at the time of writing), was to work on pictures, as I have shots from trip over three years ago that I have still not wandered through, rather than working on reverse engineering. But when I noticed the lacking backups, I decided to put that on hold until the backup problem was solved. The first problem was finding a backup solution that would actually work, and that wouldn’t cost an arm and a leg. The second problem was that of course most of the people I know are tinkerers that like rube-goldberg solutions such as using rclone on Windows with the task scheduler (no thanks, that’s how I failed the Glacier backups).

I didn’t have particularly high requirements: I wanted a backup solution that would do both local and cloud backups — because Microsoft has been reducing the featureset of their FileHistory solution, and so relying on it feels a bit flaky. And the ability to store more than a couple of terabytes on the cloud solution (I have over 1TB of RAW shots!), even at a premium. I was not too picky on price, as I know features and storage are expensive. And I wanted something that would just work out of the box. A few review reads later, I found myself trying Acronis True Image Backup. A week later, I regret it.

I guess my best lesson learnt from this is that Daniel is right, and it’s not just about VPNs: most review sites seem to be scoring higher the software they get more money from via affiliate links (you’ll notice that in this blog post there won’t be any!) So while a number of sites had great words for Acronis’s software, I found it sufficiently lacking that I’m ranting about it here.

So what’s going on with the Acronis software? First of all, while it does support both “full image” and “selected folders” modes, you need to be definitely aware that the backup is not usable as-is: you need the software to recover the data. Which is why it comes with bootable media, “survival kits”, and similar amenities. This is not a huge deal to me, but it’s still a bit annoying, when FileHistory used to allow direct access to the files. It also locks you in in accessing the backup with the software, although Acronis makes the restore option available even after you let your subscription expire, which is at least honest.

Then the next thing that was clear to me was that the speed of the cloud backup is not the strongest suit of Acronis. The original estimate for backing up the 2.2TB of data that I expected to back up was on the mark at nearly six days. To be fair to Acronis, the process went extremely smoothly, it never got caught up, looped, crashed, or slowed down. The estimate was very accurate, and indeed, running this for about 144 hours was enough to have the full data backed up. Their backup status also shows the average speed of the processes, that matched my estimate while the backup was running, of 50Mbps.

The speed is the first focus of my regret. 50Mbps is not terribly slow, and for most people this might be enough to saturate their Internet uplink. But not for me. At home, my line is provided by Hyperoptic, with a 1Gbps line that can sustain at least 900Mbps upload. So seeing the backup bottlenecked by this was more than a bit annoying. And as far as I can tell, there’s no documentation of this limit on the Acronis website at the time of writing.

When I complained on Twitter about this, it was mostly in frustration for having to wait, but I was considering the 50Mbps speed at least reasonable (although I would have considered paying a premium for faster uploads!) the replies I got from support have gotten me more upset than before. Their Twitter support people insisted that the problem was with my ISP and sent me to their knowledgebase article on using the “Acronis Cloud Connection Verification Tool” — except that following the instruction showed I was supposed to be using their “EU4” datacenter, for which there is no tool. I was then advise to file a ticket about it. Since then, I appear to have moved back to “EU3” — maybe EU4 was not ready yet.

The reply to the ticket was even more of an absurdist mess. Beside a lot of words to explain “speed is not our fault, your ISP may be limiting your upload” (fair, but I already noted to them that I knew that was not the case), one of the steps they request you to follow is to go to one of their speedtest apps — which returns a 504 error from nginx, oops! Oh yeah and you need to upload the logs via FTP. In 2020. Maybe I should call up Foone to help. (Windows 10, as it happens, still supports FTP write-access via File Explorer, but it’s not very discoverable.)

Both support people also kept reminding me that the backup is incremental. So after the first cloud backup, everything else should be a relatively small amount of data to be copied. Except that I’m not sold onto that either, still: 128GB of data (which is the amount of pictures I came back from Budapest with), would take nearly six hours to back up.

When I finally managed to get a reply that was not directly from a support script, they told me to run the speedtest on a different datacenter, EU2. As it turns out, this is their “Germany” datacenter. This was very clear by tracerouting the IP addresses for the two hosts: EU3 is connected directly to LINX, EU2 goes back to AMS, then FRA (Frankfurt). The speedtest came out fairly reasonable (around 250Mbps download, 220Mbps upload), so I shared the data they requested in the ticket… and then wondered.

Since you can’t change the datacenter you backup to once you started a backup, I tried something different: I used their “Archive” feature, and tried to archive a multi-gigabyte file, but to their Germany datacenter, rather than the United Kingdom one (against their recommendation of «select the country that is nearest to your current location»). Instead of a 50Mbps peak, I got a 90Mbps peak, with a sustained of 67Mbps. Now this is still not particularly impressive, but it would have cut down the six days to three, and the five hours to around two. And clearly it sounds like their EU3 datacenter is… not good.

Anyway, let’s move on and look at local backups, which Acronis is supposed to take care of by itself. For this one at first I wanted to use the full image backup, rather than selecting folders like I did for the cloud copy, since it would be much cheaper, and I have a 9T external harddrive anyway… and when you do that, Acronis also suggests you to create what they call the “Acronis Survival Kit” — which basically means turning the external hard drive bootable, so that you can start up and restore the image straight from it.

The first time I tried setting it up that way, it formatted the drive, but it didn’t even manage to get Windows to connect the new filesystem. I got an error message linking me to a knowledgebase article that… did not exist. This is more than a bit annoying, but I decided to run a full SMART check on the drive to be safe (no error to be found), and then try again after a reboot. Then it finally seemed to work, but here’s where things got even more hairy.

You see, I’ve been wanting to use my 9TB external drive for the backup. A full image of my system was estimated at 2.6TB. But after the Acronis Survival Kit got created, the amount of space available for the backup on that disk was… 2TB. Why? It turned out that the Kit creation caused the disk to be repartitioned as MBR, rather than the more modern GPT. And in MBR you can’t have a (boot) partition bigger than 2TB. Which means that the creation of the Survival Kit silently decreased my available space to nearly 1/5th!

The reply from Acronis on Twitter? According to them my Windows 10 was started in “BIOS mode”. Except it didn’t. It’s set up with UEFI and Secure Boot. And unfortunately it doesn’t seem like there’s an easy way to figure out why the Acronis software thinks it’s that way. But worse than that, the knowledgebase article says that I should have gotten a warning, which I never did.

So what is it going to be at the end of the day? I tested the restore from Acronis Cloud, and it works fine. Acronis has been in business for many years, so I don’t expect them to disappear next year. So the likeliness of me losing access to these backups is fairly low. I think I may just stick to them for the time being, and hope that someone in the Acronis engineering or product management teams can read this feedback and think about that speed issue, and maybe start considering the idea of asking support people to refrain from engaging with other engineers on Twitter with fairly ridiculous scripts.

But to paraphrase a recent video by Techmoan, these are the type of imperfections (particularly the mis-detected “BIOS booting” and the phantom warning), that I could excuse to a £50 software package, but that are much harder to excuse in a £150/yr subscription!

Any suggestions for good alternatives to this would be welcome, particularly before next year, when I might reconsider if this was good enough for me, or a new service is needed. Suggestions that involve scripts, NAS, rclone, task scheduling, self-hosted software will be marked as spam.

USB capturing in 2020

The vast majority of the glucometer devices I reverse the protocol of use USB to connect to a computer. You could say that all of those that I successfully reversed up to now are USB based. Over the years, the way I capture USB packets to figure out a protocol changed significantly, starting from proprietary Windows-based sniffers, and more recently involving my own opensource trace tools. The process evolution was not always intentional — in the case of USBlyzer, it was pretty much dead a few years after I started using it, plus the author refused to document the file format, and by then even my sacrificial laptop was not powerful enough to keep running all the tools I needed.

I feel I’m close to another step on the evolution of my process, and once again it’s not because of me looking to improve the process as much as is the process not working on modern tools. Let me start by explaining what the situation is, because there are two nearly separate issues at play here.

The first issue is that either OpenSuse or the kernel changed the way the debugfs is handled. For those who have not looked at this before, debugfs is what lives in /sys/kernel/debug, and provides the more modern interface for usbmon access; the old method via /dev/usbmonX is deprecated, and Wireshark will not even show up the ability to capture USB packets without debugfs. Previously, I was able to manually change the ownership of the usbmon debugfs paths to my user, and started Wireshark as user to do the capturing, but as of January 2020, it does not seem to be possible to do that anymore: the debugfs mount is only accessible to root.

Using Wireshark as root is generally considered a really bad idea, because it has a huge attack surface, in particular when doing network captures, where the input would literally be to the discretion of external actors. It’s a tinsy bit safer when capturing USB because even when the device is fairly unknown, the traffic is not as controllable, so I would have flinched, but not terribly, to use Wireshark as root — except that I can’t sudo wireshark and have it paint on X. So the remaining alternative is to use tshark, which is a terminal utility that implements the same basics as Wireshark.

Unfortunately here’s the second problem: the last time I ran a lot of captures was when I was working on the Beurer glucometer (which I still haven’t gotten back to, because Linux 5.5 is still unreleased at the time of writing, and that’s the first version that’s not going to go into a reset loop with the device), and I was doing that work from my laptop, and that’s relevant. While the laptop’s keyboard and touchpad are USB, the ports are connected to a different bus internally. Since usbmon interfaces are set by bus, that made it very handy: I only needed to capture on the “ports” bus, and no matter how much and what I typed, it wouldn’t interfere in my captures at all.

You can probably see where this is going: I’m now using a NUC on my desk, with an external keyboard and the Elecom trackball (because I did manage to hurt my wrist while working on the laptop, but that’s a story for another post). And now all the USB 2.0 ports are connected to the same bus. Capturing the bus means getting all the events for keypresses, mouse movements, and so on.

If you have some experience with tcpdump or tshark, you’d think that this is an easy problem to solve: it’s not uncommon having to capture network packets from an SSH connection, which you want to exclude from the capture itself. And the solution for that is to apply a capture filter, such as port not 22.

Unfortunately, it looks like libpcap (which means Wireshark and tshark) does not support capture filters on usbmon. The reasoning provided is that since the capture filters for network are implemented in BPF, there’s no fallback for usbmon that does not have any BPF capabilities in the kernel. I’m not sure about the decision, but there you go. You could also argue that adding BPF to usbmon would be interesting to avoid copying too much data from the kernel, but that’s not something I have particular interest in exploring right now.

So how do you handle this? The suggested option is to capture everything, then use Wireshark to select a subset of packets and save the capture again. This should allow you to have a limited capture that you can share without risking having shared a keylogger off your system. But it also made me think a bit more.

The pcapng format, which Wireshark stores usbmon captures in, is a fairly complicated one, because it can include a lot of different protocol information, and it has multiple typed blocks to store things like hardware interface descriptions. But for USB captures, there’s not much use in the format: not only the Linux and Windows captures (the latter via usbpcap) are different formats altogether, but also the whole interface definition is, as far as I can tell, completely ignored. Instead, if you need a device descriptor, you need to scan the capture for a corresponding request (which usbmon-tools now does.)

I’m now considering just providing a simpler format to store captured data with usbmon-tools, either a simple 1:1 conversion from pcapng, with each packet just size-prefixed, and a tool to filter down the capture on the command line (because honestly, having to load Wireshark to cut down a capture is a pain), or a more complicated format that can store the descriptors separately, and maybe bundle/unbundle them across captures so that you can combine multiple fragments later. If I was in my bubble, I would be using protocol buffers, but that’s not particularly friendly to integrate in a Python module, as far as I can tell. Particularly if you want to be able to use the tools straight out of the git clone.

I guess that since I’m already using construct, I could instead design my own simplistic format. Or maybe I could just bite the bullet, use base64-encoded bytearrays, and write the whole capture session out in JSON.

As I said above, pcapng supports Windows and Linux captures differently: on Linux, the capture format is effectively the wire format of usbmon, while on Linux, it’s the format used by usbpcap. While I have not (yet, at the time of writing) added support to usbmon-tools to load the usbpcap captures, I don’t see why it shouldn’t work out that way. If I do manage to load usbpcap files, though, I would need a custom format to copy these to.

If anyone has a suggestion I’m open to them. One thing that I may try is to use Protocol Buffers but submit the generated source files to parse and serialize the object.

FreeStyle Libre 2: encrypted protocol notes

When I had to write (in a hurry) my comments on Abbott’s DMCA notice to GitHub, I note that I have not had a chance to get my hands onto the Libre 2 system yet, because it’s not sold in the UK. After that, Benjamin from MillionFriends reached out to me to hear if I would be interested in giving a try to figure out how the reader itself speaks with the software. I gladly obliged, and spent most of the time I had during a sick week to get an idea of where we are with this.

While I would lie if I said that we’re now much closer to be able to download data from a Libre 2 reader, I can at least say that we have some ideas of what’s going on right now. So let me try to introduce the problem a second, because there’s a lot of information out there, and while there’s some of it that is quite authoritative (particularly as a few people have been reverse engineering the actual binaries), a lot of it is guesswork and supposition.

The Libre and Libre 2 systems are very similar — they both have sensors, and they both have readers. Technically, you could say that the mobile app (for Android or iOS) also makes up part of the system. The DMCA notice from Abbott that stirred so much trouble above was related to modifications to the mobile application — but luckily for me, my projects and my interests lay quite far away from that. The sensors can be “read” by their respective reader devices, or with a phone with the correct app on it. When reading the sensors with the reader, the reader itself stores the historical data and a bunch more information. You can download that data from the reader onto a computer with Windows or macOS with the official software from Abbott (assuming you can download a version of it that works for you, I couldn’t find a good download page for this on the UK website, but I was provided an EU version of the software as well.)

For the Libre system, I have attempted reversing the protocol, but ultimately it was someone else contributing the details of an usable protocol that I implemented in glucometerutils. For the Libre 2, the discussion already suggested it wouldn’t be the same protocol, and that encryption was used by the Libre 2 reader. As it turns out, Abbott really does not appear to appreciate customers having easy access to their data, or third parties building tools around their devices, and they started encrypting the communication between the sensors and the reader or app in the new system.

So what’s the state with the Libre 2? Well, one of the good news is that the software that I was given works with both the Libre and Libre 2 systems, so I could compare the USB captures on both systems, and that will (as I’ll show in a moment) help significantly. It also showed that the basics of the Abbott HID protocol were maintained: most of the handshake, the message types and the maximum message size. Unfortunately it was clear right away that indeed most of the messages exchanged were encrypted, because the message length made no sense (anything over 62 as length was clearly wrong).

Now, the good news is that I have built up enough interfaces in usbmon-tools that I could use to build a much more reusable extractor for the FreeStyle protocol, and introduce more of the knowledge of the encryption to it, so that it can be used for others. Being able to release these extraction tools I write, instead of just using them myself and letting them rot, was my primary motivation behind building usbmon-tools, so you could say that that’s an achieved target.

So earlier I said that I was lucky the software works with both the Libre and Libre 2 readers. The reason why that was luck, it’s because it shows that the sequence of operations between the two is nearly the same, and that some of the messages are not actually encrypted on the Libre 2 either (namely, the keepalive messages). Here’s the handshake from my Libre 1 reader:

[ 04] H>>D 00000000: 

[ 34] H<<D 00000000: 16                                                . 

[ 0d] H>>D 00000000: 00 00 00 02                                       .... 

[ 05] H>>D 00000000: 

[ 15] H>>D 00000000: 

[ 06] H<<D 00000000: 4A 43 4D 56 30 32 31 2D  54 30 38 35 35 00        JCMV021-T0855. 

[ 35] H<<D 00000000: 32 2E 31 2E 32 00                                 2.1.2. 

[ 01] H>>D 00000000: 

[ 71] H<<D 00000000: 01                                                . 

[ 21] H>>D 00000000: 24 64 62 72 6E 75 6D 3F                           $dbrnum? 

[ 60] H<<D 00000000: 44 42 20 52 65 63 6F 72  64 20 4E 75 6D 62 65 72  DB Record Number
[ 60] H<<D 00000010: 20 3D 20 33 37 32 39 38  32 0D 0A 43 4B 53 4D 3A   = 372982..CKSM:
[ 60] H<<D 00000020: 30 30 30 30 30 37 36 31  0D 0A 43 4D 44 20 4F 4B  00000761..CMD OK
[ 60] H<<D 00000030: 0D 0A                                             .. 

[ 0a] H>>D 00000000: 00 00 37 C6 32 00 34                              ..7.2.4 

[ 0c] H<<D 00000000: 01 00 18 00                                       ....

Funnily enough, while this matches the sequence that Xavier described for the Insulinx, and that I always reused for the other devices too, I found that most of this exchange is for the original software to figure out which device you connected. And since my tools require you to know which device you’re using, I actually cleaned up the FreeStyle support code in glucometerutils to shorten the initialization sequence.

To describe the sequence in prose, the software is requesting the serial number and software version of the reader (commands 0x05 and 0x15), then initializing (0x01) and immediately using the text command $dbrnum? to know how much data is stored on the device. Then it starts using the “binary mode” protocol that I started on years ago, but never understood.

For both the systems, I captured the connection establishment, from when the device is connected to the Windows virtual machine to the moment when you can choose what to do. The software is only requesting a minimal amount of data, but it’s still quite useful for comparison. Indeed, you can see that after using the binary protocol to fetch… something, the software sends a few more text commands to confirm the details of the device:

[ 0b] H<<D 00000000: 12 3C AD 93 0A 18 00 00  00 00 00 9C 2D EA 00 00  .<..........-...
[ 0b] H<<D 00000010: 00 00 00 0E 00 00 00 00  00 00 00 7C 2A EA 00 00  ...........|*...
[ 0b] H<<D 00000020: 00 00 00 16 00 00 00 00  00 00 00 84 2D EA 00 21  ............-..!
[ 0b] H<<D 00000030: C2 25 43                                          .%C 

[ 21] H>>D 00000000: 24 70 61 74 63 68 3F                              $patch? 

[ 0d] H>>D 00000000: 3D 12 00 00                                       =... 

[ 60] H<<D 00000000: 4C 6F 67 20 45 6D 70 74  79 0D 0A 43 4B 53 4D 3A  Log Empty..CKSM:
[ 60] H<<D 00000010: 30 30 30 30 30 33 36 38  0D 0A 43 4D 44 20 4F 4B  00000368..CMD OK
[ 60] H<<D 00000020: 0D 0A                                             .. 

[ 21] H>>D 00000000: 24 73 6E 3F                                       $sn? 

[ 60] H<<D 00000000: 4A 43 4D 56 30 32 31 2D  54 30 38 35 35 0D 0A 43  JCMV021-T0855..C
[ 60] H<<D 00000010: 4B 53 4D 3A 30 30 30 30  30 33 32 44 0D 0A 43 4D  KSM:0000032D..CM
[ 60] H<<D 00000020: 44 20 4F 4B 0D 0A                                 D OK.. 

[ 21] H>>D 00000000: 24 73 77 76 65 72 3F                              $swver? 

[ 60] H<<D 00000000: 32 2E 31 2E 32 0D 0A 43  4B 53 4D 3A 30 30 30 30  2.1.2..CKSM:0000
[ 60] H<<D 00000010: 30 31 30 38 0D 0A 43 4D  44 20 4F 4B 0D 0A        0108..CMD OK..

My best guess on why it’s asking again for serial number and software version, is that the data returned during the handshake is only used to select which “driver” implementation to use, while this is used to actually fill in the descriptor to show to the user.

If I look at the capture of the same actions with a Libre 2 system, the initialization is not quite the same:

[ 05] H>>D 00000000: 

[ 06] H<<D 00000000: 4D 41 47 5A 31 39 32 2D  4A 34 35 35 38 00        MAGZ192-J4558. 

[ 14] H>>D 00000000: 11                                                . 

[ 33] H<<D 00000000: 16 B1 79 F0 A1 D8 9C 6D  69 71 D9 1A C0 1A BC 7E  ..y....miq.....~ 

[ 14] H>>D 00000000: 17 6C C8 40 58 5B 3E 08  A5 40 7A C0 FE 35 91 66  .l.@X[>..@z..5.f
[ 14] H>>D 00000010: 2E 01 37 88 37 F5 94 71  79 BB                    ..7.7..qy. 

[ 33] H<<D 00000000: 18 C5 F6 DF 51 18 AB 93  9C 39 89 AC 01 DF 32 F0  ....Q....9....2.
[ 33] H<<D 00000010: 63 A8 80 99 54 4A 52 E8  96 3B 1B 44 E4 2A 6C 61  c...TJR..;.D.*la
[ 33] H<<D 00000020: 00 20                                             .  

[ 04] H>>D 00000000: 

[ 0d] H>>D 00000000: 00 00 00 02                                       .... 

[ 34] H<<D 00000000: 16                                                . 

[ 05] H>>D 00000000: 

[ 15] H>>D 00000000: 

[ 06] H<<D 00000000: 4D 41 47 5A 31 39 32 2D  4A 34 35 35 38 00        MAGZ192-J4558. 

[ 35] H<<D 00000000: 31 2E 30 2E 31 32 00                              1.0.12. 

[ 01] H>>D 00000000: 

[ 71] H<<D 00000000: 01                                                . 

[x21] H>>D 00000000: 66 C2 59 40 42 A5 09 07  28 45 34 F2 FB 2E EC B2  f.Y@B...(E4.....
[x21] H>>D 00000010: A0 BB 61 8D E9 EE 41 3E  FC 24 AD 61 FB F6 63 34  ..a...A>.$.a..c4
[x21] H>>D 00000020: 7B 7C 15 DB 93 EA 68 9F  9A A4 1E 2E 0E DE 8E A1  {|....h.........
[x21] H>>D 00000030: D6 A2 EA 53 45 2F A8 00  00 00 00 17 CF 84 64     ...SE/........d 

[x60] H<<D 00000000: 7D C1 67 28 0E 31 48 08  2C 99 88 04 DD E1 75 77  }.g(.1H.,.....uw
[x60] H<<D 00000010: 34 5A 88 CA 1F 6D 98 FD  79 42 D3 F2 4A FB C4 E8  4Z...m..yB..J...
[x60] H<<D 00000020: 75 C0 92 D5 92 CF BF 1D  F1 25 6A 78 7A F7 CE 70  u........%jxz..p
[x60] H<<D 00000030: C2 0F B9 A2 86 68 AA 00  00 00 00 F9 DE 0A AA     .....h......... 

[x0a] H>>D 00000000: 9B CA 7A AF 42 22 C6 F2  8F CA 0E 58 3F 43 9C AB  ..z.B".....X?C..
[x0a] H>>D 00000010: C7 4D 86 DF ED 07 ED F4  0B 99 D8 87 18 B5 8F 76  .M.............v
[x0a] H>>D 00000020: 69 50 4F 6C CE 86 CF E1  6D 9C A1 55 78 E0 AF DE  iPOl....m..Ux...
[x0a] H>>D 00000030: 80 C6 A0 51 38 32 8D 01  00 00 00 62 F3 67 2E     ...Q82.....b.g. 

[ 0c] H<<D 00000000: 01 00 18 00                                       .... 

[x0b] H<<D 00000000: 80 37 B7 71 7F 38 55 56  93 AC 89 65 11 F6 7F E6  .7.q.8UV...e....
[x0b] H<<D 00000010: 31 03 3E 15 48 7A 31 CC  24 AD 02 7A 09 62 FF 9C  1.>.Hz1.$..z.b..
[x0b] H<<D 00000020: D4 94 02 C9 5F FF F2 7B  3B AC F0 F7 99 1A 31 5A  ...._..{;.....1Z
[x0b] H<<D 00000030: 00 B8 7B B7 CD 4D D4 01  00 00 00 E2 D4 F1 13     ..{..M.........

The 0x14/0x33 command/response are new — and they clearly are used to set up the encryption. Indeed, trying to send out a text command without having issued these commands has the reader respond with a 0x33 reply that I interpret as a “missing encryption” error.

But you can also see that there’s a very similar structure to the commands: after the initialization, there’s an (encrypted) text command (0x21) and response (0x60), then there’s an encrypted binary command, and more encrypted binary responses. Funnily enough, that 0x0c response is not encrypted, and the sequence of responses of the same type is very similar between the Libre 1 and Libre 2 captures as well.

The similarities don’t stop here. Let’s look at the end of the capture:

[x0b] H<<D 00000000: A3 F6 2E 9D 4E 13 68 EB  7E 37 72 97 6C F9 7B D6  ....N.h.~7r.l.{.
[x0b] H<<D 00000010: 1F 7B FB 6A 15 A8 F9 5F  BD EC 87 BC CF 5E 16 96  .{.j..._.....^..
[x0b] H<<D 00000020: EB E7 D8 EC EF B5 00 D0  18 69 D5 48 B1 D0 06 A6  .........i.H....
[x0b] H<<D 00000030: 30 1E BB 9B 04 AC 93 DE  00 00 00 B6 A2 4D 23     0............M# 

[x21] H>>D 00000000: CB A5 D7 4A 6C 3A 44 AC  D7 14 47 16 15 40 15 12  ...Jl:D...G..@..
[x21] H>>D 00000010: 8B 7C AF 15 F1 28 D1 BE  5F 38 5A 4E ED 86 7D 20  .|...(.._8ZN..} 
[x21] H>>D 00000020: 1C BA 14 6F C9 05 BD 56  63 FB 3B 2C EC 9E 3B 03  ...o...Vc.;,..;.
[x21] H>>D 00000030: 50 B1 B4 D0 F6 02 92 14  00 00 00 CF FA C2 74     P.............t 

[ 0d] H>>D 00000000: DE 13 00 00                                       .... 

[x60] H<<D 00000000: CE 96 6D CD 86 27 B4 AC  D9 46 88 90 C0 E7 DB 4A  ..m..'...F.....J
[x60] H<<D 00000010: 8D CC 8E AA 5F 1B B6 11  4E A0 2B 08 C0 01 D5 D3  ...._...N.+.....
[x60] H<<D 00000020: 7A E9 8B C2 46 4C 42 B8  0C D7 52 FA E0 8F 58 32  z...FLB...R...X2
[x60] H<<D 00000030: DE 6C 71 3F BE 4E 9A DF  00 00 00 7E 38 C6 DB     .lq?.N.....~8.. 

[x60] H<<D 00000000: 11 06 1C D2 5A AC 1D 7E  E3 4C 68 B2 83 73 DF 47  ....Z..~.Lh..s.G
[x60] H<<D 00000010: 86 05 4E 81 99 EC 29 EA  D8 79 BA 26 1B 13 98 D8  ..N...)..y.&....
[x60] H<<D 00000020: 2D FA 49 4A DF DD F9 5E  2D 47 29 AB AE 0D 52 77  -.IJ...^-G)...Rw
[x60] H<<D 00000030: 2E EB 42 EC 7E CF BB E0  00 00 00 FE D4 DC 7E     ..B.~.........~ 

… Yeah many more encrypted messages …

[x60] H<<D 00000000: 53 FE E5 56 01 BB C2 A7  67 3E A6 AB DB 8E B7 13  S..V....g>......
[x60] H<<D 00000010: 6D F7 80 5C 06 23 09 3E  49 B4 A7 8B D3 61 92 C9  m..\.#.>I....a..
[x60] H<<D 00000020: 72 1D 5A 04 AE E3 3E 05  2E 1B C7 7C 42 2D F8 42  r.Z...>....|B-.B
[x60] H<<D 00000030: 37 88 7E 16 D9 34 8B E9  00 00 00 11 EE 42 05     7.~..4.......B. 

[x21] H>>D 00000000: 01 84 3F 02 36 1E A6 82  E2 C5 BF C2 40 78 B9 CD  ..?.6.......@x..
[x21] H>>D 00000010: E9 55 17 BE E9 16 8A 52  D2 D9 85 69 E4 D5 96 7A  .U.....R...i...z
[x21] H>>D 00000020: 55 6D DF 2E AF 96 36 53  64 C5 C7 D1 B6 6F 1A 1A  Um....6Sd....o..
[x21] H>>D 00000030: 4F 2F 25 FF 58 F4 EE 15  00 00 00 F6 9A 52 64     O/%.X........Rd 

[x60] H<<D 00000000: 19 F4 D4 F0 66 11 E3 CE  47 DE 82 87 22 48 3C 8D  ....f...G..."H<.
[x60] H<<D 00000010: BA 2D C0 37 12 25 CD AB  3A 58 C2 C4 01 88 60 21  .-.7.%..:X....`!
[x60] H<<D 00000020: 15 1E D1 EE F2 90 36 CA  B0 93 92 34 60 F5 89 E0  ......6....4`...
[x60] H<<D 00000030: 64 3C 20 39 BF 4C 98 EA  00 00 00 A1 CE C5 61     d< 9.L........a 

[x21] H>>D 00000000: D5 89 18 22 97 34 CB 6E  76 C5 5A 23 48 F4 5E C6  ...".4.nv.Z#H.^.
[x21] H>>D 00000010: 0E 11 0E C9 51 BD 40 D7  81 4A DF 8A 0B EF 28 82  ....Q.@..J....(.
[x21] H>>D 00000020: 1F 14 47 BC B8 B8 FA 44  59 7A 86 14 14 4B D7 0F  ..G....DYz...K..
[x21] H>>D 00000030: 37 48 CC 1F C5 A2 9E 16  00 00 00 00 A3 EE 69     7H............i 

[x60] H<<D 00000000: 62 33 4B 90 3B 68 3A D1  01 B1 15 4C 48 A1 6E 20  b3K.;h:....LH.n 
[x60] H<<D 00000010: 12 6F BC D5 50 33 9E C3  CC 35 4E C8 46 81 3E 6B  .o..P3...5N.F.>k
[x60] H<<D 00000020: 96 17 DF D5 8C 22 5C 3A  B7 52 C2 D9 37 71 B7 E2  ....."\:.R..7q..
[x60] H<<D 00000030: 5F C4 88 81 2A 91 65 EB  00 00 00 69 E2 A8 DE     _...*.e....i...

These are once again text commands. In particular one of them gets a response that is long enough to span multiple encrypted text responses (0x60). Given that the $patch? command on the Libre 1 suggested it’s a multirecord command, it might be that the Libre 2 actually has a long list of patches.

So my best guess of this is that, aside for the encryption, the Libre 2 and Libre 1 systems are actually pretty much the same. I’m expecting that the only thing between us and being able to download the data out of a Libre 2 system is to figure out the encryption scheme and whether we need to extract keys to be able to do so. In the latter case that is something we should proceed carefully with, because it’s probably going to be the way Abbott is going to enforce their DMCA requests.

What do we know about the encryption setup, then? Well, I had a theory, but then it got completely trashed. I still got some guesses that for now appear solid.

First of all, the new 0x14/0x33 command/reply: this is called multiple time by the software, and the reader uses the 0x33 response to tell you either the encryption is missing or wrong, so I’m assuming these commands are encryption related. But since there’s more than one meaning for these commands, it looks like the first byte for each of these selects a “sub-command”.

The 0x14,0x11 command appears to be the starting point for the encryption; the device responds with what appears to be 15 random bytes. Not 16! The first byte again appears to be a “typing” specification and is always 0x16. You could say that the 0x14,0x11 command gets a 0x33,0x16 response. In the first three captures I got from the software, the device actually sent exactly the same bytes. Then it started giving a different response for each time I called it. So I guess it might be some type of random value, that needs some entropy to be re-generated. Maybe it’s a nonce for the encryption?

The software then sends a 0x14,0x17 command, which at first seemed to have a number of constant bytes in positions, but now I’m not so sure. I guess I need to compare more captures for that to be the case. But because of the length, there’s at most 25 bytes that are sent to the device.

The 0x33,0x18 response comes back, and it includes 31 bytes, but the last two appear to be constant.

Also if I compare the three captures, two that received the same 0x33,0x16 response, and one that didn’t, there are many identical bytes between the two with the same response (but not all of them!), and very few with the third one. So it sounds like either this is a challenge-response that uses the provided nonces, or it actually uses that value to do the key derivation.

If you’re interested in trying to figure out the possible encryption behind this, the three captures are available on GitHub. And if you find anything else that you want to share with the rest of the people looking at this, please let us know.

Where did the discussion move to?

The oldest post you’ll find on this blog is from nearly sixteen years ago, although it’s technically a “recovered” post that came from a very old Blogspot account I used when I was in high school. The actual blog that people started following is probably fourteen years old, when Planet Gentoo started and I started writing about my development there. While this is nowhere as impressive as Scalzi’s, it’s still quite an achievement in 2020, when a lot of people appear to have moved to Medium posts or Twitter threads.

Sixteen years are an eternity in Internet terms, and that means the blog has gone through a number of different trends, from the silly quizzes to the first copy-and-paste list memes, from trackbacks to the anti-spam fights. But the one trend that has been steady over the past six years (or so) is the mistreatment of comments. I guess this went together with the whole trend of toxic comments increasing, and the (not wrong) adage of “don’t read the comments”, but it’s something that saddened me before, and that saddens me today.

First of all, the lack of comments feels, to me, like a lack of engagement. While I don’t quite write with the intention of pleasing others, I used to have meaningful conversations with readers of the blog in the past — whether it was about correcting my misunderstanding of things I have no experience with, or asking follow up questions that could become more blog posts for other to find.

Right now, while I know there’s a few readers of the blog out there, it feels very impersonal. A few people might reply to the Tweet that linked to the new post, and maybe one or two might leave a comment on LinkedIn, but that’s usually where the engagement ends for me, most of the time. Exception happen, including my more recent post on zero-waste, but even those are few and far between nowadays. And not completely unexpectedly, I don’t think anyone is paying attention to the blog’s Facebook page.

It’s not just the big social media aggregators, such as Reddit and Hacker News, that cause me these annoyances. Websites like Boing Boing, which Wikipedia still calls a “group blog”, or Bored Panda, and all their ilks, appear to mostly be gathering posts from other people and “resharing” them, nowadays. On the bright side of the spectrum, some of these sites at least appear to add their own commentary on the original content, but in many other cases I have seen them reposting the “eye catchy” part of the original content (photo, diagram, infographic, video) without the detailed explanations, and sometimes making it hard to even find the original credit.

You can imagine that it is not a complete coincidence that I’m complaining about this after having had to write a full-on commentary due to Boing Boing using extremely alarmist tones around a piece of news that, in my view, barely should have been notable. Somehow it seems news around diabetes and glucometers have this effect on people — you may remember I was already annoyed when Hackaday was tipped about my project, and decided to bundle it with an (unsafe!) do-it-yourself glucometer project that got the most of the comments on their own post.

I guess this ends up sounding a lot like an old man shouting at clouds — but I also still think that discussing ideas, posts, opinions with the creators are worth doing, particularly if the creators have the open mind of listening to critique of their mistakes — and, most importantly, the “capacitance” to send abuse away quickly. Because yeah, comments became toxic a long time ago, and I can’t blame those who prefer not to even bother with comments in the first place, despite disliking it myself.

To conclude, if you have anything to discuss or suggest me, please do get in touch. It’s actually a good feeling to know that people care.

Unnecessary, but required

In the past year, I’ve hard to learn quite a few different lessons, some harder than others, some more gratifying than others. One of the main (but far from the only) source of these lessons was learning to live with someone else — save for my mother, and a few months with Luca, I have never really shared an apartment, a flat, or a house with someone else for more than a few days. But now that I’m happily married, there’s no going back to solitude. And it’s a feeling I’m really happy about, despite the eventual challenges that this has brought to both of us.

One of the differences that we realised early on is that we have different tolerances to chaos and trinkets. I’m not particularly organised when it comes to sorting out my stuff, but I’m also not a total slob — but I don’t mind having items spread across three rooms, and I was not particularly well known for having ironed t-shirts. My wife’s much less… chaotic, but at the same time has a fairly short patience for technology for the sake of technology.

This pretty much makes a dent in the amount of random gadgets I end up buying for the sake of trying out, because they might just end up not being used, or even not being welcome if they somehow get in the way. I think my most impressive achievement has been making her accept we have an electric cheese grater. I’m still trying to convince her it’s a good idea for me to disassemble the battery charger to replace the current plug-in adapter with an micro-USB port. Which is honestly not necessary at all: the plug is an AC-DC adapter, europlug with one of those europlug-to-british screw-in adapters, which means if we decide to leave London for the Continent, we won’t be needing to replace it — it would only become an issue if we moved to a different part of the world, and we can address it then.

But at the same time, this is the type of modification that in my eyes is… well, required. Why would I not make my electric cheese grater into an USB-powered electric cheese grater?

This reminded me of what Adam Savage (of Mythbuster fame) says in his biography Every Tool’s A Hammer (which, incidentally, is an awesome read that I would recommend everyone who has even a passing interest in creating stuff):

I often describe myself as a serial skill collector. I’ve had so many different jobs over my lifetime […] that my virtual tool chest is overflowing. Still I love learning new ways of thinking and organizing, new technqiues, new ways of solving old problems. […] The skills I have, all of them, are simply arrows in my mental quiver, tools in my problem-solving tool chest, to achieve that thing. […] And I learned each of them specifically for that reason. […] Eventually, […] I came to realise this was the ONLY way I could successfully learn a skill—by doing something with it, by applying it in my real world.

Adam Savage, Every Tool’s A Hammer

This is pretty much my life. I have pretty clearly failed at learning things “academically”, lasting only a few weeks at University of Venice, and instead building up my knowledge by working on different projects, both opensource and for customers, and by trying things out for myself. This has been a blessing and a curse at same time: while it meant that I have been collecting a bunch of skills, just like Adam is saying above, for the most part I have superficial skills: I’ve only rarely had to go deep-dive into a technology or a problem in my dayjob, and the amount of time I have to spend on side projects has been fairly low, and shrinking.

Long are the the days gone when I could sit down to write a stupid IRC bot in Qt, just because I could, and not just for the lack of time. It’s also because, for the most part, I keep telling myself it’s a bad idea to work on something low level, when someone else already did it better than I could possibly do — which is likely true, but it fails to meet my requirement to add the skill to my repertoire. And that’s by itself a career-limiting move, comparable to to the bubble problem.

With these issues in mind, I’m definitely glad my wife is understanding on why I sometimes spend money, time, effort (or most likely, all three) just to get something done because I want to, and not because there’s much need for it. It’s unnecessary, but required for me to keep up to scratch. And being able to do that, without upsetting my partner despite the chaos it creates, is a significant privilege.

As well as privilege is being able to afford the time, space, and money for all these projects. I think this is, for the most part, something that is not quite clear out there yet: being able to contribute to opensource, to write up tips and tricks, to document how to do things are privileges. And I think it’s important to share this privilege, even in form of tips, tricks, videos, and blogs — which is why this blog is still existing, and even with ever-shortening spare time I try to write updates.

Whether it is Bigclive on YouTube, with sometimes off-colour comments that make me uncomfortable, or Adam Savage’s own Tested, that can rely on a real, professional shop, or Micah’s most awesome electronics reverse engineering channel, or Foone’s Twitter feed, I am very glad for those who do their best to share knowledge — and I don’t really need to know why they are doing it. Even when it doesn’t really help me directly (because I can’t learn something if I don’t try myself), I know it can help someone else. Or inspire someone else (or in some cases, me) to go and try something, that will make them learn more.