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Cake day: June 2nd, 2023

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  • It’s not directly related to the torrent or its content no. It’s more related to the potential bugs in Transmission that might be exploited to propagate viruses.

    Since Transmission has to exchange data with un-trusted parties, before knowing whether the data is relevant to the torrent you are downloading, anyone could exploit bugs that exist in the parsing of these messages.

    So running Transmission as a dedicated user limits what an attacker may have access to once they take control of Transmission through the exploit of known or unknown bugs.

    Obviously, this user need to have many restriction in place as to prevent the attacker from installing malware permanently on the machine. And when you copy over data that has been downloaded by Transmission, you’d have to make sure it has not been tampered with by the attacker in an attempt to get access to the data available to your real account.

    If you just use transmission occasionally, not on a server, I would not bother with it. Either use the flatpak version for some sandboxing and similar security guarantees as having a dedicated user running Transmission, or use an up to date version (the one from your distro should be fine) and don’t leave it running when you do not need to.


  • the common practice is to relax the dependencies

    I found this a bit disturbing

    I find that funny that, since this is rust, this is now an issue.

    I have not dwelved in packaging in a long while, but I remember that this was already the case for C programs. You need to link against libfoo? It better work with the one the distribution ship with. What do you mean you have not tested all distributions? You better have some tests to catch those elusive ABI/API breakage. And then, you have to rely on user reported errors to figure out that there is an issue.

    On one hand, the package maintainer tend to take full ownership and will investigate issues that look like integration issue themselves. On the other hand, your program is in a buggy or non-working state until that’s sorted.

    And the usual solutions are frown upon. Vendoring the dependencies or static linking? Are you crazy? You’re not the one paying for bandwidth and storage. Which is a valid concern, but that just mean we reached a stalemate.

    Which is now being broken by

    • slower moving C/C++ projects (though the newer C++ standards did some waves a few years back) which means that even Debian is likely to have a “recent” enough version of your dependencies.
    • flatpack and the likes, which are vendoring everything and the kitchen sink
    • newer languages that static link by default (and some distributions being OK with it)

    In other words, we never figured out a proper solution for C projects that will link with a different minor than the one the developer tested.

    Well, /rant I guess. The point I’m raising does not seem to be the only one, and maybe far from the main one, for which bcachefs-tools is now orphaned. But I’ve seen very dubious arguments to try and push back against rust adoption. I feel like people have forgotten where we came from. And while there is no reason to go back per say, any new language that integrate this deep into the system will face similar challenges.


  • I don’t think that’s the issue. As said in the article, the researchers found the flaw by reading the architecture documentation. So the flaw is in the design of the API the operating system uses to configure the CPU and related resources. This API is public (though not open source) as to allow operating system vendors to do their job. It usually comes with examples and pseudo code on how some operations work. Here is an example (PDF).

    Knowing how this feature is actually implemented in hardware (if the hardware was open source) would not have helped much. I would argue you are one level too low to properly understand the consequences of the implementation.

    By the vague description in the article it actually looks like a meltdown or specter like issue where some code gets executed with the inappropriate privileges. Such issues are inherent to complex designs and no amount of open-source will save you there. We need a cultural and maybe a paradigm shift on how we design CPU to fully address those issues.



  • making the place less equal, more of a broadcast medium, and less accessible to unconnected individuals and small groups.

    I do not think it is a very good analogy. I do not see how this would turn into a broadcast medium. Though I do agree it can feel less accessible and there is a risk of building echo chambers.

    How does an instance get into one of these archipelagos if they use allowlists?

    By reaching out, I would say. It’s most likely a death sentence for one-persone instances. Which is not ideal. On the other hand, I’ve seen people managing their own instance give up on the idea when they realized how little control they have over what gets replicated on their instance and how much work is required to moderate replies and such. In short, the tooling is not quite there.


  • I think both models (i.e. allowlist/blocklist) have their own perks and drawbacks and are all necessary for a healthy and enjoyable internet.

    I would tend to agree. I think both methods have their merits. Though ideally I’d rather have most instances use a blocklist model. This is less cumbersome to the average user and this achieves (in my opinion) one of fediverse goal of having an online identity not tied to an instance, an online identity you can easily migrate (including comments, follow, DMs, …) if needed.

    But the blocklist model is too hard to maintain at this time. There are various initiative to try and make it work, such as fediseer, and it might be good enough for most. But I think it’s a trap we should not fall into. On the fediverse, “good enough for most” is not good enough.

    Now that people are fleeing to the Fediverse, we’re just gathering our tribe - and this is a natural phenomenon.

    I think there is indeed something of that effect going on as well, this is true. But I do not think this warrants a move to allowlist by itself.

    I think the move to allowlist is mandated by the fact that building a safe space for “minorities” is hard. The tools to alleviate issues such as harassment and bigotry are not sufficient at this time to keep those communities fully open.

    Which is a shame as I think the best way to fight those issues, as a society, is to have people express themselves and have healthy conversation on issues that are rarely brought up.

    But we are not entirely giving that up by moving to an archipelago model. It just means that individuals would have multiple accounts, on different archipelago. The downside is that it makes the fediverse less approachable to the average person.


  • I think the current technical limitations push us toward this archipelago model.

    The thing is, bigotry and racism, to name only two, will exist on any social media, any platform where anyone is free to post something. And since those are societal issue, I don’t think it is up to the fediverse to solve. Not all by itself by any means.

    What the fediverse can solve however, is to allow instances to protect themselves and their members from such phenomenon. And my limited understanding, as a simple user, is that’s it’s not possible right now. Not on lemmy nor on Mastodon, if I trust the recent communications around moderation and instance blocking. Not without resorting to allow list.

    This is annoying to admit because it goes against the spirit of the fediverse. But the archipelago model is the only sane solution short term IMO. And it will stay that way until the moderation tools make a leap and allow some way to share the load between instances and even between users.



  • Enable permissions for KMS capture.

    Warning

    Capture of most Wayland-based desktop environments will fail unless this step is performed.

    Note

    cap_sys_admin may as well be root, except you don’t need to be root to run it. It is necessary to allow Sunshine to use KMS capture.

    Enable

       sudo setcap cap_sys_admin+p $(readlink -f $(which sunshine))
    

    Disable (for Xorg/X11 only)

       sudo setcap -r $(readlink -f $(which sunshine))
    

    Their install instruction are pretty clear to me. The actual instruction is to run

    sudo setcap cap_sys_admin+p $(readlink -f $(which sunshine))

    This is vaguely equivalent to setting the setuid bit on programs such as sudo which allows you to run as root. Except that the program does not need to be owned by root. There are also some other subtleties, but as they say, it might as well be the same as running the program directly as root. For the exact details, see here: https://www.man7.org/linux/man-pages/man7/capabilities.7.html and look for CAP_SYS_ADMIN.

    In other words, the commands gives all powers to the binary. Which is why it can capture everything.

    Using KMS capture seems way overkill for the task I would say. But maybe the wayland protocol was not there yet when this came around or they need every bit of performance they can gain. Seeing the project description, I would guess on the later as a cloud provider would dedicate a machine per user and would then wipe and re-install between two sessions.



  • This looks like one of those wireguard based solution like tailscale or netbird though I’m not sure they are using it here. They all use a public relay used for NAT penetration as well as client discovery and in some instance, when NAT pen fails, traffic relay. From the usage, this seems to be the case here as well:

    Share the local Minecraft server:

    $ holesail --live 25565 --connector “holesailMCServer420”

    On other computer(s):

    $ holesail “holesailMCServer420”

    So this would register a “holesailMCServer420” on their relay server. The clients could then join this network just by knowing its name and the relay will help then reach the host of the Minecraft server. I’m just extrapolating from the above commands though. They could be using DHT for client discovery. But I expect they’d need some form of relay for NAT pen at the very least.

    As for exposing your local network securely, wireguard based solution allow you to change the routing table of the peers as well as the DNS server used to be able to assign domain name to IPs only reachable from within another local network. In this instance, it works very much like a VPN except that the connection to the VPN gateway is done through a P2P protocol rather than trough a service directly exposed to the internet.

    Though in the instance of holesail, I have heavy doubts about “securely” as no authentication seems required to join a network: you just need to know its name. And there is no indication that choosing a fully random name is enough.


  • On the topic of exposing sequence number in APIs, this has been a security issue in the past. Here is one I remember: https://www.reuters.com/article/us-cyber-travel-idUSKBN14G1I6/

    From the article:

    Two of the three big booking systems - Amadeus and Travelport - assign booking codes sequentially, making brute-force computer guesswork easier. Of the three, Amadeus, through its web portal CheckMyTrip, is especially vulnerable, Nohl said.

    The PNRs (flight booking code) have many more security issues, but at least nowadays, their sequential aspect should no longer be exposed.

    So that’s one more reason to be careful when exposing DB id in APIs, even if converted to a natural looking key or at least something easier to remember.




  • The main problem is that dynamic linking is hard. It is not just easier for the maintainers of the languages to ignore it, it removes an entire class of problems.

    Dynamic linking does not even reliably work with C++, an “old” language with decades of tooling and experience on the matter. You get into all kind of UB when interacting with a separate DSO, especially since there are minimal verification of the ABI compatibility when loading a dynamic library. So you have to wait for a crash to be certain you got it wrong. Unless you control the compilation of your dependencies, it’s fairly hard to be certain you won’t encounter dynamic linking related issues. At which point you realize that, if the license allows it, you’re better off static linking everything, including the C++ library itself: it makes it much more predictable, you’re not forcing an additional dependency on your users and most UB are now gone (especially the one about raising exception across DSO boundaries, which can happen behind your back, unless you control the compilation of all your dependencies…).

    That’s especially true if you are releasing a library where you do not know it’s runtime: it might be dynamically loaded via dlopen by a C++ binary that will load its own C++ library first, but some of your users use the version that is stuck on C++14 and your codebase is in C++23. This can be solved, by playing with LD_LIBRARY_PATH, but the application is already making use of it to load the C++ library it comes with instead of the one provided by the system (which only provides C++11 runtime), and it completely ignores the initial state of the environment variable (how could it do otherwise? It would have to guess the path to the libstdc++ is for a newer version and not the older one provided by the system). Now imagine the same issue with your own transitive dependency on top of that: it’s a nightmare.

    So dynamic linking never really worked, except maybe for C when you expect a single level of dependency, all provided by the system. And even then that’s mostly thanks to C simpler ABI and runtime.

    So I expect that is the main reason newer languages do not bother with dynamic linking: it introduces way too many issues. Look at your average rust program and how many version of a same dependency it loads, transitively. How would you solve that problem as to be able to load different versions when it matters but try first and foremost to load only one if possible? How would you be able to make the right call? By using semver? If nobody made any mistake why not, but you will rather be required to provide escape hatches that, much like LD_LIBRARY_PATH and LD_PRELOAD, will be misused. And by then, you only “solved” the simplest problem.

    Nowadays, based on how applications are delivered on Windows and OSX, and with the advent of docker, flatpack/snap and appimage, I do not see a way back to dynamic linking anytime soon. It’s just too complicated of a problem, especially as the number of dependency grows.



  • I’ve used scratch to introduce kids (6~10) to programming. It works quite well IMO. They had a laptop with windows. I recommend a touch screen if possible, especially for younger kids. Though at 8~12yo that should not be as much of an issue.

    I used it with the microbit from the BBC. While not required, a dedicated piece of hardware makes it much more interactive and fun, for a basic introduction. Basically, the microbit can be turned into a remote control for your characters in scratch for example.

    Though, kids get fond of the ability to create pre-programmed scenes. That are not very logic intensive, more like an animated movie. And since they can add their own drawings and voice, they can get very engaged on this sole basis. So the microbit is not required at all.

    Though if you want to use it, Microsoft has its own scratch for microbit that is more annoying to use IMO (you need to flash the program every time, which is not easy for younger kids that have trouble with the mouse), but it unlocks all the capabilities of the microbit for even more interactive applications. You can make them communicates through a basic protocol over 2.4GHz radio, control led strips or even robots for example (though the robots are far from cheap for what they are 😕).

    Both scratch and makecode (the links mentioned above) have plenty of resources if you want to get a lab going. Personally, I would set my expectation fairly low and plan for many additional small features that kids that are really interested could implement on their own. In my experience, some kids will not be interested at all, not until they see a feature they want to interact with at least. Others will try to see what they can do by themselves, before the lab even begin. But usually, the older they get, the less likely they are to experiment by themselves and they’d rather wait for instructions. Which is a shame, but that’s how it is I guess.

    Also, try to make sure they can continue their work from home. Scratch is available on many platforms (though makecode sucks on Android last time I checked) and is trivial to get up and running. That said, importing a project is another matter for kids barely familiar with computers, which is why I would distribute a document aimed at their parent to get them set up.


  • I feel like since Glassdoor has a job board, there is an obvious conflict of interest that cannot be solved and ultimately yields to the company review part to be mostly useless. If you browse through a few company profiles, some that offer jobs on Glassdoor (and reply to reviews) and some that do not, you will quickly see what I’m talking about.

    I mean, who is going to post job offers on a board that also list your company at <4 stars with plenty of mention of “bad company culture” and “horrendous working condition”?

    I also do not like how most of the would-be-intersting-info is gatekeep behind you sharing various info on your own employer. I mean, it seems to make sense on the surface, but with the above, the whole thing feels like a scam. Where both employers and employees get scammed.

    How does it compare to alternatives ? Well, LinkedIn is terrible, with abysmal search function, results completely irrelevant to your profile, and the same seems to be true for recruiters seeing how often I’m proposed jobs completely outside of my skillset.

    So I guess Glassdoor is a viable source of job offer, especially if you have already selected companies you’d like to work at and those companies do not have their own board. But take all reviews and comments with a huge grain of salt.


  • I disagree. The question is not really “should we give programmer more power at the cost of yet another UB” but more “should we grow the API and add another UB for the select few for whom it might matter”. When you consider choices made on other parts of the STL, such as std::unordered_map, then you realize the STL is not about being the most performant things around, but rather a collection of reliable tools covering basic usage for 80% of the user base.

    With that in mind, I am against adding yet another function, which has its pitfalls, for minimal benefits. Again, such a function would be made almost entirely obsolete by a safe function that works with iterators/generators of known sizes. So I see even less benefit in adding a function that will just become yet another liability down the line.


  • The benchmark looks off. The msvc one may be the only one vaguely reliable. I suspect clang and GCC were able to optimize the synthetic benchmark to a little more than a loop doing additions. At 96ns for 1000 iteration, you are looking at 10G iterations per seconds. Which can only be achieved by a loop of two instructions executing at 2 inst/s on a 5GHz processor. And you will not get a 5x just for removing a highly predictable branch.

    So yes, std::vector leaves performance on the table, but no more than 10~15% for trivial loops that are not that uncommon but are rarely a bottleneck.

    Then you have to ask yourself, is it worth it to add yet another function that can crash your program if misused just for that 10% in a situation where they might not even matter. I mean, I know, it’s c++, zero cost abstraction, yadi yada, but if you’re looking for consistent performance you should have moved away from the STL already. As this post shows, your STL vendor already has a huge impact on the performance, and there are widely available options to optimize specific cases.

    So I’d rather keep the STL fairly simple. Add one function to work well with generators/iterators that have a known size if you want, but adding unchecked versions of every insertion function of every STL container is not worth it IMO.


  • First of, especially in C, you should very carefully read the documentation of the functions you use. It then should be obvious to you you are currently misusing it on two accounts:

    • You are not checking for errors
    • You are assuming the presence of a \n that might never be there (this one leads to your unexpected behavior)

    The manual tells you it will insert a \0 at the end of what it reads within the limits of the buffer. So this \0 is what you will need to look for when determining the size of the input.

    If there is a \n, it will precede the \0. Just make sure the \0 is not at index 0 before trying to erase the \n. If there is no \n before the \0, you are in either of two cases (again, this is detailed in the documentation): the input is truncated (you did not read the full line, as in your unexpected behavior above) or you are reaching the end of the stream. Note that even if the stream ends with \n, you might need to issue an additional fgets to know you are at the end of the stream in which case a \0 will be placed as the first byte of your buffer.

    If you really want to handle input that exceeds your initial buffer, then you need to dynamically allocate one and grow it as needed. A well behaved program will have an upper limit to the size of the input anyway (and this is why you don’t use gets). So you will need a combination of malloc/realloc and string concatenation. That means you need to learn all the pitfalls of dynamic memory allocation in C and how to use valgrind. For the string concatenation, even though strcat should be OK in your case, I’d recommend against it.

    In order to use strcat properly you need to keep track of the usage of the dynamically allocated buffer by hand anyway because you want to know when you will attempt to store more bytes in the buffer than is currently allocated. And once you know the number of bytes stored in the buffer, copying over the bytes that fgets returns by hand is fairly trivial and has less pitfalls. This also circumvent one of the performance pitfall of strcat: it needs to find the \0 in the destination buffer for every call. So effectively, it can transform all by itself a trivial usecase such as yours, that one would expect to be linear in algorithmic complexity, to be of O(N^2) complexity.

    On a final note: fgets does not allow you to handle binary data properly because you wont be able to tell apart a legitimate \0 coming from your input from a \0 inserted by fgets. So you will need to use fread in this case. I actually recommend using fread instead of fgets because it directly returns the number of bytes read, no need to use strlen to guess it and it makes error handling easier. Though you’ll need to add the trailing \0 yourself.