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Cake day: July 9th, 2023

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  • notabot@lemm.eetoLinux@lemmy.mlVPS encryption
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    2 months ago

    It depends what you want to do with it. If it’s just for storing files/backups then encrypt them before uploading and make sure the key never goes anywhere near the VPS. If it’s for serving up something like a simple website, you probably care more about data integrity than exfiltration, so make sure you have the security, including selinux or equivalent, locked down, and regularly run integrity checks. If it’s for running something interactive, or where data will be generated or downloaded to the machine, you’re out of luck, there’s no even theoretical way of securing that against an adversary with that much access.


  • I agree that them having users’ phone numbers isn’t ideal. There are other identifiers they could use that would work just as well. However, both the client and server are open source, so you can build, at least the client, yourself. If you can content yourself that it does not leak your ID when sending messages, then you don’t need to trust the server as it does not have the information to build a graph of your contacts. Sealed sender seems to have been announced in 2018, so it’s had time to be tested.

    Don’t get me wrong, the fact they require a phone number at all is a huge concern, and the reason I don’t really use it much, but the concern you initially stated was addressed years ago and you can build the client yourself to validate that.


  • You’re correct that if you use the system the way it used to work they can trivially build that connection, but (and I know this is a big assumption) if it does now work the way they say it does, they do not have the information to do that any more as the client doesn’t actually authenticate to the server to send a message. Yes, with some network tracing they could probably still work out that you’re the same client that did login to read messages, and that’s a certainly a concern. I would prefer to see a messaging app that uses cryptographic keys as the only identifiers, and uses different keys for different contact pairs, but given their general architecture it seems they’ve tried to deal with the issue.

    Assuming that you want to use a publicly accessible messaging app, do you have any ideas about how it should be architected? The biggest issue I see is that the client runs on your phone, and unless you’ve compiled it yourself, you can’t know what it’s actually doing.



  • Whilst I absolutely agree it’s correct to be skeptical about it, the ‘sealed sender’ process means they don’t actually know which account sent the message, just which account it should be delivered to. Your client doesn’t even authenticate to send the message.

    Now, I’m just going on what they’ve published on the system, so either I could be completely wrong, or they could be being misleading, but it does look like they’ve tried to address the very issue you’ve been pointing out. Obviously it’d be better if they didn’t have your phone number at all, but this does seem to decouple it in a way that means they can’t build a connection graph.



  • It’s a non-starter for me because I sync my notes, and sometimes a subset of my notes, to multiple devices and multiple programs. For instance, I might use Obsidian, Vim and tasks.md to access the same repository, with all the documents synced between my desktop and server, and a subset synced to my phone. I also have various scripts to capture data from other sources and write it out as markdown files. Trying to sync all of this to a database that is then further synced around seems overly complicated to say the least, and would basically just be using Trillium as a file store, which I’ve already got.

    I’ve also be burnt by various export/import systems either losing information or storing it in a incompatible way.




  • It’s been years since I had to admin Windows servers, but I was quite impressed with the number of MS products where the install and configuration tools would output the Powershell commands to carry out the changes you’d asked for. It made it quite a lot easier to automate. I’d love to see that paradigm catch on more widely, with the GUI and CLI having the same functionality and the GUI giving you the commands to run.


  • I’ve found HSBC to be ok using Firefox on Linux. I don’t know if they have integrations with any accounting software, but the web access works well, and you can export your transactions for processing locally.

    ETA: I’ve run small business accounting on Gnucash, I found the learning curve a bit steep, but once you ‘get it’ it’s handy.


  • Sorry for the slow reply, life occurred.

    I think I understand where you’re coming from with the desired to be productive and not reinstall. I think I’ve been there too! One thing that I can suggest, if you do have the time, is to learn a system like Ansible and use it to setup and configure your machine. The discipline of keeping all of the config as source rather than making ad-hoc changes reduces the chance of thinking you’ll make just one little change and breaking something, and, if something does go wrong, you can get back to your working configuration quickly.

    Bearing in mind that there really isn’t anything you can do to stop yourself if you’re really determined to not lose the data, because if you can read it at any time you can back it up, the closest you are likely to come is something like creating new key with GPG then using the TPM to wrap your secret key and deleting the original. That way the key is only usable on that specific machine. Then use the key-pair to encrypt your ‘guard’ files. You can still decrypt them because you have the wrapped secret keys and you’re on the same machine, but if you wipe the drive and lose those keys the data is gone. The TPM wrapping prevents you from taking the keys to a different machine to decrypt your data.

    There’s an article with some examples here,

    Having said all of that, this still doesn’t help if you just clone the disk as all of the data, including the wrapped key and the encrypted files will be cloned. The one difference there is that the serial number of the hard drive will be different. Maybe you could use that, combined with a passphrase as the passphrase for your GPG key, but we’re getting into pretty esoteric territory here. So you could generate a secret key with a command like:

    ( lsblk -dno SERIAL /dev/sdb ; zenity --title "Enter decrypt password" --password) | sha1sum | cut -c1-40
    

    Where /dev/sdb is the device your root partition is on. zenity is a handy utility for displaying dialogs, there are others available. In this use it just prompts for a passsword. We then concatenate the drive serial number from lsblk with the password you entered and hash the result. The hashing is really only a convenient way to mix the two without worrying about the newline lsblk spits out. Don’t record the result of this command, but use it to set the passphrase on your new GPG key. Wrapping the secret key in the manner the article above suggests is a nice extra step to make it harder to move the drive to another machine or mess around in that sort of way, but not strictly necessary as that wasn’t in the scope of your original question.

    Now you can encrypt your file with: gpg -e -r <your key name> <your file>'. That will produce an encrypted version of <your file>called<your file>.gpg. To decrypt the file you can get gpg` to use the hashing command from above to get the passphrase with something like:

    gpg -d --pinentry-mode=loopback --batch --passphrase-fd 3 <your file>.gpg 3< <( ( lsblk -dno SERIAL /dev/sdb ; zenity --title "Enter decrypt password" --password) | sha1sum | cut -c1-40 )
    

    Once you’ve tested that you can decrypt the file successfully you can remove the original, plaintext, file. Your data is now encrypted with a key that is secured with a passphrase made of a string you know and the serial number of your disk and optionally wrapped with a key from the TPM that is tied to your physical machine. If you change the disk or the machine the data is irretrievable (ignoring the caveats discussed above). I think that’s about as close to your original goal as you can get. It’s rough around the edges, and I’m not sure I’d trust my data to it, but I believe it’ll work. If you do something like this, please test it thoroughly, I can’t guarantee it!


  • This seems like a very complicated way to achieve your goal! It sounds like sitting yourself down and giving you a stern talking to might be a beter aporoach.

    Having said that, if you have these very important files that you don’t want to lose, please make sure they’re backed up somewhere off of your machine. Storage fails, and it’s a horrible feeling losing something important. Unfortunately doing so would defeat the approach you’re thinking of.

    This might be a case of needing to reframe the question to get to the cause of the issue, and then solve that. So, why do you want to make it hard to reinstall your machine? Is it the amount of time you spend on it, the chance of screwing it up, needing it working, has it become a compulsion or something else? Maybe if we can get to the root of the issue we can find a solution.

    With regard to TPM, it’s basically just a key store, so you can use it fir anything really, althought it’s normally used by generating a TPM key and using it to encrypt the key that’s actually used to encrypt your data, storing the encrypted key with the OS. Just reinstalling won’t wipe the TPM, but unless you made an effort to save the encrypted key it’ll be gone. Given your problem statement above it just adds to the data you’d need to save, which isn’t helpful.


  • Ok, I’m still not clear on exactly what you’re trying to achieve as I can’t quite see the connection between somehow preventing certain files being duplicated when cloning the disk and preventing yourself from reinstalling the system.

    Bear in mind that reinstalling the system would replace all of the OS, so there’s no way to leave counter-measures there, and the disk itself can’t do anything to your data, even if it could detect a clone operation.

    If what you’re trying to protect against is someone who knows everything you do accessing your data, you could look to use TPM to store the encryption key for your FDE. That way you don’t know the password, it’s stored encrypted with a secret key that is, in turn, stored and protected by your CPU. That way a disk clone couldn’t be used on any hardware except your specific machine.


  • Nothing can prevent a disk clone cloning the data, and there’s no way to make something happen when a disk is cloned as you’re not in control of the process.

    If you wish to mask the existence of the files, use either full disk encryption, in which case cloning the disk doesn’t reveal the existence of the files without the decrypt password, or use a file based encrypted partition such as veracrypt in which case the cloner would just see a single encrypted blob rather than your file names.

    Ultimately encrypting the files with gpg means they have already effectively ‘destroyed or corrupted’ themselves when cloned. If you don’t want to reveal the filenames, just call them something else.

    If you could be a bit more specific about your threat model people may have better ideas to help.



  • While I agree with most people here that finding a keyboard and screen would be the easiest option, you do have a couple of other options:

    • Use a preseed file A preseed lets the installer run completely automatically, without user intervention. Get it to install a basic system with SSH and take it from there. You’ll want to test the install in a VM, where you can see what’s going on before letting it run on the real server. More information here: https://wiki.debian.org/DebianInstaller/Preseed

    • Boot from a live image with SSH Take a look at https://wiki.debian.org/LiveCD in particular ‘Debian Live’. It looks like ssh is included, but you’d want to check the service comes up on boot. You can then SSH to the machine and install to the harddrive that way. Again, test on a VM until you know you have the image working, and know how to run the install, then write it to a USB key and boot the tsrget server from that.

    This all assumes the target server has USB or CD at the top of its boot order. If it doesn’t you’ll have to change that first, either with a keyboard and screen, or via a remote management interface sych as IPMI.




  • I’m not disputing that he doesn’t think the issues are major, as I said, he’s usually pretty ambivalent about what runs on the kernel, so they’re not issues he cares about. On the flip side, I do care what is running because I have to manage and support it.

    I do wonder if we’re talking at cross purposes though. You seem to mostly be talking about the systemd init system, I’m mostly talking about all the other bits it, as a sort of umbrella project, tries to encompass. I don’t much like the init system, I prefer to be able to explicitly set the ordering of the steps, rather than having them inferred, and I prefer shell script that I can test to unit files, but it mostly works ok. So does every other init system though, so it’s not a selling point.

    As I said, the big problem is around how they’ve tried to do everything, much of it less well than what they’re replacing. Yes, you can build a system that uses systemd-init and none of the other components, but that still drags in a load of other dependencies, so you might as well use a different init that’s smaller and cleaner.

    We came close to the ‘systemd apocalypse’ recently, when distros hooked the systemd library into openssh without understanding just how bloated it is and how many poorly monitored dependencies it brought in. It was just luck that the right person spotted a slight change in timing and investigated.

    Ultimately I suppose it comes down to the level you interact with your systems at. If you just want to install your OS, a few packages they directly support and let it get on with it, then you probably neither know nor care that you run systemd, and that’s great. On the other hand, in my experience, when you try to push the system past that and do anything more customized you start running into the sharp edges and misfeatures on the various systemd components.