If only more Linux programs followed sandboxing best practices...

94 comments

It's not fully sandboxed if it can write to my screen! That filthy app, writing stuff all over the place!
- Sandboxes have been converted into quarantine bomb shelters, for child safety
- Haskell programmers when you tell them the main function isn't pure
- That's why we have Wayland. :)

What if your app actually needs access to the internet?
- Or actually do anything useful? No network, no filesystem.. it's a hello world app isn't it..
  
  No filesystem access for a flatpak app just means it cant read host system files on its own, without user permission. You can still give it files or directories of files through the file explorer for the app to work with, just that it's much safer since it can only otherwise view files in its sandbox.
  
  There are portals: https://docs.flatpak.org/en/latest/desktop-integration.html#portals . they allow secure access to many features. Also any flatpak app still has access to a private app-specific filesystem, just not to the host.
  Doesn't work for all applications but for many sand boxing is possible without a loss of features.
  
  There's Obfuscate, an image redactor, and Metadata Cleaner which is self-descriptive. Both works properly without any filesystem access at all, because they use the file picker portal to ask the user for the files to be processed.
  
  Portal.
- Oh come on, what modern program actually needs to communicate or access the file system?
  
  Exactly all programs should be web based cloud subscription only. We don't want that filthy code on our rgb nvme drives
- Download the internet along with it!
  
  I'm self-hosting the entire internet. I hope you guys are enjoying yourselves.
  
  I remember in 1995-ish or something when I used the internet for the first time using the Netscape browser.... And I was asking a friend if he had tried all the web sites yet. Just got a weird look back.... :) I didn't know what the internet was back then at first.
- The app can then declare the network permission and it will still be marked as safe.

I like how the app name is blacked out so as not to dox the flathub app.
- Wouldn't want bad actors to find privacy respecting software.
- Sanboxed from prying eyes, it's completely safe.

What really needs to happen:
Flatpak packages should ask for every permission they need, and the user needs to approve every one of them.
Right now, we have this weird in-between state where some flatpak packages ship with limited permissions (like Bottles). That's because every permission the package asks for is immediately granted. The user doesn't get a chance to refuse these requests. This current model serves to make life more difficult for non-malicious flatpak packagers while failing to protect users from malicious packages.
Also, GNOME needs a Flatpak permissions center like KDE. You shouldn't need to install a third party program to manage permissions.
- it’s weird that android and ios already provide this but THE container standard doesn’t
- Absolutely, permissions should be disabled by default, and only when the app needs to do something that requires a certain permission should it ask for it.
  Maybe even do something like Android, where permissions automatically get revoked if you don't use an app for a certain time. I love that feature.
  
  It's the first time I hear someone praise Android messing with user's settings. Care to elaborate why you like it?
- I've tried to combat this a bit with a global Flatpak override that takes unnecessarily broad permissions away by default, like filesystem=home, but apps could easily circumvent it by requesting permissions for specific subdirectories. This cat-and-mouse game could be fixed by allowing a recursive override, such as nofilesystem=home/*.
  But even then, there is still the issue with D-Bus access, which is even more difficult to control ...
  I think it is sad that Flatpak finally provides the tool to restrict desktop apps in the same way that mobile apps have been restricted for a decade, but the implementation chooses to be insecure by default and only provides limited options to make it secure by default.
  
  I think the main reason why the implementation is insecure by default is simply because when it started most applications did not use portals and many portals we have today did not exist. You had to poke holes in the sandbox to make anything work cause all applications expected to run unconstrained. In the future as more apps become flatpak aware this should stop being an issue.
- Situation actually even worse https://madaidans-insecurities.github.io/linux.html#flatpak
  
  I don't doubt it, but this is a good place to start.
  This claim has interesting phrasing:
  Adding X11 sandboxing via a nested X11 server, such as Xpra, would not be difficult, but Flatpak developers refuse to acknowledge this and continue to claim, "X11 is impossible to secure".
  If you look at the GNOME post, you'll see they haven't argued against including a nested X server at all:
  Now that the basics are working it’s time to start looking at how to create a real sandbox. This is going to require a lot of changes to the Linux stack. For instance, we have to use Wayland instead of X11, because X11 is impossible to secure.
  I'm not saying they haven't refused to acknowledge this elsewhere, but it's strange to point to this blog post which acknowledges that the sandbox is very much a work-in-progress and agrees with Madaidan that X11 is hard to secure.
  Does Xpra provide better sandboxing than XWayland? If not, I think the Flatpak developer's solution to this is: just use Wayland. And obviously, there's plenty of room to improve with the permissions Flatpak does offer.
  I did some searching on the Flatpak Github for issues and found that you can actually use Xpra with Flatpak, and the answer is "just use Wayland":
  https://github.com/flatpak/flatpak/issues/3833
  https://github.com/flatpak/flatpak/issues/3684
  This is also concerning:
  As odd as this may sound, you should not enable (blind) unattended updates of Flatpak packages. If you or a Flatpak frontend (app store) simply executes flatpak update -y, Flatpaks will be automatically granted any new permissions declared upstream without notifying you. Using automatic update with GNOME Software is fine, as it does not automatically update Flatpaks with permission changes and notifies the user instead.
  Source: https://privsec.dev/posts/linux/desktop-linux-hardening/#flatpak
  It's great that GNOME Software notifies you when permissions change! I don't use Flatpak enough to know, but I hope flatpak update notifies you too if you don't use the -y option.

Why is it censored lol
- It's actually Dippi but I don't want to look like I'm advertising it here
- !peepee !< is safe

This kind of thing could work for a few apps, say a color picker utility or a QR code generator etc.
Looking at the docs, it isn't clear if apps can write to their own namespace (instead of writing to user folders directly), but if they can, we could expand the scope to games like supertuxkart, 2048 etc, which would then be able to save user milestones and progress in their own area - a bit like how Android apps do it
https://docs.flatpak.org/en/latest/sandbox-permissions.html
It's a great start IMO, although admittedly there is still work to do. Flatpak atm bridges the gap with allowing new apps, requiring new libs, to run on older stable/LTS distros
- Yes, they can. There are app-specific folders in .local that flatpaks can read and write to specifically for this purpose, and also the file picking dialog may give access to the one specific file you picked.
  Android IMO has great usability in exposing a database to apps, which means they aren't required to ship their own database engine.
  
  Get a database, data que and service mesh and we can have an advanced k8s style platform.

Likes like Hello World is ready to ship.
- With a bit of modifying code to use the color picker and maybe rearranging the workflow to adapt to the new system, apps as advanced as DaVinci Resolve and LibreOffice can have permissions as restrictive as this (the network permission would of course may be needed but it would still be marked as Safe by Flathub).
  You can use the file picker API to open the files or folders your app would need to access while having no filesystem permissions at all. You can access the camera, microphone, and GPS without the user devices portal, by simply using the respective portals where the user has the power to allow or deny access to such devices as they wish.
  You can record the screen, take a screenshot, and pick a color in the screen by simply calling the proper portals, with the bonus that the user will be able to select if they want the entire screen, a specific window, or a specific area to be recorded/captured and whether the cursor should be shown or not.
  Heck, even TeamViewer can be as this restricted without losing any functionality if they use the Screen Cast portal which allows apps to mirror input from a remote device! They would of course need the network permission, but that's still safe.
  
  Does all of this require flatpack specific APIs?

this sandbox craze is slowly pushing things back to the point where we used cartridges and booted off from them straight to the program. who needs an OS at this point? it's bundled with the app anyway 😆
/s, somewhat

It's nice to see good app security being praised. Sometimes it feels like some people on lemmy (and the fediverse) throw security to the wind.
Like one time I had heard someone over on Mastodon say that they thought that HTTPS was too overused and shouldn't have been everywhere because it makes older apps unable to access sites and also made adblocking just ever so slightly harder.
Which yeah, I love adblockers, but I'm definitely not comfortable with all traffic having to go unencrypted just for it.
- But my 1998 Windows CE device that's made obsolete by those meddling modern security practices!

This is useful for proprietary software.
- As well as FOSS too. Sandboxing is a security standard that should be followed by every software how open their code may be.

What is this? A solitaire game?
- This could well be an advanced video editor or an office suite if they take full advantage of the portals API without losing any functionality. Well, they can have the network permission, it would still be safe anyway.
  
  I agree with you
  however this program can't even create files, although I may have misunderstood it
  how are you supposed to save your work?

Does it have to be sandboxed?
- An app should not be able to access stuff the user did not consent to letting access.
  
  Isn't that what file system permissions are for?

Cool

Still not worth dependency hell.
- Flatpak reduces dependency hell... and proper sandboxing has nothing to do with dependency hell.
- Relevance?

94 comments