Snap packages and SSL-certificates.. A neverending story

Photo by Magda Ehlers: https://www.pexels.com/photo/a-broken-bicycle-leaning-on-the-wall-5342343/

Alternative title: Why I hate developers who reinvent the wheel - but forget the spokes.

This is more of a rant and link-dump article. I didn't research everything in detail as I generally avoid Snaps. So far they've caused me more troubles than benefits.. But I wanted a place to keep all my arguments and links to certain documentation sites in one place.. So here we go.

Snap is, compared to packaging formats like RPM and APT, relatively new. Maybe this explains why it still has some teething problems. The most annoying one for me is: Snap packages don't use your custom SSL-Certificates, stored in /usr/share/ca-certificates. Which is the default place to store your companies Root-CA certificates. Every browser respects this. There is tooling in every Linux distribution to take care of stored certificates and adding them to the truststore. There is tooling to automatically add these certificates to any Java (or other language) truststore that might reside on your system.

But no, that would be too easy mirroring that behaviour in Snap, right? After all.. Why just reinvent the wheel, when you can have more fun by forgetting the spokes.
Yes, I am aware that centreless/hubless wheels do exist. ;-)

The root cause is often: Snap Confinement (or to be precise: The strict confinement mode). Which means a snap is separated from the system and only has access to directories which are configured at build time of the snap, as stated in Interface Management documentation (see also: https://snapcraft.io/docs/home-interface and https://snapcraft.io/docs/supported-interfaces). And as desirable and good this is. Reality teaches us that for every application you always need a way to modify, to configure it. At least certain aspects. With snap.. Not so much?

In the latest Ubuntu releases Firefox and Chromium have been migrated exclusively to snap. You cannot install a Firefox via apt and have a normal install. You will get a snap package. Which means: Goodbye SSL Client cert authentication, goodbye internal company SSL certificates. Bug 1901586: [snap] CA Certificates from /usr/local/share/ca-certificates are not used has all the details.

Yes, clever people might add: But you can do a bind mount and mount that directory under /home where nearly every Snap application has access. But why do I need to do this? Why does Snap impose that burden on me, the user? And this doesn't fix the SSL issue..

Oh, I should copy them to /etc/ssl/certs? And what about the other troubles this might cause? .. Hello? Nothing? Oh, okay..

And it keeps getting better: If you install the Videoplayer VLC as a snap package and your files are not located under /home.. You can't access them. Snap developers will happily advise you to move your files, change the mountpoint or do a mount --bind under /home. Which can be seen here: Bug 1643706: snap apps need to be able to browse outside of user $HOME dir. for Desktop installs

And this is the point I want to make. It's OK to design a new packaging format for applications. It's okay to add security mechanism like snap confinement. But designing them in way so that each and every user is forced to manage/store/organize files in the way snap dictates? Nope, sorry.

Someone on the Internet wrote that Snap is a great idea for things like phones, PCs in public space (libraries, schools, etc.) or other confined environments where the user doesn't and shouldn't be allowed to configure many aspects. Where a system is designed and offered for only some specific purposes which are more or less static and change seldom.

And I agree. For me the root cause with all my problems regarding Snap is: It isn't the only daemon on my system. It HAS to integrate into the existing system and processes, like update-ca-certificates or even where in the filesystem I store my files. This was all there before Snap existed and now applications which always worked won't because someone thought it is better that way.. No, sorry. Like I said before: It HAS to integrate into the existing system. If it doesn't.. It might still have it use-cases. I'm not arguing against that. But then please let me have a choice! But breaking existing workflows, file structures, etc. that is not acceptable for me. And as the Internet shows, also not for many other users.

The sad part is that the decision to make Firefox only available as a Snap was done by Mozilla & Canoncial. Therefore you can't download the .deb from the Mozilla Webpage or the like. (Luckily there is still a PPA which build Firefox as .deb package offered by volunteers. This means it can potentially vanish if there is no one left doing it. But that's more or less the risk with any piece of software/technology.)

The announcement is on their Discourse: https://discourse.ubuntu.com/t/feature-freeze-exception-seeding-the-official-firefox-snap-in-ubuntu-desktop/24210/1

Oh and Snaps tend to auto-upgrade, even without unattended-upgrades configured. Which can be a problem if you require a specific version. Luckily snap refresh --hold can hold updates for all Snap packages. Or, if you just want it for some specific package/time use snap refresh --hold=72h vlc. This post has more information: Hold your horses, I mean snaps! New feature lets you stop snap updates, for as long as you need (snapcraft.io)

Security considerations

Snap was invented by Canoncial. The Snap-Store is run by Canoncial. Snap packages are slowly replacing more and more .deb-packages in Ubuntu, when you type apt-get install packagename you will automatically get a snap package if one exists.

Or if you try to execute a command which isn't present on your system. Then the command-not-found helper from Ubuntu will recommend you the associated .deb or Snap package.

The problem? Aquasec discovered that many traditional programs are not available as a Snap, but Canoncial still allows you to register Snaps with the exact same name, despite providing an entirely different program. (aquasec.com)

Additionally you can specify aliases or register Snaps for the literal filenames. The example shows how, when you try to execute the command tarquingui, command-not-found recommends to install the tarquin Snap. Which provides the tarquingui program. But they were able to additionally register a Snap with the name tarquingui. What happens? command-not-found now recommends both Snaps.

My personal opinion is that it is a dangerous and dumb oversight to not reserve every APT-package on the Snap store. Preventing the hijacking of well established software packages by potentially malicious third parties. After all it was Canoncial who introduced Snap and it's Canoncial who solely operates the Snap-Store...

How to install Firefox as .deb package (Ubuntu 23.04)

Update: I recently learned of a bug in unattended-upgrades which ignores apt-pinnings if the origin is not listed in the allowed-origins: #2033646 unattended-upgrade ignores apt-pinning to not-allowed origins

To prevent this bug, use the following workaround:

root@host:~# echo 'Unattended-Upgrade::Allowed-Origins:: "LP-PPA-mozillateam:${distro_codename}";' | sudo tee /etc/apt/apt.conf.d/51unattended-upgrades-firefox

1. Remove the Firefox snap (omit if not present)
   • snap remove firefox
   • If dpkg -l firefox still shows it as installed, execute:
     • apt-get remove --purge firefox
2. Add the Mozilla PPA
   • add-apt-repository ppa:mozillateam/ppa
     • If the command add-apt-repository is missing, install the package software-properties-common
3. Pin the Mozilla PPA-Repository with higher priority so packages are installed out of this PPA instead of other repositories where they might be available too
   • echo -e "Package: *\nPin: release o=LP-PPA-mozillateam\nPin-Priority: 1001" | sudo tee /etc/apt/preferences.d/mozilla-firefox
4. Update repository information
   • apt-get update
5. Now check that your APT-Package Policies are correct
   • apt-cache policy firefox
     • If set up correctly Candidate: will list the package name which is not a Snap. See the example below.

     • root@ubuntu:/# apt-cache policy firefox
       firefox:
         Installed: (none)
         Candidate: 1:1snap1-0ubuntu3
         Version table:
            1:1snap1-0ubuntu3 500
               500 http://archive.ubuntu.com/ubuntu lunar/main amd64 Packages
            120.0.1+build1-0ubuntu0.23.04.1~mt1 500
               500 https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu lunar/main amd64 Packages
       
       root@ubuntu:/# echo -e "Package: *\nPin: release o=LP-PPA-mozillateam\nPin-Priority: 1001" | tee /etc/apt/preferences.d/mozilla-firefox
       Package: *
       Pin: release o=LP-PPA-mozillateam
       Pin-Priority: 1001
       
       root@ubuntu:/# apt-cache policy firefox
       firefox:
         Installed: (none)
         Candidate: 120.0.1+build1-0ubuntu0.23.04.1~mt1
         Version table:
            1:1snap1-0ubuntu3 500
               500 http://archive.ubuntu.com/ubuntu lunar/main amd64 Packages
            120.0.1+build1-0ubuntu0.23.04.1~mt1 1001
              1001 https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu lunar/main amd64 Packages

6. Install Firefox. You should see that https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu is being used to download Firefox. If not search for errors.
   • • apt-get install firefox