Understanding the "Classic Confinement" Warning in Snap Packages

If you’ve ever installed a Snap package on your Linux system, you may have encountered an error message like this one:

error: This revision of snap "node" was published using classic confinement and thus may perform
       arbitrary system changes outside of the security sandbox that snaps are usually confined to,
       which may put your system at risk.

       If you understand and want to proceed repeat the command including --classic.

This warning can be unsettling, especially if you’re unfamiliar with Snap confinement or how it relates to system security. In this blog, we’ll break down what this error message means, why it’s important, and how you can approach it.

What is “Classic Confinement” in Snap Packages?

Before we dive into the error itself, let’s clarify what “Snap confinement” is and why it matters.

What is a Snap Package?

A Snap package is a type of software packaging format that bundles an application and all of its dependencies into a single package. The Snap ecosystem is designed to be cross-platform, meaning the same Snap package can run on various Linux distributions without modification. Snaps are typically isolated from the rest of your system for security reasons, using something called “confinement”.

What is Confinement?

Confinement refers to the level of isolation a Snap package has from your system. Snaps can have different levels of confinement:

Strict confinement: This is the default and most secure form. In strict confinement, a Snap can only access files and resources that it explicitly requests and is granted permission to access. It is isolated in a sandbox, which minimizes the risk to your system.
Classic confinement: A Snap with classic confinement has fewer restrictions, meaning it has more access to your system and can interact with resources outside the Snap sandbox. It’s much closer to the way traditional packages work, where an app can make arbitrary system changes.
Devmode confinement: This is typically used for development purposes. It allows a Snap to run with fewer restrictions than strict confinement, but it still doesn’t have the unrestricted access of classic confinement.

Why Does the Warning Mention Classic Confinement?

When you see the error message related to “classic confinement,” it’s highlighting the fact that the Node.js Snap you’re installing is published with classic confinement.

In the case of Node.js (or any other Snap with classic confinement), this means the application is not fully sandboxed, and it can interact with your system more freely than a strictly confined Snap. As a result, the Snap can potentially make system-wide changes, access sensitive files, and execute actions that could pose a security risk.

Here’s a breakdown of why this is important:

Security Risks: Since a Snap with classic confinement isn’t as restricted, it may have the ability to make changes that could affect the system. For example, it could access files outside its own sandbox or run system-level commands that could compromise system integrity.
System Stability: Because classic confinement allows a Snap to make broad changes, there’s a risk of instability if the application behaves unexpectedly, conflicts with other software, or has bugs that affect system-wide resources.
Permissions: You, the user, are effectively allowing the Snap to act more like a traditional application, meaning it could have access to parts of the system you may not want it to interact with. For example, a developer tool like Node.js might need to install packages globally, which could conflict with the operating system’s package manager or other installed software.

Why is Classic Confinement Used?

Despite the security trade-offs, classic confinement is sometimes necessary for certain applications, especially those that need low-level system access or need to interact with parts of the system outside of the typical Snap sandbox. In the case of Node.js, it may require the ability to install packages globally or access other resources that are not easily available within the confines of a strict sandbox.

Some use cases where classic confinement might be required include:

Development Tools: Certain programming languages or frameworks (like Node.js, Python, or Go) often require access to system directories and package managers that are outside the sandbox.
Legacy Applications: Some older applications or those not originally designed for Snap confinement may need classic access to function properly.
Complex Dependencies: Applications that require complex interactions with the operating system or external programs might not function well under strict confinement.

What Should You Do When You See This Warning?

If you’re concerned about the risks mentioned in the error message, you have a few options for how to proceed:

Review the Package: Before proceeding, check whether the Snap you’re installing is trustworthy. In the case of popular software like Node.js, the risk is relatively low, as the Snap is likely published and maintained by a reputable source.
Use a Different Installation Method: If you are uncomfortable with classic confinement, you could install Node.js (or any other software) using other methods, such as:
- Using your distribution’s package manager (e.g., apt for Ubuntu, dnf for Fedora).
- Installing from source or using version managers like nvm for Node.js.
  
  These methods often come with more granular control over the installation process and typically don’t require the application to be run with classic confinement.
Proceed with Caution: If you decide to proceed with the Snap, be aware of the potential risks, but know that popular software packages like Node.js are usually safe. Always keep your system updated, and if you encounter issues, check the Snap’s support channels or the community forums for guidance.
Feedback to Snap Maintainers: If you believe a package should be confined more strictly for security reasons, you can always submit feedback or contribute to the Snap packaging project. Open-source communities are often open to suggestions on improving security practices.

Conclusion

The warning about classic confinement is important for understanding the security implications of installing certain Snap packages. While classic confinement allows more freedom for applications to interact with your system, it comes with a trade-off in terms of security. For trusted applications like Node.js, the risk may be minimal, but for less familiar software, it’s worth considering whether a different installation method might be more appropriate.

As with all software installations, stay informed and always review the permissions and the risks involved before proceeding.