IdeaWell

Project ideas from Hacker News discussions.

Landlock-Ing Linux

Original Article

Hacker News Discussion

📝 Discussion Summary (Click to expand)

Here are the three most prevalent themes from the Hacker News discussion about Landlock:

1. Landlock as a Developer-Driven Building Block for Defense-in-Depth

A major theme is Landlock's role as an unprivileged security mechanism developers can integrate directly into their applications to incrementally reduce their own process privileges, regardless of host configuration (like SELinux/AppArmor). This contrasts with external, admin-driven security tools.

  • Supporting Quotes:
    • "LandLock is a Minor LSM intended for software developers. They incorporate it into their source code to limit where the programs may read/write." ("seethishat")
    • "It's just a building block that devs can use... In the application code itself is where landlock shines at the moment." ("razighter777")
    • "The opposite is true. Containwrization systems were built into operating systems as security features... Landlock is an all right start at unprivileged restrictions..." ("zbentley")

2. Synergy and Distinction from Containers

Users frequently discussed how Landlock relates to existing containerization technologies. The consensus is that Landlock is complementary to containers, not a replacement, because containers primarily virtualize environments (namespaces, filesystem isolation), whereas Landlock provides resource-oriented, granular restrictions within a running process.

  • Supporting Quotes:
    • "Comparing landlock to containers isn't really an apples to apples comparison. Containers use a bunch of linux security mechanisms together like chroot seccomp and user namespaces to accomplish their goals. Landlock is just another building block that devs can use." ("razighter777")
    • "This is very distinct from a resource oriented approach like landlock... They would layer nicely." ("staticassertion")
    • "One of the most annoying parts of being in a container is that you can't sandbox yourself further within that container... if you want to go further than what a container provides, landlock is a powerful solution." ("staticassertion")

3. The Nature of Unrevocable, Programmatic Restriction

A core technical point of interest is Landlock's design principle: once restrictions are applied to a process, they are permanent for that process's lifetime, preventing escalation even if the application is later compromised (e.g., via malicious input).

  • Supporting Quotes:
    • "You can not give extra permissions only limit further." ("RonanSoleste")
    • "The kernel enforces that once the policy gets added it can't be removed. So the restrictions are permanent for the life of the program. Even root can't undo them." ("razighter777")
    • "The only way for it to un-restrict itself would be to also compromise the Linux kernel. So you have 2 things you have to compromise to own the machine, instead of just 1." ("zie")

🚀 Project Ideas

Landlock Policy Translator and Validator Service

Summary

  • A centralized, version-controlled service for defining, validating, and generating Landlock policies using a high-level DSL.
  • Solves developer friction around C-level syscall interaction, path handling, and ensuring policies are safe/compatible across kernel versions.

Details

Key Value
Target Audience Application developers already using or planning to use Landlock in Go/Rust/C.
Core Feature A REST API that accepts a declarative policy specification (e.g., "Allow Read/Write to /app/data but Deny TCP Bind") and returns the appropriate, kernel-version-aware C/syscall bindings or library-specific code snippets (Go/Rust).
Tech Stack Python/Django or Rust/Actix for the backend API. YAML/JSON for the DSL input. Integrates with kernel UAPI headers for version checking.
Difficulty Medium
Monetization Hobby

Notes

  • Directly addresses the pain points raised by smartmic ("Since when is not a C API the first and foremost interface...") and the confusion around writing wrappers (butvacuum).
  • Developers could use this to easily test policies before deployment, especially addressing dynamic path issues mentioned by staticassertion (e.g., pre-creating placeholders for paths that might not exist yet).

"Container-Exit" Audit/Harden Tool

Summary

  • A simple CLI tool that executes a trusted pre-launch utility (like landrun or a custom binary) which applies maximum necessary Landlock restrictions immediately before executing a potentially untrusted third-party binary (like a script or downloaded game).
  • A layer of defense-in-depth specifically for processes being spawned outside of typical container/VM controls, solving the developer's dilemma about wrapping untrusted apps.

Details

Key Value
Target Audience Developers needing to run arbitrary, untrusted binaries (e.g., game launchers like dannyfritz07, build scripts like williamstein).
Core Feature A CLI tool that accepts a path to an executable and a declarative set of resource restrictions (based on Landlock V1 capabilities). It handles the boilerplate of setting up the Landlock policy and calling execve.
Tech Stack Go (due to ease of cross-compilation and strong Landlock library support) or C (using the kernel header API, as shown in the kernel samples).
Difficulty Low/Medium
Monetization Hobby

Notes

  • Directly appeals to users like dannyfritz07 who struggle with the complexity of bwrap for simple isolation and pdimitar/tux3 who are looking for executable wrappers when container policies lag.
  • Addresses why an application developer might want a wrapper tool: to dynamically restrict a third-party binary they don't control, which is distinct from systemd/container managers applying static rules (razighter777).

Kernel Landlock Feature Compatibility Checker

Summary

  • A small system utility or library function to introspect the running kernel and determine exactly which Landlock features are available (e.g., file restrictions, TCP bind allowance) without relying on just syscall availability.
  • Solves the version fragility issue where restrictive policies might fail due to newer kernel features not being present on a production system.

Details

Key Value
Target Audience Application developers creating software that needs to run across a wide range of Linux kernel versions (5.13+).
Core Feature A function/tool that returns a structured output detailing Landlock feature parity (e.g., {"tcp_bind_allowed": true, "udp_support_status": "pending_patch_series"}).
Tech Stack C (leveraging the UAPI headers and uname/sysinfo calls) or Rust.
Difficulty Low
Monetization Hobby

Notes

  • Directly addresses the concern raised by arianvanp regarding compatibility across kernel versions: "The only way to do that is to have the developer tell what parts need to be restricted explicitly and you can't restrict what isn't implemented yet."
  • This utility provides the "know if Landlock is present without just trying the syscalls" information mentioned by fiiin in a robust, feature-aware way.