Show HN: Nucleus – A security-hardened, Nix-native container runtime

(github.com)

34 points | by 0kenx a day ago

12 comments

waterfisher 20 hours ago
Please, guys, I beg of you: even if you're going to let LLMs generate whole wheel-reinventing GitHub repositories for you (I've let them generate many!), at least write your Hacker News posts yourself. The ability to write a Hacker News post without LLM assistance non-trivially relates to the ability to develop good software, because it boils down to skills conceptualising the project in a way that makes sense to humans, such that the project is product-shaped, rather than loose-blob-of-proper-nouns shaped. It's just very difficult to invest trust in a piece of software doing the right thing when it's not clear someone on the other end has enough ability to express their own ends in writing to make clear what that right thing is.
[-]
- mpalmer 19 hours ago
```
    If your mental model is "run my image instead of docker run," this won't fit. If it's "run untrusted or ephemeral workloads with stronger, auditable isolation on a single host," that's the target.
```
  This in particular is barely coherent.
jambay 23 minutes ago
I'm curious if Linux aarch64 would be difficult to support with this.

wallzero 17 hours ago

This is neat! Is it rootless? Could it pair with devenv?

I've just gone down a rabbit hole with Fedora atomic desktop (Kinoite), Flatpak Zed, devcontainers with podman compose using the Debian container and nix feature, and devenv.

It allows me to keep an immutable OS while still having an infrastructure as code development experience. Also team members on MacOS or Windows can choose to use devcontainers to wrap devenv or just skip devcontainers and the extra isolation. It's pretty portable.

[-]

0kenx 7 hours ago
Yes it's rootless and can pair with devenv. MacOS is unfortunately not supported because seccomp is not available.

lifeisstillgood 14 hours ago

>>> devcontainers with podman compose using the Debian container and nix feature, and devenv.

Can you expand on that please?

[-]

wallzero 6 hours ago

Sure!

Side note: Unfortunately VSCode devcontainers aren't open source and do not work with VSCodium. Upvote if you'd like VSCode devcontainers open sourced. [1] This example should still work with VSCode though. And the devcontainer CLI.

Also, Zed has some issues around Podman and SELinux with an open PR. [2] And unfortunately Podman Compose does not currently work with Flatpak Zed. [3]

In Zed to enable Podman, add the following to Zed 'settings.json':

  "use_podman": true

Then we're just mostly following the guide:

https://containers.dev/guide/dockerfile

Create '.devcontainer/devcontainer.json':

  {
    "name": "projectName",
    "runArgs": ["--name", "projectName"],
    "dockerComposeFile": "docker-compose.yml",
    "service": "devcontainer",
    "features": {
      "ghcr.io/devcontainers/features/nix:1": {
        "packages": "devenv"
      }
    },
    "workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",
    "onCreateCommand": "nix-env -iA nixpkgs.devenv",
    "postCreateCommand": "git config --global user.name \"${GIT_USER_NAME}\" && git config --global user.email \"${GIT_USER_EMAIL}\" && git config --global --add --bool push.autoSetupRemote true && echo 'eval \"$(devenv hook bash)\"' | tee -a ~/.bashrc"
  
    // If compose isn't needed use the following:
    // "image": "mcr.microsoft.com/devcontainers/base:debian",
    // "containerEnv": {
    //   "GIT_USER_NAME": "${localEnv:GIT_USER_NAME}",
    //   "GIT_USER_EMAIL": "${localEnv:GIT_USER_EMAIL}",
    //   "SSH_AUTH_SOCK": "/run/host-services/ssh-auth.sock",
    // },
    // "mounts": [
    //   "source=${localEnv:XDG_RUNTIME_DIR}/ssh-agent.socket,target=/run/host-services/ssh-auth.sock,type=bind",
    // ],
  }

Then create '.devcontainer/docker-compose.yml':

  name: projectName
  services:
    devcontainer:
      image: mcr.microsoft.com/devcontainers/base:debian
      command: sleep infinity
      userns_mode: keep-id
      environment:
        SSH_AUTH_SOCK: /run/host-services/ssh-auth.sock
        GIT_USER_EMAIL: ${GIT_USER_EMAIL?err}
        GIT_USER_NAME: ${GIT_USER_NAME?err}
        POSTGRES_DB: ${POSTGRES_DB:-projectName}
        POSTGRES_USER: ${POSTGRES_USER:-postgres}
        POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-postgres}
      ports:
        # To connect to postgres running inside the container
        - target: 5432
          published: 5432
          protocol: tcp
          host_ip: 127.0.0.1
          mode: host
      volumes:
        - ${XDG_RUNTIME_DIR}/ssh-agent.socket:/run/host-services/ssh-auth.sock:bind
        - ..:/workspaces/projectName:cached

And lastly create 'devenv.nix':

  { pkgs, config, ... }: {
    env.GREET = "determinism";
  
    enterShell = ''
      echo hello ${config.env.GREET}
    '';
  
    packages = [
      pkgs.nodejs
      pkgs.yarn
    ];
  
    services = {
      postgres = {
        enable = true;
        listen_addresses = "0.0.0.0";
        hbaConf = ''
          # TYPE      DATABASE      USER      ADDRESS       METHOD
            local       all         all                     peer
            host        all         all       127.0.0.1/32  trust
            host        all         all       0.0.0.0/0     md5
        '';
        initialDatabases = [
          {
            name = "postgres";
          }
          {
            name = "projectName";
          }
          {
            name = "projectName_auth";
          }
        ];
        initialScript = ''
          CREATE ROLE postgres SUPERUSER LOGIN PASSWORD 'postgres';
          CREATE ROLE api LOGIN PASSWORD 'api';
          CREATE ROLE auth LOGIN PASSWORD 'auth';
        '';
        settings = {
          wal_level = "logical";
        };
      };
    };
  
    scripts = {
      drizzle.exec = "npx lerna run --scope @projectName/drizzle \"$@\"";
      better-auth.exec = "npx lerna run --scope @projectName/better-auth \"$@\"";
    };
  }

On Linux with SELinux, until the PR [2] is merged, a workaround for Zed needs to be applied:

  # ~/.config/containers/containers.conf
  [containers]
  label = false

After this you can work within a podman container, connect to adjacent compose services, and use nix and devenv. If a collaborator wants to skip containers they can just run devenv locally. Though I think devcontainers running devenv is actually the easier route provided that they are setup and working on your OS.

And this all works pretty much out of the box without root on an immutable OS like Fedora Silverblue/Kinoite.

---

[1](https://github.com/microsoft/vscode-remote-release/issues/11...)

[2](https://github.com/zed-industries/zed/pull/58500)

[3](https://github.com/flathub/dev.zed.Zed/pull/342#issuecomment...)

lavaman131 15 hours ago
Very cool to see more security focused tools being built here for the Nix ecosystem. What were some of the biggest roadblocks or challenges you hit when building this?
alberand 15 hours ago
Isn't it the same as using systemd-nspawn? containers.<name> let you declare containers with nspawn. What's the difference?
[-]
- 0kenx 7 hours ago
  my main reason for building this is gvisor/seccomp/capability/landlock
yjftsjthsd-h 17 hours ago
> rootfs attestation verifies a per-file SHA-256 manifest at startup;
What threat model does this protect against? Certainly nice, especially for free, but wondering about utility.
[-]
- 0kenx 7 hours ago
  it's a simple integrity check for catching deployment drift/tampering.