Show HN: Zerobox – Sandbox any command with file and network restrictions
Zerobox is a novel, cross-platform CLI tool for sandboxing commands, focusing on file, network, and crucial credential restrictions. It leverages native OS sandboxing with a deny-by-default policy and an innovative MITM proxy for secure API key injection. Hacker News finds this particularly compelling for securing AI agents and offering a lightweight, Docker-alternative approach to process isolation, though its default file read policy and overall credibility are discussed.
The Lowdown
Zerobox, introduced as a new project on Hacker News, is a cross-platform command-line interface (CLI) tool written in Rust designed to sandbox any command with precise file and network restrictions. It distinguishes itself by adopting a 'deny by default' security posture, similar to Deno, where writes and network I/O are blocked unless explicitly allowed. The tool boasts minimal overhead and operates without the need for VMs or Docker, making it a lightweight solution for process isolation.
- Core Functionality: Wraps commands, runs an MITM proxy, and utilizes native OS sandboxing solutions (e.g., Bubblewrap on Linux, Seatbelt on macOS).
- Credential Injection: A key feature is its ability to inject secrets (like API keys) at the network proxy level. This means the sandboxed process only sees a placeholder, and the real credential is substituted only when an approved outbound network call is made, preventing the process from ever directly accessing sensitive information.
- Resource Controls: Offers granular control over file access (allow/deny reads/writes to specific paths), network traffic (allow/deny by domain), and environment variables.
- AI Agent Focus: The author explicitly targets AI agents, suggesting future capabilities like
zerobox claude, to wrap entire agent processes with preloaded policy profiles. - Performance: Benchmarks show a typical overhead of around 10ms and 7MB memory increase, making it efficient for various use cases.
- SDK: Includes a TypeScript SDK for programmatic sandboxing, offering Deno-style API methods.
Zerobox presents itself as a practical solution for developers needing robust, local sandboxing capabilities, particularly valuable for scenarios involving untrusted code execution, such as running AI-generated code or restricting LLM tool calls.
The Gossip
Credibility Concerns and Comprehensive Call
Users expressed a strong need for detailed documentation, robust testing, and thorough architectural explanations to build trust in new sandboxing tools. They highlighted that while underlying frameworks are credible, misconfigurations at higher levels are common. The author acknowledged this feedback, committing to improving documentation and testing, and pointed out that Zerobox builds upon OpenAI Codex's sandboxing crates.
Secure Secrets and Sensible Sandboxing
The credential injection mechanism, which uses an MITM proxy to replace placeholder API keys with real values only at the network layer, was highly praised as an innovative security feature. This prevents sandboxed processes, especially AI agents, from directly accessing sensitive secrets. The default-deny network policy was also noted as crucial for preventing data exfiltration.
Deliberating Default Denials
A discussion arose regarding Zerobox's default policy of allowing all file reads, in contrast to its deny-by-default for writes and network. Some users felt a default-deny for reads would be safer, acknowledging the complexity it introduces for common toolchains. The author clarified how to deny all reads but sought input on the optimal default user experience.
Performance Ponderings and Platform Comparisons
Commenters inquired about the performance overhead of Zerobox and how it compares to established solutions like Docker or lower-level OS tools such as Bubblewrap. The author provided benchmarks indicating a minimal 10ms overhead and clarified that Zerobox leverages these native OS sandboxing mechanisms.