agent-sandbox

A secure, embeddable, WASM-based sandbox for AI agents. 80+ built-in CLI tools, a full shell interpreter, a JavaScript runtime, safe HTTP networking, <13ms startup, no Docker/VMs required.

Installation

Rust

cargo add agent-sandbox

Node.js

npm install @parassharmaa/agent-sandbox

Prebuilt binaries are available for macOS (arm64, x64), Linux (x64, arm64), and Windows (x64).

Quick Start

Rust

use agent_sandbox::{Sandbox, config::SandboxConfig, FetchPolicy};

let config = SandboxConfig {
    work_dir: "/path/to/workdir".into(),
    fetch_policy: Some(FetchPolicy::default()), // enable networking
    ..Default::default()
};
let sandbox = Sandbox::new(config)?;

let result = sandbox.exec("grep", &["TODO".into(), "/work/main.rs".into()]).await?;
println!("{}", String::from_utf8_lossy(&result.stdout));

// Execute JavaScript inside the sandbox
let js_result = sandbox.exec_js("console.log('Hello from JS!')").await?;

// HTTP fetch with SSRF protection
let response = sandbox.fetch(FetchRequest {
    url: "https://api.example.com/data".into(),
    method: "GET".into(),
    headers: Default::default(),
    body: None,
}).await?;
println!("Status: {}", response.status);

Node.js

import { Sandbox } from "@parassharmaa/agent-sandbox";

const sandbox = new Sandbox({
  workDir: "/path/to/workdir",
  fetchPolicy: { denyPrivateIps: true },
});

const result = await sandbox.exec("grep", ["TODO", "/work/main.rs"]);
console.log(result.stdout.toString());

// Execute JavaScript inside the sandbox
const jsResult = await sandbox.execJs("console.log('Hello from JS!')");

// HTTP fetch
const response = await sandbox.fetch({ url: "https://api.example.com/data" });
console.log(response.status, response.body.toString());

// curl interception — routed through the safe client
const curlResult = await sandbox.exec("curl", ["https://api.example.com/data"]);

const changes = await sandbox.diff();
await sandbox.destroy();

Features

• 80+ tools: cat, grep, find, sed, awk, jq, git, tar, zip, curl, seq, md5sum, and more
• Full shell interpreter (sh/bash) with pipes, redirections, variables, loops, functions, and command substitution
• Built-in JavaScript runtime (Boa engine) via node command or execJs() API
• Safe HTTP networking with SSRF protection, domain policies, and rate limiting
• fetch() available in JS runtime, as a direct API, and via curl command interception
• Filesystem sandboxing with path traversal prevention
• Resource limits: fuel, timeout, memory
• Change tracking via filesystem snapshots
• AOT precompiled WASM — <13ms cold start, ~55us cached
• Node.js bindings (NAPI)

Networking

The sandbox provides safe HTTP access via agent-fetch, with built-in SSRF protection, domain allowlists/blocklists, DNS rebinding prevention, and rate limiting.

Networking is disabled by default. Enable it by providing a fetchPolicy:

const sandbox = new Sandbox({
  workDir: "/tmp/work",
  fetchPolicy: {
    allowedDomains: ["api.example.com", "*.github.com"], // optional allowlist
    blockedDomains: ["evil.com"],                        // optional blocklist
    denyPrivateIps: true,                                // block 127.0.0.1, 10.x, etc.
    requestTimeoutMs: 30000,
    maxRedirects: 10,
  },
});

Three ways to make HTTP requests:

// 1. Direct fetch API
const res = await sandbox.fetch({
  url: "https://api.example.com/data",
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: Buffer.from(JSON.stringify({ key: "value" })),
});

// 2. curl command (intercepted and routed through the safe client)
await sandbox.exec("curl", ["-X", "POST", "-d", '{"key":"value"}', "https://api.example.com"]);

// 3. fetch() inside the JS runtime
await sandbox.execJs(`
  var r = fetch('https://api.example.com/data');
  console.log(r.status, r.text());
`);

JavaScript Runtime

The sandbox includes a built-in JavaScript engine (Boa) that runs entirely inside the WASM sandbox. Use it via the node command or the execJs() convenience method.

// Inline evaluation
await sandbox.exec("node", ["-e", "console.log('hello')"]);

// Evaluate and print result
await sandbox.exec("node", ["-p", "2 + 3 * 4"]); // stdout: "14"

// Run a script file (from /work)
await sandbox.writeFile("script.js", Buffer.from(`
  const data = [1, 2, 3, 4, 5];
  console.log(JSON.stringify({ sum: data.reduce((a, b) => a + b) }));
`));
await sandbox.exec("node", ["/work/script.js"]);

// Convenience method
await sandbox.execJs("console.log('quick and easy')");

// fetch() is available when networking is enabled
await sandbox.execJs("var r = fetch('https://example.com'); console.log(r.ok)");

Supported JS features: ES2023+ (variables, arrow functions, destructuring, template literals, Promises, Map/Set, JSON, Math, RegExp, Array methods, and more).

Shell Interpreter

The sandbox includes a full shell interpreter accessible via sh or bash. It supports most common shell constructs, all running entirely inside the WASM sandbox.

Pipes and Redirections

// Pipes
await sandbox.exec("sh", ["-c", "echo hello world | wc -w"]);           // stdout: "2"
await sandbox.exec("sh", ["-c", "cat /work/data.csv | sort | uniq -c"]);

// Output redirection
await sandbox.exec("sh", ["-c", "echo hello > /work/out.txt"]);
await sandbox.exec("sh", ["-c", "echo world >> /work/out.txt"]);         // append

// Input redirection
await sandbox.exec("sh", ["-c", "wc -l < /work/data.txt"]);

Variables and Expansion

// Variable assignment and expansion
await sandbox.exec("sh", ["-c", "NAME=world; echo hello $NAME"]);        // "hello world"

// Default values
await sandbox.exec("sh", ["-c", 'echo ${UNSET:-fallback}']);              // "fallback"
await sandbox.exec("sh", ["-c", 'X=; echo ${X:=default}; echo $X']);     // "default\ndefault"

// String length
await sandbox.exec("sh", ["-c", 'S=hello; echo ${#S}']);                  // "5"

// Command substitution
await sandbox.exec("sh", ["-c", "echo today is $(date)"]);
await sandbox.exec("sh", ["-c", "FILES=$(ls /work); echo $FILES"]);

// Arithmetic
await sandbox.exec("sh", ["-c", "echo $((3 + 4 * 2))"]);                 // "11"

// Special variables
await sandbox.exec("sh", ["-c", "echo exit=$? args=$# pid=$$"]);

Control Flow

// if/elif/else
await sandbox.exec("sh", ["-c", `
  if [ -f /work/config.json ]; then
    echo "config exists"
  else
    echo "no config"
  fi
`]);

// for loops
await sandbox.exec("sh", ["-c", `
  for f in /work/*.txt; do
    echo "processing $f"
    wc -l "$f"
  done
`]);

// while loops
await sandbox.exec("sh", ["-c", `
  i=1
  while [ $i -le 5 ]; do
    echo $i
    i=$((i + 1))
  done
`]);

// case statements
await sandbox.exec("sh", ["-c", `
  EXT=.rs
  case $EXT in
    .rs)  echo "Rust" ;;
    .js)  echo "JavaScript" ;;
    .py)  echo "Python" ;;
    *)    echo "Unknown" ;;
  esac
`]);

Functions

await sandbox.exec("sh", ["-c", `
  greet() {
    echo "Hello, $1!"
  }
  greet World
  greet Agent
`]);
// stdout: "Hello, World!\nHello, Agent!"

Command Chaining

// AND chain — runs second only if first succeeds
await sandbox.exec("sh", ["-c", "mkdir -p /work/out && echo 'created'"]);

// OR chain — runs second only if first fails
await sandbox.exec("sh", ["-c", "cat /work/missing.txt 2>/dev/null || echo 'not found'"]);

// Semicolons — always runs both
await sandbox.exec("sh", ["-c", "echo one; echo two"]);

Real-World Agent Examples

// Install dependencies and run tests (typical CI pattern)
await sandbox.exec("sh", ["-c", `
  cd /work && \
  cat package.json | jq -r '.dependencies | keys[]' | sort > deps.txt && \
  echo "Found $(wc -l < deps.txt) dependencies"
`]);

// Process data pipeline
await sandbox.exec("sh", ["-c", `
  for file in /work/logs/*.log; do
    grep ERROR "$file" | wc -l
  done | awk '{sum+=$1} END {print "Total errors:", sum}'
`]);

// Generate a report
await sandbox.exec("sh", ["-c", `
  echo "# File Report" > /work/report.md
  echo "" >> /work/report.md
  for f in /work/src/*.rs; do
    lines=$(wc -l < "$f")
    name=$(basename "$f")
    echo "- $name: $lines lines" >> /work/report.md
  done
`]);

Available Commands

Text Processing: cat, head, tail, grep, rg, sed, sort, uniq, cut, tr, wc, awk, tac, rev, nl, paste, comm, join, fold, column, expand, unexpand, strings, od

Search & Files: find, tree, ls, mkdir, cp, mv, rm, du, ln, stat, touch, tee, readlink, rmdir, split, file

Data & Hashing: jq, diff, patch, base64, sha256sum, sha1sum, md5sum, xxd

Archives: tar, gzip, zip

Code & Version Control: git

Shell & Utilities: sh, bash, echo, printf, env, xargs, basename, dirname, seq, sleep, which, whoami, hostname, printenv, date, expr, true, false, test, [

Networking: curl (intercepted through safe client)

JavaScript Runtime: node

Limitations

• JS runtime has no Node.js built-in modules (fs, http, etc.) — fetch() is the only network API
• Single-threaded execution (pipes run sequentially via temp files)
• Shell does not support job control, signal handling, or process spawning
• Same-architecture precompiled binary

Best for: file-manipulation agents (code analysis, refactoring, git ops), sandboxed JS evaluation, safe API calls, multi-step shell scripts. Not for: databases, GPU, long-running servers.

License

MIT