codex-cli/src/utils/agent/sandbox/landlock.ts

import type { ExecResult } from "./interface.js";
import type { SpawnOptions } from "child_process";

import { exec } from "./raw-exec.js";
import { execFile } from "child_process";
import fs from "fs";
import path from "path";
import { log } from "src/utils/logger/log.js";
import { fileURLToPath } from "url";

/**
 * Runs Landlock with the following permissions:
 * - can read any file on disk
 * - can write to process.cwd()
 * - can write to the platform user temp folder
 * - can write to any user-provided writable root
 */
export async function execWithLandlock(
  cmd: Array<string>,
  opts: SpawnOptions,
  userProvidedWritableRoots: ReadonlyArray<string>,
  abortSignal?: AbortSignal,
): Promise<ExecResult> {
  const sandboxExecutable = await getSandboxExecutable();

  const extraSandboxPermissions = userProvidedWritableRoots.flatMap(
    (root: string) => ["--sandbox-permission", `disk-write-folder=${root}`],
  );

  const fullCommand = [
    sandboxExecutable,
    "--sandbox-permission",
    "disk-full-read-access",

    "--sandbox-permission",
    "disk-write-cwd",

    "--sandbox-permission",
    "disk-write-platform-user-temp-folder",

    ...extraSandboxPermissions,

    "--",
    ...cmd,
  ];

  return exec(fullCommand, opts, abortSignal);
}

/**
 * Lazily initialized promise that resolves to the absolute path of the
 * architecture-specific Landlock helper binary.
 */
let sandboxExecutablePromise: Promise<string> | null = null;

async function detectSandboxExecutable(): Promise<string> {
  // Find the executable relative to the package.json file.
  const __filename = fileURLToPath(import.meta.url);
  let dir: string = path.dirname(__filename);

  // Ascend until package.json is found or we reach the filesystem root.
  // eslint-disable-next-line no-constant-condition
  while (true) {
    try {
      // eslint-disable-next-line no-await-in-loop
      await fs.promises.access(
        path.join(dir, "package.json"),
        fs.constants.F_OK,
      );
      break; // Found the package.json ⇒ dir is our project root.
    } catch {
      // keep searching
    }

    const parent = path.dirname(dir);
    if (parent === dir) {
      throw new Error("Unable to locate package.json");
    }
    dir = parent;
  }

  const sandboxExecutable = getLinuxSandboxExecutableForCurrentArchitecture();
  const candidate = path.join(dir, "bin", sandboxExecutable);
  try {
    await fs.promises.access(candidate, fs.constants.X_OK);
  } catch {
    throw new Error(`${candidate} not found or not executable`);
  }

  // Will throw if the executable is not working in this environment.
  await verifySandboxExecutable(candidate);
  return candidate;
}

const ERROR_WHEN_LANDLOCK_NOT_SUPPORTED = `\
The combination of seccomp/landlock that Codex uses for sandboxing is not
supported in this environment.

If you are running in a Docker container, you may want to try adding
restrictions to your Docker container such that it provides your desired
sandboxing guarantees and then run Codex with the
--dangerously-auto-approve-everything option inside the container.

If you are running on an older Linux kernel that does not support newer
features of seccomp/landlock, you will have to update your kernel to a newer
version.
`;

/**
 * Now that we have the path to the executable, make sure that it works in
 * this environment. For example, when running a Linux Docker container from
 * macOS like so:
 *
 * docker run -it alpine:latest /bin/sh
 *
 * Running `codex-linux-sandbox-x64 -- true` in the container fails with:
 *
 * ```
 * Error: sandbox error: seccomp setup error
 *
 * Caused by:
 *     0: seccomp setup error
 *     1: Error calling `seccomp`: Invalid argument (os error 22)
 *     2: Invalid argument (os error 22)
 * ```
 */
function verifySandboxExecutable(sandboxExecutable: string): Promise<void> {
  // Note we are running `true` rather than `bash -lc true` because we want to
  // ensure we run an executable, not a shell built-in. Note that `true` should
  // always be available in a POSIX environment.
  return new Promise((resolve, reject) => {
    const args = ["--", "true"];
    execFile(sandboxExecutable, args, (error, stdout, stderr) => {
      if (error) {
        log(
          `Sandbox check failed for ${sandboxExecutable} ${args.join(" ")}: ${error}`,
        );
        log(`stdout: ${stdout}`);
        log(`stderr: ${stderr}`);
        reject(new Error(ERROR_WHEN_LANDLOCK_NOT_SUPPORTED));
      } else {
        resolve();
      }
    });
  });
}

/**
 * Returns the absolute path to the architecture-specific Landlock helper
 * binary. (Could be a rejected promise if not found.)
 */
function getSandboxExecutable(): Promise<string> {
  if (!sandboxExecutablePromise) {
    sandboxExecutablePromise = detectSandboxExecutable();
  }

  return sandboxExecutablePromise;
}

/** @return name of the native executable to use for Linux sandboxing. */
function getLinuxSandboxExecutableForCurrentArchitecture(): string {
  switch (process.arch) {
    case "arm64":
      return "codex-linux-sandbox-arm64";
    case "x64":
      return "codex-linux-sandbox-x64";
    // Fall back to the x86_64 build for anything else – it will obviously
    // fail on incompatible systems but gives a sane error message rather
    // than crashing earlier.
    default:
      return "codex-linux-sandbox-x64";
  }
}