# Permissions

<!--introduced_in=v20.0.0-->

Permissions can be used to control what system resources the
Node.js process has access to or what actions the process can take
with those resources.

* [Process-based permissions](#process-based-permissions) control the Node.js
  process's access to resources.
  The resource can be entirely allowed or denied, or actions related to it can
  be controlled. For example, file system reads can be allowed while denying
  writes.
  This feature does not protect against malicious code. According to the Node.js
  [Security Policy][], Node.js trusts any code it is asked to run.

The permission model implements a "seat belt" approach, which prevents trusted
code from unintentionally changing files or using resources that access has
not explicitly been granted to. It does not provide security guarantees in the
presence of malicious code. Malicious code can bypass the permission model and
execute arbitrary code without the restrictions imposed by the permission
model.

If you find a potential security vulnerability, please refer to our
[Security Policy][].

## Process-based permissions

### Permission Model

<!-- YAML
added: v20.0.0
changes:
  - version:
    - v23.5.0
    - v22.13.0
    pr-url: https://github.com/nodejs/node/pull/56201
    description: This feature is no longer experimental.
-->

> Stability: 2 - Stable

The Node.js Permission Model is a mechanism for restricting access to specific
resources during execution.
The API exists behind a flag [`--permission`][] which when enabled,
will restrict access to all available permissions.

The available permissions are documented by the [`--permission`][]
flag.

The Permission Model has two operational modes:

* **Enforce mode** (default when using [`--permission`][]): Access is denied and
  an `ERR_ACCESS_DENIED` error is thrown for any operation the process has not
  been granted permission to perform.
* **Audit mode** (when using [`--permission-audit`][]): Permission checks are
  performed and violations are published through the diagnostics channel, but
  access is **not** denied. Execution continues normally. This mode is useful
  for discovering what permissions your application requires before deploying
  with enforce mode.

When starting Node.js with `--permission`,
the ability to access the file system through the `fs` module, access the network,
spawn processes, use `node:worker_threads`, use native addons, use WASI, use
FFI, and enable the runtime inspector will be restricted (the listener for
SIGUSR1 won't be created).

```console
$ node --permission index.js

Error: Access to this API has been restricted
    at node:internal/main/run_main_module:23:47 {
  code: 'ERR_ACCESS_DENIED',
  permission: 'FileSystemRead',
  resource: '/home/user/index.js'
}
```

Allowing access to spawning a process and creating worker threads can be done
using the [`--allow-child-process`][] and [`--allow-worker`][] respectively.

To allow network access, use [`--allow-net`][] and for allowing native addons
when using permission model, use the [`--allow-addons`][]
flag. For WASI, use the [`--allow-wasi`][] flag. For FFI, use the
[`--allow-ffi`][] flag. The [`node:ffi`](ffi.md) module also requires the
`--experimental-ffi` flag and is only available in builds with FFI support.

To allow use of OpenSSL STORE loaders, for example to load a private key
from a {URL} passed to [`crypto.createPrivateKey()`][], use the
[`--allow-openssl-store`][] flag.
This flag grants broad authority to configured OpenSSL STORE loaders, which may
access files, devices, tokens, or the network. Access performed by a loader is
not constrained by the `fs.read`, `fs.write`, or `net` permission scopes.

#### Runtime API

When enabling the Permission Model through the [`--permission`][]
or [`--permission-audit`][] flags, a new property `permission` is added to the
`process` object. This property contains the following functions:

##### `permission.has(scope[, reference])`

API call to check permissions at runtime ([`permission.has()`][])

```js
process.permission.has('fs.write'); // true
process.permission.has('fs.write', '/home/rafaelgss/protected-folder'); // true

process.permission.has('fs.read'); // true
process.permission.has('fs.read', '/home/rafaelgss/protected-folder'); // false
```

##### `permission.drop(scope[, reference])`

API call to drop permissions at runtime. This operation is **irreversible**.

When called without a reference, the entire scope is dropped. When called
with a reference, only the permission for that specific resource is revoked.
Dropping a permission only affects future access checks. It does not close or
revoke access to resources that are already open, such as file descriptors,
network sockets, child processes, or worker threads. Applications are
responsible for closing or terminating those resources when they are no longer
needed.

You can only drop the exact resource that was explicitly granted. The
reference passed to `drop()` must match the original grant. If a permission
was granted using a wildcard (`*`), only the entire scope can be dropped
(by calling `drop()` without a reference). If a directory was granted
(e.g. `--allow-fs-read=/my/folder`), you cannot drop individual files
inside it - you must drop the same directory that was originally granted.

```js
const fs = require('node:fs');

// Read config at startup while we still have permission
const config = fs.readFileSync('/etc/myapp/config.json', 'utf8');

// Drop read access to /etc/myapp after initialization
process.permission.drop('fs.read', '/etc/myapp');

// This will now throw ERR_ACCESS_DENIED
process.permission.has('fs.read', '/etc/myapp/config.json'); // false

// Drop child process permission entirely
process.permission.drop('child');
```

#### Audit Mode

The [`--permission-audit`][] flag enables audit mode for the Permission Model.
In audit mode, permission checks are performed but access is **not** denied —
no `ERR_ACCESS_DENIED` error is thrown. Instead, each permission violation is
published through the `node:diagnostics_channel` module, allowing the
application to observe and log which operations would be denied under enforce
mode. Execution continues normally.

Audit mode is useful for discovering what permissions your application
requires before deploying with [`--permission`][]. It can also be combined
with the [`--allow-fs-read`][], [`--allow-fs-write`][], [`--allow-net`][],
[`--allow-child-process`][], [`--allow-worker`][], [`--allow-addons`][],
[`--allow-wasi`][], and [`--allow-ffi`][] flags to audit a subset of
permissions while granting others.

When a permission check fails in audit mode, a message is published to the
diagnostics channel corresponding to the denied scope. The channel names are:

* `node:permission-model:fs` — File System (read and write)
* `node:permission-model:net` — Network
* `node:permission-model:child` — Child Process
* `node:permission-model:worker` — Worker Threads
* `node:permission-model:inspector` — Inspector
* `node:permission-model:wasi` — WASI
* `node:permission-model:addon` — Native Addons
* `node:permission-model:ffi` — FFI

Each message is an object with the following properties:

* `permission` {string} The name of the denied permission scope.
* `resource` {string} The resource that access was denied to (e.g. a file path
  or host).

```js
const diagnostics_channel = require('node:diagnostics_channel');

diagnostics_channel.channel('node:permission-model:fs').subscribe((msg) => {
  console.log(`Permission denied: ${msg.permission} on ${msg.resource}`);
});

// Running with --permission-audit, this publishes a diagnostics channel
// message but does not throw
const fs = require('node:fs');
fs.readFileSync('/etc/passwd');
```

If both [`--permission`][] and [`--permission-audit`][] are specified,
`--permission` takes precedence and the Permission Model runs in enforce mode.

#### File System Permissions

The Permission Model, by default, restricts access to the file system through the `node:fs` module.
It does not guarantee that users will not be able to access the file system through other means,
such as through the `node:sqlite` module.

To allow access to the file system, use the [`--allow-fs-read`][] and
[`--allow-fs-write`][] flags:

```console
$ node --permission --allow-fs-read=* --allow-fs-write=* index.js
Hello world!
```

By default the entrypoints of your application are included
in the allowed file system read list. For example:

```console
$ node --permission index.js
```

* `index.js` will be included in the allowed file system read list

```console
$ node -r /path/to/custom-require.js --permission index.js.
```

* `/path/to/custom-require.js` will be included in the allowed file system read
  list.
* `index.js` will be included in the allowed file system read list.

The valid arguments for both flags are:

* `*` - To allow all `FileSystemRead` or `FileSystemWrite` operations,
  respectively.
* Relative paths to the current working directory.
* Absolute paths.

Example:

* `--allow-fs-read=*` - It will allow all `FileSystemRead` operations.
* `--allow-fs-write=*` - It will allow all `FileSystemWrite` operations.
* `--allow-fs-write=/tmp/` - It will allow `FileSystemWrite` access to the `/tmp/`
  folder.
* `--allow-fs-read=/tmp/ --allow-fs-read=/home/.gitignore` - It allows `FileSystemRead` access
  to the `/tmp/` folder **and** the `/home/.gitignore` path.

Wildcards are supported too:

* `--allow-fs-read=/home/test*` will allow read access to everything
  that matches the wildcard. e.g: `/home/test/file1` or `/home/test2`

After passing a wildcard character (`*`) all subsequent characters will
be ignored. For example: `/home/*.js` will work similar to `/home/*`.

When the permission model is initialized, it will automatically add a wildcard
(\*) if the specified directory exists. For example, if `/home/test/files`
exists, it will be treated as `/home/test/files/*`. However, if the directory
does not exist, the wildcard will not be added, and access will be limited to
`/home/test/files`. If you want to allow access to a folder that does not exist
yet, make sure to explicitly include the wildcard:
`/my-path/folder-do-not-exist/*`.

#### Configuration file support

In addition to passing permission flags on the command line, they can also be
declared in a Node.js configuration file when using the experimental
\[`--experimental-config-file`]\[] flag. Permission options must be placed inside
the `permission` top-level object.

Example `node.config.json`:

```json
{
  "permission": {
    "allow-fs-read": ["./foo"],
    "allow-fs-write": ["./bar"],
    "allow-child-process": true,
    "allow-worker": true,
    "allow-net": true,
    "allow-addons": false,
    "allow-ffi": false,
    "allow-openssl-store": false
  }
}
```

When the `permission` namespace is present in the configuration file, Node.js
automatically enables the `--permission` flag. Run with:

```console
$ node --experimental-default-config-file app.js
```

#### Using the Permission Model with `npx`

If you're using [`npx`][] to execute a Node.js script, you can enable the
Permission Model by passing the `--node-options` flag. For example:

```bash
npx --node-options="--permission" package-name
```

This sets the `NODE_OPTIONS` environment variable for all Node.js processes
spawned by [`npx`][], without affecting the `npx` process itself.

**FileSystemRead Error with `npx`**

The above command will likely throw a `FileSystemRead` invalid access error
because Node.js requires file system read access to locate and execute the
package. To avoid this:

1. **Using a Globally Installed Package**
   Grant read access to the global `node_modules` directory by running:

   ```bash
   npx --node-options="--permission --allow-fs-read=$(npm prefix -g)" package-name
   ```

2. **Using the `npx` Cache**
   If you are installing the package temporarily or relying on the `npx` cache,
   grant read access to the npm cache directory:

   ```bash
   npx --node-options="--permission --allow-fs-read=$(npm config get cache)" package-name
   ```

Any arguments you would normally pass to `node` (e.g., `--allow-*` flags) can
also be passed through the `--node-options` flag. This flexibility makes it
easy to configure permissions as needed when using `npx`.

#### Permission Model constraints

There are constraints you need to know before using this system:

* The model does not inherit to a worker thread.
* When using the Permission Model the following features will be restricted:
  * Native modules
  * Network
  * Child process
  * Worker Threads
  * Inspector protocol
  * File system access
  * WASI
  * FFI
  * OpenSSL STORE loaders
* The Permission Model is initialized after the Node.js environment is set up.
  However, certain flags such as `--env-file` or `--openssl-config` are designed
  to read files before environment initialization. As a result, such flags are
  not subject to the rules of the Permission Model. The same applies for V8
  flags that can be set via runtime through `v8.setFlagsFromString`.
* OpenSSL engines cannot be requested at runtime when the Permission
  Model is enabled, affecting the built-in crypto, https, and tls modules.
* Run-Time Loadable Extensions cannot be loaded when the Permission Model is
  enabled, affecting the sqlite module.
* Using existing file descriptors via the `node:fs` module bypasses the
  Permission Model.

#### process.\_debugProcess() and cross-process Inspector activation

The `kInspector` permission scope restricts the current process from opening its own V8 Inspector. However,
process.\_debugProcess(pid) — which sends an OS-level signal (SIGUSR1 on POSIX, a remote thread on Windows)
to an external process — is not gated by the `kInspector` scope or any other Permission Model scope.

A sandboxed process running under --permission with no additional grants can call process.\_debugProcess(pid)
to force another Node.js process to open its V8 Inspector. The target process does not need to be running
under --permission for this to work — any Node.js process running on the same host under the same OS user
can be signaled.

This is consistent with the Node.js threat model: Node.js trusts the OS environment in which it runs.
Cross-process signaling is an operating-system-level capability; restricting it is the responsibility of
the operator (for example, using OS-level process isolation, separate OS users per process, or
seccomp/AppArmor profiles on Linux).

Developers relying on --permission to sandbox untrusted code should be aware that:

* process.\_debugProcess() is callable from any sandboxed process with no grants.
* If a target Node.js process is running on the same host under the same OS user, it can be forced to
  open its Inspector via this API.
* To prevent this, run sandboxed and target processes under different OS users, or use OS-level isolation
  mechanisms outside of Node.js.

#### Limitations and Known Issues

* Symbolic links will be followed even to locations outside of the set of paths
  that access has been granted to. Relative symbolic links may allow access to
  arbitrary files and directories. When starting applications with the
  permission model enabled, you must ensure that no paths to which access has
  been granted contain relative symbolic links.

[Security Policy]: https://github.com/nodejs/node/blob/main/SECURITY.md
[`--allow-addons`]: cli.md#--allow-addons
[`--allow-child-process`]: cli.md#--allow-child-process
[`--allow-ffi`]: cli.md#--allow-ffi
[`--allow-fs-read`]: cli.md#--allow-fs-read
[`--allow-fs-write`]: cli.md#--allow-fs-write
[`--allow-net`]: cli.md#--allow-net
[`--allow-openssl-store`]: cli.md#--allow-openssl-store
[`--allow-wasi`]: cli.md#--allow-wasi
[`--allow-worker`]: cli.md#--allow-worker
[`--permission-audit`]: cli.md#--permission-audit
[`--permission`]: cli.md#--permission
[`crypto.createPrivateKey()`]: crypto.md#cryptocreateprivatekeykey
[`npx`]: https://docs.npmjs.com/cli/commands/npx
[`permission.has()`]: process.md#processpermissionhasscope-reference
