# Policies

## Concept

Policies are functions which have the ability to execute specific logic on each request before it reaches the controller's action. They are mostly used for securing business logic easily.
Each route of the project can be associated to an array of policies. For example, you can create a policy named `isAdmin`, which obviously checks that the request is sent by an admin user, and use it for critical routes.

### Where are the policies defined?

The policies are defined in each `./api/**/config/policies/` folders and plugins. They are respectively exposed through `strapi.api.**.config.policies` and `strapi.plugins.**.config.policies`. The global policies are defined at `./config/policies/` and accessible via `strapi.config.policies`.

## How to create a policy?

There are several ways to create a policy.

- Using the CLI `strapi generate:policy isAuthenticated`.<br>Read the [CLI documentation](../cli/CLI.md) for more information.
- Manually create a JavaScript file named `isAuthenticated.js` in `./config/policies/`.

**Path —** `./config/policies/isAuthenticated.js`.

```js
module.exports = async (ctx, next) => {
  if (ctx.state.user) {
    // Go to next policy or will reach the controller's action.
    return await next();
  }

  ctx.unauthorized(`You're not logged in!`);
};
```

In this example, we are verifying that a session is open. If it is the case, we call the `next()` method that will execute the next policy or controller's action. Otherwise, a 401 error is returned.

## Usage

To apply policies to a route, you need to associate an array of policies to it. There are two kinds of policies: global and scoped.

::: warning
To apply policies with GraphQL please see the [following guide](../plugins/graphql.md#execute-a-policy-before-a-resolver).
:::

### Global policies

The global policies can be associated to any route in your project.

**Path —** `./api/restaurant/routes.json`.

```json
{
  "routes": [
    {
      "method": "GET",
      "path": "/restaurants",
      "handler": "Restaurant.find",
      "config": {
        "policies": ["global::isAuthenticated"]
      }
    }
  ]
}
```

Before executing the `find` action in the `Restaurant.js` controller, the global policy `isAuthenticated` located in `./config/policies/isAuthenticated.js` will be called.

::: tip
You can put as much policy as you want in this array. However be careful about the performance impact.
:::

### Plugins policies

Plugins can add and expose policies into your app. For example, the plugin **Users & Permissions** comes with useful policies to ensure that the user is well authenticated or has the rights to perform an action.

**Path —** `./api/restaurant/config/routes.json`.

```json
{
  "routes": [
    {
      "method": "GET",
      "path": "/restaurants",
      "handler": "Restaurant.find",
      "config": {
        "policies": ["plugins::users-permissions.isAuthenticated"]
      }
    }
  ]
}
```

The policy `isAuthenticated` located in the `users-permissions` plugin will be executed before the `find` action in the `Restaurant.js` controller.

### API policies

The API policies can be associated to the routes defined in the API where they have been declared.

**Path —** `./api/restaurant/config/policies/isAdmin.js`.

```js
module.exports = async (ctx, next) => {
  if (ctx.state.user.role.name === 'Administrator') {
    // Go to next policy or will reach the controller's action.
    return await next();
  }

  ctx.unauthorized(`You're not allowed to perform this action!`);
};
```

**Path —** `./api/restaurant/config/routes.json`.

```json
{
  "routes": [
    {
      "method": "GET",
      "path": "/restaurants",
      "handler": "Restaurant.find",
      "config": {
        "policies": ["isAdmin"]
      }
    }
  ]
}
```

The policy `isAdmin` located in `./api/restaurant/config/policies/isAdmin.js` will be executed before the `find` action in the `Restaurant.js` controller.

### Using a policy outside its api

To use a policy in another api you can reference it with the following syntax: `{apiName}.{policyName}`.

**Path —** `./api/category/config/routes.json`.

```json
{
  "routes": [
    {
      "method": "GET",
      "path": "/categories",
      "handler": "Category.find",
      "config": {
        "policies": ["restaurant.isAdmin"]
      }
    }
  ]
}
```

## Advanced usage

As it's explained above, the policies are executed before the controller's action. It looks like an action that you can make `before` the controller's action. You can also execute a logic `after`.

**Path —** `./config/policies/custom404.js`.

```js
module.exports = async (ctx, next) => {
  // Indicate to the server to go to
  // the next policy or to the controller's action.
  await next();

  // The code below will be executed after the controller's action.
  if (ctx.status === 404) {
    ctx.body = 'We cannot find the resource.';
  }
};
```