> For the complete documentation index, see [llms.txt](https://webauthn-doc.spomky-labs.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://webauthn-doc.spomky-labs.com/v5.2/symfony-bundle/advanced-behaviors/dealing-with-localhost.md).

# Cross Origin Authentication

Please [refer to this page](/v5.2/pure-php/advanced-behaviours/dealing-with-localhost.md) to know more about the Cross Origin Authentication.

## Configuration

The configuration of the allowed domains can be done as follows.

{% code title="config/packages/webauthn.yaml" lineNumbers="true" %}

```yaml
webauthn:
    allowed_origins:
        - 'https://acme.com'
        - 'https://acme.fr'
        - 'android:apk-key-hash://your-app-hash'
        - 'ios:bundle-id://your.bundle.id'
    allow_subdomains: true
```

{% endcode %}

## Top Origin Validation (Cross-Origin iframes)

If your authentication page is embedded in a cross-origin iframe, you can enable top origin validation by registering a service that implements `Webauthn\CeremonyStep\TopOriginValidator`.

When a `TopOriginValidator` service is available in the container, it is automatically used for both creation and request ceremonies.

{% code title="src/Security/MyTopOriginValidator.php" lineNumbers="true" %}

```php
<?php

declare(strict_types=1);

namespace App\Security;

use Webauthn\CeremonyStep\TopOriginValidator;
use Webauthn\Exception\AuthenticatorResponseVerificationException;

final readonly class MyTopOriginValidator implements TopOriginValidator
{
    public function validate(string $topOrigin): void
    {
        $allowed = [
            'https://app.example.com',
            'https://dashboard.example.com',
        ];
        if (!in_array($topOrigin, $allowed, true)) {
            throw AuthenticatorResponseVerificationException::create(
                'The top origin is not allowed.'
            );
        }
    }
}
```

{% endcode %}

{% hint style="info" %}
If no `TopOriginValidator` service is registered, the top origin is not validated. See [the pure PHP documentation](/v5.2/pure-php/advanced-behaviours/dealing-with-localhost.md#top-origin-validation-cross-origin-iframes) for more details.
{% endhint %}

## Allowed Origins Endpoint

When the allowed\_origins parameter is set, the path `/.well-known/webauthn` is enabled. This path returns a `JSON` object with allowed domains.


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