> For the complete documentation index, see [llms.txt](https://docs.fortifiedid.se/access/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fortifiedid.se/access/key-components/authenticators/flow-control/chain.md).

# Chain

Configuration and usage guidance for Chain in Fortified ID Access.

## Introduction

The chain authenticator orchestrates one or more authenticators that perform(s) the actual authentication.

The chain is complete when all (required) authenticators in the chain are completed.

A chain authenticator can be nested with [Selector](/access/key-components/authenticators/flow-control/selector.md)s and other chains.

## Configuration

{% hint style="info" %}
**Authenticator type:** `Chain`
{% endhint %}

Common Authenticator configuration can be found [here](/access/key-components/authenticators/common-configuration.md).

{% tabs %}
{% tab title="Properties" %}

| Name               | Description                                                                                                                                                                                 | Default |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `base_path`        | The base path for this authenticator *and* used to construct paths for chained authenticators. (see [Routing](#routing))                                                                    |         |
| `exec_if`          | An expression that determines if this authenticator should be executed or not.                                                                                                              |         |
| `chain`            | List of [authenticator refs](#authenticator-refs) defining the content and order of the chain. An empty chain will block the authentication and therefore at least one ref must be present. | `[]`    |
| `require_subject`  | Flag controlling if this authenticator requires a subject to be set before completing. Use only for nested chains.                                                                          | `true`  |
| `proceed_on_error` | Flag controlling how chain behaves on authenticator failure. If enabled, all authenticators in chain will be executed before error is raised (stealth behaviour).                           | `true`  |
| `require_chain`    | Flag specifying if this authenticator must be executed inside a chain.                                                                                                                      | `false` |
| `verbose`          | Turns on extended trace logging. Use for troubleshooting only.                                                                                                                              | `false` |
| {% endtab %}       |                                                                                                                                                                                             |         |

{% tab title="Example" %}

```json
{
    "id" : "chain00",
    "type" : "Chain",
    "config" : {
      "base_path" : "/test/authn",
      "success_location" : "/authn/success.html",
      "failure_location" : "/authn/failure.html",
      "chain" : [ {
        "id" : "confirm00",
        "required" : true
      }, {
        "id" : "select00",
        "required" : true
      } ]
    }
  }
```

{% endtab %}
{% endtabs %}

### Authenticator refs

An authenticator ref points to an actual authenticator available in the current configuration.

{% tabs %}
{% tab title="Property" %}

<table data-full-width="true"><thead><tr><th>Name</th><th>Description</th><th>Default</th><th data-type="checkbox">Mandatory</th></tr></thead><tbody><tr><td><code>id</code></td><td>Authenticator id</td><td></td><td>true</td></tr><tr><td><code>required</code></td><td>Flag controlling if authenticator is required to complete or not. Authentication will fail if a required authenticator does not complete.</td><td><code>true</code></td><td>false</td></tr><tr><td><code>order</code></td><td>If ALL items have order numbers, these numbers define the execution order. If NO item has an order number, the order of the list defines the execution order.</td><td></td><td>false</td></tr></tbody></table>
{% endtab %}

{% tab title="Example" %}

```json
"chain" : [ 
  {
    "id" : "confirm00",
    "required" : true,
    "order": 0
  }, 
  {
    "id" : "select00",
    "required" : true,
    "order": 1
  }
 ]
```

{% endtab %}
{% endtabs %}

### Routing

When a chain is executed, the user agent is redirected to each chained authenticator in the specified (configured) order. The path to the authenticator is constructed by combining `base_path` with the chain authenticator's ID (specified as `id` in `authenticator_ref`).

Note that `base_path` is also used to generate the path for the current authenticator. This is intentional, as all authenticators in a flow must share the same path and session, both of which are managed by the path.

## API

API not available.


---

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