> For the complete documentation index, see [llms.txt](/docs/llms.txt)

# SAML v2 Reconcile Lambda | FusionAuth Docs

An overview of the SAML v2 Response Reconcile lambda.

# SAML v2 Reconcile Lambda

When an SAML v2 identity provider is used to complete a federated login request, FusionAuth will use the [configured linking strategy](/docs/lifecycle/authenticate-users/identity-providers/#linking-strategies) and well known SAML v2 attributes to reconcile the user. FusionAuth will attempt to match the user information returned from the SAML v2 identity provider to an existing user account or create a new one.

You may optionally utilize a lambda to customize the user and user registration during the authentication event.

It is common that the SAML attributes (claims) returned from the SAML IdP login request will contain custom attributes. In order to utilize these custom attributes you may wish to use a lambda to assist FusionAuth during the login request to copy these claims to appropriate fields on the FusionAuth user object.

When you create a new lambda using the FusionAuth administrative user interface, you will be provided an empty function to implement.

Starting in version 1.65.0, you can use [attribute mappings](/docs/lifecycle/authenticate-users/identity-providers/#attribute-mappings) to map IdP claims directly to FusionAuth user and registration fields without writing a lambda. Reconcile lambdas and attribute mappings are mutually exclusive. Attempting to configure both on a given IdP results in a validation error.

## Lambda Structure[#](#lambda-structure)

If you are using the API to create the lambda you will need to ensure your function has the following signature:

```
function reconcile(user, registration, samlResponse, context) {
  // Lambda code goes here
}
```

This lambda must contain a function named `reconcile` that accepts the following parameters:

*   `user` - the FusionAuth User object. You can modify this object. However, the **email** and **username** attributes may not be modified after the user has been linked.
*   `registration` - the FusionAuth UserRegistration object. You can modify this object.

*   `samlResponse` - the SAML v2 response object. This is read-only.
*   `context` - Available since 1.64.0 - an object containing the context of the request, including access to [secrets](/docs/extend/code/lambdas#secrets). This object is read-only.

The two FusionAuth objects are well documented here in the [User API](/docs/apis/users) and [Registration API](/docs/apis/registrations) documentation. The SAML response object mimics the format of the XML document, but is designed to be much simpler to use than dealing with the DOM object model. Here is a list of the fields you have access to manipulate in the SAML response:

### SAML Response Fields[#](#saml-response-fields)

`samlResponse.assertion.attributes`Map<String, List<String>>

A map of the attributes of the user. This is sometimes call the claims of the user. Since SAML attributes can be multi-valued, you will need to wrap single values in Arrays like this:

```
samlResponse.assertion.attributes['firstName'] = [user.firstName];
```

`samlResponse.assertion.conditions.audiences`Array<String>

A list of the audiences for this SAML response. By default, the `audience` or `issuer`, in that order, from the corresponding SAML identity provider configuration are used.

`samlResponse.assertion.conditions.notBefore`Long

The instant that this assertion starts being valid. This is the number of milliseconds since Epoch UTC.

`samlResponse.assertion.conditions.notOnOrAfter`Long

The instant that this assertion stops being valid. This is the number of milliseconds since Epoch UTC.

`samlResponse.assertion.issuer`String

The issuer of this SAML assertion. This defaults to the `issuer` from the corresponding SAML identity provider configuration.

`samlResponse.assertion.subject.nameID.format`StringDEPRECATED

The `NameID` format for the id of the subject (user). FusionAuth uses the `emailaddress` format specified by the SAML specifications. It is not recommended that you change this unless you know what you are doing.

Removed in 1.28.0

`samlResponse.assertion.subject.nameID.id`StringDEPRECATED

The `NameID` id of the subject (user). This defaults to the user's email address. It is not recommended that you change this unless you know what you are doing.

Removed in 1.28.0

`samlResponse.assertion.subject.nameIDs`ArrayAvailable since 1.28.0

The list of NameId objects.

Prior to version `1.28.0`, this field was a single entry but has since been converted to an array.

`samlResponse.assertion.subject.nameIDs[x].format`StringAvailable since 1.28.0

The `NameID` format for the id of the subject (user). FusionAuth uses the `urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress` format specified by the SAML specifications by default. It is not recommended that you change this unless you know what you are doing.

`samlResponse.assertion.subject.nameIDs[x].id`StringAvailable since 1.28.0

The `NameID` id of the subject (user). This defaults to the user's email address. It is not recommended that you change this unless you know what you are doing.

`samlResponse.assertion.subject.confirmation.inResponseTo`String

This is the ID from the SAML request. It is not recommended that you change this unless you know what you are doing.

`samlResponse.assertion.subject.confirmation.method`String

The confirmation method FusionAuth uses for the subject (user). This default to `Bearer`. It is not recommended that you change this unless you know what you are doing.

`samlResponse.assertion.subject.confirmation.notBefore`Long

The instant that this assertion's subject starts being valid. This is the number of milliseconds since Epoch UTC.

`samlResponse.assertion.subject.confirmation.notOnOrAfter`Long

The instant that this assertion's subject stops being valid. This is the number of milliseconds since Epoch UTC.

`samlResponse.assertion.subject.confirmation.recipient`String

The recipient of the subject. This defaults to the callback URL (ACS).

`samlResponse.assertions`ArrayAvailable since 1.60.0

An array containing all assertions on the SAML response. You can use this array to inspect the original assertions on the response instead of the combined **assertion**.

`samlResponse.destination`String

The destination of the SAML response. This defaults to the callback URL (ACS).

`samlResponse.id`String

A unique identifier for the SAML response that is generated by FusionAuth.

`samlResponse.inResponseTo`String

This is the ID from the SAML request. It is not recommended that you change this unless you know what you are doing.

`samlResponse.issueInstant`Long

The instant that this assertion was created. This is the number of milliseconds since Epoch UTC.

`samlResponse.issuer`String

This is the issuer of the SAML response. This defaults to the name of this FusionAuth deployment.

`samlResponse.status.code`String

The status code of the SAML response. Whenever the lambda is called, this will always be `Success`.

`samlResponse.status.message`String

The status message of the SAML response. Whenever the lambda is called, this will always be `null`.

## Assigning The Lambda[#](#assigning-the-lambda)

Once a lambda is created, you may assign it to one or more SAML v2 IdPs in the IdP configuration.

Navigate to Settings -> Identity Providers and select your existing a SAML v2 configuration or click Add provider and select SAML v2 if it has not yet been configured.

## Example Lambda[#](#example-lambda)

Here is an example of a simple Lambda that sets roles and attributes on the FusionAuth user from the SAML v2 response.

```
function reconcile(user, registration, samlResponse) {
  // Assign the roles to the user from the SAML attribute named 'roles'
  registration.roles = samlResponse.assertion.attributes['roles'] || [];
  // Set Assign a custom attribute from the SAML attribute named 'favoriteColor'
  registration.data.favoriteColor = samlResponse.assertion.attributes['favoriteColor'];

  // Create an event log of type 'Debug' when the lambda has debug logging enabled
  console.debug('FusionAuth reconciled a User from a SAML v2 IdP and I helped!');
}
```

During development if you want to get a better idea of what your IdP is returning in the `samlResponse` object, you may print the contents of this object to the Event Log to help you write the lambda. Add the following line of code to your lambda to dump the entire object to an informational event log.

```
// Pretty print the samlResponse object to the Event Log
console.info(JSON.stringify(samlResponse, null, 2));
```