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SAML v2 Populate Lambda

In order to handle complex integrations with SAML service providers, you can specify a lambda to be used by a FusionAuth application acting as SAML identity provider (IdP). This lambda will be invoked prior to the SAML response being sent back to the service provider.

When you create a new lambda using the FusionAuth UI we will provide you an empty function for you to implement.

Lambda Structure

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

function populate(samlResponse, user, registration) {
  // Lambda code goes here
}

This lambda must contain a function named populate that takes three parameters. The parameters that the lambda is passed are:

  • samlResponse - the SAML v2 response object. You can modify this object.
  • user - the FusionAuth User object. This object is read-only.
  • registration - the FusionAuth UserRegistration object. This object is read-only.

The two FusionAuth objects are well documented in the User API and Registration API 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

samlResponse.assertion.attributesMap<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.audiencesArray<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.notBeforeLong

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

samlResponse.assertion.conditions.notOnOrAfterLong

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

samlResponse.assertion.issuerString

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

samlResponse.assertion.subject.nameID.formatStringDEPRECATED

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.idStringDEPRECATED

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.nameIDsArrayAvailable 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].formatStringAvailable 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].idStringAvailable 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.inResponseToString

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.methodString

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.notBeforeLong

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

samlResponse.assertion.subject.confirmation.notOnOrAfterLong

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

samlResponse.assertion.subject.confirmation.recipientString

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

samlResponse.destinationString

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

samlResponse.idString

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

samlResponse.inResponseToString

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

samlResponse.issueInstantLong

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

samlResponse.issuerString

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

samlResponse.status.codeString

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

samlResponse.status.messageString

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

Assigning The Lambda

Once a lambda is created, you may assign it to one or more applications in the SAML configuration. See the SAML tab in the Application configuration.

Example Lambda

Here is an example of a simple Lambda that sets a few extra parameters into the SAML response from the User, including some custom data:

function populate(samlResponse, user, registration) {
  // Set an attribute named 'roles' from the User assigned roles for this registration
  samlResponse.assertion.attributes['roles'] = registration.roles || [];
  // Set an attribute named 'favoriteColor' using the custom data attribute named 'favoriteColor'
  samlResponse.assertion.attributes['favoriteColor'] = [user.data.favoriteColor];
}