SAML v2 Populate Lambda
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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, context) {
// Lambda code goes here
}
This lambda must contain a function named populate that accepts the following parameters:
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.context- Available since1.64.0- an object containing the context of the request, including access to secrets. 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.attributes 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 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 The instant that this assertion starts being valid. This is the number of milliseconds since Epoch UTC.
samlResponse.assertion.conditions.notOnOrAfter The instant that this assertion stops being valid. This is the number of milliseconds since Epoch UTC.
samlResponse.assertion.issuer The issuer of this SAML assertion. This defaults to the issuer from the corresponding SAML identity provider configuration.
samlResponse.assertion.subject.nameID.format 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.
1.28.0samlResponse.assertion.subject.nameID.id 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.
1.28.0samlResponse.assertion.subject.nameIDs 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 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 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 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 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 The instant that this assertion's subject starts being valid. This is the number of milliseconds since Epoch UTC.
samlResponse.assertion.subject.confirmation.notOnOrAfter The instant that this assertion's subject stops being valid. This is the number of milliseconds since Epoch UTC.
samlResponse.assertion.subject.confirmation.recipient The recipient of the subject. This defaults to the callback URL (ACS).
samlResponse.assertions 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 The destination of the SAML response. This defaults to the callback URL (ACS).
samlResponse.id A unique identifier for the SAML response that is generated by FusionAuth.
samlResponse.inResponseTo 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 The instant that this assertion was created. This is the number of milliseconds since Epoch UTC.
samlResponse.issuer This is the issuer of the SAML response. This defaults to the name of this FusionAuth deployment.
samlResponse.status.code The status code of the SAML response. Whenever the lambda is called, this will always be Success.
samlResponse.status.message 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];
}
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