SAML v2 Populate Lambda
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To customize the SAML response for a service provider, assign a lambda to a FusionAuth application that acts as a SAML Identity Provider (IdP). FusionAuth runs the lambda before FusionAuth sends the SAML response to the service provider.
When you create a lambda in the Admin UI, FusionAuth provides an empty function for you to implement.
Lambda Structure#
When you create the lambda with the API, give the function the following signature:
function populate(samlResponse, user, registration, context) {
// Lambda code goes here
}
The 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 parameter isnullwhen the user is not registered for the application. This object is read-only.context: Available since1.64.0an object containing the context of the request, including access to secrets. This object is read-only.
The User API and Registration API documentation describe the user and registration objects. The samlResponse object follows the structure of the XML document, without the DOM object model. The lambda can change the following fields 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#
After you create the lambda, assign the lambda to one or more Applications on the SAML tab of the Application configuration.
Example Lambdas#
Map Attributes for a Service Provider#
FusionAuth adds default attributes to the assertion, such as email, first_name, and the http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress form of each name. Many service providers expect their own attribute names instead. The following lambda replaces the default attributes with the names a service provider expects. The lambda leaves out an attribute when the user has no value for the attribute:
// replaces the default attributes with the names a service provider expects, and leaves out empty values
function populate(samlResponse, user, registration, context) {
var attributes = {};
function add(name, values) {
values = values.filter(function (value) {
return value !== undefined && value !== null && value !== '';
});
if (values.length > 0) {
attributes[name] = values;
}
}
add('User.Email', [user.email]);
add('User.FirstName', [user.firstName]);
add('User.LastName', [user.lastName]);
add('User.Department', [user.data.department]);
add('User.Groups', registration && registration.roles ? registration.roles : []);
samlResponse.assertion.attributes = attributes;
}SAML attributes can hold several values, so every attribute value is an array, even for a single value.
Send One Role#
Some service providers accept one role per user. For a lambda that picks one role from the user's roles, see the Zendesk integration.
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