Custom Lambda with Nomad Media Authorizer

API Gateways in your AWS account can use the existing Nomad Media Authorizer Lambda to secure custom routes. When a request passes authentication, the authorizer injects four Nomad Media-specific attributes into the Lambda event context.

For instructions on attaching the Nomad Media Authorizer to your API Gateway, see Nomad Media Authorizer Setup.

Authorizer Attributes

Attribute	Type	Value
`isAuthd`	Boolean	`true` if the user passed authorization; `false` otherwise
`userId`	GUID	The unique Nomad Media user ID. This never changes, even if the user's email changes.
`name`	string	The first and last name of the user
`email`	string	The email address of the user

HTTP API Gateway Sample

Use the following as a starting point for custom Lambdas behind an HTTP API Gateway:

exports.handler = async (event, context) => {
    console.log("=========== event ===================");
    console.log(JSON.stringify(event));

    try {
        let requestContextObject = event.requestContext;

        let isAuthd = requestContextObject.authorizer.lambda.isAuthd;
        let userId  = requestContextObject.authorizer.lambda.userId;
        let name    = requestContextObject.authorizer.lambda.name;
        let email   = requestContextObject.authorizer.lambda.email;

        console.log(`isAuthd Parameter: ${isAuthd}`);
        console.log(`userId Parameter: ${userId}`);
        console.log(`name Parameter: ${name}`);
        console.log(`email Parameter: ${email}`);

        return "OK";

    } catch (error) {
        console.log(`Error: ${error}`);
    }
};

Example output:

INFO isAuthd Parameter: true
INFO userId Parameter: 83f15ca3-7e5c-4232-b4c9-57f5333d618a
INFO name Parameter: Test Account
INFO email Parameter: [email protected]

REST API Gateway Sample

For custom Lambdas behind a REST API Gateway, the authorizer context is accessed differently:

exports.handler = async (event) => {

    let requestContextObject = event.requestContext;

    let isAuthd = requestContextObject.authorizer.isAuthd;
    let userId  = requestContextObject.authorizer.userId;
    let name    = requestContextObject.authorizer.name;
    let email   = requestContextObject.authorizer.email;

    console.log(`isAuthd Parameter: ${isAuthd}`);
    console.log(`userId Parameter: ${userId}`);
    console.log(`name Parameter: ${name}`);
    console.log(`email Parameter: ${email}`);

    let responseBody = {
        message: "OK"
    };

    let response = {
        statusCode: 200,
        body: JSON.stringify(responseBody)
    };

    return response;
};

The key difference between HTTP and REST API Gateway: HTTP uses authorizer.lambda.* while REST uses authorizer.* directly on the request context.