How to pass API Gateway authorizer context to a HTTP integration

Question

I have successfully implemented a Lambda authorizer for my AWS API Gateway, but I want to pass a few custom properties from it to my Node.js endpoint.

My output from my authorizer follows the format specified by AWS, as seen below.

{
  "principalId": "yyyyyyyy",
  "policyDocument": {
    "Version": "2012-10-17",
    "Statement": [
      {
        "Action": "execute-api:Invoke",
        "Effect": "Allow|Deny",
        "Resource": "arn:aws:execute-api:<regionId>:<accountId>:<appId>/<stage>/<httpVerb>/[<resource>/<httpVerb>/[...]]"
      }
    ]
  },
  "context": {
    "company_id": "123",
    ...
  }
}

In my case, context contains a few parameters, like company_id, that I would like to pass along to my Node endpoint.

If I was to use a Lambda endpoint, I understand that this is done with Mapping Template and something like this:

{
  "company_id": "$context.authorizer.company_id"
}

However, Body Mapping Template is only available under Integration Request if Lambda is selected as Integration type. Not if HTTP is selected.

In short, how do I pass company_id from my Lambda authorizer to my Node API?

Answer 1

Most of the credit goes out to @Michael-sqlbot in the comments to my question, but I'll put the complete answer here if someone else finds this question.

Authorizer Lambda

It has to return an object in this format, where context contains the parameters you want to forward to your endpoint, as specified in the question.

{
  "principalId": "yyyyyyyy",
  "policyDocument": {
    "Version": "2012-10-17",
    "Statement": [{
      "Action": "execute-api:Invoke",
      "Effect": "Allow|Deny",
      "Resource": "arn:aws:execute-api:<regionId>:<accountId>:<appId>/<stage>/<httpVerb>/[<resource>/<httpVerb>/[...]]"
    }]
  },
  "context": {
    "company_id": "123", <-- The part you want to forward
    ...
  }
}

Method Request

Under Method Request / HTTP Request Headers, add the context property you want to forward:

• Name: company_id
• Required: optional
• Cashing: optional

Integration Request

And under Integration Request / HTTP Headers, add:

• Name: company_id
• Mapped from: context.authorizer.company_id
• Cashing: optional

Answer 2

If you're using lamda-proxy, you can access the context from your event.requestContext.authorizer.context.

So your company_id can be accessed using event.requestContext.authorizer.context.company_id.