aws-sdk send request with IAM Auth - amazon-web-services

Question

I would like to make my Lambda function comunicate with a API Gateway...
However what I want is that the API Gateway checks the request with AWS_IAM... therefore the lambda function should in some way "sign" the request with a specific IAM token i suppose...
I was reading this https://docs.aws.amazon.com/general/latest/gr/signing_aws_api_requests.html, but I'm not able to find any example on how to sign the request with a specific IAM User
(I've already created a User in IAM with AmazonAPIGatewayInvokeFullAccess and I have both access key and secret key, so I suppose I really need only the "how to sign the request")

Answer 1

We need to build regular nodejs request options with three additional parameters
service: "execute-api" for Api Gateway
region: "us-east-1" AWS Region.
body: postData , typically we pass body req.write, we also need it in options because it is needed for signing.
and finally the aws4.sign(...) is passed to request.
All .sign method does is adds 4 additional headers X-Amz-Content-Sha256, X-Amz-Security-Token, X-Amz-Date and Authorization
var aws4 = require("aws4");
var https = require("https");
const requestBody = { name: "test" };
var postData = JSON.stringify(requestBody);
var options = {
method: "POST",
hostname: "abcdefgh.execute-api.us-east-1.amazonaws.com",
path: "/qa",
headers: {
"Content-Type": "application/json",
},
service: "execute-api",
region: "us-east-1",
body: postData,
maxRedirects: 20,
};
const signedRequest = aws4.sign(options, {
secretAccessKey: "abcadefghijknlmnopstabcadefghijknlmnopst",
accessKeyId: "ABCDEFGHIJKLMNOPQRST",
sessionToken: "this is optional ==",
});
console.log(signedRequest);
var req = https.request(signedRequest, function (res) {
var chunks = [];
res.on("data", function (chunk) {
chunks.push(chunk);
});
res.on("end", function (chunk) {
var body = Buffer.concat(chunks);
console.log(body.toString());
});
res.on("error", function (error) {
console.error(error);
});
});
req.write(postData);
req.end();
since this call is made from lambda whole object with keys can be skipped and simply call aws4.sign(options), it should use from environment variables.