AWS lambda function returns HTTP 403 when sending file via POST

Question

I'm migrating a small node/express app to lambda functions using serverless.

My app is really simple. No authentication. Just 1 endpoint, allowing GET and POST. The problem is GET works, but I'm getting HTTP error 403 when I send POST request sending a binary file (docx file)

var app = express();
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));
app.use(express.static(path.join(__dirname, 'public')));


/* GET home page. */
app.get('/', function (req, res, next) {
    res.render('index', {title: 'Whatever'});
});

/* POST receive file */
app.post('/', function (req, res, next) {
    // Simplified to the minimum
    return res.json({'msg': 'ok'});   
});

module.exports.handler = serverless(app);

My serverless.yml file looks like this

service: my_service

provider:
  name: aws
  runtime: nodejs8.10
  stage: dev
  region: eu-west-3

functions:
  app:
    handler: app.handler
    events:
      - http: GET /
      - http: 'ANY {proxy+}'
  post:
    handler: app.handler
    events:
      - http:
          path: /
          method: post
          cors: true

After running sls deploy, an Amazon API Gateway is created and the function is deployed, but can't use POST to send binary files to my app.

This is probably a problem with API Gateway, but couldn't fix it.

EDIT

The first response is the correct one, with just a small change in the serverless.yml file. This is the right one:

service: my-service

provider:
  name: aws
  runtime: nodejs8.10
  stage: dev
  region: eu-west-3

functions:
  app:
    handler: app.handler
    events:
      - http: GET /
      - http: POST /
      - http: 'ANY {proxy+}'

Answer 1

I think you are mixing up a few concepts:

• You only have one function. I am not sure why you are defining two on your serverless.yml file
• You have many methods under ONE function because you are delegating everything to express to handle.
• If you wanted to have multiple functions, every one mapped to a different HTTP method, then you would not need to use Express
• You are declaring PROXY, ANY, GET and POST, all under / (Although not sure, I think this is the root of your problem as API Gateway is getting lost on the routes). You don't need it if you're using Express as all you need is to proxy every single call.

With all of that said, you should modify your serverless.yml file accordingly:

service: my-service

provider:
  name: aws
  runtime: nodejs8.10
  stage: dev
  region: eu-west-3

functions:
  app:
    handler: app.handler
    events:
      - http: ANY /
      - http: 'ANY {proxy+}'

I have slightly changed your app.js file, but that was only to make it a little clearer to me, but you can always use it to compare against yours:

const serverless = require('serverless-http');
const express = require('express')
const app = express()
const bodyParser = require('body-parser');

app.use(bodyParser.json({ strict: false }));

/* GET home page. */
app.get('/', function (req, res, next) {
    res.json({title: 'Whatever'});
});

/* POST receive file */
app.post('/', function (req, res, next) {
    // Simplified to the minimum
    return res.json({'msg': 'ok'});   
});

module.exports.handler = serverless(app);

If you now deploy with sls deploy, you will be able to execute both methods successfully.

I have run both examples for you.

Issuing a GET results in:

And issuing a POST results in:

which is exactly what you are expecting.