Content-type Header Not Handled Correctly for JSON and Form Data with Charset Information

[ManuelLoaizaVasquez]

Description

In the file bodyDecoder-middleware.js, lines 47-53, the server incorrectly handles Content-type: application/json; charset=utf-8 headers and similarly formatted headers for form data (application/x-www-form-urlencoded). The existing code uses strict string comparison, causing issues when the Content-type header contains additional properties like charset.

Existing Code

// bodyDecoder-middleware.js, lines 47-53
if (contentType === 'application/json') {
  bodyData = JSON.stringify(req.body);
}

if (contentType === 'application/x-www-form-urlencoded') {
  bodyData = queryString.stringify(req.body);
}

This code only works for requests that send a pure Content-type: application/json or Content-type: application/x-www-form-urlencoded without any additional properties like charset.

Expected behavior

The code should be able to handle Content-type headers with additional parameters.

Standard Practice According to MDN

According to MDN's documentation on Content-Type, the header can contain additional parameters (like charset), separated by a semicolon. Therefore, using startsWith would align better with this standard practice.

Solution

A possible solution is to change the string comparison to check if the Content-type starts with the desired value. Below is the proposed change:

if (contentType.startsWith('application/json')) {
  bodyData = JSON.stringify(req.body);
}

if (contentType.startsWith('application/x-www-form-urlencoded')) {
  bodyData = queryString.stringify(req.body);
}

Steps to Reproduce

1. Send a POST request with a Content-type: application/json; charset=utf-8 header and JSON payload.
2. Observe that the existing code does not handle the body as expected.

Thank you for taking the time to look into this issue.