Slack OAuth HTTP Post Request returns "undefined" access token

Question

I'm using the following code in a simple slash command app to handle OAuth for public distribution of my app:

const express = require("express");
const bodyParser = require("body-parser");
const fetch = require("node-fetch")
require('dotenv').config();

const app = express();
app.use(bodyParser.urlencoded({ extended: true }));

// App installation handling
app.get("/auth", async (req, res) => {
    if (!req.query.code) {
        console.log("Access denied!");
        return;
    }
    var data = {form: {
        client_id: process.env.SLACK_CLIENT_ID,
        client_secret: process.env.SLACK_CLIENT_SECRET,
        code: req.query.code,
        redirect_uri: "https://6c0c-35-20-201-50.ngrok.io/auth"
    }};
    console.log(req.query.code);

    // Send received code back to Slack and get Oauth2 access token
    const config = {
        method: "POST",
        body: data,
        headers: {'Content-type': 'application/x-www-form-urlencoded'}
    };
    console.log("We got something!");
    try {
        const slack_oauth_response = await fetch("https://slack.com/api/oauth.v2.access", config);
        console.log("Access token granted!");
        console.log(JSON.stringify(slack_oauth_response.access_token));
    } catch (e) {
        console.error(e);
    }
    res.sendStatus(200);

})

When I try using the Add to Slack button, I get a timeout error. My log results will look like this:

PS D:\Documents\SlackRegApp> node local_testing.js
1007612862405.3292595223126.481b3e25d2c29dc80af7dc21bcb84a8bc19c28ddec155a429c6651105903902f
We got something!
Access token granted!
undefined // where the access token should be

If I go ahead and just log the entirety of slack_oauth_response, it looks like this:

{"size":0, "timeout":0}

When I try to install the app via cURL, it works, like below:

curl -F code=1007612862405.3292595223126.481b3e25d2c29dc80af7dc21bcb84a8bc19c28ddec155a429c6651105903902f -F client_id=**SLACK_CLIENT_ID** -F client_secret=**SLACK_CLIENT_SECRET** https://slack.com/api/oauth.v2.access

Hoping for some help here, thanks!

Answer 1

I just used the Slack WebClient API to access the oauth.v2.access method instead of trying to make my own HTTP request.