Auth0 refresh token in React Native fails with 401 - react-native

Question

In my React Native app -- init app not Expo -- I'm trying to refresh the access_token but my POST call is failing with 401. I'm testing this functionality so I make the POST call some 30 seconds after I login so not sure if this plays a role or not.
In my initial login, I do get a refresh_token along with a valid access_token. I then tell my app to wait 30 seconds and make a POST call that looks like this:
const url = 'https://mydomain.auth0.com/oauth/token';
const postOptions = {
method: 'POST',
url: url,
headers: {
"content-type": 'application/x-www-form-urlencoded'
},
form: {
grant_type: 'refresh_token',
client_id: 'MY_CLIENT_ID',
refresh_token: 'REFRESH_TOKEN_RECEIVED_DURING_LOG_IN'
}
};
fetch(url, postOptions)
.then((response) => {
debugger;
// this is where I get response.status 401
})
Any idea what the issue is here?
Also want to mention that under my application settings, Refresh Token is checked under "Grant Types" but refresh token rotation or expiration are NOT enabled.

Answer 1

I figured this out and sharing it in case others need it in the future.
First, Auth0 documentation is misleading at best. They keep mentioning a regular POST call which doesn't work.
In my React Native app, I use their react-native-auth0 library. This library does offer a refreshToken() method which is what I ended up using.
Before I share the code, here are a couple of really important points:
Be sure to include offline_access in the scope of your initial authentication call for the user. Without including offline_access in your scope, you won't get a refresh_token. Once you receive it along with your access_token and id_token, store it as you'll use it many times. This brings me to the second point.
Unless you set it otherwise, your refresh_token doesn't expire. Therefore, store it some place secure and NOT just in AsyncStorage. As mentioned above, unless, you set it otherwise or it gets revoked, your refresh_token doesn't expire and you use it again and again.
With that said, here's the code. Please keep in mind that at start up, I initialize auth0 as a global variable so that I can access it in different parts of my app.
Here's what my initialization looks like in index.js:
import Auth0 from 'react-native-auth0';
global.auth0 = new Auth0({
domain: "MY_DOMAIN.auth0.com",
clientId: "MY_CLIENT_ID",
});
And here's how I use the refreshToken() method:
// First, retrieve the refresh_token you stored somewhere secure after your initial authentication call for the user
global.auth0.auth.refreshToken({ refreshToken: 'MY_REFRESH_TOKEN' })
.then(result => {
// If you're doing it right, the result will include a new access_token
})

Answer 2

you probably need to add the authorization header with your access_token:
const url = 'https://mydomain.auth0.com/oauth/token';
const postOptions = {
method: 'POST',
url: url,
headers: {
"content-type": 'application/x-www-form-urlencoded',
"Authorization" 'bearer '+access_token,
},
body: JSON.stringify({
grant_type: 'refresh_token',
client_id: 'MY_CLIENT_ID',
refresh_token: 'REFRESH_TOKEN_RECEIVED_DURING_LOG_IN'
});
};
fetch(url, postOptions)
.then((response) => {
debugger;
// this is where I get response.status 401
})