expo Facebook.useAuthRequest validation error - facebook

Question

I am using "expo-auth-session" package for login to Facebook
SDK Version: 45
Platforms(Android/iOS/web/all): expo go and iOS
Code I got from the manual https://docs.expo.dev/guides/authentication/#facebook
import * as React from 'react';
import * as WebBrowser from 'expo-web-browser';
import * as Facebook from 'expo-auth-session/providers/facebook';
import { ResponseType } from 'expo-auth-session';
import { Button } from 'react-native';
WebBrowser.maybeCompleteAuthSession();
export default function App() {
const [request, response, promptAsync] = Facebook.useAuthRequest({
clientId: '<YOUR FBID>',
responseType: ResponseType.Code,
});
React.useEffect(() => {
if (response?.type === 'success') {
const { code } = response.params;
const fetchData = async () => {
const requestOptions = {
method: 'GET',
headers: {
"Content-Type": "application/json"
}
};
const link = "https://graph.facebook.com/v7.0/oauth/access_token" +
"?client_id=*******************" +
"&redirect_uri=https://auth.expo.io/#********/**********" +
"&client_secret=*******************" +
"&code=" + code;
const response = await fetch(link, requestOptions);
const body = await response.json();
console.log("fetchData response: => ", body);
}
fetchData().catch(console.error);
}
}, [response]);
return (
<Button
disabled={!request}
title="Login"
onPress={() => {
promptAsync();
}}
/>
);
}
So I am getting “Code” param from the api and then I should change it to “access token” with request like that
const link = "https://graph.facebook.com/v7.0/oauth/access_token" +
"?client_id=*******************" +
"&redirect_uri=https://auth.expo.io/#********/**********" +
"&client_secret=*******************" +
"&code=" + code;
Response:
{
"error": Object {
"code": 1,
"fbtrace_id": "A2avpevCrHdiCPhfadWl-S3",
"message": "Invalid code verifier. Code verifier should be a cryptographically random string using the characters A-Z, a-z, 0-9, and the punctuation characters -._~ (hyphen, period, underscore, and tilde), between 43 and 128 characters long.",
"type": "OAuthException",
},
}
How come it asking some verifier? Where should I get that param? I do not see anything like that in the manual.

Answer 1

I found the solution to this. In object request, you can find that "validator" param which was generated automatically. All you need resend it when getting token.
const link = "https://graph.facebook.com/oauth/access_token" +
"?client_id=*************" +
"&redirect_uri=*********************" +
"&client_secret=***********************" +
"&grant_type=authorization_code" +
"&code_verifier=" + request?.codeVerifier +
"&code=" + code;