I am trying to build a web app that accesses Google Analytics API, and pull data. However, I have having some issues with the OAuth 2.0 authorization.
It allows for successful initial access, but it quickly kicks me out and throws a Google_Auth_Exception with message 'Error fetching OAuth2 access token, message: 'invalid_grant'' when I hit a submit button that refreshes the page.
As I understand OAuth 2.0, there are 4 steps to authentication:
- Obtain OAuth 2.0 credentials from Google Dev Console
- Obtain an access token from Google Authorization Server
- Send the access token to Google Analytics API
- Refresh the access token, if necessary
And as I understand it, $client->setAccessToken(); automatically refreshes the token.
I cannot seem to find any documentation from Google since they moved to Github, and I have followed their example structures for the most part.
The error is thrown from the first try block, when it tries to execute $client->authenticate($_GET['code']);
My current workaround is to unset the session token, and have the user re-authorize. However, this is really cumbersome and intrusive, as any interaction with the page will ask for re-authorization.
Any help would be greatly appreciated!
Here is my code:
<?php
/**********************
OAUTH 2.0 AUTHORIZATION
***********************/
//required libraries
set_include_path("../src/" . PATH_SEPARATOR . get_include_path());
require_once 'Google/Client.php';
require_once 'Google/Service/Analytics.php';
//variables
$client_id = 'redacted';
$client_secret = 'redacted';
$redirect_uri = 'http://'.$_SERVER["HTTP_HOST"].$_SERVER['PHP_SELF'];
$dev_key = 'redacted';
//create a Google client
$client = new Google_Client();
$client->setApplicationName('App');
//sets client's API information
$client->setClientId($client_id);
$client->setClientSecret($client_secret);
$client->setRedirectUri($redirect_uri);
$client->setDeveloperKey($dev_key);
$client->setScopes(array('https://www.googleapis.com/auth/analytics.readonly'));
//if log out is requested, revoke the access
if (isset($_REQUEST['logout'])) {
unset($_SESSION['token']);
}
//check if authorization code is in the URL
try{
if (isset($_GET['code'])) {
$client->authenticate($_GET['code']); //does authorization work
$_SESSION['access_token'] = $client->getAccessToken(); //gets valid access token
$redirect = 'https://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF']; //set into session storage
header('Location: ' . filter_var($redirect, FILTER_SANITIZE_URL)); //cleans up the URL
}
}
//if the authorization code is now invalid
catch (Google_Auth_Exception $e) {
unset($_SESSION['token']); //unset the session token
echo "Token now invalid, please revalidate. <br>";
}
//if there is an access token in the session storage
if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {
$client->setAccessToken($_SESSION['access_token']); //set the client's access token
//try creating an analytics object
try {
$analytics = new Google_Service_Analytics($client);
echo 'Created Google Analytics Client successfully! <br><br>';
}
catch (Google_Auth_Exception $e) {
echo 'Need authorization!';
}
} else {
$authUrl = $client->createAuthUrl(); //create one
echo "<a class='login' href='$authUrl'><button>Authorize Google Access</button></a>"; //print button
}
I resolved the issue. I was trying to authorize the same authentication code twice, and therefore it returned an invalid_grant error.
My solution was to rewrite much of the code and fix the OAuth2 logic.
I have created a mini-tutorial of the OAuth2 authentication flow below:
<?php
session_start(); // Create a session
/**************************
* Google Client Configuration
*
* You may want to consider a modular approach,
* and do the following in a separate PHP file.
***************************/
/* Required Google libraries */
require_once 'Google/Client.php';
require_once 'Google/Service/Analytics.php';
/* API client information */
$clientId = 'YOUR-CLIENT-ID-HERE';
$clientSecret = 'YOUR-CLIENT-SECRET-HERE';
$redirectUri = 'http://www.example.com/';
$devKey = 'YOUR-DEVELOPER-KEY-HERE';
// Create a Google Client.
$client = new Google_Client();
$client->setApplicationName('App'); // Set your app name here
/* Configure the Google Client with your API information */
// Set Client ID and Secret.
$client->setClientId($clientId);
$client->setClientSecret($clientSecret);
// Set Redirect URL here - this should match the one you supplied.
$client->setRedirectUri($redirectUri);
// Set Developer Key and your Application Scopes.
$client->setDeveloperKey($devKey);
$client->setScopes(
array('https://www.googleapis.com/auth/analytics.readonly')
);
/**************************
* OAuth2 Authentication Flow
*
* You may want to consider a modular approach,
* and do the following in a separate PHP file.
***************************/
// Create a Google Analytics Service using the configured Google Client.
$analytics = new Google_Service_Analytics($client);
// Check if there is a logout request in the URL.
if (isset($_REQUEST['logout'])) {
// Clear the access token from the session storage.
unset($_SESSION['access_token']);
}
// Check if there is an authentication code in the URL.
// The authentication code is appended to the URL after
// the user is successfully redirected from authentication.
if (isset($_GET['code'])) {
// Exchange the authentication code with the Google Client.
$client->authenticate($_GET['code']);
// Retrieve the access token from the Google Client.
// In this example, we are storing the access token in
// the session storage - you may want to use a database instead.
$_SESSION['access_token'] = $client->getAccessToken();
// Once the access token is retrieved, you no longer need the
// authorization code in the URL. Redirect the user to a clean URL.
header('Location: '.filter_var($redirectUri, FILTER_SANITIZE_URL));
}
// If an access token exists in the session storage, you may use it
// to authenticate the Google Client for authorized usage.
if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {
$client->setAccessToken($_SESSION['access_token']);
}
// If the Google Client does not have an authenticated access token,
// have the user go through the OAuth2 authentication flow.
if (!$client->getAccessToken()) {
// Get the OAuth2 authentication URL.
$authUrl = $client->createAuthUrl();
/* Have the user access the URL and authenticate here */
// Display the authentication URL here.
}
/**************************
* OAuth2 Authentication Complete
*
* Insert your API calls here
***************************/
in my case it was problem of reauthentication. I was testing the api and got the code. To get the access token i had to revoke the access from account section->security->apps connected. Now select you app name and remove it. now try it and you will get the token response.
Error was : Uncaught exception 'Google_Auth_Exception' with message 'Error fetching OAuth2 access token, message: 'invalid_grant: Code was already redeemed
After added
header('Location: '.filter_var($redirectUri, FILTER_SANITIZE_URL));
I got error message Invalid Request Parameter. How to solve it?
来源：https://stackoverflow.com/questions/23498104/why-do-i-keep-catching-a-google-auth-exception-for-invalid-grant