OAuth2 returns invalid_client error

Question

good day,

I'm having trouble with getting the access token. I've followed the guide here: http://developers.box.com/oauth/ and already get my client_id, client_secret, and set the redirect_uri on the App settings (OAuth2 parameters) section.

Here is the code for the file client.php

<?php
    $client_id = 'my_client_id_here'; //removed
    $post_url = 'https://www.box.com/api/oauth2/authorize';

    include 'includes/header.php';
?>
    <div id="content">
        <form action="<?php echo $post_url; ?>" type="POST" enctype="application/x-www-form-urlencoded">
            <input type="text" name="response_type" value="code">
            <input type="text" name="client_id" value="<?php echo $client_id; ?>">
            <input type="text" name="state" value="vexhax97td8xf_SomeTemporaryValueForTesting">
            <input type="submit">
        </form>
        <div id="response"></div>
    </div>

<?php
    include 'includes/footer.php';
?>

and here's code for the file something.php (this is where the redirect_uri will go)

<?php

$client_id =  'my_client_id_here'; //removed
$client_secret =  'my_client_secrect_here'; //removed
$post_url = 'https://www.box.com/api/oauth2/token';

$code = $_GET['code'];

include 'includes/header.php';

$fields_params = array(
        "grant_type" => 'authorization_code',
        "code" => $code,
        "client_id" => $client_id,
        "client_secret" => $client_secret
    );

$ch = curl_init(); 
curl_setopt($ch, CURLOPT_URL, $post_url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields_params);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Content-Type: application/json',
    'Accept: application/json'
));

$data = curl_exec($ch); 
curl_close($ch);

$json = json_decode($data, true);
var_dump($json);

?>
    <div id="content">
        <?php 
            //Nothing fancy, just for displaying passed values
            if (isset($_GET))
                var_dump($_GET); 

            if (isset($_POST))
                var_dump($_POST); 
        ?>
    </div>

<?php
    include 'includes/footer.php';
?>

...now what happens is,

1.) on the first step (client.php), there is a form there with submit button.

2.) After i clicked on the submit button, i get redirected to the Box' login page with the button "Authorize".

3.) after entering login details and allow granting access for my app. I now gets redirected to the redirect_uri that i've set on the App settings (something.php), where in this file, it will execute curl post to get an access token, but i get stuck at this part, the curl result returns with the error:

array(2) { ["error"]=> string(14) "invalid_client" ["error_description"]=> string(34) "The client credentials are invalid" }

I'm sure that I have entered my client_id and client_secret correctly which I've obtained from the App settings. And the url for the redirect_uri, is also SSL enabled.

Any solutions, ideas why this is happening?

Thank you for your help.

Answer 1

The problem is in the cURL headers you're setting something.php. Remove the Content-Type header. In fact, you can not set the headers at all - cURL will send the correctly encoded parameters and Box will return JSON data by default.

curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Accept: application/json'
));