Unknown authentication scheme on LinkedIn API

Question

I'm using OAuth 1.0a for LinkedIn API. Currently, I've already implemented some calls for getting the profile and connections and they all seem to work fine. But for sending a message, the oauth library throws an exception with the following:

{
  "errorCode": 0,
  "message": "Unknown authentication scheme",
  "requestId": "I2Y0MFJ8ME",
  "status": 401,
  "timestamp": 1378376573339
}

I'm using PHP PECL OAuth. I'm initializing the $oauth object like this:

$oauth = new OAuth(API_KEY, API_SECRET, OAUTH_SIG_METHOD_HMACSHA1, OAUTH_AUTH_TYPE_FORM);
$oauth->setToken(ACCESS_TOKEN, SECRET);

and making the rest call like this:

$url = 'https://api.linkedin.com/v1/people/~/mailbox?format=json';
$content_type = array('Content-Type' => 'application/json');
$oauth->fetch($url, $message, OAUTH_HTTP_METHOD_POST, $content_type);

and $message looks something like this:

$message = Array
(
    [recipients] => Array
        (
            [0] => z2222117O
        )

    [subject] => this is my title
    [body] => this is my body
    [format] => json
    [id] => EAS123123
)

It doesn't look like there's anything wrong with the request. I've followed the instructions from the LinkedIn messaging docs. Anyone else had the same problem? Thanks in advance.

Answer 1

Some questions on the LinkedIn forums seem to indicate that the error you're getting means that you don't have a valid authentication token.

Are you sure you're sending a correct and active auth token with your message?

Answer 2

I have answer the question on the below link, seems the same error. Though it seems different technology, but solution would be same to send the access_token in request back to get the protected resources.

The link for your reference. Apache Oltu Linkedin Integration example

Answer 3

LinkedIn requires you to either set the access token in the header or as a query param with the non-standard name of oauth2_access_token. When I sent it as a query param with the name access_token, I got the error you did.