Incomplete Linkedin OAuth 2.0 access token response - oauth

Question

My question is about OAuth2 access token response from Linkedin api. When I'm trying to get this token I recieve the following response:
{"access_token":"...","expires_in":...}
But the thing is that according to OAuth2 documentation (in 5.1 paragraph) there should be at least one more required parameter - "token_type".
So the question is: could it be somehow customized so the linkedin API will return this parameter with access token response or it is just a departure from the rule and this parameter won't be returned?
Thanks in advance.

Answer 1

I have run into the same issue. According to LinkedIn Docs:
A successful Access Token request will return a JSON object containing the following fields:
access_token — The access token for the user. This value must be kept secure, as per your agreement to the API Terms of Use.
expires_in — The number of seconds remaining, from the time it was requested, before the token will expire. Currently, all access tokens are issued with a 60 day lifespan.
they respond with
{"access_token":"...","expires_in":...}
which violates the standard.
Currently I am using Spring Security 5.0.3 and to fix the issue, I had to monkeypatch one class:
com.nimbusds.oauth2.sdk.token.BearerAccessToken
I will not post the whole class, only a significant part:
public static BearerAccessToken parse(final JSONObject jsonObject)
throws ParseException {
// Parse and verify type
AccessTokenType tokenType;
try {
tokenType = new AccessTokenType(JSONObjectUtils.getString(jsonObject, "token_type"));
} catch (ParseException ex) {
tokenType = AccessTokenType.BEARER;
}
if (!tokenType.equals(AccessTokenType.BEARER))
throw new ParseException("Token type must be \"Bearer\"");
//...
}

Answer 2

I hoped to get answer from Linkedin member since they stated on their site that stackoverflow is a proper place for asking such questions. But since there is no answer from them and I didn't find any relevant information regarding this question I believe that it is just the way they implemented OAuth 2.0 protocol.