Invalid Signature LinkedIn Oauth while getting access token

Question

I am trying dearly to add LinkedIn OAuth to a Phonegap application that I have created to allow users to automatically post to their LinkedIn public profile. I seem to be having trouble retrieving the access token from LinkedIn REST API via the Childbrowser plugin. To sign my REST API calls, I am using the OauthSimple plugin, in javascript.

When I send my signed POST to the REST API, I receive an 401 Unauthorized error. It specifies that I have an invalid signature and I can't figure out for the life of me what is wrong.

This is the json response I receive from LinkedIn when I make the request for the access token:

{"readyState":4,
"responseText":"oauth_problem=signature_invalid&
oauth_problem_advice=com.linkedin.security.auth.pub.LoginDeniedInvalidAuthTokenException%20
while%20obtaining%20request%20token%20for%20%3APOST%26
https%253A%252F%252Fapi.linkedin.com%252Fuas%252Foauth%252F
accessToken%26
oauth_consumer_key%253Dkivazo8r4xr3%2526
oauth_nonce%253D6ruTZ%2526
oauth_signature_method%253DHMAC-SHA1%2526
oauth_timestamp%253D1360525594%2526
oauth_token%253D0011aab8-0cf0-4555-ba44-304b34e4b636%2526
oauth_verifier%253D32140%2526
oauth_version%253D1.0,
"status":401,
"statusText":"Unauthorized"}

If you would like to have a look at my javascript, here are my functions:

function parametersFromUrl(url) {
    var result = {};
    //Remove everything up to where the parameters start. could be after # or after ?
    url = url.substr(url.indexOf('?') + 1).substr(url.indexOf('#') + 1)
    //Replace html escape characters
    url = url.replace(/%23/g, '#').replace(/%26/g, '&').replace(/%3D/g, '=');
    var parameters = url.split('&');
    for(var i = 0; i < parameters.length; i++) {
        var parameter = parameters[i].split('=');
        result[parameter[0]] = parameter[1];
    }
    return result;
}

/* -- Linkedin START -- */

var Linkedin = {
    init:function() {
        var signatures = { consumer_key: '555555', shared_secret: '555555' };
        var simple = new OAuthSimple(signatures.consumer_key, signatures.shared_secret);
        Linkedin.getRequestToken(simple, signatures);
    },
    getRequestToken:function(simple, signatures) {
        var result = simple.reset().sign({
            action: 'POST',
            path: 'https://api.linkedin.com/uas/oauth/requestToken',
            signatures: signatures
        });
        console.log(result);
        console.log(result.signed_url);
        jQuery.ajax({
            url: result.signed_url,
            type: 'POST',
            success: function(data) {
                jQuery.extend(signatures, parametersFromUrl(data));
                console.log(signatures['oauth_token']);
                Linkedin.childBrowserAuthenticate(simple, signatures);
            },
            error: function() {
                console.log('error');
            }
        });
    },
    childBrowserAuthenticate:function(simple, signatures) {
        ChildBrowser.install();
        var childBrowser = window.plugins.childBrowser;
        var browserUrl = simple.reset().sign({
            path: signatures['xoauth_request_auth_url']
        }).signed_url;
        browserUrl = browserUrl + '&oauth_token=' + signatures['oauth_token'];
        childBrowser.showWebPage(decodeURIComponent(browserUrl));

        function finish(err) {
            if (err) onFailure(err);
            childBrowser.onClose = null;
            childBrowser.close();
        }

        childBrowser.onLocationChange = function(loc) {
            if (loc.indexOf('oauth_problem') > -1) {
                finish('User authorization error');
            } else if (loc.indexOf('oauth_verifier') > -1) {
                alert('good');
                finish();
                $.each(signatures, function(i,item) {
                    console.log(i);
                    console.log(item);
                });
                console.log("next");
                params = parametersFromUrl(loc);
                jQuery.extend(signatures, params);
                $.each(signatures, function(i,item) {
                    console.log(i);
                    console.log(item);
                });
                Linkedin.getAccessToken(simple, signatures);
            }
        };

        childBrowser.onClose = function() {
            finish('User cancelled authorization.');
        };
    },
    getAccessToken:function(simple, signatures) {
        console.log("last");
        $.each(signatures, function(i,item) {
                    console.log(i);
                    console.log(item);
                });

        var requestUrl = simple.reset().sign({
            action: 'POST',
            path: 'https://api.linkedin.com/uas/oauth/accessToken',
            parameters: {
                'oauth_verifier': signatures.oauth_verifier,
                'oauth_token': signatures.oauth_token,
                'oauth_token_secret': signatures.oauth_token_secret,
                'oauth_version': "1.0"
            }
        }).signed_url;
        console.log(requestUrl);
        jQuery.ajax({
            url: requestUrl,
            type: 'POST',
            success: function(data) {
                jQuery.extend(signatures, parametersFromUrl(data));
                $.each(signatures, function(i,item) {
                    console.log(i);
                    console.log(item);
                });
                Linkedin.getUserProfile();
            },
            error: function(resp) {
                alert('crap');
                console.log(resp);
            }
        });
    },
    getUserProfile:function() {
        var result = simple.reset().sign({
            action: 'GET',
            path: 'https://api.linkedin.com/v1/people/~:(first-name,last-name,headline,picture-url)',
            parameters: {
                format: 'json'
            }
        });

        jQuery.ajax({
            url: result.signed_url,
            success: function(userData) {
                onSuccess(userData);
                alert('success');
                alert(userData);
            },
            error: function(resp) {
                onFailure('Failed to get profile information')
            }
        });
    }
};

/* -- Linkedin END -- */

When I make a request (POST) to LinkedIn REST API to get access token, my url looks like this:

https://api.linkedin.com/uas/oauth/accessToken?oauth_consumer_key=555555&oauth_nonce=KXuSN&oauth_signature=rk7eNjTxlhi0UOppOPfA%2BYvQ8uM%3D&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1360527087&oauth_token=206e2377-c790-49a6-839c-a996cadfbdfc&oauth_verifier=62355&oauth_version=1.0

I compared my oauth signature to the one generated by the Linkedin oauth console and they arent the same. What could be wrong?

I used this tutorial to guide me through the process.

If you need any more information, please let me know and I will add to my question.

Thank you so much!

Answer 1

So I found my answer! Since I am using Phonegap, I can make direct JSON calls to the API without a signature library. So I directly requested the Auth Code from the API using OAuth 2.0 with the values added to the url. Here is the link to the documentation.

https://developer.linkedin.com/documents/authentication

Answer 2

Why not use the Linkedin Javascript library? It does all the backend work for you, including signing requests. Place this in your header file.

<script type="text/javascript" src="http://platform.linkedin.com/in.js">
   api_key:    [API_KEY]
</script>

Then place this anywhere you need to show the sign-in button.

 <script type="in/Login"> Hello, <?js= firstName ?> <?js= lastName ?>. </script>