ICloud.java

// Uses retrofit to generate an implementation
public interface ICloud {
    static String serviceProviderHeader = "X-Auth-Service-Provider";
    static String credentialsAuthorizationHeader = "X-Verify-Credentials-Authorization";

    @GET("/verify_credentials?provider=digits")
    void verifyCredentials(
            @Header(serviceProviderHeader) String serviceProvider,
            @Header(credentialsAuthorizationHeader) String authorization,
            @Query("id") long id,
            Callback<String> callback);

}

SessionManager.java

public class SessionManager {

    // ... //
    
    // region Session related
    public void verifySession(DigitsSession session, Callback callback) {
        TwitterAuthConfig authConfig = TwitterCore.getInstance().getAuthConfig();

        // Cast from AuthToken to TwitterAuthToken
        TwitterAuthToken authToken = (TwitterAuthToken)session.getAuthToken();

        OAuthSigning oAuthSigning = new OAuthSigning(authConfig, authToken);
        // First value should be the location we're querying to twitter. 
            // The second is the actual validation information
        Map<String, String> authHeaders = oAuthSigning.getOAuthEchoHeadersForVerifyCredentials();
        try {
            Cloud.verifyCredentials(
                    authHeaders.get(ICloud.serviceProviderHeader),
                    authHeaders.get(ICloud.credentialsAuthorizationHeader),
                    session.getId(),
                    callback);
        }
        catch (Exception e) {
            Log.e(LOG_TAG, e.getMessage().toString());
        }
    }
}

webhooks.js

// The webhooks module
var express = require('express')
    , _ = require('underscore');


/**
 *  Handles authorizing with Twitter
 */
function DigitsAuth(req, res) {
    // These are the input fields coming in
    var headers = [
        // The url we'll be making the twitter request to
        'X-Auth-Service-Provider',
        // These are the credentials twitter will be verifying
        'X-Verify-Credentials-Authorization'
    ];

    // Check for any missing inputs
    var missingValues = _.reject(headers, function(val) {
        return req.get(val);
    });

    // Return an error if we don't have proper inputs
    if(missingValues.length > 0) {
        res.status(400).json({
            error: 'Auth information missing',
            missingInputs: missingValues
        });
        console.log('Missing values', missingValues);
        return;
    }

    // Send the request to twitter
    Parse.Cloud.httpRequest({
        method: 'GET',
        url: req.get(headers[0]),
        headers: {'Authorization': req.get(headers[1])},

        success: function(httpResponse) {
            var obj = JSON.parse(httpResponse.text);

            // TODO: Check for errors. Add to sessions table. Send JSON response
            res.status(httpResponse.status).send("success");
        },
        error: function(httpResponse) {
            res.status(400).json({
                error: 'Unable to make a twitter request'
            });
            console.log('Twitter error', httpResponse.text);
        }
    });
}

/** Setup Express **/
var app = express();
app.use(express.bodyParser());    // Middleware for reading request body
app.get('/verify_credentials', DigitsAuth);