Enable CORS in Golang callback function

Question

I have an AJAX call to Google's oAuth2 api looks like this:

$(document).on('click', '#signup', function() {
  var OAUTHURL        =  'https://accounts.google.com/o/oauth2/auth?';
  var SCOPE           =   'email profile';
  var STATE           =   'profile';
  var REDIRECT_URI    =   'https://localhost:8080/callback';
  var RESPONSE_TYPE   =   'token';
  var CLIENT_ID       =   '554886359117-8icq0dc9halr8rjd6bdtqcmagrdql9lr.apps.googleusercontent.com';
  var _url            =    OAUTHURL + 'scope=' + SCOPE + '&state=' + STATE + '&redirect_uri=' + REDIRECT_URI + '&response_type=' + RESPONSE_TYPE + '&client_id=' + CLIENT_ID;
  $.ajax({
    type: "POST",
    dataType: "text",
    url: _url,
    success: function(response)
    {
        console.log(response.url);
    },
    error: function(error)
    {
        console.log("ERROR: ", error);
    }
  });
});

This is supposed to redirect back to the server running on http://localhost/callback.

Redirect URIs:  http://localhost:8080/callback
Javascript Origins: http://localhost:8080

I also have the callback function defined as below:

func init() {
    r := mux.NewRouter()

    r.HandleFunc("/", rootHandler)
    r.HandleFunc("/callback", callbackHandler)
    http.Handle("/", r)
}
func callbackHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "I am sent back from the server!"+time.Now().Format("Mon, 02 Jan 2006 15:04:05 MST"))
}

everything looks good in debugging mode, except I get this error back from google's api:

XMLHttpRequest cannot load https://accounts.google.com/o/oauth2/auth?scope=email%20profile&state=profi…d=554886359117-8icq0dc9halr8rjd6bdtqcmagrdql9lr.apps.googleusercontent.com. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access.

I have tweaked a little around but I can't seem to find my way through. Any thought on this?

Henri · Accepted Answer · 2016-04-05 15:45:39Z

1

Like Not_a_Golfer said your backend is not setting correct headers to response. To handle CORS problem in every cases I made this little handler that wraps your router so you don't have to manually set headers in every callback.

Use it like this:

import "github.com/heppu/simple-cors"

func init() {
    r := mux.NewRouter()
    r.HandleFunc("/", rootHandler)
    r.HandleFunc("/callback", callbackHandler)
    http.Handle("/", cors.CORS(r))
}
func callbackHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "I am sent back from the server!"+time.Now().Format("Mon, 02 Jan 2006 15:04:05 MST"))
}

edited Apr 5, 2016 at 15:45

answered Feb 22, 2016 at 19:25

Henri

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Comments

Not_a_Golfer · Accepted Answer · 2015-04-02 08:47:56Z

0

Just add CORS headers to your callbackHandler:

// make this configurable via command line flags, env var, or something
var MyServerName = "https://localhost:8080" 

func callbackHandler(w http.ResponseWriter, r *http.Request) {
    w.Header().Add("Access-Control-Allow-Origin", MyServerName)

    fmt.Fprint(w, "I am sent back from the server!"+time.Now().Format("Mon, 02 Jan 2006 15:04:05 MST"))
}

answered Apr 2, 2015 at 8:47

Not_a_Golfer

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2 Comments

mehdix_ Over a year ago

I have played with it with different tricks, didn't really seem to solve the problem.

mehdix_ Over a year ago

My challenging question is if the problem is from the point where my AJAX call gets sent over the wire or is it my callback handler that fails to handle response from google?

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