Authenticate my web application with google oauth2

Question

I am trying to authenticate my web application with google oauth2. I am using vb.net as code behind.

At first step I added a hyperlink which redirect to https://accounts.google.com/o/oauth2/auth?scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fuserinfo.email+https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fuserinfo.profile&state=%2Fprofile&redirect_uri=http%3A%2F%2Flocalhost:2690%2Ftest1.aspx&response_type=code&client_id=XXX.apps.googleusercontent.com

Now after receiving code from code, I used code on page load of test1.aspx

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles    Me.Load
    If Not IsNullOrEmpty(Request.QueryString("code")) Then
                    Dim buffer As Byte() = Encoding.UTF8.GetBytes("code=" + Request.QueryString("code") + "&client_id=XXX.apps.googleusercontent.com&client_secret=XXX&redirect_uri=https%3A%2F%2Flocalhost:2690%2Ftest1.aspx&grant_type=authorization_code")     
        Dim req As HttpWebRequest = WebRequest.Create("https://accounts.google.com/o/oauth2/token")
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
        req.ContentLength = buffer.Length

        Dim strm As Stream = req.GetRequestStream()
        strm.Write(buffer, 0, buffer.Length)
        strm.Close()
        Try
            Dim res As HttpWebResponse = req.GetResponse()
            Response.Write(res.StatusDescription)
        Catch wex As WebException
            Response.Write(wex.Data.ToString + "<br/>" + wex.InnerException.ToString + "<br/>" + wex.Message + "<br/>" + wex.TargetSite.ToString)
        End Try


    End If
End Sub

Each time I am getting bad request error from server. Please help me to find out what I am doing wrong. I also tried to use dotnetopenauth but each example is using mvc and c# and I only know vb.net. Thanks for your help….

breno breno · Accepted Answer · 2013-01-19T05:19:28

Is this code URLencoding the values in the body of the POST request.

Also keep in mind that the code is to be exchanged once for tokens.

Authenticate my web application with google oauth2

1 Answers