Web api token based authentication:- Failed to decode token from base64 string to get user name and password - authentication

Question

I am using Web Api Token Based Authentication using OWIN Middleware; the token is generated successfully but i can't decode it; e.g. i cannot extract user name and password from it;
Here is my configuration
my start up code
var oAuthAuthorizationServerOptions = new OAuthAuthorizationServerOptions
{
AllowInsecureHttp = true,
TokenEndpointPath = new PathString("/api/token"),
AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
Provider = new SimpleAuthorizationServerProvider()
};
// Token Generation
app.UseOAuthAuthorizationServer(oAuthAuthorizationServerOptions);
app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());
my code that is ued to send the token is
static async Task RunAsync(JObject token)
{
using (var client = new HttpClient())
{
client.Timeout = new TimeSpan(1000000000000);
client.BaseAddress = new Uri("http://localhost/SampleApp/");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(token["token_type"].ToString(),
token["access_token"].ToString());
}}
my authetication code
var authenticationSchema = httpContext.Request.Headers["Authorization"];
if (!String.IsNullOrWhiteSpace(authenticationSchema))
authentication = AuthenticationHeaderValue.Parse(authenticationSchema);
if (authentication != null)
{
var unencoded = Convert.FromBase64String(authentication.Parameter);
var userpw = Encoding.GetEncoding("iso-8859- 1").GetString(unencoded);
var creds = userpw.Split(':');
return new Tuple<string, string>(creds[0], creds[1]);
}
and the code failed when trying to decode the code from base64 string
note:- my sample token is
3K8vHKHA2ZsKfKbvzUbo4a2sat2JLzvvyxCZ0KSD6s1wUS3t3oDPXuQ89aTmGpsG4ZL8O0cr8M9EUeZGtdM6FBwR7gLFcLZkTaimFGKyyZMNce9trQavVTzs6gam6qach1rPTLv_gIYGgPmM-401PZsr89BIXw4acTpJL3KbXs8y7PQ-o-eTV2IA8euCVkqC02iEnAzmS0SwhBouISCC-HvcNpE2aNixg4JXEt8EslU
you can see the attached for the exception

Answer 1

As far as I can see from the code, access token is sent plain to server; but you need to encode the access token on the client side like:
client.DefaultRequestHeaders.Authorization =
new AuthenticationHeaderValue(token["token_type"].ToString(),
Convert.ToBase64String(Encoding.GetEncoding("iso-8859-1").GetBytes(token["access_token"].ToString())));
Then you can convert access token from base64 string on the server side. The access token string value you provided is not a valid Base64 string, so as expressed in the exception message.