Owin, pass custom query parameters in Authentication Request

Question

We have our own OpenID Connect Provider. We want to pass custom query parameter in Authentication request using Owin middleware. And we cannot find the way how to implement

Answer 1

You're almost there! What's left is overriding built-in GoogleOAuth2AuthenticationProvider and here is the example how to do it:

class CustomGoogleAuthProvider : GoogleOAuth2AuthenticationProvider
{
    public CustomGoogleAuthProvider()
    {
        OnApplyRedirect = (GoogleOAuth2ApplyRedirectContext context) =>
        {
            IDictionary<string, string> props = context.OwinContext.Authentication.AuthenticationResponseChallenge.Properties.Dictionary;

            string newRedirectUri = context.RedirectUri;

            string[] paramertsToPassThrough = new[] { "login_hint", "hd", "anything" };

            foreach (var param in paramertsToPassThrough)
            {
                if (props.ContainsKey(param))
                {
                    newRedirectUri += string.Format("&{0}={1}", param, HttpUtility.UrlEncode(props[param]));
                }
            }

            context.Response.Redirect(newRedirectUri);
        };
    }
}

OWIN middleware registration:

app.UseGoogleAuthentication(new Microsoft.Owin.Security.Google.GoogleOAuth2AuthenticationOptions()
{
    // other config ...
    Provider = new CustomGoogleAuthProvider(),
});

The result (by the way with current version (3.0.1) of Google OAuth middleware login_hint flows from Authentication parameters out-of-the-box):

Answer 2

So, having struggled with a similar type of issue, brockallen sent me some code that gives me what I need using identity server 3....

class CustomGoogleAuthProvider : GoogleOAuth2AuthenticationProvider
{
    public CustomGoogleAuthProvider()
    {
        OnApplyRedirect = (GoogleOAuth2ApplyRedirectContext context) =>
        {
            var signinId = context.OwinContext.Request.Query["signin"];
            var msg = context.OwinContext.Environment.GetSignInMessage(signinId);
            var hint = msg.LoginHint;

            var newRedirectUri = context.RedirectUri;
            newRedirectUri += string.Format("&login_hint={0}", HttpUtility.UrlEncode(hint));

            context.Response.Redirect(newRedirectUri);
        };
    }
}