Using Your Web Server as an Intermediary for OAuth2 Redirect to localhost.

If your OAuth2 provider does not allow "localhost" as a redirect URI, you can use your own public web server as an intermediary to receive the OAuth redirect and forward it to localhost.

How This Works

1. Your web server (e.g., "https://yourdomain.com/oauth-callback") is registered as the OAuth2 redirect URI.
2. Your application sets Chilkat.OAuth2.AppCallbackUrl = "https://yourdomain.com/oauth-callback" and Chilkat.OAuth2.ListenPort = 3017.
3. Your application calls Chilkat.StartAuth, which returns a URL for the browser and starts a background thread to capture the redirect with the code.
4. Your application launches a browser navigated to the URL. The user proceeds to grant authorization.
5. The OAuth provider sends the authorization code to your web server.
6. Your web server captures the code and redirects to your local machine, where Chilkat is waiting to receive the redirect in a background thread ("http://localhost:3017/callback?code=xyz").
7. Chilkat extracts the code and completes the OAuth2 flow.

Implementation

Register Your Public Server as the Redirect URI

• In your OAuth provider settings, set:

  https://yourdomain.com/oauth-callback

Implement the Redirecting Server

Your web server will:

• Receive the OAuth authorization code.
• Redirect the user to localhost while preserving the query parameters.

PHP Example

Here's an example using PHP:

1. Host this script on your public web server (e.g., "https://yourdomain.com/oauth-callback.php").
2. Register "https://yourdomain.com/oauth-callback.php" as your OAuth2 redirect URI.
3. Your server captures the code and redirects the user to localhost.

<?php
   header( 'Location: http://localhost:3017?' . $_SERVER['QUERY_STRING'] );
?>

Classic ASP Example

Here’s how you can implement the OAuth2 redirecting server in Classic ASP (VBScript).

1. Host this script on your public web server (e.g., "https://yourdomain.com/oauth-callback.asp").
2. Register "https://yourdomain.com/oauth-callback.asp" as your OAuth2 redirect URI in the OAuth provider settings.
3. Your server captures the code and redirects the user to localhost.

<%
' Get the authorization code from the query string
Dim authCode
authCode = Request.QueryString("code")
' Construct the localhost redirect URL
Dim localRedirectUrl
localRedirectUrl = "http://localhost:3017/callback?code=" & Server.URLEncode(authCode)
' Redirect the user to localhost with the authorization code
Response.Redirect localRedirectUrl
%>

ASP.NET Example

Here’s how you can implement the OAuth2 redirecting server in ASP.NET (C#).

1. Host this script on your public web server (e.g., "https://yourdomain.com/oauth-callback").
2. Register "https://yourdomain.com/oauth-callback" as your OAuth2 redirect URI in the OAuth provider settings.
3. Your server captures the code and redirects the user to localhost.

If you are using ASP.NET Core 6 or later, you can create a simple redirecting endpoint like this:

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet("/oauth-callback", (HttpContext context) =>
{
  string authCode = context.Request.Query["code"];
  string localRedirectUrl = $"http://localhost:3017/callback?code={Uri.EscapeDataString(authCode)}";
  return Results.Redirect(localRedirectUrl);
});
app.Run();

Node.js Example

Here's an example using Node.js (Express):

const express = require("express");
const app = express();
app.get("/oauth-callback", (req, res) => {
  const authCode = req.query.code;
  // Redirect to localhost with the code
  const localRedirect = "http://localhost:3017/callback?code=${encodeURIComponent(authCode)}";
  res.redirect(localRedirect);
});