I'm working on a site that needs to get webhook requests from external providers, for this the new "Dev Tunnels"-feature in Visual Studio is great. The problem is that Umbraco does not recognize the x-forwarded-host header which makes any absolute links point to https://localhost/ since that is what it's running as internally. I have a slight memory that there might be some "mechanism" in Umbraco that tells the CMS the current URL (so that I can use the headers from the proxy). Anyone knows?

There's the

UmbracoApplicationUrl

setting, but I'm not sure what it controls...

@Markus Johansson you can add something like this to your rewrite rules:

csharp
private static void RewriteHttpHost(RewriteContext context) {

    context.Result = RuleResult.ContinueRules;

    // Get a reference to the current request
    HttpRequest request = context.HttpContext.Request;

    // Get the host from the header
    string? proxyHost = request.Headers["x-forwarded-host"];
    if (!string.IsNullOrWhiteSpace(proxyHost)) return;

    // Update the HTTP host
    request.Host = new HostString(proxyHost);

}

Thanks @Anders Bjerner I have to give that a try! Is that wired up in during service registration? I noticed that the built-in UrlProvider is using HttpContext.Request directly - I'm guessing that this would basically fool the site to think that it's operating on a different host right?

Yes, Umbraco and other logic should see the "new" host instead

Great stuff! Thanks!

> Is that wired up in during service registration? For an Umbraco 10 site, I have this in my

Configure

method in `Startup.cs`:

csharp
app.UseRewriter(new RewriteOptions().Add(RewriteHttpHost));

The Umbraco 13 template doesn't have a

Startup.cs

, but it looks somewhat similar in

Program.cs

. I can see my coworker added it between

await app.BootUmbracoAsync();

and

app.UseUmbraco()

. I don't know if it makes any difference, but probably wouldn't hurt adding it before

await app.BootUmbracoAsync();

. https://cdn.discordapp.com/attachments/1222868066858438737/1222930014157406258/image.png?ex=66180154&is=66058c54&hm=9b2200ac47d37ff80605a97a46b54512ad889b89c9e52473a09f12b73f797a38&

Thanks man! Relly helpful! It works great! I ended up with this:

csharp
public class ProxyHostRewriteRule : Microsoft.AspNetCore.Rewrite.IRule
{
    public void ApplyRule(RewriteContext context)
    {
        context.Result = RuleResult.ContinueRules;

        // Get a reference to the current request
        HttpRequest request = context.HttpContext.Request;

        // Get the host from the header
        string? proxyHost = request.Headers["x-forwarded-host"];
        if (!string.IsNullOrWhiteSpace(proxyHost))
        {
            // Update the host
            request.Host = new HostString(proxyHost);
        }

        string? proxyScheme = request.Headers["x-forwarded-scheme"];
        if (!string.IsNullOrWhiteSpace(proxyScheme))
        {
            // Update the scheme (http/https)
            request.Scheme = proxyScheme;
        }

    }
}

and then during startup:

csharp
var rewriteOptions = new RewriteOptions();
rewriteOptions.Rules.Add(new ProxyHostRewriteRule());
app.UseRewriter(rewriteOptions);

Thanks a lot for helping out!