In ASP.NET Core how do you check if request is local?

UPDATE: ASP.NET Core 2.0 has a method called Url.IsLocalUrl (see this Microsoft Docs).

I think this code will work, but I haven't been able to test it completely

var callingUrl = Request.Headers["Referer"].ToString();
var isLocal = Url.IsLocalUrl(callingUrl);

But see Will Dean's comment below about this approach:

Anyone thinking about using the 'updated' version which checks the Referrer header should bear in mind that headers are extremely easy to spoof, to a degree that doesn't apply to loopback IP addresses.

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Original solution

I came across this looking for a solution to knowing if a request is local. Unfortunately ASP.NET version 1.1.0 does not have a IsLocal method on a connection. I found one solution on a web site called Strathweb but that is out of date too.

I have created my own IsLocal extension, and it seems to work, but I can't say I have tested it in all circumstances, but you are welcome to try it.

public static class IsLocalExtension
{
    private const string NullIpAddress = "::1";

    public static bool IsLocal(this HttpRequest req)
    {
        var connection = req.HttpContext.Connection;
        if (connection.RemoteIpAddress.IsSet())
        {
            //We have a remote address set up
            return connection.LocalIpAddress.IsSet() 
                  //Is local is same as remote, then we are local
                ? connection.RemoteIpAddress.Equals(connection.LocalIpAddress) 
                  //else we are remote if the remote IP address is not a loopback address
                : IPAddress.IsLoopback(connection.RemoteIpAddress);
        }

        return true;
    }

    private static bool IsSet(this IPAddress address)
    {
        return address != null && address.ToString() != NullIpAddress;
    }
}

You call it in a controller action from using the Request property, i.e.

 public IActionResult YourAction()
 {
     var isLocal = Request.IsLocal();
     //... your code here
 }

I hope that helps someone.

At the time of writing HttpContext.Connection.IsLocal is now missing from .NET Core.

Other working solution checks only for a first loopback address (::1 or 127.0.0.1) which might not be adequate.

I find the solution below useful:

using Microsoft.AspNetCore.Http;
using System.Net;

namespace ApiHelpers.Filters
{
    public static class HttpContextFilters
    {
        public static bool IsLocalRequest(HttpContext context)
        {
            if (context.Connection.RemoteIpAddress.Equals(context.Connection.LocalIpAddress))
            {
                return true;
            }
            if (IPAddress.IsLoopback(context.Connection.RemoteIpAddress))
            {
                return true;
            }
            return false;
        }
    }
}

And the example use case:

app.UseWhen(HttpContextFilters.IsLocalRequest, configuration => configuration.UseElmPage());