Retrieve ServerVariables in ASP.NET Core

Question

I've implemented IdentityServer4. The application is running ASP.NET Core. The hosting environment is on IIS. I'm using Shibboleth to perform pre-authentication to the site. This populates a number of server variables in IIS. (We cannot use HTTP Headers in our environment, everything must be done using ServerVariables)

I want to retrieve either server variable 'AUTH_USER' or 'REMOTE_USER'.

In legacy ASP or ASP.NET this was as simple as calling Request.ServerVariable("AUTH_USER"). This has changed in ASP.NET Core.

I've tried ClaimsPricipal -> User.Identity.Name, (User name is empty, IsAuthenticated is false)

I've confirmed the server variables are in fact set.

This question is similar to this question but doesn't answer the question

May be you have to use forwarded headers with middleware stackoverflow.com/q/51394593/10634638 — estinamir
– estinamir, Commented Feb 25, 2019 at 18:31
We're not using headers. There are no headers to speak of, just 30 or so ServerVariables. — BDarley
– BDarley, Commented Feb 25, 2019 at 18:37

yoel halb · Accepted Answer · 2020-08-18 00:15:17Z

9

In Asp.Net Core 3, there is an extension method GetServerVariable on the HttpContext.

To use it you need to install the Microsoft.AspNetCore.Http.Extensions NuGet package, and the actual method is in the Microsoft.AspNetCore.Http.HttpContextServerVariableExtensions class.

Note that the server has to support it, otherwise it will return null.

For earlier versions of ASP.Net Core you might be able to use the features property of the context property, by calling context.Features.Get<IServerVariablesFeature>()

edited Aug 18, 2020 at 0:15

answered Aug 18, 2020 at 0:04

yoel halb

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CodingYourLife · Accepted Answer · 2021-04-03 23:35:52Z

The .NET (Core) team changed this quite a few times in the last releases. I couldn't neither get HttpContextServerVariableExtensions version nor the legacy variant to via context features to work.

But this gist helped me. Works with .NET 5 on AWS fargate likely with some kind of load balancer pass-through.

public static class HttpContextExtensions
{
    //https://gist.github.com/jjxtra/3b240b31a1ed3ad783a7dcdb6df12c36

    public static IPAddress GetRemoteIPAddress(this HttpContext context, bool allowForwarded = true)
    {
        if (allowForwarded)
        {
            string header = (context.Request.Headers["CF-Connecting-IP"].FirstOrDefault() ?? context.Request.Headers["X-Forwarded-For"].FirstOrDefault());
            if (IPAddress.TryParse(header, out IPAddress ip))
            {
                return ip;
            }
        }
        return context.Connection.RemoteIpAddress;
    }
}

I assume you can get any values like this out of the header. HttpContext.Request.Headers["X-Forwarded-For"]. Note that you cannot locally debug the headers. I didn't see those entries because of my local setup that differs. I saw what magic strings are available e.g. here.

Vijayanand Settin · Accepted Answer · 2023-07-21 17:04:35Z

0

I am using .Net 7 and I had to use the request headers to get to the server variables.

HttpContext.Request?.Headers

answered Jul 21, 2023 at 17:04

Vijayanand Settin

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