Let's Encrypt confirmation on IIS not working - iis

Question

I'm trying to use the Certify SSL Manager to configure SSL certificates from Let's Encrypt on my IIS server, but it fails during the check.
https://dev.mywebsite.com/.well-known/acme-challenge/configcheck/
This works:
https://dev.mywebsite.com/well-known/acme-challenge/configcheck
https://dev.mywebsite.com/.well-known/acme-challenge/test.txt
So I assumed it's the . before well-known. But the fact that test.txt works confuses me.
I've already configured the directory according to this discussion:
https://github.com/ebekker/ACMESharp/issues/15
I have a bunch of rewrite stuff in my web.config, but even if I remove that section completely, it still fails.

Answer 1

Perhaps check if the acme-challenge web.config contains a conflict within the handler section. Do so by opening IIS manager, find the acme-challenge folder en double click the handler mapping icon. In my case, this resulted in an error.
The problem I ran into with the default web.config in the acme-challenge folder was that the applicationhost.config contained:
<section name="handlers" overrideModeDefault="Deny" />
The handlers section in the acme-challenge web.config therefore was not allowed with the result that the challenge failed. In this case the solutions were:
Change applicationhost.config line to:
<section name="handlers" overrideModeDefault="Allow" />
Or ...
Remove the handlers setting from the web.config in acme-challenge folder.
The applicationhost.config can be found here: c:\windows\system32\inetsrv\config

Answer 2

The configcheck url is a file, not a directory. Make sure that file exists on disk (i.e. C:\inetpub\wwwroot\.well-known\acme-challenge\configcheck) in your webroot. Then try to load your links with this barebones web.config in your website root directory (if using ASP.NET):
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<staticContent>
<mimeMap fileExtension="." mimeType="application/unknown" />
</staticContent>
</system.webServer>
</configuration>
If that works, try slowly adding back in your web.config sections including routes/rewrite until you figure out what's causing the problem.
If using ASP.NET Core with a wwwroot folder hosting your static files, you'll have to modify your config in Startup.cs instead:
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
string filepath = Path.Combine(Directory.GetCurrentDirectory(), #"wwwroot/.well-known");
app.UseStaticFiles(new StaticFileOptions()
{
FileProvider = new PhysicalFileProvider(filepath),
RequestPath = new PathString("/.well-known"),
ServeUnknownFileTypes = true
});
// ... your other startup code here
}

Answer 3

I had to modify the web.config as follow to fix the error:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<staticContent>
<mimeMap fileExtension="*" mimeType="text/plain" />
</staticContent>
<handlers>
<clear />
<add name="StaticFile" path="*" verb="*" type=""
modules="StaticFileModule,DefaultDocumentModule,DirectoryListingModule"
scriptProcessor="" resourceType="Either" requireAccess="Read"
allowPathInfo="true" preCondition="" responseBufferLimit="4194304" />
</handlers>
</system.webServer>
</configuration>