Expose SNI hostname via a feature

[shirhatti]

We currently do not expose the SNI hostname via a feature interface

aspnetcore/src/Servers/Kestrel/Core/src/Internal/TlsConnectionFeature.cs

Lines 52 to 53 in 640b77f

	// Used for event source, not part of any of the feature interfaces.
	public string? HostName { get; set; }

namespace Microsoft.AspNetCore.Http.Features
{
    public interface ITlsHandshakeFeature
    {
+        string? HostName { get; }
    }
}

Given that it's already a property on the TlsConnectionFeature we can trivially expose it.

[Tratcher]

Is it available on http.sys or IIS?

[shirhatti]

@alanwest @cijothomas Y'all might be interested in this for open-telemetry/opentelemetry-dotnet#2159 if you wish to add the http.server_name attribute.

[shirhatti]

@Tratcher Is there somewhere else I should be looking?

aspnetcore/src/Shared/HttpSys/NativeInterop/HttpApiTypes.cs

Lines 261 to 272 in 640b77f

	[StructLayout(LayoutKind.Sequential)]
	internal struct HTTP_SSL_INFO
	{
	internal ushort ServerCertKeySize;
	internal ushort ConnectionKeySize;
	internal uint ServerCertIssuerSize;
	internal uint ServerCertSubjectSize;
	internal byte* pServerCertIssuer;
	internal byte* pServerCertSubject;
	internal HTTP_SSL_CLIENT_CERT_INFO* pClientCertInfo;
	internal uint SslClientCertNegotiated;
	}

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[shirhatti]

Microsoft.Extensions.Features targets netstandard2.0 and net461 which means I can't use a DIM 😢

aspnetcore/src/Extensions/Features/src/Microsoft.Extensions.Features.csproj

Line 10 in 23b7049

<TargetFrameworks>$(DefaultNetFxTargetFramework);netstandard2.0;$(DefaultNetCoreTargetFramework)</TargetFrameworks>

[Tratcher]

What are you trying to modify in Microsoft.Extensions.Features? I thought the features you needed to change were in Microsoft.AspNetCore.Http.Features?

[shirhatti]

Oops. I meant

aspnetcore/src/Servers/Connections.Abstractions/src/Microsoft.AspNetCore.Connections.Abstractions.csproj

Line 5 in 23b7049

<TargetFrameworks>$(DefaultNetFxTargetFramework);netstandard2.0;netstandard2.1;$(DefaultNetCoreTargetFramework)</TargetFrameworks>

[Tratcher]

Ah. I guess we'll have to put it on ITlsConnectionFeature instead.

aspnetcore/src/Http/Http.Features/src/ITlsConnectionFeature.cs

Line 13 in 23b7049

public interface ITlsConnectionFeature

[shirhatti]

aspnetcore/src/Servers/Kestrel/Core/src/Middleware/HttpsConnectionMiddleware.cs

Lines 305 to 318 in d1c349f

	if (_serverCertificateSelector != null)
	{
	selector = (sender, name) =>
	{
	feature.HostName = name;
	context.Features.Set(sslStream);
	var cert = _serverCertificateSelector(context, name);
	if (cert != null)
	{
	EnsureCertificateIsAllowedForServerAuth(cert);
	}
	return cert!;
	};
	}

Turns out we never capture the hostname (or set SslStream as a feature) if you don't specify a ServerCertificateSelector