feat(HTTP.SYS): on-demand TLS client hello retrieval

[DeagleGross]

HTTP.SYS only on-demand TLS client hello

As discussed in api proposal we are doing 2 things here:

1. removing previous "callback" API HttpSysOptions.TlsClientHelloBytesCallback
2. implementing an on-demand request of TlsClientHello via win API. It is done by exposing a method on a new feature interface IHttpSysRequestPropertiesFeature: IHttpSysRequestPropertiesFeature.TryGetTlsClientHello.

TlsFeaturesObserve.Program sample shows the usage of that feature and this API in particular:

app.Use(async (context, next) =>
{
    var connectionFeature = context.Features.GetRequiredFeature<IHttpConnectionFeature>();
    var httpSysPropFeature = context.Features.GetRequiredFeature<IHttpSysRequestPropertyFeature>();

    // first time invocation to find out required size
    var success = httpSysPropFeature.TryGetTlsClientHello(Array.Empty<byte>(), out var bytesReturned);
    Debug.Assert(!success);
    Debug.Assert(bytesReturned > 0);

    // rent with enough memory span and invoke
    var bytes = ArrayPool<byte>.Shared.Rent(bytesReturned);
    success = httpSysPropFeature.TryGetTlsClientHello(bytes, out _);
    Debug.Assert(success);

    await context.Response.WriteAsync($"[Response] connectionId={connectionFeature.ConnectionId}; tlsClientHello.length={bytesReturned}; tlsclienthello start={string.Join(' ', bytes.AsSpan(0, 30).ToArray())}");
    await next(context);
});

Implements #61625

[tdykstra]

Just A few nits.

[DeagleGross]

/backport to release/8.0

[github-actions]

Started backporting to release/8.0: https://github.com/dotnet/aspnetcore/actions/runs/15546470366

[github-actions]

@DeagleGross backporting to "release/8.0" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: drop callback / implement on-demand tls client hello access
Using index info to reconstruct a base tree...
M	src/Servers/HttpSys/samples/TlsFeaturesObserve/Program.cs
M	src/Servers/HttpSys/src/HttpSysListener.cs
M	src/Servers/HttpSys/src/HttpSysOptions.cs
M	src/Servers/HttpSys/src/PublicAPI.Unshipped.txt
M	src/Servers/HttpSys/src/RequestProcessing/Request.cs
M	src/Servers/HttpSys/src/RequestProcessing/RequestContext.FeatureCollection.cs
M	src/Servers/HttpSys/src/RequestProcessing/RequestContext.cs
M	src/Servers/HttpSys/src/RequestProcessing/TlsListener.cs
Falling back to patching base and 3-way merge...
CONFLICT (modify/delete): src/Servers/HttpSys/src/RequestProcessing/TlsListener.cs deleted in drop callback / implement on-demand tls client hello access and modified in HEAD. Version HEAD of src/Servers/HttpSys/src/RequestProcessing/TlsListener.cs left in tree.
Removing src/Servers/HttpSys/src/RequestProcessing/TlsListener.Log.cs
Auto-merging src/Servers/HttpSys/src/RequestProcessing/RequestContext.cs
CONFLICT (content): Merge conflict in src/Servers/HttpSys/src/RequestProcessing/RequestContext.cs
Auto-merging src/Servers/HttpSys/src/RequestProcessing/RequestContext.FeatureCollection.cs
Auto-merging src/Servers/HttpSys/src/RequestProcessing/Request.cs
CONFLICT (content): Merge conflict in src/Servers/HttpSys/src/RequestProcessing/Request.cs
Auto-merging src/Servers/HttpSys/src/PublicAPI.Unshipped.txt
CONFLICT (content): Merge conflict in src/Servers/HttpSys/src/PublicAPI.Unshipped.txt
Auto-merging src/Servers/HttpSys/src/HttpSysOptions.cs
CONFLICT (content): Merge conflict in src/Servers/HttpSys/src/HttpSysOptions.cs
Auto-merging src/Servers/HttpSys/src/HttpSysListener.cs
CONFLICT (content): Merge conflict in src/Servers/HttpSys/src/HttpSysListener.cs
Removing src/Servers/HttpSys/samples/TlsFeaturesObserve/Startup.cs
Auto-merging src/Servers/HttpSys/samples/TlsFeaturesObserve/Program.cs
CONFLICT (content): Merge conflict in src/Servers/HttpSys/samples/TlsFeaturesObserve/Program.cs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 drop callback / implement on-demand tls client hello access
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

[dotnet-policy-service]

@@DeagleGross, this change will be considered for inclusion in the blog post for the release it'll ship in. Nice work!

Please ensure that the original comment in this thread contains a clear explanation of what the change does, why it's important (what problem does it solve?), and, if relevant, include things like code samples and/or performance numbers.

This content may not be exactly what goes into the blog post, but it will help the team putting together the announcement.

Thanks!