Certificate chain building and verification should be cancellable AuthenticateAs* on OSX and Linux: - https://github.com/dotnet/runtime/blob/b44492d10a783726a12513c9292ef69489dde468/src/libraries/System.Net.Security/src/System/Net/Security/Pal.OSX/SafeDeleteSslContext.cs#L325 - https://github.com/dotnet/runtime/blob/4bdf4684ddf5636c3d8ed8cd7231e40fc069ab0a/src/libraries/Common/src/Interop/Unix/System.Security.Cryptography.Native/Interop.OpenSsl.cs#L213