As a part of a larger application I need to implement an SSL tunnel in C#. I was wondering if there's a better way of doing that instead of writing each step of SSL negotiation myself which sounds like reinventing the wheel.
Do you know if there are any libraries that I could use to minimize the code I need to write or any tutorials which show how this or similar thing can be implemented most efficiently in .NET?
It's not clear what you mean by SSL tunnel. If I understand it right, you need some client-side software which acts as a local server (to which other applications connect), this software then connects using SSL to your server-side software, which in turn takes the data out of the SSL tunnel, and routes them further. In this case you would need client-side and server-side SSL/TLS components. You can use SecureBlackbox for this task. SecureBlackbox provides comprehensive support for SSL/TLS protocol with complete control over connection and certificate management.
It can be that you need not plain SSL channel, but some kind of encrypting proxy. In this case you need to decide what exactly kind of proxy you want (will it be SOCKS proxy or HTTP CONNECT proxy) and implement it on the client side. one of the benefits of such proxy is that it can transfer the real connection address (i.e. where the client wants to go to) to the remote server, and that remote server will perform connection. This is more flexible approach, but it would require some (minimal, I should say) coding to implement the stuff, related to SOCKS or HTTP CONNECT request parsing and response generation.