SSLConn

This is an experimental golang (CGO) wrapper around OpenSSL.

The crypto/tls package does not support (1) SSLv2 compatible handshakes,
so this is an attempt to use OpenSSL in golang. The reason SSLv2 handshake
is desired is for compatibility (2) with a variety of clients.

The suggested approach is to provide SSL termination upstream, however 
some protocols upgrade plain text connections using STARTTLS (3) which 
would require a smart and protocol aware SSL terminator.

This wrapper only exposes only a tiny subset of the OpenSSL API, just
enough to enable the use-case described above.

Examples: github.com/vadims/sslconn-examples

Implementation Details

In order to multiplex a OpenSSL connection the underlying IO needs to
be non blocking. To support that, a NonBlockingReader and NonBlockingWriter
were implemented to provide the necessary semantics.

Most of the OpenSSL integration is done in C to avoid locking the OS 
thread required for error checking (thread locals.) 

1. http://code.google.com/p/go/issues/detail?id=3930
2. http://www.openssl.org/docs/ssl/SSL_CTX_new.html
3. http://en.wikipedia.org/wiki/STARTTLS