Sure, working up Gambit's built-in OpenSSL API integration to work as a client for ordinary usecases, works.
Please remember that SSL domain validation only is the tip of the iceberg though, in such a way that in particular for server usecases and also for more sophisticated client usecases, OpenSSL's unending quirks (and very low code quality) lead you to need an application-level solution anyhow.
(
I suggest SSL domain name validation is only the tip of the iceberg, you'll want to
* negotiate the right ciphers with the right settings,
* configure exact TLS/SSL versions supported,
* cap TSL renegotiation ability,
* in server mode deliver more TLS certificates on the same TLS server (IP),
* read certificates from binary blobs and generate local certificates,
* and then finally someone will like to do a non-TSL handshake/warmup before the TLS takes over, or do TLS over something else than a TCP port.
)
On my TODO is to implement a proof of concept application layer ports for Gambit. After reading _io.scm a couple of times and talking to Vyzo about it, I was struck with a sense of confidence that I could actually do it heh.