That depends on which filter you are using. A tcp input uses netty, and netty uses OpenSSL. The elasticsearch filters use cheald's manticore, which is built upon the Apache http client, which uses JSSE.
JRuby-OpenSSL uses Bouncy Castle to emulate OpenSSL. It does not use OpenSSL.
If you want to know versions I would suggest building logstash from source and seeing what dependencies get pulled.