I have seen Where to find Java 6 JSSE/JCE Source Code? and asked the question myself How to get JRE/JDK with matching source? but I don\'t either of these was specific enough
The JSSE source code for the Sun Java releases was formerly available via the Sun Community Source License Program. Since the Oracle takeover it appears to have disappeared, but I hope I'm wrong about that.
The Sun implementation is not open source as far as I know. You can download an open source JCE here:
http://www.bouncycastle.org/java.html