There is n "source code for wpa2". Actually there are many. It is an algorithm, thus can be implemented in several (almost all) programming languages, so there is no "one and only" source code if it. And it is highly hardware dependent.
The algorithm is summarized here:
http://en.wikipedia.org/wiki/IEEE_802.11i-2004[
^], but you can read the whole standard here:
http://www.elektormedia.com/EthernetToolbox/Data/Standard/802.11i-2004.pdf[
^]
But most of the implementations will be in C, here is an open source router firmware repository:
http://www.dd-wrt.com/wiki/index.php/Compiling_DD-WRT_Sources[
^], the soure is at
svn://svn.dd-wrt.com/DD-WRT/src/squashfs-tools
, but you need an SVN client to browse it.
Btw: the tar file is the oldest of all archives. You can use 7Zip for example to open it.