It's just simple SHA2, you can implement the whole thing easily without dragging in a huge lib like OpenSSL. I guess I haven't looked at it recently but the original CPU miner was just implemented locally in bitcoin and didn't use any libs.
I don't get the 'dragging in' part. Bitcoin already depends on OpenSSL for ecdsa, bignum, and SSL for RPC. Please, please don't try to reimplement these locally :-)