The quick answer is no, you can't extend the hashes available in the crypto
module. The given hash is checked at
https://github.com/joyent/node/blob/v0.10.22/src/node_crypto.cc#L2856
and basically depends on the hashes supported by OpenSSL.
You may be able to potentially monkey-patch createHash
to redirect to your own code, but wouldn't be advisable.
Instead, I'd recommend reworking your middleware usage to hash the data after the bodyParser is complete, or skip the standard bodyParser and implement your own for your specific use-case.