BigNum to byte stream

I am implementing an SGX Attestation Service Provider using IPP Crypto.

I have derived a shared DH secret with the other party and now want to derive other keys from it using an AES CMAC.

The DH secret is stored in a BigNum while ippsAES_CMAC_UPDATE receives its input message through a pointer to a byte-stream.

Would just passing the BigNum pointer work? If not, is there another simple (preferably copy-free) way to get a pointer to a byte stream representing the number in little-endian format?