How to specify ECDSA nonce used in bitcoin signing code?
ECDSA_do_sign() does not allow specifying the nonce. You can use ECDSA_do_sign_ex(), which needs extra arguments for (k*G).x and 1/k instead.

Bitcoin master recently switched to the libsecp256k1 library for signing, which always needs the nonce passed explicitly, and does not require precomputation of the x coordinate and inverse. See the code in Bitcoin Core for signing: https://github.com/bitcoin/bitcoin/blob/0a1d03ca5265293e6419b0ffb68d277da6b1d9a0/src/key.cpp#L75-L92

Disclaimer: I'm the author of libsecp256k1.