hmac_sha256_kdf() function

hmac_sha256_kdf - HMAC-SHA256 based KDF (RFC 5295) @secret: Key for KDF @secret_len: Length of the key in bytes @label: A unique label for each purpose of the KDF or %NULL to select RFC 5869 HKDF-Expand() with arbitrary seed (= info) @seed: Seed value to bind into the key @seed_len: Length of the seed @out: Buffer for the generated pseudo-random key @outlen: Number of bytes of key to generate Returns: 0 on success, -1 on failure. This function is used to derive new, cryptographically separate keys from a given key in ERP. This KDF is defined in RFC 5295, Chapter 3.1.2. When used with label = NULL and seed = info, this matches HKDF-Expand() defined in RFC 5869, Chapter 2.3.