sha1_prf() function

sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1) @key: Key for PRF @key_len: Length of the key in bytes @label: A unique label for each purpose of the PRF @data: Extra data to bind into the key @data_len: Length of the data @buf: Buffer for the generated pseudo-random key @buf_len: Number of bytes of key to generate Returns: 0 on success, -1 of failure This function is used to derive new, cryptographically separate keys from a given key (e.g., PMK in IEEE 802.11i).