1252190Srpaulo/* 2252190Srpaulo * SHA256-based PRF (IEEE 802.11r) 3252190Srpaulo * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi> 4252190Srpaulo * 5252190Srpaulo * This software may be distributed under the terms of the BSD license. 6252190Srpaulo * See README for more details. 7252190Srpaulo */ 8252190Srpaulo 9252190Srpaulo#include "includes.h" 10252190Srpaulo 11252190Srpaulo#include "common.h" 12252190Srpaulo#include "sha256.h" 13252190Srpaulo#include "crypto.h" 14252190Srpaulo 15252190Srpaulo 16252190Srpaulo/** 17252190Srpaulo * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2) 18252190Srpaulo * @key: Key for PRF 19252190Srpaulo * @key_len: Length of the key in bytes 20252190Srpaulo * @label: A unique label for each purpose of the PRF 21252190Srpaulo * @data: Extra data to bind into the key 22252190Srpaulo * @data_len: Length of the data 23252190Srpaulo * @buf: Buffer for the generated pseudo-random key 24252190Srpaulo * @buf_len: Number of bytes of key to generate 25252190Srpaulo * 26252190Srpaulo * This function is used to derive new, cryptographically separate keys from a 27252190Srpaulo * given key. 28252190Srpaulo */ 29252190Srpaulovoid sha256_prf(const u8 *key, size_t key_len, const char *label, 30252190Srpaulo const u8 *data, size_t data_len, u8 *buf, size_t buf_len) 31252190Srpaulo{ 32252190Srpaulo u16 counter = 1; 33252190Srpaulo size_t pos, plen; 34252190Srpaulo u8 hash[SHA256_MAC_LEN]; 35252190Srpaulo const u8 *addr[4]; 36252190Srpaulo size_t len[4]; 37252190Srpaulo u8 counter_le[2], length_le[2]; 38252190Srpaulo 39252190Srpaulo addr[0] = counter_le; 40252190Srpaulo len[0] = 2; 41252190Srpaulo addr[1] = (u8 *) label; 42252190Srpaulo len[1] = os_strlen(label); 43252190Srpaulo addr[2] = data; 44252190Srpaulo len[2] = data_len; 45252190Srpaulo addr[3] = length_le; 46252190Srpaulo len[3] = sizeof(length_le); 47252190Srpaulo 48252190Srpaulo WPA_PUT_LE16(length_le, buf_len * 8); 49252190Srpaulo pos = 0; 50252190Srpaulo while (pos < buf_len) { 51252190Srpaulo plen = buf_len - pos; 52252190Srpaulo WPA_PUT_LE16(counter_le, counter); 53252190Srpaulo if (plen >= SHA256_MAC_LEN) { 54252190Srpaulo hmac_sha256_vector(key, key_len, 4, addr, len, 55252190Srpaulo &buf[pos]); 56252190Srpaulo pos += SHA256_MAC_LEN; 57252190Srpaulo } else { 58252190Srpaulo hmac_sha256_vector(key, key_len, 4, addr, len, hash); 59252190Srpaulo os_memcpy(&buf[pos], hash, plen); 60252190Srpaulo break; 61252190Srpaulo } 62252190Srpaulo counter++; 63252190Srpaulo } 64252190Srpaulo} 65