1 /* 2 * SHA256-based PRF (IEEE 802.11r) 3 * Copyright (c) 2003-2007, Jouni Malinen <j (at) w1.fi> 4 * 5 * This software may be distributed under the terms of the BSD license. 6 * See README for more details. 7 */ 8 9 #include "includes.h" 10 11 #include "common.h" 12 #include "sha256.h" 13 #include "crypto.h" 14 15 16 /** 17 * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2) 18 * @key: Key for PRF 19 * @key_len: Length of the key in bytes 20 * @label: A unique label for each purpose of the PRF 21 * @data: Extra data to bind into the key 22 * @data_len: Length of the data 23 * @buf: Buffer for the generated pseudo-random key 24 * @buf_len: Number of bytes of key to generate 25 * 26 * This function is used to derive new, cryptographically separate keys from a 27 * given key. 28 */ 29 void sha256_prf(const u8 *key, size_t key_len, const char *label, 30 const u8 *data, size_t data_len, u8 *buf, size_t buf_len) 31 { 32 u16 counter = 1; 33 size_t pos, plen; 34 u8 hash[SHA256_MAC_LEN]; 35 const u8 *addr[4]; 36 size_t len[4]; 37 u8 counter_le[2], length_le[2]; 38 39 addr[0] = counter_le; 40 len[0] = 2; 41 addr[1] = (u8 *) label; 42 len[1] = os_strlen(label); 43 addr[2] = data; 44 len[2] = data_len; 45 addr[3] = length_le; 46 len[3] = sizeof(length_le); 47 48 WPA_PUT_LE16(length_le, buf_len * 8); 49 pos = 0; 50 while (pos < buf_len) { 51 plen = buf_len - pos; 52 WPA_PUT_LE16(counter_le, counter); 53 if (plen >= SHA256_MAC_LEN) { 54 hmac_sha256_vector(key, key_len, 4, addr, len, 55 &buf[pos]); 56 pos += SHA256_MAC_LEN; 57 } else { 58 hmac_sha256_vector(key, key_len, 4, addr, len, hash); 59 os_memcpy(&buf[pos], hash, plen); 60 break; 61 } 62 counter++; 63 } 64 } 65
