1 /* 2 * SHA1 T-PRF for EAP-FAST 3 * Copyright (c) 2003-2005, Jouni Malinen <j (at) w1.fi> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 * 9 * Alternatively, this software may be distributed under the terms of BSD 10 * license. 11 * 12 * See README and COPYING for more details. 13 */ 14 15 #include "includes.h" 16 17 #include "common.h" 18 #include "sha1.h" 19 #include "crypto.h" 20 21 /** 22 * sha1_t_prf - EAP-FAST Pseudo-Random Function (T-PRF) 23 * @key: Key for PRF 24 * @key_len: Length of the key in bytes 25 * @label: A unique label for each purpose of the PRF 26 * @seed: Seed value to bind into the key 27 * @seed_len: Length of the seed 28 * @buf: Buffer for the generated pseudo-random key 29 * @buf_len: Number of bytes of key to generate 30 * Returns: 0 on success, -1 of failure 31 * 32 * This function is used to derive new, cryptographically separate keys from a 33 * given key for EAP-FAST. T-PRF is defined in RFC 4851, Section 5.5. 34 */ 35 int sha1_t_prf(const u8 *key, size_t key_len, const char *label, 36 const u8 *seed, size_t seed_len, u8 *buf, size_t buf_len) 37 { 38 unsigned char counter = 0; 39 size_t pos, plen; 40 u8 hash[SHA1_MAC_LEN]; 41 size_t label_len = os_strlen(label); 42 u8 output_len[2]; 43 const unsigned char *addr[5]; 44 size_t len[5]; 45 46 addr[0] = hash; 47 len[0] = 0; 48 addr[1] = (unsigned char *) label; 49 len[1] = label_len + 1; 50 addr[2] = seed; 51 len[2] = seed_len; 52 addr[3] = output_len; 53 len[3] = 2; 54 addr[4] = &counter; 55 len[4] = 1; 56 57 output_len[0] = (buf_len >> 8) & 0xff; 58 output_len[1] = buf_len & 0xff; 59 pos = 0; 60 while (pos < buf_len) { 61 counter++; 62 plen = buf_len - pos; 63 if (hmac_sha1_vector(key, key_len, 5, addr, len, hash)) 64 return -1; 65 if (plen >= SHA1_MAC_LEN) { 66 os_memcpy(&buf[pos], hash, SHA1_MAC_LEN); 67 pos += SHA1_MAC_LEN; 68 } else { 69 os_memcpy(&buf[pos], hash, plen); 70 break; 71 } 72 len[0] = SHA1_MAC_LEN; 73 } 74 75 return 0; 76 } 77
