2 * SHA1 T-PRF for EAP-FAST
3 * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
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.
9 * Alternatively, this software may be distributed under the terms of BSD
12 * See README and COPYING for more details.
22 * sha1_t_prf - EAP-FAST Pseudo-Random Function (T-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
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.
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)
38 unsigned char counter = 0;
40 u8 hash[SHA1_MAC_LEN];
41 size_t label_len = os_strlen(label);
43 const unsigned char *addr[5];
48 addr[1] = (unsigned char *) label;
49 len[1] = label_len + 1;
57 output_len[0] = (buf_len >> 8) & 0xff;
58 output_len[1] = buf_len & 0xff;
60 while (pos < buf_len) {
63 if (hmac_sha1_vector(key, key_len, 5, addr, len, hash))
65 if (plen >= SHA1_MAC_LEN) {
66 os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
69 os_memcpy(&buf[pos], hash, plen);
72 len[0] = SHA1_MAC_LEN;