sha1-tprf.c revision 8d520ff1dc2da35cdca849e982051b86468016d8 
1/*
2 * SHA1 T-PRF for EAP-FAST
3 * Copyright (c) 2003-2005, Jouni Malinen <j@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 */
35int 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