1/*
2 * SHA1-based PRF
3 * Copyright (c) 2003-2005, Jouni Malinen <j@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 "sha1.h"
13#include "crypto.h"
14
15
16/**
17 * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
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 * Returns: 0 on success, -1 of failure
26 *
27 * This function is used to derive new, cryptographically separate keys from a
28 * given key (e.g., PMK in IEEE 802.11i).
29 */
30int sha1_prf(const u8 *key, size_t key_len, const char *label,
31	     const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
32{
33	u8 counter = 0;
34	size_t pos, plen;
35	u8 hash[SHA1_MAC_LEN];
36	size_t label_len = os_strlen(label) + 1;
37	const unsigned char *addr[3];
38	size_t len[3];
39
40	addr[0] = (u8 *) label;
41	len[0] = label_len;
42	addr[1] = data;
43	len[1] = data_len;
44	addr[2] = &counter;
45	len[2] = 1;
46
47	pos = 0;
48	while (pos < buf_len) {
49		plen = buf_len - pos;
50		if (plen >= SHA1_MAC_LEN) {
51			if (hmac_sha1_vector(key, key_len, 3, addr, len,
52					     &buf[pos]))
53				return -1;
54			pos += SHA1_MAC_LEN;
55		} else {
56			if (hmac_sha1_vector(key, key_len, 3, addr, len,
57					     hash))
58				return -1;
59			os_memcpy(&buf[pos], hash, plen);
60			break;
61		}
62		counter++;
63	}
64
65	return 0;
66}
67