1/*
2 * SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
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 "md5.h"
20#include "crypto.h"
21
22static int pbkdf2_sha1_f(const char *passphrase, const char *ssid,
23			 size_t ssid_len, int iterations, unsigned int count,
24			 u8 *digest)
25{
26	unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
27	int i, j;
28	unsigned char count_buf[4];
29	const u8 *addr[2];
30	size_t len[2];
31	size_t passphrase_len = os_strlen(passphrase);
32
33	addr[0] = (u8 *) ssid;
34	len[0] = ssid_len;
35	addr[1] = count_buf;
36	len[1] = 4;
37
38	/* F(P, S, c, i) = U1 xor U2 xor ... Uc
39	 * U1 = PRF(P, S || i)
40	 * U2 = PRF(P, U1)
41	 * Uc = PRF(P, Uc-1)
42	 */
43
44	count_buf[0] = (count >> 24) & 0xff;
45	count_buf[1] = (count >> 16) & 0xff;
46	count_buf[2] = (count >> 8) & 0xff;
47	count_buf[3] = count & 0xff;
48	if (hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len,
49			     tmp))
50		return -1;
51	os_memcpy(digest, tmp, SHA1_MAC_LEN);
52
53	for (i = 1; i < iterations; i++) {
54		if (hmac_sha1((u8 *) passphrase, passphrase_len, tmp,
55			      SHA1_MAC_LEN, tmp2))
56			return -1;
57		os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
58		for (j = 0; j < SHA1_MAC_LEN; j++)
59			digest[j] ^= tmp2[j];
60	}
61
62	return 0;
63}
64
65
66/**
67 * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
68 * @passphrase: ASCII passphrase
69 * @ssid: SSID
70 * @ssid_len: SSID length in bytes
71 * @iterations: Number of iterations to run
72 * @buf: Buffer for the generated key
73 * @buflen: Length of the buffer in bytes
74 * Returns: 0 on success, -1 of failure
75 *
76 * This function is used to derive PSK for WPA-PSK. For this protocol,
77 * iterations is set to 4096 and buflen to 32. This function is described in
78 * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
79 */
80int pbkdf2_sha1(const char *passphrase, const char *ssid, size_t ssid_len,
81		int iterations, u8 *buf, size_t buflen)
82{
83	unsigned int count = 0;
84	unsigned char *pos = buf;
85	size_t left = buflen, plen;
86	unsigned char digest[SHA1_MAC_LEN];
87
88	while (left > 0) {
89		count++;
90		if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,
91				  count, digest))
92			return -1;
93		plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
94		os_memcpy(pos, digest, plen);
95		pos += plen;
96		left -= plen;
97	}
98
99	return 0;
100}
101