sha1-pbkdf2.c revision 1f69aa52ea2e0a73ac502565df8c666ee49cab6a 
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
20static int pbkdf2_sha1_f(const char *passphrase, const char *ssid,
21			 size_t ssid_len, int iterations, unsigned int count,
22			 u8 *digest)
23{
24	unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
25	int i, j;
26	unsigned char count_buf[4];
27	const u8 *addr[2];
28	size_t len[2];
29	size_t passphrase_len = os_strlen(passphrase);
30
31	addr[0] = (u8 *) ssid;
32	len[0] = ssid_len;
33	addr[1] = count_buf;
34	len[1] = 4;
35
36	/* F(P, S, c, i) = U1 xor U2 xor ... Uc
37	 * U1 = PRF(P, S || i)
38	 * U2 = PRF(P, U1)
39	 * Uc = PRF(P, Uc-1)
40	 */
41
42	count_buf[0] = (count >> 24) & 0xff;
43	count_buf[1] = (count >> 16) & 0xff;
44	count_buf[2] = (count >> 8) & 0xff;
45	count_buf[3] = count & 0xff;
46	if (hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len,
47			     tmp))
48		return -1;
49	os_memcpy(digest, tmp, SHA1_MAC_LEN);
50
51	for (i = 1; i < iterations; i++) {
52		if (hmac_sha1((u8 *) passphrase, passphrase_len, tmp,
53			      SHA1_MAC_LEN, tmp2))
54			return -1;
55		os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
56		for (j = 0; j < SHA1_MAC_LEN; j++)
57			digest[j] ^= tmp2[j];
58	}
59
60	return 0;
61}
62
63
64/**
65 * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
66 * @passphrase: ASCII passphrase
67 * @ssid: SSID
68 * @ssid_len: SSID length in bytes
69 * @iterations: Number of iterations to run
70 * @buf: Buffer for the generated key
71 * @buflen: Length of the buffer in bytes
72 * Returns: 0 on success, -1 of failure
73 *
74 * This function is used to derive PSK for WPA-PSK. For this protocol,
75 * iterations is set to 4096 and buflen to 32. This function is described in
76 * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
77 */
78int pbkdf2_sha1(const char *passphrase, const char *ssid, size_t ssid_len,
79		int iterations, u8 *buf, size_t buflen)
80{
81	unsigned int count = 0;
82	unsigned char *pos = buf;
83	size_t left = buflen, plen;
84	unsigned char digest[SHA1_MAC_LEN];
85
86	while (left > 0) {
87		count++;
88		if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,
89				  count, digest))
90			return -1;
91		plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
92		os_memcpy(pos, digest, plen);
93		pos += plen;
94		left -= plen;
95	}
96
97	return 0;
98}
99