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 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
pbkdf2_sha1_f(const char * passphrase,const u8 * ssid,size_t ssid_len,int iterations,unsigned int count,u8 * digest)14 static int pbkdf2_sha1_f(const char *passphrase, const u8 *ssid,
15 size_t ssid_len, int iterations, unsigned int count,
16 u8 *digest)
17 {
18 unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
19 int i, j;
20 unsigned char count_buf[4];
21 const u8 *addr[2];
22 size_t len[2];
23 size_t passphrase_len = os_strlen(passphrase);
24
25 addr[0] = ssid;
26 len[0] = ssid_len;
27 addr[1] = count_buf;
28 len[1] = 4;
29
30 /* F(P, S, c, i) = U1 xor U2 xor ... Uc
31 * U1 = PRF(P, S || i)
32 * U2 = PRF(P, U1)
33 * Uc = PRF(P, Uc-1)
34 */
35
36 count_buf[0] = (count >> 24) & 0xff;
37 count_buf[1] = (count >> 16) & 0xff;
38 count_buf[2] = (count >> 8) & 0xff;
39 count_buf[3] = count & 0xff;
40 if (hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len,
41 tmp))
42 return -1;
43 os_memcpy(digest, tmp, SHA1_MAC_LEN);
44
45 for (i = 1; i < iterations; i++) {
46 if (hmac_sha1((u8 *) passphrase, passphrase_len, tmp,
47 SHA1_MAC_LEN, tmp2))
48 return -1;
49 os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
50 for (j = 0; j < SHA1_MAC_LEN; j++)
51 digest[j] ^= tmp2[j];
52 }
53 forced_memzero(tmp, SHA1_MAC_LEN);
54 forced_memzero(tmp2, SHA1_MAC_LEN);
55
56 return 0;
57 }
58
59
60 /**
61 * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
62 * @passphrase: ASCII passphrase
63 * @ssid: SSID
64 * @ssid_len: SSID length in bytes
65 * @iterations: Number of iterations to run
66 * @buf: Buffer for the generated key
67 * @buflen: Length of the buffer in bytes
68 * Returns: 0 on success, -1 of failure
69 *
70 * This function is used to derive PSK for WPA-PSK. For this protocol,
71 * iterations is set to 4096 and buflen to 32. This function is described in
72 * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
73 */
pbkdf2_sha1(const char * passphrase,const u8 * ssid,size_t ssid_len,int iterations,u8 * buf,size_t buflen)74 int pbkdf2_sha1(const char *passphrase, const u8 *ssid, size_t ssid_len,
75 int iterations, u8 *buf, size_t buflen)
76 {
77 unsigned int count = 0;
78 unsigned char *pos = buf;
79 size_t left = buflen, plen;
80 unsigned char digest[SHA1_MAC_LEN];
81
82 while (left > 0) {
83 count++;
84 if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,
85 count, digest))
86 return -1;
87 plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
88 os_memcpy(pos, digest, plen);
89 pos += plen;
90 left -= plen;
91 }
92 forced_memzero(digest, SHA1_MAC_LEN);
93
94 return 0;
95 }
96