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
54 return 0;
55 }
56
57
58 /**
59 * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
60 * @passphrase: ASCII passphrase
61 * @ssid: SSID
62 * @ssid_len: SSID length in bytes
63 * @iterations: Number of iterations to run
64 * @buf: Buffer for the generated key
65 * @buflen: Length of the buffer in bytes
66 * Returns: 0 on success, -1 of failure
67 *
68 * This function is used to derive PSK for WPA-PSK. For this protocol,
69 * iterations is set to 4096 and buflen to 32. This function is described in
70 * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
71 */
pbkdf2_sha1(const char * passphrase,const u8 * ssid,size_t ssid_len,int iterations,u8 * buf,size_t buflen)72 int pbkdf2_sha1(const char *passphrase, const u8 *ssid, size_t ssid_len,
73 int iterations, u8 *buf, size_t buflen)
74 {
75 unsigned int count = 0;
76 unsigned char *pos = buf;
77 size_t left = buflen, plen;
78 unsigned char digest[SHA1_MAC_LEN];
79
80 while (left > 0) {
81 count++;
82 if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,
83 count, digest))
84 return -1;
85 plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
86 os_memcpy(pos, digest, plen);
87 pos += plen;
88 left -= plen;
89 }
90
91 return 0;
92 }
93