1 /*
2 * SHA1 T-PRF for EAP-FAST
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 * sha1_t_prf - EAP-FAST Pseudo-Random Function (T-PRF)
17 * @key: Key for PRF
18 * @key_len: Length of the key in bytes
19 * @label: A unique label for each purpose of the PRF
20 * @seed: Seed value to bind into the key
21 * @seed_len: Length of the seed
22 * @buf: Buffer for the generated pseudo-random key
23 * @buf_len: Number of bytes of key to generate
24 * Returns: 0 on success, -1 of failure
25 *
26 * This function is used to derive new, cryptographically separate keys from a
27 * given key for EAP-FAST. T-PRF is defined in RFC 4851, Section 5.5.
28 */
sha1_t_prf(const u8 * key,size_t key_len,const char * label,const u8 * seed,size_t seed_len,u8 * buf,size_t buf_len)29 int sha1_t_prf(const u8 *key, size_t key_len, const char *label,
30 const u8 *seed, size_t seed_len, u8 *buf, size_t buf_len)
31 {
32 unsigned char counter = 0;
33 size_t pos, plen;
34 u8 hash[SHA1_MAC_LEN];
35 size_t label_len = os_strlen(label);
36 u8 output_len[2];
37 const unsigned char *addr[5];
38 size_t len[5];
39
40 addr[0] = hash;
41 len[0] = 0;
42 addr[1] = (unsigned char *) label;
43 len[1] = label_len + 1;
44 addr[2] = seed;
45 len[2] = seed_len;
46 addr[3] = output_len;
47 len[3] = 2;
48 addr[4] = &counter;
49 len[4] = 1;
50
51 output_len[0] = (buf_len >> 8) & 0xff;
52 output_len[1] = buf_len & 0xff;
53 pos = 0;
54 while (pos < buf_len) {
55 counter++;
56 plen = buf_len - pos;
57 if (hmac_sha1_vector(key, key_len, 5, addr, len, hash))
58 return -1;
59 if (plen >= SHA1_MAC_LEN) {
60 os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
61 pos += SHA1_MAC_LEN;
62 } else {
63 os_memcpy(&buf[pos], hash, plen);
64 break;
65 }
66 len[0] = SHA1_MAC_LEN;
67 }
68
69 forced_memzero(hash, SHA1_MAC_LEN);
70
71 return 0;
72 }
73
