Line data Source code
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 : */
29 419 : 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 : {
32 419 : unsigned char counter = 0;
33 : size_t pos, plen;
34 : u8 hash[SHA1_MAC_LEN];
35 419 : size_t label_len = os_strlen(label);
36 : u8 output_len[2];
37 : const unsigned char *addr[5];
38 : size_t len[5];
39 :
40 419 : addr[0] = hash;
41 419 : len[0] = 0;
42 419 : addr[1] = (unsigned char *) label;
43 419 : len[1] = label_len + 1;
44 419 : addr[2] = seed;
45 419 : len[2] = seed_len;
46 419 : addr[3] = output_len;
47 419 : len[3] = 2;
48 419 : addr[4] = &counter;
49 419 : len[4] = 1;
50 :
51 419 : output_len[0] = (buf_len >> 8) & 0xff;
52 419 : output_len[1] = buf_len & 0xff;
53 419 : pos = 0;
54 2013 : while (pos < buf_len) {
55 1409 : counter++;
56 1409 : plen = buf_len - pos;
57 1409 : if (hmac_sha1_vector(key, key_len, 5, addr, len, hash))
58 3 : return -1;
59 1406 : if (plen >= SHA1_MAC_LEN) {
60 1175 : os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
61 1175 : pos += SHA1_MAC_LEN;
62 : } else {
63 231 : os_memcpy(&buf[pos], hash, plen);
64 231 : break;
65 : }
66 1175 : len[0] = SHA1_MAC_LEN;
67 : }
68 :
69 416 : os_memset(hash, 0, SHA1_MAC_LEN);
70 :
71 416 : return 0;
72 : }
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