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1 /*
2  * SHA1-based PRF
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 /**
17  * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
18  * @key: Key for PRF
19  * @key_len: Length of the key in bytes
20  * @label: A unique label for each purpose of the PRF
21  * @data: Extra data to bind into the key
22  * @data_len: Length of the data
23  * @buf: Buffer for the generated pseudo-random key
24  * @buf_len: Number of bytes of key to generate
25  * Returns: 0 on success, -1 of failure
26  *
27  * This function is used to derive new, cryptographically separate keys from a
28  * given key (e.g., PMK in IEEE 802.11i).
29  */
sha1_prf(const u8 * key,size_t key_len,const char * label,const u8 * data,size_t data_len,u8 * buf,size_t buf_len)30 int sha1_prf(const u8 *key, size_t key_len, const char *label,
31 	     const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
32 {
33 	u8 counter = 0;
34 	size_t pos, plen;
35 	u8 hash[SHA1_MAC_LEN];
36 	size_t label_len = os_strlen(label) + 1;
37 	const unsigned char *addr[3];
38 	size_t len[3];
39 
40 	addr[0] = (u8 *) label;
41 	len[0] = label_len;
42 	addr[1] = data;
43 	len[1] = data_len;
44 	addr[2] = &counter;
45 	len[2] = 1;
46 
47 	pos = 0;
48 	while (pos < buf_len) {
49 		plen = buf_len - pos;
50 		if (plen >= SHA1_MAC_LEN) {
51 			if (hmac_sha1_vector(key, key_len, 3, addr, len,
52 					     &buf[pos]))
53 				return -1;
54 			pos += SHA1_MAC_LEN;
55 		} else {
56 			if (hmac_sha1_vector(key, key_len, 3, addr, len,
57 					     hash))
58 				return -1;
59 			os_memcpy(&buf[pos], hash, plen);
60 			break;
61 		}
62 		counter++;
63 	}
64 	os_memset(hash, 0, sizeof(hash));
65 
66 	return 0;
67 }
68