1 /*
2  * SHA-256 hash implementation and interface functions
3  * Copyright (c) 2003-2012, 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 "sha256.h"
13 #include "crypto.h"
14 
15 
16 /**
17  * hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104)
18  * @key: Key for HMAC operations
19  * @key_len: Length of the key in bytes
20  * @num_elem: Number of elements in the data vector
21  * @addr: Pointers to the data areas
22  * @len: Lengths of the data blocks
23  * @mac: Buffer for the hash (32 bytes)
24  * Returns: 0 on success, -1 on failure
25  */
hmac_sha256_vector(const u8 * key,size_t key_len,size_t num_elem,const u8 * addr[],const size_t * len,u8 * mac)26 int hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem,
27 		       const u8 *addr[], const size_t *len, u8 *mac)
28 {
29 	unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
30 	unsigned char tk[32];
31 	const u8 *_addr[11];
32 	size_t _len[11], i;
33 
34 	if (num_elem > 10) {
35 		/*
36 		 * Fixed limit on the number of fragments to avoid having to
37 		 * allocate memory (which could fail).
38 		 */
39 		return -1;
40 	}
41 
42         /* if key is longer than 64 bytes reset it to key = SHA256(key) */
43         if (key_len > 64) {
44 		if (sha256_vector(1, &key, &key_len, tk) < 0)
45 			return -1;
46 		key = tk;
47 		key_len = 32;
48         }
49 
50 	/* the HMAC_SHA256 transform looks like:
51 	 *
52 	 * SHA256(K XOR opad, SHA256(K XOR ipad, text))
53 	 *
54 	 * where K is an n byte key
55 	 * ipad is the byte 0x36 repeated 64 times
56 	 * opad is the byte 0x5c repeated 64 times
57 	 * and text is the data being protected */
58 
59 	/* start out by storing key in ipad */
60 	os_memset(k_pad, 0, sizeof(k_pad));
61 	os_memcpy(k_pad, key, key_len);
62 	/* XOR key with ipad values */
63 	for (i = 0; i < 64; i++)
64 		k_pad[i] ^= 0x36;
65 
66 	/* perform inner SHA256 */
67 	_addr[0] = k_pad;
68 	_len[0] = 64;
69 	for (i = 0; i < num_elem; i++) {
70 		_addr[i + 1] = addr[i];
71 		_len[i + 1] = len[i];
72 	}
73 	if (sha256_vector(1 + num_elem, _addr, _len, mac) < 0)
74 		return -1;
75 
76 	os_memset(k_pad, 0, sizeof(k_pad));
77 	os_memcpy(k_pad, key, key_len);
78 	/* XOR key with opad values */
79 	for (i = 0; i < 64; i++)
80 		k_pad[i] ^= 0x5c;
81 
82 	/* perform outer SHA256 */
83 	_addr[0] = k_pad;
84 	_len[0] = 64;
85 	_addr[1] = mac;
86 	_len[1] = SHA256_MAC_LEN;
87 	return sha256_vector(2, _addr, _len, mac);
88 }
89 
90 
91 /**
92  * hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104)
93  * @key: Key for HMAC operations
94  * @key_len: Length of the key in bytes
95  * @data: Pointers to the data area
96  * @data_len: Length of the data area
97  * @mac: Buffer for the hash (32 bytes)
98  * Returns: 0 on success, -1 on failure
99  */
hmac_sha256(const u8 * key,size_t key_len,const u8 * data,size_t data_len,u8 * mac)100 int hmac_sha256(const u8 *key, size_t key_len, const u8 *data,
101 		size_t data_len, u8 *mac)
102 {
103 	return hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac);
104 }
105