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      1 /*
      2  * SHA-256 hash implementation and interface functions
      3  * Copyright (c) 2003-2012, Jouni Malinen <j (at) 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  */
     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[6];
     32 	size_t _len[6], i;
     33 
     34 	if (num_elem > 5) {
     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  */
    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