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      1 /*
      2  * One-key CBC MAC (OMAC1) hash with AES-128
      3  *
      4  * Copyright (c) 2003-2007, Jouni Malinen <j (at) w1.fi>
      5  *
      6  * This software may be distributed under the terms of the BSD license.
      7  * See README for more details.
      8  */
      9 
     10 #include "includes.h"
     11 
     12 #include "common.h"
     13 #include "aes.h"
     14 #include "aes_wrap.h"
     15 
     16 static void gf_mulx(u8 *pad)
     17 {
     18 	int i, carry;
     19 
     20 	carry = pad[0] & 0x80;
     21 	for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
     22 		pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
     23 	pad[AES_BLOCK_SIZE - 1] <<= 1;
     24 	if (carry)
     25 		pad[AES_BLOCK_SIZE - 1] ^= 0x87;
     26 }
     27 
     28 
     29 /**
     30  * omac1_aes_128_vector - One-Key CBC MAC (OMAC1) hash with AES-128
     31  * @key: 128-bit key for the hash operation
     32  * @num_elem: Number of elements in the data vector
     33  * @addr: Pointers to the data areas
     34  * @len: Lengths of the data blocks
     35  * @mac: Buffer for MAC (128 bits, i.e., 16 bytes)
     36  * Returns: 0 on success, -1 on failure
     37  *
     38  * This is a mode for using block cipher (AES in this case) for authentication.
     39  * OMAC1 was standardized with the name CMAC by NIST in a Special Publication
     40  * (SP) 800-38B.
     41  */
     42 int omac1_aes_128_vector(const u8 *key, size_t num_elem,
     43 			 const u8 *addr[], const size_t *len, u8 *mac)
     44 {
     45 	void *ctx;
     46 	u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
     47 	const u8 *pos, *end;
     48 	size_t i, e, left, total_len;
     49 
     50 	ctx = aes_encrypt_init(key, 16);
     51 	if (ctx == NULL)
     52 		return -1;
     53 	os_memset(cbc, 0, AES_BLOCK_SIZE);
     54 
     55 	total_len = 0;
     56 	for (e = 0; e < num_elem; e++)
     57 		total_len += len[e];
     58 	left = total_len;
     59 
     60 	e = 0;
     61 	pos = addr[0];
     62 	end = pos + len[0];
     63 
     64 	while (left >= AES_BLOCK_SIZE) {
     65 		for (i = 0; i < AES_BLOCK_SIZE; i++) {
     66 			cbc[i] ^= *pos++;
     67 			if (pos >= end) {
     68 				e++;
     69 				pos = addr[e];
     70 				end = pos + len[e];
     71 			}
     72 		}
     73 		if (left > AES_BLOCK_SIZE)
     74 			aes_encrypt(ctx, cbc, cbc);
     75 		left -= AES_BLOCK_SIZE;
     76 	}
     77 
     78 	os_memset(pad, 0, AES_BLOCK_SIZE);
     79 	aes_encrypt(ctx, pad, pad);
     80 	gf_mulx(pad);
     81 
     82 	if (left || total_len == 0) {
     83 		for (i = 0; i < left; i++) {
     84 			cbc[i] ^= *pos++;
     85 			if (pos >= end) {
     86 				e++;
     87 				pos = addr[e];
     88 				end = pos + len[e];
     89 			}
     90 		}
     91 		cbc[left] ^= 0x80;
     92 		gf_mulx(pad);
     93 	}
     94 
     95 	for (i = 0; i < AES_BLOCK_SIZE; i++)
     96 		pad[i] ^= cbc[i];
     97 	aes_encrypt(ctx, pad, mac);
     98 	aes_encrypt_deinit(ctx);
     99 	return 0;
    100 }
    101 
    102 
    103 /**
    104  * omac1_aes_128 - One-Key CBC MAC (OMAC1) hash with AES-128 (aka AES-CMAC)
    105  * @key: 128-bit key for the hash operation
    106  * @data: Data buffer for which a MAC is determined
    107  * @data_len: Length of data buffer in bytes
    108  * @mac: Buffer for MAC (128 bits, i.e., 16 bytes)
    109  * Returns: 0 on success, -1 on failure
    110  *
    111  * This is a mode for using block cipher (AES in this case) for authentication.
    112  * OMAC1 was standardized with the name CMAC by NIST in a Special Publication
    113  * (SP) 800-38B.
    114  */
    115 int omac1_aes_128(const u8 *key, const u8 *data, size_t data_len, u8 *mac)
    116 {
    117 	return omac1_aes_128_vector(key, 1, &data, &data_len, mac);
    118 }
    119