1 /*
2 Copyright (c) 2021 Fraunhofer AISEC. See the COPYRIGHT
3 file at the top-level directory of this distribution.
4
5 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 option. This file may not be copied, modified, or distributed
9 except according to those terms.
10 */
11
12 #include <stdio.h>
13 #include <string.h>
14
15 #include "oscore/nonce.h"
16 #include "oscore/security_context.h"
17
18 #include "common/print_util.h"
19 #include "common/memcpy_s.h"
20
create_nonce(struct byte_array * id_piv,struct byte_array * piv,struct byte_array * common_iv,struct byte_array * nonce)21 enum err create_nonce(struct byte_array *id_piv, struct byte_array *piv,
22 struct byte_array *common_iv, struct byte_array *nonce)
23 {
24 /* "1. left-padding the PIV in network byte order with zeroes to exactly 5 bytes"*/
25 uint8_t padded_piv[MAX_PIV_LEN] = { 0 };
26 TRY(_memcpy_s(&padded_piv[sizeof(padded_piv) - piv->len], piv->len,
27 piv->ptr, piv->len));
28
29 /* "2. left-padding the ID_PIV in network byte order with zeroes to exactly nonce length minus 6 bytes," */
30
31 uint8_t padded_id_piv[NONCE_LEN - MAX_PIV_LEN - 1] = { 0 };
32 const uint8_t padded_id_piv_len = sizeof(padded_id_piv);
33 TRY(_memcpy_s(&padded_id_piv[sizeof(padded_id_piv) - id_piv->len],
34 id_piv->len, id_piv->ptr, id_piv->len));
35
36 /* "3. concatenating the size of the ID_PIV (a single byte S) with the padded ID_PIV and the padded PIV,"*/
37 nonce->ptr[0] = (uint8_t)id_piv->len;
38 TRY(_memcpy_s(&nonce->ptr[1], padded_id_piv_len, padded_id_piv,
39 padded_id_piv_len));
40
41 TRY(_memcpy_s(&nonce->ptr[1 + sizeof(padded_id_piv)],
42 sizeof(padded_piv), padded_piv, sizeof(padded_piv)));
43
44 PRINT_ARRAY("nonce input A", nonce->ptr, nonce->len);
45 PRINT_ARRAY("nonce input B", common_iv->ptr, common_iv->len);
46 /* "4. and then XORing with the Common IV."*/
47 for (uint32_t i = 0; i < common_iv->len; i++) {
48 nonce->ptr[i] ^= common_iv->ptr[i];
49 }
50
51 PRINT_ARRAY("nonce", nonce->ptr, nonce->len);
52 return ok;
53 }
54
