1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3 #include "tomcrypt_private.h"
4
5 /**
6 @file xcbc_done.c
7 XCBC Support, terminate the state
8 */
9
10 #ifdef LTC_XCBC
11
12 /** Terminate the XCBC-MAC state
13 @param xcbc XCBC state to terminate
14 @param out [out] Destination for the MAC tag
15 @param outlen [in/out] Destination size and final tag size
16 Return CRYPT_OK on success
17 */
xcbc_done(xcbc_state * xcbc,unsigned char * out,unsigned long * outlen)18 int xcbc_done(xcbc_state *xcbc, unsigned char *out, unsigned long *outlen)
19 {
20 int err, x;
21 LTC_ARGCHK(xcbc != NULL);
22 LTC_ARGCHK(out != NULL);
23
24 /* check structure */
25 if ((err = cipher_is_valid(xcbc->cipher)) != CRYPT_OK) {
26 return err;
27 }
28
29 if ((xcbc->blocksize > cipher_descriptor[xcbc->cipher]->block_length) || (xcbc->blocksize < 0) ||
30 (xcbc->buflen > xcbc->blocksize) || (xcbc->buflen < 0)) {
31 return CRYPT_INVALID_ARG;
32 }
33
34 /* which key do we use? */
35 if (xcbc->buflen == xcbc->blocksize) {
36 /* k2 */
37 for (x = 0; x < xcbc->blocksize; x++) {
38 xcbc->IV[x] ^= xcbc->K[1][x];
39 }
40 } else {
41 xcbc->IV[xcbc->buflen] ^= 0x80;
42 /* k3 */
43 for (x = 0; x < xcbc->blocksize; x++) {
44 xcbc->IV[x] ^= xcbc->K[2][x];
45 }
46 }
47
48 /* encrypt */
49 cipher_descriptor[xcbc->cipher]->ecb_encrypt(xcbc->IV, xcbc->IV, &xcbc->key);
50 cipher_descriptor[xcbc->cipher]->done(&xcbc->key);
51
52 /* extract tag */
53 for (x = 0; x < xcbc->blocksize && (unsigned long)x < *outlen; x++) {
54 out[x] = xcbc->IV[x];
55 }
56 *outlen = x;
57
58 #ifdef LTC_CLEAN_STACK
59 zeromem(xcbc, sizeof(*xcbc));
60 #endif
61 return CRYPT_OK;
62 }
63
64 #endif
65
66