1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3 #include "tomcrypt_private.h"
4
5 /**
6 @file omac_done.c
7 OMAC1 support, terminate a stream, Tom St Denis
8 */
9
10 #ifdef LTC_OMAC
11
12 /**
13 Terminate an OMAC stream
14 @param omac The OMAC state
15 @param out [out] Destination for the authentication tag
16 @param outlen [in/out] The max size and resulting size of the authentication tag
17 @return CRYPT_OK if successful
18 */
omac_done(omac_state * omac,unsigned char * out,unsigned long * outlen)19 int omac_done(omac_state *omac, unsigned char *out, unsigned long *outlen)
20 {
21 int err, mode;
22 unsigned x;
23
24 LTC_ARGCHK(omac != NULL);
25 LTC_ARGCHK(out != NULL);
26 LTC_ARGCHK(outlen != NULL);
27 if ((err = cipher_is_valid(omac->cipher_idx)) != CRYPT_OK) {
28 return err;
29 }
30
31 if ((omac->buflen > (int)sizeof(omac->block)) || (omac->buflen < 0) ||
32 (omac->blklen > (int)sizeof(omac->block)) || (omac->buflen > omac->blklen)) {
33 return CRYPT_INVALID_ARG;
34 }
35
36 /* figure out mode */
37 if (omac->buflen != omac->blklen) {
38 /* add the 0x80 byte */
39 omac->block[omac->buflen++] = 0x80;
40
41 /* pad with 0x00 */
42 while (omac->buflen < omac->blklen) {
43 omac->block[omac->buflen++] = 0x00;
44 }
45 mode = 1;
46 } else {
47 mode = 0;
48 }
49
50 /* now xor prev + Lu[mode] */
51 for (x = 0; x < (unsigned)omac->blklen; x++) {
52 omac->block[x] ^= omac->prev[x] ^ omac->Lu[mode][x];
53 }
54
55 /* encrypt it */
56 if ((err = cipher_descriptor[omac->cipher_idx]->ecb_encrypt(omac->block, omac->block, &omac->key)) != CRYPT_OK) {
57 return err;
58 }
59 cipher_descriptor[omac->cipher_idx]->done(&omac->key);
60
61 /* output it */
62 for (x = 0; x < (unsigned)omac->blklen && x < *outlen; x++) {
63 out[x] = omac->block[x];
64 }
65 *outlen = x;
66
67 #ifdef LTC_CLEAN_STACK
68 zeromem(omac, sizeof(*omac));
69 #endif
70 return CRYPT_OK;
71 }
72
73 #endif
74
75