1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11 #include "tomcrypt.h"
12
13 /**
14 @file omac_done.c
15 OMAC1 support, terminate a stream, Tom St Denis
16 */
17
18 #ifdef LTC_OMAC
19
20 /**
21 Terminate an OMAC stream
22 @param omac The OMAC state
23 @param out [out] Destination for the authentication tag
24 @param outlen [in/out] The max size and resulting size of the authentication tag
25 @return CRYPT_OK if successful
26 */
omac_done(omac_state * omac,unsigned char * out,unsigned long * outlen)27 int omac_done(omac_state *omac, unsigned char *out, unsigned long *outlen)
28 {
29 int err, mode;
30 unsigned x;
31
32 LTC_ARGCHK(omac != NULL);
33 LTC_ARGCHK(out != NULL);
34 LTC_ARGCHK(outlen != NULL);
35 if ((err = cipher_is_valid(omac->cipher_idx)) != CRYPT_OK) {
36 return err;
37 }
38
39 if ((omac->buflen > (int)sizeof(omac->block)) || (omac->buflen < 0) ||
40 (omac->blklen > (int)sizeof(omac->block)) || (omac->buflen > omac->blklen)) {
41 return CRYPT_INVALID_ARG;
42 }
43
44 /* figure out mode */
45 if (omac->buflen != omac->blklen) {
46 /* add the 0x80 byte */
47 omac->block[omac->buflen++] = 0x80;
48
49 /* pad with 0x00 */
50 while (omac->buflen < omac->blklen) {
51 omac->block[omac->buflen++] = 0x00;
52 }
53 mode = 1;
54 } else {
55 mode = 0;
56 }
57
58 /* now xor prev + Lu[mode] */
59 for (x = 0; x < (unsigned)omac->blklen; x++) {
60 omac->block[x] ^= omac->prev[x] ^ omac->Lu[mode][x];
61 }
62
63 /* encrypt it */
64 if ((err = cipher_descriptor[omac->cipher_idx].ecb_encrypt(omac->block, omac->block, &omac->key)) != CRYPT_OK) {
65 return err;
66 }
67 cipher_descriptor[omac->cipher_idx].done(&omac->key);
68
69 /* output it */
70 for (x = 0; x < (unsigned)omac->blklen && x < *outlen; x++) {
71 out[x] = omac->block[x];
72 }
73 *outlen = x;
74
75 #ifdef LTC_CLEAN_STACK
76 zeromem(omac, sizeof(*omac));
77 #endif
78 return CRYPT_OK;
79 }
80
81 #endif
82
83
84 /* $Source: /cvs/libtom/libtomcrypt/src/mac/omac/omac_done.c,v $ */
85 /* $Revision: 1.7 $ */
86 /* $Date: 2006/11/03 00:39:49 $ */
87