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*/
27int 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