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
12/**
13   @file ocb_done_decrypt.c
14   OCB implementation, terminate decryption, by Tom St Denis
15*/
16#include "tomcrypt.h"
17
18#ifdef OCB_MODE
19
20/**
21   Terminate a decrypting OCB state
22   @param ocb    The OCB state
23   @param ct     The ciphertext (if any)
24   @param ctlen  The length of the ciphertext (octets)
25   @param pt     [out] The plaintext
26   @param tag    The authentication tag (to compare against)
27   @param taglen The length of the authentication tag provided
28   @param stat    [out] The result of the tag comparison
29   @return CRYPT_OK if the process was successful regardless if the tag is valid
30*/
31int ocb_done_decrypt(ocb_state *ocb,
32                     const unsigned char *ct,  unsigned long ctlen,
33                           unsigned char *pt,
34                     const unsigned char *tag, unsigned long taglen, int *stat)
35{
36   int err;
37   unsigned char *tagbuf;
38   unsigned long tagbuflen;
39
40   LTC_ARGCHK(ocb  != NULL);
41   LTC_ARGCHK(pt   != NULL);
42   LTC_ARGCHK(ct   != NULL);
43   LTC_ARGCHK(tag  != NULL);
44   LTC_ARGCHK(stat != NULL);
45
46   /* default to failed */
47   *stat = 0;
48
49   /* allocate memory */
50   tagbuf = XMALLOC(MAXBLOCKSIZE);
51   if (tagbuf == NULL) {
52      return CRYPT_MEM;
53   }
54
55   tagbuflen = MAXBLOCKSIZE;
56   if ((err = s_ocb_done(ocb, ct, ctlen, pt, tagbuf, &tagbuflen, 1)) != CRYPT_OK) {
57      goto LBL_ERR;
58   }
59
60   if (taglen <= tagbuflen && XMEMCMP(tagbuf, tag, taglen) == 0) {
61      *stat = 1;
62   }
63
64   err = CRYPT_OK;
65LBL_ERR:
66#ifdef LTC_CLEAN_STACK
67   zeromem(tagbuf, MAXBLOCKSIZE);
68#endif
69
70   XFREE(tagbuf);
71
72   return err;
73}
74
75#endif
76
77
78/* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_done_decrypt.c,v $ */
79/* $Revision: 1.5 $ */
80/* $Date: 2006/11/01 09:28:17 $ */
81