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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
*/
/**
@file eax_done.c
EAX implementation, terminate session, by Tom St Denis
*/
#include "tomcrypt.h"
#ifdef EAX_MODE
/**
Terminate an EAX session and get the tag.
@param eax The EAX state
@param tag [out] The destination of the authentication tag
@param taglen [in/out] The max length and resulting length of the authentication tag
@return CRYPT_OK if successful
*/
int eax_done(eax_state *eax, unsigned char *tag, unsigned long *taglen)
{
int err;
unsigned char *headermac, *ctmac;
unsigned long x, len;
LTC_ARGCHK(eax != NULL);
LTC_ARGCHK(tag != NULL);
LTC_ARGCHK(taglen != NULL);
/* allocate ram */
headermac = XMALLOC(MAXBLOCKSIZE);
ctmac = XMALLOC(MAXBLOCKSIZE);
if (headermac == NULL || ctmac == NULL) {
if (headermac != NULL) {
XFREE(headermac);
}
if (ctmac != NULL) {
XFREE(ctmac);
}
return CRYPT_MEM;
}
/* finish ctomac */
len = MAXBLOCKSIZE;
if ((err = omac_done(&eax->ctomac, ctmac, &len)) != CRYPT_OK) {
goto LBL_ERR;
}
/* finish headeromac */
/* note we specifically don't reset len so the two lens are minimal */
if ((err = omac_done(&eax->headeromac, headermac, &len)) != CRYPT_OK) {
goto LBL_ERR;
}
/* terminate the CTR chain */
if ((err = ctr_done(&eax->ctr)) != CRYPT_OK) {
goto LBL_ERR;
}
/* compute N xor H xor C */
for (x = 0; x < len && x < *taglen; x++) {
tag[x] = eax->N[x] ^ headermac[x] ^ ctmac[x];
}
*taglen = x;
err = CRYPT_OK;
LBL_ERR:
#ifdef LTC_CLEAN_STACK
zeromem(ctmac, MAXBLOCKSIZE);
zeromem(headermac, MAXBLOCKSIZE);
zeromem(eax, sizeof(*eax));
#endif
XFREE(ctmac);
XFREE(headermac);
return err;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/encauth/eax/eax_done.c,v $ */
/* $Revision: 1.5 $ */
/* $Date: 2006/03/31 14:15:35 $ */
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