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