56 lines
1.3 KiB
C
56 lines
1.3 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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#include "tomcrypt_private.h"
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#ifdef LTC_CCM_MODE
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/**
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Terminate a CCM stream
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@param ccm The CCM state
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@param tag [out] The destination for the MAC tag
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@param taglen [in/out] The length of the MAC tag
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@return CRYPT_OK on success
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*/
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int ccm_done(ccm_state *ccm,
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unsigned char *tag, unsigned long *taglen)
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{
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unsigned long x, y;
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int err;
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LTC_ARGCHK(ccm != NULL);
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/* Check all data have been processed */
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if (ccm->ptlen != ccm->current_ptlen) {
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return CRYPT_ERROR;
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}
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LTC_ARGCHK(tag != NULL);
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LTC_ARGCHK(taglen != NULL);
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if (ccm->x != 0) {
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if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->PAD, ccm->PAD, &ccm->K)) != CRYPT_OK) {
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return err;
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}
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}
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/* setup CTR for the TAG (zero the count) */
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for (y = 15; y > 15 - ccm->L; y--) {
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ccm->ctr[y] = 0x00;
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}
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if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->ctr, ccm->CTRPAD, &ccm->K)) != CRYPT_OK) {
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return err;
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}
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cipher_descriptor[ccm->cipher].done(&ccm->K);
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/* store the TAG */
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for (x = 0; x < 16 && x < *taglen; x++) {
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tag[x] = ccm->PAD[x] ^ ccm->CTRPAD[x];
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}
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*taglen = x;
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return CRYPT_OK;
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}
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#endif
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