/* LibTomCrypt, modular cryptographic library -- Tom St Denis */

/* SPDX-License-Identifier: Unlicense */

#include "tomcrypt_private.h"

#ifdef LTC_CCM_MODE

/**

  Terminate a CCM stream

  @param ccm     The CCM state

  @param tag     [out] The destination for the MAC tag

  @param taglen  [in/out]  The length of the MAC tag

  @return CRYPT_OK on success

 */

int ccm_done(ccm_state *ccm,

             unsigned char *tag,    unsigned long *taglen)

{

   unsigned long x, y;

   int            err;

   LTC_ARGCHK(ccm != NULL);

   /* Check all data have been processed */

   if (ccm->ptlen != ccm->current_ptlen) {

      return CRYPT_ERROR;

   }

   LTC_ARGCHK(tag    != NULL);

   LTC_ARGCHK(taglen != NULL);

   if (ccm->x != 0) {

      if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->PAD, ccm->PAD, &ccm->K)) != CRYPT_OK) {

         return err;

      }

   }

   /* setup CTR for the TAG (zero the count) */

   for (y = 15; y > 15 - ccm->L; y--) {

      ccm->ctr[y] = 0x00;

   }

   if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->ctr, ccm->CTRPAD, &ccm->K)) != CRYPT_OK) {

      return err;

   }

   cipher_descriptor[ccm->cipher].done(&ccm->K);

   /* store the TAG */

   for (x = 0; x < 16 && x < *taglen; x++) {

      tag[x] = ccm->PAD[x] ^ ccm->CTRPAD[x];

   }

   *taglen = x;

   return CRYPT_OK;

}

#endif