107 lines
2.6 KiB
C
107 lines
2.6 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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Add nonce data to the CCM state
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@param ccm The CCM state
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@param nonce The nonce data to add
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@param noncelen The length of the nonce
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@return CRYPT_OK on success
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*/
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int ccm_add_nonce(ccm_state *ccm,
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const unsigned char *nonce, unsigned long noncelen)
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{
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unsigned long x, y, len;
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int err;
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LTC_ARGCHK(ccm != NULL);
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LTC_ARGCHK(nonce != NULL);
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/* increase L to match the nonce len */
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ccm->noncelen = (noncelen > 13) ? 13 : noncelen;
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if ((15 - ccm->noncelen) > ccm->L) {
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ccm->L = 15 - ccm->noncelen;
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}
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if (ccm->L > 8) {
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return CRYPT_INVALID_ARG;
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}
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/* decrease noncelen to match L */
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if ((ccm->noncelen + ccm->L) > 15) {
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ccm->noncelen = 15 - ccm->L;
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}
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/* form B_0 == flags | Nonce N | l(m) */
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x = 0;
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ccm->PAD[x++] = (unsigned char)(((ccm->aadlen > 0) ? (1<<6) : 0) |
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(((ccm->taglen - 2)>>1)<<3) |
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(ccm->L-1));
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/* nonce */
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for (y = 0; y < 15 - ccm->L; y++) {
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ccm->PAD[x++] = nonce[y];
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}
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/* store len */
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len = ccm->ptlen;
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/* shift len so the upper bytes of len are the contents of the length */
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for (y = ccm->L; y < 4; y++) {
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len <<= 8;
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}
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/* store l(m) (only store 32-bits) */
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for (y = 0; ccm->L > 4 && (ccm->L-y)>4; y++) {
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ccm->PAD[x++] = 0;
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}
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for (; y < ccm->L; y++) {
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ccm->PAD[x++] = (unsigned char)((len >> 24) & 255);
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len <<= 8;
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}
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/* encrypt PAD */
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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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/* handle header */
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ccm->x = 0;
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if (ccm->aadlen > 0) {
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/* store length */
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if (ccm->aadlen < ((1UL<<16) - (1UL<<8))) {
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ccm->PAD[ccm->x++] ^= (ccm->aadlen>>8) & 255;
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ccm->PAD[ccm->x++] ^= ccm->aadlen & 255;
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} else {
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ccm->PAD[ccm->x++] ^= 0xFF;
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ccm->PAD[ccm->x++] ^= 0xFE;
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ccm->PAD[ccm->x++] ^= (ccm->aadlen>>24) & 255;
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ccm->PAD[ccm->x++] ^= (ccm->aadlen>>16) & 255;
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ccm->PAD[ccm->x++] ^= (ccm->aadlen>>8) & 255;
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ccm->PAD[ccm->x++] ^= ccm->aadlen & 255;
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}
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}
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/* setup the ctr counter */
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x = 0;
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/* flags */
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ccm->ctr[x++] = (unsigned char)ccm->L-1;
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/* nonce */
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for (y = 0; y < (16 - (ccm->L+1)); ++y) {
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ccm->ctr[x++] = nonce[y];
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}
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/* offset */
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while (x < 16) {
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ccm->ctr[x++] = 0;
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}
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ccm->CTRlen = 16;
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return CRYPT_OK;
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}
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#endif
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