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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.
*/
#include "tomcrypt.h"
#ifdef LTC_CCM_MODE
/**
Add nonce data to the CCM state
@param ccm The CCM state
@param nonce The nonce data to add
@param noncelen The length of the nonce
@return CRYPT_OK on success
*/
int ccm_add_nonce(ccm_state *ccm,
const unsigned char *nonce, unsigned long noncelen)
{
unsigned long x, y, len;
int err;
LTC_ARGCHK(ccm != NULL);
LTC_ARGCHK(nonce != NULL);
/* increase L to match the nonce len */
ccm->noncelen = (noncelen > 13) ? 13 : noncelen;
if ((15 - ccm->noncelen) > ccm->L) {
ccm->L = 15 - ccm->noncelen;
}
/* decrease noncelen to match L */
if ((ccm->noncelen + ccm->L) > 15) {
ccm->noncelen = 15 - ccm->L;
}
/* form B_0 == flags | Nonce N | l(m) */
x = 0;
ccm->PAD[x++] = (unsigned char)(((ccm->aadlen > 0) ? (1<<6) : 0) |
(((ccm->taglen - 2)>>1)<<3) |
(ccm->L-1));
/* nonce */
for (y = 0; y < (16 - (ccm->L + 1)); y++) {
ccm->PAD[x++] = nonce[y];
}
/* store len */
len = ccm->ptlen;
/* shift len so the upper bytes of len are the contents of the length */
for (y = ccm->L; y < 4; y++) {
len <<= 8;
}
/* store l(m) (only store 32-bits) */
for (y = 0; ccm->L > 4 && (ccm->L-y)>4; y++) {
ccm->PAD[x++] = 0;
}
for (; y < ccm->L; y++) {
ccm->PAD[x++] = (unsigned char)((len >> 24) & 255);
len <<= 8;
}
/* encrypt PAD */
if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->PAD, ccm->PAD, &ccm->K)) != CRYPT_OK) {
return err;
}
/* handle header */
ccm->x = 0;
if (ccm->aadlen > 0) {
/* store length */
if (ccm->aadlen < ((1UL<<16) - (1UL<<8))) {
ccm->PAD[ccm->x++] ^= (ccm->aadlen>>8) & 255;
ccm->PAD[ccm->x++] ^= ccm->aadlen & 255;
} else {
ccm->PAD[ccm->x++] ^= 0xFF;
ccm->PAD[ccm->x++] ^= 0xFE;
ccm->PAD[ccm->x++] ^= (ccm->aadlen>>24) & 255;
ccm->PAD[ccm->x++] ^= (ccm->aadlen>>16) & 255;
ccm->PAD[ccm->x++] ^= (ccm->aadlen>>8) & 255;
ccm->PAD[ccm->x++] ^= ccm->aadlen & 255;
}
}
/* setup the ctr counter */
x = 0;
/* flags */
ccm->ctr[x++] = (unsigned char)ccm->L-1;
/* nonce */
for (y = 0; y < (16 - (ccm->L+1)); ++y) {
ccm->ctr[x++] = nonce[y];
}
/* offset */
while (x < 16) {
ccm->ctr[x++] = 0;
}
ccm->CTRlen = 16;
return CRYPT_OK;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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