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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
/**
Process plaintext/ciphertext through CCM
@param ccm The CCM state
@param pt The plaintext
@param ptlen The plaintext length (ciphertext length is the same)
@param ct The ciphertext
@param direction Encrypt or Decrypt mode (CCM_ENCRYPT or CCM_DECRYPT)
@return CRYPT_OK on success
*/
int ccm_process(ccm_state *ccm,
unsigned char *pt, unsigned long ptlen,
unsigned char *ct,
int direction)
{
unsigned char z, b;
unsigned long y;
int err;
LTC_ARGCHK(ccm != NULL);
/* Check aad has been correctly added */
if (ccm->aadlen != ccm->current_aadlen) {
return CRYPT_ERROR;
}
/* Check we do not process too much data */
if (ccm->ptlen < ccm->current_ptlen + ptlen) {
return CRYPT_ERROR;
}
ccm->current_ptlen += ptlen;
/* now handle the PT */
if (ptlen > 0) {
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
for (y = 0; y < ptlen; y++) {
/* increment the ctr? */
if (ccm->CTRlen == 16) {
for (z = 15; z > 15-ccm->L; z--) {
ccm->ctr[z] = (ccm->ctr[z] + 1) & 255;
if (ccm->ctr[z]) break;
}
if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->ctr, ccm->CTRPAD, &ccm->K)) != CRYPT_OK) {
return err;
}
ccm->CTRlen = 0;
}
/* if we encrypt we add the bytes to the MAC first */
if (direction == CCM_ENCRYPT) {
b = pt[y];
ct[y] = b ^ ccm->CTRPAD[ccm->CTRlen++];
} else {
b = ct[y] ^ ccm->CTRPAD[ccm->CTRlen++];
pt[y] = b;
}
if (ccm->x == 16) {
if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->PAD, ccm->PAD, &ccm->K)) != CRYPT_OK) {
return err;
}
ccm->x = 0;
}
ccm->PAD[ccm->x++] ^= b;
}
}
return CRYPT_OK;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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