int ccmode_ctr_setctr(CC_UNUSED const struct ccmode_ctr *mode, ccctr_ctx *ctx, const void *ctr)
{
CCMODE_CTR_KEY_PAD_OFFSET(ctx) = CCMODE_CTR_KEY_ECB(ctx)->block_size;
CC_MEMCPY(CCMODE_CTR_KEY_CTR(ctx), ctr, CCMODE_CTR_KEY_ECB(ctx)->block_size);
return 0;
}
void ccmode_ctr_crypt(ccctr_ctx *key,
size_t nbytes, const void *in, void *out) {
const struct ccmode_ecb *ecb = CCMODE_CTR_KEY_ECB(key);
const ccecb_ctx *ecb_key = CCMODE_CTR_KEY_ECB_KEY(key);
uint8_t *ctr = (uint8_t *)CCMODE_CTR_KEY_CTR(key);
uint8_t *pad = (uint8_t *)CCMODE_CTR_KEY_PAD(key);
cc_size pad_len = CCMODE_CTR_KEY_PAD_LEN(key);
const uint8_t *pt = in;
// Counter is 64bit wide for cipher with block size of 64bit or more
// This is to match the assembly
const size_t counter_size=(CC_MIN(ecb->block_size,(typeof(ecb->block_size))8));
uint8_t *ct = out;
while (nbytes) {
if (pad_len == ecb->block_size) {
ecb->ecb(ecb_key, 1, ctr, pad);
pad_len = 0;
/* increment the big endian counter */
for (size_t x = ecb->block_size; x-- > (ecb->block_size-counter_size);) {
ctr[x] = (ctr[x] + (unsigned char)1) & (unsigned char)255;
if (ctr[x] != (unsigned char)0) {
break;
}
}
if (nbytes==0) break;
}
/* TODO: Make sure this works. If pt and ct aren't aligned this
might not work right. */
#if 0
if (pad_len == 0 && nbytes >= ecb->block_size) {
ccn_xor(ecb->block_size / CCN_UNIT_SIZE, ct, pt, pad);
pad_len = ecb->block_size;
pt += pad_len;
ct += pad_len;
nbytes -= pad_len;
}
#endif
do {
*ct++ = *pt++ ^ pad[pad_len++];
--nbytes;
} while ((nbytes>0)&&(pad_len<ecb->block_size));
}
CCMODE_CTR_KEY_PAD_LEN(key) = pad_len;
}