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/*
* This code is shared between crypto_aesctr*.c files, and should not be
* compiled as a separate translation unit. For details, see the comments in
* those files.
*/
/* AES-CTR state. */
struct crypto_aesctr {
const struct crypto_aes_key * key;
uint64_t bytectr;
uint8_t buf[16];
uint8_t pblk[16];
};
/* Generate a block of cipherstream. */
static inline void
crypto_aesctr_stream_cipherblock_generate(struct crypto_aesctr * stream)
{
/* Sanity check. */
assert(stream->bytectr % 16 == 0);
/* Prepare counter. */
stream->pblk[15]++;
if (stream->pblk[15] == 0) {
/*
* If incrementing the least significant byte resulted in it
* wrapping, re-encode the complete 64-bit value.
*/
be64enc(stream->pblk + 8, stream->bytectr / 16);
}
/* Encrypt the cipherblock. */
crypto_aes_encrypt_block(stream->pblk, stream->buf, stream->key);
}
/* Encrypt ${nbytes} bytes, then update ${inbuf}, ${outbuf}, and ${buflen}. */
static inline void
crypto_aesctr_stream_cipherblock_use(struct crypto_aesctr * stream,
const uint8_t ** inbuf, uint8_t ** outbuf, size_t * buflen, size_t nbytes,
size_t bytemod)
{
size_t i;
/* Encrypt the byte(s). */
for (i = 0; i < nbytes; i++)
(*outbuf)[i] = (*inbuf)[i] ^ stream->buf[bytemod + i];
/* Move to the next byte(s) of cipherstream. */
stream->bytectr += nbytes;
/* Update the positions. */
*inbuf += nbytes;
*outbuf += nbytes;
*buflen -= nbytes;
}
/*
* Process any bytes before we can process a whole block. Return 1 if there
* are no bytes left to process after calling this function.
*/
static inline int
crypto_aesctr_stream_pre_wholeblock(struct crypto_aesctr * stream,
const uint8_t ** inbuf, uint8_t ** outbuf, size_t * buflen_p)
{
size_t bytemod;
/* Do we have any bytes left in the current cipherblock? */
bytemod = stream->bytectr % 16;
if (bytemod != 0) {
/* Do we have enough to complete the request? */
if (bytemod + *buflen_p <= 16) {
/* Process only buflen bytes, then return. */
crypto_aesctr_stream_cipherblock_use(stream, inbuf,
outbuf, buflen_p, *buflen_p, bytemod);
return (1);
}
/* Encrypt the byte(s) and update the positions. */
crypto_aesctr_stream_cipherblock_use(stream, inbuf, outbuf,
buflen_p, 16 - bytemod, bytemod);
}
/* Success! */
return (0);
}
/* Process any final bytes after finishing all whole blocks. */
static inline void
crypto_aesctr_stream_post_wholeblock(struct crypto_aesctr * stream,
const uint8_t ** inbuf, uint8_t ** outbuf, size_t * buflen_p)
{
/* Process any final bytes; we need a new cipherblock. */
if (*buflen_p > 0) {
/* Generate a block of cipherstream. */
crypto_aesctr_stream_cipherblock_generate(stream);
/* Encrypt the byte(s) and update the positions. */
crypto_aesctr_stream_cipherblock_use(stream, inbuf, outbuf,
buflen_p, *buflen_p, 0);
}
}
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