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/*
* Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/* chacha20 cipher implementation */
#include "cipher_chacha20.h"
static int chacha20_initkey(PROV_CIPHER_CTX *bctx, const uint8_t *key,
size_t keylen)
{
PROV_CHACHA20_CTX *ctx = (PROV_CHACHA20_CTX *)bctx;
unsigned int i;
if (key != NULL) {
for (i = 0; i < CHACHA_KEY_SIZE; i += 4)
ctx->key.d[i / 4] = CHACHA_U8TOU32(key + i);
}
ctx->partial_len = 0;
return 1;
}
static int chacha20_initiv(PROV_CIPHER_CTX *bctx)
{
PROV_CHACHA20_CTX *ctx = (PROV_CHACHA20_CTX *)bctx;
unsigned int i;
if (bctx->iv_set) {
for (i = 0; i < CHACHA_CTR_SIZE; i += 4)
ctx->counter[i / 4] = CHACHA_U8TOU32(bctx->oiv + i);
}
ctx->partial_len = 0;
return 1;
}
static int chacha20_cipher(PROV_CIPHER_CTX *bctx, unsigned char *out,
const unsigned char *in, size_t inl)
{
PROV_CHACHA20_CTX *ctx = (PROV_CHACHA20_CTX *)bctx;
unsigned int n, rem, ctr32;
n = ctx->partial_len;
if (n > 0) {
while (inl > 0 && n < CHACHA_BLK_SIZE) {
*out++ = *in++ ^ ctx->buf[n++];
inl--;
}
ctx->partial_len = n;
if (inl == 0)
return 1;
if (n == CHACHA_BLK_SIZE) {
ctx->partial_len = 0;
ctx->counter[0]++;
if (ctx->counter[0] == 0)
ctx->counter[1]++;
}
}
rem = (unsigned int)(inl % CHACHA_BLK_SIZE);
inl -= rem;
ctr32 = ctx->counter[0];
while (inl >= CHACHA_BLK_SIZE) {
size_t blocks = inl / CHACHA_BLK_SIZE;
/*
* 1<<28 is just a not-so-small yet not-so-large number...
* Below condition is practically never met, but it has to
* be checked for code correctness.
*/
if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
blocks = (1U << 28);
/*
* As ChaCha20_ctr32 operates on 32-bit counter, caller
* has to handle overflow. 'if' below detects the
* overflow, which is then handled by limiting the
* amount of blocks to the exact overflow point...
*/
ctr32 += (unsigned int)blocks;
if (ctr32 < blocks) {
blocks -= ctr32;
ctr32 = 0;
}
blocks *= CHACHA_BLK_SIZE;
ChaCha20_ctr32(out, in, blocks, ctx->key.d, ctx->counter);
inl -= blocks;
in += blocks;
out += blocks;
ctx->counter[0] = ctr32;
if (ctr32 == 0) ctx->counter[1]++;
}
if (rem > 0) {
memset(ctx->buf, 0, sizeof(ctx->buf));
ChaCha20_ctr32(ctx->buf, ctx->buf, CHACHA_BLK_SIZE,
ctx->key.d, ctx->counter);
for (n = 0; n < rem; n++)
out[n] = in[n] ^ ctx->buf[n];
ctx->partial_len = rem;
}
return 1;
}
static const PROV_CIPHER_HW_CHACHA20 chacha20_hw = {
{ chacha20_initkey, chacha20_cipher },
chacha20_initiv
};
const PROV_CIPHER_HW *ossl_prov_cipher_hw_chacha20(size_t keybits)
{
return (PROV_CIPHER_HW *)&chacha20_hw;
}
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