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/* Copyright (c) 2014, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
/* Adapted from the public domain, estream code by D. Bernstein. */
#include <openssl/chacha.h>
#include <string.h>
#include <openssl/cpu.h>
#if defined(OPENSSL_WINDOWS) || (!defined(OPENSSL_X86_64) && !defined(OPENSSL_X86)) || !defined(__SSE2__)
/* sigma contains the ChaCha constants, which happen to be an ASCII string. */
static const uint8_t sigma[16] = { 'e', 'x', 'p', 'a', 'n', 'd', ' ', '3',
'2', '-', 'b', 'y', 't', 'e', ' ', 'k' };
#define ROTATE(v, n) (((v) << (n)) | ((v) >> (32 - (n))))
#define XOR(v, w) ((v) ^ (w))
#define PLUS(x, y) ((x) + (y))
#define PLUSONE(v) (PLUS((v), 1))
#define U32TO8_LITTLE(p, v) \
{ \
(p)[0] = (v >> 0) & 0xff; \
(p)[1] = (v >> 8) & 0xff; \
(p)[2] = (v >> 16) & 0xff; \
(p)[3] = (v >> 24) & 0xff; \
}
#define U8TO32_LITTLE(p) \
(((uint32_t)((p)[0])) | ((uint32_t)((p)[1]) << 8) | \
((uint32_t)((p)[2]) << 16) | ((uint32_t)((p)[3]) << 24))
/* QUARTERROUND updates a, b, c, d with a ChaCha "quarter" round. */
#define QUARTERROUND(a,b,c,d) \
x[a] = PLUS(x[a],x[b]); x[d] = ROTATE(XOR(x[d],x[a]),16); \
x[c] = PLUS(x[c],x[d]); x[b] = ROTATE(XOR(x[b],x[c]),12); \
x[a] = PLUS(x[a],x[b]); x[d] = ROTATE(XOR(x[d],x[a]), 8); \
x[c] = PLUS(x[c],x[d]); x[b] = ROTATE(XOR(x[b],x[c]), 7);
#if defined(OPENSSL_ARM) && !defined(OPENSSL_NO_ASM)
/* Defined in chacha_vec.c */
void CRYPTO_chacha_20_neon(uint8_t *out, const uint8_t *in, size_t in_len,
const uint8_t key[32], const uint8_t nonce[12],
uint32_t counter);
#endif
/* chacha_core performs 20 rounds of ChaCha on the input words in
* |input| and writes the 64 output bytes to |output|. */
static void chacha_core(uint8_t output[64], const uint32_t input[16]) {
uint32_t x[16];
int i;
memcpy(x, input, sizeof(uint32_t) * 16);
for (i = 20; i > 0; i -= 2) {
QUARTERROUND(0, 4, 8, 12)
QUARTERROUND(1, 5, 9, 13)
QUARTERROUND(2, 6, 10, 14)
QUARTERROUND(3, 7, 11, 15)
QUARTERROUND(0, 5, 10, 15)
QUARTERROUND(1, 6, 11, 12)
QUARTERROUND(2, 7, 8, 13)
QUARTERROUND(3, 4, 9, 14)
}
for (i = 0; i < 16; ++i) {
x[i] = PLUS(x[i], input[i]);
}
for (i = 0; i < 16; ++i) {
U32TO8_LITTLE(output + 4 * i, x[i]);
}
}
void CRYPTO_chacha_20(uint8_t *out, const uint8_t *in, size_t in_len,
const uint8_t key[32], const uint8_t nonce[12],
uint32_t counter) {
uint32_t input[16];
uint8_t buf[64];
size_t todo, i;
#if defined(OPENSSL_ARM) && !defined(OPENSSL_NO_ASM)
if (CRYPTO_is_NEON_capable()) {
CRYPTO_chacha_20_neon(out, in, in_len, key, nonce, counter);
return;
}
#endif
input[0] = U8TO32_LITTLE(sigma + 0);
input[1] = U8TO32_LITTLE(sigma + 4);
input[2] = U8TO32_LITTLE(sigma + 8);
input[3] = U8TO32_LITTLE(sigma + 12);
input[4] = U8TO32_LITTLE(key + 0);
input[5] = U8TO32_LITTLE(key + 4);
input[6] = U8TO32_LITTLE(key + 8);
input[7] = U8TO32_LITTLE(key + 12);
input[8] = U8TO32_LITTLE(key + 16);
input[9] = U8TO32_LITTLE(key + 20);
input[10] = U8TO32_LITTLE(key + 24);
input[11] = U8TO32_LITTLE(key + 28);
input[12] = counter;
input[13] = U8TO32_LITTLE(nonce + 0);
input[14] = U8TO32_LITTLE(nonce + 4);
input[15] = U8TO32_LITTLE(nonce + 8);
while (in_len > 0) {
todo = sizeof(buf);
if (in_len < todo) {
todo = in_len;
}
chacha_core(buf, input);
for (i = 0; i < todo; i++) {
out[i] = in[i] ^ buf[i];
}
out += todo;
in += todo;
in_len -= todo;
input[12]++;
}
}
#endif /* OPENSSL_WINDOWS || !OPENSSL_X86_64 && !OPENSSL_X86 || !__SSE2__ */
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