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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* Implementation of the ChaCha20 stream cipher.
*
* Information: https://cr.yp.to/chacha.html
*/
#include <zinc/chacha20.h>
#include <linux/kernel.h>
#include <crypto/algapi.h>
#ifndef HAVE_CHACHA20_ARCH_IMPLEMENTATION
void __init chacha20_fpu_init(void)
{
}
static inline bool chacha20_arch(u8 *out, const u8 *in, const size_t len,
const u32 key[8], const u32 counter[4],
simd_context_t simd_context)
{
return false;
}
static inline bool hchacha20_arch(u8 *derived_key, const u8 *nonce,
const u8 *key, simd_context_t simd_context)
{
return false;
}
#endif
#define EXPAND_32_BYTE_K 0x61707865U, 0x3320646eU, 0x79622d32U, 0x6b206574U
#define QUARTER_ROUND(x, a, b, c, d) ( \
x[a] += x[b], \
x[d] = rol32((x[d] ^ x[a]), 16), \
x[c] += x[d], \
x[b] = rol32((x[b] ^ x[c]), 12), \
x[a] += x[b], \
x[d] = rol32((x[d] ^ x[a]), 8), \
x[c] += x[d], \
x[b] = rol32((x[b] ^ x[c]), 7) \
)
#define C(i, j) (i * 4 + j)
#define DOUBLE_ROUND(x) ( \
/* Column Round */ \
QUARTER_ROUND(x, C(0, 0), C(1, 0), C(2, 0), C(3, 0)), \
QUARTER_ROUND(x, C(0, 1), C(1, 1), C(2, 1), C(3, 1)), \
QUARTER_ROUND(x, C(0, 2), C(1, 2), C(2, 2), C(3, 2)), \
QUARTER_ROUND(x, C(0, 3), C(1, 3), C(2, 3), C(3, 3)), \
/* Diagonal Round */ \
QUARTER_ROUND(x, C(0, 0), C(1, 1), C(2, 2), C(3, 3)), \
QUARTER_ROUND(x, C(0, 1), C(1, 2), C(2, 3), C(3, 0)), \
QUARTER_ROUND(x, C(0, 2), C(1, 3), C(2, 0), C(3, 1)), \
QUARTER_ROUND(x, C(0, 3), C(1, 0), C(2, 1), C(3, 2)) \
)
#define TWENTY_ROUNDS(x) ( \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x), \
DOUBLE_ROUND(x) \
)
static void chacha20_block_generic(__le32 *stream, u32 *state)
{
u32 x[CHACHA20_BLOCK_WORDS];
int i;
for (i = 0; i < ARRAY_SIZE(x); ++i)
x[i] = state[i];
TWENTY_ROUNDS(x);
for (i = 0; i < ARRAY_SIZE(x); ++i)
stream[i] = cpu_to_le32(x[i] + state[i]);
++state[12];
}
static void chacha20_generic(u8 *out, const u8 *in, u32 len, const u32 key[8],
const u32 counter[4])
{
__le32 buf[CHACHA20_BLOCK_WORDS];
u32 x[] = {
EXPAND_32_BYTE_K,
key[0], key[1], key[2], key[3],
key[4], key[5], key[6], key[7],
counter[0], counter[1], counter[2], counter[3]
};
if (out != in)
memmove(out, in, len);
while (len >= CHACHA20_BLOCK_SIZE) {
chacha20_block_generic(buf, x);
crypto_xor(out, (u8 *)buf, CHACHA20_BLOCK_SIZE);
len -= CHACHA20_BLOCK_SIZE;
out += CHACHA20_BLOCK_SIZE;
}
if (len) {
chacha20_block_generic(buf, x);
crypto_xor(out, (u8 *)buf, len);
}
}
void chacha20(struct chacha20_ctx *state, u8 *dst, const u8 *src, u32 len,
simd_context_t simd_context)
{
if (!chacha20_arch(dst, src, len, state->key, state->counter,
simd_context))
chacha20_generic(dst, src, len, state->key, state->counter);
state->counter[0] += (len + 63) / 64;
}
EXPORT_SYMBOL(chacha20);
static void hchacha20_generic(u8 derived_key[CHACHA20_KEY_SIZE],
const u8 nonce[HCHACHA20_NONCE_SIZE],
const u8 key[HCHACHA20_KEY_SIZE])
{
__le32 *out = (__force __le32 *)derived_key;
u32 x[] = { EXPAND_32_BYTE_K,
get_unaligned_le32(key + 0),
get_unaligned_le32(key + 4),
get_unaligned_le32(key + 8),
get_unaligned_le32(key + 12),
get_unaligned_le32(key + 16),
get_unaligned_le32(key + 20),
get_unaligned_le32(key + 24),
get_unaligned_le32(key + 28),
get_unaligned_le32(nonce + 0),
get_unaligned_le32(nonce + 4),
get_unaligned_le32(nonce + 8),
get_unaligned_le32(nonce + 12)
};
TWENTY_ROUNDS(x);
out[0] = cpu_to_le32(x[0]);
out[1] = cpu_to_le32(x[1]);
out[2] = cpu_to_le32(x[2]);
out[3] = cpu_to_le32(x[3]);
out[4] = cpu_to_le32(x[12]);
out[5] = cpu_to_le32(x[13]);
out[6] = cpu_to_le32(x[14]);
out[7] = cpu_to_le32(x[15]);
}
/* Derived key should be 32-bit aligned */
void hchacha20(u8 derived_key[CHACHA20_KEY_SIZE],
const u8 nonce[HCHACHA20_NONCE_SIZE],
const u8 key[HCHACHA20_KEY_SIZE], simd_context_t simd_context)
{
if (!hchacha20_arch(derived_key, nonce, key, simd_context))
hchacha20_generic(derived_key, nonce, key);
}
/* Deliberately not EXPORT_SYMBOL'd, since there are few reasons why somebody
* should be using this directly, rather than via xchacha20. Revisit only in
* the unlikely event that somebody has a good reason to export this.
*/
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