115 строки
3.7 KiB
C
115 строки
3.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* The "hash function" used as the core of the ChaCha stream cipher (RFC7539)
|
|
*
|
|
* Copyright (C) 2015 Martin Willi
|
|
*/
|
|
|
|
#include <linux/bug.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/export.h>
|
|
#include <linux/bitops.h>
|
|
#include <linux/string.h>
|
|
#include <asm/unaligned.h>
|
|
#include <crypto/chacha.h>
|
|
|
|
static void chacha_permute(u32 *x, int nrounds)
|
|
{
|
|
int i;
|
|
|
|
/* whitelist the allowed round counts */
|
|
WARN_ON_ONCE(nrounds != 20 && nrounds != 12);
|
|
|
|
for (i = 0; i < nrounds; i += 2) {
|
|
x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
|
|
x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
|
|
x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16);
|
|
x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16);
|
|
|
|
x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12);
|
|
x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12);
|
|
x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12);
|
|
x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12);
|
|
|
|
x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8);
|
|
x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8);
|
|
x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8);
|
|
x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8);
|
|
|
|
x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7);
|
|
x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7);
|
|
x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7);
|
|
x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7);
|
|
|
|
x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16);
|
|
x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16);
|
|
x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16);
|
|
x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16);
|
|
|
|
x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12);
|
|
x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12);
|
|
x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12);
|
|
x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12);
|
|
|
|
x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8);
|
|
x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8);
|
|
x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8);
|
|
x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8);
|
|
|
|
x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7);
|
|
x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7);
|
|
x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
|
|
x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* chacha_block - generate one keystream block and increment block counter
|
|
* @state: input state matrix (16 32-bit words)
|
|
* @stream: output keystream block (64 bytes)
|
|
* @nrounds: number of rounds (20 or 12; 20 is recommended)
|
|
*
|
|
* This is the ChaCha core, a function from 64-byte strings to 64-byte strings.
|
|
* The caller has already converted the endianness of the input. This function
|
|
* also handles incrementing the block counter in the input matrix.
|
|
*/
|
|
void chacha_block_generic(u32 *state, u8 *stream, int nrounds)
|
|
{
|
|
u32 x[16];
|
|
int i;
|
|
|
|
memcpy(x, state, 64);
|
|
|
|
chacha_permute(x, nrounds);
|
|
|
|
for (i = 0; i < ARRAY_SIZE(x); i++)
|
|
put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
|
|
|
|
state[12]++;
|
|
}
|
|
EXPORT_SYMBOL(chacha_block_generic);
|
|
|
|
/**
|
|
* hchacha_block_generic - abbreviated ChaCha core, for XChaCha
|
|
* @state: input state matrix (16 32-bit words)
|
|
* @out: output (8 32-bit words)
|
|
* @nrounds: number of rounds (20 or 12; 20 is recommended)
|
|
*
|
|
* HChaCha is the ChaCha equivalent of HSalsa and is an intermediate step
|
|
* towards XChaCha (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf). HChaCha
|
|
* skips the final addition of the initial state, and outputs only certain words
|
|
* of the state. It should not be used for streaming directly.
|
|
*/
|
|
void hchacha_block_generic(const u32 *state, u32 *stream, int nrounds)
|
|
{
|
|
u32 x[16];
|
|
|
|
memcpy(x, state, 64);
|
|
|
|
chacha_permute(x, nrounds);
|
|
|
|
memcpy(&stream[0], &x[0], 16);
|
|
memcpy(&stream[4], &x[12], 16);
|
|
}
|
|
EXPORT_SYMBOL(hchacha_block_generic);
|