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/*
* ChaCha20 256-bit cipher algorithm, RFC7539
*
* Copyright (C) 2015 Martin Willi
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <crypto/algapi.h>
#include <linux/crypto.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <crypto/chacha20.h>
static inline u32 rotl32(u32 v, u8 n)
{
return (v << n) | (v >> (sizeof(v) * 8 - n));
}
static inline u32 le32_to_cpuvp(const void *p)
{
return le32_to_cpup(p);
}
static void chacha20_block(u32 *state, void *stream)
{
u32 x[16], *out = stream;
int i;
for (i = 0; i < ARRAY_SIZE(x); i++)
x[i] = state[i];
for (i = 0; i < 20; i += 2) {
x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
}
for (i = 0; i < ARRAY_SIZE(x); i++)
out[i] = cpu_to_le32(x[i] + state[i]);
state[12]++;
}
static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
unsigned int bytes)
{
u8 stream[CHACHA20_BLOCK_SIZE];
if (dst != src)
memcpy(dst, src, bytes);
while (bytes >= CHACHA20_BLOCK_SIZE) {
chacha20_block(state, stream);
crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
bytes -= CHACHA20_BLOCK_SIZE;
dst += CHACHA20_BLOCK_SIZE;
}
if (bytes) {
chacha20_block(state, stream);
crypto_xor(dst, stream, bytes);
}
}
void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
{
static const char constant[16] = "expand 32-byte k";
state[0] = le32_to_cpuvp(constant + 0);
state[1] = le32_to_cpuvp(constant + 4);
state[2] = le32_to_cpuvp(constant + 8);
state[3] = le32_to_cpuvp(constant + 12);
state[4] = ctx->key[0];
state[5] = ctx->key[1];
state[6] = ctx->key[2];
state[7] = ctx->key[3];
state[8] = ctx->key[4];
state[9] = ctx->key[5];
state[10] = ctx->key[6];
state[11] = ctx->key[7];
state[12] = le32_to_cpuvp(iv + 0);
state[13] = le32_to_cpuvp(iv + 4);
state[14] = le32_to_cpuvp(iv + 8);
state[15] = le32_to_cpuvp(iv + 12);
}
EXPORT_SYMBOL_GPL(crypto_chacha20_init);
int crypto_chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
unsigned int keysize)
{
struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
int i;
if (keysize != CHACHA20_KEY_SIZE)
return -EINVAL;
for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
return 0;
}
EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
int crypto_chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
struct scatterlist *src, unsigned
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