crypto: chacha20-generic - add HChaCha20 library function

};

void chacha20_block(u32 *state, u8 *stream);

void hchacha20_block(const u32 *in, u32 *out);

void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv);

int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,

			   unsigned int keysize);

/*

 * ChaCha20 256-bit cipher algorithm, RFC7539

 * The "hash function" used as the core of the ChaCha20 stream cipher (RFC7539)

 *

 * Copyright (C) 2015 Martin Willi

 *

#include <asm/unaligned.h>

#include <crypto/chacha20.h>

void chacha20_block(u32 *state, u8 *stream)

static void chacha20_permute(u32 *x)

{

	u32 x[16];

	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] = rol32(x[12] ^ x[0],  16);

		x[1]  += x[5];    x[13] = rol32(x[13] ^ x[1],  16);

		x[8]  += x[13];   x[7]  = rol32(x[7]  ^ x[8],   7);

		x[9]  += x[14];   x[4]  = rol32(x[4]  ^ x[9],   7);

	}

}

/**

 * chacha20_block - generate one keystream block and increment block counter

 * @state: input state matrix (16 32-bit words)

 * @stream: output keystream block (64 bytes)

 *

 * This is the ChaCha20 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 chacha20_block(u32 *state, u8 *stream)

{

	u32 x[16];

	int i;

	memcpy(x, state, 64);

	chacha20_permute(x);

	for (i = 0; i < ARRAY_SIZE(x); i++)

		put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);

	state[12]++;

}

EXPORT_SYMBOL(chacha20_block);

/**

 * hchacha20_block - abbreviated ChaCha20 core, for XChaCha20

 * @in: input state matrix (16 32-bit words)

 * @out: output (8 32-bit words)

 *

 * HChaCha20 is the ChaCha equivalent of HSalsa20 and is an intermediate step

 * towards XChaCha20 (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf).

 * HChaCha20 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 hchacha20_block(const u32 *in, u32 *out)

{

	u32 x[16];

	memcpy(x, in, 64);

	chacha20_permute(x);

	memcpy(&out[0], &x[0], 16);

	memcpy(&out[4], &x[12], 16);

}

EXPORT_SYMBOL(hchacha20_block);