/*	$NetSBD$	*/

/* SIP Hash */

/*-
 * Copyright (c) 2012 Taylor R. Campbell
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
 * NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Jean-Philippe Aumasson and Daniel J. Bernstein, `SipHash: a fast
 * short-input PRF', Cryptology ePrint Archive Report 2012/351, 2012,
 * presented at the DIAC workshop.
 *
 * http://eprint.iacr.org/2012/351
 */

#include <sys/cdefs.h>

#if defined(_KERNEL) || defined(_STANDALONE)
_KERNEL_RCSID(0, "$NetBSD$");
#else
__RCSID("$NetBSD$");
#ifdef __weak_alias
__weak_alias(siphash,_siphash);
__weak_alias(siphash_2_4,_siphash_2_4);
__weak_alias(siphash_4_8,_siphash_4_8);
#endif
#include "namespace.h"
#endif

#include <sys/types.h>
#include <sys/endian.h>
#include <sys/stdint.h>

#include "siphash.h"

struct state {
	uint64_t v[4];
};

static inline void
rotate64(uint64_t *p, unsigned int n)
{

	*p = ((*p << n) | (*p >> (64 - n)));
}

static inline void
sipround(struct state *s)
{

	s->v[0] += s->v[1]; rotate64(&s->v[1], 13);
	s->v[1] ^= s->v[0]; rotate64(&s->v[0], 32);

	s->v[2] += s->v[3]; rotate64(&s->v[3], 16);
	s->v[3] ^= s->v[2];

	s->v[0] += s->v[3]; rotate64(&s->v[3], 21);
	s->v[3] ^= s->v[0];

	s->v[2] += s->v[1]; rotate64(&s->v[1], 17);
	s->v[1] ^= s->v[2]; rotate64(&s->v[2], 32);
}

static inline void
sipcompress(unsigned int rounds, uint64_t m, struct state *s)
{

	s->v[3] ^= m;
	while (0 < rounds--)
		sipround(s);
	s->v[0] ^= m;
}

static inline uint64_t
sipfinalize(unsigned int rounds, struct state *s)
{

	s->v[2] ^= UINT64_C(0xff);
	while (0 < rounds--)
		sipround(s);

	return (s->v[0] ^ s->v[1] ^ s->v[2] ^ s->v[3]);
}

inline uint64_t
siphash(unsigned int compress_rounds, unsigned int finalize_rounds,
    const uint8_t key[16], const uint8_t *message, size_t length)
{
	uint64_t k[2];
	struct state s;
	size_t words, remainder, i;
	uint8_t buffer[8];

	/* `somepseudorandomlygeneratedbytes' */
	static const uint64_t h[] = {
		UINT64_C(0x736f6d6570736575),
		UINT64_C(0x646f72616e646f6d),
		UINT64_C(0x6c7967656e657261),
		UINT64_C(0x7465646279746573),
	};

	k[0] = le64dec(&key[0]);
	k[1] = le64dec(&key[8]);

	s.v[0] = (k[0] ^ h[0]);
	s.v[1] = (k[1] ^ h[1]);
	s.v[2] = (k[0] ^ h[2]);
	s.v[3] = (k[1] ^ h[3]);

	remainder = (length & 7);
	words = (((length + 1) >> 3) - (remainder != 0));

	while (0 < words--) {
		sipcompress(compress_rounds, le64dec(message), &s);
		message += 8;
	}

	for (i = 0; (i < remainder); i++)
		buffer[i] = message[i];
	for (i = remainder; (i < 7); i++)
		buffer[i] = 0;
	buffer[7] = (length & 0xff);
	sipcompress(compress_rounds, le64dec(buffer), &s);

	return sipfinalize(finalize_rounds, &s);
}

uint64_t
siphash_2_4(const uint8_t key[16], const uint8_t *message, size_t length)
{

	return siphash(2, 4, key, message, length);
}

uint64_t
siphash_4_8(const uint8_t key[16], const uint8_t *message, size_t length)
{

	return siphash(4, 8, key, message, length);
}