/* SipHash reference C implementation
 *
 * Copyright (c) 2012-2016 Jean-Philippe Aumasson
 * <jeanphilippe.aumasson@gmail.com>
 * Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>
 *
 * Slightly adapted by rsyslog in regard to build system and code style
 * check.
 *
 * To the extent possible under law, the author(s) have dedicated all copyright
 * and related and neighboring rights to this software to the public domain
 * worldwide. This software is distributed without any warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication along
 * with
 * this software. If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.
 *
 * For details on siphash see https://131002.net/siphash/
 */
#include <assert.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

/* default: SipHash-2-4 */
#define cROUNDS 2
#define dROUNDS 4

#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))

#define U32TO8_LE(p, v)                                                        \
	(p)[0] = (uint8_t)((v));                                                   \
	(p)[1] = (uint8_t)((v) >> 8);                                              \
	(p)[2] = (uint8_t)((v) >> 16);                                             \
	(p)[3] = (uint8_t)((v) >> 24);

#define U64TO8_LE(p, v)                                                        \
	U32TO8_LE((p), (uint32_t)((v)));                                           \
	U32TO8_LE((p) + 4, (uint32_t)((v) >> 32));

#define U8TO64_LE(p)                                                           \
	(((uint64_t)((p)[0])) | ((uint64_t)((p)[1]) << 8) |                        \
	((uint64_t)((p)[2]) << 16) | ((uint64_t)((p)[3]) << 24) |                 \
	((uint64_t)((p)[4]) << 32) | ((uint64_t)((p)[5]) << 40) |                 \
	((uint64_t)((p)[6]) << 48) | ((uint64_t)((p)[7]) << 56))

#define SIPROUND                                                               \
	do {                                                                       \
		v0 += v1;                                                              \
		v1 = ROTL(v1, 13);                                                     \
		v1 ^= v0;                                                              \
		v0 = ROTL(v0, 32);                                                     \
		v2 += v3;                                                              \
		v3 = ROTL(v3, 16);                                                     \
		v3 ^= v2;                                                              \
		v0 += v3;                                                              \
		v3 = ROTL(v3, 21);                                                     \
		v3 ^= v0;                                                              \
		v2 += v1;                                                              \
		v1 = ROTL(v1, 17);                                                     \
		v1 ^= v2;                                                              \
		v2 = ROTL(v2, 32);                                                     \
	} while (0)

#ifdef DEBUG
#define TRACE                                                                  \
	do {                                                                       \
		printf("(%3d) v0 %08x %08x\n", (int)inlen, (uint32_t)(v0 >> 32),       \
		       (uint32_t)v0);                                                  \
		printf("(%3d) v1 %08x %08x\n", (int)inlen, (uint32_t)(v1 >> 32),       \
		       (uint32_t)v1);                                                  \
		printf("(%3d) v2 %08x %08x\n", (int)inlen, (uint32_t)(v2 >> 32),       \
		       (uint32_t)v2);                                                  \
		printf("(%3d) v3 %08x %08x\n", (int)inlen, (uint32_t)(v3 >> 32),       \
		       (uint32_t)v3);                                                  \
	} while (0)
#else
#define TRACE
#endif

extern int rs_siphash(const uint8_t *in, const size_t inlen, const uint8_t *k,
	uint8_t *out, const size_t outlen); /* avoid compiler warning */
#if defined(__clang__)
#pragma GCC diagnostic ignored "-Wunknown-attributes"
#endif
int
#if defined(__clang__)
__attribute__((no_sanitize("unsigned-integer-overflow")))
#endif
rs_siphash(const uint8_t *in, const size_t inlen, const uint8_t *k,
	uint8_t *out, const size_t outlen) {

	uint64_t v0 = 0x736f6d6570736575ULL;
	uint64_t v1 = 0x646f72616e646f6dULL;
	uint64_t v2 = 0x6c7967656e657261ULL;
	uint64_t v3 = 0x7465646279746573ULL;
	uint64_t k0 = U8TO64_LE(k);
	uint64_t k1 = U8TO64_LE(k + 8);
	uint64_t m;
	int i;
	const uint8_t *end = in + inlen - (inlen % sizeof(uint64_t));
	const int left = inlen & 7;
	uint64_t b = ((uint64_t)inlen) << 56;
	assert((outlen == 8) || (outlen == 16));
	v3 ^= k1;
	v2 ^= k0;
	v1 ^= k1;
	v0 ^= k0;

	if (outlen == 16)
	v1 ^= 0xee;

	for (; in != end; in += 8) {
		m = U8TO64_LE(in);
		v3 ^= m;

		TRACE;
		for (i = 0; i < cROUNDS; ++i)
		    SIPROUND;

		v0 ^= m;
	}

	switch (left) {
	case 7:
		b |= ((uint64_t)in[6]) << 48;
		/*FALLTHROUGH*/
	case 6:
		b |= ((uint64_t)in[5]) << 40;
		/*FALLTHROUGH*/
	case 5:
		b |= ((uint64_t)in[4]) << 32;
		/*FALLTHROUGH*/
	case 4:
		b |= ((uint64_t)in[3]) << 24;
		/*FALLTHROUGH*/
	case 3:
		b |= ((uint64_t)in[2]) << 16;
		/*FALLTHROUGH*/
	case 2:
		b |= ((uint64_t)in[1]) << 8;
		/*FALLTHROUGH*/
	case 1:
		b |= ((uint64_t)in[0]);
		break;
	case 0:
	default:
		break;
	}

	v3 ^= b;

	TRACE;
	for (i = 0; i < cROUNDS; ++i)
		SIPROUND;

	v0 ^= b;

	if (outlen == 16)
		v2 ^= 0xee;
	else
		v2 ^= 0xff;

	TRACE;
	for (i = 0; i < dROUNDS; ++i)
		SIPROUND;

	b = v0 ^ v1 ^ v2 ^ v3;
	U64TO8_LE(out, b);

	if (outlen == 8)
		return 0;

	v1 ^= 0xdd;

	TRACE;
	for (i = 0; i < dROUNDS; ++i)
		SIPROUND;

	b = v0 ^ v1 ^ v2 ^ v3;
	U64TO8_LE(out + 8, b);

	return 0;
}
