/*-
 * Copyright (c) 2013 Andre Oppermann <andre@FreeBSD.org>
 * 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.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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.
 */

/*
 * SipHash is a family of PRFs SipHash-c-d where the integer parameters c and d
 * are the number of compression rounds and the number of finalization rounds.
 * A compression round is identical to a finalization round and this round
 * function is called SipRound.  Given a 128-bit key k and a (possibly empty)
 * byte string m, SipHash-c-d returns a 64-bit value SipHash-c-d(k; m).
 *
 * Implemented from the paper "SipHash: a fast short-input PRF", 2012.09.18,
 * by Jean-Philippe Aumasson and Daniel J. Bernstein,
 * Permanent Document ID b9a943a805fbfc6fde808af9fc0ecdfa
 * https://131002.net/siphash/siphash.pdf
 * https://131002.net/siphash/
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/libkern.h>
#include <sys/endian.h>

#include <crypto/siphash/siphash.h>

static void     SipRounds(SIPHASH_CTX *ctx, int final);

void
SipHash_InitX(SIPHASH_CTX *ctx, int rc, int rf)
{

        ctx->v[0] = 0x736f6d6570736575ull;
        ctx->v[1] = 0x646f72616e646f6dull;
        ctx->v[2] = 0x6c7967656e657261ull;
        ctx->v[3] = 0x7465646279746573ull;
        ctx->buf.b64 = 0;
        ctx->bytes = 0;
        ctx->buflen = 0;
        ctx->rounds_compr = rc;
        ctx->rounds_final = rf;
        ctx->initialized = 1;
}

void
SipHash_SetKey(SIPHASH_CTX *ctx, const uint8_t key[static SIPHASH_KEY_LENGTH])
{
        uint64_t k[2];

        KASSERT(ctx->v[0] == 0x736f6d6570736575ull &&
            ctx->initialized == 1,
            ("%s: context %p not properly initialized", __func__, ctx));

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

        ctx->v[0] ^= k[0];
        ctx->v[1] ^= k[1];
        ctx->v[2] ^= k[0];
        ctx->v[3] ^= k[1];

        ctx->initialized = 2;
}

static size_t
SipBuf(SIPHASH_CTX *ctx, const uint8_t **src, size_t len, int final)
{
        size_t x = 0;

        /* handle hashing 0 length buffer - needed for test vectors */
        if (len == 0 && final == 0)
                return (0);

        if (final) {
                KASSERT(len == 0, ("%s: invalid len param", __func__));
                ctx->buf.b8[7] = (uint8_t)ctx->bytes;
        } else {
                KASSERT((len > 0) && src && *src,
                        ("%s: invalid parameters", __func__));
                x = MIN(len, sizeof(ctx->buf.b64) - ctx->buflen);
                bcopy(*src, &ctx->buf.b8[ctx->buflen], x);
                ctx->buflen += x;
                *src += x;
        }

        if (ctx->buflen == 8 || final) {
                ctx->v[3] ^= le64toh(ctx->buf.b64);
                SipRounds(ctx, 0);
                ctx->v[0] ^= le64toh(ctx->buf.b64);
                ctx->buf.b64 = 0;
                ctx->buflen = 0;
        }
        return (x);
}

void
SipHash_Update(SIPHASH_CTX *ctx, const void *src, size_t len)
{
        uint64_t m;
        const uint64_t *p;
        const uint8_t *s;
        size_t rem;

        KASSERT(ctx->initialized == 2,
            ("%s: context %p not properly initialized", __func__, ctx));

        s = src;
        ctx->bytes += len;

        /*
         * Push length smaller than block size into buffer or
         * fill up the buffer if there is already something
         * in it.
         */
        if (ctx->buflen > 0 || len < 8)
                len -= SipBuf(ctx, &s, len, 0);
        if (len == 0)
                return;

        rem = len & 0x7;
        len >>= 3;

        /* Optimze for 64bit aligned/unaligned access. */
        if (((uintptr_t)s & 0x7) == 0) {
                for (p = (const uint64_t *)s; len > 0; len--, p++) {
                        m = le64toh(*p);
                        ctx->v[3] ^= m;
                        SipRounds(ctx, 0);
                        ctx->v[0] ^= m;
                }
                s = (const uint8_t *)p;
        } else {
                for (; len > 0; len--, s += 8) {
                        m = le64dec(s);
                        ctx->v[3] ^= m;
                        SipRounds(ctx, 0);
                        ctx->v[0] ^= m;
                }
        }

        /* Push remainder into buffer. */
        if (rem > 0)
                (void)SipBuf(ctx, &s, rem, 0);
}

void
SipHash_Final(uint8_t dst[static SIPHASH_DIGEST_LENGTH], SIPHASH_CTX *ctx)
{
        uint64_t r;

        KASSERT(ctx->initialized == 2,
            ("%s: context %p not properly initialized", __func__, ctx));

        r = SipHash_End(ctx);
        le64enc(dst, r);
}

uint64_t
SipHash_End(SIPHASH_CTX *ctx)
{
        uint64_t r;

        KASSERT(ctx->initialized == 2,
            ("%s: context %p not properly initialized", __func__, ctx));

        SipBuf(ctx, NULL, 0, 1);
        ctx->v[2] ^= 0xff;
        SipRounds(ctx, 1);
        r = (ctx->v[0] ^ ctx->v[1]) ^ (ctx->v[2] ^ ctx->v[3]);

        bzero(ctx, sizeof(*ctx));
        return (r);
}

uint64_t
SipHashX(SIPHASH_CTX *ctx, int rc, int rf,
    const uint8_t key[static SIPHASH_KEY_LENGTH], const void *src, size_t len)
{

        SipHash_InitX(ctx, rc, rf);
        SipHash_SetKey(ctx, key);
        SipHash_Update(ctx, src, len);

        return (SipHash_End(ctx));
}

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

static void
SipRounds(SIPHASH_CTX *ctx, int final)
{
        int rounds;

        if (!final)
                rounds = ctx->rounds_compr;
        else
                rounds = ctx->rounds_final;

        while (rounds--) {
                ctx->v[0] += ctx->v[1];
                ctx->v[2] += ctx->v[3];
                ctx->v[1] = SIP_ROTL(ctx->v[1], 13);
                ctx->v[3] = SIP_ROTL(ctx->v[3], 16);

                ctx->v[1] ^= ctx->v[0];
                ctx->v[3] ^= ctx->v[2];
                ctx->v[0] = SIP_ROTL(ctx->v[0], 32);

                ctx->v[2] += ctx->v[1];
                ctx->v[0] += ctx->v[3];
                ctx->v[1] = SIP_ROTL(ctx->v[1], 17);
                ctx->v[3] = SIP_ROTL(ctx->v[3], 21);

                ctx->v[1] ^= ctx->v[2];
                ctx->v[3] ^= ctx->v[0];
                ctx->v[2] = SIP_ROTL(ctx->v[2], 32);
        }
}