fs/bcachefs/siphash.c

   1 // SPDX-License-Identifier: BSD-3-Clause
   2 /*      $OpenBSD: siphash.c,v 1.3 2015/02/20 11:51:03 tedu Exp $ */
   3
   4 /*-
   5  * Copyright (c) 2013 Andre Oppermann <andre@FreeBSD.org>
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. The name of the author may not be used to endorse or promote
  17  *    products derived from this software without specific prior written
  18  *    permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 /*
  34  * SipHash is a family of PRFs SipHash-c-d where the integer parameters c and d
  35  * are the number of compression rounds and the number of finalization rounds.
  36  * A compression round is identical to a finalization round and this round
  37  * function is called SipRound.  Given a 128-bit key k and a (possibly empty)
  38  * byte string m, SipHash-c-d returns a 64-bit value SipHash-c-d(k; m).
  39  *
  40  * Implemented from the paper "SipHash: a fast short-input PRF", 2012.09.18,
  41  * by Jean-Philippe Aumasson and Daniel J. Bernstein,
  42  * Permanent Document ID b9a943a805fbfc6fde808af9fc0ecdfa
  43  * https://131002.net/siphash/siphash.pdf
  44  * https://131002.net/siphash/
  45  */
  46
  47 #include <asm/byteorder.h>
  48 #include <linux/unaligned.h>
  49 #include <linux/bitops.h>
  50 #include <linux/string.h>
  51
  52 #include "siphash.h"
  53
  54 static void SipHash_Rounds(SIPHASH_CTX *ctx, int rounds)
  55 {
  56         while (rounds--) {
  57                 ctx->v[0] += ctx->v[1];
  58                 ctx->v[2] += ctx->v[3];
  59                 ctx->v[1] = rol64(ctx->v[1], 13);
  60                 ctx->v[3] = rol64(ctx->v[3], 16);
  61
  62                 ctx->v[1] ^= ctx->v[0];
  63                 ctx->v[3] ^= ctx->v[2];
  64                 ctx->v[0] = rol64(ctx->v[0], 32);
  65
  66                 ctx->v[2] += ctx->v[1];
  67                 ctx->v[0] += ctx->v[3];
  68                 ctx->v[1] = rol64(ctx->v[1], 17);
  69                 ctx->v[3] = rol64(ctx->v[3], 21);
  70
  71                 ctx->v[1] ^= ctx->v[2];
  72                 ctx->v[3] ^= ctx->v[0];
  73                 ctx->v[2] = rol64(ctx->v[2], 32);
  74         }
  75 }
  76
  77 static void SipHash_CRounds(SIPHASH_CTX *ctx, const void *ptr, int rounds)
  78 {
  79         u64 m = get_unaligned_le64(ptr);
  80
  81         ctx->v[3] ^= m;
  82         SipHash_Rounds(ctx, rounds);
  83         ctx->v[0] ^= m;
  84 }
  85
  86 void SipHash_Init(SIPHASH_CTX *ctx, const SIPHASH_KEY *key)
  87 {
  88         u64 k0, k1;
  89
  90         k0 = le64_to_cpu(key->k0);
  91         k1 = le64_to_cpu(key->k1);
  92
  93         ctx->v[0] = 0x736f6d6570736575ULL ^ k0;
  94         ctx->v[1] = 0x646f72616e646f6dULL ^ k1;
  95         ctx->v[2] = 0x6c7967656e657261ULL ^ k0;
  96         ctx->v[3] = 0x7465646279746573ULL ^ k1;
  97
  98         memset(ctx->buf, 0, sizeof(ctx->buf));
  99         ctx->bytes = 0;
 100 }
 101
 102 void SipHash_Update(SIPHASH_CTX *ctx, int rc, int rf,
 103                     const void *src, size_t len)
 104 {
 105         const u8 *ptr = src;
 106         size_t left, used;
 107
 108         if (len == 0)
 109                 return;
 110
 111         used = ctx->bytes % sizeof(ctx->buf);
 112         ctx->bytes += len;
 113
 114         if (used > 0) {
 115                 left = sizeof(ctx->buf) - used;
 116
 117                 if (len >= left) {
 118                         memcpy(&ctx->buf[used], ptr, left);
 119                         SipHash_CRounds(ctx, ctx->buf, rc);
 120                         len -= left;
 121                         ptr += left;
 122                 } else {
 123                         memcpy(&ctx->buf[used], ptr, len);
 124                         return;
 125                 }
 126         }
 127
 128         while (len >= sizeof(ctx->buf)) {
 129                 SipHash_CRounds(ctx, ptr, rc);
 130                 len -= sizeof(ctx->buf);
 131                 ptr += sizeof(ctx->buf);
 132         }
 133
 134         if (len > 0)
 135                 memcpy(&ctx->buf[used], ptr, len);
 136 }
 137
 138 void SipHash_Final(void *dst, SIPHASH_CTX *ctx, int rc, int rf)
 139 {
 140         u64 r;
 141
 142         r = SipHash_End(ctx, rc, rf);
 143
 144         *((__le64 *) dst) = cpu_to_le64(r);
 145 }
 146
 147 u64 SipHash_End(SIPHASH_CTX *ctx, int rc, int rf)
 148 {
 149         u64 r;
 150         size_t left, used;
 151
 152         used = ctx->bytes % sizeof(ctx->buf);
 153         left = sizeof(ctx->buf) - used;
 154         memset(&ctx->buf[used], 0, left - 1);
 155         ctx->buf[7] = ctx->bytes;
 156
 157         SipHash_CRounds(ctx, ctx->buf, rc);
 158         ctx->v[2] ^= 0xff;
 159         SipHash_Rounds(ctx, rf);
 160
 161         r = (ctx->v[0] ^ ctx->v[1]) ^ (ctx->v[2] ^ ctx->v[3]);
 162         memset(ctx, 0, sizeof(*ctx));
 163         return r;
 164 }
 165
 166 u64 SipHash(const SIPHASH_KEY *key, int rc, int rf, const void *src, size_t len)
 167 {
 168         SIPHASH_CTX ctx;
 169
 170         SipHash_Init(&ctx, key);
 171         SipHash_Update(&ctx, rc, rf, src, len);
 172         return SipHash_End(&ctx, rc, rf);
 173 }