balloon.go

   1 /*
   2 balloon -- Balloon password hashing function
   3 Copyright (C) 2016-2018 Sergey Matveev <stargrave@stargrave.org>
   4
   5 This program is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU Lesser General Public License as
   7 published by the Free Software Foundation, either version 3 of the
   8 License, or (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU Lesser General Public License for more details.
  14
  15 You should have received a copy of the GNU Lesser General Public
  16 License along with this program.  If not, see
  17 <http://www.gnu.org/licenses/>.
  18 */
  19
  20 // Balloon password hashing.
  21 //
  22 // Look https://crypto.stanford.edu/balloon/ for more description.
  23 package balloon
  24
  25 import (
  26         "encoding/binary"
  27         "hash"
  28         "math/big"
  29 )
  30
  31 const (
  32         delta = 3
  33 )
  34
  35 // This function takes hash, password, salt, space cost (buffer size,
  36 // number of hash-output sized blocks), time cost (number of rounds) and
  37 // performs the following:
  38 //
  39 //    # Expand input into buffer.
  40 //    buf[0] = hash(cnt++ || passwd || salt)
  41 //    for m from 1 to sCost-1:
  42 //        buf[m] = hash(cnt++ || buf[m-1])
  43 //    # Mix buffer contents.
  44 //    for t from 0 to tCost-1:
  45 //        for m from 0 to sCost-1:
  46 //            # Hash last and current blocks.
  47 //            prev = buf[(m-1) mod sCost]
  48 //            buf[m] = hash(cnt++ || prev || buf[m])
  49 //            # Hash in pseudorandomly chosen blocks.
  50 //            for i from 0 to delta-1:
  51 //                other = to_int(hash(cnt++ || salt || t || m || i)) mod sCost
  52 //                buf[m] = hash(cnt++ || buf[m] || buf[other])
  53 //    # Extract output from buffer.
  54 //    return buf[sCost-1]
  55 func B(h hash.Hash, passwd, salt []byte, sCost, tCost int) []byte {
  56         var cnt uint64
  57         intBuf := make([]byte, 8)
  58         buf := make([][]byte, sCost)
  59         // Expand input into buffer
  60         binary.BigEndian.PutUint64(intBuf, cnt)
  61         cnt++
  62         h.Write(intBuf)
  63         h.Write(passwd)
  64         h.Write(salt)
  65         buf[0] = h.Sum(nil)
  66         var m int
  67         for m = 1; m < sCost; m++ {
  68                 binary.BigEndian.PutUint64(intBuf, cnt)
  69                 cnt++
  70                 h.Reset()
  71                 h.Write(intBuf)
  72                 h.Write(buf[m-1])
  73                 buf[m] = h.Sum(nil)
  74         }
  75         // Mix buffer contents
  76         var prev []byte
  77         var i int
  78         bi := big.NewInt(0)
  79         bs := big.NewInt(int64(sCost))
  80         biBuf := make([]byte, 0, h.Size())
  81         var other int
  82         for t := 0; t < tCost; t++ {
  83                 for m = 0; m < sCost; m++ {
  84                         // Hash last and current blocks
  85                         if m == 0 {
  86                                 prev = buf[len(buf)-1]
  87                         } else {
  88                                 prev = buf[m-1]
  89                         }
  90                         binary.BigEndian.PutUint64(intBuf, cnt)
  91                         cnt++
  92                         h.Reset()
  93                         h.Write(intBuf)
  94                         h.Write(prev)
  95                         h.Write(buf[m])
  96                         buf[m] = h.Sum(buf[m][:0])
  97
  98                         // Hash in pseudorandomly chosen blocks
  99                         for i = 0; i < delta; i++ {
 100                                 binary.BigEndian.PutUint64(intBuf, cnt)
 101                                 cnt++
 102                                 h.Reset()
 103                                 h.Write(intBuf)
 104                                 h.Write(salt)
 105                                 binary.BigEndian.PutUint64(intBuf, uint64(t))
 106                                 h.Write(intBuf)
 107                                 binary.BigEndian.PutUint64(intBuf, uint64(m))
 108                                 h.Write(intBuf)
 109                                 binary.BigEndian.PutUint64(intBuf, uint64(i))
 110                                 h.Write(intBuf)
 111                                 biBuf = h.Sum(biBuf[:0])
 112                                 bi.SetBytes(biBuf)
 113                                 bi.Mod(bi, bs)
 114                                 other = int(bi.Uint64())
 115                                 binary.BigEndian.PutUint64(intBuf, cnt)
 116                                 cnt++
 117                                 h.Reset()
 118                                 h.Write(intBuf)
 119                                 h.Write(buf[m])
 120                                 h.Write(buf[other])
 121                                 buf[m] = h.Sum(buf[m][:0])
 122                         }
 123                 }
 124         }
 125         // Extract output from buffer
 126         return buf[sCost-1]
 127 }
 128
 129 // This function adds additional functionality over pure B(): ability to
 130 // run several hashers (jobs) simultaneously and second-preimage resistant
 131 // password double hashing.
 132 //
 133 //     H(p, s, jobs) = hash(p || s || (
 134 //         B(p, s || "1") XOR
 135 //         B(p, s || "2") XOR
 136 //         B(p, s || jobs)
 137 //     ))
 138 func H(hasher func() hash.Hash, passwd, salt []byte, sCost, tCost int, jobs int) []byte {
 139         var i int
 140         results := make(chan []byte)
 141         for ; i < jobs; i++ {
 142                 go func(i int) {
 143                         saltBuf := make([]byte, 8)
 144                         binary.BigEndian.PutUint64(saltBuf, uint64(i))
 145                         results <- B(hasher(), passwd, append(salt, saltBuf...), sCost, tCost)
 146                 }(i)
 147         }
 148         h := hasher()
 149         h.Write(passwd)
 150         h.Write(salt)
 151         result := make([]byte, h.Size())
 152         for i = 0; i < jobs; i++ {
 153                 for n, e := range <-results {
 154                         result[n] ^= e
 155                 }
 156         }
 157         close(results)
 158         h.Write(result)
 159         return h.Sum(result[:0])
 160 }