balloon.go

   1 /*
   2 balloon -- Balloon password hashing function
   3 Copyright (C) 2016-2019 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 the Free Software Foundation, version 3 of the License.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU Lesser General Public License for more details.
  13
  14 You should have received a copy of the GNU Lesser General Public
  15 License along with this program.  If not, see
  16 <http://www.gnu.org/licenses/>.
  17 */
  18
  19 // Balloon password hashing.
  20 //
  21 // Look https://crypto.stanford.edu/balloon/ for more description.
  22 package balloon
  23
  24 import (
  25         "encoding/binary"
  26         "hash"
  27         "math/big"
  28 )
  29
  30 const (
  31         delta = 3
  32 )
  33
  34 // This function takes hash, password, salt, space cost (buffer size,
  35 // number of hash-output sized blocks), time cost (number of rounds) and
  36 // performs the following:
  37 //
  38 //    # Expand input into buffer.
  39 //    buf[0] = hash(cnt++ || passwd || salt)
  40 //    for m from 1 to sCost-1:
  41 //        buf[m] = hash(cnt++ || buf[m-1])
  42 //    # Mix buffer contents.
  43 //    for t from 0 to tCost-1:
  44 //        for m from 0 to sCost-1:
  45 //            # Hash last and current blocks.
  46 //            prev = buf[(m-1) mod sCost]
  47 //            buf[m] = hash(cnt++ || prev || buf[m])
  48 //            # Hash in pseudorandomly chosen blocks.
  49 //            for i from 0 to delta-1:
  50 //                other = to_int(hash(cnt++ || salt || t || m || i)) mod sCost
  51 //                buf[m] = hash(cnt++ || buf[m] || buf[other])
  52 //    # Extract output from buffer.
  53 //    return buf[sCost-1]
  54 func B(h hash.Hash, passwd, salt []byte, sCost, tCost uint64) []byte {
  55         var cnt uint64
  56         intBuf := make([]byte, 8)
  57         hSize := uint64(h.Size())
  58         buf := make([]byte, 0, sCost*hSize)
  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 = h.Sum(buf)
  66         var m uint64
  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)*hSize : m*hSize])
  73                 buf = h.Sum(buf)
  74         }
  75         // Mix buffer contents
  76         var prev []byte
  77         var i uint64
  78         var neigh uint64
  79         bi := big.NewInt(0)
  80         bs := big.NewInt(int64(sCost))
  81         biBuf := make([]byte, 0, h.Size())
  82         for t := uint64(0); t < tCost; t++ {
  83                 for m = 0; m < sCost; m++ {
  84                         // Hash last and current blocks
  85                         if m == 0 {
  86                                 prev = buf[(sCost-1)*hSize:]
  87                         } else {
  88                                 prev = buf[(m-1)*hSize : m*hSize]
  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*hSize : (m+1)*hSize])
  96                         buf = h.Sum(buf[:m*hSize])
  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, t)
 106                                 h.Write(intBuf)
 107                                 binary.BigEndian.PutUint64(intBuf, m)
 108                                 h.Write(intBuf)
 109                                 binary.BigEndian.PutUint64(intBuf, i)
 110                                 h.Write(intBuf)
 111                                 biBuf = h.Sum(biBuf[:0])
 112                                 bi.SetBytes(biBuf)
 113                                 bi.Mod(bi, bs)
 114                                 binary.BigEndian.PutUint64(intBuf, cnt)
 115                                 cnt++
 116                                 h.Reset()
 117                                 h.Write(intBuf)
 118                                 h.Write(buf[m*hSize : (m+1)*hSize])
 119                                 neigh = bi.Uint64()
 120                                 h.Write(buf[neigh*hSize : (neigh+1)*hSize])
 121                                 buf = h.Sum(buf[:m*hSize])
 122                         }
 123                 }
 124         }
 125         // Extract output from buffer
 126         return buf[(sCost-1)*hSize:]
 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, len(salt)+8)
 144                         copy(saltBuf, salt)
 145                         binary.BigEndian.PutUint64(saltBuf[len(salt):], uint64(i))
 146                         results <- B(hasher(), passwd, saltBuf, uint64(sCost), uint64(tCost))
 147                 }(i)
 148         }
 149         h := hasher()
 150         h.Write(passwd)
 151         h.Write(salt)
 152         result := make([]byte, h.Size())
 153         for i = 0; i < jobs; i++ {
 154                 for n, e := range <-results {
 155                         result[n] ^= e
 156                 }
 157         }
 158         close(results)
 159         h.Write(result)
 160         return h.Sum(result[:0])
 161 }