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// Copyright 2012, Jeramey Crawford <jeramey@antihe.ro>
// Copyright 2013, Jonas mg
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file.
package common
import (
"crypto/rand"
"errors"
"strconv"
)
var (
ErrSaltPrefix = errors.New("invalid magic prefix")
ErrSaltFormat = errors.New("invalid salt format")
ErrSaltRounds = errors.New("invalid rounds")
)
// Salt represents a salt.
type Salt struct {
MagicPrefix []byte
SaltLenMin int
SaltLenMax int
RoundsMin int
RoundsMax int
RoundsDefault int
}
// Generate generates a random salt of a given length.
//
// The length is set thus:
//
// length > SaltLenMax: length = SaltLenMax
// length < SaltLenMin: length = SaltLenMin
func (s *Salt) Generate(length int) []byte {
if length > s.SaltLenMax {
length = s.SaltLenMax
} else if length < s.SaltLenMin {
length = s.SaltLenMin
}
saltLen := (length * 6 / 8)
if (length*6)%8 != 0 {
saltLen++
}
salt := make([]byte, saltLen)
rand.Read(salt)
out := make([]byte, len(s.MagicPrefix)+length)
copy(out, s.MagicPrefix)
copy(out[len(s.MagicPrefix):], Base64_24Bit(salt))
return out
}
// GenerateWRounds creates a random salt with the random bytes being of the
// length provided, and the rounds parameter set as specified.
//
// The parameters are set thus:
//
// length > SaltLenMax: length = SaltLenMax
// length < SaltLenMin: length = SaltLenMin
//
// rounds < 0: rounds = RoundsDefault
// rounds < RoundsMin: rounds = RoundsMin
// rounds > RoundsMax: rounds = RoundsMax
//
// If rounds is equal to RoundsDefault, then the "rounds=" part of the salt is
// removed.
func (s *Salt) GenerateWRounds(length, rounds int) []byte {
if length > s.SaltLenMax {
length = s.SaltLenMax
} else if length < s.SaltLenMin {
length = s.SaltLenMin
}
if rounds < 0 {
rounds = s.RoundsDefault
} else if rounds < s.RoundsMin {
rounds = s.RoundsMin
} else if rounds > s.RoundsMax {
rounds = s.RoundsMax
}
saltLen := (length * 6 / 8)
if (length*6)%8 != 0 {
saltLen++
}
salt := make([]byte, saltLen)
rand.Read(salt)
roundsText := ""
if rounds != s.RoundsDefault {
roundsText = "rounds=" + strconv.Itoa(rounds) + "$"
}
out := make([]byte, len(s.MagicPrefix)+len(roundsText)+length)
copy(out, s.MagicPrefix)
copy(out[len(s.MagicPrefix):], []byte(roundsText))
copy(out[len(s.MagicPrefix)+len(roundsText):], Base64_24Bit(salt))
return out
}
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