PWGen/pwgenerator/funcs.go

package pwgenerator

import (
	"crypto/rand"
	"math/big"
	insecureRand "math/rand"
	"sort"
	"strings"
)

// newCryptoShuffler returns a new cryptoShuffler.
func newCryptoShuffler() *cryptoShuffler {
	return new(cryptoShuffler)
}

/*
	GetCharset returns a CharSet from a set of characters.

	chars can be one of []rune, []byte, []string, or string.
*/
func GetCharset(chars interface{}) (charset CharSet, err error) {

	switch t := chars.(type) {
	case []rune:
		charset = CharSet(string(t))
	case []byte:
		charset = CharSet(string(t))
	case []string:
		s := strings.Join(t, "")
		charset = CharSet(s)
	case string:
		charset = CharSet(t)
	default:
		err = ErrBadType
		return
	}

	return
}

// sortDedupe sorts a slice of runes and deduplicates them.
func sortDedupe(charset *CharSet) {

	var vals map[Char]bool = make(map[Char]bool)
	var sorted CharSet
	var idx int

	// This inherently dedupes.
	for _, i := range *charset {
		vals[i] = true
	}

	// This handles sorting.
	sorted = make(CharSet, len(vals))
	// First we need a slice (again).
	for k := range vals {
		sorted[idx] = k
		idx++
	}
	// And now we can sort...
	sort.Sort(&sorted)

	// And replace the original charset with the sorted, deduplicated one.
	*charset = sorted

	return
}

/*
	saferRandInt uses crypto/rand instead of math/rand to get a random number.

	While this is cryptographically safer, I guarantee it's a much bigger pain to do.
*/
func saferRandInt(max int) (randInt int, err error) {

	// Avoid a panic on max being 0 per rand.Int.
	if max == 0 {
		max = 1
	}

	var max64 int64 = int64(max)
	var cryptoInt *big.Int = big.NewInt(max64)
	var randInt64 int64

	if cryptoInt, err = rand.Int(rand.Reader, cryptoInt); err != nil {
		return
	}

	randInt64 = cryptoInt.Int64()

	randInt = int(randInt64)

	return
}

// passwordShuffle shuffles a password's characters ordering so we don't have the condition satisfiers in the beginning.
func passwordShuffle(passwd *string) {

	var r *insecureRand.Rand = insecureRand.New(newCryptoShuffler())

	r.Shuffle(
		len(*passwd),
		func(i, j int) {
			var chars []rune = []rune(*passwd)

			chars[i], chars[j] = chars[j], chars[i]

			*passwd = string(chars)
		},
	)

	return
}