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package main
import (
"bytes"
"crypto/rand"
"encoding/base64"
"fmt"
"strings"
"golang.org/x/crypto/scrypt"
)
type (
pwHash struct {
salt []byte
hash []byte
}
)
// Create a new password hash.
func newHash(pw string) (*pwHash, error) {
hash := pwHash{}
if err := hash.genSalt(); err != nil {
return nil, err
}
h, err := hash.Hash(pw)
if err != nil {
return nil, err
}
hash.hash = h
return &hash, nil
}
// generate a hash for the given salt and password
func (p *pwHash) Hash(pw string) ([]byte, error) {
if len(p.salt) == 0 {
return []byte{}, fmt.Errorf("salt not initialized")
}
// constants taken from https://godoc.org/golang.org/x/crypto/scrypt
hash, err := scrypt.Key([]byte(pw), p.salt, 32768, 8, 1, 32)
if err != nil {
return []byte{}, fmt.Errorf("could not compute hash: %s", err)
}
return hash, nil
}
// genSalt generates 8 bytes of salt.
func (p *pwHash) genSalt() error {
salt := make([]byte, 8)
_, err := rand.Read(salt)
p.salt = salt
return err
}
// compare a hash to a password and return true, when it matches.
func (p *pwHash) compare(pw string) (bool, error) {
hash, err := p.Hash(pw)
if err != nil {
return false, fmt.Errorf("could not check password")
}
if bytes.Compare(p.hash, hash) == 0 {
return true, nil
}
return false, nil
}
// Encode a hash and salt to a string.
func (p *pwHash) String() string {
return fmt.Sprintf(
"1$%s$%s",
base64.StdEncoding.EncodeToString(p.salt),
base64.StdEncoding.EncodeToString(p.hash),
)
}
// Parse a hash from a file or anywhere.
func (p *pwHash) Parse(raw string) error {
if len(raw) == 0 {
return fmt.Errorf("no hash found")
}
parts := strings.Split(raw, "$")
if len(parts) != 3 {
return fmt.Errorf("format error")
}
if parts[0] != "1" {
return fmt.Errorf("unknown hash version")
}
salt, err := base64.StdEncoding.DecodeString(parts[1])
if err != nil {
return fmt.Errorf("could not parse salt: %s", err)
}
hash, err := base64.StdEncoding.DecodeString(parts[2])
if err != nil {
return fmt.Errorf("could not parse salt: %s", err)
}
p.salt = salt
p.hash = hash
return nil
}
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