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package security
import (
"crypto/pbkdf2"
"crypto/rand"
"crypto/sha256"
"crypto/subtle"
"errors"
"unicode"
)
const (
PasswordSaltBytes = 16
PasswordHashBytes = 32
PasswordIterations = 600_000
)
var ErrWeakPassword = errors.New("password must be 12-128 characters and contain letters and numbers")
func ValidatePassword(password string) error {
runes := []rune(password)
if len(runes) < 12 || len(runes) > 128 {
return ErrWeakPassword
}
var letter, number bool
for _, value := range runes {
letter = letter || unicode.IsLetter(value)
number = number || unicode.IsNumber(value)
}
if !letter || !number {
return ErrWeakPassword
}
return nil
}
func HashPassword(password string) (hash, salt []byte, iterations int, err error) {
if err := ValidatePassword(password); err != nil {
return nil, nil, 0, err
}
salt = make([]byte, PasswordSaltBytes)
if _, err := rand.Read(salt); err != nil {
return nil, nil, 0, err
}
hash, err = pbkdf2.Key(sha256.New, password, salt, PasswordIterations, PasswordHashBytes)
if err != nil {
return nil, nil, 0, err
}
return hash, salt, PasswordIterations, nil
}
func VerifyPassword(password string, expectedHash, salt []byte, iterations int) bool {
if len(expectedHash) != PasswordHashBytes || len(salt) != PasswordSaltBytes || iterations < 100_000 || iterations > 10_000_000 || len([]rune(password)) > 128 {
return false
}
actual, err := pbkdf2.Key(sha256.New, password, salt, iterations, len(expectedHash))
if err != nil {
return false
}
return subtle.ConstantTimeCompare(actual, expectedHash) == 1
}
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