Function Compare

internal/kdf/kdf.go:88–130

Compare compares the password with the given PHC encoded hash, returns true if they match. The time taken is a function of the length of the slices and is independent of the contents.

(password, phc []byte)

// if they match. The time taken is a function of the length of the slices and
// is independent of the contents.
func Compare(password, phc []byte) (bool, error) {
	id, version, params, salt, hash, err := phcDecode(string(phc))
	if err != nil {
		return false, errors.Wrap(err, "error decoding hash")
	}

	var hashedPass []byte
	switch id {
	case bcryptHash:
		return (bcrypt.CompareHashAndPassword(hash, password) == nil), nil
	case scryptHash:
		p, err := newScryptParams(params)
		if err != nil {
			return false, err
		}
		hashedPass, err = scrypt.Key(password, salt, p.N, p.r, p.p, len(hash))
		if err != nil {
			return false, errors.Wrap(err, "error deriving input")
		}
	case argon2iHash:
		p, err := newArgon2Params(params)
		if err != nil {
			return false, err
		}
		if version != 0 && version != argon2.Version {
			return false, errors.Errorf("unsupported argon2 version '%d'", version)
		}
		hashedPass = argon2.Key(password, salt, p.t, p.m, p.p, cast.Uint32(len(hash)))
	case argon2idHash:
		p, err := newArgon2Params(params)
		if err != nil {
			return false, err
		}
		if version != 0 && version != argon2.Version {
			return false, errors.Errorf("unsupported argon2 version '%d'", version)
		}
		hashedPass = argon2.IDKey(password, salt, p.t, p.m, p.p, cast.Uint32(len(hash)))
	default:
		return false, errors.Errorf("invalid or unsupported hash method with id '%s'", id)
	}

	return (subtle.ConstantTimeCompare(hash, hashedPass) == 1), nil
}

// CompareString  compares the given password with the given PHC encoded hash,
// returns true if they match. The time taken is a function of the length of