XTLS/Xray-core · error

rand lengthMin or lengthMax cannot be 0

Error message

rand lengthMin or lengthMax cannot be 0

What it means

Thrown by ParseNoise when a rand noise's parsed range has a lower bound of 0. A zero-length random padding packet is useless (it would emit nothing), so after LengthMin/LengthMax are set the builder rejects LengthMin == 0. Note only the minimum is checked here.

Source

Thrown at infra/conf/freedom.go:210

	return config, nil
}

func ParseNoise(noise *Noise) (*freedom.Noise, error) {
	var err error
	NConfig := new(freedom.Noise)
	noise.Packet = strings.TrimSpace(noise.Packet)

	switch noise.Type {
	case "rand":
		min, max, err := ParseRangeString(noise.Packet)
		if err != nil {
			return nil, errors.New("invalid value for rand Length").Base(err)
		}
		NConfig.LengthMin = uint64(min)
		NConfig.LengthMax = uint64(max)
		if NConfig.LengthMin == 0 {
			return nil, errors.New("rand lengthMin or lengthMax cannot be 0")
		}

	case "str":
		// user input string
		NConfig.Packet = []byte(noise.Packet)

	case "hex":
		// user input hex
		NConfig.Packet, err = hex.DecodeString(noise.Packet)
		if err != nil {
			return nil, errors.New("Invalid hex string").Base(err)
		}

	case "base64":
		// user input base64
		NConfig.Packet, err = base64.RawURLEncoding.DecodeString(strings.NewReplacer("+", "-", "/", "_", "=", "").Replace(noise.Packet))
		if err != nil {
			return nil, errors.New("Invalid base64 string").Base(err)

View on GitHub (pinned to 7d214f8b09)

Solutions

1. Start the range at 1 or higher, e.g. "50-100".
2. Use a fixed positive range like "100-100" for deterministic padding size.
3. Validate noise ranges in config tooling before deployment.

Example fix

// before
{"type": "rand", "packet": "0-100"}

// after
{"type": "rand", "packet": "50-100"}

if min, _, err := ParseRangeString(noise.Packet); err == nil && min < 1 {
    return errors.New("rand noise length must be >= 1")
}

When it happens

Trigger: {"type": "rand", "packet": "0-100"} — the range parses fine but min is 0. Also "0-0".

Common situations: 0-based ranges from generators; misunderstanding the range as byte counts where 0 seems harmless.

Related errors

• PacketsFrom can't be 0
• LengthMin can't be 0
• invalid value for rand Length
• Invalid hex string
• Invalid base64 string

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/44fe60655e19f702. Report an issue: GitHub.