owasp-amass/amass · error

invalid key delimiter: %s

Error message

invalid key delimiter: %s

What it means

Transformation.Split expects a key containing exactly one '->' delimiter separating the From and To components; anything else returns this error naming the key. It enforces the 'from->to' transformation key format.

Source

Thrown at config/transform.go:111

			return fmt.Errorf("invalid type for priority in default_transform_values")
		}

	}
	return nil
}

// Split splits the key into 'From' and 'To' components, expecting a "->" delimiter.
// Requires a non-nil Transformation pointer and a valid key format. Example: FQDN->IPaddress.
func (t *Transformation) Split(key string) error {
	if t.From != "" && t.To != "" {
		t.From = strings.ToLower(t.From)
		t.To = strings.ToLower(t.To)
		return nil // Already split
	}
	// Split the key into 'From' and 'To' components, expecting a "->" delimiter.
	parts := strings.Split(key, "->")
	if len(parts) != 2 {
		return fmt.Errorf("invalid key delimiter: %s", key)
	}
	// Assign the 'From' and 'To' values to the Transformation struct.
	t.From = strings.ToLower(parts[0])
	t.To = strings.ToLower(parts[1])
	return nil
}

// Validate checks the validity of a given transformation with respect to OAM &
// previously registered transformations. The function ensures OAM compliance & that there are no conflicts
// between transformations with 'none' (indicating no action) and other valid transformations
// for the same 'From' type.
func (t *Transformation) Validate(c *Config) error {
	if c.fromWithNone == nil {
		c.fromWithNone = make(map[string]bool)
	}
	if c.fromWithValid == nil {
		c.fromWithValid = make(map[string]bool)
	}

View on GitHub (pinned to 79299dce87)

Solutions

1. Format the key as 'from->to' with exactly one '->' delimiter
2. Split chained transformations into separate entries
3. Normalize the key: strings.Count(key, "->") == 1 check before calling Split

Example fix

// before
cfg.Transformations["subdomain>ip"] = &Transformation{}
// after
cfg.Transformations["subdomain->ip"] = &Transformation{}

func validTransformKey(key string) bool {
	parts := strings.Split(key, "->")
	return len(parts) == 2 && parts[0] != "" && parts[1] != ""
}

if err := t.Split(key); err != nil {
	if strings.Contains(err.Error(), "invalid key delimiter") {
		return fmt.Errorf("transformation key %q must use '->' exactly once", key)
	}
	return err
}

When it happens

Trigger: Calling Split (directly or via loadTransformSettings) with keys like 'a>b', 'a', 'a->b->c', 'a - > b', or keys using a different arrow notation.

Common situations: Hand-writing transformation entries in amass config YAML with wrong delimiters, or programmatic key construction that concatenates multiple hops into one key.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• %s is not a valid IP address or range
• %s is not a valid IP
• %s is not a valid IP range
• brute forcing cannot be performed without DNS resolution
• active enumeration cannot be performed without DNS resolutio

AI-assisted analysis of owasp-amass/amass@79299dce87 (2026-09-06). Data as JSON: /api/errors/1dcb5a9cce134dd7. Report an issue: GitHub.