owasp-amass/amass · error

no valid resolvers were found

Error message

no valid resolvers were found

What it means

After parsing and type-asserting resolver entries to strings, loadResolverSettings deduplicates the list and requires at least one valid resolver. If the list is empty after validation, this error is returned because enumeration cannot proceed without a resolver.

Source

Thrown at config/resolvers.go:210

		absPath, err := c.AbsPathFromConfigDir(rStr)
		if err != nil {
			return fmt.Errorf("failed to get absolute path for resolver file: %w", err)
		}

		fileResolvers, err := c.loadResolversFromFile(absPath)
		if err != nil {
			return fmt.Errorf("failed to load resolvers from file: %w", err)
		}

		resolversList = append(resolversList, fileResolvers...)

	}

	// Deduplicate the list of resolvers and assign to c.Resolvers.
	resolverIPs := stringset.Deduplicate(resolversList)

	if len(resolverIPs) == 0 {
		return errors.New("no valid resolvers were found")
	}

	c.Resolvers = resolverIPs

	return nil
}

func (c *Config) loadResolversFromFile(path string) ([]string, error) {
	absPath, err := filepath.Abs(path)
	if err != nil {
		return nil, fmt.Errorf("failed to get absolute path: %v", err)
	}

	data, err := os.ReadFile(absPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open resolvers file: %w", err)
	}

View on GitHub (pinned to 79299dce87)

Solutions

1. Add at least one valid resolver IP (e.g. 8.8.8.8) to the list.
2. Remove empty or placeholder entries that fail validation.
3. Verify entries parse as valid IPs/addresses.
4. Confirm the right config file/environment is loaded.

Example fix

# before
resolvers: []
# after
resolvers:
  - 8.8.8.8
  - 1.1.1.1

if len(resolvers) == 0 || allEmpty(resolvers) {
    return errors.New("at least one non-empty resolver is required")
}

if err := loadResolverSettings(cfg); err != nil {
    if strings.Contains(err.Error(), "no valid resolvers") {
        // fall back to well-known public resolvers (8.8.8.8, 1.1.1.1)
    }
    return err
}

When it happens

Trigger: Calling loadResolverSettings where resolversList resolves to zero entries after parsing/validation — e.g. a resolvers list with only empty strings or entries rejected by validation — so len(resolverIPs) == 0.

Common situations: An empty resolvers list in the config (resolvers: [] or only blank entries), environment-specific configs stripped of resolver addresses, or validation dropping malformed addresses leaving none.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• brute forcing cannot be performed without DNS resolution
• active enumeration cannot be performed without DNS resolutio
• no resolver keys were found in the resolvers section
• resolvers section is not a list
• alterations wordlist_file item is not a string

AI-assisted analysis of owasp-amass/amass@79299dce87 (2026-09-06). Data as JSON: /api/errors/0e0c5e2240e571d0. Report an issue: GitHub.