owasp-amass/amass · error

expected 'engine' to be a string, got %T

Error message

expected 'engine' to be a string, got %T

What it means

loadEngineSettings found a non-nil value under the 'engine' option key, but its Go type is not string (e.g. a map or number from a malformed YAML/JSON config). The %T verb names the actual type encountered, making this a type-shape validation of user-supplied configuration.

Source

Thrown at config/engineapi.go:53

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// loadEngineSettings is responsible for extracting the "engine" URL from the application's configuration
// and initializing the EngAPI structure. It performs several checks such as ensuring the configuration options
// are initialized and the "engine" key is present and of type string. If any of these checks fail, an error is returned.
func (c *Config) loadEngineSettings(cfg *Config) error {
	// Check if configuration options are initialized; if not, return an error.
	if c.Options == nil {
		return fmt.Errorf("config options are not initialized")
	}
	// Attempt to retrieve the "engine" value from the configuration options.
	apiURIInterface, ok := c.Options["engine"]
	if !ok {
		return c.LoadEngineEnvSettings()
	}
	// Assert that the "engine" option is of type string; if not, return an error specifying the incorrect type received.
	apiURI, ok := apiURIInterface.(string)
	if !ok {
		return fmt.Errorf("expected 'engine' to be a string, got %T", apiURIInterface)
	}
	// Load the Engine API URI information into the EngAPI structure.
	// If there's an error during this process, it's returned to the calling function.
	if err := c.loadEngineURI(apiURI); err != nil {
		return err
	}
	return nil
}

// LoadEngineEnvSettings initializes the EngAPI structure with the Environment variables.
func (c *Config) LoadEngineEnvSettings() error {
	apiURI := ""
	eng := &EngAPI{}

	h := "localhost"
	if henv, set := os.LookupEnv(engineHost); set {
		h = henv
	}

View on GitHub (pinned to 79299dce87)

Solutions

1. Fix the config file so 'engine' is a URI string (e.g. "grpc://user:pass@host:port")
2. If the type is a map by design, serialize/flatten it to a URI string before it reaches Options
3. Add a config schema check that rejects non-string 'engine' values with a file/line reference

When it happens

Trigger: Thrown at config/engineapi.go:53 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of owasp-amass/amass@79299dce87 (2026-09-06). Data as JSON: /api/errors/544fee6ce870f6f4. Report an issue: GitHub.