What causes "fiber: keyauth insufficient_scope requires scope" in gofiber/fiber?

Set Config.Scope to a space-delimited list of required scopes, e.g. "read write".

fiber: keyauth insufficient_scope requires scope

Error message

fiber: keyauth insufficient_scope requires scope

What it means

When keyauth Config.Error is set to ErrorInsufficientScope, RFC 6750 requires a scope parameter telling the client which scopes are needed. Leaving Config.Scope empty in that case panics in configDefault(), because the challenge would not tell the client what scopes to request.

Source

Thrown at middleware/keyauth/config.go:152

		case ErrorInvalidRequest, ErrorInvalidToken, ErrorInsufficientScope:
		default:
			panic("fiber: keyauth unsupported error token")
		}
	}
	if cfg.ErrorDescription != "" && cfg.Error == "" {
		panic("fiber: keyauth error_description requires error")
	}
	if cfg.ErrorURI != "" {
		if cfg.Error == "" {
			panic("fiber: keyauth error_uri requires error")
		}
		if u, err := url.Parse(cfg.ErrorURI); err != nil || !u.IsAbs() {
			panic("fiber: keyauth error_uri must be absolute")
		}
	}
	if cfg.Error == ErrorInsufficientScope {
		if cfg.Scope == "" {
			panic("fiber: keyauth insufficient_scope requires scope")
		}
		for scope := range strings.SplitSeq(cfg.Scope, " ") {
			if scope == "" || !isScopeToken(scope) {
				panic("fiber: keyauth scope contains invalid token")
			}
		}
	} else if cfg.Scope != "" {
		panic("fiber: keyauth scope requires insufficient_scope error")
	}

	return cfg
}

func isScopeToken(s string) bool {
	for i := 0; i < len(s); i++ {
		c := s[i]
		if c < 0x21 || c > 0x7e || c == '"' || c == '\\' {
			return false

View on GitHub (pinned to 9a4c7e57fe)

Solutions

Set Config.Scope to a space-delimited list of required scopes, e.g. "read write".
If you do not actually do scope checks, use a different Error code (invalid_token) instead of insufficient_scope.
Centralize scope strings in constants to avoid leaving the field empty by accident.

Example fix

// before
app.Use(keyauth.New(keyauth.Config{
    Validator: validateKey,
    Error:     keyauth.ErrorInsufficientScope,
}))
// after
app.Use(keyauth.New(keyauth.Config{
    Validator: validateKey,
    Error:     keyauth.ErrorInsufficientScope,
    Scope:     "read write",
}))

Defensive patterns

Strategy: validation

Validate before calling

if cfg.Error == keyauth.ErrorInsufficientScope && cfg.Scope == "" {
    log.Fatal("keyauth: insufficient_scope requires a non-empty Scope")
}

Prevention

Define required scopes as a constant and reference it in both validation logic and config.
Treat Error=insufficient_scope and Scope as a single coupled setting.

When it happens

Trigger: Calling keyauth.New() with Config.Error set to keyauth.ErrorInsufficientScope but Config.Scope left empty. The check at config.go:150-153 fires immediately after the error token validation passes.

Common situations: Enabling scope-based authorization for the first time and forgetting the scope list. Copying a config template that set Error but commented out Scope. Refactoring auth and dropping the scope string.

Related errors

AI-assisted analysis of gofiber/fiber@9a4c7e57fe (2026-08-04). Data as JSON: /data/errors/79d1a5bc49d76da9.json. Report an issue: GitHub.