crowdsecurity/crowdsec · critical

failed to generate initial challenge bundle: %w

Error message

failed to generate initial challenge bundle: %w

What it means

NewChallengeRuntime first tries to seed the challenge JS cache from the baked-in initial bundle (generated at build time via `go generate`). If that bundle is missing or corrupt, it falls back to obfuscating the challenge code synchronously; if that synchronous generation also fails, the constructor aborts and this error wraps the underlying cause. The AppSec challenge runtime cannot start without at least one challenge bundle.

Source

Thrown at pkg/appsec/challenge/challenge.go:489

		powDifficulty:      defaultPowDifficulty,
		keys:               keys,
		cryptoPoolSize:     cryptoPoolSize,
		dynamicModuleCache: make(map[int64][]string),
		cookieTTL:          cookieTTL,
		maxCookieLen:       maxCookieLen,
		htmlTpl:            htmlTpl,
		spent:              newSpentSet(spentSetMaxEntries),
		logger:             logger,
	}

	// Load the build-time-obfuscated challenge code from the baked-in bundle so
	// we can serve immediately.
	if err := challengeRuntime.seedCacheFromInitialBundle(); err != nil {
		// Initial bundle missing/corrupt (e.g. `go generate` not run): fall back
		// to obfuscating the challenge code synchronously.
		logger.Warnf("failed to load baked-in initial challenge bundle (%v); falling back to synchronous generation", err)
		if err := challengeRuntime.generateAndCacheChallengeJS(ctx); err != nil {
			return nil, fmt.Errorf("failed to generate initial challenge bundle: %w", err)
		}
	}

	// Pre-warm the current epoch's dynamic module so the first GetChallengePage
	// doesn't pay the ~5s obfuscation cost on the request path. The background
	// pre-warmer then re-obfuscates on every rotation; it runs under a context
	// owned by Close() rather than the constructor ctx, so a reload (which
	// reuses the process ctx) can stop it — see Close().
	if !resolvedOpts.skipPreWarm {
		if _, err := challengeRuntime.currentDynamicModule(ctx); err != nil {
			return nil, fmt.Errorf("warm dynamic key module: %w", err)
		}

		runCtx, cancel := context.WithCancel(ctx)
		challengeRuntime.preWarmCancel = cancel
		go challengeRuntime.dynamicModulePreWarmer(runCtx)
	}

View on GitHub (pinned to 909b515798)

Solutions

  1. Run `go generate ./pkg/appsec/challenge/...` (or `make generate`) so the initial bundle is baked in, then rebuild.
  2. Rebuild the binaries from a clean tree (`make build`) to regenerate the embedded bundle.
  3. Ensure the startup context passed to NewChallengeRuntime is not already cancelled and the process is not starved of CPU (obfuscation takes ~5s).
  4. Check the wrapped error in the message for the specific generation failure (crypto rand, template, etc.) and fix that root cause.

Example fix

// before: startup ctx with a short timeout kills the ~5s obfuscation
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
rt, err := NewChallengeRuntime(ctx, opts)
// after
ctx := context.Background()
rt, err := NewChallengeRuntime(ctx, opts)
Defensive patterns

Strategy: fallback

Validate before calling

// preflight: ensure the baked-in bundle exists before constructing
if challenge.GetChallengeCode() == "" {
    logger.Warn("initial challenge bundle missing; run `go generate` before building")
}

Try / catch

rt, err := NewChallengeRuntime(ctx, opts)
if err != nil {
    if errors.Is(err, context.DeadlineExceeded) {
        logger.Error("challenge init exceeded deadline; increase startup timeout")
    }
    return fmt.Errorf("appsec challenge runtime init: %w", err)
}

Prevention

When it happens

Trigger: Calling NewChallengeRuntime (directly or via Configure during AppSec component load) when seedCacheFromInitialBundle fails (bundle not generated / corrupt embed) AND generateAndCacheChallengeJS also returns an error (obfuscation timeout, context cancelled, crypto/template failure).

Common situations: Building from source without running `go generate`; a broken build that embedded an empty bundle; a startup context already cancelled/expired before obfuscation completes (obfuscation can take ~5s); resource exhaustion on constrained hosts.

Related errors

AI-assisted analysis of crowdsecurity/crowdsec@909b515798 (2026-09-06). Data as JSON: /api/errors/8f4f3b9ea005820e. Report an issue: GitHub.