{"record":{"id":"3a00292b7397cb2e","repo":"crowdsecurity/crowdsec","slug":"failed-to-generate-challenge-js-w","errorCode":null,"errorMessage":"failed to generate challenge JS: %w","messagePattern":"failed to generate challenge JS: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/appsec/challenge/challenge.go","lineNumber":547,"sourceCode":"\t\tc.preWarmCancel()\n\t}\n\n\treturn c.r.Close(ctx)\n}\n\n// GetChallengePage renders the challenge HTML page with the given PoW difficulty.\n// If difficulty is 0, the default difficulty is used.\nfunc (c *ChallengeRuntime) GetChallengePage(ctx context.Context, userAgent string, difficulty int) (string, error) {\n\t_ = userAgent\n\n\tif difficulty <= 0 {\n\t\tdifficulty = c.powDifficulty\n\t}\n\n\tchallengeCode := c.getChallengeCode()\n\tif challengeCode == \"\" {\n\t\tif err := c.generateAndCacheChallengeJS(ctx); err != nil {\n\t\t\treturn \"\", fmt.Errorf(\"failed to generate challenge JS: %w\", err)\n\t\t}\n\t\tchallengeCode = c.getChallengeCode()\n\t\tif challengeCode == \"\" {\n\t\t\treturn \"\", errors.New(\"challenge JS cache is empty\")\n\t\t}\n\t}\n\n\t// Issuance is stateless (only submission is stateful — see the single-use\n\t// burn in ValidateChallengeResponse). `r` seeds the per-challenge secret\n\t// `s = HMAC(K_epoch, r)` the client derives from the obfuscated dynamic\n\t// module, so `s` never appears in plain HTML; the PoW MAC binds the salt to\n\t// `r`+ts so a client can't pick a favorable salt.\n\tts := fmt.Sprintf(\"%d\", time.Now().UnixNano())\n\tr, err := generateChallengeNonce()\n\tif err != nil {\n\t\treturn \"\", err\n\t}\n\tpowSalt, err := generatePowPrefix()","sourceCodeStart":529,"sourceCodeEnd":565,"githubUrl":"https://github.com/crowdsecurity/crowdsec/blob/909b5157986a2b2c2163300fdaef5ed01289f7d2/pkg/appsec/challenge/challenge.go#L529-L565","documentation":"GetChallengePage serves the challenge JS from the runtime cache. If the cached challenge code is empty, it attempts a synchronous generateAndCacheChallengeJS; if that generation fails, this error wraps the cause and no challenge page can be served.","triggerScenarios":"Calling GetChallengePage when getChallengeCode() returns \"\" (cache empty — e.g. constructor fell back and generation never succeeded, or cache was cleared) and generateAndCacheChallengeJS(ctx) errors (ctx cancelled, obfuscation failure).","commonSituations":"Request arriving before any bundle was ever generated; expired/cleared cache with a request context too short for the ~5s obfuscation; upstream generation failures after a bad rebuild.","solutions":["Rebuild/restart so the baked-in initial bundle is present (`go generate`, `make build`).","Check the wrapped error: fix the underlying generation failure (context deadline, crypto, template).","Increase request/startup timeouts so the ~5s synchronous obfuscation can finish.","Verify the pre-warmer is running (skipPreWarm=false) so the cache is never empty."],"exampleFix":"// before: challenge served with an already-half-expired request ctx\npage, err := rt.GetChallengePage(req.Context(), opts)\n// after: use a detached ctx with a generation budget\npage, err := rt.GetChallengePage(context.WithTimeout(context.Background(), 30*time.Second), opts)","handlingStrategy":"retry","validationCode":null,"typeGuard":null,"tryCatchPattern":"page, err := rt.GetChallengePage(ctx, opts)\nif err != nil {\n    var genErr error\n    if errors.As(err, &genErr) && strings.Contains(err.Error(), \"challenge JS\") {\n        // one bounded retry with a fresh, longer-lived context\n    }\n    http.Error(w, \"challenge unavailable\", http.StatusServiceUnavailable)\n}","preventionTips":["Keep the pre-warmer enabled so the cache is never empty.","Use request contexts long enough for a synchronous ~5s generation fallback.","Rebuild after pulling new code so embedded bundles match.","Watch logs for repeated empty-cache warnings."],"tags":["appsec","challenge","cache","obfuscation"],"backgroundTag":"module-init-failed","analyzedSha":"909b5157986a2b2c2163300fdaef5ed01289f7d2","analyzedAt":"2026-09-06T12:27:26.012Z","contentChangedAt":"2026-09-06T12:27:26.012Z","schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}