{"record":{"id":"9204e55eaf9cb618","repo":"crowdsecurity/crowdsec","slug":"render-challenge-page-w","errorCode":null,"errorMessage":"render challenge page: %w","messagePattern":"render challenge page: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/appsec/challenge/challenge.go","lineNumber":600,"sourceCode":"\t// carries the per-epoch K, so K never appears in plain HTML.\n\tdynamicModule, err := c.currentDynamicModule(ctx)\n\tif err != nil {\n\t\treturn \"\", fmt.Errorf(\"build dynamic key module: %w\", err)\n\t}\n\n\tvar renderedPage strings.Builder\n\n\tif err := c.htmlTpl.Execute(&renderedPage, map[string]interface{}{\n\t\t\"JSChallenge\":   challengeCode,\n\t\t\"DynamicModule\": dynamicModule,\n\t\t\"FPScannerPath\": ChallengeFPScannerPath,\n\t\t\"PowDifficulty\": difficulty,\n\t\t\"PowPrefix\":     powSalt,\n\t\t\"PowMAC\":        powMAC,\n\t\t\"Timestamp\":     ts,\n\t\t\"R\":             r,\n\t}); err != nil {\n\t\treturn \"\", fmt.Errorf(\"render challenge page: %w\", err)\n\t}\n\treturn renderedPage.String(), nil\n}\n\n// ValidateChallengeResponse parses a submit POST and runs the full chain:\n// freshness + PoW-salt authenticity + difficulty, PoW solution,\n// the submission signature `sig` (keyed by the never-transmitted s = HMAC(K_epoch, r)),\n// a single-use burn of `r` (replay protection),\n// and fingerprint de-obfuscation. On success it returns the sealed\n// cookie, decoded FingerprintData, and the proven PoW difficulty; failures\n// return a generic error so the caller doesn't leak which stage failed.\nfunc (c *ChallengeRuntime) ValidateChallengeResponse(request *http.Request, body []byte) (*cookie.AppsecCookie, FingerprintData, int, error) {\n\tvars, err := url.ParseQuery(string(body))\n\tif err != nil {\n\t\treturn nil, FingerprintData{}, 0, fmt.Errorf(\"%w: %w\", ErrChallengePayload, err)\n\t}\n\n\tencryptedFingerprint := vars.Get(\"f\")","sourceCodeStart":582,"sourceCodeEnd":618,"githubUrl":"https://github.com/crowdsecurity/crowdsec/blob/909b5157986a2b2c2163300fdaef5ed01289f7d2/pkg/appsec/challenge/challenge.go#L582-L618","documentation":"GetChallengePage renders the final challenge HTML via the runtime's htmlTpl template. If template execution fails (bad template syntax, missing/invalid template data fields), the error is wrapped as 'render challenge page'. This is an internal template/data contract failure, not a client problem.","triggerScenarios":"Calling GetChallengePage when htmlTpl.Execute returns an error — malformed embedded template, or template data map missing a field the template references (JSChallenge, DynamicModule, PowDifficulty, PowPrefix, PowMAC, Timestamp, R).","commonSituations":"Custom/patched builds with edited challenge HTML templates; a build where the embedded template drifted from the data map keys; extremely rare runtime write failures.","solutions":["Rebuild from a clean tree so the embedded htmlTpl matches the data the code passes (`make build`).","Check the wrapped error for the template name/line it reports and fix that template spot.","If you customized the template, re-sync it with the data keys rendered by GetChallengePage.","Report upstream if it reproduces on an unmodified build — it indicates a code/template contract bug."],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"page, err := rt.GetChallengePage(ctx, opts)\nif err != nil {\n    if strings.Contains(err.Error(), \"render challenge page\") {\n        logger.WithError(err).Error(\"challenge template render failed; check embedded template/data contract\")\n        http.Error(w, \"internal error\", http.StatusInternalServerError)\n    }\n}","preventionTips":["Never hand-edit the embedded challenge HTML template without rebuilding.","Keep template data keys and htmlTpl placeholders in sync.","Rebuild from a clean tree after template changes.","Treat occurrences on stock builds as a bug to report upstream."],"tags":["appsec","challenge","template","rendering"],"backgroundTag":"template-render-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"}