{"record":{"id":"27aa0dd39d9ca5b4","repo":"Kuberwastaken/claurst","slug":"failed-to-generate-pkce-verifier","errorCode":null,"errorMessage":"Failed to generate PKCE verifier: {}","messagePattern":"Failed to generate PKCE verifier: (.+?)","errorType":"exception","errorClass":"anyhow::Error","httpStatus":null,"severity":"error","filePath":"src-rust/crates/mcp/src/oauth.rs","lineNumber":198,"sourceCode":"                    .get(\"token_endpoint\")\n                    .and_then(|value| value.as_str())\n                    .unwrap_or(fallback.token_endpoint.as_str())\n                    .to_string(),\n            })\n        }\n        Ok(_) | Err(_) => Ok(fallback),\n    }\n}\n\npub async fn begin_mcp_auth(\n    server_name: &str,\n    server_url: &str,\n) -> anyhow::Result<McpAuthSession> {\n    let metadata = fetch_oauth_metadata(server_url).await?;\n    let redirect_port = oauth_port_alloc()\n        .map_err(|e| anyhow::anyhow!(\"Failed to allocate OAuth redirect port: {}\", e))?;\n    let redirect_uri = format!(\"http://127.0.0.1:{}/callback\", redirect_port);\n    let verifier = pkce_verifier().map_err(|e| anyhow::anyhow!(\"Failed to generate PKCE verifier: {}\", e))?;\n    let auth_url = build_mcp_auth_url(\n        &metadata.authorization_endpoint,\n        &redirect_uri,\n        &verifier,\n    );\n\n    Ok(McpAuthSession {\n        server_name: server_name.to_string(),\n        auth_url,\n        redirect_uri,\n        verifier,\n        metadata,\n    })\n}\n\nasync fn bind_callback_listener(\n    redirect_uri: &str,\n) -> anyhow::Result<(TcpListener, String, String)> {","sourceCodeStart":180,"sourceCodeEnd":216,"githubUrl":"https://github.com/Kuberwastaken/claurst/blob/b0637c97ec34144387cbf2f74f65df6d16a6cef1/src-rust/crates/mcp/src/oauth.rs#L180-L216","documentation":"Thrown in begin_mcp_auth when the local PKCE code-verifier generator (pkce_verifier) fails. The verifier is a cryptographically random string required for the OAuth 2.0 PKCE flow against the MCP server's authorization endpoint. Failure means the random source or encoding step errored, so the auth session cannot proceed.","triggerScenarios":"Calling run_mcp_auth_flow / begin_mcp_auth when pkce_verifier() returns Err — e.g. the OS entropy source (/dev/urandom, getrandom) is unavailable or the base64url encoding of the random bytes fails.","commonSituations":"Running in a heavily sandboxed container that blocks access to the system RNG; restricted seccomp profiles blocking the getrandom syscall; embedded/minimal Linux images without a configured entropy source.","solutions":["Check the inner error ({} placeholder) for the underlying RNG/encoding cause and fix the environment accordingly","Verify the container/sandbox allows the getrandom syscall or has /dev/urandom available","Retry the auth flow — RNG failures are often transient","If persistent, upgrade the runtime image or the rand/getrandom dependency"],"exampleFix":"# Sandbox blocking getrandom\ndocker run --security-opt seccomp=unconfined ...\n# or ensure /dev/urandom exists:\nls -l /dev/urandom","handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"match pkce_verifier() {\n    Ok(v) => v,\n    Err(e) => { eprintln!(\"PKCE generation failed: {e}; check entropy source\"); return; }\n}","preventionTips":["Run in environments with a working RNG (/dev/urandom, getrandom)","Avoid seccomp profiles that block getrandom","Retry transient RNG failures before giving up"],"tags":["oauth","pkce","cryptography"],"backgroundTag":"missing-credentials","analyzedSha":"b0637c97ec34144387cbf2f74f65df6d16a6cef1","analyzedAt":"2026-09-10T00:24:58.650Z","contentChangedAt":"2026-09-10T00:24:58.650Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}