{"record":{"id":"cd1c0c91beb1b941","repo":"Pumpkin-MC/Pumpkin","slug":"missing-expected-challenge-from-pending-connection","errorCode":null,"errorMessage":"Missing expected challenge from pending connection","messagePattern":"Missing expected challenge from pending connection","errorType":"error_code","errorClass":"VineError","httpStatus":null,"severity":"error","filePath":"crates/pumpkin/src/net/proxy/vine.rs","lineNumber":44,"sourceCode":"    #[error(\"No response data received\")]\n    NoData,\n    #[error(\"Vine response data too short (minimum 89 bytes)\")]\n    DataTooShort,\n    #[error(\"No public key or secret configured for Vine proxy\")]\n    MissingKeyConfig,\n    #[error(\"Invalid Ed25519 public key\")]\n    InvalidPublicKey,\n    #[error(\"Failed to verify Ed25519 signature\")]\n    InvalidSignature,\n    #[error(\"Failed to read forward version\")]\n    FailedReadForwardVersion,\n    #[error(\"Unsupported forwarding version {0}. Expected {1}\")]\n    UnsupportedForwardVersion(i32, i32),\n    #[error(\"Vine timestamp expired or desynchronized: skew of {0}s exceeds limit of {1}s\")]\n    TimestampExpired(i64, i64),\n    #[error(\"Vine challenge nonce mismatch\")]\n    ChallengeMismatch,\n    #[error(\"Missing expected challenge from pending connection\")]\n    MissingChallenge,\n    #[error(\"Failed to read address\")]\n    FailedReadAddress,\n    #[error(\"Failed to parse address\")]\n    FailedParseAddress,\n    #[error(\"Failed to read game profile name\")]\n    FailedReadProfileName,\n    #[error(\"Failed to read game profile UUID\")]\n    FailedReadProfileUUID,\n    #[error(\"Failed to read game profile properties\")]\n    FailedReadProfileProperties,\n}\n\n/// Initiates Vine modern forwarding handshake by sending a `CLoginPluginRequest`\n/// with a unique 16-byte challenge nonce to protect against replay attacks.\npub async fn vine_login(connection: &mut PendingConnection) {\n    let message_id: i32 = rand::random();\n    let challenge: [u8; 16] = rand::random();","sourceCodeStart":26,"sourceCodeEnd":62,"githubUrl":"https://github.com/Pumpkin-MC/Pumpkin/blob/8d4639e25a57c15e47448ec327c780d41bbf2356/crates/pumpkin/src/net/proxy/vine.rs#L26-L62","documentation":"VineError::MissingChallenge is returned at the start of receive_vine_plugin_response when expected_challenge is None (vine.rs:150) — i.e. no challenge nonce was recorded on the pending connection — yet a Vine plugin response arrived. The server cannot validate replay protection without the stored nonce, so it rejects the packet. This indicates an internal state inconsistency rather than a bad packet.","triggerScenarios":"A SLoginPluginResponse on the vine:player_info channel is processed for a PendingConnection whose vine_challenge field is None: vine_login was never invoked for this connection, the state was cleared/consumed already, or the response was dispatched to the wrong connection object.","commonSituations":"A client sends an unsolicited login plugin response without a prior request; the server processed two responses for one login and the stored challenge was already consumed; a code path reset or skipped vine_login (e.g. forwarding config changed mid-flight).","solutions":["Ensure vine_login is always invoked before any plugin response can arrive for that connection","Reject/drop unsolicited login plugin responses from clients early","Check connection state management so vine_challenge is not cleared before the response is handled","Verify each PendingConnection handles exactly one Vine exchange per login"],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":"// gate the response handler: only process if a Vine exchange was initiated\nif pending.vine_challenge.is_none() {\n    drop(pending); // unsolicited response — ignore instead of panicking on state\n    return;\n}","typeGuard":"fn expecting_vine_response(conn: &PendingConnection) -> bool {\n    conn.vine_challenge.is_some()\n}","tryCatchPattern":"match receive_vine_plugin_response(port, &config, response, pending.vine_challenge) {\n    Err(VineError::MissingChallenge) => {\n        tracing::debug!(\"Got Vine response without a stored challenge; ignoring unsolicited packet\");\n        disconnect(DisconnectReason::InvalidLoginState);\n    }\n    result => result?,\n}","preventionTips":["Always call vine_login before a connection can reach the plugin-response handling path","Clear vine_challenge exactly once, after the response is consumed, to avoid double-processing","Drop unsolicited login plugin responses early in the packet handler","Add a debug log when a response arrives with no stored challenge to catch state bugs early"],"tags":["state-management","minecraft","internal-state"],"backgroundTag":"invalid-state-transition","analyzedSha":"8d4639e25a57c15e47448ec327c780d41bbf2356","analyzedAt":"2026-09-09T15:32:22.916Z","contentChangedAt":"2026-09-09T15:32:22.916Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}