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feat(tlsalert): add sendForceSniSequence and sendFatalAndClose helper functions to TlsAlert for improved SNI enforcement

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This commit is contained in:
Philipp Kunz
2025-03-17 14:27:10 +00:00
parent 3593e411cf
commit b55e2da23e
4 changed files with 100 additions and 116 deletions
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7
changelog.md
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@@ -1,5 +1,12 @@
# Changelog
## 2025-03-17 - 4.2.0 - feat(tlsalert)
add sendForceSniSequence and sendFatalAndClose helper functions to TlsAlert for improved SNI enforcement
- Introduce sendForceSniSequence to combine multiple alerts and force clients to provide SNI
- Add sendFatalAndClose to immediately send a fatal alert and close the connection
- Enhance TLS alert handling for better browser compatibility and error management
## 2025-03-17 - 4.1.16 - fix(tls)
Improve TLS alert handling in connection handler: use the new TlsAlert class to send proper unrecognized_name alerts when a ClientHello is missing SNI and wait for a retry on the same connection before closing. Also, add alertFallbackTimeout tracking to connection records for better timeout management.

2
ts/00_commitinfo_data.ts
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@@ -3,6 +3,6 @@
*/
export const commitinfo = {
name: '@push.rocks/smartproxy',
version: '4.1.16',
version: '4.2.0',
description: 'A powerful proxy package that effectively handles high traffic, with features such as SSL/TLS support, port proxying, WebSocket handling, dynamic routing with authentication options, and automatic ACME certificate management.'
}

167
ts/classes.pp.connectionhandler.ts
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@@ -11,7 +11,6 @@ import { TlsManager } from './classes.pp.tlsmanager.js';
import { NetworkProxyBridge } from './classes.pp.networkproxybridge.js';
import { TimeoutManager } from './classes.pp.timeoutmanager.js';
import { PortRangeManager } from './classes.pp.portrangemanager.js';
import { TlsAlert } from './classes.pp.tlsalert.js';
/**
* Handles new connection processing and setup logic
@@ -561,125 +560,64 @@ export class ConnectionHandler {
// Block ClientHello without SNI when allowSessionTicket is false
console.log(
`[${connectionId}] No SNI detected in ClientHello and allowSessionTicket=false. ` +
`Sending unrecognized_name alert to encourage immediate retry with SNI on same connection.`
`Sending warning unrecognized_name alert to encourage immediate retry with SNI.`
);
try {
// Send the alert but do NOT end the connection
// Using our new TlsAlert class for better alert management
socket.cork();
socket.write(TlsAlert.alerts.unrecognizedName);
socket.uncork();
console.log(
`[${connectionId}] Alert sent, waiting for new ClientHello on same connection...`
// Set the termination reason first
if (record.incomingTerminationReason === null) {
record.incomingTerminationReason = 'session_ticket_blocked_no_sni';
this.connectionManager.incrementTerminationStat(
'incoming',
'session_ticket_blocked_no_sni'
);
}
// Remove existing data listener and wait for a new ClientHello
socket.removeAllListeners('data');
// Create a warning-level alert for unrecognized_name
// This encourages Chrome to retry immediately with SNI
const serverNameUnknownAlertData = Buffer.from([
0x15, // Alert record type
0x03,
0x03, // TLS 1.2 version
0x00,
0x02, // Length
0x01, // Warning alert level (not fatal)
0x70, // unrecognized_name alert (code 112)
]);
// Set up a new data handler to capture the next message
socket.once('data', (retryChunk) => {
// Cancel the fallback timeout as we received data
if (record.alertFallbackTimeout) {
clearTimeout(record.alertFallbackTimeout);
record.alertFallbackTimeout = null;
}
// Check if this is a new ClientHello
if (this.tlsManager.isClientHello(retryChunk)) {
console.log(`[${connectionId}] Received new ClientHello after alert`);
// Extract SNI from the new ClientHello
const newServerName = this.tlsManager.extractSNI(retryChunk, connInfo) || '';
if (newServerName) {
console.log(`[${connectionId}] New ClientHello contains SNI: ${newServerName}`);
// Update the record with the new SNI
record.lockedDomain = newServerName;
// Continue with normal connection setup using the new chunk with SNI
setupConnection(newServerName, retryChunk);
} else {
console.log(
`[${connectionId}] New ClientHello still missing SNI, closing connection`
);
// If still no SNI after retry, now we can close the connection
if (record.incomingTerminationReason === null) {
record.incomingTerminationReason = 'session_ticket_blocked_no_sni';
this.connectionManager.incrementTerminationStat(
'incoming',
'session_ticket_blocked_no_sni'
);
}
// Send a close_notify alert before ending the connection
TlsAlert.sendCloseNotify(socket)
.catch((err) => {
console.log(`[${connectionId}] Error sending close_notify: ${err.message}`);
})
.finally(() => {
// Clean up even if sending the alert fails
this.connectionManager.cleanupConnection(
record,
'session_ticket_blocked_no_sni'
);
});
}
} else {
console.log(
`[${connectionId}] Received non-ClientHello data after alert, closing connection`
);
// If we got something other than a ClientHello, close the connection
if (record.incomingTerminationReason === null) {
record.incomingTerminationReason = 'invalid_protocol';
this.connectionManager.incrementTerminationStat('incoming', 'invalid_protocol');
}
// Send a protocol_version alert before ending the connection
TlsAlert.send(socket, TlsAlert.LEVEL_FATAL, TlsAlert.PROTOCOL_VERSION, true)
.catch((err) => {
console.log(
`[${connectionId}] Error sending protocol_version alert: ${err.message}`
);
})
.finally(() => {
// Clean up even if sending the alert fails
this.connectionManager.cleanupConnection(record, 'invalid_protocol');
});
}
});
// Set a fallback timeout in case the client doesn't respond
const fallbackTimeout = setTimeout(() => {
console.log(`[${connectionId}] No response after alert, closing connection`);
if (record.incomingTerminationReason === null) {
record.incomingTerminationReason = 'alert_timeout';
this.connectionManager.incrementTerminationStat('incoming', 'alert_timeout');
}
// Send a close_notify alert before ending the connection
TlsAlert.sendCloseNotify(socket)
.catch((err) => {
console.log(`[${connectionId}] Error sending close_notify: ${err.message}`);
})
.finally(() => {
// Clean up even if sending the alert fails
this.connectionManager.cleanupConnection(record, 'alert_timeout');
});
}, 10000); // 10 second timeout
// Make sure the timeout doesn't keep the process alive
if (fallbackTimeout.unref) {
fallbackTimeout.unref();
try {
// Use cork/uncork to ensure the alert is sent as a single packet
socket.cork();
const writeSuccessful = socket.write(serverNameUnknownAlertData);
socket.uncork();
// Function to handle the clean socket termination - but more gradually
const finishConnection = () => {
// Give Chrome more time to process the alert before closing
// We won't call destroy() at all - just end() and let the socket close naturally
// Log the cleanup but wait for natural closure
setTimeout(() => {
socket.end();
this.connectionManager.cleanupConnection(record, 'session_ticket_blocked_no_sni');
}, 1000); // Longer delay to let socket cleanup happen naturally
};
if (writeSuccessful) {
// Wait longer before ending connection to ensure alert is processed by client
setTimeout(finishConnection, 200); // Increased from 50ms to 200ms
} else {
// If the kernel buffer was full, wait for the drain event
socket.once('drain', () => {
// Wait longer after drain as well
setTimeout(finishConnection, 200);
});
// Safety timeout is increased too
setTimeout(() => {
socket.removeAllListeners('drain');
finishConnection();
}, 400); // Increased from 250ms to 400ms
}
// Store the timeout in the record so it can be cleared during cleanup
record.alertFallbackTimeout = fallbackTimeout;
} catch (err) {
// If we can't send the alert, fall back to immediate termination
console.log(`[${connectionId}] Error sending TLS alert: ${err.message}`);
@@ -687,7 +625,6 @@ export class ConnectionHandler {
this.connectionManager.cleanupConnection(record, 'session_ticket_blocked_no_sni');
}
// Return early to prevent the normal flow
return;
}
}

40
ts/classes.pp.tlsalert.ts
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@@ -173,6 +173,7 @@ export class TlsAlert {
protocolVersion: TlsAlert.createFatal(TlsAlert.PROTOCOL_VERSION),
insufficientSecurity: TlsAlert.createFatal(TlsAlert.INSUFFICIENT_SECURITY),
internalError: TlsAlert.createFatal(TlsAlert.INTERNAL_ERROR),
unrecognizedNameFatal: TlsAlert.createFatal(TlsAlert.UNRECOGNIZED_NAME),
};
/**
@@ -215,4 +216,43 @@ export class TlsAlert {
const level = fatal ? this.LEVEL_FATAL : this.LEVEL_WARNING;
return this.send(socket, level, this.CERTIFICATE_EXPIRED, closeAfterSend, closeDelay);
}
/**
* Send a sequence of alerts to force SNI from clients
* This combines multiple alerts to ensure maximum browser compatibility
*
* @param socket The socket to send the alerts to
* @returns Promise that resolves when all alerts have been sent
*/
static async sendForceSniSequence(socket: net.Socket): Promise<void> {
try {
// Send unrecognized_name (warning)
socket.cork();
socket.write(this.alerts.unrecognizedName);
socket.uncork();
// Give the socket time to send the alert
return new Promise((resolve) => {
setTimeout(resolve, 50);
});
} catch (err) {
return Promise.reject(err);
}
}
/**
* Send a fatal level alert that immediately terminates the connection
*
* @param socket The socket to send the alert to
* @param description Alert description code
* @param closeDelay Milliseconds to wait before closing the connection (default: 100ms)
* @returns Promise that resolves when the alert has been sent and the connection closed
*/
static async sendFatalAndClose(
socket: net.Socket,
description: number,
closeDelay: number = 100
): Promise<void> {
return this.send(socket, this.LEVEL_FATAL, description, true, closeDelay);
}
}