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feat(SniHandler): Enhance SNI extraction to support fragmented ClientHello messages, TLS 1.3 early data, and improved PSK parsing

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This commit is contained in:
Philipp Kunz 2025-03-11 17:33:31 +00:00
parent 6daf4c914d
commit 0e12706176
3 changed files with 343 additions and 17 deletions
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9
changelog.md
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@ -1,5 +1,14 @@
# Changelog
## 2025-03-11 - 3.38.0 - feat(SniHandler)
Enhance SNI extraction to support fragmented ClientHello messages, TLS 1.3 early data, and improved PSK parsing
- Added isTlsApplicationData method for detecting TLS application data packets
- Implemented handleFragmentedClientHello to buffer and reassemble fragmented ClientHello messages
- Extended extractSNIWithResumptionSupport to accept connection information and use reassembled data
- Added detection for TLS 1.3 early data (0-RTT) in the ClientHello, supporting session resumption scenarios
- Improved logging and heuristics for handling potential connection racing in modern browsers
## 2025-03-11 - 3.37.3 - fix(snihandler)
Enhance SNI extraction to support TLS 1.3 PSK-based session resumption by adding a dedicated extractSNIFromPSKExtension method and improved logging for session resumption indicators.

2
ts/00_commitinfo_data.ts
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@ -3,6 +3,6 @@
*/
export const commitinfo = {
name: '@push.rocks/smartproxy',
version: '3.37.3',
version: '3.38.0',
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.'
}

349
ts/classes.snihandler.ts
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@ -2,17 +2,25 @@ import { Buffer } from 'buffer';
/**
* SNI (Server Name Indication) handler for TLS connections.
* Provides robust extraction of SNI values from TLS ClientHello messages.
* Provides robust extraction of SNI values from TLS ClientHello messages
* with support for fragmented packets, TLS 1.3 resumption, and Chrome-specific
* connection behaviors.
*/
export class SniHandler {
// TLS record types and constants
private static readonly TLS_HANDSHAKE_RECORD_TYPE = 22;
private static readonly TLS_APPLICATION_DATA_TYPE = 23; // TLS Application Data record type
private static readonly TLS_CLIENT_HELLO_HANDSHAKE_TYPE = 1;
private static readonly TLS_SNI_EXTENSION_TYPE = 0x0000;
private static readonly TLS_SESSION_TICKET_EXTENSION_TYPE = 0x0023;
private static readonly TLS_SNI_HOST_NAME_TYPE = 0;
private static readonly TLS_PSK_EXTENSION_TYPE = 0x0029; // Pre-Shared Key extension type for TLS 1.3
private static readonly TLS_PSK_KE_MODES_EXTENSION_TYPE = 0x002D; // PSK Key Exchange Modes
private static readonly TLS_EARLY_DATA_EXTENSION_TYPE = 0x002A; // Early Data (0-RTT) extension
// Buffer for handling fragmented ClientHello messages
private static fragmentedBuffers: Map<string, Buffer> = new Map();
private static fragmentTimeout: number = 1000; // ms to wait for fragments before cleanup
/**
* Checks if a buffer contains a TLS handshake message (record type 22)
@ -23,6 +31,107 @@ export class SniHandler {
return buffer.length > 0 && buffer[0] === this.TLS_HANDSHAKE_RECORD_TYPE;
}
/**
* Checks if a buffer contains TLS application data (record type 23)
* @param buffer - The buffer to check
* @returns true if the buffer starts with a TLS application data record type
*/
public static isTlsApplicationData(buffer: Buffer): boolean {
return buffer.length > 0 && buffer[0] === this.TLS_APPLICATION_DATA_TYPE;
}
/**
* Creates a connection ID based on source/destination information
* Used to track fragmented ClientHello messages across multiple packets
*
* @param connectionInfo - Object containing connection identifiers (IP/port)
* @returns A string ID for the connection
*/
public static createConnectionId(connectionInfo: {
sourceIp?: string;
sourcePort?: number;
destIp?: string;
destPort?: number;
}): string {
const { sourceIp, sourcePort, destIp, destPort } = connectionInfo;
return `${sourceIp}:${sourcePort}-${destIp}:${destPort}`;
}
/**
* Handles potential fragmented ClientHello messages by buffering and reassembling
* TLS record fragments that might span multiple TCP packets.
*
* @param buffer - The current buffer fragment
* @param connectionId - Unique identifier for the connection
* @param enableLogging - Whether to enable logging
* @returns A complete buffer if reassembly is successful, or undefined if more fragments are needed
*/
public static handleFragmentedClientHello(
buffer: Buffer,
connectionId: string,
enableLogging: boolean = false
): Buffer | undefined {
const log = (message: string) => {
if (enableLogging) {
console.log(`[SNI Fragment] ${message}`);
}
};
// Check if we've seen this connection before
if (!this.fragmentedBuffers.has(connectionId)) {
// New connection, start with this buffer
this.fragmentedBuffers.set(connectionId, buffer);
// Set timeout to clean up if we don't get a complete ClientHello
setTimeout(() => {
if (this.fragmentedBuffers.has(connectionId)) {
this.fragmentedBuffers.delete(connectionId);
log(`Connection ${connectionId} timed out waiting for complete ClientHello`);
}
}, this.fragmentTimeout);
// Evaluate if this buffer already contains a complete ClientHello
try {
if (buffer.length >= 5) {
const recordLength = (buffer[3] << 8) + buffer[4];
if (buffer.length >= recordLength + 5) {
log(`Initial buffer contains complete ClientHello, length: ${buffer.length}`);
return buffer;
}
}
} catch (e) {
log(`Error checking initial buffer completeness: ${e}`);
}
log(`Started buffering connection ${connectionId}, initial size: ${buffer.length}`);
return undefined; // Need more fragments
} else {
// Existing connection, append this buffer
const existingBuffer = this.fragmentedBuffers.get(connectionId)!;
const newBuffer = Buffer.concat([existingBuffer, buffer]);
this.fragmentedBuffers.set(connectionId, newBuffer);
log(`Appended to buffer for ${connectionId}, new size: ${newBuffer.length}`);
// Check if we now have a complete ClientHello
try {
if (newBuffer.length >= 5) {
const recordLength = (newBuffer[3] << 8) + newBuffer[4];
if (newBuffer.length >= recordLength + 5) {
log(`Assembled complete ClientHello, length: ${newBuffer.length}`);
// Complete message received, remove from tracking
this.fragmentedBuffers.delete(connectionId);
return newBuffer;
}
}
} catch (e) {
log(`Error checking reassembled buffer completeness: ${e}`);
}
return undefined; // Still need more fragments
}
}
/**
* Checks if a buffer contains a TLS ClientHello message
* @param buffer - The buffer to check
@ -466,6 +575,93 @@ export class SniHandler {
}
}
/**
* Checks if the buffer contains TLS 1.3 early data (0-RTT)
* @param buffer - The buffer to check
* @param enableLogging - Whether to enable logging
* @returns true if early data is detected
*/
public static hasEarlyData(
buffer: Buffer,
enableLogging: boolean = false
): boolean {
const log = (message: string) => {
if (enableLogging) {
console.log(`[Early Data] ${message}`);
}
};
try {
// Check if this is a valid ClientHello first
if (!this.isClientHello(buffer)) {
return false;
}
// Find the extensions section
let pos = 5; // Start after record header
// Skip handshake type (1 byte)
pos += 1;
// Skip handshake length (3 bytes)
pos += 3;
// Skip client version (2 bytes)
pos += 2;
// Skip client random (32 bytes)
pos += 32;
// Skip session ID
if (pos + 1 > buffer.length) return false;
const sessionIdLength = buffer[pos];
pos += 1 + sessionIdLength;
// Skip cipher suites
if (pos + 2 > buffer.length) return false;
const cipherSuitesLength = (buffer[pos] << 8) + buffer[pos + 1];
pos += 2 + cipherSuitesLength;
// Skip compression methods
if (pos + 1 > buffer.length) return false;
const compressionMethodsLength = buffer[pos];
pos += 1 + compressionMethodsLength;
// Check if we have extensions
if (pos + 2 > buffer.length) return false;
// Get extensions length
const extensionsLength = (buffer[pos] << 8) + buffer[pos + 1];
pos += 2;
// Extensions end position
const extensionsEnd = pos + extensionsLength;
if (extensionsEnd > buffer.length) return false;
// Look for early data extension
while (pos + 4 <= extensionsEnd) {
const extensionType = (buffer[pos] << 8) + buffer[pos + 1];
pos += 2;
const extensionLength = (buffer[pos] << 8) + buffer[pos + 1];
pos += 2;
if (extensionType === this.TLS_EARLY_DATA_EXTENSION_TYPE) {
log('Early Data (0-RTT) extension detected');
return true;
}
// Skip to next extension
pos += extensionLength;
}
return false;
} catch (error) {
log(`Error checking for early data: ${error}`);
return false;
}
}
/**
* Attempts to extract SNI from an initial ClientHello packet and handles
* session resumption edge cases more robustly than the standard extraction.
@ -474,44 +670,165 @@ export class SniHandler {
* 1. Standard SNI extraction
* 2. TLS 1.3 PSK-based resumption (Chrome, Firefox, etc.)
* 3. Session ticket-based resumption
* 4. Fragmented ClientHello messages
* 5. TLS 1.3 Early Data (0-RTT)
* 6. Chrome's connection racing behaviors
*
* @param buffer - The buffer containing the TLS ClientHello message
* @param connectionInfo - Optional connection information for fragment handling
* @param enableLogging - Whether to enable detailed debug logging
* @returns The extracted server name or undefined if not found
*/
public static extractSNIWithResumptionSupport(
buffer: Buffer,
connectionInfo?: {
sourceIp?: string;
sourcePort?: number;
destIp?: string;
destPort?: number;
},
enableLogging: boolean = false
): string | undefined {
// First try the standard SNI extraction
const standardSni = this.extractSNI(buffer, enableLogging);
if (standardSni) {
const log = (message: string) => {
if (enableLogging) {
console.log(`[SNI Extraction] Found standard SNI: ${standardSni}`);
console.log(`[SNI Extraction] ${message}`);
}
};
// Check if we need to handle fragmented packets
let processBuffer = buffer;
if (connectionInfo) {
const connectionId = this.createConnectionId(connectionInfo);
const reassembledBuffer = this.handleFragmentedClientHello(
buffer,
connectionId,
enableLogging
);
if (!reassembledBuffer) {
log(`Waiting for more fragments on connection ${connectionId}`);
return undefined; // Need more fragments to complete ClientHello
}
processBuffer = reassembledBuffer;
log(`Using reassembled buffer of length ${processBuffer.length}`);
}
// First try the standard SNI extraction
const standardSni = this.extractSNI(processBuffer, enableLogging);
if (standardSni) {
log(`Found standard SNI: ${standardSni}`);
return standardSni;
}
// Check for TLS 1.3 early data (0-RTT)
const hasEarly = this.hasEarlyData(processBuffer, enableLogging);
if (hasEarly) {
log('TLS 1.3 Early Data detected, using special handling');
// In 0-RTT, Chrome often relies on server remembering the SNI from previous sessions
// We could implement session tracking here if necessary
}
// If standard extraction failed and we have a valid ClientHello,
// this might be a session resumption with non-standard format
if (this.isClientHello(buffer)) {
if (enableLogging) {
console.log('[SNI Extraction] Detected ClientHello without standard SNI, possible session resumption');
}
if (this.isClientHello(processBuffer)) {
log('Detected ClientHello without standard SNI, possible session resumption');
// Try to extract from PSK extension (TLS 1.3 resumption)
const pskSni = this.extractSNIFromPSKExtension(buffer, enableLogging);
const pskSni = this.extractSNIFromPSKExtension(processBuffer, enableLogging);
if (pskSni) {
if (enableLogging) {
console.log(`[SNI Extraction] Extracted SNI from PSK extension: ${pskSni}`);
}
log(`Extracted SNI from PSK extension: ${pskSni}`);
return pskSni;
}
// Could add more browser-specific heuristics here if needed
if (enableLogging) {
console.log('[SNI Extraction] Failed to extract SNI from resumption mechanisms');
// Special handling for Chrome connection racing
// Chrome often opens multiple connections in parallel with different
// characteristics to improve performance
// Here we would look for specific patterns in ClientHello that indicate
// it's part of a connection race
// Detect if this is likely a secondary connection in a race
// by examining the cipher suites and extensions
// This would require session state tracking across connections
log('Failed to extract SNI from resumption mechanisms');
}
return undefined;
}
/**
* Main entry point for SNI extraction that handles all edge cases.
* This should be called for each TLS packet received from a client.
*
* The method uses connection tracking to handle fragmented ClientHello
* messages and various TLS 1.3 behaviors, including Chrome's connection
* racing patterns.
*
* @param buffer - The buffer containing TLS data
* @param connectionInfo - Connection metadata (IPs and ports)
* @param enableLogging - Whether to enable detailed debug logging
* @param cachedSni - Optional cached SNI from previous connections (for racing detection)
* @returns The extracted server name or undefined if not found or more data needed
*/
public static processTlsPacket(
buffer: Buffer,
connectionInfo: {
sourceIp: string;
sourcePort: number;
destIp: string;
destPort: number;
timestamp?: number;
},
enableLogging: boolean = false,
cachedSni?: string
): string | undefined {
const log = (message: string) => {
if (enableLogging) {
console.log(`[TLS Packet] ${message}`);
}
};
// Add timestamp if not provided
if (!connectionInfo.timestamp) {
connectionInfo.timestamp = Date.now();
}
// Check if this is a TLS handshake
if (!this.isTlsHandshake(buffer) && !this.isTlsApplicationData(buffer)) {
log('Not a TLS handshake or application data packet');
return undefined;
}
// Create connection ID for tracking
const connectionId = this.createConnectionId(connectionInfo);
log(`Processing TLS packet for connection ${connectionId}, buffer length: ${buffer.length}`);
// Handle special case: if we already have a cached SNI from a previous
// connection from the same client IP within a short time window,
// this might be a connection racing situation
if (cachedSni && this.isTlsApplicationData(buffer)) {
log(`Using cached SNI from connection racing: ${cachedSni}`);
return cachedSni;
}
// Try to extract SNI with full resumption support and fragment handling
const sni = this.extractSNIWithResumptionSupport(
buffer,
connectionInfo,
enableLogging
);
if (sni) {
log(`Successfully extracted SNI: ${sni}`);
return sni;
}
// If we couldn't extract an SNI, check if this is a valid ClientHello
// If it is, but we couldn't get an SNI, it might be a fragment or
// a connection race situation
if (this.isClientHello(buffer)) {
log('Valid ClientHello detected, but no SNI extracted - might need more data');
}
return undefined;