Add TLS record fragmentation

bin/gt.js

@@ -76,6 +76,12 @@ const { argv } = yargs
 		default: true,
 	})
 
+	.option('tls-record-fragmentation', {
+		type: 'boolean',
+		describe: 'enable TLS record fragmentation',
+		default: false
+	})
+
 	.example('$0')
 	.example('$0 --ip 127.0.0.1 --port 8000')
 	.example('$0 --dns-server https://doh.securedns.eu/dns-query')
@@ -128,6 +134,7 @@ async function main() {
 			port: argv['dns-port']
 		},
 		source: 'CLI',
+		'tlsRecordFragmentation': argv['tls-record-fragmentation']
 	});
 
 	const exitTrap = async () => {

src/handlers/https.js

@@ -43,7 +43,7 @@ export default async function handleHTTPS(clientSocket, firstChunk, proxy) {
 	// -- clientSocket --
 
 	clientSocket.once('data', clientHello => {
-		const chunks = bufferToChunks(clientHello, proxy.config.clientHelloMTU);
+		const chunks = bufferToChunks(clientHello, proxy.config.clientHelloMTU, proxy.config.tlsRecordFragmentation);
 		for (const chunk of chunks) {
 			logger.debug(`[HTTPS HELLO] ${url.host} (length: ${chunk.length})`);
 			tryWrite(serverSocket, chunk, close);

src/utils/buffer.js

@@ -1,4 +1,5 @@
-export function bufferToChunks(buffer, chunkSize) {
+export function bufferToChunks(buffer, chunkSize, recordFragmentation) {
+	if(recordFragmentation) buffer=tlsRecordFragmentation(buffer, chunkSize)
 	const result = [];
 	const len = buffer.length;
 	let i = 0;
@@ -9,3 +10,26 @@ export function bufferToChunks(buffer, chunkSize) {
 
 	return result;
 }
+/**
+ * @param {Buffer} buffer
+ * @param {number} chunkSize
+ */
+function tlsRecordFragmentation(buffer, chunkSize) {
+	const list = []
+	const header = buffer.subarray(0,3)
+	const fullRecord = buffer.subarray(5)
+	const len = fullRecord.length
+	let i = 0
+
+	while (i < len) {
+		const record = fullRecord.subarray(i, i+chunkSize)
+		const recordLength = record.length
+		const buf = Buffer.alloc(recordLength+5)
+		header.copy(buf)
+		buf.writeUInt16BE(recordLength,3)
+		record.copy(buf,5)
+		list.push(buf)
+		i+=chunkSize
+	}
+	return Buffer.concat(list)
+}