Adding half-handshake tls detect

net/net.go

@@ -1,4 +1,4 @@
-package netutil
+package net
 
 import (
 	"errors"

net/net_test.go

@@ -1,4 +1,4 @@
-package netutil
+package net
 
 import (
 	"testing"

net/tls.go

@@ -0,0 +1,155 @@
+package net
+
+import (
+	"crypto/rand"
+	"net"
+	"os"
+	"time"
+)
+
+// DetectTLS attempts to detect TLS on a connection by sending a ClientHello
+// and checking for early TLS fingerprints without performing a full handshake.
+//
+// It returns true if TLS is detected, false otherwise.
+//
+// The function uses the following steps:
+// 1. Generate a random 32-byte value for the ClientHello.
+// 2. Create a ServerNameIndication (SNI) extension for the hostname.
+// 3. Create a ClientHello message with the random value and the SNI extension.
+// 4. Send the ClientHello message to the server.
+// 5. Read the response from the server.
+// 6. Check if the response contains a ServerHello or tls alert message.
+// 7. If the response contains a ServerHello or tls alert message, return true.
+// 8. Otherwise, return false.
+func DetectTLS(conn net.Conn, host string, timeout time.Duration) bool {
+	hostname := ""
+	if host != "" {
+		if ip := net.ParseIP(host); ip == nil {
+			hostname = host
+		}
+	}
+
+	var sniExtension []byte
+	var extensions []byte
+	var extensionsLength int
+
+	if hostname != "" {
+		hostnameBytes := []byte(hostname)
+		sniListLength := 1 + 2 + len(hostnameBytes)
+		sniLength := 2 + sniListLength
+		sniExtension = make([]byte, 4+sniLength)
+		sniExtension[0] = 0x00 // extension type: server_name
+		sniExtension[1] = 0x00
+		sniExtension[2] = byte(sniLength >> 8) // extension length
+		sniExtension[3] = byte(sniLength)
+		sniExtension[4] = byte(sniListLength >> 8) // server_name_list length
+		sniExtension[5] = byte(sniListLength)
+		sniExtension[6] = 0x00                          // name_type: host_name
+		sniExtension[7] = byte(len(hostnameBytes) >> 8) // hostname length
+		sniExtension[8] = byte(len(hostnameBytes))
+		copy(sniExtension[9:], hostnameBytes)
+
+		extensions = sniExtension
+		extensionsLength = len(extensions)
+	}
+
+	clientHelloBodyLength := 2 + 32 + 1 + 2 + 2 + 1 + 1 + 2 + extensionsLength
+	handshakeLength := 4 + clientHelloBodyLength
+	recordLength := handshakeLength
+	clientHello := make([]byte, 5+handshakeLength)
+	offset := 0
+
+	// TLS record header
+	clientHello[offset] = 0x16                      // content type: Handshake
+	clientHello[offset+1] = 0x03                    // version: TLS 1.0 (major)
+	clientHello[offset+2] = 0x01                    // version: TLS 1.0 (minor)
+	clientHello[offset+3] = byte(recordLength >> 8) // length (high)
+	clientHello[offset+4] = byte(recordLength)      // length (low)
+	offset += 5
+
+	// Handshake header
+	clientHello[offset] = 0x01                                // handshake type: ClientHello
+	clientHello[offset+1] = byte(clientHelloBodyLength >> 16) // length (high)
+	clientHello[offset+2] = byte(clientHelloBodyLength >> 8)  // length (mid)
+	clientHello[offset+3] = byte(clientHelloBodyLength)       // length (low)
+	offset += 4
+
+	// ClientHello message
+	clientHello[offset] = 0x03   // version: TLS 1.2 (major)
+	clientHello[offset+1] = 0x03 // version: TLS 1.2 (minor)
+	offset += 2
+	random := make([]byte, 32)
+	if _, err := rand.Read(random); err != nil {
+		return false
+	}
+	copy(clientHello[offset:], random) // random (32 bytes)
+	offset += 32
+	clientHello[offset] = 0x00 // session_id length
+	offset++
+	clientHello[offset] = 0x00   // cipher_suites length (high)
+	clientHello[offset+1] = 0x02 // cipher_suites length (low)
+	offset += 2
+	clientHello[offset] = 0x00   // cipher_suite: TLS_RSA_WITH_AES_128_CBC_SHA (high)
+	clientHello[offset+1] = 0x2f // cipher_suite (low)
+	offset += 2
+	clientHello[offset] = 0x01 // compression_methods length
+	offset++
+	clientHello[offset] = 0x00 // compression_method: null
+	offset++
+	clientHello[offset] = byte(extensionsLength >> 8) // extensions length (high)
+	clientHello[offset+1] = byte(extensionsLength)    // extensions length (low)
+	offset += 2
+	if extensionsLength > 0 {
+		copy(clientHello[offset:], extensions)
+		offset += extensionsLength
+	}
+
+	actualRecordLength := offset - 5
+	clientHello[3] = byte(actualRecordLength >> 8)
+	clientHello[4] = byte(actualRecordLength)
+
+	if err := conn.SetWriteDeadline(time.Now().Add(timeout)); err != nil {
+		return false
+	}
+
+	if _, err := conn.Write(clientHello[:offset]); err != nil {
+		return false
+	}
+	readTimeout := 2 * time.Second
+	if timeout < readTimeout {
+		readTimeout = timeout
+	}
+	if err := conn.SetReadDeadline(time.Now().Add(readTimeout)); err != nil {
+		return false
+	}
+
+	buffer := make([]byte, 1024)
+	n, err := conn.Read(buffer)
+	if err != nil && !os.IsTimeout(err) {
+		return false
+	}
+
+	if n < 5 {
+		return false
+	}
+
+	// check content type (0x15=Alert, 0x16=Handshake)
+	contentType := buffer[0]
+	if contentType != 0x15 && contentType != 0x16 {
+		return false
+	}
+
+	// check TLS version (major must be 0x03)
+	if buffer[1] != 0x03 {
+		return false
+	}
+
+	// if handshake, check for ServerHello (0x02)
+	if contentType == 0x16 && n >= 6 {
+		if buffer[5] == 0x02 {
+			return true
+		}
+	}
+
+	return true
+}