TCP Fingerprinting

tcp.go

package fingerprint

import (
	"context"
	"fmt"
	"net"
	"syscall"
	"time"
)

// TCPFingerprinter handles TCP-level fingerprinting
type TCPFingerprinter struct {
	profile *TCPProfile
}

// CustomDialer provides TCP fingerprinting capabilities
type CustomDialer struct {
	tcpProfile *TCPProfile
	baseDialer *net.Dialer
}

func NewTCPFingerprinter(profile *TCPProfile) *TCPFingerprinter {
	return &TCPFingerprinter{
		profile: profile,
	}
}

func NewCustomDialer(profile *TCPProfile) *CustomDialer {
	return &CustomDialer{
		tcpProfile: profile,
		baseDialer: &net.Dialer{
			Timeout:   30 * time.Second,
			KeepAlive: 30 * time.Second,
		},
	}
}

func (cd *CustomDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
	// Use base dialer to establish connection
	conn, err := cd.baseDialer.DialContext(ctx, network, address)
	if err != nil {
		return nil, err
	}

	// Apply TCP fingerprinting options
	if tcpConn, ok := conn.(*net.TCPConn); ok {
		if err := cd.applyTCPOptions(tcpConn); err != nil {
			conn.Close()
			return nil, err
		}
	}

	return conn, nil
}

func (cd *CustomDialer) applyTCPOptions(conn *net.TCPConn) error {
	// Get raw connection for socket options
	rawConn, err := conn.SyscallConn()
	if err != nil {
		return err
	}

	var sockErr error
	err = rawConn.Control(func(fd uintptr) {
		sockErr = cd.setSocketOptions(int(fd))
	})
	if err != nil {
		return err
	}

	return sockErr
}

func (cd *CustomDialer) setSocketOptions(fd int) error {
	// Set TCP window size
	if cd.tcpProfile.WindowSize > 0 {
		if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUF, cd.tcpProfile.WindowSize); err != nil {
			return err
		}
		if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF, cd.tcpProfile.WindowSize); err != nil {
			return err
		}
	}

	// Set MSS (Maximum Segment Size)
	if cd.tcpProfile.MSS > 0 {
		// Note: MSS setting is platform-specific and may require different approaches
		// This is a simplified example
		if err := syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_MAXSEG, cd.tcpProfile.MSS); err != nil {
			// MSS setting might not be available on all platforms
			// Continue without error in production
		}
	}

	// Set TCP_NODELAY (disable Nagle's algorithm)
	if err := syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_NODELAY, 1); err != nil {
		return err
	}

	// Set SO_KEEPALIVE
	if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_KEEPALIVE, 1); err != nil {
		return err
	}

	// Platform-specific TCP options would go here
	// For example, on Linux:
	// - TCP_WINDOW_CLAMP
	// - TCP_USER_TIMEOUT
	// - TCP_TIMESTAMP
	// - TCP_SACK

	return nil
}

// Platform-specific implementations would be in separate files:
// tcp_linux.go, tcp_windows.go, tcp_darwin.go

// LinuxTCPOptions applies Linux-specific TCP options
func (cd *CustomDialer) applyLinuxTCPOptions(fd int) error {
	// TCP Window Scaling
	if cd.tcpProfile.WindowScaling {
		// This would use Linux-specific socket options
		// syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, TCP_WINDOW_CLAMP, value)
	}

	// TCP Timestamps
	if cd.tcpProfile.Timestamps {
		// syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, TCP_TIMESTAMP, 1)
	}

	// TCP Selective Acknowledgment
	if cd.tcpProfile.SelectiveAck {
		// syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, TCP_SACK_ENABLE, 1)
	}

	return nil
}

// WindowsTCPOptions applies Windows-specific TCP options
func (cd *CustomDialer) applyWindowsTCPOptions(fd int) error {
	// Windows has different socket options and registry settings
	// that would need to be configured differently

	return nil
}

// DarwinTCPOptions applies macOS-specific TCP options
func (cd *CustomDialer) applyDarwinTCPOptions(fd int) error {
	// macOS/Darwin specific TCP stack options

	return nil
}

// TCPStackDetection provides methods to detect and mimic different TCP stacks
type TCPStackDetection struct {
	knownStacks map[string]*TCPSignature
}

type TCPSignature struct {
	Name          string
	WindowSize    int
	MSS           int
	TTL           int
	Options       []TCPOption
	WindowScaling bool
	Timestamps    bool
	SelectiveAck  bool
	ECN           bool
}

type TCPOption struct {
	Kind   uint8
	Length uint8
	Data   []byte
}

func NewTCPStackDetection() *TCPStackDetection {
	tsd := &TCPStackDetection{
		knownStacks: make(map[string]*TCPSignature),
	}

	tsd.loadKnownSignatures()
	return tsd
}

func (tsd *TCPStackDetection) loadKnownSignatures() {
	// Windows 10/11 signature
	tsd.knownStacks["windows10"] = &TCPSignature{
		Name:          "Windows 10/11",
		WindowSize:    65535,
		MSS:           1460,
		TTL:           128,
		WindowScaling: true,
		Timestamps:    true,
		SelectiveAck:  true,
		ECN:           false,
	}

	// Linux signature
	tsd.knownStacks["linux"] = &TCPSignature{
		Name:          "Linux",
		WindowSize:    29200,
		MSS:           1460,
		TTL:           64,
		WindowScaling: true,
		Timestamps:    true,
		SelectiveAck:  true,
		ECN:           true,
	}

	// macOS signature
	tsd.knownStacks["macos"] = &TCPSignature{
		Name:          "macOS",
		WindowSize:    65535,
		MSS:           1460,
		TTL:           64,
		WindowScaling: true,
		Timestamps:    true,
		SelectiveAck:  true,
		ECN:           false,
	}

	// FreeBSD signature
	tsd.knownStacks["freebsd"] = &TCPSignature{
		Name:          "FreeBSD",
		WindowSize:    65535,
		MSS:           1460,
		TTL:           64,
		WindowScaling: true,
		Timestamps:    true,
		SelectiveAck:  true,
		ECN:           false,
	}
}

func (tsd *TCPStackDetection) GetSignature(stackName string) *TCPSignature {
	if sig, exists := tsd.knownStacks[stackName]; exists {
		return sig
	}
	return tsd.knownStacks["linux"] // Default
}

func (tsd *TCPStackDetection) CreateProfileFromSignature(sig *TCPSignature) *TCPProfile {
	return &TCPProfile{
		Name:          sig.Name,
		WindowSize:    sig.WindowSize,
		MSS:           sig.MSS,
		TTL:           sig.TTL,
		WindowScaling: sig.WindowScaling,
		Timestamps:    sig.Timestamps,
		SelectiveAck:  sig.SelectiveAck,
	}
}

// Advanced TCP fingerprinting techniques
type AdvancedTCPFingerprinter struct {
	stackDetection *TCPStackDetection
	evasionMode    bool
}

func NewAdvancedTCPFingerprinter() *AdvancedTCPFingerprinter {
	return &AdvancedTCPFingerprinter{
		stackDetection: NewTCPStackDetection(),
		evasionMode:    false,
	}
}

func (atf *AdvancedTCPFingerprinter) SetEvasionMode(enabled bool) {
	atf.evasionMode = enabled
}

func (atf *AdvancedTCPFingerprinter) GetRandomProfile() *TCPProfile {
	stacks := []string{"windows10", "linux", "macos", "freebsd"}
	randomStack := stacks[time.Now().UnixNano()%int64(len(stacks))]

	sig := atf.stackDetection.GetSignature(randomStack)
	profile := atf.stackDetection.CreateProfileFromSignature(sig)

	// Apply evasion techniques if enabled
	if atf.evasionMode {
		atf.applyEvasionTechniques(profile)
	}

	return profile
}

func (atf *AdvancedTCPFingerprinter) applyEvasionTechniques(profile *TCPProfile) {
	// Randomize window size within realistic ranges
	baseWindow := profile.WindowSize
	variation := baseWindow / 10 // ±10% variation
	profile.WindowSize = baseWindow + int(time.Now().UnixNano()%int64(variation*2)) - variation

	// Randomize MSS slightly
	if profile.MSS > 0 {
		profile.MSS += int(time.Now().UnixNano()%40) - 20 // ±20 bytes
		if profile.MSS < 536 {
			profile.MSS = 536 // Minimum MSS
		}
		if profile.MSS > 1460 {
			profile.MSS = 1460 // Standard Ethernet MSS
		}
	}

	// Occasionally disable some features for evasion
	if time.Now().UnixNano()%10 == 0 {
		profile.WindowScaling = false
	}

	if time.Now().UnixNano()%8 == 0 {
		profile.Timestamps = false
	}

	if time.Now().UnixNano()%12 == 0 {
		profile.SelectiveAck = false
	}
}

// TCPFingerprintMatcher helps identify and match TCP fingerprints
type TCPFingerprintMatcher struct {
	database map[string]*TCPSignature
}

func NewTCPFingerprintMatcher() *TCPFingerprintMatcher {
	return &TCPFingerprintMatcher{
		database: make(map[string]*TCPSignature),
	}
}

func (tfm *TCPFingerprintMatcher) AnalyzePacket(windowSize, mss, ttl int, options []TCPOption) string {
	// Simple fingerprint matching based on common patterns

	// Windows detection
	if ttl == 128 && windowSize == 65535 {
		if mss == 1460 {
			return "Windows 10/11"
		}
		return "Windows (version unknown)"
	}

	// Linux detection
	if ttl == 64 && windowSize > 25000 && windowSize < 35000 {
		return "Linux"
	}

	// macOS detection
	if ttl == 64 && windowSize == 65535 && mss == 1460 {
		return "macOS"
	}

	// FreeBSD detection
	if ttl == 64 && windowSize == 65535 {
		return "FreeBSD"
	}

	return "Unknown"
}

// Connection pool with TCP fingerprinting
type FingerprintedConnPool struct {
	pools  map[string]*ConnectionPool
	dialer map[string]*CustomDialer
}

type ConnectionPool struct {
	connections chan net.Conn
	maxConns    int
	profile     *TCPProfile
}

func NewFingerprintedConnPool() *FingerprintedConnPool {
	return &FingerprintedConnPool{
		pools:  make(map[string]*ConnectionPool),
		dialer: make(map[string]*CustomDialer),
	}
}

func (fcp *FingerprintedConnPool) GetConnection(profileName string, address string) (net.Conn, error) {
	pool, exists := fcp.pools[profileName]
	if !exists {
		return nil, fmt.Errorf("profile %s not found", profileName)
	}

	// Try to get existing connection from pool
	select {
	case conn := <-pool.connections:
		// Test if connection is still alive
		if fcp.isConnAlive(conn) {
			return conn, nil
		}
		conn.Close()
	default:
		// No available connections, create new one
	}

	// Create new connection with fingerprinting
	dialer := fcp.dialer[profileName]
	if dialer == nil {
		return nil, fmt.Errorf("dialer for profile %s not found", profileName)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	return dialer.DialContext(ctx, "tcp", address)
}

func (fcp *FingerprintedConnPool) ReturnConnection(profileName string, conn net.Conn) {
	pool, exists := fcp.pools[profileName]
	if !exists || !fcp.isConnAlive(conn) {
		conn.Close()
		return
	}

	select {
	case pool.connections <- conn:
		// Successfully returned to pool
	default:
		// Pool is full, close connection
		conn.Close()
	}
}

func (fcp *FingerprintedConnPool) isConnAlive(conn net.Conn) bool {
	// Simple connection liveness check
	conn.SetReadDeadline(time.Now().Add(time.Millisecond))
	var buf [1]byte
	_, err := conn.Read(buf[:])
	conn.SetReadDeadline(time.Time{})

	// If we get a timeout, connection is likely alive
	if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
		return true
	}

	return false
}

func (fcp *FingerprintedConnPool) AddProfile(name string, profile *TCPProfile, maxConns int) {
	pool := &ConnectionPool{
		connections: make(chan net.Conn, maxConns),
		maxConns:    maxConns,
		profile:     profile,
	}

	fcp.pools[name] = pool
	fcp.dialer[name] = NewCustomDialer(profile)
}

// Network interface and routing manipulation for advanced evasion
type NetworkEvasion struct {
	interfaces []NetworkInterface
}

type NetworkInterface struct {
	Name    string
	IP      net.IP
	Gateway net.IP
	MTU     int
}

func NewNetworkEvasion() *NetworkEvasion {
	ne := &NetworkEvasion{}
	ne.discoverInterfaces()
	return ne
}

func (ne *NetworkEvasion) discoverInterfaces() {
	interfaces, err := net.Interfaces()
	if err != nil {
		return
	}

	for _, iface := range interfaces {
		if iface.Flags&net.FlagUp == 0 || iface.Flags&net.FlagLoopback != 0 {
			continue
		}

		addrs, err := iface.Addrs()
		if err != nil {
			continue
		}

		for _, addr := range addrs {
			if ipnet, ok := addr.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
				if ipnet.IP.To4() != nil {
					netIface := NetworkInterface{
						Name: iface.Name,
						IP:   ipnet.IP,
						MTU:  iface.MTU,
					}
					ne.interfaces = append(ne.interfaces, netIface)
				}
			}
		}
	}
}

func (ne *NetworkEvasion) SelectRandomInterface() *NetworkInterface {
	if len(ne.interfaces) == 0 {
		return nil
	}

	index := time.Now().UnixNano() % int64(len(ne.interfaces))
	return &ne.interfaces[index]
}

// IP fragmentation and packet manipulation for evasion
type PacketManipulator struct {
	fragmentationEnabled bool
	maxFragmentSize      int
}

func NewPacketManipulator() *PacketManipulator {
	return &PacketManipulator{
		fragmentationEnabled: false,
		maxFragmentSize:      1400,
	}
}

func (pm *PacketManipulator) EnableFragmentation(maxSize int) {
	pm.fragmentationEnabled = true
	pm.maxFragmentSize = maxSize
}

func (pm *PacketManipulator) DisableFragmentation() {
	pm.fragmentationEnabled = false
}

// TCP sequence number randomization
type SequenceRandomizer struct {
	baseSequence uint32
	increment    uint32
}

func NewSequenceRandomizer() *SequenceRandomizer {
	now := time.Now().UnixNano()
	return &SequenceRandomizer{
		baseSequence: uint32(now),
		increment:    uint32(now % 10000),
	}
}

func (sr *SequenceRandomizer) NextSequence() uint32 {
	sr.baseSequence += sr.increment
	return sr.baseSequence
}

func (sr *SequenceRandomizer) RandomizeIncrement() {
	sr.increment = uint32(time.Now().UnixNano() % 10000)
}

// Utility functions for TCP fingerprinting
func CalculateChecksum(data []byte) uint16 {
	var sum uint32

	// Process pairs of bytes
	for i := 0; i < len(data)-1; i += 2 {
		sum += uint32(data[i])<<8 + uint32(data[i+1])
	}

	// Handle odd byte
	if len(data)%2 == 1 {
		sum += uint32(data[len(data)-1]) << 8
	}

	// Add carry
	for (sum >> 16) > 0 {
		sum = (sum & 0xFFFF) + (sum >> 16)
	}

	return ^uint16(sum)
}

func GenerateRandomTCPOptions() []TCPOption {
	options := []TCPOption{}

	// MSS option
	options = append(options, TCPOption{
		Kind:   2,
		Length: 4,
		Data:   []byte{0x05, 0xB4}, // 1460 bytes
	})

	// Window scale option
	options = append(options, TCPOption{
		Kind:   3,
		Length: 3,
		Data:   []byte{0x08}, // Scale factor 8
	})

	// SACK permitted option
	options = append(options, TCPOption{
		Kind:   4,
		Length: 2,
		Data:   []byte{},
	})

	// Timestamp option
	timestamp := uint32(time.Now().Unix())
	options = append(options, TCPOption{
		Kind:   8,
		Length: 10,
		Data: []byte{
			byte(timestamp >> 24),
			byte(timestamp >> 16),
			byte(timestamp >> 8),
			byte(timestamp),
			0, 0, 0, 0, // Echo timestamp (0 for SYN)
		},
	})

	return options
}