Add transparent proxy inspection engine with envoy sidecar support

client/internal/engine_tproxy.go

@@ -0,0 +1,571 @@
+package internal
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"net/netip"
+	"net/url"
+	"os"
+	"strconv"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/firewall/uspfilter/forwarder"
+	"github.com/netbirdio/netbird/client/inspect"
+	"github.com/netbirdio/netbird/client/internal/acl/id"
+	"github.com/netbirdio/netbird/shared/management/domain"
+	mgmProto "github.com/netbirdio/netbird/shared/management/proto"
+)
+
+// updateTransparentProxy processes transparent proxy configuration from the network map.
+func (e *Engine) updateTransparentProxy(cfg *mgmProto.TransparentProxyConfig) {
+	if cfg == nil || !cfg.Enabled {
+		if cfg == nil {
+			log.Tracef("inspect: config is nil")
+		} else {
+			log.Tracef("inspect: config disabled")
+		}
+		// Only stop if explicitly disabled. Don't stop on nil config to avoid
+		// a gap during policy edits where management briefly pushes empty config.
+		if cfg != nil && !cfg.Enabled {
+			e.stopTransparentProxy()
+		}
+		return
+	}
+
+	log.Debugf("inspect: config received: enabled=%v mode=%v default_action=%v rules=%d has_ca=%v",
+		cfg.Enabled, cfg.Mode, cfg.DefaultAction, len(cfg.Rules), len(cfg.CaCertPem) > 0)
+
+	// BlockInbound prevents adding TPROXY rules since kernel TPROXY bypasses ACLs.
+	// The userspace forwarder path still works as it operates within the forwarder hook.
+	if e.config.BlockInbound {
+		log.Warnf("inspect: BlockInbound is set, skipping redirect rules (userspace path still active)")
+	}
+
+	proxyConfig, err := toProxyConfig(cfg)
+	if err != nil {
+		log.Errorf("inspect: parse config: %v", err)
+		e.stopTransparentProxy()
+		return
+	}
+
+	// CA priority: local config > management-pushed > auto-generated self-signed.
+	// Local wins over mgmt to prevent compromised management from injecting a CA.
+	e.resolveInspectionCA(&proxyConfig)
+
+	if e.transparentProxy != nil {
+		// Mode change requires full recreate (envoy lifecycle, listener changes).
+		if proxyConfig.Mode != e.transparentProxy.Mode() {
+			log.Infof("inspect: mode changed to %s, recreating engine", proxyConfig.Mode)
+			e.stopTransparentProxy()
+		} else {
+			e.transparentProxy.UpdateConfig(proxyConfig)
+			e.syncTProxyRules(proxyConfig)
+			e.syncUDPInspectionHook()
+			return
+		}
+	}
+
+	if e.wgInterface != nil {
+		proxyConfig.WGNetwork = e.wgInterface.Address().Network
+		proxyConfig.ListenAddr = netip.AddrPortFrom(
+			e.wgInterface.Address().IP.Unmap(),
+			proxyConfig.ListenAddr.Port(),
+		)
+	}
+
+	// Pass local IP checker for SSRF prevention
+	if checker, ok := e.firewall.(inspect.LocalIPChecker); ok {
+		proxyConfig.LocalIPChecker = checker
+	}
+
+	p, err := inspect.New(e.ctx, log.WithField("component", "inspect"), proxyConfig)
+	if err != nil {
+		log.Errorf("inspect: start engine: %v", err)
+		return
+	}
+	e.transparentProxy = p
+
+	e.attachProxyToForwarder(p)
+	e.syncTProxyRules(proxyConfig)
+	e.syncUDPInspectionHook()
+
+	log.Infof("inspect: engine started (mode=%s, rules=%d)", proxyConfig.Mode, len(proxyConfig.Rules))
+}
+
+// stopTransparentProxy shuts down the transparent proxy and removes interception.
+func (e *Engine) stopTransparentProxy() {
+	if e.transparentProxy == nil {
+		return
+	}
+
+	e.attachProxyToForwarder(nil)
+	e.removeTProxyRule()
+	e.removeUDPInspectionHook()
+
+	if err := e.transparentProxy.Close(); err != nil {
+		log.Debugf("inspect: close engine: %v", err)
+	}
+	e.transparentProxy = nil
+
+	log.Info("inspect: engine stopped")
+}
+
+const tproxyRuleID = "tproxy-redirect"
+
+// syncTProxyRules adds a TPROXY rule via the firewall manager to intercept
+// matching traffic on the WG interface and redirect it to the proxy socket.
+func (e *Engine) syncTProxyRules(config inspect.Config) {
+	if e.config.BlockInbound {
+		e.removeTProxyRule()
+		return
+	}
+
+	var listenPort uint16
+	if e.transparentProxy != nil {
+		listenPort = e.transparentProxy.ListenPort()
+	}
+	if listenPort == 0 {
+		e.removeTProxyRule()
+		return
+	}
+
+	if e.firewall == nil {
+		return
+	}
+
+	dstPorts := make([]uint16, len(config.RedirectPorts))
+	copy(dstPorts, config.RedirectPorts)
+
+	log.Debugf("inspect: syncing redirect rules: listen port %d, redirect ports %v, sources %v",
+		listenPort, dstPorts, config.RedirectSources)
+
+	if err := e.firewall.AddTProxyRule(tproxyRuleID, config.RedirectSources, dstPorts, listenPort); err != nil {
+		log.Errorf("inspect: add redirect rule: %v", err)
+		return
+	}
+}
+
+// removeTProxyRule removes the TPROXY redirect rule.
+func (e *Engine) removeTProxyRule() {
+	if e.firewall == nil {
+		return
+	}
+	if err := e.firewall.RemoveTProxyRule(tproxyRuleID); err != nil {
+		log.Debugf("inspect: remove redirect rule: %v", err)
+	}
+}
+
+// syncUDPInspectionHook registers a UDP packet hook on port 443 for QUIC SNI blocking.
+// The hook is called by the USP filter for each UDP packet matching the port,
+// allowing the inspection engine to extract QUIC SNI and block by domain.
+func (e *Engine) syncUDPInspectionHook() {
+	e.removeUDPInspectionHook()
+
+	if e.firewall == nil || e.transparentProxy == nil {
+		return
+	}
+
+	p := e.transparentProxy
+	hookID := e.firewall.AddUDPInspectionHook(443, func(packet []byte) bool {
+		srcIP, dstIP, dstPort, udpPayload, ok := parseUDPPacket(packet)
+		if !ok {
+			return false
+		}
+
+		src := inspect.SourceInfo{IP: srcIP}
+		dst := netip.AddrPortFrom(dstIP, dstPort)
+		action := p.HandleUDPPacket(udpPayload, dst, src)
+		return action == inspect.ActionBlock
+	})
+
+	e.udpInspectionHookID = hookID
+	log.Debugf("inspect: registered UDP inspection hook on port 443 (id=%s)", hookID)
+}
+
+// removeUDPInspectionHook removes the QUIC inspection hook.
+func (e *Engine) removeUDPInspectionHook() {
+	if e.udpInspectionHookID == "" || e.firewall == nil {
+		return
+	}
+	e.firewall.RemoveUDPInspectionHook(e.udpInspectionHookID)
+	e.udpInspectionHookID = ""
+}
+
+// parseUDPPacket extracts source/destination IP, destination port, and UDP
+// payload from a raw IP packet. Supports both IPv4 and IPv6.
+func parseUDPPacket(packet []byte) (srcIP, dstIP netip.Addr, dstPort uint16, payload []byte, ok bool) {
+	if len(packet) < 1 {
+		return srcIP, dstIP, 0, nil, false
+	}
+
+	version := packet[0] >> 4
+
+	var udpOffset int
+	switch version {
+	case 4:
+		if len(packet) < 20 {
+			return srcIP, dstIP, 0, nil, false
+		}
+		ihl := int(packet[0]&0x0f) * 4
+		if len(packet) < ihl+8 {
+			return srcIP, dstIP, 0, nil, false
+		}
+		var srcOK, dstOK bool
+		srcIP, srcOK = netip.AddrFromSlice(packet[12:16])
+		dstIP, dstOK = netip.AddrFromSlice(packet[16:20])
+		if !srcOK || !dstOK {
+			return srcIP, dstIP, 0, nil, false
+		}
+		udpOffset = ihl
+
+	case 6:
+		// IPv6 fixed header is 40 bytes. Next header must be UDP (17).
+		if len(packet) < 48 { // 40 header + 8 UDP
+			return srcIP, dstIP, 0, nil, false
+		}
+		nextHeader := packet[6]
+		if nextHeader != 17 { // not UDP (may have extension headers)
+			return srcIP, dstIP, 0, nil, false
+		}
+		var srcOK, dstOK bool
+		srcIP, srcOK = netip.AddrFromSlice(packet[8:24])
+		dstIP, dstOK = netip.AddrFromSlice(packet[24:40])
+		if !srcOK || !dstOK {
+			return srcIP, dstIP, 0, nil, false
+		}
+		udpOffset = 40
+
+	default:
+		return srcIP, dstIP, 0, nil, false
+	}
+
+	srcIP = srcIP.Unmap()
+	dstIP = dstIP.Unmap()
+	dstPort = uint16(packet[udpOffset+2])<<8 | uint16(packet[udpOffset+3])
+	payload = packet[udpOffset+8:]
+
+	return srcIP, dstIP, dstPort, payload, true
+}
+
+// attachProxyToForwarder sets or clears the proxy on the userspace forwarder.
+func (e *Engine) attachProxyToForwarder(p *inspect.Proxy) {
+	type forwarderGetter interface {
+		GetForwarder() *forwarder.Forwarder
+	}
+
+	if fg, ok := e.firewall.(forwarderGetter); ok {
+		if fwd := fg.GetForwarder(); fwd != nil {
+			fwd.SetProxy(p)
+		}
+	}
+}
+
+// toProxyConfig converts a proto TransparentProxyConfig to the inspect.Config type.
+func toProxyConfig(cfg *mgmProto.TransparentProxyConfig) (inspect.Config, error) {
+	config := inspect.Config{
+		Enabled:       cfg.Enabled,
+		DefaultAction: toProxyAction(cfg.DefaultAction),
+	}
+
+	switch cfg.Mode {
+	case mgmProto.TransparentProxyMode_TP_MODE_ENVOY:
+		config.Mode = inspect.ModeEnvoy
+	case mgmProto.TransparentProxyMode_TP_MODE_EXTERNAL:
+		config.Mode = inspect.ModeExternal
+	default:
+		config.Mode = inspect.ModeBuiltin
+	}
+
+	if cfg.ExternalProxyUrl != "" {
+		u, err := url.Parse(cfg.ExternalProxyUrl)
+		if err != nil {
+			return inspect.Config{}, fmt.Errorf("parse external proxy URL: %w", err)
+		}
+		config.ExternalURL = u
+	}
+
+	for _, s := range cfg.RedirectSources {
+		prefix, err := netip.ParsePrefix(s)
+		if err != nil {
+			return inspect.Config{}, fmt.Errorf("parse redirect source %q: %w", s, err)
+		}
+		config.RedirectSources = append(config.RedirectSources, prefix)
+	}
+
+	for _, p := range cfg.RedirectPorts {
+		config.RedirectPorts = append(config.RedirectPorts, uint16(p))
+	}
+
+	// TPROXY listen port: fixed default, overridable via env var.
+	if config.Mode == inspect.ModeBuiltin {
+		port := uint16(inspect.DefaultTProxyPort)
+		if v := os.Getenv("NB_TPROXY_PORT"); v != "" {
+			if p, err := strconv.ParseUint(v, 10, 16); err == nil {
+				port = uint16(p)
+			} else {
+				log.Warnf("invalid NB_TPROXY_PORT %q, using default %d", v, inspect.DefaultTProxyPort)
+			}
+		}
+		config.ListenAddr = netip.AddrPortFrom(netip.IPv4Unspecified(), port)
+	}
+
+	for _, r := range cfg.Rules {
+		rule, err := toProxyRule(r)
+		if err != nil {
+			return inspect.Config{}, fmt.Errorf("parse rule %q: %w", r.Id, err)
+		}
+		config.Rules = append(config.Rules, rule)
+	}
+
+	if cfg.Icap != nil {
+		icapCfg, err := toICAPConfig(cfg.Icap)
+		if err != nil {
+			return inspect.Config{}, fmt.Errorf("parse ICAP config: %w", err)
+		}
+		config.ICAP = icapCfg
+	}
+
+	if len(cfg.CaCertPem) > 0 && len(cfg.CaKeyPem) > 0 {
+		tlsCfg, err := parseTLSConfig(cfg.CaCertPem, cfg.CaKeyPem)
+		if err != nil {
+			return inspect.Config{}, fmt.Errorf("parse TLS config: %w", err)
+		}
+		config.TLS = tlsCfg
+	}
+
+	if config.Mode == inspect.ModeEnvoy {
+		envCfg := &inspect.EnvoyConfig{
+			BinaryPath: cfg.EnvoyBinaryPath,
+			AdminPort:  uint16(cfg.EnvoyAdminPort),
+		}
+		if cfg.EnvoySnippets != nil {
+			envCfg.Snippets = &inspect.EnvoySnippets{
+				HTTPFilters:    cfg.EnvoySnippets.HttpFilters,
+				NetworkFilters: cfg.EnvoySnippets.NetworkFilters,
+				Clusters:       cfg.EnvoySnippets.Clusters,
+			}
+		}
+		config.Envoy = envCfg
+	}
+
+	return config, nil
+}
+
+func toProxyRule(r *mgmProto.TransparentProxyRule) (inspect.Rule, error) {
+	rule := inspect.Rule{
+		ID:       id.RuleID(r.Id),
+		Action:   toProxyAction(r.Action),
+		Priority: int(r.Priority),
+	}
+
+	for _, d := range r.Domains {
+		dom, err := domain.FromString(d)
+		if err != nil {
+			return inspect.Rule{}, fmt.Errorf("parse domain %q: %w", d, err)
+		}
+		rule.Domains = append(rule.Domains, dom)
+	}
+
+	for _, n := range r.Networks {
+		prefix, err := netip.ParsePrefix(n)
+		if err != nil {
+			return inspect.Rule{}, fmt.Errorf("parse network %q: %w", n, err)
+		}
+		rule.Networks = append(rule.Networks, prefix)
+	}
+
+	for _, p := range r.Ports {
+		rule.Ports = append(rule.Ports, uint16(p))
+	}
+
+	for _, proto := range r.Protocols {
+		rule.Protocols = append(rule.Protocols, toProxyProtoType(proto))
+	}
+
+	rule.Paths = r.Paths
+
+	return rule, nil
+}
+
+func toProxyProtoType(p mgmProto.TransparentProxyProtocol) inspect.ProtoType {
+	switch p {
+	case mgmProto.TransparentProxyProtocol_TP_PROTO_HTTP:
+		return inspect.ProtoHTTP
+	case mgmProto.TransparentProxyProtocol_TP_PROTO_HTTPS:
+		return inspect.ProtoHTTPS
+	case mgmProto.TransparentProxyProtocol_TP_PROTO_H2:
+		return inspect.ProtoH2
+	case mgmProto.TransparentProxyProtocol_TP_PROTO_H3:
+		return inspect.ProtoH3
+	case mgmProto.TransparentProxyProtocol_TP_PROTO_WEBSOCKET:
+		return inspect.ProtoWebSocket
+	case mgmProto.TransparentProxyProtocol_TP_PROTO_OTHER:
+		return inspect.ProtoOther
+	default:
+		return ""
+	}
+}
+
+func toProxyAction(a mgmProto.TransparentProxyAction) inspect.Action {
+	switch a {
+	case mgmProto.TransparentProxyAction_TP_ACTION_BLOCK:
+		return inspect.ActionBlock
+	case mgmProto.TransparentProxyAction_TP_ACTION_INSPECT:
+		return inspect.ActionInspect
+	default:
+		return inspect.ActionAllow
+	}
+}
+
+func toICAPConfig(cfg *mgmProto.TransparentProxyICAPConfig) (*inspect.ICAPConfig, error) {
+	icap := &inspect.ICAPConfig{
+		MaxConnections: int(cfg.MaxConnections),
+	}
+
+	if cfg.ReqmodUrl != "" {
+		u, err := url.Parse(cfg.ReqmodUrl)
+		if err != nil {
+			return nil, fmt.Errorf("parse ICAP reqmod URL: %w", err)
+		}
+		icap.ReqModURL = u
+	}
+
+	if cfg.RespmodUrl != "" {
+		u, err := url.Parse(cfg.RespmodUrl)
+		if err != nil {
+			return nil, fmt.Errorf("parse ICAP respmod URL: %w", err)
+		}
+		icap.RespModURL = u
+	}
+
+	return icap, nil
+}
+
+func parseTLSConfig(certPEM, keyPEM []byte) (*inspect.TLSConfig, error) {
+	block, _ := pem.Decode(certPEM)
+	if block == nil {
+		return nil, fmt.Errorf("decode CA certificate PEM")
+	}
+
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("parse CA certificate: %w", err)
+	}
+
+	keyBlock, _ := pem.Decode(keyPEM)
+	if keyBlock == nil {
+		return nil, fmt.Errorf("decode CA key PEM")
+	}
+
+	key, err := x509.ParseECPrivateKey(keyBlock.Bytes)
+	if err != nil {
+		// Try PKCS8 as fallback
+		pkcs8Key, pkcs8Err := x509.ParsePKCS8PrivateKey(keyBlock.Bytes)
+		if pkcs8Err != nil {
+			return nil, fmt.Errorf("parse CA private key (tried EC and PKCS8): %w", err)
+		}
+		return &inspect.TLSConfig{CA: cert, CAKey: pkcs8Key}, nil
+	}
+
+	return &inspect.TLSConfig{CA: cert, CAKey: key}, nil
+}
+
+// resolveInspectionCA sets the TLS config on the proxy config using priority:
+// 1. Local config file CA (InspectionCACertPath/InspectionCAKeyPath)
+// 2. Management-pushed CA (already parsed in toProxyConfig)
+// 3. Auto-generated self-signed CA (ephemeral, for testing)
+// Local always wins to prevent a compromised management server from injecting a CA.
+func (e *Engine) resolveInspectionCA(config *inspect.Config) {
+	// 1. Local CA from config file or env vars
+	certPath := e.config.InspectionCACertPath
+	keyPath := e.config.InspectionCAKeyPath
+	if certPath == "" {
+		certPath = os.Getenv("NB_INSPECTION_CA_CERT")
+	}
+	if keyPath == "" {
+		keyPath = os.Getenv("NB_INSPECTION_CA_KEY")
+	}
+	if certPath != "" && keyPath != "" {
+		certPEM, err := os.ReadFile(certPath)
+		if err != nil {
+			log.Errorf("read local inspection CA cert %s: %v", certPath, err)
+			return
+		}
+		keyPEM, err := os.ReadFile(keyPath)
+		if err != nil {
+			log.Errorf("read local inspection CA key %s: %v", keyPath, err)
+			return
+		}
+		tlsCfg, err := parseTLSConfig(certPEM, keyPEM)
+		if err != nil {
+			log.Errorf("parse local inspection CA: %v", err)
+			return
+		}
+		log.Infof("inspect: using local CA from %s", certPath)
+		config.TLS = tlsCfg
+		return
+	}
+
+	// 2. Management-pushed CA (already set by toProxyConfig)
+	if config.TLS != nil {
+		log.Infof("inspect: using management-pushed CA")
+		return
+	}
+
+	// 3. Auto-generate self-signed CA for testing / accept-cert UX
+	tlsCfg, err := generateSelfSignedCA()
+	if err != nil {
+		log.Errorf("generate self-signed inspection CA: %v", err)
+		return
+	}
+	log.Infof("inspect: using auto-generated self-signed CA (clients will see certificate warnings)")
+	config.TLS = tlsCfg
+}
+
+// generateSelfSignedCA creates an ephemeral ECDSA P-256 CA certificate.
+// Clients will see certificate warnings but can choose to accept.
+func generateSelfSignedCA() (*inspect.TLSConfig, error) {
+	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return nil, fmt.Errorf("generate CA key: %w", err)
+	}
+
+	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
+	if err != nil {
+		return nil, fmt.Errorf("generate serial: %w", err)
+	}
+
+	template := &x509.Certificate{
+		SerialNumber: serial,
+		Subject: pkix.Name{
+			Organization: []string{"NetBird Transparent Proxy"},
+			CommonName:   "NetBird Inspection CA (auto-generated)",
+		},
+		NotBefore:             time.Now().Add(-1 * time.Hour),
+		NotAfter:              time.Now().Add(365 * 24 * time.Hour),
+		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+		MaxPathLen:            0,
+	}
+
+	certDER, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
+	if err != nil {
+		return nil, fmt.Errorf("create CA certificate: %w", err)
+	}
+
+	cert, err := x509.ParseCertificate(certDER)
+	if err != nil {
+		return nil, fmt.Errorf("parse generated CA certificate: %w", err)
+	}
+
+	return &inspect.TLSConfig{CA: cert, CAKey: key}, nil
+}