[relay] only trust X-Real-Ip headers from configured trusted proxies (#6833)

The WS listener unconditionally trusted X-Real-Ip/X-Real-Port headers,
letting any client forge the source address the relay logs. Gate header
trust behind a trusted-proxy allowlist; ignore the headers unless the
immediate peer matches a configured prefix. Defaults to never trusting
the headers when the allowlist is empty.

## Describe your changes

## Issue ticket number and link

## Stack

<!-- branch-stack -->

### Checklist
- [x] Is it a bug fix
- [ ] Is a typo/documentation fix
- [ ] Is a feature enhancement
- [ ] It is a refactor
- [ ] Created tests that fail without the change (if possible)
- [ ] This change does **not** modify the public API, gRPC protocols,
functionality behavior, CLI / service flags, or introduce a new feature
— **OR** I have discussed it with the NetBird team beforehand (link the
issue / Slack thread in the description). See
[CONTRIBUTING.md](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTING.md#discuss-changes-with-the-netbird-team-first).

> By submitting this pull request, you confirm that you have read and
agree to the terms of the [Contributor License
Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md).

## Documentation
Select exactly one:

- [ ] I added/updated documentation for this change
- [x] Documentation is **not needed** for this change (explain why)

### Docs PR URL (required if "docs added" is checked)
Paste the PR link from https://github.com/netbirdio/docs here:

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added `--trusted-proxies` to configure a comma-separated allowlist of
trusted upstream proxy IPs/CIDRs.
* **Behavior Changes**
* Relay WebSocket now uses `X-Real-Ip` / `X-Real-Port` only when the
immediate peer is from the configured trusted set; otherwise it falls
back to the direct remote address.
* Proxy client IP resolution is now consistent and honors
`X-Forwarded-For` only through trusted hops.
* **Operational**
  * Invalid `--trusted-proxies` values fail fast on startup.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

proxy/cmd/proxy/cmd/root.go

@@ -18,6 +18,7 @@ import (
 	"github.com/netbirdio/netbird/client/embed"
 	"github.com/netbirdio/netbird/proxy"
 	nbacme "github.com/netbirdio/netbird/proxy/internal/acme"
+	"github.com/netbirdio/netbird/trustedproxy"
 	"github.com/netbirdio/netbird/util"
 )
 
@@ -209,7 +210,7 @@ func runServer(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("invalid domain value %q: %w", proxyDomain, err)
 	}
 
-	parsedTrustedProxies, err := proxy.ParseTrustedProxies(trustedProxies)
+	parsedTrustedProxies, err := trustedproxy.Parse(trustedProxies)
 	if err != nil {
 		return fmt.Errorf("invalid --trusted-proxies: %w", err)
 	}

proxy/internal/accesslog/logger.go

@@ -16,6 +16,7 @@ import (
 	"github.com/netbirdio/netbird/proxy/auth"
 	"github.com/netbirdio/netbird/proxy/internal/types"
 	"github.com/netbirdio/netbird/shared/management/proto"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 const (
@@ -66,7 +67,7 @@ type denyBucket struct {
 type Logger struct {
 	client         gRPCClient
 	logger         *log.Logger
-	trustedProxies []netip.Prefix
+	trustedProxies *trustedproxy.List
 
 	usageMux    sync.Mutex
 	domainUsage map[string]*domainUsage
@@ -82,7 +83,7 @@ type Logger struct {
 // NewLogger creates a new access log Logger. The trustedProxies parameter
 // configures which upstream proxy IP ranges are trusted for extracting
 // the real client IP from X-Forwarded-For headers.
-func NewLogger(client gRPCClient, logger *log.Logger, trustedProxies []netip.Prefix) *Logger {
+func NewLogger(client gRPCClient, logger *log.Logger, trustedProxies *trustedproxy.List) *Logger {
 	if logger == nil {
 		logger = log.StandardLogger()
 	}

proxy/internal/accesslog/requestip.go

@@ -4,13 +4,13 @@ import (
 	"net/http"
 	"net/netip"
 
-	"github.com/netbirdio/netbird/proxy/internal/proxy"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 // extractSourceIP resolves the real client IP from the request using trusted
 // proxy configuration. When trustedProxies is non-empty and the direct
 // connection is from a trusted source, it walks X-Forwarded-For right-to-left
 // skipping trusted IPs. Otherwise it returns RemoteAddr directly.
-func extractSourceIP(r *http.Request, trustedProxies []netip.Prefix) netip.Addr {
+func extractSourceIP(r *http.Request, trustedProxies *trustedproxy.List) netip.Addr {
-	return proxy.ResolveClientIP(r.RemoteAddr, r.Header.Get("X-Forwarded-For"), trustedProxies)
+	return trustedProxies.ResolveClientIP(r.RemoteAddr, r.Header.Get("X-Forwarded-For"))
 }

proxy/internal/proxy/reverseproxy.go

@@ -22,6 +22,7 @@ import (
 	"github.com/netbirdio/netbird/proxy/internal/roundtrip"
 	"github.com/netbirdio/netbird/proxy/internal/types"
 	"github.com/netbirdio/netbird/proxy/web"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 type ReverseProxy struct {
@@ -29,10 +30,10 @@ type ReverseProxy struct {
 	// forwardedProto overrides the X-Forwarded-Proto header value.
 	// Valid values: "auto" (detect from TLS), "http", "https".
 	forwardedProto string
-	// trustedProxies is a list of IP prefixes for trusted upstream proxies.
+	// trustedProxies is the set of trusted upstream proxies. When the direct
-	// When the direct connection comes from a trusted proxy, forwarding
+	// connection comes from a trusted proxy, forwarding headers are preserved
-	// headers are preserved and appended to instead of being stripped.
+	// and appended to instead of being stripped.
-	trustedProxies []netip.Prefix
+	trustedProxies *trustedproxy.List
 	mappingsMux    sync.RWMutex
 	mappings       map[string]Mapping
 	logger         *log.Logger
@@ -63,7 +64,7 @@ func WithMiddlewareManager(m *middleware.Manager) Option {
 // between requested URLs and targets.
 // The internal mappings can be modified using the AddMapping
 // and RemoveMapping functions.
-func NewReverseProxy(transport http.RoundTripper, forwardedProto string, trustedProxies []netip.Prefix, logger *log.Logger, opts ...Option) *ReverseProxy {
+func NewReverseProxy(transport http.RoundTripper, forwardedProto string, trustedProxies *trustedproxy.List, logger *log.Logger, opts ...Option) *ReverseProxy {
 	if logger == nil {
 		logger = log.StandardLogger()
 	}
@@ -527,7 +528,7 @@ func (p *ReverseProxy) isSelfTargetLoop(r *http.Request, target *url.URL) bool {
 	if !types.IsOverlayOrigin(r.Context()) {
 		return false
 	}
-	srcIP := extractHostIP(r.RemoteAddr)
+	srcIP := trustedproxy.ExtractHostIP(r.RemoteAddr)
 	if !srcIP.IsValid() {
 		return false
 	}
@@ -578,9 +579,9 @@ func (p *ReverseProxy) rewriteFunc(target *url.URL, matchedPath string, passHost
 
 		stampNetBirdIdentity(r)
 
-		clientIP := extractHostIP(r.In.RemoteAddr)
+		clientIP := trustedproxy.ExtractHostIP(r.In.RemoteAddr)
 
-		if isTrustedAddr(clientIP, p.trustedProxies) {
+		if p.trustedProxies.Contains(clientIP) {
 			p.setTrustedForwardingHeaders(r, clientIP)
 		} else {
 			p.setUntrustedForwardingHeaders(r, clientIP)
@@ -664,7 +665,7 @@ func (p *ReverseProxy) setTrustedForwardingHeaders(r *httputil.ProxyRequest, cli
 	if realIP := r.In.Header.Get("X-Real-IP"); realIP != "" {
 		r.Out.Header.Set("X-Real-IP", realIP)
 	} else {
-		resolved := ResolveClientIP(r.In.RemoteAddr, r.In.Header.Get("X-Forwarded-For"), p.trustedProxies)
+		resolved := p.trustedProxies.ResolveClientIP(r.In.RemoteAddr, r.In.Header.Get("X-Forwarded-For"))
 		r.Out.Header.Set("X-Real-IP", resolved.String())
 	}
 

proxy/internal/proxy/reverseproxy_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/netbirdio/netbird/proxy/internal/roundtrip"
 	"github.com/netbirdio/netbird/proxy/internal/types"
 	"github.com/netbirdio/netbird/proxy/web"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 func TestRewriteFunc_HostRewriting(t *testing.T) {
@@ -302,7 +303,7 @@ func TestExtractHostIP(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			assert.Equal(t, tt.expected, extractHostIP(tt.remoteAddr))
+			assert.Equal(t, tt.expected, trustedproxy.ExtractHostIP(tt.remoteAddr))
 		})
 	}
 }
@@ -330,7 +331,7 @@ func TestExtractForwardedPort(t *testing.T) {
 
 func TestRewriteFunc_TrustedProxy(t *testing.T) {
 	target, _ := url.Parse("http://backend.internal:8080")
-	trusted := []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}
+	trusted := trustedproxy.FromPrefixes([]netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")})
 
 	t.Run("appends to X-Forwarded-For", func(t *testing.T) {
 		p := &ReverseProxy{forwardedProto: "auto", trustedProxies: trusted}

proxy/internal/proxy/trustedproxy.go

@@ -1,81 +0,0 @@
-package proxy
-
-import (
-	"net/netip"
-	"strings"
-)
-
-// IsTrustedProxy checks if the given IP string falls within any of the trusted prefixes.
-func IsTrustedProxy(ipStr string, trusted []netip.Prefix) bool {
-	addr, err := netip.ParseAddr(ipStr)
-	if err != nil || len(trusted) == 0 {
-		return false
-	}
-	return isTrustedAddr(addr.Unmap(), trusted)
-}
-
-// ResolveClientIP extracts the real client IP from X-Forwarded-For using the trusted proxy list.
-// It walks the XFF chain right-to-left, skipping IPs that match trusted prefixes.
-// The first untrusted IP is the real client.
-//
-// If the trusted list is empty or remoteAddr is not trusted, it returns the
-// remoteAddr IP directly (ignoring any forwarding headers).
-func ResolveClientIP(remoteAddr, xff string, trusted []netip.Prefix) netip.Addr {
-	remoteIP := extractHostIP(remoteAddr)
-
-	if len(trusted) == 0 || !isTrustedAddr(remoteIP, trusted) {
-		return remoteIP
-	}
-
-	if xff == "" {
-		return remoteIP
-	}
-
-	parts := strings.Split(xff, ",")
-	for i := len(parts) - 1; i >= 0; i-- {
-		ip := strings.TrimSpace(parts[i])
-		if ip == "" {
-			continue
-		}
-		addr, err := netip.ParseAddr(ip)
-		if err != nil {
-			continue
-		}
-		addr = addr.Unmap()
-		if !isTrustedAddr(addr, trusted) {
-			return addr
-		}
-	}
-
-	// All IPs in XFF are trusted; return the leftmost as best guess.
-	if first := strings.TrimSpace(parts[0]); first != "" {
-		if addr, err := netip.ParseAddr(first); err == nil {
-			return addr.Unmap()
-		}
-	}
-	return remoteIP
-}
-
-// extractHostIP parses the IP from a host:port string and returns it unmapped.
-func extractHostIP(hostPort string) netip.Addr {
-	if ap, err := netip.ParseAddrPort(hostPort); err == nil {
-		return ap.Addr().Unmap()
-	}
-	if addr, err := netip.ParseAddr(hostPort); err == nil {
-		return addr.Unmap()
-	}
-	return netip.Addr{}
-}
-
-// isTrustedAddr checks if the given address falls within any of the trusted prefixes.
-func isTrustedAddr(addr netip.Addr, trusted []netip.Prefix) bool {
-	if !addr.IsValid() {
-		return false
-	}
-	for _, prefix := range trusted {
-		if prefix.Contains(addr) {
-			return true
-		}
-	}
-	return false
-}

proxy/internal/proxy/trustedproxy_test.go

@@ -1,129 +0,0 @@
-package proxy
-
-import (
-	"net/netip"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestIsTrustedProxy(t *testing.T) {
-	trusted := []netip.Prefix{
-		netip.MustParsePrefix("10.0.0.0/8"),
-		netip.MustParsePrefix("192.168.1.0/24"),
-		netip.MustParsePrefix("fd00::/8"),
-	}
-
-	tests := []struct {
-		name    string
-		ip      string
-		trusted []netip.Prefix
-		want    bool
-	}{
-		{"empty trusted list", "10.0.0.1", nil, false},
-		{"IP within /8 prefix", "10.1.2.3", trusted, true},
-		{"IP within /24 prefix", "192.168.1.100", trusted, true},
-		{"IP outside all prefixes", "203.0.113.50", trusted, false},
-		{"boundary IP just outside prefix", "192.168.2.1", trusted, false},
-		{"unparsable IP", "not-an-ip", trusted, false},
-		{"IPv6 in trusted range", "fd00::1", trusted, true},
-		{"IPv6 outside range", "2001:db8::1", trusted, false},
-		{"empty string", "", trusted, false},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			assert.Equal(t, tt.want, IsTrustedProxy(tt.ip, tt.trusted))
-		})
-	}
-}
-
-func TestResolveClientIP(t *testing.T) {
-	trusted := []netip.Prefix{
-		netip.MustParsePrefix("10.0.0.0/8"),
-		netip.MustParsePrefix("172.16.0.0/12"),
-	}
-
-	tests := []struct {
-		name       string
-		remoteAddr string
-		xff        string
-		trusted    []netip.Prefix
-		want       netip.Addr
-	}{
-		{
-			name:       "empty trusted list returns RemoteAddr",
-			remoteAddr: "203.0.113.50:9999",
-			xff:        "1.2.3.4",
-			trusted:    nil,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "untrusted RemoteAddr ignores XFF",
-			remoteAddr: "203.0.113.50:9999",
-			xff:        "1.2.3.4, 10.0.0.1",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "trusted RemoteAddr with single client in XFF",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        "203.0.113.50",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "trusted RemoteAddr walks past trusted entries in XFF",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        "203.0.113.50, 10.0.0.2, 172.16.0.5",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "trusted RemoteAddr with empty XFF falls back to RemoteAddr",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        "",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("10.0.0.1"),
-		},
-		{
-			name:       "all XFF IPs trusted returns leftmost",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        "10.0.0.2, 172.16.0.1, 10.0.0.3",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("10.0.0.2"),
-		},
-		{
-			name:       "XFF with whitespace",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        " 203.0.113.50 , 10.0.0.2 ",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "XFF with empty segments",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        "203.0.113.50,,10.0.0.2",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "multi-hop with mixed trust",
-			remoteAddr: "10.0.0.1:5000",
-			xff:        "8.8.8.8, 203.0.113.50, 172.16.0.1",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-		{
-			name:       "RemoteAddr without port",
-			remoteAddr: "10.0.0.1",
-			xff:        "203.0.113.50",
-			trusted:    trusted,
-			want:       netip.MustParseAddr("203.0.113.50"),
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			assert.Equal(t, tt.want, ResolveClientIP(tt.remoteAddr, tt.xff, tt.trusted))
-		})
-	}
-}

proxy/lifecycle.go

@@ -2,13 +2,13 @@ package proxy
 
 import (
 	"context"
-	"net/netip"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 
 	"github.com/netbirdio/netbird/client/embed"
 	"github.com/netbirdio/netbird/proxy/internal/acme"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 // Config bundles every knob the proxy reads at construction time. It mirrors
@@ -83,9 +83,9 @@ type Config struct {
 	// ForwardedProto overrides the X-Forwarded-Proto value sent to
 	// backends. Valid values: "auto", "http", "https".
 	ForwardedProto string
-	// TrustedProxies is a list of IP prefixes for trusted upstream
+	// TrustedProxies is the set of trusted upstream proxies that may set
-	// proxies that may set forwarding headers.
+	// forwarding headers.
-	TrustedProxies []netip.Prefix
+	TrustedProxies *trustedproxy.List
 	// WireguardPort is the UDP port for the embedded NetBird tunnel.
 	// Zero asks the OS for a random port.
 	WireguardPort uint16

proxy/proxyprotocol_test.go

@@ -10,12 +10,14 @@ import (
 	log "github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 func TestWrapProxyProtocol_OverridesRemoteAddr(t *testing.T) {
 	srv := &Server{
 		Logger:         log.StandardLogger(),
-		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("127.0.0.1/32")},
+		TrustedProxies: trustedproxy.FromPrefixes([]netip.Prefix{netip.MustParsePrefix("127.0.0.1/32")}),
 		ProxyProtocol:  true,
 	}
 
@@ -66,7 +68,7 @@ func TestWrapProxyProtocol_OverridesRemoteAddr(t *testing.T) {
 func TestProxyProtocolPolicy_TrustedRequires(t *testing.T) {
 	srv := &Server{
 		Logger:         log.StandardLogger(),
-		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+		TrustedProxies: trustedproxy.FromPrefixes([]netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}),
 	}
 
 	opts := proxyproto.ConnPolicyOptions{
@@ -80,7 +82,7 @@ func TestProxyProtocolPolicy_TrustedRequires(t *testing.T) {
 func TestProxyProtocolPolicy_UntrustedIgnores(t *testing.T) {
 	srv := &Server{
 		Logger:         log.StandardLogger(),
-		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+		TrustedProxies: trustedproxy.FromPrefixes([]netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}),
 	}
 
 	opts := proxyproto.ConnPolicyOptions{
@@ -94,7 +96,7 @@ func TestProxyProtocolPolicy_UntrustedIgnores(t *testing.T) {
 func TestProxyProtocolPolicy_InvalidIPRejects(t *testing.T) {
 	srv := &Server{
 		Logger:         log.StandardLogger(),
-		TrustedProxies: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+		TrustedProxies: trustedproxy.FromPrefixes([]netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}),
 	}
 
 	opts := proxyproto.ConnPolicyOptions{

proxy/server.go

@@ -67,6 +67,7 @@ import (
 	"github.com/netbirdio/netbird/proxy/web"
 	"github.com/netbirdio/netbird/shared/management/domain"
 	"github.com/netbirdio/netbird/shared/management/proto"
+	"github.com/netbirdio/netbird/trustedproxy"
 	"github.com/netbirdio/netbird/util/embeddedroots"
 )
 
@@ -79,19 +80,19 @@ type portRouter struct {
 
 type Server struct {
 	ctx               context.Context
-	mgmtClient    proto.ProxyServiceClient
+	mgmtClient        proto.ProxyServiceClient
-	proxy         *proxy.ReverseProxy
+	proxy             *proxy.ReverseProxy
-	netbird       *roundtrip.NetBird
+	netbird           *roundtrip.NetBird
-	acme          *acme.Manager
+	acme              *acme.Manager
 	staticCertWatcher *certwatch.Watcher
-	auth          *auth.Middleware
+	auth              *auth.Middleware
-	http          *http.Server
+	http              *http.Server
-	https         *http.Server
+	https             *http.Server
-	debug         *http.Server
+	debug             *http.Server
-	healthServer  *health.Server
+	healthServer      *health.Server
-	healthChecker *health.Checker
+	healthChecker     *health.Checker
-	meter         *proxymetrics.Metrics
+	meter             *proxymetrics.Metrics
-	accessLog     *accesslog.Logger
+	accessLog         *accesslog.Logger
 	// middlewareManager drives per-target middleware dispatch. Always
 	// constructed during boot; an empty registry produces empty chains and
 	// the reverse-proxy stays on the no-capture fast path.
@@ -99,16 +100,16 @@ type Server struct {
 	// middlewareRegistry is the source of registered middleware factories.
 	// Concrete middlewares register themselves through init().
 	middlewareRegistry *middleware.Registry
-	mainRouter    *nbtcp.Router
+	mainRouter         *nbtcp.Router
-	mainPort      uint16
+	mainPort           uint16
-	udpMu         sync.Mutex
+	udpMu              sync.Mutex
-	udpRelays     map[types.ServiceID]*udprelay.Relay
+	udpRelays          map[types.ServiceID]*udprelay.Relay
-	udpRelayWg    sync.WaitGroup
+	udpRelayWg         sync.WaitGroup
-	portMu        sync.RWMutex
+	portMu             sync.RWMutex
-	portRouters   map[uint16]*portRouter
+	portRouters        map[uint16]*portRouter
-	svcPorts      map[types.ServiceID][]uint16
+	svcPorts           map[types.ServiceID][]uint16
-	lastMappings  map[types.ServiceID]*proto.ProxyMapping
+	lastMappings       map[types.ServiceID]*proto.ProxyMapping
-	portRouterWg  sync.WaitGroup
+	portRouterWg       sync.WaitGroup
 
 	// hijackTracker tracks hijacked connections (e.g. WebSocket upgrades)
 	// so they can be closed during graceful shutdown, since http.Server.Shutdown
@@ -192,10 +193,10 @@ type Server struct {
 	// ForwardedProto overrides the X-Forwarded-Proto value sent to backends.
 	// Valid values: "auto" (detect from TLS), "http", "https".
 	ForwardedProto string
-	// TrustedProxies is a list of IP prefixes for trusted upstream proxies.
+	// TrustedProxies is the set of trusted upstream proxies. When set,
-	// When set, forwarding headers from these sources are preserved and
+	// forwarding headers from these sources are preserved and appended to
-	// appended to instead of being stripped.
+	// instead of being stripped.
-	TrustedProxies []netip.Prefix
+	TrustedProxies *trustedproxy.List
 	// WireguardPort is the port for the NetBird tunnel interface. Use 0
 	// for a random OS-assigned port. A fixed port only works with
 	// single-account deployments; multiple accounts will fail to bind
@@ -718,7 +719,7 @@ func (s *Server) wrapProxyProtocol(ln net.Listener) net.Listener {
 		Listener:          ln,
 		ReadHeaderTimeout: proxyProtoHeaderTimeout,
 	}
-	if len(s.TrustedProxies) > 0 {
+	if !s.TrustedProxies.Empty() {
 		ppListener.ConnPolicy = s.proxyProtocolPolicy
 	} else {
 		s.Logger.Warn("PROXY protocol enabled without trusted proxies; any source may send PROXY headers")
@@ -742,10 +743,8 @@ func (s *Server) proxyProtocolPolicy(opts proxyproto.ConnPolicyOptions) (proxypr
 	addr = addr.Unmap()
 
 	// called per accept
-	for _, prefix := range s.TrustedProxies {
+	if s.TrustedProxies.Contains(addr) {
-		if prefix.Contains(addr) {
+		return proxyproto.REQUIRE, nil
-			return proxyproto.REQUIRE, nil
-		}
 	}
 	return proxyproto.IGNORE, nil
 }

proxy/trustedproxy.go

@@ -1,43 +0,0 @@
-package proxy
-
-import (
-	"fmt"
-	"net/netip"
-	"strings"
-)
-
-// ParseTrustedProxies parses a comma-separated list of CIDR prefixes or bare IPs
-// into a slice of netip.Prefix values suitable for trusted proxy configuration.
-// Bare IPs are converted to single-host prefixes (/32 or /128).
-func ParseTrustedProxies(raw string) ([]netip.Prefix, error) {
-	if raw == "" {
-		return nil, nil
-	}
-
-	parts := strings.Split(raw, ",")
-	prefixes := make([]netip.Prefix, 0, len(parts))
-	for _, part := range parts {
-		part = strings.TrimSpace(part)
-		if part == "" {
-			continue
-		}
-
-		prefix, err := netip.ParsePrefix(part)
-		if err == nil {
-			prefixes = append(prefixes, prefix)
-			continue
-		}
-
-		addr, addrErr := netip.ParseAddr(part)
-		if addrErr != nil {
-			return nil, fmt.Errorf("parse trusted proxy %q: not a valid CIDR or IP: %w", part, addrErr)
-		}
-
-		bits := 32
-		if addr.Is6() {
-			bits = 128
-		}
-		prefixes = append(prefixes, netip.PrefixFrom(addr, bits))
-	}
-	return prefixes, nil
-}

proxy/trustedproxy_test.go

@@ -1,90 +0,0 @@
-package proxy
-
-import (
-	"net/netip"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-)
-
-func TestParseTrustedProxies(t *testing.T) {
-	tests := []struct {
-		name    string
-		raw     string
-		want    []netip.Prefix
-		wantErr bool
-	}{
-		{
-			name: "empty string returns nil",
-			raw:  "",
-			want: nil,
-		},
-		{
-			name: "single CIDR",
-			raw:  "10.0.0.0/8",
-			want: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
-		},
-		{
-			name: "single bare IPv4",
-			raw:  "1.2.3.4",
-			want: []netip.Prefix{netip.MustParsePrefix("1.2.3.4/32")},
-		},
-		{
-			name: "single bare IPv6",
-			raw:  "::1",
-			want: []netip.Prefix{netip.MustParsePrefix("::1/128")},
-		},
-		{
-			name: "comma-separated CIDRs",
-			raw:  "10.0.0.0/8, 192.168.1.0/24",
-			want: []netip.Prefix{
-				netip.MustParsePrefix("10.0.0.0/8"),
-				netip.MustParsePrefix("192.168.1.0/24"),
-			},
-		},
-		{
-			name: "mixed CIDRs and bare IPs",
-			raw:  "10.0.0.0/8, 1.2.3.4, fd00::/8",
-			want: []netip.Prefix{
-				netip.MustParsePrefix("10.0.0.0/8"),
-				netip.MustParsePrefix("1.2.3.4/32"),
-				netip.MustParsePrefix("fd00::/8"),
-			},
-		},
-		{
-			name: "whitespace around entries",
-			raw:  "  10.0.0.0/8 , 192.168.0.0/16  ",
-			want: []netip.Prefix{
-				netip.MustParsePrefix("10.0.0.0/8"),
-				netip.MustParsePrefix("192.168.0.0/16"),
-			},
-		},
-		{
-			name: "trailing comma produces no extra entry",
-			raw:  "10.0.0.0/8,",
-			want: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
-		},
-		{
-			name:    "invalid entry",
-			raw:     "not-an-ip",
-			wantErr: true,
-		},
-		{
-			name:    "partially invalid",
-			raw:     "10.0.0.0/8, garbage",
-			wantErr: true,
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got, err := ParseTrustedProxies(tt.raw)
-			if tt.wantErr {
-				require.Error(t, err)
-				return
-			}
-			require.NoError(t, err)
-			assert.Equal(t, tt.want, got)
-		})
-	}
-}

relay/cmd/root.go

@@ -24,6 +24,7 @@ import (
 	"github.com/netbirdio/netbird/shared/metrics"
 	"github.com/netbirdio/netbird/shared/relay/auth"
 	"github.com/netbirdio/netbird/stun"
+	"github.com/netbirdio/netbird/trustedproxy"
 	"github.com/netbirdio/netbird/util"
 )
 
@@ -45,6 +46,9 @@ type Config struct {
 	LogLevel                 string
 	LogFile                  string
 	HealthcheckListenAddress string
+	// TrustedProxies is a comma-separated list of upstream proxy CIDRs/IPs whose
+	// X-Real-Ip/X-Real-Port headers are trusted. Empty means never trust these headers.
+	TrustedProxies string
 	// STUN server configuration
 	EnableSTUN   bool
 	STUNPorts    []int
@@ -116,6 +120,7 @@ func init() {
 	rootCmd.PersistentFlags().StringVar(&cobraConfig.LogLevel, "log-level", "info", "log level")
 	rootCmd.PersistentFlags().StringVar(&cobraConfig.LogFile, "log-file", "console", "log file")
 	rootCmd.PersistentFlags().StringVarP(&cobraConfig.HealthcheckListenAddress, "health-listen-address", "H", ":9000", "listen address of healthcheck server")
+	rootCmd.PersistentFlags().StringVar(&cobraConfig.TrustedProxies, "trusted-proxies", "", "comma-separated list of upstream proxy CIDRs or IPs whose X-Real-Ip/X-Real-Port headers are trusted; leave empty to always use the direct connection address")
 	rootCmd.PersistentFlags().BoolVar(&cobraConfig.EnableSTUN, "enable-stun", false, "enable embedded STUN server")
 	rootCmd.PersistentFlags().IntSliceVar(&cobraConfig.STUNPorts, "stun-ports", []int{3478}, "ports for the embedded STUN server (can be specified multiple times or comma-separated)")
 	rootCmd.PersistentFlags().StringVar(&cobraConfig.STUNLogLevel, "stun-log-level", "info", "log level for STUN server (panic, fatal, error, warn, info, debug, trace)")
@@ -155,8 +160,15 @@ func execute(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("setup metrics: %v", err)
 	}
 
+	trustedProxies, err := trustedproxy.Parse(cobraConfig.TrustedProxies)
+	if err != nil {
+		log.Debugf("failed to parse trusted proxies: %s", err)
+		return fmt.Errorf("failed to parse trusted proxies: %s", err)
+	}
+
 	srvListenerCfg := server.ListenerConfig{
-		Address: cobraConfig.ListenAddress,
+		Address:        cobraConfig.ListenAddress,
+		TrustedProxies: trustedProxies,
 	}
 
 	tlsConfig, tlsSupport, err := handleTLSConfig(cobraConfig)

relay/server/listener/ws/listener.go

@@ -15,6 +15,7 @@ import (
 	"github.com/netbirdio/netbird/relay/protocol"
 	relaylistener "github.com/netbirdio/netbird/relay/server/listener"
 	"github.com/netbirdio/netbird/shared/relay"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 const (
@@ -27,6 +28,9 @@ type Listener struct {
 	Address string
 	// TLSConfig is the TLS configuration for the server.
 	TLSConfig *tls.Config
+	// TrustedProxies is the set of upstream proxies whose X-Real-Ip/X-Real-Port
+	// headers are trusted. Headers from any other immediate peer are ignored.
+	TrustedProxies *trustedproxy.List
 
 	server   *http.Server
 	acceptFn func(conn relaylistener.Conn)
@@ -75,7 +79,7 @@ func (l *Listener) Shutdown(ctx context.Context) error {
 }
 
 func (l *Listener) onAccept(w http.ResponseWriter, r *http.Request) {
-	connRemoteAddr := remoteAddr(r)
+	connRemoteAddr := remoteAddr(r, l.TrustedProxies)
 
 	acceptOptions := &websocket.AcceptOptions{
 		OriginPatterns: []string{"*"},
@@ -102,9 +106,17 @@ func (l *Listener) onAccept(w http.ResponseWriter, r *http.Request) {
 	l.acceptFn(conn)
 }
 
-func remoteAddr(r *http.Request) string {
+func remoteAddr(r *http.Request, trustedProxies *trustedproxy.List) string {
-	if r.Header.Get("X-Real-Ip") == "" || r.Header.Get("X-Real-Port") == "" {
+	realIP := r.Header.Get("X-Real-Ip")
+	realPort := r.Header.Get("X-Real-Port")
+	if realIP == "" || realPort == "" {
 		return r.RemoteAddr
 	}
-	return net.JoinHostPort(r.Header.Get("X-Real-Ip"), r.Header.Get("X-Real-Port"))
+
+	if !trustedProxies.IsTrusted(r.RemoteAddr) {
+		log.Debugf("ignoring X-Real-Ip header from untrusted peer %s", r.RemoteAddr)
+		return r.RemoteAddr
+	}
+
+	return net.JoinHostPort(realIP, realPort)
 }

relay/server/server.go

@@ -15,14 +15,17 @@ import (
 	"github.com/netbirdio/netbird/relay/server/listener/quic"
 	"github.com/netbirdio/netbird/relay/server/listener/ws"
 	quictls "github.com/netbirdio/netbird/shared/relay/tls"
+	"github.com/netbirdio/netbird/trustedproxy"
 )
 
 // ListenerConfig is the configuration for the listener.
 // Address: the address to bind the listener to. It could be an address behind a reverse proxy.
 // TLSConfig: the TLS configuration for the listener.
+// TrustedProxies: upstream proxy prefixes whose forwarding headers (X-Real-Ip/X-Real-Port) are trusted.
 type ListenerConfig struct {
-	Address   string
+	Address        string
-	TLSConfig *tls.Config
+	TLSConfig      *tls.Config
+	TrustedProxies *trustedproxy.List
 }
 
 // Server is the main entry point for the relay server.
@@ -62,8 +65,9 @@ func NewServer(config Config) (*Server, error) {
 // Listen starts the relay server.
 func (r *Server) Listen(cfg ListenerConfig) error {
 	wSListener := &ws.Listener{
-		Address:   cfg.Address,
+		Address:        cfg.Address,
-		TLSConfig: cfg.TLSConfig,
+		TLSConfig:      cfg.TLSConfig,
+		TrustedProxies: cfg.TrustedProxies,
 	}
 
 	r.listenerMux.Lock()

trustedproxy/trustedproxy.go

@@ -0,0 +1,132 @@
+package trustedproxy
+
+import (
+	"fmt"
+	"net/netip"
+	"strings"
+)
+
+// List holds a parsed set of trusted upstream proxy prefixes and answers trust
+// questions against it. The zero value (and a nil *List) is a valid, empty list
+// that never trusts any address, so callers can use it without a nil check.
+type List struct {
+	prefixes []netip.Prefix
+}
+
+// Parse parses a comma-separated list of CIDR prefixes or bare IPs into a List.
+// Bare IPs are converted to single-host prefixes (/32 or /128). An empty input
+// yields an empty List that trusts nothing.
+func Parse(raw string) (*List, error) {
+	if raw == "" {
+		return &List{}, nil
+	}
+
+	parts := strings.Split(raw, ",")
+	prefixes := make([]netip.Prefix, 0, len(parts))
+	for _, part := range parts {
+		part = strings.TrimSpace(part)
+		if part == "" {
+			continue
+		}
+
+		prefix, err := netip.ParsePrefix(part)
+		if err == nil {
+			prefixes = append(prefixes, prefix)
+			continue
+		}
+
+		addr, addrErr := netip.ParseAddr(part)
+		if addrErr != nil {
+			return nil, fmt.Errorf("parse trusted proxy %q: not a valid CIDR or IP: %w", part, addrErr)
+		}
+
+		bits := 32
+		if addr.Is6() {
+			bits = 128
+		}
+		prefixes = append(prefixes, netip.PrefixFrom(addr, bits))
+	}
+	return &List{prefixes: prefixes}, nil
+}
+
+// FromPrefixes wraps an already-parsed set of prefixes in a List.
+func FromPrefixes(prefixes []netip.Prefix) *List {
+	return &List{prefixes: prefixes}
+}
+
+// Empty reports whether the list contains no prefixes.
+func (l *List) Empty() bool {
+	return l == nil || len(l.prefixes) == 0
+}
+
+// IsTrusted reports whether the given host:port or bare IP falls within the list.
+func (l *List) IsTrusted(remoteAddr string) bool {
+	if l.Empty() {
+		return false
+	}
+	return l.Contains(ExtractHostIP(remoteAddr))
+}
+
+// Contains reports whether the given address falls within any trusted prefix.
+func (l *List) Contains(addr netip.Addr) bool {
+	if l.Empty() || !addr.IsValid() {
+		return false
+	}
+	for _, prefix := range l.prefixes {
+		if prefix.Contains(addr) {
+			return true
+		}
+	}
+	return false
+}
+
+// ResolveClientIP extracts the real client IP from X-Forwarded-For using the
+// list. It walks the XFF chain right-to-left, skipping IPs that match trusted
+// prefixes; the first untrusted IP is the real client. If the list is empty or
+// remoteAddr is not trusted, it returns the remoteAddr IP directly, ignoring any
+// forwarding headers.
+func (l *List) ResolveClientIP(remoteAddr, xff string) netip.Addr {
+	remoteIP := ExtractHostIP(remoteAddr)
+
+	if l.Empty() || !l.Contains(remoteIP) {
+		return remoteIP
+	}
+
+	if xff == "" {
+		return remoteIP
+	}
+
+	parts := strings.Split(xff, ",")
+	for i := len(parts) - 1; i >= 0; i-- {
+		ip := strings.TrimSpace(parts[i])
+		if ip == "" {
+			continue
+		}
+		addr, err := netip.ParseAddr(ip)
+		if err != nil {
+			continue
+		}
+		addr = addr.Unmap()
+		if !l.Contains(addr) {
+			return addr
+		}
+	}
+
+	if first := strings.TrimSpace(parts[0]); first != "" {
+		if addr, err := netip.ParseAddr(first); err == nil {
+			return addr.Unmap()
+		}
+	}
+	return remoteIP
+}
+
+// ExtractHostIP parses the IP from a host:port string and returns it unmapped.
+func ExtractHostIP(hostPort string) netip.Addr {
+	if ap, err := netip.ParseAddrPort(hostPort); err == nil {
+		return ap.Addr().Unmap()
+	}
+	if addr, err := netip.ParseAddr(hostPort); err == nil {
+		return addr.Unmap()
+	}
+	return netip.Addr{}
+}

trustedproxy/trustedproxy_test.go

@@ -0,0 +1,216 @@
+package trustedproxy
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		name    string
+		raw     string
+		want    []netip.Prefix
+		wantErr bool
+	}{
+		{
+			name: "empty string returns empty list",
+			raw:  "",
+			want: nil,
+		},
+		{
+			name: "single CIDR",
+			raw:  "10.0.0.0/8",
+			want: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+		},
+		{
+			name: "single bare IPv4",
+			raw:  "1.2.3.4",
+			want: []netip.Prefix{netip.MustParsePrefix("1.2.3.4/32")},
+		},
+		{
+			name: "single bare IPv6",
+			raw:  "::1",
+			want: []netip.Prefix{netip.MustParsePrefix("::1/128")},
+		},
+		{
+			name: "comma-separated CIDRs",
+			raw:  "10.0.0.0/8, 192.168.1.0/24",
+			want: []netip.Prefix{
+				netip.MustParsePrefix("10.0.0.0/8"),
+				netip.MustParsePrefix("192.168.1.0/24"),
+			},
+		},
+		{
+			name: "mixed CIDRs and bare IPs",
+			raw:  "10.0.0.0/8, 1.2.3.4, fd00::/8",
+			want: []netip.Prefix{
+				netip.MustParsePrefix("10.0.0.0/8"),
+				netip.MustParsePrefix("1.2.3.4/32"),
+				netip.MustParsePrefix("fd00::/8"),
+			},
+		},
+		{
+			name: "whitespace around entries",
+			raw:  "  10.0.0.0/8 , 192.168.0.0/16  ",
+			want: []netip.Prefix{
+				netip.MustParsePrefix("10.0.0.0/8"),
+				netip.MustParsePrefix("192.168.0.0/16"),
+			},
+		},
+		{
+			name: "trailing comma produces no extra entry",
+			raw:  "10.0.0.0/8,",
+			want: []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")},
+		},
+		{
+			name:    "invalid entry",
+			raw:     "not-an-ip",
+			wantErr: true,
+		},
+		{
+			name:    "partially invalid",
+			raw:     "10.0.0.0/8, garbage",
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Parse(tt.raw)
+			if tt.wantErr {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			assert.Equal(t, tt.want, got.prefixes)
+		})
+	}
+}
+
+func TestListIsTrusted(t *testing.T) {
+	list, err := Parse("10.0.0.0/8, 192.168.1.0/24, fd00::/8")
+	require.NoError(t, err)
+
+	tests := []struct {
+		name string
+		addr string
+		list *List
+		want bool
+	}{
+		{"nil list", "10.0.0.1", nil, false},
+		{"empty list", "10.0.0.1", &List{}, false},
+		{"IP within /8 prefix", "10.1.2.3", list, true},
+		{"IP within /24 prefix", "192.168.1.100", list, true},
+		{"IP outside all prefixes", "203.0.113.50", list, false},
+		{"boundary IP just outside prefix", "192.168.2.1", list, false},
+		{"unparsable IP", "not-an-ip", list, false},
+		{"IPv6 in trusted range", "fd00::1", list, true},
+		{"IPv6 outside range", "2001:db8::1", list, false},
+		{"empty string", "", list, false},
+		{"host:port within prefix", "10.1.2.3:9999", list, true},
+		{"host:port outside prefix", "203.0.113.50:9999", list, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.list.IsTrusted(tt.addr))
+		})
+	}
+}
+
+func TestListResolveClientIP(t *testing.T) {
+	trusted, err := Parse("10.0.0.0/8, 172.16.0.0/12")
+	require.NoError(t, err)
+
+	tests := []struct {
+		name       string
+		remoteAddr string
+		xff        string
+		list       *List
+		want       netip.Addr
+	}{
+		{
+			name:       "empty list returns RemoteAddr",
+			remoteAddr: "203.0.113.50:9999",
+			xff:        "1.2.3.4",
+			list:       &List{},
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "nil list returns RemoteAddr",
+			remoteAddr: "203.0.113.50:9999",
+			xff:        "1.2.3.4",
+			list:       nil,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "untrusted RemoteAddr ignores XFF",
+			remoteAddr: "203.0.113.50:9999",
+			xff:        "1.2.3.4, 10.0.0.1",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "trusted RemoteAddr with single client in XFF",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        "203.0.113.50",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "trusted RemoteAddr walks past trusted entries in XFF",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        "203.0.113.50, 10.0.0.2, 172.16.0.5",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "trusted RemoteAddr with empty XFF falls back to RemoteAddr",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        "",
+			list:       trusted,
+			want:       netip.MustParseAddr("10.0.0.1"),
+		},
+		{
+			name:       "all XFF IPs trusted returns leftmost",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        "10.0.0.2, 172.16.0.1, 10.0.0.3",
+			list:       trusted,
+			want:       netip.MustParseAddr("10.0.0.2"),
+		},
+		{
+			name:       "XFF with whitespace",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        " 203.0.113.50 , 10.0.0.2 ",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "XFF with empty segments",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        "203.0.113.50,,10.0.0.2",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "multi-hop with mixed trust",
+			remoteAddr: "10.0.0.1:5000",
+			xff:        "8.8.8.8, 203.0.113.50, 172.16.0.1",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+		{
+			name:       "RemoteAddr without port",
+			remoteAddr: "10.0.0.1",
+			xff:        "203.0.113.50",
+			list:       trusted,
+			want:       netip.MustParseAddr("203.0.113.50"),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.list.ResolveClientIP(tt.remoteAddr, tt.xff))
+		})
+	}
+}