[client] Add excluded port range handling for PKCE flow

client/internal/auth/pkce_flow.go

@@ -13,6 +13,7 @@ import (
 	"net"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -46,9 +47,10 @@ type PKCEAuthorizationFlow struct {
 func NewPKCEAuthorizationFlow(config internal.PKCEAuthProviderConfig) (*PKCEAuthorizationFlow, error) {
 	var availableRedirectURL string
 
-	// find the first available redirect URL
+	excludedRanges := getSystemExcludedPortRanges()
+
 	for _, redirectURL := range config.RedirectURLs {
-		if !isRedirectURLPortUsed(redirectURL) {
+		if !isRedirectURLPortUsed(redirectURL, excludedRanges) {
 			availableRedirectURL = redirectURL
 			break
 		}
@@ -282,15 +284,22 @@ func createCodeChallenge(codeVerifier string) string {
 	return base64.RawURLEncoding.EncodeToString(sha2[:])
 }
 
-// isRedirectURLPortUsed checks if the port used in the redirect URL is in use.
-func isRedirectURLPortUsed(redirectURL string) bool {
+// isRedirectURLPortUsed checks if the port used in the redirect URL is in use or excluded on Windows.
+func isRedirectURLPortUsed(redirectURL string, excludedRanges []excludedPortRange) bool {
 	parsedURL, err := url.Parse(redirectURL)
 	if err != nil {
 		log.Errorf("failed to parse redirect URL: %v", err)
 		return true
 	}
 
-	addr := fmt.Sprintf(":%s", parsedURL.Port())
+	port := parsedURL.Port()
+
+	if isPortInExcludedRange(port, excludedRanges) {
+		log.Warnf("port %s is in Windows excluded port range, skipping", port)
+		return true
+	}
+
+	addr := fmt.Sprintf(":%s", port)
 	conn, err := net.DialTimeout("tcp", addr, 3*time.Second)
 	if err != nil {
 		return false
@@ -304,6 +313,33 @@ func isRedirectURLPortUsed(redirectURL string) bool {
 	return true
 }
 
+// excludedPortRange represents a range of excluded ports.
+type excludedPortRange struct {
+	start int
+	end   int
+}
+
+// isPortInExcludedRange checks if the given port is in any of the excluded ranges.
+func isPortInExcludedRange(port string, excludedRanges []excludedPortRange) bool {
+	if len(excludedRanges) == 0 {
+		return false
+	}
+
+	portNum, err := strconv.Atoi(port)
+	if err != nil {
+		log.Debugf("invalid port number %s: %v", port, err)
+		return false
+	}
+
+	for _, r := range excludedRanges {
+		if portNum >= r.start && portNum <= r.end {
+			return true
+		}
+	}
+
+	return false
+}
+
 func renderPKCEFlowTmpl(w http.ResponseWriter, authError error) {
 	tmpl, err := template.New("pkce-auth-flow").Parse(templates.PKCEAuthMsgTmpl)
 	if err != nil {

client/internal/auth/pkce_flow_other.go

@@ -0,0 +1,8 @@
+//go:build !windows
+
+package auth
+
+// getSystemExcludedPortRanges returns nil on non-Windows platforms.
+func getSystemExcludedPortRanges() []excludedPortRange {
+	return nil
+}

client/internal/auth/pkce_flow_test.go

@@ -2,8 +2,11 @@ package auth
 
 import (
 	"context"
+	"fmt"
+	"net"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/netbirdio/netbird/client/internal"
@@ -69,3 +72,147 @@ func TestPromptLogin(t *testing.T) {
 		})
 	}
 }
+
+func TestIsPortInExcludedRange(t *testing.T) {
+	tests := []struct {
+		name            string
+		port            string
+		excludedRanges  []excludedPortRange
+		expectedBlocked bool
+	}{
+		{
+			name:            "Port in excluded range",
+			port:            "8080",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: true,
+		},
+		{
+			name:            "Port at start of range",
+			port:            "8000",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: true,
+		},
+		{
+			name:            "Port at end of range",
+			port:            "8100",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: true,
+		},
+		{
+			name:            "Port before range",
+			port:            "7999",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: false,
+		},
+		{
+			name:            "Port after range",
+			port:            "8101",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: false,
+		},
+		{
+			name:            "Empty excluded ranges",
+			port:            "8080",
+			excludedRanges:  []excludedPortRange{},
+			expectedBlocked: false,
+		},
+		{
+			name:            "Nil excluded ranges",
+			port:            "8080",
+			excludedRanges:  nil,
+			expectedBlocked: false,
+		},
+		{
+			name: "Multiple ranges - port in second range",
+			port: "9050",
+			excludedRanges: []excludedPortRange{
+				{start: 8000, end: 8100},
+				{start: 9000, end: 9100},
+			},
+			expectedBlocked: true,
+		},
+		{
+			name: "Multiple ranges - port not in any range",
+			port: "8500",
+			excludedRanges: []excludedPortRange{
+				{start: 8000, end: 8100},
+				{start: 9000, end: 9100},
+			},
+			expectedBlocked: false,
+		},
+		{
+			name:            "Invalid port string",
+			port:            "invalid",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: false,
+		},
+		{
+			name:            "Empty port string",
+			port:            "",
+			excludedRanges:  []excludedPortRange{{start: 8000, end: 8100}},
+			expectedBlocked: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := isPortInExcludedRange(tt.port, tt.excludedRanges)
+			assert.Equal(t, tt.expectedBlocked, result, "Port exclusion check mismatch")
+		})
+	}
+}
+
+func TestIsRedirectURLPortUsed(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	defer func() {
+		_ = listener.Close()
+	}()
+
+	usedPort := listener.Addr().(*net.TCPAddr).Port
+
+	tests := []struct {
+		name           string
+		redirectURL    string
+		excludedRanges []excludedPortRange
+		expectedUsed   bool
+	}{
+		{
+			name:           "Port in excluded range",
+			redirectURL:    "http://127.0.0.1:8080/",
+			excludedRanges: []excludedPortRange{{start: 8000, end: 8100}},
+			expectedUsed:   true,
+		},
+		{
+			name:           "Port actually in use",
+			redirectURL:    fmt.Sprintf("http://127.0.0.1:%d/", usedPort),
+			excludedRanges: nil,
+			expectedUsed:   true,
+		},
+		{
+			name:           "Port not in use and not excluded",
+			redirectURL:    "http://127.0.0.1:65432/",
+			excludedRanges: nil,
+			expectedUsed:   false,
+		},
+		{
+			name:           "Invalid URL without port",
+			redirectURL:    "not-a-valid-url",
+			excludedRanges: nil,
+			expectedUsed:   false,
+		},
+		{
+			name:           "Port excluded even if not in use",
+			redirectURL:    "http://127.0.0.1:8050/",
+			excludedRanges: []excludedPortRange{{start: 8000, end: 8100}},
+			expectedUsed:   true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := isRedirectURLPortUsed(tt.redirectURL, tt.excludedRanges)
+			assert.Equal(t, tt.expectedUsed, result, "Port usage check mismatch")
+		})
+	}
+}

client/internal/auth/pkce_flow_windows.go

@@ -0,0 +1,64 @@
+//go:build windows
+
+package auth
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/sys/windows/registry"
+)
+
+// getSystemExcludedPortRanges retrieves the excluded port ranges from Windows.
+func getSystemExcludedPortRanges() []excludedPortRange {
+	ranges, err := getExcludedPortRangesFromRegistry()
+	if err == nil && len(ranges) > 0 {
+		return ranges
+	}
+
+	return ranges
+}
+
+// getExcludedPortRangesFromRegistry retrieves excluded port ranges from Windows registry.
+func getExcludedPortRangesFromRegistry() ([]excludedPortRange, error) {
+	k, err := registry.OpenKey(registry.LOCAL_MACHINE,
+		`SYSTEM\CurrentControlSet\Services\Tcpip\Parameters`,
+		registry.QUERY_VALUE)
+	if err != nil {
+		return nil, fmt.Errorf("open registry key: %w", err)
+	}
+	defer func() {
+		if err := k.Close(); err != nil {
+			log.Debugf("failed to close registry key: %v", err)
+		}
+	}()
+
+	reservedPorts, _, err := k.GetStringsValue("ReservedPorts")
+	if err != nil {
+		return nil, fmt.Errorf("read ReservedPorts: %w", err)
+	}
+
+	var ranges []excludedPortRange
+	for _, portSpec := range reservedPorts {
+		parts := strings.Split(portSpec, "-")
+		if len(parts) != 2 {
+			continue
+		}
+
+		start, err := strconv.Atoi(strings.TrimSpace(parts[0]))
+		if err != nil {
+			continue
+		}
+
+		end, err := strconv.Atoi(strings.TrimSpace(parts[1]))
+		if err != nil {
+			continue
+		}
+
+		ranges = append(ranges, excludedPortRange{start: start, end: end})
+	}
+
+	return ranges, nil
+}