feat: Add BungeeGuard Compatible mode

.web/docs/guide/compatibility.md

@@ -13,14 +13,14 @@ We highly recommend using [Paper](https://papermc.io/) for running a server in m
 Gate is tested with older and most recent versions of it.
 
 You can use `modern` forwarding (like Velocity does) if you run Paper
-1.13.2 or higher. If you use Paper 1.12.2 or lower, you must use `legacy` BungeeCord-style forwarding.
+1.13.2 or higher. If you use Paper 1.12.2 or lower, you can use `legacy` BungeeCord-style forwarding or the more secure `bungeeguard` [Bungeeguard](https://www.spigotmc.org/resources/bungeeguard.79601/) forwarding.
 
 ## Spigot
 
 Spigot is not well-tested with Gate.
 However, it is based on vanilla and as it is the base for Paper, it is relatively well-supported.
 
-Spigot does not support Gate/Velocity modern forwarding, but does support legacy BungeeCord forwarding.
+Spigot does not support Gate/Velocity modern forwarding, but does support legacy BungeeCord forwarding and the more secure Bungeeguard forwarding when using the [Bungeeguard](https://www.spigotmc.org/resources/bungeeguard.79601/) plugin.
 
 ## Forks of Spigot/Paper
 

config.yml

@@ -86,10 +86,12 @@ config:
   # This allows you to customize how player information such as IPs and UUIDs are forwarded to your server.
   # See the documentation for more information.
   forwarding:
-    # Options: legacy, none, velocity
+    # Options: legacy, none, bungeeguard, velocity
     mode: legacy
     # The secret used if the mode is velocity.
     #velocitySecret: secret_here
+    # The secret used if the mode is bungeeguard.
+    #bungeeGuardSecret: secret_here
   # Proxy protocol (HA-Proxy) determines whether Gate should support proxy protocol for players.
   # Do not enable this if you don't know what it is.
   proxyProtocol: false

pkg/edition/java/config/config.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"fmt"
+
 	liteconfig "go.minekube.com/gate/pkg/edition/java/lite/config"
 	"go.minekube.com/gate/pkg/edition/java/proto/version"
 	"go.minekube.com/gate/pkg/util/componentutil"
@@ -135,8 +136,9 @@ type (
 		ShowPlugins bool `yaml:"showPlugins"`
 	}
 	Forwarding struct {
-		Mode           ForwardingMode `yaml:"mode"`
-		VelocitySecret string         `yaml:"velocitySecret"` // Used with "velocity" mode
+		Mode              ForwardingMode `yaml:"mode"`
+		VelocitySecret    string         `yaml:"velocitySecret"`    // Used with "velocity" mode
+		BungeeGuardSecret string         `yaml:"bungeeGuardSecret"` // Used with "bungeeguard" mode
 	}
 	Compression struct {
 		Threshold int `yaml:"threshold"`
@@ -171,6 +173,8 @@ const (
 	// VelocityForwardingMode is a forwarding mode specified by the Velocity java proxy and
 	// supported by PaperSpigot for versions starting at 1.13.
 	VelocityForwardingMode ForwardingMode = "velocity"
+	// BungeeGuardForwardingMode is a forwarding mode used by versions lower than 1.13
+	BungeeGuardForwardingMode ForwardingMode = "bungeeguard"
 )
 
 // Validate validates Config.
@@ -217,9 +221,9 @@ func (c *Config) Validate() (warns []error, errs []error) {
 	case NoneForwardingMode:
 		w("Player forwarding is disabled! Backend servers will have players with " +
 			"offline-mode UUIDs and the same IP as the proxy.")
-	case LegacyForwardingMode, VelocityForwardingMode:
+	case LegacyForwardingMode, VelocityForwardingMode, BungeeGuardForwardingMode:
 	default:
-		e("Unknown forwarding mode %q, must be one of none,legacy,velocity", c.Forwarding.Mode)
+		e("Unknown forwarding mode %q, must be one of none,legacy,velocity,bungeeguard", c.Forwarding.Mode)
 	}
 
 	if len(c.Servers) == 0 {

pkg/edition/java/proxy/phase/types.go

@@ -77,7 +77,7 @@ func (*legacyForgeConnType) AddGameProfileTokensIfRequired(
 	// since both use the "hostname" field in the handshake. We add a special property to the
 	// profile instead, which will be ignored by non-Forge servers and can be intercepted by a
 	// Forge coremod, such as SpongeForge.
-	if forwardingType == config.LegacyForwardingMode {
+	if forwardingType == config.LegacyForwardingMode || forwardingType == config.BungeeGuardForwardingMode {
 		original.Properties = append(original.Properties, profile.Property{Name: "forgeClient", Value: "true"})
 	}
 	return original

pkg/edition/java/proxy/server.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"go.minekube.com/gate/pkg/edition/java/forge/modernforge"
+	"go.minekube.com/gate/pkg/edition/java/profile"
 	"go.minekube.com/gate/pkg/edition/java/proto/state/states"
 	"net"
 	"strings"
@@ -343,8 +344,12 @@ func (s *serverConnection) handshakeAddr(vHost string, player Player) string {
 	var ok bool
 	if ha, ok = s.Server().ServerInfo().(HandshakeAddresser); !ok {
 		if ha, ok = s.Server().(HandshakeAddresser); !ok {
-			if s.config().Forwarding.Mode == config.LegacyForwardingMode {
+			switch s.config().Forwarding.Mode {
+			case config.LegacyForwardingMode:
 				return s.createLegacyForwardingAddress()
+			case config.BungeeGuardForwardingMode:
+				secret := s.config().Forwarding.BungeeGuardSecret
+				return s.createBungeeGuardForwardingAddress(secret)
 			}
 		}
 	}
@@ -491,6 +496,27 @@ func (s *serverConnection) createLegacyForwardingAddress() string {
 	return b.String()
 }
 
+func (s *serverConnection) createBungeeGuardForwardingAddress(secret string) string {
+	// Bungeeguard IP forwading is the same as the legacy Bungeecord IP forwarding but with an additional
+	// property in the profile properties that contains the bungeeguard-token.
+	playerIP := netutil.Host(s.player.RemoteAddr())
+	b := new(strings.Builder)
+	b.WriteString(s.server.ServerInfo().Addr().String())
+	const sep = "\000"
+	b.WriteString(sep)
+	b.WriteString(playerIP)
+	b.WriteString(sep)
+	b.WriteString(s.player.profile.ID.Undashed())
+	b.WriteString(sep)
+	props, err := json.Marshal(
+		append(s.player.profile.Properties, profile.Property{Name: "bungeeguard-token", Value: secret}))
+	if err != nil { // should never happen
+		panic(err)
+	}
+	b.WriteString(string(props)) // first convert props to string
+	return b.String()
+}
+
 // Returns the active backend server connection or false if inactive.
 func (s *serverConnection) ensureConnected() (backend netmc.MinecraftConn, connected bool) {
 	if s == nil {

pkg/edition/java/proxy/session_backend_login.go

@@ -250,7 +250,7 @@ func (b *backendLoginSessionHandler) handleServerLoginSuccess() {
 }
 
 func (b *backendLoginSessionHandler) Disconnected() {
-	if b.config().Forwarding.Mode == config.LegacyForwardingMode {
+	if b.config().Forwarding.Mode == config.LegacyForwardingMode || b.config().Forwarding.Mode == config.BungeeGuardForwardingMode {
 		b.requestCtx.result(nil, errs.NewSilentErr(`The connection to the remote server was unexpectedly closed.
 This is usually because the remote server does not have BungeeCord IP forwarding correctly enabled.`))
 	} else {

pkg/edition/java/proxy/session_client_auth.go

@@ -72,7 +72,6 @@ func (a *authSessionHandler) Activated() {
 	// Some connection types may need to alter the game profile.
 	gameProfile := *a.inbound.delegate.Type().AddGameProfileTokensIfRequired(
 		a.profile, a.config().Forwarding.Mode)
-
 	profileRequest := NewGameProfileRequestEvent(a.inbound, gameProfile, a.onlineMode)
 	a.eventMgr.Fire(profileRequest)
 	conn := a.inbound.delegate.MinecraftConn