From 2fc0f7a74ff2092eea140b7b3a3e298e11444528 Mon Sep 17 00:00:00 2001
From: onyx-and-iris <code@onyxandiris.online>
Date: Sat, 28 Sep 2024 15:36:04 +0100
Subject: [PATCH] log challenge requests

---
 pkg/udpproxy/session.go   | 11 ++++++--
 pkg/udpproxy/udpproxy.go  |  4 +--
 pkg/udpproxy/validator.go | 54 ++++++++++++++++++++++-----------------
 3 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/pkg/udpproxy/session.go b/pkg/udpproxy/session.go
index 2d5b2b5..99b86e3 100644
--- a/pkg/udpproxy/session.go
+++ b/pkg/udpproxy/session.go
@@ -2,6 +2,7 @@ package udpproxy
 
 import (
 	"errors"
+	"fmt"
 	"net"
 	"strings"
 	"time"
@@ -68,7 +69,7 @@ func (s *session) proxyFrom(buf []byte) error {
 		if s.isBadRconResponse(buf) {
 			log.Infof("Response: Bad rcon from %s", s.caddr.IP)
 		} else {
-			log.Debugf("Response: %s", string(buf[10:]))
+			log.Debugf("Response: %s", string(buf[len(s.rconResponseHeader):]))
 		}
 	}
 
@@ -77,7 +78,13 @@ func (s *session) proxyFrom(buf []byte) error {
 
 func (s *session) proxyTo(buf []byte) error {
 	if !s.isValidRequestPacket(buf) {
-		err := errors.New("not a rcon or query request packet")
+		var err error
+		if s.isChallengeRequestPacket(buf) {
+			parts := strings.SplitN(string(buf), " ", 3)
+			err = fmt.Errorf("invalid challenge from %s with GUID: %s", s.caddr.IP, parts[len(parts)-1])
+		} else {
+			err = errors.New("not a rcon or query request packet")
+		}
 		log.Error(err.Error())
 		return err
 	}
diff --git a/pkg/udpproxy/udpproxy.go b/pkg/udpproxy/udpproxy.go
index 6437da9..04df3b8 100644
--- a/pkg/udpproxy/udpproxy.go
+++ b/pkg/udpproxy/udpproxy.go
@@ -53,8 +53,8 @@ func (c *Client) ListenAndServe() error {
 			log.Error(err)
 		}
 
-		session, found := c.sessions[caddr.String()]
-		if !found {
+		session, ok := c.sessions[caddr.String()]
+		if !ok {
 			session, err = newSession(caddr, c.raddr, c.proxyConn)
 			if err != nil {
 				log.Error(err)
diff --git a/pkg/udpproxy/validator.go b/pkg/udpproxy/validator.go
index f60b405..5faf007 100644
--- a/pkg/udpproxy/validator.go
+++ b/pkg/udpproxy/validator.go
@@ -3,57 +3,63 @@ package udpproxy
 import "bytes"
 
 type validator struct {
-	rconRequestHeader       []byte
-	getstatusRequestHeader  []byte
-	getinfoRequestHeader    []byte
-	rconResponseHeader      []byte
-	getstatusResponseHeader []byte
-	getinfoResponseHeader   []byte
-	badRconIdentifier       []byte
+	rconRequestHeader         []byte
+	getstatusRequestHeader    []byte
+	getinfoRequestHeader      []byte
+	getchallengeRequestHeader []byte
+	rconResponseHeader        []byte
+	getstatusResponseHeader   []byte
+	getinfoResponseHeader     []byte
+	badRconIdentifier         []byte
 }
 
 func newValidator() validator {
-	v := validator{}
-	v.rconRequestHeader = []byte("\xff\xff\xff\xffrcon")
-	v.getstatusRequestHeader = []byte("\xff\xff\xff\xffgetstatus")
-	v.getinfoRequestHeader = []byte("\xff\xff\xff\xffgetinfo")
-	v.rconResponseHeader = []byte("\xff\xff\xff\xffprint\n")
-	v.getstatusResponseHeader = []byte("\xff\xff\xff\xffstatusResponse\n")
-	v.getinfoResponseHeader = []byte("\xff\xff\xff\xffinfoResponse\n")
-	v.badRconIdentifier = []byte("Bad rcon")
-	return v
+	return validator{
+		rconRequestHeader:         []byte("\xff\xff\xff\xffrcon"),
+		getstatusRequestHeader:    []byte("\xff\xff\xff\xffgetstatus"),
+		getinfoRequestHeader:      []byte("\xff\xff\xff\xffgetinfo"),
+		getchallengeRequestHeader: []byte("\xff\xff\xff\xffgetchallenge"),
+		rconResponseHeader:        []byte("\xff\xff\xff\xffprint\n"),
+		getstatusResponseHeader:   []byte("\xff\xff\xff\xffstatusResponse\n"),
+		getinfoResponseHeader:     []byte("\xff\xff\xff\xffinfoResponse\n"),
+		badRconIdentifier:         []byte("Bad rcon"),
+	}
 }
 
-func (v *validator) compare(buf, c []byte) bool {
+func (v validator) compare(buf, c []byte) bool {
 	return bytes.Equal(buf[:len(c)], c)
 }
 
-func (v *validator) isRconRequestPacket(buf []byte) bool {
+func (v validator) isRconRequestPacket(buf []byte) bool {
 	return v.compare(buf, v.rconRequestHeader)
 }
 
-func (v *validator) isQueryRequestPacket(buf []byte) bool {
+func (v validator) isQueryRequestPacket(buf []byte) bool {
 	return v.compare(buf, v.getstatusRequestHeader) ||
 		v.compare(buf, v.getinfoRequestHeader)
 }
 
-func (v *validator) isValidRequestPacket(buf []byte) bool {
+func (v validator) isValidRequestPacket(buf []byte) bool {
 	return v.isRconRequestPacket(buf) || v.isQueryRequestPacket(buf)
 }
 
-func (v *validator) isRconResponsePacket(buf []byte) bool {
+func (v validator) isChallengeRequestPacket(buf []byte) bool {
+	return v.compare(buf, v.getchallengeRequestHeader)
+}
+
+func (v validator) isRconResponsePacket(buf []byte) bool {
 	return v.compare(buf, v.rconResponseHeader)
 }
 
-func (v *validator) isQueryResponsePacket(buf []byte) bool {
+func (v validator) isQueryResponsePacket(buf []byte) bool {
 	return v.compare(buf, v.getstatusResponseHeader) ||
 		v.compare(buf, v.getinfoResponseHeader)
 }
 
-func (v *validator) isValidResponsePacket(buf []byte) bool {
+func (v validator) isValidResponsePacket(buf []byte) bool {
 	return v.isRconResponsePacket(buf) || v.isQueryResponsePacket(buf)
 }
 
-func (v *validator) isBadRconResponse(buf []byte) bool {
+func (v validator) isBadRconResponse(buf []byte) bool {
 	return v.compare(buf[len(v.rconResponseHeader):], v.badRconIdentifier)
 }