rename Q3RCON_STALE_SESSION_TIMEOUT to Q3RCON_SESSION_TIMEOUT

add a trace level log when a session gets deleted.

.gitignore

@@ -19,3 +19,7 @@
 
 # Go workspace file
 go.work
+
+# testing
+run.sh
+server.yaml

CHANGELOG.md

@@ -11,8 +11,41 @@ Before any major/minor/patch bump all unit tests will be run to verify they pass
 
 -   [x]
 
+## [0.6.0] - 2024-03-21
+
+### Added
+
+-   new environment variable `Q3RCON_DEBUG` for enabling debug logging. Defaults to 0.
+-   rcon responses are now logged at debug level
+-   invalid responses (rcon and query) now logged
+
+### Changed
+
+-   All packet header checking methods moved into Session struct.
+
+### Fixed
+
+-   a bug causing the proxy not to send back query responses
+
+## [0.3.0] - 2024-03-08
+
+### Added
+
+-   outgoing rcon requests now logged at info level
+-   new environment variable `Q3RCON_HOST` for specifying which ip to bind the proxy to. Defaults to `0.0.0.0`.
+
+### Changed
+
+-   now using [logrus][logrus] package for logging.
+
+### Fixed
+
+-   a `slice bounds out of range` error due to query packets being logged.
+
 ## [0.1.0] - 2024-01-27
 
+### Added
+
 -   only forward packets if the header matches q3 rcon/query.
 
 ## [0.0.1] - 2024-01-27
@@ -20,3 +53,5 @@ Before any major/minor/patch bump all unit tests will be run to verify they pass
 ### Added
 
 -   All source files for lilproxy including full commit history.
+
+[logrus]: https://github.com/sirupsen/logrus

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.21
+FROM golang:1.21 AS build_image
 
 WORKDIR /usr/src/app
 
@@ -6,9 +6,16 @@ WORKDIR /usr/src/app
 COPY go.mod go.sum ./
 RUN go mod download && go mod verify
 
-# build binary and place into /usr/local/bin/
 COPY . .
-RUN go build -v -o /usr/local/bin/q3rcon-proxy ./cmd/q3rcon-proxy/
+
+# build binary, place into ./bin/
+RUN CGO_ENABLED=0 GOOS=linux go build -o ./bin/q3rcon-proxy ./cmd/q3rcon-proxy/
+
+FROM scratch AS final_image
+
+WORKDIR /bin/
+
+COPY --from=build_image /usr/src/app/bin/q3rcon-proxy .
 
 # Command to run when starting the container
-ENTRYPOINT [ "q3rcon-proxy" ]
+ENTRYPOINT [ "./q3rcon-proxy" ]

README.md

@@ -2,6 +2,10 @@
 
 A modification of [lilproxy][lilproxy_url] that forwards only Q3 rcon/query packets. Useful for separating the rcon port from the game server port.
 
+### Why
+
+Unfortunately the Q3Rcon engine ties the rcon port to the game servers public port used for client connections. This proxy will allow you to run rcon through a separate whitelisted port.
+
 ### Use
 
 Run one or multiple rcon proxies by setting an environment variable `Q3RCON_PROXY`
@@ -16,13 +20,15 @@ This would configure q3rcon-proxy to run 3 proxy servers listening on ports `200
 
 Then just run the binary which you can compile yourself, download from `Releases` or use the included Dockerfile.
 
-### Why
+### Logging
 
-Avoid sending plaintext rcon commands to the public game server port. In general I would advise anyone using rcon remotely to use a secured connection but perhaps you've passed rcon to a clan friend who doesn't know about secured connections. Now you can instruct them to use rcon only through a whitelisted port.
+Set the log level with environment variable `Q3RCON_LOGLEVEL`:
+
+`0 = Panic, 1 = Fatal, 2 = Error, 3 = Warning, 4 = Info, 5 = Debug, 6 = Trace`
 
 ### Special Thanks
 
-[Dylan][user_link] For writing this proxy.
+[Dylan][user_link] For writing [lilproxy][lilproxy_url].
 
 [lilproxy_url]: https://github.com/dgparker/lilproxy
 [user_link]: https://github.com/dgparker

cmd/q3rcon-proxy/main.go

@@ -2,20 +2,57 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"os"
+	"slices"
 	"strings"
+	"time"
+
+	log "github.com/sirupsen/logrus"
 
 	"github.com/onyx-and-iris/q3rcon-proxy/pkg/udpproxy"
 )
 
-func start(proxy string) {
+func main() {
+	logLevel, err := getEnvInt("Q3RCON_LOGLEVEL")
+	if err != nil {
+		log.Fatalf("unable to parse Q3RCON_LEVEL: %s", err.Error())
+	}
+	if slices.Contains(log.AllLevels, log.Level(logLevel)) {
+		log.SetLevel(log.Level(logLevel))
+	}
+
+	proxies := os.Getenv("Q3RCON_PROXY")
+	if proxies == "" {
+		log.Fatal("env Q3RCON_PROXY required")
+	}
+
+	host := os.Getenv("Q3RCON_HOST")
+	if host == "" {
+		host = "0.0.0.0"
+	}
+
+	sessionTimeout, err := getEnvInt("Q3RCON_SESSION_TIMEOUT")
+	if err != nil {
+		log.Fatalf("unable to parse Q3RCON_SESSION_TIMEOUT: %s", err.Error())
+	}
+
+	for _, proxy := range strings.Split(proxies, ";") {
+		go start(host, proxy, sessionTimeout)
+	}
+
+	<-make(chan int)
+}
+
+func start(host, proxy string, sessionTimeout int) {
 	port, target := func() (string, string) {
 		x := strings.Split(proxy, ":")
 		return x[0], x[1]
 	}()
 
-	c, err := udpproxy.New(fmt.Sprintf("%s:%s", host, port), fmt.Sprintf("127.0.0.1:%s", target))
+	c, err := udpproxy.New(
+		fmt.Sprintf("%s:%s", host, port),
+		fmt.Sprintf("127.0.0.1:%s", target),
+		udpproxy.WithSessionTimeout(time.Duration(sessionTimeout)*time.Minute))
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -24,27 +61,3 @@ func start(proxy string) {
 
 	log.Fatal(c.ListenAndServe())
 }
-
-var (
-	proxies, host string
-)
-
-func init() {
-	proxies = os.Getenv("Q3RCON_PROXY")
-	if proxies == "" {
-		log.Fatal("env Q3RCON_PROXY required")
-	}
-
-	host = os.Getenv("Q3RCON_HOST")
-	if host == "" {
-		host = "0.0.0.0"
-	}
-}
-
-func main() {
-	for _, proxy := range strings.Split(proxies, ";") {
-		go start(proxy)
-	}
-
-	<-make(chan int)
-}

cmd/q3rcon-proxy/util.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"os"
+	"strconv"
+)
+
+func getEnvInt(key string) (int, error) {
+	s := os.Getenv(key)
+	if s == "" {
+		return 0, nil
+	}
+	v, err := strconv.Atoi(s)
+	if err != nil {
+		return 0, err
+	}
+	return v, nil
+}

debian/q3rcon-proxy.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=Q3Rcon Proxy Service
+Wants=network.target
+After=network.target
+
+[Service]
+Type=simple
+User=gameservers
+Environment="Q3RCON_PROXY=20000:28960;20001:28961;20002:28962"
+Environment="Q3RCON_HOST=0.0.0.0"
+Environment="Q3RCON_DEBUG=0"
+
+ExecStart=/usr/local/bin/q3rcon-proxy
+Restart=always
+RestartSec=3
+
+[Install]
+WantedBy=multi-user.target

pkg/udpproxy/session.go

@@ -1,6 +1,8 @@
 package udpproxy
 
 import (
+	"errors"
+	"fmt"
 	"net"
 	"strings"
 	"time"
@@ -8,24 +10,27 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-type Session struct {
+type session struct {
 	serverConn *net.UDPConn
 	proxyConn  *net.UDPConn
 	caddr      *net.UDPAddr
 	updateTime time.Time
+
+	validator
 }
 
-func createSession(caddr *net.UDPAddr, raddr *net.UDPAddr, proxyConn *net.UDPConn) (*Session, error) {
+func newSession(caddr *net.UDPAddr, raddr *net.UDPAddr, proxyConn *net.UDPConn) (*session, error) {
 	serverConn, err := net.DialUDP("udp", nil, raddr)
 	if err != nil {
 		return nil, err
 	}
 
-	session := &Session{
+	session := &session{
 		serverConn: serverConn,
 		proxyConn:  proxyConn,
 		caddr:      caddr,
 		updateTime: time.Now(),
+		validator:  newValidator(),
 	}
 
 	go session.listen()
@@ -33,12 +38,12 @@ func createSession(caddr *net.UDPAddr, raddr *net.UDPAddr, proxyConn *net.UDPCon
 	return session, nil
 }
 
-func (s *Session) listen() error {
-	for {
+func (s *session) listen() error {
 	buf := make([]byte, 2048)
+	for {
 		n, err := s.serverConn.Read(buf)
 		if err != nil {
-			log.Println(err)
+			log.Error(err)
 			continue
 		}
 
@@ -46,29 +51,54 @@ func (s *Session) listen() error {
 	}
 }
 
-func (s *Session) proxyFrom(buf []byte) error {
+func (s *session) proxyFrom(buf []byte) error {
+	if !s.isValidResponsePacket(buf) {
+		err := errors.New("not a rcon or query response packet")
+		log.Error(err.Error())
+		return err
+	}
+
 	s.updateTime = time.Now()
 	_, err := s.proxyConn.WriteToUDP(buf, s.caddr)
 	if err != nil {
-		log.Println(err)
+		log.Error(err)
 		return err
 	}
 
+	if s.isRconResponsePacket(buf) {
+		if s.isBadRconResponse(buf) {
+			log.Infof("Response: Bad rcon from %s", s.caddr.IP)
+		} else {
+			log.Debugf("Response: %s", string(buf[len(s.rconResponseHeader):]))
+		}
+	}
+
 	return nil
 }
 
-func (s *Session) proxyTo(buf []byte) error {
+func (s *session) proxyTo(buf []byte) error {
+	if !s.isValidRequestPacket(buf) {
+		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
+	}
+
 	s.updateTime = time.Now()
 	_, err := s.serverConn.Write(buf)
 	if err != nil {
-		log.Println(err)
+		log.Error(err)
 		return err
 	}
 
-	cmd := string(buf)
-	if cmd[:8] == "\xff\xff\xff\xffrcon" {
-		parts := strings.Split(cmd, " ")
-		log.Info("From [", s.caddr.IP, "] To [", s.serverConn.RemoteAddr().String(), "] Command: ", strings.Join(parts[2:], " "))
+	if s.isRconRequestPacket(buf) {
+		parts := strings.SplitN(string(buf), " ", 3)
+		log.Infof("From [%s] To [%s] Command: %s", s.caddr.IP, s.serverConn.RemoteAddr(), parts[len(parts)-1])
 	}
 
 	return nil

pkg/udpproxy/sessioncache.go

@@ -0,0 +1,41 @@
+package udpproxy
+
+import "sync"
+
+// sessionCache tracks connection sessions
+type sessionCache struct {
+	mu   sync.RWMutex
+	data map[string]*session
+}
+
+// newSessionCache creates a usable sessionCache.
+func newSessionCache() sessionCache {
+	return sessionCache{
+		data: make(map[string]*session),
+	}
+}
+
+// Read returns the associated session for an addr
+func (sc *sessionCache) Read(addr string) (*session, bool) {
+	sc.mu.RLock()
+	defer sc.mu.RUnlock()
+
+	v, ok := sc.data[addr]
+	return v, ok
+}
+
+// Upsert overrides the session for a given addr.
+func (sc *sessionCache) Upsert(addr string, session *session) {
+	sc.mu.Lock()
+	defer sc.mu.Unlock()
+
+	sc.data[addr] = session
+}
+
+// Delete removes the session for the given addr.
+func (sc *sessionCache) Delete(addr string) {
+	sc.mu.Lock()
+	defer sc.mu.Unlock()
+
+	delete(sc.data, addr)
+}

pkg/udpproxy/udpproxy.go

@@ -2,23 +2,37 @@ package udpproxy
 
 import (
 	"net"
-	"sync"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 )
 
+// Option is a functional option type that allows us to configure the Client.
+type Option func(*Client)
+
+// WithSessionTimeout is a functional option to set the session timeout
+func WithSessionTimeout(timeout time.Duration) Option {
+	return func(c *Client) {
+		if timeout < time.Minute {
+			log.Warnf("cannot set stale session timeout to less than 1 minute.. defaulting to 5 minutes")
+			return
+		}
+
+		c.sessionTimeout = timeout
+	}
+}
+
 type Client struct {
 	laddr *net.UDPAddr
 	raddr *net.UDPAddr
 
 	proxyConn *net.UDPConn
 
-	mutex    sync.RWMutex
-	sessions map[string]*Session
+	sessionCache   sessionCache
+	sessionTimeout time.Duration
 }
 
-func New(port, target string) (*Client, error) {
+func New(port, target string, options ...Option) (*Client, error) {
 	laddr, err := net.ResolveUDPAddr("udp", port)
 	if err != nil {
 		return nil, err
@@ -29,16 +43,18 @@ func New(port, target string) (*Client, error) {
 		return nil, err
 	}
 
-	return &Client{
+	c := &Client{
 		laddr:          laddr,
 		raddr:          raddr,
-		mutex:    sync.RWMutex{},
-		sessions: map[string]*Session{},
-	}, nil
-}
+		sessionCache:   newSessionCache(),
+		sessionTimeout: 5 * time.Minute,
+	}
 
-func (c *Client) isValidPacket(header []byte) bool {
-	return string(header[:8]) == "\xff\xff\xff\xffrcon" || string(header[:13]) == "\xff\xff\xff\xffgetstatus" || string(header[:11]) == "\xff\xff\xff\xffgetinfo"
+	for _, o := range options {
+		o(c)
+	}
+
+	return c, nil
 }
 
 func (c *Client) ListenAndServe() error {
@@ -50,26 +66,22 @@ func (c *Client) ListenAndServe() error {
 
 	go c.pruneSessions()
 
-	for {
 	buf := make([]byte, 2048)
+	for {
 		n, caddr, err := c.proxyConn.ReadFromUDP(buf)
 		if err != nil {
-			log.Println(err)
+			log.Error(err)
 		}
 
-		if !c.isValidPacket(buf[:16]) {
-			continue
-		}
-
-		session, found := c.sessions[caddr.String()]
-		if !found {
-			session, err = createSession(caddr, c.raddr, c.proxyConn)
+		session, ok := c.sessionCache.Read(caddr.String())
+		if !ok {
+			session, err = newSession(caddr, c.raddr, c.proxyConn)
 			if err != nil {
-				log.Println(err)
+				log.Error(err)
 				continue
 			}
 
-			c.sessions[caddr.String()] = session
+			c.sessionCache.Upsert(caddr.String(), session)
 		}
 
 		go session.proxyTo(buf[:n])
@@ -79,15 +91,12 @@ func (c *Client) ListenAndServe() error {
 func (c *Client) pruneSessions() {
 	ticker := time.NewTicker(1 * time.Minute)
 
-	// the locks here could be abusive and i dont even know if this is a real
-	// problem but we definitely need to clean up stale sessions
 	for range ticker.C {
-		for _, session := range c.sessions {
-			c.mutex.RLock()
-			if time.Since(session.updateTime) > time.Minute*5 {
-				delete(c.sessions, session.caddr.String())
+		for _, session := range c.sessionCache.data {
+			if time.Since(session.updateTime) > c.sessionTimeout {
+				c.sessionCache.Delete(session.caddr.String())
+				log.Tracef("session for %s deleted", session.caddr)
 			}
-			c.mutex.RUnlock()
 		}
 	}
 }

pkg/udpproxy/validator.go

@@ -0,0 +1,65 @@
+package udpproxy
+
+import "bytes"
+
+type validator struct {
+	rconRequestHeader         []byte
+	getstatusRequestHeader    []byte
+	getinfoRequestHeader      []byte
+	getchallengeRequestHeader []byte
+	rconResponseHeader        []byte
+	getstatusResponseHeader   []byte
+	getinfoResponseHeader     []byte
+	badRconIdentifier         []byte
+}
+
+func newValidator() validator {
+	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 {
+	return bytes.Equal(buf[:len(c)], c)
+}
+
+func (v validator) isRconRequestPacket(buf []byte) bool {
+	return v.compare(buf, v.rconRequestHeader)
+}
+
+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 {
+	return v.isRconRequestPacket(buf) || v.isQueryRequestPacket(buf)
+}
+
+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 {
+	return v.compare(buf, v.getstatusResponseHeader) ||
+		v.compare(buf, v.getinfoResponseHeader)
+}
+
+func (v validator) isValidResponsePacket(buf []byte) bool {
+	return v.isRconResponsePacket(buf) || v.isQueryResponsePacket(buf)
+}
+
+func (v validator) isBadRconResponse(buf []byte) bool {
+	return v.compare(buf[len(v.rconResponseHeader):], v.badRconIdentifier)
+}