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fix: protect concurrent map access in port-forward #303

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fix: protect concurrent map access in port-forward #303

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49 changes: 33 additions & 16 deletions cmd/portforward.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ import (
"os/signal"
"strconv"
"strings"
"sync"
"time"

"github.com/mendersoftware/go-lib-micro/ws"
Expand Down Expand Up @@ -51,9 +52,9 @@ var portForwardCmd = &cobra.Command{
"it possible to port-forward to third hosts running in the device's network.\n" +
"In this case, the specification will be LOCAL_PORT:REMOTE_HOST:REMOTE_PORT.\n\n" +
"You can specify multiple port mapping specifications.",
Example: " mender-cli port-forward DEVICE_ID 8000:8000\n" +
" mender-cli port-forward DEVICE_ID udp/8000:8000\n" +
" mender-cli port-forward DEVICE_ID tcp/8000:192.168.1.1:8000",
Example: " mender-cli port-forward DEVICE_ID 8000:8000\n" +
" mender-cli port-forward DEVICE_ID udp/8000:8000\n" +
" mender-cli port-forward DEVICE_ID tcp/8000:192.168.1.1:8000",
Args: cobra.MinimumNArgs(2),
Run: func(c *cobra.Command, args []string) {
cmd, err := NewPortForwardCmd(c, args)
Expand All @@ -63,10 +64,10 @@ var portForwardCmd = &cobra.Command{
}

var portForwardMaxDuration = 24 * time.Hour

var errPortForwardNotImplemented = errors.New(
"port forward not implemented or enabled on the device",
)

var errRestart = errors.New("restart")

func init() {
Expand All @@ -87,17 +88,18 @@ type portMapping struct {

// PortForwardCmd handles the port-forward command
type PortForwardCmd struct {
server string
token string
skipVerify bool
deviceID string
sessionID string
bindingHost string
portMappings []portMapping
recvChans map[string]chan *ws.ProtoMsg
running bool
stop chan struct{}
err error
server string
token string
skipVerify bool
deviceID string
sessionID string
bindingHost string
portMappings []portMapping
recvChans map[string]chan *ws.ProtoMsg
recvChansLock sync.RWMutex
running bool
stop chan struct{}
err error
}

func getPortMappings(args []string) ([]portMapping, error) {
Expand All @@ -106,6 +108,7 @@ func getPortMappings(args []string) ([]portMapping, error) {
for _, arg := range args {
remoteHost := localhost
protocol := wspf.PortForwardProtocolTCP

if strings.Contains(arg, "/") {
parts := strings.SplitN(arg, "/", 2)
if parts[0] == protocolTCP {
Expand All @@ -117,17 +120,20 @@ func getPortMappings(args []string) ([]portMapping, error) {
}
arg = parts[1]
}

var localPort, remotePort int
if strings.Contains(arg, ":") {
parts := strings.SplitN(arg, ":", 3)
if len(parts) == 3 {
remoteHost = parts[1]
parts = []string{parts[0], parts[2]}
}

localPort, err = strconv.Atoi(parts[0])
if err != nil || localPort < 0 || localPort > 65536 {
return nil, errors.New("invalid port number: " + parts[0])
}

remotePort, err = strconv.Atoi(parts[1])
if err != nil || remotePort < 0 || remotePort > 65536 {
return nil, errors.New("invalid port number: " + parts[1])
Expand All @@ -140,6 +146,7 @@ func getPortMappings(args []string) ([]portMapping, error) {
localPort = port
remotePort = port
}

portMappings = append(portMappings, portMapping{
Protocol: protocol,
LocalPort: uint16(localPort),
Expand Down Expand Up @@ -239,13 +246,15 @@ func (c *PortForwardCmd) run() error {
if err != nil {
return err
}

go forwarder.Run(ctx, c.sessionID, msgChan, c.recvChans)
case protocolUDP:
forwarder, err := NewUDPPortForwarder(c.bindingHost, portMapping.LocalPort,
portMapping.RemoteHost, portMapping.RemotePort)
if err != nil {
return err
}

go forwarder.Run(ctx, c.sessionID, msgChan, c.recvChans)
default:
return errors.New("unknown protocol: " + portMapping.Protocol)
Expand Down Expand Up @@ -313,13 +322,15 @@ func (c *PortForwardCmd) handshake(client *deviceconnect.Client) error {
if err != nil {
return err
}

m := &ws.ProtoMsg{
Header: ws.ProtoHdr{
Proto: ws.ProtoTypeControl,
MsgType: ws.MessageTypeOpen,
},
Body: body,
}

err = client.WriteMessage(m)
if err != nil {
return err
Expand All @@ -329,6 +340,7 @@ func (c *PortForwardCmd) handshake(client *deviceconnect.Client) error {
if err != nil {
return err
}

if msg.Header.MsgType == ws.MessageTypeError {
erro := new(ws.Error)
_ = msgpack.Unmarshal(msg.Body, erro)
Expand Down Expand Up @@ -366,6 +378,7 @@ func (c *PortForwardCmd) closeSession(client *deviceconnect.Client) error {
MsgType: ws.MessageTypeClose,
},
}

err := client.WriteMessage(m)
if err != nil {
return err
Expand Down Expand Up @@ -411,7 +424,11 @@ func (c *PortForwardCmd) processIncomingMessages(
m.Header.MsgType == wspf.MessageTypePortForwardStop) {
connectionID, _ := m.Header.Properties[wspf.PropertyConnectionID].(string)
if connectionID != "" {
if recvChan, ok := c.recvChans[connectionID]; ok {
c.recvChansLock.RLock()
recvChan, ok := c.recvChans[connectionID]
c.recvChansLock.RUnlock()

if ok {
recvChan <- m
}
}
Expand Down
57 changes: 37 additions & 20 deletions cmd/portforward_tcp.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -34,10 +34,11 @@ import (
const portForwardTCPChannelSize = 20

type TCPPortForwarder struct {
listen net.Listener
remoteHost string
remotePort uint16
mutexAck map[string]*sync.Mutex
listen net.Listener
remoteHost string
remotePort uint16
mutexAck map[string]*sync.Mutex
mutexAckLock sync.RWMutex
}

func NewTCPPortForwarder(
Expand All @@ -51,6 +52,7 @@ func NewTCPPortForwarder(
if err != nil {
return nil, err
}

return &TCPPortForwarder{
listen: listen,
remoteHost: remoteHost,
Expand All @@ -76,6 +78,7 @@ func (p *TCPPortForwarder) Run(
if err != nil {
return
}

fmt.Printf(
"Handling connection from %s to %s\n",
conn.RemoteAddr().String(),
Expand Down Expand Up @@ -110,9 +113,14 @@ func (p *TCPPortForwarder) handleRequest(
) {
defer conn.Close()

p.mutexAckLock.Lock()
p.mutexAck[connectionID] = &sync.Mutex{}
p.mutexAckLock.Unlock()

defer func() {
p.mutexAckLock.Lock()
delete(p.mutexAck, connectionID)
p.mutexAckLock.Unlock()
}()

errChan := make(chan error)
Expand All @@ -124,11 +132,13 @@ func (p *TCPPortForwarder) handleRequest(
RemoteHost: &p.remoteHost,
RemotePort: &p.remotePort,
}

body, err := msgpack.Marshal(portforwardNew)
if err != nil {
fmt.Fprintf(os.Stderr, "error: %v\n", err.Error())
panic(err)
}

m := &ws.ProtoMsg{
Header: ws.ProtoHdr{
Proto: ws.ProtoTypePortForward,
Expand All @@ -140,9 +150,10 @@ func (p *TCPPortForwarder) handleRequest(
},
Body: body,
}
msgChan <- m

msgChan <- m
sendStopMessage := true

defer func() {
conn.Close()
if sendStopMessage {
Expand Down Expand Up @@ -195,9 +206,11 @@ func (p *TCPPortForwarder) handleRequest(
}
} else if m.Header.Proto == ws.ProtoTypePortForward &&
m.Header.MsgType == wspf.MessageTypePortForwardAck {
if m, ok := p.mutexAck[connectionID]; ok {
m.Unlock()
p.mutexAckLock.RLock()
if mutex, ok := p.mutexAck[connectionID]; ok {
mutex.Unlock()
}
p.mutexAckLock.RUnlock()
Comment on lines +209 to +213
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@merlin-northern merlin-northern Nov 2, 2025

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The reason will be displayed to describe this comment to others. Learn more.

Would you consider:

Suggested change
p.mutexAckLock.RLock()
if mutex, ok := p.mutexAck[connectionID]; ok {
mutex.Unlock()
}
p.mutexAckLock.RUnlock()
p.mutexAckLock.RLock()
mutex, ok := p.mutexAck[connectionID]
p.mutexAckLock.RUnlock()
if ok && mutex != nil {
mutex.Unlock()
}

you know, I do panic when I see mutexes in the critical section ;-)

}
case <-ctx.Done():
return
Expand All @@ -214,21 +227,25 @@ func (p *TCPPortForwarder) handleRequest(
}
return
case data := <-dataChan:
// lock the ack mutex, we don't allow more than one in-flight message
p.mutexAck[connectionID].Lock()
p.mutexAckLock.RLock()
mutex, ok := p.mutexAck[connectionID]
p.mutexAckLock.RUnlock()

m := &ws.ProtoMsg{
Header: ws.ProtoHdr{
Proto: ws.ProtoTypePortForward,
MsgType: wspf.MessageTypePortForward,
SessionID: sessionID,
Properties: map[string]interface{}{
wspf.PropertyConnectionID: connectionID,
if ok {
mutex.Lock()
m := &ws.ProtoMsg{
Header: ws.ProtoHdr{
Proto: ws.ProtoTypePortForward,
MsgType: wspf.MessageTypePortForward,
SessionID: sessionID,
Properties: map[string]interface{}{
wspf.PropertyConnectionID: connectionID,
},
},
},
Body: data,
Body: data,
}
msgChan <- m
}
msgChan <- m
case <-ctx.Done():
return
}
Expand All @@ -241,13 +258,13 @@ func (p *TCPPortForwarder) handleRequestConnection(
conn net.Conn,
) {
data := make([]byte, readBuffLength)

for {
n, err := conn.Read(data)
if err != nil {
errChan <- err
break
}

if n > 0 {
tmp := make([]byte, n)
copy(tmp, data[:n])
Expand Down