client: reject invalid work connection addresses (#5472)

client/proxy/proxy.go

@@ -174,6 +174,26 @@ func (pxy *BaseProxy) HandleTCPWorkConnection(workConn net.Conn, m *msg.StartWor
 	xl.Tracef("handle tcp work connection, useEncryption: %t, useCompression: %t",
 		baseCfg.Transport.UseEncryption, baseCfg.Transport.UseCompression)
 
+	var srcAddr, dstAddr *net.TCPAddr
+	if m.SrcAddr != "" && m.SrcPort != 0 {
+		if m.DstAddr == "" {
+			m.DstAddr = "127.0.0.1"
+		}
+		var err error
+		srcAddr, err = net.ResolveTCPAddr("tcp", net.JoinHostPort(m.SrcAddr, strconv.Itoa(int(m.SrcPort))))
+		if err != nil {
+			xl.Warnf("resolve source address [%s] error: %v", m.SrcAddr, err)
+			_ = workConn.Close()
+			return
+		}
+		dstAddr, err = net.ResolveTCPAddr("tcp", net.JoinHostPort(m.DstAddr, strconv.Itoa(int(m.DstPort))))
+		if err != nil {
+			xl.Warnf("resolve destination address [%s] error: %v", m.DstAddr, err)
+			_ = workConn.Close()
+			return
+		}
+	}
+
 	remote, recycleFn, err := pxy.wrapWorkConn(workConn, encKey)
 	if err != nil {
 		xl.Errorf("wrap work connection: %v", err)
@@ -183,11 +203,6 @@ func (pxy *BaseProxy) HandleTCPWorkConnection(workConn net.Conn, m *msg.StartWor
 	// check if we need to send proxy protocol info
 	var connInfo plugin.ConnectionInfo
 	if m.SrcAddr != "" && m.SrcPort != 0 {
-		if m.DstAddr == "" {
-			m.DstAddr = "127.0.0.1"
-		}
-		srcAddr, _ := net.ResolveTCPAddr("tcp", net.JoinHostPort(m.SrcAddr, strconv.Itoa(int(m.SrcPort))))
-		dstAddr, _ := net.ResolveTCPAddr("tcp", net.JoinHostPort(m.DstAddr, strconv.Itoa(int(m.DstPort))))
 		connInfo.SrcAddr = srcAddr
 		connInfo.DstAddr = dstAddr
 	}

client/proxy/proxy_test.go

@@ -0,0 +1,47 @@
+// Copyright 2026 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !frps
+
+package proxy
+
+import (
+	"io"
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	v1 "github.com/fatedier/frp/pkg/config/v1"
+	"github.com/fatedier/frp/pkg/msg"
+	"github.com/fatedier/frp/pkg/util/xlog"
+)
+
+func TestHandleTCPWorkConnectionRejectsInvalidAddress(t *testing.T) {
+	workConn, peerConn := net.Pipe()
+	defer peerConn.Close()
+
+	pxy := &BaseProxy{
+		baseCfg: &v1.ProxyBaseConfig{},
+		xl:      xlog.New(),
+	}
+	pxy.HandleTCPWorkConnection(workConn, &msg.StartWorkConn{
+		SrcAddr: "[",
+		SrcPort: 1,
+	}, nil)
+
+	buffer := make([]byte, 1)
+	_, err := peerConn.Read(buffer)
+	require.ErrorIs(t, err, io.EOF)
+}

go.mod

@@ -13,7 +13,7 @@ require (
 	github.com/onsi/ginkgo/v2 v2.23.4
 	github.com/onsi/gomega v1.36.3
 	github.com/pelletier/go-toml/v2 v2.2.0
-	github.com/pires/go-proxyproto v0.7.0
+	github.com/pires/go-proxyproto v0.15.0
 	github.com/prometheus/client_golang v1.19.1
 	github.com/quic-go/quic-go v0.60.0
 	github.com/rodaine/table v1.2.0

go.sum

@@ -78,8 +78,8 @@ github.com/onsi/gomega v1.36.3 h1:hID7cr8t3Wp26+cYnfcjR6HpJ00fdogN6dqZ1t6IylU=
 github.com/onsi/gomega v1.36.3/go.mod h1:8D9+Txp43QWKhM24yyOBEdpkzN8FvJyAwecBgsU4KU0=
 github.com/pelletier/go-toml/v2 v2.2.0 h1:QLgLl2yMN7N+ruc31VynXs1vhMZa7CeHHejIeBAsoHo=
 github.com/pelletier/go-toml/v2 v2.2.0/go.mod h1:1t835xjRzz80PqgE6HHgN2JOsmgYu/h4qDAS4n929Rs=
-github.com/pires/go-proxyproto v0.7.0 h1:IukmRewDQFWC7kfnb66CSomk2q/seBuilHBYFwyq0Hs=
+github.com/pires/go-proxyproto v0.15.0 h1:dTshmNbFm/D+0+sbrxUuddPOZ5Y0B7c5NhtsBkm6LqI=
-github.com/pires/go-proxyproto v0.7.0/go.mod h1:Vz/1JPY/OACxWGQNIRY2BeyDmpoaWmEP40O9LbuiFR4=
+github.com/pires/go-proxyproto v0.15.0/go.mod h1:OXsCrKwrK2tXS9YrI5tkHx5xaQlO8FH3lFW76orFh24=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=