plugin/http_proxy: fix fragmented CONNECT method detection and add read deadline (#5296)

Release.md

@@ -8,9 +8,9 @@ For mixed-version deployments, upgrade frps first, then upgrade frpc. This keeps
 
 This release introduces wire protocol v2 as a transition path for future frpc/frps protocol changes. The existing wire protocol is difficult to extend without compatibility risk, and upcoming changes, including replacing deprecated stream encryption methods, require a versioned protocol.
 
-**The default value of `transport.wireProtocol` remains `v1` in this release, but it will switch to `v2` in the next release.** Users can keep the default for now. To test v2 early, upgrade both frpc and frps to versions that support it, then set `transport.wireProtocol = "v2"` in frpc. A v2-enabled frpc cannot connect to an older frps.
+**The default value of `transport.wireProtocol` remains `v1` in this release.** Users can keep the default for now. To test v2 early, upgrade both frpc and frps to versions that support it, then set `transport.wireProtocol = "v2"` in frpc. A v2-enabled frpc cannot connect to an older frps.
 
-v1 will be deprecated when v2 becomes the default in the next release. It will continue to be supported until v0.78.0 is released, and may be removed in v0.78.0 or later.
+v1 will be deprecated when v2 becomes the default in a future release. It will continue to be supported until v0.78.0 is released, and may be removed in v0.78.0 or later.
 
 ## Features
 

pkg/plugin/client/http_proxy.go

@@ -45,6 +45,8 @@ type HTTPProxy struct {
 	s *http.Server
 }
 
+const httpProxyReadHeaderTimeout = 60 * time.Second
+
 func NewHTTPProxyPlugin(_ PluginContext, options v1.ClientPluginOptions) (Plugin, error) {
 	opts := options.(*v1.HTTPProxyPluginOptions)
 	listener := NewProxyListener()
@@ -56,7 +58,7 @@ func NewHTTPProxyPlugin(_ PluginContext, options v1.ClientPluginOptions) (Plugin
 
 	hp.s = &http.Server{
 		Handler:           hp,
-		ReadHeaderTimeout: 60 * time.Second,
+		ReadHeaderTimeout: httpProxyReadHeaderTimeout,
 	}
 
 	go func() {
@@ -73,16 +75,19 @@ func (hp *HTTPProxy) Handle(_ context.Context, connInfo *ConnectionInfo) {
 	wrapConn := netpkg.WrapReadWriteCloserToConn(connInfo.Conn, connInfo.UnderlyingConn)
 
 	sc, rd := libnet.NewSharedConn(wrapConn)
-	firstBytes := make([]byte, 7)
-	_, err := rd.Read(firstBytes)
+	firstBytes := make([]byte, len(http.MethodConnect))
+	_ = wrapConn.SetReadDeadline(time.Now().Add(httpProxyReadHeaderTimeout))
+	_, err := io.ReadFull(rd, firstBytes)
 	if err != nil {
+		_ = wrapConn.SetReadDeadline(time.Time{})
 		wrapConn.Close()
 		return
 	}
 
-	if strings.ToUpper(string(firstBytes)) == "CONNECT" {
+	if strings.EqualFold(string(firstBytes), http.MethodConnect) {
 		bufRd := bufio.NewReader(sc)
 		request, err := http.ReadRequest(bufRd)
+		_ = wrapConn.SetReadDeadline(time.Time{})
 		if err != nil {
 			wrapConn.Close()
 			return
@@ -91,6 +96,7 @@ func (hp *HTTPProxy) Handle(_ context.Context, connInfo *ConnectionInfo) {
 		return
 	}
 
+	_ = wrapConn.SetReadDeadline(time.Time{})
 	_ = hp.l.PutConn(sc)
 }
 

pkg/plugin/client/http_proxy_test.go

@@ -0,0 +1,107 @@
+// 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 client
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	v1 "github.com/fatedier/frp/pkg/config/v1"
+)
+
+func TestHTTPProxyHandleFragmentedConnectMethod(t *testing.T) {
+	require := require.New(t)
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(err)
+	defer ln.Close()
+
+	const payload = "ping"
+	echoErr := make(chan error, 1)
+	go func() {
+		conn, err := ln.Accept()
+		if err != nil {
+			echoErr <- err
+			return
+		}
+		defer conn.Close()
+
+		buf := make([]byte, len(payload))
+		if _, err = io.ReadFull(conn, buf); err != nil {
+			echoErr <- err
+			return
+		}
+		if string(buf) != payload {
+			echoErr <- fmt.Errorf("unexpected payload %q", string(buf))
+			return
+		}
+		_, err = conn.Write([]byte("echo:" + payload))
+		echoErr <- err
+	}()
+
+	hp := &HTTPProxy{
+		opts: &v1.HTTPProxyPluginOptions{},
+		l:    NewProxyListener(),
+	}
+
+	clientConn, serverConn := net.Pipe()
+	defer clientConn.Close()
+
+	go hp.Handle(context.Background(), &ConnectionInfo{
+		Conn:           serverConn,
+		UnderlyingConn: serverConn,
+	})
+
+	require.NoError(clientConn.SetDeadline(time.Now().Add(5 * time.Second)))
+
+	targetAddr := ln.Addr().String()
+	req := "CONNECT " + targetAddr + " HTTP/1.1\r\nHost: " + targetAddr + "\r\n\r\n"
+	_, err = clientConn.Write([]byte("CON"))
+	require.NoError(err)
+	_, err = clientConn.Write([]byte(req[len("CON"):]))
+	require.NoError(err)
+
+	rd := bufio.NewReader(clientConn)
+	status, err := rd.ReadString('\n')
+	require.NoError(err)
+	require.Equal("HTTP/1.1 200 OK\r\n", status)
+	line, err := rd.ReadString('\n')
+	require.NoError(err)
+	require.Equal("\r\n", line)
+
+	_, err = clientConn.Write([]byte(payload))
+	require.NoError(err)
+
+	got := make([]byte, len("echo:"+payload))
+	_, err = io.ReadFull(rd, got)
+	require.NoError(err)
+	require.Equal("echo:"+payload, string(got))
+
+	select {
+	case err := <-echoErr:
+		require.NoError(err)
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for echo server")
+	}
+}